A111Q3 Qtbbfll

\

V) NBS SPECIAL PUBLICATION 514

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

Product Durability

and Life

MFPG

27th Meeting

WATIONAL BURBAtJ OF STANDARDS

JjIBflARY

MFPG

Product Durability and Life

Proceedings of the 27th Meeting of the

Mechanical Failures Prevention Group,

held at the National Bureau of Standards,

Gaithersburg, Maryland, November 1-3, 1977

Edited by .

T. Robert Shives and William A. Willard

National Measurement Laboratory

National Bureau of Standards

Washington, DC 20234

The 27th meeting of the MFPG and these proceedings were sponsored by the Institute for Materials Research and the Center for Consumer Product Technology of the National Bureau of Standards, Washington, DC 20234; the Office of Naval

Research, Department of the Navy, Arlington, VA 22217; the Naval Air Development Center, Department of the Navy,

Warminster, PA 18974; the National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, MD 20771; and the Department of Energy-Fossil Energy, Washington, DC 20545.

This work was co-sponsored by the Institute for Materials Research prior to the NBS reorganization effective April 9, 1978. The Institute for Materials Research is now included in the National Measurement Laboratory of NBS.

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Annbler, Director

Issued May 1978

*

in Q
Library of Congress Cataloging in Publication Data

Mechanical Failures Prevention Group.

MFPG, product durability and life. (National Bureau of Standards Special publication ; 514) "Sponsored by the Institute for Materials Research . . . [et asl.]." Supt.ofDocs.no.: C13. 10:514

1. Durable goods, Consumer-Reliability—Congresses. 2. Durable

goods. Consumer—Testing—Congresses. I. Shives, T. R. II. Willard, William A. III. Title. IV. Title: Product durability and life. V. Series; United States. National Bureau of Standards. Special publications ; 514. QC100.U57 no. 514 [TS173] 602'.ls [658.5'6] 78-606044

National Bureau of Standards Special Publication 514

Nat. Bur. Stand. (U.S.), Spec. Publ. 514, 188 pages (May 1978) CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1978

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Stock No. 003-003-01935-6 Price $3.75

(Add 25 percent additional for other than U.S. mailing).
FOREWORD

The 27th meeting of the Mechanical Failures Prevention Group was held

November 1-3, 1977, at the National Bureau of Standards in Gaithersburg,

Maryland. The program was organized by the MFPG committee on Mechanisms

of Failure under the Chairmanship of Marshal Peterson of the Office of

Technology Assessment, United States Congress. In addition to the

members of the Mechanisms of Failure Committee, Kenneth C. Ludema of the

University of Michigan, and A. William Ruff and Andrew J. Fowell of the

National Bureau of Standards, made significant contributions in developing the program. All those involved with planning the program, and

especially the speakers, are to be commended for producing an excellent

meeting.

Most of the papers in these proceedings are presented as submitted by

the author on camera ready copy with some minor editorial changes.

Special thanks are due Sara R. Torrence of the NBS Office of Information

Activities for the meeting arrangements.

Appreciation is extended to the following members of the NBS Metallurgy

Division: T. Robert Shives and William A. Willard for their editing,

organization and preparation of the proceedings, Paul M. Fleming for

handling financial matters, Todd Eudy and Leonard C. Smith for photographic work, Marian L. Slusser for typing, and to other members of the

Division whose help contributed to the success of the meeting.

HARRY C. BURNETT

Executive Secretary, MFPG

Metallurgy Division

National Bureau of Standards

III

TABLE OF CONTENTS

Page

FOREWORD III

SESSION I: PRODUCT DURABILITY ISSUES

1

.

Opportunities and Implications of Extending Product

Life. Robert T. Lund and William Michael Denney*

3

2. Economic Considerations and Product Life, Paul .Lerman 12

3. Technical Durability of Products. Elio Passaglia

(abstract only, see Appendix A)

4. Labeling Products for Durability. Mark J. Raabe 19

SESSION II: PRODUCT TESTING

1

.

Methodology of Product Life Testing. Julius Cohen 31

2. Small Appliance Life Testing. Kenneth W. Yee 42

3. Product Life Testing and Durability. N. R. Pugh 54

4. Hydraulic Pump Contaminant Life Evaluation. L. E. Bensch 66

5. Control of Design Quality. Andrew W. Dorney 76

6. Factors Affecting Product Lifetime: Preliminary Results

of a Research Study. W. David Conn,* Carol Inge,

Biswapriya Sanyal , and Elaine Warren

82

SESSION III: DURABILITY TECHNOLOGY IN INDUSTRY

1 . Brake Wear. S. K. Rhee 93

2. Accelerated Testing of Compressors. Frank E. Kalivoda 99

3. Automobile Durability. C. J. Brady and H. W. Larsen* 107

4. Wear Analysis in Office Machines. P. A, Engel 121

V
SESSION IV: PRODUCT PERFORMANCE -- WHY CARE?

1. Materials Conservation through Increased Durability,

M. B. Peterson (abstract only, see Appendix A)

2. Extended Life and Waste Reduction. F. Smith (no

manuscript or abstract submitted)

3. Household Retention of Consumer Appliances: USDA 131

Actuarial Estimates. Marilyn Doss Ruffin* and

Katherine S. Tippett

4. Application of Historical Repair Data in Life Cycle 139

Costing Analysis. S. Wayne Stiefel* and

Wil 1 iam B. Beine

5. The Concepts of Product Life and Consumer Product Safety.

Joann H. Langston (abstract only, see Appendix A)

6. Environmental and Economic Impacts of Product Durability 156

and Life. P. L. Fontaine \

SESSION V: PANEL DISCUSSION: CAN AND SHOULD PRODUCT LIFE BE

EXTENDED?

Introductory Remarks of Panelists:

1 . William E. Davis 165

2. W. A. Glaeser 169

3. N. R. Pugh 171

APPENDIX A

Abstracts of Papers for which no Manuscripts were Submitted:

1. Technical Durability of Products. Elio Passaglia 175

2. Materials Conservation through Increased Durability. 176

M. B. Peterson

3. The Concepts of Product Life and Consumer Product Safety. 177

Joann H. Langston

VI
APPENDIX B

List of Registrants for the 27th MFPG Meeting

MFPG Publications

181

186

* Indicates speaker when a paper had more than one author.

VII
ABSTRACT

These proceedings consist of a group of nineteen submitted papers

from the 27th meeting of the Mechanical Failures Prevention Group which

was held at the National Bureau of Standards in Gaithersburg, Maryland,

on November 1-3, 1977. The central theme of the proceedings pertains

to the durability of consumer products. Special emphasis is on durability technology, product testing, product performance, the economics of

extending product life, and labeling products for durability.

Key words : Design quality; durability; durability technology; materials

conservation; product life; product performance; product testing; wear

analysis

UNITS AND SYMBOLS

Customary United States units and symbols appear in many of the

papers in these proceedings. The participants in the 27th meeting of

the Mechanical Failures Prevention Group have used the established units

and symbols commonly employed in their professional fields. However,

as an aid ,to the reader in increasing familiarity with and usage of the

metric system of units (SI), the following references are given:

NBS Special Publication, SP330, 1977 Edition, "The International System

of Units."

ISO International Standard 1000 (1973 Edition), "SI Units and Recommendations for Use of Their Multiples."

E380-76 ASTM/IEEE Standard Metric Practice (Institute of Electrical and

Electronics Engineers, Inc. Standard 268-1976).

Disclaimer:

Certain trade names and company products are identified in order to

adequately specify the experimental procedure. In no case does such

identification imply recommendation or endorsement by the National

Bureau of Standards, nor does it imply that the products are necessarily the best available for the purpose.

VIII
SESSION I

PRODUCT DURABILITY ISSUES

CHAIRMAN: K. C. LUDEMA

UNIVERSITY OF MICHIGAN

OPPORTUNITIES AND IMPLICATIONS OF EXTENDING PRODUCT LIFE

Robert T. Lund

Center for Policy Alternatives

Massachusetts Institute of Technology

Cambridge, Massachusetts 02139

Wm. Michael Penney

Center for Policy Alternatives

Massachusetts Institute of Technology

Cambridge, Massachusetts 02139

Abstract: This paper begins by discussing the various benefits associated with extended product life, and possible negative impacts are

noted, as well. It is pointed out that the factors influencing product

life are not only technological in nature, but also include product

usage behavior by consumers. The discussion then turns to a fourfold

classification scheme for policy alternatives for extending product

life. This scheme is built on the distinction between consumer versus product-related influences on product life, and a distinction between

short-term and long-term policy impacts. The final section of the paper

identifies options available to policymakers attempting to prolong

product life. The concept of remanufacturing , as a strategy deserving

more careful attention, is particularly stressed.

Key words: Product life; remanufacturing ; consumer usage; product

durability; product design; resource conservation.

How often have we heard the lament: "Why can't they make a product that

lasts?" To the average consumer, the desire for longer lasting products

probably seems beyond debate. This is corroborated by the recent Sentry

Insurance study. Consumerism at the Crossroads , which found that 78

percent of the public believes that products do not last as long now as in the past [1]. Whether this is objectively true is open to question

[2,3] but the shape of consumer sentiments is clearly in the negative.

Beyond the desire to satisfy public sentiment, however, there are persuasive arguments in favor of making products live longer.

There is, first of all, the prospect for direct savings to consumers

that could accrue from less often having to replace products in which

they have a major investment. Moreover, to the extent that increased

product life also means greater reliability and fewer repairs, we might

3
expect consumers to become more satisfied with the performance of their

purchases

.

In addition to benefits for the individual consumer, extending product

life also promises to benefit society as a whole. There is an increasingly recognized need for a shift in societal values toward resource conservation as dictated by encroaching scarcities (or the economic

measure, rising costs). Thus, a primary societal incentive for extending product life involves the opportunity to save material and energy resources that go into the manufacture of consumer goods. It can also

be expected that longer product life will help alleviate the waste disposal burden that has become one of the nastier by-products of this age

of technological prosperity.

As with most issues, however, the question of product life is not all

one-sided. There are potential problems and limitations in what can be

achieved. It is possible, for example, that increased life for certain

products can be purchased only through significantly increased costs of

production. This would be the case when more costly materials are used,

or when more expensive fabrication or assembly techniques are required.

If longer lasting products are also more expensive, the direct savings

to consumers may not be possible. Because most of us have some intuitive "discount rate" built into our evaluation of future savings arising

from present costs, the extension of life of a product, such as an appliance that already has an average life of fifteen years, may have

a rather low value at the time of purchase.

A second and related problem involves reliance on scarce or precious

materials to achieve greater product durability. Not only might the

cost of certain products be increased through increased use of stainless

steels and brass, for example, but it would also be counterproductive

to promote product life when it might only serve to place heavier

demands on copper, chromium, nickel and zinc —more valuable and increasingly scarce materials.

A third problem raised by the prospect of longer product life is its

potential effect on product innovation. If products last longer, the

turnover rate for the total product stock will fall; this in turn may

inhibit the rate at which new product designs and related innovations

can be introduced into the existing stock. In an era when we find ourselves promoting and encouraging consumers to switch to more energy*

efficient cars and appliances, more pollution-free automobiles, safer

products, and so forth, it can be argued in some instances that we

should not attempt to perpetuate existing product designs.

A final argument stems from the potential economic dislocations that

might result from extending the life of products. If longer product

life leads to a reduction in consumer demand, this would imply a slowdown in economic growth for the affected industry. Unemployment and

profit losses could result. Generally, however, such negative impacts
can be regarded as temporary, since the long-term effects of consumer

savings in one product category should be a redistribution of expenditures to other kinds of goods and services. During the transition,

however, the consequence for production workers, suppliers and retail

dealers can be painful.

Longer product life, then, as with many aspects of product design,

manufacture and use, is a situation involving important trade-offs.

The reason why product life has become an important topic today is

that the values that go into the trade-off equilibria have been

shifting—some very rapidly. We now need to see if there are ways of

achieving new balances that provide longer life at an acceptable cost.

Factors Determining Product Life

When most people talk about increasing product life, they usually focus

on technological solutions to product durability. (The program for

this conference reflects this prevailing concern.) Naturally, how long

a product lasts is heavily dependent upon its design, the materials

used in its construction, and the processes by which it is manufactured

and tested for quality. In addition, however, product life is also

dependent upon consumer attitudes and usage behavior. [4] Products all wear out —eventually. But they will wear out more quickly when they

are used more heavily or when they are abused. The care and maintenance given a product will influence its durability. And finally, of

course, the very decision that a product is no longer "worth keeping"

is ultimately a subjective and only partly economic judgement by the

consumer, rather than one based on purely technological considerations.

Opportunities for extending product life are not merely questions of

design and manufacturing technology. A great deal depends on consumer

attitudes and perceptions as these influence product usage behavior.

Not only are there these two major sources of influence on product life,

but an additional level of complexity arises out of the interplay

between product design and consumer psychology. Perhaps the most widely

recognized example of that interplay involves stylistic changes in product design. This is the familiar phenomenon of new products being

bought to keep up with new styles and appearances, in disregard of functional qualities. Critics of industry frequently argue that superficial

style changes, without significant change in underlying design, are exploited as a marketing device to the detriment of the consumer. The

counter-argument is that consumers want "style," and business is only

meeting the legitimate needs of consumers to pursue their aesthetic

tastes whether these needs are rational or not in some more objective

sense. Furthermore, new models often contain a mix of functional improvements and styling changes. [5]

5
Policy Alternatives for Extending Product Life

The achievement of longer product life is a desirable objective, provided that the means of accomplishing the objective do not generate un- acceptable side effects. Society, we believe, is willing to opt for

products that live longer if the consequences of this course of action

are reasonably benign. There are, then, two principal issues confronting policy formulation in this area: (1) to identify specific product

categories for which longer life is a desirable goal; and (2) to identify appropriate strategies for accomplishing the objective of extended

life with minimal adverse effects.

While definitive answers to these issues are not yet readily available,

a useful starting point would be to specify the criteria that are most

relevant for assessing the policy alternatives that may be considered.

In identifying product targets , at least the following four criteria

should be taken into account: (1) value-added during manufacture; (2)

materials and net energy involved in production; (3) effects of the

product on the environment; and (4) actual potential for increased life.

First, the prime candidates for extended life policy should be products

with a comparatively high level of value-added, since these offer the

greatest opportunity for conservation of labor, energy, and materials

invested in products. In this sense, extending product life complements

recycling as a conservation strategy. Secondly, while the value-added

criterion covers both material and energy overhead costs, these also

deserve separate consideration. At present, the full social costs of

many materials are not internalized in production costs; the same may be

said for energy resources to perhaps an even greater degree. Therefore,

the relative scarcity of and potential substitutes for these resources

should be a direct policy concern independent of their cost contribution

to production overhead.

The same may be said for those products which, when discarded, produce

undesirable social consequences - litter, pollution, waste handling

costs. These social costs have not even been adequately accounted for,

and certainly have not been made internal to the products.

The fourth major consideration in identifying target products is the

pragmatic one of whether there is actually a significant life-extension

opportunity. It is senseless to devote time and effort to promoting

product life in cases where only marginal improvements are possible.

Turning to the question of what policy strategies will generate the

greatest benefits with the fewest adverse effects, we encounter somewhat

greater problems for systematic treatment. Earlier, we cited a number

of the most critical negative impacts that could result from illconceived efforts at extending product life. Any policy program should

certainly strive for prior assessments of both the intended and unintended

consequences of alternative strategies. Before this can be done,

however, it is necessary to have some basis for determining what the

possible policy strategies themselves may be.

6
As a first step toward delineating the policy alternatives for extending

product life, we propose a fourfold classification scheme. We are led

to this scheme, first, by the previous observation that product life

depends both upon factors of consumer psychology as well as properties

of the product itself. More generally, consumers make up the demand

side of the marketplace. In the complete array of product life policies,

the consumer-related policies may very well be as important as the

technologically-oriented policies of the supply side.

From a policy standpoint, moreover, it is important to recognize the

difference between short- and long-term processes of change. Shortterm policy strategies in the case of durable products would pertain

primarily to the existing stock of products, while long-term strategies

would apply to products not yet offered for sale to consumers. The

total problem/policy environment can thus be usefully depicted according to the following fourfold matrix:

MARKET BEHAVIOR SUPPLIER BEHAVIOR

SHORT-TERM IMPACTS Consumer usage Existing product

behavior maintenance & disposal technology

LONG-TERM IMPACTS Consumer purchase New product

behavior performance-design

and manufacture

Within each of the four cells of this scheme, we have specified what

appear to be the primary controlling factors on product life. These,

in effect, comprise the leverage points available to policy intervention.

If one wishes to promote longer product life, the resources of policy

intervention (e.g., tax incentives or penalties, product material and

performance standards, consumer information and persuasive appeals)

should be directed to affect one or more of these controlling factors.

In the short-term, market quadrant, efforts to promote longer product

life must focus on the way consumers use the products they currently

own and/or on the service and disposal mechanisms that are currently

available. Examples of strategies that could be employed to influence

consumer usage behavior are: (1) education to help consumers appreciate

the value of improved product care and information to indicate the most

efficacious ways of increasing the useful life of products already owned;

and (2) tax incentives for expenditures on repairs and basic maintenance

that enhances product longevity — analogous to the tax deductions

allowable now for medical expenses.

On the supply side, short-term policy options could include: (1) incentives to suppliers to encourage them to keep up parts inventories.

7
both to assure the availability of replacement parts and to help hold

dovm the cost of such parts for product repair; (2) encouragement and

perhaps direct public support for used product markets, both for direct

re-use (second-hand) by consumers and for purposes of total or part

remanuf acturing; and (3) lower servicing costs.

In the long-term, strategies to promote longer product life must focus more on making changes in the composition of the total product stock.

Initiatives directed at market behavior should concentrate on inducing

the purchase of models with the potential for a longer technicallyuseful life. While consumers may be concerned about product durability,

they often lack the information to evaluate their purchase alternatives

in this light. This implies some form of consumer education or information that assists consumers in their product selections. Having

purchased more durable products, consumers must be encouraged to keep

them to the end of their useful lives or to get them into second-hand

markets or collection points for remanufacturing

.

In the long-term, where we are considering new products replacing

existing products in use, suppliers have a major role in increasing

product life through product design. Not only can the functional

durability of the product be enhanced, but its cosmetic durability

(resistance to degradation of appearance) should also be considered.

Repairability — low cost replacement of either functional or cosmetic

parts — is an alternative to designs for very long-term durability.

This approach obviously depends on the supplier's willingness to maintain stocks of replacement parts over the life of the product. Finally

the product can be designed for ease of disassembly and remanufacture

.

This latter alternative has been given very little attention by either

the public or private sector, and needs further consideration.

Remanufacturing — A Neglected Alternative

Even when a complex durable product such as an automobile, an appliance

or a machine has come to the end of its useful life, there is much in

that product that retains its full functional value if the components

could be put to use again. The brushes in electric motors may wear out

but the armatures and their windings are good; bearings may fail, but

the castings in which they are set are still sound. Each of these

functionally useable parts have a value (as represented by the materials,

labor, energy, and overhead costs associated with its manufacture) that

is many times the residual material value as scrap. Remanufacturing is an approach that finds intermediate methods of preserving the functional value of the original product — essentially giving older products

new lives.

We would like to suggest that remanufacturing is an especially promising strategy for achieving a fully extended product life. We are not

speaking here of unit-by-unit rebuilding of products, which would be

too small in scale to have significant economic impact. Rather, we

8
refer to the highly organized business of total disassembly of products,

pooling of interchangeable parts, and production-line reassembly with

some replacement of worn parts. It is a strategy aimed at capturing

the residual functional value (or value-added) in a used product that

might otherwise be destined for disposal, by reprocessing all usable

parts to arrive at a like-new product or functional value nearly equal

to the original.

Remanuf acturing promises an unusually strong array of advantages com- pared to alternative methods of extending product life. Unlike strategies aimed simply at increasing the life of the original product

(e.g., increased durability), remanufacturing helps deal with the fact

that all products do eventually wear out. While repairs can keep a product in operation for an extended period, there arrives a time when

repair costs become prohibitive and the unit is discarded. When this

happens, the residual value of the product (or of its salvageable parts)

is entirely lost. Recycling, to recover the materials content of products is, if collection costs are included, a far less attractive

alternative. Through remanufacturing , by contrast, one has the opportunity to preserve a much larger share of the product's functional

value over an extended period.

Remanufacturing involves a number of process steps that are relatively

labor intensive. The bulk of the work is in parts refinishing, testing and assembly, where people are needed. Remanufacturing , therefore,

implies employment opportunity, especially at unskilled and semi-skilled

levels. It can provide a stimulus to new jobs not only in the remanuf acturing operations, but also in the development of collection and

distribution networks needed to sustain such an industry.

This stimulus to employment need not be merely a trade-off for jobs

lost through a reduction in work in original equipment manufacturing

plants. Remanufacturing will provide lower cost, like-new products in

the market. These will undoubtedly compete with some portion of the new product market, but there is a high probability that the lower

prices on the remanufactured models will expand the market among lower

income consumers and to higher income consumers wishing to add to their

household stock (a second refrigerator, for instance).

Remanufacturing is also an attractive way of providing lower-cost

replacement assemblies to repair products still in use. This is about

the only contribution remanufacturing makes today. There is an active

remanufacturing industry for major automobile parts, such as alternators, starter motors and water pumps. These lower-cost replacement

parts directly contribute to prolonging the lives of automobiles which

might otherwise be abandoned.

While remanufacturing offers attractive opportunities for extending product life, a number of issues need to be better understood before this

approach can be successfully implemented. Among the major problems to

be resolved is the need to establish efficient channels for both

9
collecting worn-out products and, at the other end of the line, for

distributing and retailing the reprocessed products. Not only must

these commercial operations be established, but the whole proposition

must gain consumer acceptance. Consumers must cooperate in getting

their used goods into the remanuf acturing system (some incentive may

be needed) , and then some segment of the consuming public must be ready

to buy remanufactured products. Price savings should provide a strong

inducement, but there may still be some degree of attitudinal resistance to be overcome.

Another set of issues pertains to the fit between product designs and

the remanuf acturing process. It would clearly be helpful if emphasis were given to new product designs that allow for easy disassembly of

component parts and reassembly once cleaning and refurbishing have been

done. Similarly, it would facilitate the remanufacturing process if

there were greater standardization of product components across brand

and model categories. While such standardization should not be sought

at the expense of product innovation, there surely can be greater com- patibility of component designs particularly in products with a relatively stable technology.

A final set of issues centers on the process technology of remanufac- turing per se. Since this is not yet a large industry, little experience is available as to the most practical and efficient methods of

operation. There are questions about the optimal scale for such operations, the degree of centralization possible (given constraints imposed

by collection and distribution channels) , and the most promising

approaches for starting up such an operation. For that matter, it is

not yet clear what product categories are the prime targets for remanuf acturing, although the criteria described earlier can help guide such

choices

.

What we are suggesting here is that remanufacturing holds great promise

as both a strategy for extending product life, and as a potentially

lucrative business venture in its own right. However, much needs to

be learned before substantial investments are warranted. A closer look

will undoubtedly reveal technical, economic and social problems that

must be dealt with. This is an important area for research, and we are preparing to explore it further.

Conclusion

We began this paper by noting that the opportunities for extending

product life carry both positive and negative potentials. It is not a one-sided propostion, and great care must be taken in determining the

most effective life-extending strategies with the fewest undesirable

consequences. Well-reasoned policies to promote longer product life

must begin by assessing the alternative strategies that are actually

available

.

10
As a step in this direction, we have stressed the point that product

life is affected not only by inherent characteristics and durability

of the product itself, but also by the way consumers use the product.

Technological solutions can be ineffectual if consumers refuse to

cooperate. More than this, it must be recognized that products and

people interact, and that efforts to prolong product life must take

the human factor into account.

As with any complex problem, the challenge of extending product life

has many different facets. There are differences between short-term

and long-term policies — i.e., whether you are trying to extend the

life of products already on the market versus trying to reshape the

nature of the total stock of products over time. There are also

crucial differences in whether one wishes to concentrate on making

the original product live longer or on trying to establish some intermediate mechanism, such as remanufacturing , that fulfills essentially

the same function of preserving the functional value of products or product parts.

The point is not that any one approach is better than others, but

rather that such judgements must begin by discerning what actually are

the alternatives before us. The optimal solution is very likely to

involve a mix of strategic alternatives—technological change, market

and consumer behavior change, and perhaps even the emergence of whole

new industries.

References

1. Consumerism at the Crossroads , Sentry Insurance, report prepared

by Louis Harris and Associates, Inc. and Marketing Science

Institute, 1977, page 23.

2. Lund, R. T. , "Incentives for Longer Product Life: A Case Study,"

paper presented to O.K. CD., Paris, April 1976.

3. Ruff in, Marilyn Doss and Katherine S. Tippett, "Service-Life

Expentancy of Household Appliances: New Estimates From the USDA,"

Home Economics Research Journal , Vol. 3, March 2975, pp. 159-170.

4. Smith, Frank A. , Product Design Modifications for Resource Recovery , Source Reduction, or Solid Waste Management Purposes , Section

entitled "Economic Durability of Products," Mimeo, May 1973 (largely

reproduced as Appendix B of Second Report to Congress , Resource

Recovery and Source Reduction, U. S. Environmental Protection Agency,

1974)

.

5. White, Lawrence J., The Automobile Industry Since 1945 , Chapter 12,

"Product Behavior: Durability, Styling Models and Model Proliferation," pp. 189-210, Howard University Press, Cambridge, 1971, 348 pp.

11
ECONOMIC CONSIDERATIONS AND PRODUCT LIFE

Paul Lerman

Fairleigh Dickinson University

Rutherford, New Jersey 07070

Abstract: The economic and financial considerations

associated with all product decisions has become

increasingly important in recent years due, in large part,

to relatively high capital costs and the resulting desire

on the part of corporate decision makers to invest their

capital funds in those projects yielding acceptable

returns

.

Most cases involving an improvement in product

durability will require a commitment of managerial,

engineering, and production resources, all of which will

ultimately be measured in financial terms. Thus, the final

decision regarding product durability would seem to be

based on economic and financial considerations, assuming

technological feasability.

This paper discusses the economic and financial

considerations that must be recognized in determining the

viability of an improvement in product durability. Included

in this discussion are current accounting and tax policies

that affect the decision.

Key words: Discounted cash flow; financial analysis;

product durability; product life; tax effects.

INTRODUCTION

It has become increasingly clear in recent years that

all corporate decisions have, and continue to, come under

increasing scrutiny by the financial decision makers. The

ultimate decision is based at least as much on financial

considerations as on technological considerations since,

in most cases, they are inseparable. Thus, in order to

make a rational decision as to the desirability of

increased product durability or prolonged product life,

it is necessary to consider the financial institutions

12
that affect the decision.

GENERAL CONSIDERATIONS

The decision to improve product durability would be

simple to arrive at if it were possible to accomplish the

improvement at no additional cost to either producer or

consumer. However it would be unrealistic to expect that

product cost would not increase with such an improvement

in product durability. From the standpoint of the producer

it could be expected that his production cost, including

research and development and other capital investment, would

increase. This might result in a change in sales revenue

which could be negative (due to reduced volume caused by

increased price) or positive (due to wide acceptance of

the improved product at the higher price)

.

Thus, in consideration of changes in revenue and

costs, the producer's decision rests on whether future

sales will provide a sufficient incremental benefit to

justify increased investment. The consumer would also

be concerned with the tradeoff of higher initial cost

against the future incremental benefits purchased by the

increased initial expenditure. Both producer and consumer

would presumably utilize the so called "discounted cash

flow" analysis to determine the worthiness of the

additional expenditure. The basic equation used for the

analysis is:

Cl C2

NPV = Cq + + ^ + . . . +

(1 + i) (1 + i)^ (1 + i)""

where

NPV = net present value ($)

C. = cash flow ($) j = 1,2, ...,n

1"*= discount rate.

If we assume, for example, that Cq is negative representing the incremental initial outlay, and each C . is

positive, representing the incremental benefit due ti

improved product durability, the calculation of NPV would

provide an indication of the desirability of the additional

investment.

An investigation of the denominator of each term in

the net present value equation provides some insight into

15
the nature of the analysis. It can be seen from the NPV

equation that as the benefit to be received is further in

the future, the contribution to NPV per dollar of benefit

decreases due to the increasing nature of the denominator.

Alternately stated, one dollar of additional expenditure at

the outset requires more than one dollar of benefit at a future time period in order to make the original investment

worthwhile. Just how much larger depends upon the timing

of the benefit and the discount rate. The effect of time as well as the effect of the discount rate may be seen in

Table 1.

The table reveals that as the time of the receipt of

the benefit is pushed into the future, the discounted value

of the benefit decreases. Additionally, the table shows

that as the discount rate is increased, holding the benefit

receipt period constant, the discounted value of the

benefit decreases. For industrial decisions, the discount

rate usually represents the minimum acceptable rate of

return on corporate investments. It is usually determined

by considering such factors as the cost of capital, project

risk, expectations regarding inflation, etc. In many

corporations this rate is varied, depending on the risk

nature of the specific investment under consideration. It

is significant to note that, currently, it is quite commonplace for the discount rate to be in excess of twenty percent, with it not being uncommon for some corporations to

use a discount rate of thirty percent for at least some of

its investments.

These rates have very serious ramifications from the

viewpoint of at least one aspect of product durability,

that is, extended product life. For, if the increase in

product life has resulted in a one year extension of that

life, say from nine years to ten years, it can be seen from

Table 1 that each one dollar benefit in year ten, assuming

a twenty percent discount rate, has a net present value of

$0.1515. Alternately stated, this one year extension of

product life can be justified only if each additional dollar

of benefit cost no more than $0.1515 at inception. Of

course, if the discount rate is increased to thirty percent,

each additional dollar of benefit received in year ten can

be justified by an additional expenditure of no more than

$0.0725 at inception.

Ik
TABLE 1

PRESENT VALUE OF ONE DOLLAR

1

YEAR OF DISCOUNT RATE

RECEIPT 5% 10% 20% 30%

1 0,.95238 0..90909 0,.83333 0,.76923

2 0..90703 0..82645 0,.69444 0,. 59172

3 0..86384 0..75131 0,.57870 0..45517

4 0..82270 0..68301 0,.48225 0..35013

5 0..78353 0..62092 0,.40188 0.. 26933

10 0..61391 0..38554 0,.16151 0..07254

15 0..48102 0.. 23939 0,.06491 0..01954

IDENTIFICATION OF COSTS AND BENEFITS

In order to apply the discounted cash flow method, it

is necessary to quantify the costs and benefits (net cash

flows) associated with a decision to alter product durability. From the viewpoint of the producer, an improvement in product durability can be expected to require

additional outlays in research and development, machinery,

etc. As discussed earlier, given no external disturbance

such as increased government intervention, a rational

producer would undertake such an investment only if the

future sales are expected to result in a sufficiently high

cash flow stream. The actual cash flows are significantly

affected by taxation policies, a subject discussed in some

detail below.

Likewise, the consumer would be required to expend

an incremental amount of money at the time of the purchase

on the improved product. His expectation of the future

benefits to be received for this additional outlay would

include such things as reduced maintenance and/or increased

product life. Of course there are other less tangible

benefits that enter into consumer decisions. In any event

it should be noted that consumers (other than industrial)

discount future benefits quite heavily (ref. 1) and thus

the initial price usually plays more of a role in his

decision than for the industrial consumer.

ACCOUNTING AND TAX EFFECTS

A simple definition of the term "net cash flow" may

be stated as the incremental amount of money that an

15
investor finds in (or out) of his pocket for having made

the investment under consideration. For industrial producers and industrial consumers, the actual determination

of net cash flow depends very heavily on the accounting

and tax treatment of the original expenditure and the

future benefits

.

The two major categories of increased initial outlay

have previously been identified as research and development and, equipment (fixed assets). Current tax law

(1977) permits research and development to be deducted

from income in the year paid or incurred, or over a period

of 60 months or more. Any additional or new equipment

must be capitalized and depreciated over the expected

useful life of the equipment. There are several methods

permitted to be used in the calculation of annual depreciation charges. Table 2 provides an example of the

charges as calculated by the three most commonly utilized methods. All are accepted by the Internal Revenue

Service for income tax purposes. The table shows that

all three methods result in the same total depreciation

over the life of the investment. The differences between

the three methods can be found in the timing of the

depreciation charges. The accelerated methods, double

rate declining balance and sum of the years digits, provide

larger expenses in early years and smaller expenses in

later years when compared to straight line depreciation.

Depreciation charges themselves are non-cash charges

however, since depreciation is an allowable expense in

the computation of income taxes, it can be seen that the

accelerated methods while resulting in larger charges in

early years have the effect of reducing income taxes in

those years while increasing them in later years. Even

though the total amount of taxes paid over the life of

the investment will be the same regardless of which method

is used for the computation of depreciation, the discounted

cash flow equation reveals that it is desirable to defer

tax payments to later years since deferal of taxes results

in larger cash flows in early years when the present value

factors are the greatest.

One additional feature of the current tax law important to machinery investment decisions is the investment

tax credit. The investment credit was originally intended

as a device for stimulating increased business investment

16
in machinery and equipment. The Tax Reduction Act of 1975

raised the credit from 7% in effect since 1962 to 10%.

A tax credit differs from a deduction in that it is applied

dollar for dollar against the actual tax bill, whereas a deduction, such as depreciation, results in a tax saving

of $0.48 for each dollar of deduction. (The current tax

law places all corporations earning over $50,000 in

a 48% tax bracket.) The investment tax credit, for

equipment having a life in excess of seven years is 10%

with reductions for equipment having useful life of

between three and seven years. There is no credit for

equipment having a useful life of less than three years.

Therefore, for the example of Table 2, the purchase would

result in an actual tax saving of $1600.00 thereby effectively reducing the initial outlay for the equipment to

$14,400. The tax credit has no effect on regular depreciation . Thus it can be seen that if a corporation chooses an

accelerated depreciation method, coupled with the investment

tax credit, the major portion of the tax benefits are

taken in early years.

TABLE 2

COMPARISON OF DEPRECIATION METHODS

EXAMPLE: Asset Original Cost

Estimated Salvage

Estimated life

$16000.00

1000.00

10 years

YEAR STRAIGHT

LINE

DOUBLE RATE

DECLINING BALANCE

SUM OF THE

YEARS DIGITS

1

2

3

4

5

6

7

8

9

10

$1500.00

1500.00

1500.00

1500.00

1500.00

1500.00

1500.00

1500.00

1500.00

1500.00

$3200.00

2560.00

2048.00

1638.40

1310.72

1048.58

838.86

785.15

785.15

785.15

$2727. 27

2454.55

2181.82

1909.09

1636.36

1363.64

1090.91

818.18

545.45

272.73

$ 15000.00 $ 15000.00 $ 15000.00

NOTE: For double rate declining balance, the deprec17
iation rate is twice the reciprocal of the asset's

expected life, with no explicit recognition of

end of life salvage. The practice is to switch to

straight-line depreciation in the year that the

declining balance charge falls below the average

depreciable amount.

EFFECT ON DURABILITY DECISIONS

The previous discussions all seem to point in the

same direction. Financial management seems to be oriented

toward early return of the benefits associated with any

given investment. The tax laws appear to be written to

provide this early return through the investment tax

credit and accelerated depreciation provisions. These

observations should provide some insight into which

durability improvements can be made viable. If the

only effect of improved durability is to increase product

life for a product having a relatively long product life,

say ten years, it could be justified only by a small

additional outlay requirement. However, if the improvement provides reduced maintenance costs throughout the

life of the product, it may be possible to justify a relatively larger initial outlay

REFERENCES

(1) Flanagan, W.F. and R.T. Lund. "Factors Controlling

Longer Product Life: The Case for Consumer Durables"

Proceedings of a Workshop on Wear Control to Achieve

Product Durability. Analytical Rework/Service Life

Project Office, Naval Air Development Center, Warminster, Pa.

18
LABELING PRODUCTS FOR DURABILITY

Mark J. Raabe

House Ccranittee on Interstate and Foreign Comierce

2125 Raybum House Office Building

Washington, D. C. 20515

Abstract: Review of Congressional Action with respect to past consideration and current bills dealing with labeling products for durability,

as well as for other characteristics. Discussion of present governmental action in the overall product labeling area, including comrients

on primary problems being encountered. A focus specifically on durability labeling along with comnents on prospects for future congressional action.

I am pleased to be here this afternoon to discuss labeling of products

for durability. I plan to first review Congressional action in this

area with respect to both past consideration and current bills before

the House and the Senate.

Next, I shall discuss vdiat government agencies are doing — and potentially can do — in this overall area, in the absence of further Congressional action. This will include ccmment on some of the problems

that are currently being encountered.

And finally, I shall focus on durability, and the prospects for Congressional action in that area — as I see it frcm my vantage point.

Congressional action — So far in the 95th Congress, which began in

January of this year, there have been two basic bills introduced on

subject matter relating to durability.

(1) Congressman Ben Rosenthal of New York is the prime sponsor of the

first bill I shall discuss. This bill would require that durable

consumer products be labeled as to durability and performance life. If

enacted, it would be known as the "Performance Life Disclosure Act."

Through successive introductions of this bill, there are now 33 co- sponsors of the legislation.

In format, this is a relatively unccxrplicated, straight-foi^mrd and

simple bill. That is not to suggest, however, that carrying out the

legislative mandate of the bill would be easy or not fraught with difficult and coiplex problem areas.

Under this bill, the National Bureau of Standards (NBS) would be called

upon to establish regulations requiring manufacturers of durable

19
consumer products, including appliances and electronic itens, to disclose on a conspicuous label or tag affixed to each item sold at retail

to consuirers, the product life of each manufactured durable product as used urider normal operating conditions.

Under this bill, the NBS would have final authority over the selection

of products and conponents of those products for which performancelife designations would be made, as well as over the procedures for

determining and establishing performance life of those products. The

bill is silent on the manner in which the NBS is to carry out its responsibilities. As I indicated earlier, this is a rather abbreviated

bill — consisting of only two pages in length — which leaves many

problems of irtplementation unanswered.

The Federal Trade Ccanmission (FTC) would be authorized, under this

bill, to enforce the Act with the same jurisdiction, paver and duties

as are contained in the FTC Act. (Cdtnent on FTC jurisdiction.)

(2) The second and more corprehensive bill introduced in the current

session is H.R. 24. This bill would establish uniform test protocols

for consumer products and mandate labeling them. The bill was introduced by Congressman John Murphy of New York and, if passed, would be

known as the "Consumer Product Testing Act of 1977 .

H.R. 24 closely parallels a bill knovn as the "Consumer Product Testing

Act of 1975," co-sponsored in the last session by Senators Magnuson and

Moss in the Senate and Congressmen Moss, Dingell and Van Deerlin in the

House. While the two bills I have mentioned have been introduced in

the House, no legislation bearing upon durability has been introduced

in the Senate during this session. However, while hearings have not

been held in the House, they have been held in the Senate during the

past session. I will say more about this later. First, I will coinnent

briefly on the provisions of H.R. 24.

The bill would require the FTC, in conjunction with the NBS, to prcimilgate uniform product test protocols v\^ch would provide a basis for

judging and carparing "product characteristics". Product characteristics include, but are not limited to (1) effectuation of purpose, (2)

durability, (3) average annual cost of repair, (4) maintenance requirements, (5) frequency and nature of repair, and (6) environmental innpact

in the manufacture, use and disposal of the product.

Section 4 of the bill directs the Ccsnmission to initiate proceedings

for the development of test protocols when it determines that the protocols would mterially assist consumers in purchasing decisions. Section 5 details the procedure for the development of test protocols.

The COTtnission, in conjunction with the NBS, would have the responsibility of initially identifying product characteristics capable of objective measureirent. Thereafter, interested persons would be invited to

develop test protocols. A proposed protocol wDuld be published in the

20
Federal Register as a proposed rale. Protocols would be promulgated

pursuant to the informal rulemaking provisions of section 553 of the

APA. (Cf. procedures of sec. 553 with those of Magnuson-Moss Act.)

Section 6 of the bill would authorize the FTC to promulgate regulations governing the manner in which manufacturers, distributors, and

retailers may advertise that their products have been tested in accordance with a test protocol. Results of such testing would be required

to be disseminated to consumers at the point of sale prior to sale.

Section 8 provides that the Ccfftmission may conduct compliance testing

to insure the veracity of test results. Sections 9, 10 and 11, respectively, provide for injunctive relief to injured parties, set forth

prohibited acts and provide for civil and criminal penalties.

During the Senate hearings on S. 643 (counterpart of H.R. 24) in the

last session of Congress, strong opposition to the bill was heard fron

both government and industry groiips. It might be of interest to you

just to note briefly the positions of the principal parties who testified. I should caution, however, that viewpoints can and do change

with the passage of time. This would be particularly possible vAiere a

change in administrations has taken place such as we have undergone

since the 94th Congress.

The Federal Trade CciTmission , through then Chairman Engman, expressed

unanimous support for the basic concepts of the bill. The Cannission

felt the bill would help correct problems both of deficiency and noncorparability of product information. In addition, the Ccmnission

took the position that labeling as to quality and performance would

lead to increased ooirpetition and promote product improvement. Generally, FTC disagreement with the bill focused on language in section

5 (a) which seemed to suggest that the offeror process would be the

primary tool to obtain test protocols. The Cannission sought more

flexibility in this regard and recoirmended that the bill also make

clear that the Carmission has the discretion to make the testing of

consumer products and dissemination of the results thereof, voluntary

or mandatory, depending upon which approach wDuld best serve the public

interest.

The Department of Transportation opposed the bill largely on the basis

that it could produce conflicting standards with those of NHTSA, FAA

and the Coast Guard, thereby causing confusion and rendering the latter

ineffective.

The Department of Carmerce strongly supported the concept of more consumer product information but urged development of voluntary programs.

The National Bureau of Standards echoed its parent organization in

opposing mandatory requirements and endorsed voluntary programs. NBS

gave assiirance, however, that it could meet the responsibilities

assigned to it under the legislation, provided appropriate funding

would be forthcoming.

21
The Department of Justice strongly opposed S, 643, The Department's

views could be summarized by the following: consumers already have

access to considerable product information; the FTC has authority to

stop false advertising where it exists; the government should not be- cone involved to a greater degree in product testing; the proposed

testing would increase si±istantially the cost of consumer products;

and consumer injunctive suits are highly undesirable.

Consumers Union supported the bill but had reservations about certain

provisions. Basically, CU found the bill unclear as to what consumer

information wDuld be required. It reccnmended the bill be amended to

allow experimentation with various alternatives relating to the con- sumer information program. The most desirable consumer information

varies under different circumstances, i.e., from point of sale mandatory labeling in some instances to "take one" sheets at the counter in

others. CU noted there is a potential problem of too much information

v\fcLch could cause consumer confusion and this too requires experimentation to resolve. CU raised other questions including conflict of interest, translation of raw test data into performance grades, and the

determination of vrho best can develop a test protocol.

The American Society for Testing and Materials (ASTM) generally supported the concept but felt S. 643 could not meet the stated objective

as written. Specifically, ASTM felt the statutoiry time limits unworkable (180 days clearly inadequate) ; the statutory enphasis should be on

corrpetence in developing test protocols and not on technical ccupetence

per se; and, there should be clear provision for due process in developing protocols so that a consensus on protocols is reached with a minimum of government bludgeoning. ASTM also warned that the development

of standards is a costly business. ASTM's developmental work with

CPSC as offeror on the matchbook standard cost $213,000 and ASTM estimated another $250,000 costs were incurred by CPSC and private industry

before the project was coiTpleted.

Industry trade associations , representing ^pliance manufacturers, were

strongly opposed to the bill. These included the National Electrical

Manufacturers Association, Electronic Industries Association, Gas Appliance Manufacturers Association and the American Gas Association.

The objections of these groups centered on charges that the bill was

unnecessary, would be unworkable through the offeror process, v^rould cause consumer confusion by producing too much information, would result in severe damage to the free market econon^ by unwarranted intrusion of government into standard setting, would adversely affect ccxrpetition and reduce innovations in product design, and wDuld significant^

increase product costs far beyond any resulting consumer benefits.

Generally, consumer groups were not represented at the hearings, although the National Consumers League appeared and endorsed the bill.

NCL pointed to seme difficulties in the offeror process experienced by

22
CPSCf i.e. lack of consumer participation and insufficient funds ^ and

felt these had been corrected in the ci:irrent bill,

Fran the foregoing, it is clear that while there appears to be a con- sensus that disclosure of product information is good, there is a wide

variety of views as to hew this can best be acconplished

.

At this point, I would like to shift gears and move on to the second

point to examine the FTC's ongoing activities with respect to measuring product performance. The Canmission currently has several pending

proceedings which propose to require labeling of products with respect

to certain product qualtities or characteristics. I think it is pertinent to review these proceedings because they can provide insight into

factors which must be weighed in connection with any consideration of

labeling for durability.

Energy Policy and Conservation Act (EPCA.) — The testing and disclosure requirements of the Energy Policy and Conservation Act, P.L. 94-

163, are generally similar in many respects to those contained in H.R.

24. The major differences are that ]a>CA (1) vests responsibility for

protocol developnent in the Federal Energy Administration (FEA) , and

(2) sets forth limited and specific characteristics, energy efficiency

and cost of operation, that should be tested and disclosed to consumers. The FTC bears no responsibility for developing uniform test protocols.

Rather, the Ccnmission is charged with the development of prototype

appliance labels to insure that the annual operating cost of the products in question as well as the range of costs for conparable products

are effectively coimumicated to consumers.

The EPCA specified target dates for proposed and final rules concerning

each of three groupings of thirteen categories of appliances — the

rules to be adopted under section 553 procedures.

Group I proposed rule - 6/30/76

refrigerators & refrigerator-freezers final rule - 9/30/76

freezers

dishwashers

clothes dryers

hot water heaters

roan airconditioners

Group II

televisions

hone heating equipment

ranges and ovens

Group III

humidifiers & dehumidifiers

central airconditioning

furnaces

clothes washers

proposed rule

final rule

9/30/76

12/30/76

proposed rule

final rule

6/30/77

9/30/77

25
There has been considerable slippage in the target dates. At the present time, no final rules have been issued; with respect to Group I,

the responsible agencies are well over a year behind schedule.

The principal delay has been caused by difficulties encountered in developing acceptable test protocols. The FEA has now proposed testing

procedures for all thirteen categories and final procedures have been

adopted for nine of those categories with still others nearing completion. Final procedures are anticipated soon with respect to ranges and

ovens. On the other hand, it is expected that it will be some tdjne

before final test protocols are developed for central airconditioning

and furnaces. Similarly, hone heating equipment has presented the biggest problon because of the wide variety of products and resulting

_

variables involved and the lack of an industry standard. In sane instances, such as rocm air conditioners, the FEA's work was greatly

sirtplified by the existence of a largely acceptable industry standard.

In the meantime, the FTC has contracted the services of an expert to

conduct consumer research in an effort to determine the most effective

labeling technique to disclose pertinent energy related information.

This research has now been completed and the results are expected to

be available to the FTC staff in the near future. It is possible that

proposed labeling procedures will be issued by the FTC by the end of

this year for written and oral comment. If this schedule is met, it

is conceivable that the labeling rule could be final by September,

1978, v^ich, even if it does occur then, will be two years behind the

statutory schedule. In addition, the statute permits a 90-day lead

time for labeling carpliance, with an opportunity for an additional

90-day extension, if necessary.

In developing proposed labeling, the FTC is working closely with the

FEA and the expert v^o is analyzing consumer reaction. This is an extremely critical phase of the rulemaking because labeling that finally is adopted must be informative and also receive consumer acceptance.

Without the latter, critical information will not be imparted to potential buyers. Questions such as whether the information should be displayed in narrative form (v^ch can be cumbersane and complex) or by

some kind of scale (vdiich may be more meaningful but provide less data)

must be considered. Moreover, sane products, by their very nature,

create a more cotplicated situation. For example, dishwasher performance is affected by the amount (and perhaps kind) of detergent used;

the type of water (hard or soft) , and the frequency of use (daily,

full load, etc.). And, of course, utility rates will have an overriding effect on all of these factors.

Vacuum Cleaners — While the program to develop a cleanability standard for vacuum cleaners has been under development for sane time, it

has been held in abeyance for approximately the last year. During this

period, the Ccmnission has lacked the contract funds needed to support

2h
development of an adequate test protocol. The FTC had hoped to contract with the NBS to evaluate a test protocol that is being developed

by the industry, however, the cost of such an evaluation has been estimated in the neighborhood of $100,000. (NBS has already done some work

in this area under a voluntary program. ) While these funds may be

available in FY 78, a manpower shortage at the FTC may continue to

frustrate the project. So at this point, the immediate fate of this

proceeding is uncertain. If the proceeding can move forward, it appears it will take NBS at least a year to refine the protocol. At this

point, the ETC would then proceed under the Magnuson-Moss rulemaking

procedures, which have been protracted at best. From this, you can

see that standards for vacuum cleaners are still some time off.

Detergents — The PTC formally ccrrmenced its investigation into the

need for disclosures with respect to a cleanability standard for detergents approximately two years ago. An imnediate advantage was gained

in this proceeding frcm the fact that there is an existing, widely

accepted industry protocol. But even here, a problem exists because

the industiry standard is not adapted to the FTC's proceeding. First,

there must be a standard detergent for ccarparison purposes, and the

industry standard has not provided this. In the absence of a standard

detergent, there would be a meaningless corparison of Brand A with

Brand B or Brand C with Brand D. Second, the industry test protocol

is based on an outdated detergent containing 12% phosphate which, while

it apparently cleans better than lover phosphates, it appears to be

less desirable environmentally. Presently, most detergents contain 6%

phosphates, while sane contain no phosphates at all. Thus, the FTC

proposes to develop two test protocols — one for 6% phosphate detergents and one for 0% phosphate detergents. Each product would be

measured against its own class of products.

Other complications have been encountered with the detergent standard.

There are many potential variables in use, for example, results will

vary when (1) cold or luke warm water is used, or when (2) hard or soft

water, or (3) more or less detergent is used.

Further, problans arise if labeling is designed to encotpass all of

the foregoing possibilities. It might not only be potentially confusing to consumers, but it would be highly expensive. It is estimated

that each such test (hard water vs. cold water, etc.) costs approximately $20,000. Such an added expense has the potential of creating

an anticatpetitive effect. If a number of tests are required, it could

place a heavy financial burden on the small manufacturer and potentially bar him frcm the market. For this reason, it appears that the

FTC will consider one overall standard for irtplementation.

At this time, it is possible that a proposed detergent standard could

be published within six months. Such a standard conceivably could

affect advertising as well as labeling. It should be noted that this

25
proceeding is already meeting stiff opposition frcxn the predominant

soap and detergent maiiufa,ctiarers . There is sane speculation that the

Cdtmission may eventaully prcinulgate a guide instead of a rule.

Thermal Insulation — The FTC is expected to act manentarily in au- thorizing a proceeding which vvould propose requiring the disclosure

of "R" values in horvs insulation both in labeling and advertising.

There is an existing industry standard which appears to be acceptable.

Moreover, NBS, under its voluntary program, appears to have already

devised suitable testing for measuring performance.

The FTC's proceeding will be conducted under a newly streamlined

Magnuson-Moss procedure. It is anticipated that the new procedure will

take approximately a year, thereby shortening the existing time span by

years.

It is ray understanding that both the NBS voluntary program and the

FTC's effort will move forward in a coordinated fashion. Thus, even

though NBS may provide exclusively for flainnability and the FTC may

exclusively cover advertising, care will be taken to insure that the

ultimate standards do not conflict.

Durability — Frcm the foregoing, it is clear that the development of

test protocols to measure product quality and performance is a carplex,

time-consuming and expensive undertaking. This has been aptly demonstrated by the FTC's efforts with cleanability ratings for detergents

and vacuum cleaners and by the FTC/FEA attenpt to produce energy efficiency ratings for major appliances.

Ratings reflecting cleaning ability and energy efficiency will be based

on rather direct scientific determinations and vould therefore be more

susceptible to accurate measuranent than ratings based on more ccrnplex or subjective evaluations. For example, it vould be more difficult to

measure such product characteristics as "frequency and nature of repair," (contained in H.R. 24) since other factors are involved, e.g.,

performance is ccrtpletely dependent upon unknown factors of maintenance,

use and abuse of the products by consumers.

To a layman, it would seem that measuring durability would pose problems of unusual difficulty, more complicated than cleanability, for

example. The need to scmehow simulate years of wear on materials, or

on a mechanical or electrical device, is a step beyond the mere measurement of perfoinnance.

In any event, there appears to be at least twD levels at vi^ich an

assessment of durability could be helpful: (1) a calculated average

use of a product, and (2) an actual expected life-span of a product.

Obviously, while the latter would be more difficult to measure, it

would also be more informative to purchasers. But the degree of difficulty is not in my province to judge. The feasibility and ease of

26
developing tests to ineasure durability is a matter that you must deal

with.

Prospective Congressional Action '— As I stated earlier, no bills re- lating to this subject have been introduced in the Senate during the

current session. I would draw no conclusion either fron the absence

of legislative activity in the Senate or frcm the fact that two bills

sponsored by a number of Manbers have been introduced in the House. It

is not unusual for bills to be introduced over the course of several

years before they finally reach the Floor of either body of Congress.

While it appears that neither the House nor the Senate will consider

durability labeling in the current Congress, durability raises a strong

public policy question v^^ich will beccme increasingly urgent as an

awareness of our depleting natural resources and energy supplies con- tinues to grow. (It is ray mderstanding that materials production in

the U.S. consumes about 25% of total energy used.)

However, even though initial indications suggest the desirability of

developing a test protocol on durability, other factors will also be

given consideration. While greater product durability and materials

conservation are highly desirable objectives, they may require tradeoffs of increased costs and the risk of reductions in technical innovations. (With respect to cost, it has been estimated that development

of a test protocol frcm scratch would cost about $1 million. ) Moreover,

material savings are apparently not directly or necessarily proportional

to a longer life. (In a study done for OTA, it was found that if mechanical lifetimes of refrigerators and automobiles were extended 50%,

sales and materials consunption would be reduced only 15% and 9%, respectively. )

There is also the ccarpetitive issue to consider. Opponents of any

labeling effort related to product chaxacteristics state that government involvement has an anticarpetitive effect because a new or lowvolume manufacturer may not be able to meet the added expense of testing and labeling. The counter to that argument is that governmental

involvenent would favor the new or small entrant into the field (and

therefore have a good catpetitive effect) because the small company

could concentrate on high quality of a few products which could be

labeled as such, and would not have to ccftpete on the basis of advertising which the big corpanies can afford.

Whenever a test protocol is feasible, however, the need for consumers

to have an opportunity to make intelligent and discriminating purchasing decisions in the marketplace should be carefully balanced against

any potentially negative factors.

In conclusion, I would say that pi±»lic policy strongly argues in favor

of developing a capability of measuring durability with respect to a

27
wide range of produc±s. If legislation is eventually enacted, it is

conceivable that it would fall somewhere between the two bills that

currently have been introduced in the House. Obviously, this is impossible to predict at this time. It would be my personal judgment,

however, that there will not be definitive Congressional action in this

area until such time as the pending related projects are conpleted and can be fully evaluated.

28
SESSION II

PRODUCT TESTING

CHAIRMAN: A. J. FOWELL

i NATIONAL BUREAU OF STANDARDS
I

j

I

I
METHODOLOGY OF PRODUCT LIFE TESTING

Julius Cohen

Center for Consumer Product, Technology

National Eureau of Standards

Washington, D.C. 20234

Abstract: A methodology was formulated for estimating,

through laboratory testing, useful life and associated

performance of consumer products. Excerpts from two key

parts —concepts of reliability engineering and procedure to

guide the formulation of tests--are given here. Criteria

for assessing tests are presented.

Key Words: Consumer products; testing methodology;

reliability engineering; useful life.

INTRODUCTION

Test methodology is a generalized, coherent body of

operational concepts, terminology, rules, methods, and

procedures. It is used to guide the formulation of

particular tests. The purposes of this methodology are 1)

to standardize testing; 2) to make testing more objective

and accurate; 3) to make test designing logical and easier

(because one does not have to rethink the steps each time)

.

A methodology was formulated for estimating, through

laboratory testing, the useful life and associated

performance (e.g., failure classification and mechanism;

reliability) of consumer products. It is not feasible to

present the full scope here; instead, extracts from two key

parts—concepts and procedure —will be given. Also, the

assessment of tests will be considered.

BASIC CONCEPTS

The six basic concepts of reliability engineering are:

performance, failure, maintenance, repair, reliability, and

useful life. These will be defined and performance will be

seen to be the primal concept.

51
First, however, a few prefatory definitions: Use conditions

are the manner and method by which a product is employed,

including the load (that which is acted upon or processed by

a product for accomplishing its main utilitarian purpose)

.

Environmental factors are those elements in the surroundings

of the product which can be expected to influence

performance. Examples are temperature, humidity, dust, and

vibration

.

Performance is defined as the selected and designated

accomplishments of a product under specified and implemented

use conditions and environmental factors

.

A consideration of the concept is warranted by its eminence.

It is tacit in the definition, above, (which labels the

concept) that performance is not an intrinsic property of a product. Rather, it is the resultant of precepts; its

implementation; and product. The test designer issues the

precepts—it is he who specifies the use conditions and

environmental factors; selects the accomplishments from

among many possible attributes; and sets the criteria for

satisfactory and unsatisfactory performance (failure) . But

his precepts must be implemented by people and by apparatus,

and that which is established and that which was called for

may not be the same. Then, the results may be spurious.

The rule is: Do not accept failures at face value

investigate and confirm or invalidate.

The notion that performance is the reaction of a product to

an applied stress--stress being the conjoined use conditions

and environmental factors--is useful for making analyses.

Normal stress means the way the product is most usually used

in the field (or home) , including the accompanying

environmental factors. Understress and overstress mean,

respectively, less severe and more severe than normal. In

systems, containing components, all three kinds of stress

may be operating simultaneously. Additionally, 1) elements

of stress may be synergistic; e.g., temperature and

vibration; and 2) performance may be nonlinear with stress;

i.e., a small increase in stress may have a large, even

inordinate, effect on performance. This completes, for the

time being, the consideration of the performance concept;

the other concepts will now be mentioned.

Failure is defined as the inability of a product or

component to perform a function in accordance with test

specifications

.

Usually, minimum levels of performance will be specified for

systems. Failure and satisfactory performance are quantal

52
something either performs satisfactorily or it does not

there is no in-between.

Maintenance is defined as a prescribed action executed on a product capable of performing satisfactorily, to prolong its

period of capability.

Repair is defined as an action carried out on a failed

product to restore its ability to perform satisfactorily.

Reliability is defined as the probability that a product

will be able to perform satisfactorily within an arbitrary

duration. (It is assumed that the product will be capable

at the onset .

)

Useful life is defined as the duration of satisfactory

reliability measured from when the product is first

employed.

The above definition is consistent with English usage, but

more importantly it meets the needs of cost-conscious

consumers. That others may dispose of products beforehand

for whatever whim or reason does not detract from a product's capability.

Usefulness of a product is intimately bound up with

functionality in the sense of both intended performance and

service expected as due. Specifically, if a product

generally performs satisfactorily, does not break down in

use, and will perform satisfactorily when demanded, the

product is useful. These criteria can be summarized with

the single term, reliability, as satisfactory performance is

inherent in reliability. Factors influencing reliability

expectations are 1) the nature and structure of the product;

2) the age and condition of the product; 3) maintenance; 4)

purchase price; and 5) repair cost. Unlike satisfactory

performance criteria which remain constant throughout the

product's life, satisfactory reliability criteria generally

change as the product ages and expectations change.

Wow that the six basic concepts have been given, notice how

the performance concept pervades all others. Important as

they are, the others are still satellite concepts which owe

their existence to the need for satisfactory performance in

the present and in the future. And however sophisticated

the statistical handling of the test data be, whatever is

derived—e.g., reliabilities; mean times —will be for naught

if the performance test itself is not sound.

33
PROCEDURE

The goal of the laboratory life testing is to generate

normal failure modes; i.e., those which prevail in the

field, and to ascribe average times to failure. If the

product in the laboratory receives an approximately normal

stress, normal failure modes should result and in

approximately the same amount of use time as that in the

field. If the product is overstressed too much, failures

will occur rapidly, but they may be abnormal. On the other

hand, if the product is understressed too much, failures may

not occur at all and there will be no data; in any event,

the times- to-failure will be prolonged. Little wonder the

test designer wants to know what constitutes normal stress;

market research and observation of human subjects are

possible means of assistance. And does there exist any

other field where failures are the measure of success?

Now, a generalized procedure, in outline form, will be

offered for guiding test formulation;

1. State Test Objectives

Example: To estimate useful life and associated performance

of a widget.

^ • List Data to be Sought

Example: a) probable useful life, together with

confidence level and limits;

b) number and type of maintenance actions during

useful life;

c) number and causes of failures, repair actions

(components, materials, time-to-repair)

during useful life.

3. Search and Familiarization

a) Sampling Characterization

1) homogeneous or heterogeneous? (If heterogeneous,

different tests for different units may be

required .

)

2) repairable or nonrepairable?

3h
3) product evolution slow or rapid? (If slow,

historical data will be of value. If rapid,

historical data may be of no value: the product

may be obsolete by the time tests are completed.)

b) Historical data, particularly as regards failure modes,

mean times to or between failures and stresses. (For slowly

evolving products, historical data, if available, will not

only greatly facilitate test design, they may also permit

accelerated or overstress testing to be made.) In-warranty

data, service records, laboratory results are all useful

information

.

c) Existent Tests—if available, review for applicability.

d) Published Literature—service manuals, trade journals,

market research reports, etc.

e) Discussions—with design and test engineers, home

economists, etc., to aid in making judgments.

f) Inspection—design; construction; materials; operation.

Identify major working parts and likely wear-out contenders.

(This is to aid test design, but guard against becoming

biased therefrom.)

4 . Test Design and Development

a) Human Factors Input

1) Determine use conditions; load; use-environment,

all as a population distribution. (These may not

be independent variables)

;

2) Frequency and duration of use;

3) How was information obtained (e.g.,

questionnaires, observatons ) ?

;

4) Number in sampling;

5) Is sampling random? How chosen?

6) Is sampling representative of user population?

7) What will be the confidence level and limit of

these data?

55
b) Identification of Stresses

Which use (including load) and use-environment conditions

are known to or believed to affect performance

significantly? Consider use and environment singly and in

combination. Examples of possible environmental factors:

ambient temperature; humidity; dust; mechnical shock;

vibration; temperature and humidity, temperature and

vibration.

c) Selection of Stress Pattern

1) If historical data are available, consider

accelerated testing and how this test might be

integrated with the previous; if no historical

data are available, avoid atypical overstress and

attempt to use normal stress testing where

possible

.

2) Restrict testing to prime stresses only (side

experiments may be desirable to help in

determination)

.

3) Prescribe use, load, and environmental factors;

specify allowable ranges; include customarilyexpected overstresses ; prescribe operating time

schedule

.

d) "Stress" Analysis

1) List major components of product, especially those

known to or believed to fail typically in use.

2) Indicate whether these components will be over-,

under-, or normally-stressed by stress pattern.

3) Consider desirability of altering stress pattern,

above [ 4 .c) 3) ]

.

e) Performance and Failure Specifications

1) State main utilitarian function (primary

performance attribute) ; specify (usually minimum)

level of acceptable performance.

2) Specify salient secondary performance criteria.

Examples to consider are degradation of the load

by the product; excessive noise; excessive

vibration; leaking of liquids or gases56
f) Specification of Useful Life Criteria

1) Specify minimum acceptable reliability or

reliabilities (consider aging of product)

;

2) Specify maximum acceptable repair cost;

3) For allowable repairs, specify reliabilities which

will justify costs.

It is advisable to obtain human factor data to assist in

determination of the preceding three criteria.

For repairable products, useful life terminates with failure

to meet criterion 1, 2, or 3 above. For nonrepairable

products, useful life terminates with failure.

For products where average retention life is less than

probable useful life, it may be desirable to terminate

testing or a portion thereof at a time equivalent to the

former

.

g) Sampling

1) Estimate number of units required for a desired

confidence level and limits; or

2) Estimate confidence level and limits for the

number of samples obtainable. Are they

satisfactory?

3) Obtain random sampling, if possible.

h) Repair Readiness

1) Are replacement parts readily available? If not,

stock selected parts.

2) Are qualified repairmen on site? If not, secure

or have personnel trained.

i) Controlled Field Tests

1) How many units (or households) are desirable or

are accessible?

2) How are units (households) to be selected?

Consider, for example, geographic location; income

level; and size of family.

57
3) How are field data to be obtained? Some

possibilities are manufacturer's in-warranty

records and other service records. Can

arrangements be made with consumers to provide

free or discounted repairs beyond warranty period?

Can monitoring instrumentation be installed on

products?

j) Feasibility

1) Consider funding, qualified personnel, equipment,

facilities, time duration of project, etc.

2) Estimate what may be feasible under the above

constraints

.

3) Modify statement of objectives or data to be

sought, if indicated by 2, above.

5 . Test Execution

ALL PERFORMANCE CRITERIA AlvJD USEFUL LIFE CRITERIA MUST BE

SPECIFIED IN ADVANCE OF TESTING! (This is a safeguard for

objectivity.

)

a) Simulate prescribed use conditions and environmental

factors

;

b) Monitor performance frequently;

c) Note, inspect, and identify all failures (be on guard

for spurious failures)

.

d) Make qualified repair if appropriate (see 4.f); return

unit to test.

e) Maintenance

1) Carry out (only) all maintenance actions

prescribed by manufacturer, (Exception: if

maintainability is so poor as to preclude a maintenance action by consumer, this may be

omitted at discretion of test designer, but the

omission should be noted.)

2) Correction of incipient failures are to be

included as maintenance actions.

38
f) Keep complete records of data; data forms prepared in

advance are useful.

g) Testing of a unit terminates in accordance with useful

life criteria.

6 . Test Analysis and Interpretation

a) Data handling: avoid omissions; avoid rationalized

"laundering"; avoid unjustified extrapolations. Early

failures (infant mortalities) are customarily not counted in

reliability and life testing.

b) Is test acceptable?

1) validity?

2) reproducibility?

3) correlativity? (Do failure modes and

distributions of laboratory and field tests

agree?)

c) Reappraise assumptions in light of field data.

d) Repeat "stress" analysis in light of field data.

e) Revise for future tests, as required.

TEST ASSESSMENT

Performance testing seeks to assess the qualities of a

product. That it does so satisfactorily should not be

assumed; it is conditional on the quality of the testing

meeting standards. Thus, the quality of testing itself

needs to be assessed and the criteria are 1) validity, 2)

reproducibility, and 3) correlativity. All three criteria

need to be met.

Validity is the truthfulness of the data; it relates to

whether what is claimed to be measured is in fact measured.

Causes of invalidness include faulty instrumentation; human

errors in measurement, judgment, and reasoning; errors or

negligence in sampling selection; failure to recognize or

distinquish primary and extraneous factors.

Reproducibility measurements establish the consistency of a

test. It is not sufficient that tests be reproducible

59
within an individual laboratory; to have utility, there must

also be interlaboratory reproducibility. Failure to obtain

reasonable reproducibility may cast serious doubt on the

test's validity. Reproducibility depends in general on 1)

sampling constancy or invariance; 2) measurement apparatus,

techniques, and skills; 3) following of instructions and

carrying out of test procedures.

To abet attainment of reproducibility—particularily

interlaboratory—different samplings should be chosen

judiciously to ensure they are virtually equivalent. For

intralaboratory testing to establish precision, the time

between successive tests should be kept short so that

constancy of the product may be reasonably assumed. Also,

test procedures and descriptions should be written clearly

and precisely, to minimize the possibility of

misunderstanding or sub jectiveness by test engineers or

technicians

.

The usefulness of performance testing in the laboratory is

contingent on the relevancy of the results to those which

actually occur in the field, and the quality of the

relationship is the correlativity

.

Correlativity is the quality or state of exhibiting

correlation between results of performance testing in the

laboratory and corresponding results obtained from field or

home use.

Obtaining or demonstrating correlation, however, is

difficult and may be full of pitfalls: 1) it is difficult

to determine or predict what actual normal use conditions

and environmental factors in the field are; 2) use and

environment generally cover a much broader spectrum in the

field than is feasible to simulate in the laboratory; 3) it

is often difficult to simulate changing environmental

factors accurately over a prolonged period of time; 4)

product evolvement, manufacturing or material changes, and

variations in conformance of manufactured parts to design

specifications make a statistically significant and random

sampling difficult; 5) the requirement of reproducibility in

laboratory testing may impose conditions which are not

representative of actual field use.

Laboratory data are obtained from controlled testing; field

data may be from (partially) controlled testing or

uncontrolled activities, such as surveys.

Consider first uncontrolled field data. Information is

obtained from the consumer on the frequency and nature of

ko
repairs, retention life, and possibly the reason for

disposal. There are several pitfalls: 1) maintenance

actions, which are important factors in life, performance,

and reliability, may not have been carried out as specified;

2) products may have been misused or abused; 3) the consumer

may not have perceived failures accurately or in conformity

with the test designer's definition; 4) repair actions may

not have been made proficiently; e.g., primary failure may

not have been recognized and corrected; replacement parts

may have been of substandard quality; workmanship may have

been poor. If repairs are not proper, failures will occur

prematurely; 5) the retention life is not necessarily the

same as the useful life, and indeed products are often

disposed of before the end of their useful life; e.g.,

because of obsolescence or for aesthetic reasons. Thus,

uncontrolled field data pose a serious problem in validity.

Do the data represent what are supposed to be measured or

represented, free of extraneous, unaccountable or

unrecognized factors which cause deleterious results?

Because very little performance data on consumer products

throughout life exists at the present time, the problem is

perhaps academic, but it does point up the pitfalls inherent

in any approach which attempts to correlate laboratory

results with uncontrolled field results. It may be possible

to indicate validity through use of statistical tools, but

the problems would be considerable.

It is desirable, perhaps even necessary, to resort to

controlled field tests instead. Here, a sufficiently large

number of new units, randomly chosen together with those for

laboratory testing, are placed in the field and periodic

inspections are made by qualified technical personnel with

appropriate test equipment and parts, to help ensure that

prescribed maintenance is done, to confirm the accuracy of

the consumer's perception of failure to the test

specifications, and to carry out repairs proficiently, when

necessary. Only the stress pattern (use conditions and

environmental factors) is not controlled. On the other

hand, in the laboratory, the stress pattern is controlled,

and this is presumed to constitute the only difference

between laboratory and controlled field tests.

Controlled laboratory and controlled field tests together

constitute an experiment in which there are presumably only

two variables: laboratory stress pattern and field stress

pattern. The chances of demonstrating correlation are

considered good and the analysis of results is much

simplified.

hi
SMALL APPLIANCE LIFE TESTIMG

Kenneth W. Yee

National Bureau of Standards

Washington, D.C. 20234

Abstract: V/ork has been underway at the National Bureau of Standards,

Center for Consumer Product Technology, to determine the feasibility of

and methodology for developing standard test methods to estimate the

useful life of consumer products. Initial efforts have been on small

appliances. The hand-held blow hair dryer was selected for the

demonstration product. The status of current work on the hair dryer

will be described. A similar effort on a major appliance has been

undertaken and will be described.

Key words: Consumer product testing; life test method; useful life.

During the past year, work has been underway at the National Bureau of

Standards (MBS), Center for Consume*" Product Technology, to determine

the feasibility of developing standard laboratory test methods to

estimate the useful life of consumer products. Previous work has been

done to establish the methodology for consuiTie^ product testing.

Current work is intended to determine the feasibility of, and identify

the barriers associated with, developing a laboratory life test method

and will not necessarily result in a completed test method for a specific product.

Why develop a life test method? Proposed legislation would requi'^e

disclosure of life or durability information for consumer products and

the Department of Commerce now has a voluntary Consumer Product

Information Labeling Program (CPILP) underway on a trial basis. This

program is intended to make information available at the point of

purchase, which will assist in the purchase decision and which is not

readily discernible. Certainly information on product life would be

valuable in making an informed purchase decision.

Industry now does extensive testing related to product life. The test

methods used, however, are not suitable for providing uniform life ' information on all the models of a product class available in the

marketplace. Industry testing is generally intended to evaluate I designs or determine if design goals have been realized by production • units. Testing is frequently terminated when design-goal operating ' time has been achieved and units are not run to destruction. Design

j k2 :

I

i

!
goals are different for each manufacturer depending on the individual

performance, reliability and cost objectives. The industry tests are usually developed for a specific manufacturer's product designs and

models and may not be universally applicable. The tests are considered p'-oprietary and would not generally be released for use by

others. A major limitation is that the test methods do not provide

independently reproducible quantitative measurements. The '^esults are frequently of a pass-fail nature and may requi'^e subjective judgment

as to what constitutes a failure or end of life. Many tests provide

only comparative information: that A lasts longer than B where A may

be the old design or previous production and B a new design or production lot.

The methodology followed in developing a test method for small

appliances includes evaluating the design and performance of

representative products in the marketplace; determining the use conditions and failure modes of the product; devising a laboratory

test incorporating the most important use and environmental

conditions; correlating the laboratory test results with actual

failures or life in the field; modifying the laboratory test as necessary to provide better correlation with field results.

Unfortunately not all of these steps are easy to complete adequately.

Evaluating representative products is limited only by the time and

money available to shop for sanples and examine them. One will never obtain samples of all the models made, but enough to ascertain the

typical design techniques and performance can readily be obtained.

Our limited experience has shown that good quant itive, statistically

valid information on the use, abuse and environmental conditions and

failure modes for a product are not available. How long, how often,

where, under what loads, what voltage, what temperature, etc. the

product is used are not »"eally known. In most cases it is not known

how long products last or why people dispose of them or if and how

they have failed.

A laboratory test method can never incorporate all the use and

environmental conditions that affect a product's life. The best one

can do is to incorporate the factors that most significantly affect

product life. Without good information on hov/ long the product lasts

and v^hat fails, correlation of the laboratory test results and field

results is difficult. The method used is a controlled field test

where a limited number of instrumented products have been placed in

the field. After all the preceding steps the test method may have to

be modified to change the test conditions or incorporate additional

factors which have been found to be significant.

The goal of the initial laboratory effort at NBS is to develop a test

method that will estimate the useful operating life in hours. An

ultimate goal is to estimate the useful life in years. A simple

motorized product, the hand-held blow hair dryer, was selected for the
test. It has low but significant cost in the $10 to $25 range, with

significant sales and market saturation, about one million units per

year and 157o saturation. A failure is easy to define, generally there

is no ai"" output or no heat output and there is negligable loading

effect by the user. It is generally not repaired beyond the warranty

period.

Even for this limited product class there are many variables. There

are significant design differences in ai'" flow pattern (radial and

axial) and motor type (universal and dc permanent magnet) as shown in

Figure 1. The use pattern is not well known, but various surveys

report time per use of from 5 to 25 minutes and uses per week of from

1 to 7. This variation makes the transition from life in terms of

operating time to years difficult. An estimate is about 25 to 50

hours per year. Additionally, there are manufacturing variations in

the same tnodel, some due to quality control and some due to design

changes or alternate sources for components.

Many factors were considered in designing the initial laboratory test.

The sanple size is limited to 15 to 30 units due to power consumption

and room heat exhaust capability. The pov;er consumption of blow hair

dryers is now in the 800 to 1500 watt range. Twenty produce as much

heat as a typical 'residential electric furnace. The cost of the test

samples and the noise generated by the units are additional

considerations limiting the sample size.

It has been found that motor loading and exhaust air temperature are

not affected by the presence of a head 2.5 centimeters from the

outlet. The heat-up and cool-down times for a representative motor

bearing were measured and are shown in Figure 2. The temperature

essentially stabilizes within 10 minutes after turn-on but takes much

longer to cool down after turn-off. A 10-minute on and 10-minute off

test cycle was selected as a compromise between the actual use cycle

and accumulating the maximum operating time in a given clock time

period. Subsequent tests indicate that operating time variations in

the region of 5 minutes to 30 minutes have little effect on life in

operating hours.

In the tests, the units are fixed in one orientation and powered from

a regulated 120 volt ac supply which is switched on and off by motor

driven cam-operated switches, see Figure 3. The dryer power switch is

not tested since it is subject to a UL endurance requirement of 6000

cycles. The heater is operated at maximum power level. The dryers

are not subjected to any vibration, dropping, hair or hair spray which

all may affect life. The units in a test sample are all of the same date code or manufacturing lot to eliminate design or alternate

component differences. The test ambient temperature is similar to a warm bathroom, but the effects of high humidity have not yet been

investigated.
Six test lots including several models of about 15 units each have

been run in the laboratory. Operating lives from 100 to over 1500

hours have been observed. A test takes 10 to 150 days to complete

with the units operating 2U hours a day at 50% duty cycle. Ratios

from 1.5:1 to 2.5:1 between the longest life and shortest life samples

in a test lot have been observed. The Weibull chart, Figure U, shows

the results of a typical test. The mean life of this lot was 179

hours and the standard deviation M2 hours. All failures for this test

lot were motor brush wear out. Except for a few manufacturing defects

(early failures) all failures observed have been related to motor wear

out. In some models both brush and bearing failures have been

observed. Motor slow down results in a failure as the dryers are protected by a thermostat which turns the heater off when the exit air

temperature rises due to reduced ai*" flow. Preliminary results

indicate that this test method can measure significant differences in

operating life. There is a question as to the significance of

operating hours in excess of a few hundred hours in view of the

estimated 25 to 50 hours annual use.

A laboratory experiment is planned for the near future to determine

the effect of a periodic shock to the dryer on the measured operating

life. Each dryer will drop about 2 centimeters twice each on-off

cycle. This experiment is intended to determine if the effect is

significant and is not intended to be representative of shocks that

occur in normal use.

Two efforts are underway to provide some correlation between the

laboratory test results and actual field results. About 50 discarded

hair dryers have been collected and examined. Unfortunately most have

been very old designs or of the styler (side air discharge) design

rather than blower design. Failures attributed to the motor, heater

element, fan, switch, thermal protector and cord were observed. Most

failures were possible effects of manufacturing defect or were random

failures. Surprisingly, 8 of the units are the same model and all

failed due to motor slow down caused by bearing wear or contamination.

Their operating hours as estimated by the users ranged from 10 to 350

hours. None of the discarded units is a model that has been run in

the laboratory. The discarded units show that a wide variety of early

and random failures occur and failure due to motor wear can occur in some models.

A controlled field test is underway to provide information on units of

the same model and manufacturing lot as one lot run in the laboratory.

Thirty units were instrumented with a box, shown in Figure 5, that

records operating time and the number of times the unit is turned on. The box was designed and built at NBS to make the measurements at the

end of the power cord without any modification or other attachment to

the product under test. These dryers are in use in households with

more than one user of the dryer. The dryer recording boxes were read
after eight weeks of use. The use averaged 1/2-hour per week and

about 3 minutes per turn on. An unanticipated occurrence is that iiany users turn the dryer off and back on during one hair drying session.

The total minutes per drying session cannot be found without knowledge

of the user's habits. Better use information will be obtained after a longer period in the field. To date there has been one ea'^ly failure

which may have been caused by a design or production defect. "lOtor wear out in the field is not anticipated. The samples in the

laboratory test have exceeded 1500 operating hours. Between the time

of an initial test of this model, the results of which were shown in

the V/eibull plot, and the acquisition of the lot used in the field

test, the manufacturer changed motor suppliers. The visual

differences are minor but the operating life of the new motor is

greater by an order of magnitude.

In the next year the test method will be modified to include the

additional complication of variable loading by the user. The electric

hand drill or the electric hand mixer is under consideration as a demonstration product. The applicability of overstress accelerated

testing will be investigated.

A similar effort has been undertaken for a major appliance, the

electric clothes dryer. This appliance v;as selected as the simplest

major appliance. Compared with the hair dryer the clothes dryer is

indeed major. The clothes dryer costs about 10 times the cost of a hair dryer, will^be repaired, and has an estimated service life of

almost 14 years. The testing involves many more factors: powe'"

requirement, heat and moisture exhaust, test space, clothes load,

rewetting, lint, and time.

Supplying regulated power and exhausting the heat and moisture for the

dryers requires a major capital investment. Five electric dryers

produce as much heat as a typical electric house furnace. End of life

is not a simple judgment. Most failures are repairable and an acceptable repair cost is an economic decision which may be a function

of the age of the dryer and the cost of replacement. For sane individuals, sufficient reliability will be a consideration.

Testing time is long even if compressed time accelerated testing is

used. To accumulate the operating cycles equivalent to 14 years of

use at an estimated 8 loads per week takes 8 months of 24 hour per day

testing if one cycle is run each hour. Additional time is requi'^ed

due to equipment failures, intermediate testing, holidays, etc.

The goal of the current effort on clothes dryers is to denonstrate the

methodology and determine the barriers to developing a laboratory life

'Ruffin and Tippett, Service-Life Expectancy of Household Appliances,

Home Economics Research J., March 1975, Vol. 3, No. 3

k6
test for a major appliance. As shc^t terra objectives vie hope to

determine if energy efficiency changes over the life of the dryer;

determine if repair incidence and the natu'^e of probable repai'^s over

the life of the product can be measu'^ed in the lab; and determine if

it is feasible to estimate life in tenns of cycles or operating hours

and ultimately years.

Sixteen dryers have been run in the laboratory for a six-month period

(see F'igure 6). Eight dryers of two popular brands and models are under test. In the present installation, excess lint which passes

through the machine filter is captured by a nylon stocking and the room ventilating system is capable of handling the exhaust. Each

dryer is automatically resta^-ted and the test load automatically

rewetted. The normal test load consists of 2.,5 kilograns of bath

towels wet to a moisture content of SOX of the dry weight. A load

takes about 40 minutes to dry and is restarted once each hour.

Periodically a load of twice the weight of towels is run to simulate

normal overloads. An additional load with metal buttons is used as an

ab'^asive test load. One model has accumulated 4 years of loads and

the other 6 years of loads. One early failure of a timer and one randan failure of a heate*" element have been observed. Mo change in

energy efficiency has been measured. Wear out failures are anticipated in the next calendar year of testing.

In conclusion, we have demonstrated that a laboratory life test can identify significant differences between various models of hair

dryers. It is not yet known how the laboratory measured operating

life and the operating life in the field are related. The

significance of laboratory life in excess of a few hundred hours is

not known for the hair dryer. Perhaps this indicates that wear out is

not likely to occur and that early or random failures, which may be

related more to quality control than design, will dominate in use. The results of laboratory testing on clothes dryers is too incomplete

to draw any conclusions.

hi
1^8
80

40-

HEAT UP

COOL DOWN

TYPICAL BEARING HEATING /COOLING VS TIME

OF A D.C. MOTOR

J L

I L

5 10 15 20

TIME (MIN)

25 30

Figure 2. Bearing Heating/Cooling Time

^9


52
55
PRODUCT LIFE TESTING AND DURABILITY

N. R. Pugh

Governmental and Technical Liaison

Sears, P>.oebuck and Co.

Department 817

Sears Tower

Chicago, IL 60684

Abstract: This paper considers testing for product failure prevention

from the standpoint of a laboratory in a retailing system based on "private-label" product lines.

The point of view of such a laboratory in product design evaluation and

testing programs is described briefly.

Some thoughts are presented about the need for consumer product durability testing, considering the present level of product life, and the

state of the art in consumer product technology.

Some of the challenges in predicting durability, and minimizing failures, through laboratory and field test programs, are explored. Examples of testing for durability evaluation are discussed. The relationship of design quality evaluation to conformance quality, both as- manufactured and after extended use, is examined. Examples of testing

for durability evaluation are discussed.

The interaction of factual information and consumer receptivity; and

the effectiveness of durability and life information, is considered.

Lastlv, some opportunities for real accomplishment through better teamwork among various elements—governmental institutions, academe', and

the private sector are described.

Key words: Consumer product life; durability; testing.

RETAILING AND THE PUBLIC :

To clarify the point of view of this paper, some points about the role

of retailers in general, and Sears' merchandising system in particular,

should be made.

First, retailers face the public directly and constantly, bearing the

brunt of consumer dissatisfaction with many types of errors. Consumers

tell us about quality errors made by manufacturers and wrong decision^;
we make on behalf of customers. We also must deal with complaints

about regulatory decisions which add cost, and impair product function,

without clear benefit to consumers.

Secondly, retailers act as purchasing agents for the public; through

the decisions they make on what products to put on the shelves.

Third, a private labeler must get involved with a much broader array

of products than the typical manufacturer, and must work closely with a wide variety of manufacturers, both large and small.

Lastly, it is necessary that private-labelers make "trade-off" decisions for consumers, based on knowledge of consumers' wishes and sense

of values—and we must be right at least m.ore often than we are wrong.

In the intensity of today's competition, a retailer who tries to offer

more of any product characteristic than customers wish to pay for, is

penalized—as much as the merchant who does not offer enough.

These factors help to explain why we have developed a special view

of the new challenges to the consumer product field -- broad,

complex problems of an unfamiliar kind.

An underlying factor in many cases is the enormous impact of improvements in communication. Events which only a generation ago would be

known to only one locality, can now receive nation-v/ide attention,

almost immediately. This phenomena has not been lost on politicians,

whose survival depends on sensitivity to public reactions. As a result, solving consumer product related problems requiring excellent

technology is often unnecessarily complicated by political input.

In fact, we are concerned because too many such problems are approached

more on a political/dramatic basis than in a genuine problem solving

mode.

In a merchandising organization, we are conscious of the importance

of imagination and enthusiasm; make no mistake about that. On the

other hand, we believe that there is a special need for the MFPG,

and similar groups, to promote valid techniques of problem solving,

even though it is not easy to accomplish.

For a start, we suggest a close examination of where typical consumer

product life stands today, in relation to consumer wants, needs and

long-range interests.

We believe that learning how to prevent failures, and building longer

life into products, justifies considerable effort. At the same time,

it seems important to recognize also, that the private sector,

55
I

j responding to consumers wishes, has provided a pretty good level of i product durability and life, in irost products. |

For example, with reasonable care most automobiles will go 100,000

miles or more. Carpeting is being offered which vjears on and on, even in relatively hard service. ¥^ny textile products are discarded, 1 not because they have become unserviceable, but because they are no longer "in style".

In other words, it seems clear from the record that consumer products

^ generally provide a reasonable level of durability, overall. For

example, the MIT studies on "Servicing of Produc.ts"and "The Real Cost

j of Consumer Appliances", documented impressive improvements in

reliability and life, for some products.

j In our own experience, we find that a very large percentage of sales ^ do not result from failure of the current product, but because that

product has become obsolete through the improved functions, features j and style, offered in today's products. I

This is not to say that there is little more to accomplish through the

application of sound engineering principles to consumer products. We

will talk Fore of that a little later. The point is, however, there is a need to keep a sense of perspective about current demands for longer

product life.

One important technical challenge lies in developing a discipline to

determine vjhich components of products are most vulnerable, to zero i in on the v/eakest link in product construction. In the Scars I Laboratories, this is an ongoing process, but we are quick to admit

that all of us in this field still have lots to learn. Along the way,

however, we have developed some strong beliefs — some might say

biases. j For example, while there has been a lot written about planned obsolescence, and how easy it would be to make longer lasting products,

j we believe insufficient attention has been paid to the opposite side

of the coin. In our observation, more components in consumer products

are over-designed, than under-designed, for optimum value. That is, j a more nearly optimum design would use many less expensive components ' and materials, with reduced, but still adequate, reliability and

durability. Of course, in a truly optimum design, some components

and materials (the "vTeak links") would probably be more costly.

There is little mystery about which are the "weak links", in the minds

of the engineers who are designing consumer products, and there are constant efforts to upgrade those key items, within severe cost

restraints. Belts, bearings, brakes and insulation (electrical and

56
thermal) , are examples of parts which often limi-t durability.

Improvements in durability through selection of more expensive

components is usually possible, but the trade-off of extra life for

more cost may not be rewarding in the competitive marketplace. On

the other hand, in particular designs, these same components may

be over-designed in comparison to other parts of the product. Often,

it isn't that much more expensive to get a better quality component,

and the extra reliability and durability of that component may be

excessive in comparison to the total.

The key to optimum design is balance and consistency. However, a great deal of high-quality research will be needed in order to

provide an information base adequate to the purpose. Such formal

research as has been done so far is unimpressive, for a variety of reasons. One of the most important is that seemingly simple questions

in this field almost invariably turn out to be difficult to answer.

Furthermore, the life cycle of many products extends well beyond

major changes in state-of-the-art, "obsolescence by improvements."

For example, there are a lot of ranges in excellent condition which

are quite obsolete in comparison to the self-cleaning oven, the.

microwave oven, the smooth- top range, and induction cooking, for

today's homemakers. In retrospect, consumers might ask: "Why were

ranges made that lasted so long?"

Next, we should consider the effect of serviceability on total life

cycle costs. Service costs are escalating, mainly from the more

expensive equipment and more highly trained people required to service

today's complex products. For many products, it seems that rather

than emphasizing component durability, future minimum life-cycle cost

designs should emphasize improved maintainability and serviceability.

Admittedly, the picture is complicated by unpredictable extremes of

use. Many products are subject to harm because people who are not

part of the design system make sub-optimizing decisions. For example,

a person whose primary responsibility is to get the snow off the

street as fast as possible after a heavy snowfall, does not have the

incentive to make a thoughtful trade-off in corrosion damage to automobiles. Similarly, an untrained serviceman can do great harm to a product which otherwise might seem to be of excellent design.

In summary, this overview section has attempted to raise some questions

which are important, but may not have received enough attention to

date.

57
DURABILITY TESTING km ANALYSIS:

Sears Laboratories' efforts in this field emphasize engineering design

analysis and "testing by exception". That is, a Sears product engineer

is expected to have a thorough knowledge of their product lines—the

current technology, future trends, and customer usage in general.

Furthermore, he will usiially have had input in the product development

stage, so that he is familiar with important design changes.

Also, he is aware of the many kinds of trade-off decisions that have to

be made in bringing a product to market. For example, how it is necessary at times to back off from some choices that might improve durability, because they would add unduly to cost, or reduce convenience, or interfere with basic function. Similarly, he is av^are of the great

impact of variability, in product characteristics and in type of use. Furthermore, he is extremely sensitive to the interaction of engineering design with the manufacturing facilities that will be involved.

As an illustration, recently one of our senior product engineers

reviewed the results of tests on an important, new product. The

test results looked good. Many of the components and materials were relatively well-known, and proven in use. Yet, when the product engineer applied his experience to analysis of the engineering design, he

recognized that the design was such that it required extreme care and

precision in manufacturing, to prevent reliability problems and heavy

service costs. On that basis, the laboratory recommended that the

design be greatly modified before production, which was done.

CONFORMANCE TESTING :

As far as testing is concerned, in most cases we are very much aware

that we are not duplicating consumer use over an extended period very

well. In that connection, before v;e consider some details of testing

of particular products, let us look at a total matrix of testing for

long-range consumer satisfaction.

In analyzing the elements of product durability, we find it necessary

to think In terms of quality of design versus quality of conformance to

design intent, as manufactured. A Cadillac is engineered for longer

life through quality of design than a Chevrolet, for example—but the

conformance to design intent m.ay be poor on some individual Cadillacs.

Similarly, there is an extensive list of characteristics that affect

product life, including those characteristics that determine consumer

satisfaction after extended use. The current state of the quality

control art copes much more comfortably with the former, than with

the latter.

58
If we put these aspects in matrix form, it looks like this:

Quality of Design Conformance Quality

Performance

As Received

Laboratory tests can define reasonably

vrell.

Inspection, Quality

Assurance testing

can define fairly

well.

Performance

After Use

Special tests have

some predictive

value.

Currently cannot

be defined well at

reasonable cost.

The lower right hand entry points out the fact that a manufacturer cannot be certain vrhich of (or vrhether) the many things he did differently

today will affect the long-range characteristics of the product. Fortunately, vrith reasonable care, serious problems from this cause can be minimized.

DURABILITY TEST PROGRAM EXAMPLES :

In specific product test programs, let us begin with mattresses. By

experience, we know that while we do not duplicate consumer use exactly,

if the mattress passes certain laboratory tests, it is likely to meet

customer expectations. Our awareness of sales results and consumer

complaints gives a reasonable base of such judgements on product durability and life.

By the use of a heavy roller which provides cycles of heavy loading and

unloading of the mattress, followed by visual inspection after teardown,

we think v^e get an adequate handle on durability. We recognize that the

test does not completely account for aging of the foam, nor does it take

into account the effect of specific "high-pressure points" (knees and

elbows), which might require more elaborate test apparatus.

Similarly, in testing chairs, we emphasize structural integrity in the

test program. We recognize structural tests do not take into account

such factors as the aging of the plastics, the corrosion of metal,

abrasion effects, nor permanent "packing do^m" of the cushioning material. Special tests are run for some of these aspects of long-range

performance, whenever construction changes are judged likely to affect

durability in an unpredictable way.

There are some synergistic long-range effects that no amount of laboratory aging tests can either duplicate or predict effectively. In other

words, we must use engineering judgment on the degree to which material

aging and wear will affect functional performance and constimer satisfaction.

59
In carpeting, we use a practical test for durability which involves

having it walked on hundreds of thousands of times in a high traffic

hallway. This is the best durability test we know, but still may be in

need of improvement.

For just one example, under this kind of test carpeting gets soiled

more severely, so that cleanabillty evaluation is complicated by

"deeper" cycles of soiling and cleaning.

In luggage testing, we test individually for many product characteristics that may change in different ways, and interact unpredicatably

over time. For example, we use drop tests, ttmble tests, handle-lift

tests and abrasion tests, in addition to many others. Again, we must

concede that the results must be subjected to highly knowledgeable

interpretation, and have not always been correlated well with real-life

results.

For further examples of complications in predicting product life, con- sider an automatic washing machine. Suppose we have data on the life

of all components and sub-assemblies, under some "typical" conditions

of use.

We should start our process by defining, or assuming, the range of

environmental conditions and type of use. In this case, we can visualize that one unit of a certain model might conceivably be purchased to

clean the washing rags in a car-wash situation. Another might be purchased by a retired couple. The number of hours use, the loading, and

the environment (dry/cool v.s. steamy/wet) would be extremely different

for the two.

Any specific figure, therefore, v7ould be quite arbitrary, unless the

usage factor would be well understood and the degree of variability

defined. Suppose any one of us were to try to predict how long a washing machine would last in our home, given the following information:

"When used under conditions of severe heat and humidity, and with heavy

loading this machine will last three years. It will last 30 years under

favorable environmental conditions and light duty."

Would you be able to tell where your particular family usage would fit

into this product range?

To complicate the picture still further, consumer products are evolving

rapidly in many ways, particularly in the use of new materials and new

applications of electronics. This introduction of unknown elements

greatly influences the reliability. Similarly, in many cases changes

in purchased components and materials are not accompanied by engineering

information on the likely effect of the change on product durability.

60
We are not suggesting that it is necessary or desirable to put product

design in "stop-motion" while we develop highly precise tests and analyses. We do want to emphasize the need for investigation of likely

side consequences of changes.

CONSUMER USE OF DURA.BILITY INFORMATION :

One of the underexplored fields of consumer product marketing and technology is consumer use of information.

For just one example, any life rating is likely to be confused with a guarantee. This is further complicated by the FTC emerging policies

and rules on implied warranties.

Another danger is that once consumers develop reliance on a life rating,

there will be strong pressures on manufacturers to get into a "horsepower race" on claims for product life. This will lead to problems on how claims should be verified—which brings us back to the starting

gate!

Similarly, if we look at the history of warranties and guarantees

effectiveness, lifetime guarantees have had mixed results. At times,

it has made a dramatic difference, particularly with replacement items,

such as automobile mufflers. VThen applied to characteristics that are

not high on consumers' priorities, it is likely to be ignored.

In children's play clothes, we have found that mothers rate durability

extremely high. In fact, they will trade off quite a bit of comfort

and appearance for durability.

Extended life guarantee was successful in the introduction of the steel

radial tire, where the increase in tire life was dramatic, and the miles

per dollar represented increased value.

On the other hand, both automobiles and television receivers have had

some unhappy results with extended life guarantees.

Part of our concerns include consumer awareness of the true economic

impact, or efforts to increase product life. Someone has to pay the

bill. There does not seem to be sufficient consumer awareness that

most of the increases in desirable characteristics, such as product

life, safety, etc., involve complex, trade-off decisions involving

other desirable characteristics.

For example, the FTC requires that lamp bulbs be rated as to lumens of

light output, and hours of life. Both illumination needs and life

expectations vary dramatically with operating conditions, such as applied voltage and visual task. How can the typical consumer be

expected to evaluate "long life" bulbs versus "standard" bulbs—partic61
ularly parameters of power consumption, light output and price. If

you had to replace a bulb in a relatively inaccessible hall stairway

light, how would you choose among these three alternatives:

Wattage Lumens Hours life Price

60 870 1000 30 c

60 770 (less light) 2500 (long life) 75c

75 (more power cost) 1170 (more light) 750 (shorter life) 35 c

Would you make the same choice for one of the bulbs in the dining room

chandelier? Or don't you care about the labels on lamp bulbs?

FUTURE DIRECTIONS:

In previous parts of this paper, we have emphasized the complications

and difficulties in product life testing and durability prediction.

This was intended to help prevent effort wasted by underestimating

the complexity of the task.

However, we feel optimistic about progress that can be made. In that

spirit, we are suggesting some specific directions for government,

industry, and academe' to consider and explore.

These, then, are suggestions to the attendees at this conference:

First: CHALLENGE TO GOVERNMENT:

Our most important suggestion is to recognize the enoirmous potential

in the directions of motivating industry efforts, and in informing

the public. We believe that attempts to influence, regulate, or predetermine fine details of technical action are unrewarding. As

Congress expressed in the legislative history of the Consumer Product

Safety Act, technical knowledge about consumer products resides

primarily among manufacturers, and effective action requires good

utilization of that knowledge.

This motivation effort will require careful thought and planning, in

the absence of regulatory power—and we think the history of the CPSC

shows how counter-productive regulatory power can be when full

utilization of the knowledge of producers is disregarded.

We suggest that another useful activity for government is to encourage

applied research in this field. The National Science Foundation's RANN

Program has made an excellent beginning, although there may be need

to shift emphasis towards specific applied research. Other programs

are needed.

62
Next, government could inform and educate consumers in appropriate

ways. For example, the National Bureau of Standards has had enormous credibility with the public that is both a great opportunity and a sobering responsibility.

The Sentry/Ilarris Report seems to indicate that the public favors a government technical function to represent their interest in product

safety. As we have already mentioned, we think the history of the

CPSC shows that regulation has not proven to be an effective means

for such representation. We are convinced, however, that information

and education does have an enormous potential for the future, both

in product safety and product durability.

Along this line, certain research results provide som.e clues. For

example, there is a trend for more disclosure of important kinds

of information. The public has indicated that it favors an approach

which is straight- forward and informative. Our research in catalog

copy indicates that such directness is appreciated and favored by

our customers.

There will be some honest disagreement how extensively and in what

depth disclosure should be done, but this, too, is amenable to

research. Similarly, consumer information and education might help

with some market considerations. Research shows that only one out

of three consumers for big ticket consumer items repurchases the same brand if he is in the market again. This lack of brand loyalty

for expensive items suggests product satisfaction alone won't bring

back a customer. Advertising is necessary to keep the product in

mind. The report speculates that possible reasons are high emotional

and personal involvement in the purchase of expensive items, the

search for information, and the option to delay purchase.

This research has real-world implications concerning product life

improvement. How can the public be made aware that rewarding brands

for product satisfaction can help to increase the level of general

satisfaction, whereas a low correlation between product satisfaction

and rewards, discourages manufacturers' efforts?

One way that the government can provide extremely useful services

would be to set up an information center for consumer product life

data.

One would hope that we all can learn from the disappointing experience

of the CPSC with the use of NEISS data. For one thing, we would

admonish against proceeding too far and too fast with an over-idealized

system which might be suitable for an aerospace program but does not

face the realities of consumer marketing. On the other hand, we are extremely enthusiastic about the potential contribution of such a data

center ±f_ it is carefully planned, started on a modest scale and

constantly improved through feedback of actual results.

65
CtlALLElTGE TO ITTOUSTRY:

Perhaps one of the most important suggestions to industry in this

field is to take a longer range view, recognizing the changing "rules

of the game". For example, the full impact of life-cycle-cost

awareness will apply in the not too distant future to products

made today.

In other words, while there has been an emphasis on meeting consumer wants in the marketplace, it has been based primarily on sales. It is

probably time to add an awareness of delayed consumer dissatisfaction,

such as from the service costs. In other words, industry needs to

recognize the need for high quality of engineering for customer satisfaction over the full life cycle of the product.

Furthermore, industry should be aware that it is not necessarily more expensive to have an excellent quality of engineering in the design of consumer products. In fact, with the help of government and the academic world, it can be very rewarding in the future to be able to

design for more reliable products which are easier to service.

CHiVXLENGE TO ACADEME':

The academic community can contribute greatly by attempting to develop

techniques that allov? better application of current knowledge to con- sumer products, in a marketing-realistic way. For example, there needs

to be better research techniques on consumers' usage of products. Some

valuable work has been done, but does not seem to have received the

attention it deserves. Frank Gryna' s pioneering use of surveys paid

careful attention to front end analysis, in order to determine the

"vital few" factors that should be targeted for research. This technique should be used far more extensively, and improved on by use.

Similarly, there needs to be research on the way prodxicts respond to

extremes of use. Some products are "forgiving" of extremes of use. Others are quite unforgiving, and even quite punishing, of any departure

from the type of use built into the design assum.ptions.

And next, we suggest research into improved techniques of technology

transfer, techniques which take a realistic view of consumers, con- sumer products, and technology. For example, there is a misconception

that a great deal of aerospace "high technology" can be transferred

directly to consumer product technology. There are some, but not as many as there would be, if those engaged in developing the art of technology transfer made the effort to better understand the interaction

of technology with marketing considerations.

6k
Lastly, the academic world needs to develop better techniques to train

engineers in the art of mathematical modeling of engineering design.

Individual product samples submitted for laboratory testing may not be

completely representative of total production, and may even be carefully

produced prototypes. There is a need for much research work, before we

can predict the quality of engineering design after use. Mathematical

modeling will also require data related to the statistical distribution

of important product characteristics. Advantages will not suffice.

We should also emphasize that this modeling must be balanced by good

judgment and an excellent grasp of how basic assumptions have to be

used for an optimum design. There is a danger of "paralysis by analysis" which all of us concerned with consumer products must keep in

mind. In other words, the challenge is to balance the amount of analytical work against the need to meet reasonable deadlines. This

requires the ability to know when it is time to stop gathering and analyzing data and make judgment decisions.

65
HYDRAULIC PUMP CONTAMINANT LIFE EVALUATION

Dr. L E. Bensch

Fluid Power Research Center

Oklahoma State University

Stillwater, Oklahoma 74074

Abstract: The hydraulic pump is one of the most critical components in any fluid

power system. It is also generally thought to be one of the most sensitive to abrasive wear. The Fluid Power Research Center has been investigating accelerated test methods

for evaluating pump contaminant sensitivity for several years. An associated wear theory

has also been developed for predicting long-range pump contaminant service life based

upon these accelerated tests and field operating conditions. During the past two to three

years, a number of tests have been performed to verify the contaminant life predictions

by conducting extended life tests under controlled contaminant environments. Tests were

conducted over a broad range of service lives, ranging from 22 to 1430 hours utilizing

both gear and piston pumps.

This paper presents the results of this extensive research investigation, including details of

the life evaluation methods. Also included are brief descriptions of the accelerated test methods and contaminant life prediction techniques. The paper discusses the expected

accuracy of the life predictions revealed by the test results.

Key words: Contaminant wear; hydraulic pump wear; accelerated wear testing; service

life, abrasive wear, contaminant tolerance

Introduction: In any fluid power system, there are a number of individual components

which affect the performance as well as the resultant reliability of the system. The hydraulic pump is generally considered one of the most important components because it provides the hydraulic power necessary to operate the remaining components. It has been

recognized for a number of years that hydraulic components (in particular, the pump)

are sensitive to contaminant-induced wear. Most hydraulic component manufacturers

specify that their products should be protected by filtration; however, they have not had

any proven method upon which to base these filter specifications.

Because of the deleterious effects of contamination upon hydraulic components, an entire area of investigation commonly called contamination control has developed. The Fluid

Power Research Center (FPRC) has been active in this area for the past two decades, and

a number of associated theories and test methods have resulted for most fluid power components. The accelerated pump contaminant sensitivity test method is one of the most

advanced of the techniques developed and has been adopted as a standard by the National

Fluid Power Association [1]. An associated contaminant wear theory was also developed

66
[2] for interpreting the accelerated test data with respect to extended life in field environments. Until recently, the wear theory had not been rigorously verified; however, the

results have been successfully applied in field applications.

During the past two years, the FPRC has been involved in a program under the sponsorship

of the U.S. Army MERADCOM which has resulted in a more complete verification of the wear theories. A number of extended life tests were conducted under controlled contamination conditions, and comparisons were made of the results of these tests and predictions made from accelerated tests conducted on identical pumps. The following sections

of this paper present a brief description of the accelerated test method and the wear

theory. Then, the test technique and results of the extended life tests are presented.

Finally, comparisons are made of the actual and predicted performance.

Accelerated contaminant sensitivity test: In order to estimate the length of time a given

pump will operate in a given contaminated environment, it is necessary to conduct testing

under contaminated conditions. When considering the effects of contaminant wear on a hydraulic pump, the output flow rate is generally utilized as the performance appraisal

parameter. The pump life is, thus, determined by the operating time during which the

output flow rate is above some specified level. When flow rate is used as the appraisal

parameter, the other operating conditions — speed, pressure, and temperature — are held

at a constant value. The accelerated pump test procedure [1], originally formalized at the FPRC under U.S. Army MERADCOM sponsorship [3], utilizes these concepts for

evaluating the pump contaminant sensitivity.

The accelerated test method is designed to progressively expose a pump to increasing sizes

of contaminant while monitoring the output flow rate. The test facility utilized is illus- trated in Fig. 1. To enhance both the repeatability and reproducibility of the test, the

volume of the test fluid in the circuit is maintained at a constant value equal to onefourth the rated volume flow of the pump per minute. The control or clean-up filters utilized reduce the contamination level of the fluid between injections to less than 10

mg/litre. The procedure specifies the use of single-cut (e.g., 0-5, 0-10, 0-20, 0-80

micrometres) contaminant classified from AC Fine Test Dust base stock. The contamination level maintained in the test system during each injection is 300 mg/litre. The test method calls for the test fluid to be selected by the pump manufacturer; however, most

tests at the FPRC are conducted with Mil-L-2104, Grade 10, hydraulic fluid at 65.5°C.

After an extensive break-in period, the actual contaminant sensitivity test is initiated by

injecting a slurry of 0-5 micrometre test dust to create a 300 mg/litre system level. The

pump is then run at rated conditions and output flow rate is monitored. After the flow

rate has stabilized for ten minutes or a total of 30 minutes has elapsed (whichever occurs

first), the contaminant is filtered from the system and the final flow rate for that injection is measured and recorded. Subsequent injections of 0-10, 0-20, 0-80 micrometres

contaminant are then made, and the final flow rate is recorded after each injection. The

test is terminated after the 0-80 micrometre injection or after the flow rate has dropped

to less than 70% of its original value.

67
Data analysis and life prediction: In order to provide an interpretation of the results of a contaminant sensitivity test in terms compatible with filter specifications or allowable

contamination levels, a contaminant wear theory has been proposed [2]. The entire

development of the model is presented in Ref. [2] and will not be repeated in detail here.

INJECTION CHAMBER

[<>4 AIR SUPPLY

I SAMPLE

TEST PUMP ^

VALVE

INJECTION CHAMBER

CONTROL

FILTER

Fig. 1. Test Circuit for Pump Contaminant Sensitivity Test.

The contaminant sensitivity model is based upon the contention that, for every critical size particle that passes through or is exposed to the pump, there is a finite amount of

damage which reduces the output flow of the pump. Thus, the rate that the flow degrades

(dQ/dt) depends upon the sensitivity (Sj) of the pump at size interval (i) and the rate (dNj/dt) at which particles of size interval (i) are exposed to the pump. This relationship

is expressed by the following equation:

68
dQ/dt = - Sj (dNj/dt) (1)

By considering the facts that: (1) the sensitivity coefficient is a function of both particle

size and concentration, and (2) the contaminant exposure is not only related to particle

concentration but also to the flow rate of the pump, an expression for flow degradation

for a given particle size can be obtained as follows:

where: Qq = initial flow rate a = contaminant wear coefficient

nQ = initial particle concentration

T = particle destruction time constant

It should be pointed out that the contaminant wear coefficient, a, is constant for a given

pump and operating conditions but varies with particle size. The influence of each particle

size range is evaluated by a single injection of contaminant which is continuously circulated during the test. Test results have shown that the contaminant (or at least its ability to cause wear) is destroyed during a test, and such destruction must be considered in the

mathematical analysis. The contaminant destruction is accounted for in Eq. (2) by the

use of the time constant, r.

In using the results of a contaminant sensitivity test for estimating field operating characteristics, it is assumed that, under field conditions, contaminant is continually being ingressed or generated and subsequently filtered from the system. This continuous interchange

of new particles results in a relatively constant contamination level, n, determined by the

ingression and filtering characteristics, and Eq. (2) for field operation becomes:

Q = Qoe-«"^t (3)

Solving Eq. (3) for time and allowing the full particle size distribution to be reflected

gives the following reference contaminant life equation:

-Cn(Qp/Qo)

-i (4)

max

2

i = 1

«i "i

where Qq and Qp are, respectively, the initial and final flow rates and T is the contaminant service life. The onj's are the reference contaminant wear coefficients evaluated from

the laboratory test, and the nj's are the particle concentrations for the various size inter- vals which describe the particle size distribution of the field fluid.

69
The contaminant life equation can be utilized to calculate the pump contaminant life for

any given particle size distribution. In order to allow system filters to be selected for the

protection of a given pump, it is desirable to determine the maximum particle size distribu

tions which would result in a specific contaminant life. In order to provide this informiation, the contaminant tolerance profile was developed [2]. The calculation of the profile

requires the iterative use of Eq. (4). Ideally, any contaminant particle size distribution

which is below the contaminant tolerance profile would result in a service life equal to or

greater than the reference life associated with the profile.

Contaminant life verification testing: In order to verify the accelerated sensitivity test and the accuracy of the wear relationships for predicting field service life, a number of

extended wear tests were conducted. The procedure utilized for these contaminant life tests consisted of the following basic steps: (1) Conduct contaminant sensitivity test on

subject pump; (2) calculate contaminant tolerance profile for pump; (3) determine contam

ination level to result in desired life; (4) select proper filter and ingression rate to produce

required contamination level; (5) conduct life test; (6) compare results of life test to pre- diction.

The test circuit utilized for most of the test work is illustrated in the schematic shown in Fig. 2. The pump test system was a recirculating loop, consisting of a load valve, flowmeter, clean-up filter, and automatic temperature controller. The contaminant conditioning circuit included a 26 8pm pump and "conditioning filter." The two systems used a common fluid reservoir with a volume of approximately 40 litres. A separate recirculating

CLEAN-UP

FILTER

CONTAMINANT CONTAMINANT PUMP

INJECTION CONDITIONING TEST

SYSTEM SYSTEM SYSTEM

Fig. 2. Pump Contaminant Life Test Circuit.

system continuously injected fresh AC Fine Test Dust contaminant into the conditioning

circuit upsteam of the filter. Automatic controls and shut-down features controlled pres- sure and temperature and provided for shut-down due to low or high pressure, high

TO
temperature, low fluid level, or high filter differential pressure. Periodic measurements

of output flow rate were made during testing, and fluid samples were extracted for particle

count analysis. The test configuration was selected to result in longer filter life while

retaining an approximation to a realistic field system. The pumps used for testing were

contributed by pump manufacturers and included both gear and piston pumps. All tests were conducted at 1800 rpm, 138 bars (2000 psi) and 65.5°C, using Mil-L-2104, Grade 10,

hydraulic fluid. A total of nine tests were completed on four different pump models with

rated flows in the 60-80 £pm range.

Reference [4] includes a complete summary of the verification test results. Therefore,

only the condensed highlights are presented here. Typical contamination levels encountered in tests on pump numbers 243B and 243E are illustrated in Fig. 3. The number refers to a specific pump model, and the letter suffix signifies a particular pump from that lot. A 1000-hour contaminant tolerance profile for Pump 243 is also shown in Fig. 3. The

contamination level exposed to Pump 243B was well above the 1000-hour profile, while

the level for Pump 243E was approximately tangent to the profile curve. The flow degradation curves calculated for Pumps 243B and 243E are shown in Figs. 4 and 5. The actual

flow degradation values (actual flow divided by initial flow) are also shown on Figs. 3 and

4 for direct comparison to the calculated values. In both instances, the results are exceptionally close. Similar curves were obtained for the remaining pumps, but space limitations

do not allow presentation of all curves in this paper. The calculated flow degradation

values were actually determined in a stepwise manner versus time. Because the particle

count levels changed somewhat during testing, the actual counts were used in the calculations, along with the pump contaminant wear coefficients determined from a standard

pump contaminant test. The particle counts used for a given time period were an average

of the counts obtained at the beginning and end of the time period.

Comparison of actual and predicted life: A convenient method to verify the accuracy of

the contaminant wear theory (besides a direct comparison of actual and calculated flow

degradation curves) is to compare the actual time required for designated flow degradation

to the calculated time for the same degradation. Table 1 presents the results of life comparisons to a flow degradation value of 0.800, or 20% degradation. For situations in which

the flow did not degrade below 80% of the initial value, the final flow rate at the conclusion of the test was used as the comparison point, and a life calculation to that flow rate was made. The life for Pump 242D was not calculated because the degradations were so minute (0.5% maximum) that large errors can result in life estimations. The flow degradation ratio at the conclusion of the test on Pump 242D (0.995) was actually less than the

calculated value, but only by a factor of 0.001, or 0.1%. Because contamination levels were not known past the test termination of 163.8 hours, the estimated life past that

point could not be determined.

The average ratio of actual to calculated life for the eight pumps considered in Table 1 was 1.58, with a standard deviation of 0.32. This ratio implies that the average pump life

is 1.58 times greater than that predicted using the contaminant wear theory. In every

instance, except pump 242D, the actual life was in excess of the calculated value. Figure 6

71
PARTICLE SIZE , micromefers

Fig. 3. O)ntamination Levels for Pump 243 Life Tests.

is a graphical representation of the life ratios listed in Table 1. A histogram was construct- ed using ranges of life ratio equal to 0.25. The "normal" curve superimposed on the histogram emphasizes the mean life ratio of 1.58.

72
TIME , HOURS

Fig. 4. Comparison of Actual and Calculated Fig. 5. Comparison of Actual and Calculated

E)egradation for Pump 243B. Degradation for Pump 243E.

Conclusions: A total of nine life tests were conducted on various hydraulic pumps,

and the data are summarized in Table 1. The tests on both gear and piston pumps ranged

in length from approximately 12 hours to 1,431 hours. The average ratio of actual to

calculated pump life was 1.58, with a standard deviation of 0.32 or 20% of the mean. The low standard deviation implies that the life calculations are consistent but deviate

from the actual by an average factor of 1.58. In all but one instance, the actual life was

in excess of the calculated value; and, in this case, the actual and calculated flow degradations differed by a maximum of only 0.2%. Because of the conservative nature of the

estimations, the contaminant wear theory and interpretations can be used with confidence

directly, as presented in Ref. [2]

.

The primary reason for the discrepancy between the actual and calculated lives is believed to be caused by the omission of "particle destruction" characteristics in the field wear

expressions. In reality, the contaminant is not totally destroyed, but its abrasive characteristics are probably altered (sharp edges rounded, etc.) by the wear process. Current

studies are being conducted to gain actual evidence to support this contention. Preliminary photographs taken through a scanning electron microscope have revealed that many of

the sharp edges on the silica particles are rounded after several minutes of exposure to the

73

i '1
TABLE 1. ACTUAL VERSUS CALCULATED PUMP LIFE SUMMARY.

PUMP

1 . D.

PUMP

TYPE

FLOW DEGRADAT ION

RATIO

Actual Life (hours)

Calculated

Life (hours)

Ratio

Actual / Calc.

242D Pi ston 0.995 163.8 XX XX

242C Piston 0.840 276.0 158.1 1 .75

243B Piston 0.800 52.2 50.6 1 .03

243E Piston 0.903 646.

1

396.1 1 .63

247D Gear 0.800 11.7 8.0 1 .46

247E Gear 0.800 385.3 273.4 1 .41

241C Gear 0.990 1430.6 852.2 1 .68

223A Gear 0.800 108.0 72.0 1 .50

252 Gear 0.800 123.0 57.0 2.16

Average Ratio (actual/calculated life) = 1.58

Standard Deviation = 0.32

AVERAGE = I 58

SID. DEV. = 0.32

<

I /

/

/

/

/

/

\

ACTUAL DATA

\

\ "TYPICAL NORMAL" ^

CURVE

\

\

I RATIO OF ACTUAL TO CALCULATED LIFE

Fig. 6. Actual Vs. Calculated Pump Life Characteristics.
wear process. A detailed report on the findings of this study will be available in the near

future. It can certainly be concluded from these studies that it is necessary to continuously inject fresh contaminant in any realistic field-simulated experiments.

Although the contaminant wear theory is not totally accurate without the inclusion of

terms describing "particle destruction" (This would include filter and ingression characteristics.), it appears to be sufficiently accurate for routine application. Based on the data

shown, proper application of the contaminant wear theory results in sufficient protection

for a hydraulic pump and assures adequate contaminant service life.

Acknowledgments: The author wishes to express his appreciation to the U.S. Army

MERADCOM for sponsorship of this project, to the pump manufacturers who contributed

the test pumps, and to Pall Corporation for their assistance in performing the preliminary

scanning electron microscope analyses of the silica contaminant during the various wear

stages.

References:

1. "Method of Establishing the Flow Degradation of Hydraulic Fluid Power Pumps

When Exposed to Particulate Contaminant," NFPA Recommended Standard T3.9.18-

1976, National Fluid Power Association, Milwaukee, Wisconsin, 1976.

2. Bensch, L. E., and E. C. Fitch, "A New Theory for the Contaminant Sensitivity of

Fluid Power Pumps," Paper No. P72-CC-6, Sixth Annual Fluid Power Research

Conference, Oklahoma State University, Stillwater, Oklahoma, October 1972.

3. "Hydraulic Specification (Phase I)," Final Report to U.S. Army MERADCOM,

Contract No. DAAK02-70-C-0093, Oklahoma State University, Stillwater, Oklahoma,

November 1970.

4. "Pump Contaminant Tolerance Verification," Section VI, MERADCOM/OSU

Hydraulic System Reliability Program, Annual Report, Contract No. DAAK02-75-C0137, Oklahoma State University, Stillwater, Oklahoma, February 1977.

75
CONTROL OF DESIGN QUALITY

Andrew W. Dorney

American Standard Inc.

P. 0. Box 2003

New Brunswick, NJ 08903

Abstract: Manufacturers often find that even though their products

have been processed utilizing stringent manufacturing controls, their

customers are still receiving and reporting poor quality. The function

of an independent Reliability Section is discussed covering its re- lationship with Design, Manufacturing and Quality Control. This

section does not fully utilize the statistical aspects of Reliability,

but controls the quality of the design as required, by determining the

end use of the product and testing accordingly. Responsibility for the

design and manufacturing in the various stages is discussed as is the

testing and decision making associated with it. A typical consumer

product is followed from Marketing concept through acceptance for shipment to the customer.

Key words: Product failure; product testing; quality control; quality

of design; reliability.

Why is it - we never take the time to do the job right, but we always

take the time to do it over? As manufacturers, we have all been made

painfully aware of a shortcoming in our product by the most important

inspector, the customer. Somehow, the press of meeting deadlines, the

potential sales and profits, and the desire to just get the task com- pleted, results in taking short cuts, risks, and in many cases, making

errors of commission and, more importantly, of omission, causing the

production of a poor quality product.

When the customer informs us that the product has failed, our first

inclination is to be defensive, raising the usual questions. Is the

product really unsatisfactory? Is the customer being too fussy? Is it

only one lot, or one area of the country? Has anyone seen any bad ones?

Should we stop production and shipment? Most times, the product is_

defective upon inspection and so the wheels of correction activity are

set in motion and the job is done over and, possibly over again, since

sometimes the corrective actions are not adequate and more problems are generated. There is not only added engineering, manufacturing, and

inspection expense, but expenses for returning and reworking defective

product, and shipping new product, but also damage to our image as a reputable manufacturer. In addition, faulty product may pose a potential consumer hazard, and if this is the case, then we must follow

76
the procedures of the Consumer Product Safety Act and report the potential hazard to the Consumer Product Safety Commission. They must

be furnished information on the extent of the problem, what is being

done to correct and/or recall defective product, and what corrective

measures are being taken to assure no hazard on future product. How

much better it would have been to utilize this time, effort and money

to do the job right!

Doing the job right - what is the job? The job is to design and manufacture a quality product. This entails controlling the quality of

the design and controlling the quality of manufacture. We are all

wel 1 -acquainted with controlling the quality of manufacture; this is our Quality Control Program, with the assigned task of making the

product to print or, in other words, the Quality of Conformance. It

does not do any good, however, to have an excellent Quality Control

Program without having a proven design. This then is the area of

prime importance, the control of the quality of the design.

Reliability, the quality of the design, is defined as assuring that

the product will perform acceptably for the planned life in the intended environment. The primary assignment of this responsibility

must be to an organization, generally called Reliability, which is a completely independent entity from manufacturing, design engineering

or quality control. It must have the basic authority to approve or reject designs, or design changes, wholly and solely based upon the

results of their testing and investigations. Experience has shown

that rationalization of test results by well-meaning management eliminates the possibility of continual good judgment and weakens the future activities undertaken by this section. Lack of support by management, especially in negative decisions, will soon render the entire

function useless; however, enthusiastic backing through a few new products or design changes, should prove its effectiveness.

At American-Standard, Reliability is part of a multi-discipline department which supplies technical expertise to our manufacturing

organization which no plant or group of plants could economically

justify. The primary responsibility of this Engineering Services

Department is to assure that all newly designed or redesigned product

will perform as intended and/or product limitations are recognized

beforehand. In order to do this, a system has been set-up whereby

Engineering, Manufacturing, Marketing and Reliability collectively co- ordinate design and production activity; however. Reliability, having

the responsibility for performance and testing, is generally the con- trolling factor.

The system as set-up is a formal one requiring each group to perform

and report on functions associated with their area. For example, when

engineering has completed their design on new product, they must, in

conjunction with manufacturing, confirm that they are able to produce

the design successfully, at the cost price agreed upon, within the

77
appropriate time interval, and with the assigned inventory. Marketing

responsibility is to confirm that they will realize the planned selling

price and volumes. On redesigns, the situation is similar; however, in

requesting a design change, the reason and cost must be specified when

the request is made. The request is submitted to each department, in

turn, and all must approve before the change can be implemented. When

the change requires a print revision, al

1

signatures must appear on the

request document before this is done. No production may take place

without a revised print; therefore, in cases where testing and further

approvals are necessary all parties must sign the document and it must

be stamped with the notification that the product may be produced but

may not be shipped prior to official approval.

Design changes are generally undertaken for three basic reasons, cor- rection of field problems, substitution of materials, or cost reductions. The intent and necessity of the first two is apparent but the

third, while important, often results in problems. The control of

cost reduction changes must be extremely stringent, since many of them

result not only in cost reduction, but in product degradation, by re- ducing the effectiveness of the product in one way or another.

Even though Reliability has the authority to approve designs or design

changes, based upon its own activities, it must avail itself of all of

the other disciplines, as appropriate. Questions regarding installation and compatibility are referred to Roughing-In, review of aesthetics are referred to Industrial Design, material evaluations and approval for use are assigned to Materials, regulatory agency and appropriate code and standard conformance is checked by Codes, and adequate packaging is designed and/or tested by Packaging. Even though

all these disciplines are extremely competent and the decisions made

in each area are technically sound, the ultimate value of the effort

is directly proportional to the calibre of the person responsible for

operation of the Reliability Section. This position can make or break

the entire design control activity, since it many times finds that designs are not acceptable and therefore not suitable for use. The

easily badgered or non-confident individual, who is unwilling to face

higher levels of management, with unpopular decisions, will render the

entire program valueless, and it will be nothing more than a paperwork

exercise. The make-up of the Reliability Section is extremely important. It must have the fundamental disciplines available, such as, me- chanical and electrical engineering, and statistical expertise, but by

far the most critical item, an indepth, exploring, sensitive, investigative, practical approach to product design evaluation. When planning

the evaluation, not only the normal functioning and environmental ex- posure of the product must be covered, but also the foreseeable possibility of misuse and overload characteristics, including damage. It is

important here that past experience be utilized in setting up design

evaluation tests or procedures, but it must be remembered that past

results, even in similar tests or products, should not color the

thinking or analysis of the problem at hand.

78
Initiation of the control of design occurs when Marketing submits a re- quest to have a product designed. They spell out the important characteristics of the product, with material limitations, if any, the comparable products on the market, whether in-house or competitors, and the

target selling price. The design engineer, with the parameters defined,

formulates his ideas into sketches and functional models. This phase

of development then proceeds to some performance testing and perhaps

some minimal life testing. The depth of testing required to qualify a design is obviously a function of not only its complexity but the en- vironmental conditions to which it will be exposed, in addition to all

the normal performance requirements. A careful assessment of the performance test results, both as they affect basic design and materials

selection, can save many hours of duplicated testing later on, so it

is important that this testing be as rigorous as possible.

The importance of standard tests and the requirement of full compliance

is critical to design control. Occasionally, it is necessary to field

test a product to further insure a design's effectiveness, since all

the functional and environmental variables cannot be reproduced to the

extent necessary within a laboratory. For the most part any critical

characteristic associated with time can only be estimated, and only

actual time in use will provide the necessary answers. It is imperative the field testing be kept to a minimum and, therefore, a very detailed plan regarding quantities, distribution, and follow-up, must be

made. A comprehensive list of defects must be made defining a design

failure and, any failures associated with the design constitutes re- jection of the design.

It is important to note, at this time, that a test plan covers both

standard and uniquely developed tests formulated to check for design

capability. They are documented procedures prescribing detailed

methods, equipment and conditions, including time or usage characteristics; however, they do not include acceptance criteria since it is

expected that no design attributable failures are allowed. All designs

and redesigns in which test plans require the use of the documented

procedures are done under the same conditions and are required to pass

them successfully. Unique tests are generally developed in response

to design changes associated with material usage; for example, the

compatibility of rubber and plastics in close contact, to assure that

migration from the rubber does not cause deterioration of the plastic.

Also important in plastic applications is the effect of household

cleaners on the parts, as installed. Many plastic materials under

stress, are attacked by these cleaners, resulting in cracking or other

physical changes, such as staining.

Responsibility for all testing activity is assigned to Reliability;

however, in the development phase, the control of the intent and

amount of testing is given to the Design Engineer. He stipulates

tests, data, and conditions to be utilized and may at any time,

depending upon the results obtained, change direction. When the design

79
engineer is satisfied with the performance of the product, the initial

sketches and specifications are converted to complete engineering

drawings. At this point. Reliability reviews the drawings and coupled

with their previous exposure in the development testing, formulates a test plan to determine acceptability of the design.

This Design Review also covers the evaluation of materials used in each

component. The specification for each material, coupled with its use,

is checked for completeness; that is, will the specification provide

material selection, most notably in rubber and plastics, in how to determine and define their selection. Often formulations are given for

rubber and, in many cases, the tradenames of plastic material are utilized. Unfortunately, once the selection has been made on this

basis, the responsibility of the performance of the materials is with

the purchaser. To preclude incorrect or marginal material selection,

a system has been developed, whereby performance characteristics are specified, utilizing ASTM tests for evaluation. While this is a step

in the right direction, it too is still deficient in that the tests

performed are on laboratory produced configurations rather than on the

part itself; however, these tests coupled with actual performance

tests of the product, provide a great deal of protection.

One of the shortcomings in testing, which is very difficult to overcome, is the changes which occur due to aging. The passage of time

can be approximated by certain accelerating conditions; however, there

is no real substitute for actual time in service. If there is any

question as to the validity of the results, it may be necessary to

conduct a field test to confirm the results obtained. Field testing

may be conducted in one of two ways; the low volume, highly, detailed

test, or utilization of the "shotgun" approach with an extremely large

quantity of production. Results in the first case are dependent on the performance and close scrutiny of each and every piece installed

in a known location, while the second approach is more easily evaluated

by waiting for complaints from the field, if any. The field test must

be documented as completely as possible when new materials or old ma- terials in new applications are being tested, as it may be necessary

to use this documented data to convince Municipal, State, or Federal

Administrative Authorities to allow the product to be used.

After the development phase and subsequent Design Review, prototype

parts are produced and assembled using manufacturing tools, conditions

and methods, whenever possible, utilizing temporary tooling only as necessary. The Manufacturing Department is responsible for assuring

that this production conforms to the design since all testing is done

on an "as received" basis, and only after failure or completion of

test are dimensions confirmed and/or noted as to the change or wear

which has resulted. During this phase of testing, two very significant

items are reviewed. The first is an evaluation of any failures or potential failures, which could occur, to determine the completeness of

the specification; that is, have all the necessary characteristics of

80
materials and components been adequately identified and controls instituted for protection? The second is the type of ultimate failure to be

expected; that is, what will the failure mode be when the planned life

of the product is exceeded? This must be non-catastrophic! Using the

test plan, the prototype production is evaluated and upon successful

completion, final production is authorized.

This authorization begins with final engineering drawings which represent the product accepted in the prototype evaluation to a large extent,

obviously though, it must cover tolerance ranges and combinations of

tolerance stack-up not previously encountered. It is imperative that

the approval of the design, covers to the maximum extent possible, the

combinations of dimensions and manufacturing variables which could be

encountered in long range production. To do this on a planned basis

is not feasible, so the random approach to the various combinations is

utilized by requiring a production quantity based upon the complexity

of the design. This production run is controlled by manufacturing and

quality control, utilizing the same activities that would be in place

as required by this design. Samples representing the production are

selected and tested using the same test plan previously used and upon

successful completion, further production and shipments are authorized.

This final stage is repeated whenever design changes are required which

necessitates Reliability testing approval.

Control of product design, therefore, is fundamental to the manufacture

and sale of any product. All the possible contingencies must be ex- plored to the fullest extent so that when the design has been finalized,

no surprises are upcoming. Product use must be simulated and utilized

as the test method, and in most cases, the conditions extrapolated to

the maximum expected. The failure modes must be known, and any possible malfunctions, due to misuse, must be taken into account. Detailed methods for product use, and instructions for installation are

a must, as is adequate protection for the product, until delivered for

use.

To summarize, product failure may be attributed to either quality of

conformance or quality of design. As in the case of love and marriage,

"you can't have one without the other," if you expect a happy ending.

81
FACTORS AFFECTING PRODUCT LIFETIME

PRELIMINARY RESULTS OF A RESEARCH STUDY*

W. David Conn, Carol Inge,

Biswapriya Sanyal, and Elaine Warren

School of Architecture & Urban Planning

University of California,

Los Angeles, California 90024

Abstract

A possible method of reducing solid waste (to alleviate problems of solid waste management, resource depletion, and environmental degradation)

is to increase the lifetimes of durable products. Recognizing that in

practice these lifetimes are determined not only by the physical durability "built in" by the manufacturers but also by a variety of other

factors, an NSF-sponsored research project at UCLA is currently seeking

information to assist government decision-makers in developing cost-effective waste reduction policies. Consumers have been surveyed to obtain data about their acquisition and disposal of small household appliances (such as irons, toasters, etc.); manufacturers have been asked

about their actions affecting product lifetimes; and the nature and extent of second-hand markets have been examined. Preliminary results are presented.

Key Words

Product lifetime; durability; solid waste management; waste reduction;

small household electrical appliances, consumers; second-hand markets.

Introduction

Extending the lifetimes of durable products (and thereby delaying the

need for replacements) has been suggested as a means of conserving natural resources, lessening environmental impacts, and reducing solid

*This paper is based on a study entitled "Factors Affecting Product Lifetime: A Study in Support of Policy Development for Waste Reduction",

supported by the National Science Foundation. Marian Burke, J. Eugene

Grigsby III, Richard A. Kentro, Thomas H. Hale, Mary Hruby, and Richard

J. Lutz have contributed to the research. Any opinions stated herein

are those of the authors alone and do not reflect an offical view of

the National Science Foundation or of the University of California.

82
waste management costs (1,2,3). Careful examination of the likely effects of product lifetime extension on materials and energy flows has

shown that the outcome is not always predictable, and that it could be

counterproductive with respect to the stated objectives (4). For example, an automobile could almost certainly be built that would last con- siderably longer than present models, but it might also weigh considerably more and consume much greater quantities of gasoline.

Nevertheless, it does seem likely that many situations exist in which an extension of product lifetime would indeed serve the intended objectives.

Given that such an extension might be desired (for this or any other

reason) , policy-makers face the question of how it might be achieved . Many policy measures proposed in the past, such as durability standards,

product labeling, and requirements for longer warranty periods, seem to

have been aimed at persuading the manufacturers, directly or indirectly,

to produce products that are physically more durable.! However, it is

not at all clear that the physical durability built in by a manufacturer is necessarily the sole or even a major determinant of a product's

lifetime in use . The latter appears to be influenced by the decisions

and actions not only of the manufacturers, but also of the distributors,

repair industries, taxing and regulatory authorities, and (perhaps most

importantly) the consumers themselves.

In order to assist policy-makers in this poorly understood area, a re- search project sponsored by the National Science Foundation has been

seeking information on "Factors Affecting Product Lifetime". This paper

presents preliminary results from the study, which is currently nearing

completion.

Nature of the Study

The study has been exploratory. It has covered a selected set of products, namely small household electrical appliances, as listed in

Table 1. It has been conducted in a limited geographic area, namely, in

and around the City of Santa Monica, California. Although this City

has a mix of population, ethnic, income, housing, and other characteristics that is thought to be reasonably representative of many major com- munities throughout the U.S., it is recognized that the findings of the

study may have a regional bias; for example, the prevalence of certain

second-hand markets, such as garage sales, might be influenced by climatic factors.

The study has been conducted in three parts. In the first part, consumers have been asked directly a variety of questions concerning their

acquisition, use, and disposal of the products under investigation, as

1. This may not necessarily be true in every case. For example, product

labeling may simply have the purpose of improving market efficiency

by producing consumers who are better informed; it may not be intended specifically to influence behavior.

85
TABLE 1 Products Covered in Product Lifetime Study

Toasters

Toaster ovens Blenders

Coffee-makers

Can-openers

Frypans/ skillets

Irons

Blow hair-driers

Bonnet hair-driers

Vacuum cleaners

Radios

Black and white portable TVs

well as about relevant attitudes. In the second part, manufacturers

have been asked for their perceptions of consumer responses to some of

the questions previously mentioned, as well as for information regarding

the feasibility and desirability of a number of possible policy approaches aimed at extending product lifetimes. The third part has consisted

of an investigation of second-hand markets, on the grounds that these

provide an opportunity for the transfer of products from owners who no longer use them to potential new users.

The findings regarding second-hand markets have already been reported in

a separate paper (5) and will merely be summarized here. The responses

obtained from manufacturers have not yet been fully analyzed, and therefore will not be discussed in this paper. Instead, the primary focus

will be on the preliminary findings from the survey of consumers.

Second-Hand Markets

Due to limitations on resources, no attempt was made to conduct a fully

comprehensive investigation of second-hand markets; rather, efforts were directed primarily at:

(i) identifying market channels for the products covered in the study;

(ii) gaining a reasonably reliable estimate of the volume of products

transfered via these channels; and

(iii) understanding the principal factors and constraints affecting the

operation of these markets.

The information was obtained by means of interviews with market participants and other interested parties, reviews of tax records, printed advertisements, and other pertinent documents, and field observation.

Table 2 lists the markets that were examined. However, it is recognized

that in addition, certain stores selling new appliances will accept used

products in part-exchange; furthermore, some stores offer for sale re- built or reconditioned appliances. The principal findings of the investigation can be summarized as follows:

(i) The volume of small household electrical appliances transfered via

81^
the second-hand markets studied is small, numbering in the tens or hundreds of appliances per month within the Santa Monica area, compared

with the thousands of new appliances sold monthly in the same area,

(ii) The second-hand markets are frequently inter-related, in that products bought at one market (e.g., a garage sale) may subsequently be

sold at another (e.g., a swap meet). Discards that have not sold in

other markets may be "dumped" on the charitable organizations such as Goodwill Industries and the Salvation Army, qualifying the donor for a tax deduction. As a last resort, some products are sold "as is" to dealers from South of the U.S. border, where their useful lifetimes may be

extended further.

TABLE 2 Second-Hand Markets for Small Electrical Appliances

Garage sales

Swap meets

Private sales via classified advertisements

Privately operated thrift stores

Charitably operated thrift stores

2 Consumer Survey

In the initial phase of the consumer survey, a randomly selected sample

of 3291 households were screened by telephone to identify those that

had disposed of one or more of the products under investigation during

the past 12 months. "Disposing" in this context did not necessarily

mean "throwing away" but rather refered to the termination of a product's useful life within the household. Table 3 lists the options that

fell within the definition of "disposal" for the purpose of the study.

Respondents who qualified in the telephone screening were asked to participate in home interviews. A total of 311 interviews have since been

completed

.

TABLE 3 Disposal Options Considered in the Study

Store (with no definite intention of re-use)

Throw away

Give to friend or relative

Donate to charity

Sell

Trade in

The frequency distribution of the various disposal options is given in

Table 4. It is significant that the two most frequently chosen options

(stored and thrown away) can be considered the most "wasteful" since

they correspond to non-use of the product; the other four options en- tail a greater likelihood of further use. The primary reasons given

for the choice of each option (as listed in Table 5) are consistent

with intuitive expectations. An interesting observation is that those

2. The survey itself was conducted under contract by The Planning Group,

Inc

.

85
options providing some monetary gain to the disposing household (i.e.,

donated, sold, traded in) appear to have been chosen by middle-income

families

.

TABLE 4 Frequency of Choice of Disposal Options

%

Stored 41

Thrown away 21

Given away 18

Donated 11

Sold 7 Traded in - 2 100

TABLE 5 Primary Reasons Given for Choice of Disposal Option

Stored: "Couldn't decide what else to do with it" (given

by 30% of those who stored products)

Thrown away: "Damaged and too costly to repair" (30%)

Given away: "A friend or relative needed one" (40%)

Sold: "Needed the money" (25%)

Donated: "To support Goodwill or the Salvation Army" (30%)

Traded in: "To get a price cut" (43%)

Table 6 indicates the frequency with which products needed repair at the

time of disposal, in aggregate and by disposal option. It is significant that nearly half of the products did not need repair when the

household stopped using them, although it does appear that many of these

products in working order were passed on, in one way or another, to other

potential users.

Of the households whose products needed repair, only 46% considered doing so. Cost and inconvenience were cited as the main reasons for not

repairing. Since the likelihood of having a broken product repaired

would be expected to depend largely on the relative cost of repairing

versus buying a new product, it is important to note that the products

investigated in the study had generally been fairly inexpensive when

TABLE 6 Products Needing Repair at Time of Disposal

%

Total 54.2

By disposal option

Thrown away

Donated

Traded in

Stored

Sold

Given away

95

63

57

53

24

15

86
purchased; the average price (of those that were remembered) was $43,

while the median was $21. Furthermore, 95% of the products thrown away

and 70% of those stored had cost less than $30. In contrast, it was determined in another part of the study that the cost of repairing one

of the same products typically falls in the range of $7-15. Responding

to an attitudinal question posed elsewhere in the survey, more than half

of the respondents said that they would not hesitate to throw away a product costing less than $20 if it broke down. The responses to other

attitudinal questions relating to repair are given in Table 7; they

provide further Insight as to why a breakdown often signals the end of

a product's useful life.

TABLE 7 Consumer Views on Repairing Small Electrical Appliances

% in agreement

"Items should be easier to repair" 98

"Some products are not worth repairing" 80

"Getting items repaired is unconvenient" 73

"It is often cheaper to buy a new product

than to repair an old one" 70

The patterns of acquisition of the products disposed of and their re- placements (where acquired) are indicated in Table 8. It is interesting that many products which were originally received as gifts were subsequently replaced by direct purchases. The survey revealed that 90%

of all products were acquired new, and that most of those acquired used

came through informal channels (e.g., from a friend or relative) rather

than through a second-hand market such as a garage sale or thrift shop.

TABLE 8 Sources of Acquisition

Old products (those that

had been disposed of)

Purchase

Gift

Other

56.3

39.5

4.2

New products (acquired as replacements)

69.8

26.4

3.8

%

When asked about the importance attached to various criteria when the

original product was purchased, performance, reliability, and durability were most commonly rated "important" or "extremely important" by

the respondents (as indicated in Table 9). However, although durability

rated highly on this question, it is interesting to note that almost

one-third of the respondents had not known how long their products were

expected to last.

Table 10 lists some general statements regarding product satisfaction,

with which many respondents "agreed" or "strongly agreed". Although

care was taken in designing the survey instrument to avoid "loading"

the questions, it is significant that these expressions of discontent

87
TABLE 9 Criteria Used in Purchasing Products

% considering important

or extremely important

More important criteria

Performance

Reliability

Durability

99

98

88

Less important criteria

Terms of warranty

Ease of repair

Appearance

50

50

40

shows a lack of consistency with the response to another question, in

which 80% of respondents claimed that they were satisfied with the particular products being discussed.

TABLE 10 Consumer Views on Product Satisfaction

Future Output From the Study

Most of the findings reported above have emerged from a preliminary an- alysis of responses to the consumer survey. Little or no attempt has

been made in this paper to explore the implications of these findings;

this will be done once the data have been subjected to more extensive

scrutiny, using a variety of analytical techniques. As mentioned earlier, the primary objective of the study is to provide policy-makers with

information that will assist them in efforts to extend product lifetimes; for this purpose, it is important both to understand the factors

that influence the pertinent decisions by consumers and others, and to

anticipate the likely responses to different policy approaches. Early

indications are that the study will indeed shed light on some of the

key issues involved.

References

1. U.S. Environmental Protection Agency, Office of Solid Waste Management Programs, Annual Reports to Congress: Resource Recovery and

Waste Reduction , U.S. Environmental Protection Agency, Washington,

1974-77.

% in agreement

Products are not built the way they used

to be

I am often disappointed with the products

I buy

Products break down too soon

I would gladly pay more for more durable

products 87

57

55

75

88
2. Wahl, D., Reduce - Targets, Means and Impacts of Source Reduction , League of Women Voters, Washington, 1975.

3. Conn, W.D., ed.. Proposed Policies for Waste Reduction in California , California State Solid Waste Management Board, Sacramento, 1976.

4. Conn, W.D. , "Consumer Product Life Extension in the Context of Materials and Energy Flows" in Pearce, D.W. and Walter, I., eds.. Re- source Conservation: Social and Economic Dimensions of Recycling , New York University Press, 1977.

5. Conn, W.D. and Sanyal, B., "The Significance of Second-Hand Markets

for Small Electrical Appliances", Discussion Paper, UCLA School of

Architecture and Urban Planning, 1977.

89
I
SESSION III

DURABILITY TECHNOLOGY

IN INDUSTRY

CHAIRMAN: A. W. RUFF

NATIONAL BUREAU OF STANDARDS

BRAKE WEAR

S. K. Rhee

Bendix Research Laboratories

The Bendix Corporation

Southfield, Michigan 48076

Abstract: Automotive and truck friction materials are described, and

their wear characteristics are discussed. The wear rates of these friction materials are dependent upon many independent and dependent variables such as brake temperature, brake pressure, deceleration rate,

weight, terrain, climate, engine conditions, drivers, traffic conditions, road dust, dust shield, surface roughness of the rotor and

others. Test methods are described, and an equation is given for determining wear rate of automotive friction materials at a given temperature. The paper concludes by noting the difficulties of developing

standardized techniques for durability testing of friction materials.

Key words: Automotive friction materials; brake wear; friction material

test methods; friction materials wear; wear equation; wear mechanisms.

During a stop or deceleration a brake converts a substantial portion of

the kinetic energy of the moving vehicle or machinery into heat, absorbs

the heat, and gradually dissipates it to the atmosphere. The sliding

friction couple in the brake consists of a rotor (drum or disc), and a stator on which is mounted a friction material (lining, pad, or block).

The friction material is the expendable portion of the friction couple

which converts to brake wear debris and gases in use. There exist many

types of brakes, varying in size from a small brake on a bicycle or small machine to large brakes on the jumbo-aircraft. The scope of this

paper will be limited to the discussion of automotive and truck brakes.

However, general principles described in this paper will be generally

applicable to other brakes and clutches as well.

There are numerous kinds of friction materials, different in composition

as well as in configuration. The most familiar are lining materials for

automotive drum brakes and pad materials for automotive disc brakes.

Usually, these materials consist of an asbestos-reinforced polymer

(commonly phenolic resin or rubber) filled with various friction and

wear modifiers. Friction materials of this type are conventionally

called "organic" friction materials [Refs. 1-5]. For extreme heavy-duty

applications such as aircraft, rapid transit and occasionally race car brakes, copper or iron matrix materials, reinforced with steel fiber and

filled with various ceramic and metallic property modifiers, are used.

Materials of this type are called "Cerametalix" , cermet or sintered

friction materials [6-8]. When the asbestos-reinforcement in "organic"

friction materials is replaced by steel fiber, and other fillers such as

95
iron and graphite powder are added, the material is called "semimetallic"

[9]. "Semimetallic" friction materials are used for passenger car and

truck disc brakes, when "organic" friction materials are found to be

inadequate.

Desired properties common to these automotive and truck friction

materials include high, constant friction; low wear rate and no noise; no sensitivity to water; and little or no wear of the drum or disc; all

under varying service conditions. Gray cast iron is the most commonly

used drum or disc material. There are two separate pieces of linings

in a drum brake: primary and secondary linings. Both of them may be

of the same composition, but frequently they are found to be of different compositions and different sizes. The primary lining must provide

high and stable friction while the secondary lining provides stable

friction and wear resistance. Similarly, a pair of disc pads is used

for a disc brake and the two pieces of the pair may or may not be of the same composition and size.

Friction materials can be tested in the laboratory or in the field.

Laboratory testing usually uses the Friction Assessment Screening Test

Machine (FAST machine) [10] , Friction Materials Test Machine (sometimes

called the Chase machine) [11], and/or inertial dynamometer [12, 13],

while field testing uses an actual vehicle such as a passenger car or truck. The FAST machine employs a 1/2-inch square sample of friction

material rubbing against the flat face of a 7-inch diameter cast iron

disc which rotates at a constant speed. The heat generated by the rubbing action raises the temperature of the disc as the test proceeds. In

the case of the Chase machine a 1-inch square sample of friction material is slid against the internal siorface of an 11- inch diameter cast

iron drum, and a heater-blower system can be used when desired for con- trolling the drum temperature. These two machines are more suitable for

evaluating the consistency of friction materials rather than for predicting the performance of friction materials on a vehicle. In other

words^ these two machines are quality control tools, and results obtained

from these two machines do not correlate very well with vehicle data

[14]. In contrast to these two machines an inertial dynamometer employs

full-size brakes and linings (or pads). Brake drums (or discs) are linked to inertial steel discs, which are bolted together and rotated

to simulate the vehicle weight and speed. The single-end inertia dynamometer utilizes only a single brake while the dual-end inertial dynamometer uses one front brake and one rear brake. The quadruple inertial

dynamometer uses all four brakes. Since the coefficient of friction of

friction materials changes depending upon service conditions, there is a continuous load transfer between the front and rear brakes during

braking. This makes it highly desirable to evaluate friction materials

using the dual-end dynamometer or quadruple dynamometer. These inertial

dynamometers produce test results which are usually in fair agreement

with vehicle test results. One major disadvantage of these inertial

dynamometers, however, is their high initial cost. The reasons for the

fair agreement rather than excellent agreement are many. A brake system

9h
mounted on a dynamometer cannot fully duplicate a brake system on a vehicle in terms of air flow, vibration, road dust and other factors.

For example, one may find differences in wear rates between an inner

disc pad and outer disc pad when tested on a dynamometer, while vehicle

tests indicate no differences. This difference is due to the fact that

vibration of a moving vehicle assists disc brake shoes to retract from

the rotor when the brake hydraulic pressure is released, while a rigid

inertial dynamometer provides no significant vibration to the brake, so that one of the two pads tends to hang and slide continuously against

the rotor.

There are many dynamometer and vehicle test procedures for evaluating

the friction, friction stability, noise, wear, sensitivity to water,

and rotor wear. These include wear-versus- temperature , SAE (Society of

Automotive Engineers) Fade, FMVSS (Federal Motor Vehicle Safety Standards) 105-75, Detroit Traffic, Los Angeles Traffic, Jennerstown Mountain,

Davis Dam and Pikes Peak. Generally speaking, dynamometer tests are used to screen candidate friction materials, and then, dynamometerscreened friction materials are always vehicle- tested on the road for

each type of vehicle before release to the public.

If a fixed amount of work (or braking) is performed under the conditions

of fixed normal load (or torque) and sliding speed, the wear rate of

automotive and truck friction materials remains fairly constant with

respect to rotor temperature up to approximately 220°C and the rate in- creases exponentially thereafter [15-18]. At low temperatures below

220°C (rotor temperature), the wear rate may remain constant or increase

slightly with increasing temperature, depending on the composition of

the friction material. The wear at these low temperatures has been

attributed to the abrasive and adhesive wear mechanisms [19]. The ex- ponentially increasing wear rate at high temperatures is due to the

thermal decomposition of polymeric Ingredients present in friction

materials [15, 16]. In other words wear rates of polymer-matrix friction materials can be very sensitive to brake temperatures. The wear

rate at low temperatures is also very much dependent upon the surface

roughness of the rotor. In general, the low- temperature wear rate in- creases with increasing roughness of the rotor friction surface [18, 19].

Of course, the roughness of the rotor surface is influenced by the

mating friction material itself as well as road dust.

The wear rate at a given temperature of automotive friction materials is

related to the normal load (p) and sliding speed (v) in the following

manner:

W = k P^ t^

where W is the amount of wear; k, a, b and c are constants characteristic

of a given friction pair; and t the sliding time [15, 16, 20]. This

wear equation is also found to be applicable to the sliding wear of

95
ceramic materials [21]. As a general rule, a and b are different from

each other, being substantially different from unity, and c is usually

unity. In other words, the wear rate is not a linear function of the

normal load or sliding time. Thus doubling the normal load may not

raise the wear rate by a factor of two, but doubling the sliding speed

may raise the wear rate by more than a factor of two.

Apparent from the discussions given above is the complex nature of

testing a friction material for its durability or life. The durability

is dependent not only on the brake temperature, but also on the brake

pressure and deceleration rate. Furthermore, each type of vehicle tends

to have its own brake design or designs; usually front brakes are different from rear brakes. Some brakes may have dust shields, thus lowering the three-body abrasive wear, but raising brake temperatures. Rear

brakes may run hotter than front brakes because of the heat generated

by the engine in the front. Inner disc pads may run cooler than outer

disc pads because of different air flow rates, or vice versa. In addition to all of these variables, there are a few more; weight (heavy vs. light), terrain (mountainous vs. flat), weather (hot vs. cold), engine

conditions (different engine deceleration), different drivers (different

driving habits), and traffic conditions. Also, brake linings and disc

pads tend to wear out unevenly (tapered). In a case such as this, the

average volume wear rate may be more meaningful to scientists than to consumers. From a practical point of view consumers are more interested

in the maximum thickness wear. Because of all these variables, it is

not unusual to replace brake drum linings or disc pads after 60,000 or 70,000 miles in one case, versus only after 20,000 miles or less in an- other case. Because of the many variables, it is difficult to compare

friction materials by road tests alone. Controlled testing has been

recently done by simulating the Detroit Traffic Road Test for a specific

vehicle, using an inertial dynamometer. Those tests exhibited considerably more consistent results than actual road tests.

In conclusion, if a "typical" vehicle (or brake) and "typical" service

conditions can be defined, the durability of friction materials can be more readily determined. However, one must question if there are such

things as "typical" vehicle and "typical" service conditions. In addition, the durability evaluation has to be coupled with other property

evaluations: friction, friction stability, noise, rotor wear, and water

recovery. Also, friction materials of one composition found suitable

for one brake system may turn out to be unsatisfactory for another brake

system. Thus, it must be said that if durability testing is to be

standardized for friction materials, a tremendous amount of preparatory

work will be needed to generate a reasonably satisfactory and acceptable

set of test procedures. This task will prove to be extremely complicated and difficult.

96
References

1. R. E. Spokes and E. C. Keller, "Friction Element", U.S. Patent No.

2,428,298, September 30, 1947.

2. R. E. Spokes, "Friction Elements and Methods of Making the Same",

U.S. Patent No. 2,685,551, August 3, 1954.

3. B. W. Klein, "Friction Controlling Means", U.S. Patent No. 3,007,

549, November 7, 1961.

4. S. B. Twiss and E. J. Sydor, "Friction Elements and Methods of

Making the Same", U.S. Patent No. 3,007,890, November 7, 1961.

5. F. W. Aldrich and M. G. Jacko, "Organic Friction Materials",

Bendix Technical Journal, Vol. 2 (No.l), p. 42 (1969).

6. A. W. Allen and R. H. Herron, "Friction Article", U. S. Patent No.

2,948,955, August 16, 1960.

7. N. A. Hooton, "Metal-Ceramic Composites in High-Energy Friction

Applicat ions", Bendix Technical Journal, Vol. 2 (No.l), p. 55

(1969).

8. K. Aoki and J. Shirotani, "The New Tokaido-Line Bullet Train",

Bendix Technical Journal, Vol.6 (No. 2) p.l (1973/74).

9. S. K. Rhee and J. P. Kwolek, "Sponge Iron Friction Materials",

U.S. Patent No. 3,835,118, September 10, 1974.

10. A. E. Anderson, S. Gratch and H. P. Hayes, "A New Laboratory

Friction and Wear Test for the Characterization of Brake Linings",

SAE Paper No. 670079 (1967).

11. A. J. Burkman and F. H. Highley, "Laboratory Evaluation of Brake

Lining Materials", SAE Paper No. 670510 (1967).

12. D. W. Howard and J. L. Winge, "An Automatically Programmed Quadruple Dynamometer for Vehicle Brake Testing", SAE Paper No.

670144 (1967).

13. D. Sinclair and W. F. Gulick, "The Dual Brake Inertial Dynamometer

-A New Tool for Brake Testing", SAE Paper No. 488C (1962).

14. J. D. Preston and R. J. Forthofer, "Correlation of Vehicle,

Dynamometer and Other Laboratory Tests for Brake Friction

Materials", SAE Paper No. 710250 (1971).

15. T. Liu and S. K. Rhee, "High-Temperature Wear of Semimetallic

Disc Brake Pads", Wear of Materials , edited by W. A. Glaeser,

K. C. Ludema and S. K. Rhee, ASME, New York, p. 552 (1977).

16. T. Liu and S. K. Rhee, "High Temperature Wear of AsbestosReinforced Friction Materials", Wear, Vol. 37, p. 291 (1976).

17. S. K. Rhee, "Wear Mechanisms for Asbestos-Reinforced Automotive

Friction Materials" Wear, Vol. 29, p. 391 (1974).

18. S. K. Rhee, "Influence of Rotor Metallurgy on the Wear of Friction

Materials in Automotive Brakes", SAE Transactions, Vol. 80,

p. 992 (1971).

19. S. K. Rhee, "Wear Mechanisms at Low Temperatures for MetalReinforced Phenolic Resins", Wear, Vol. 23, p. 261 (1973).

20. S. K. Rhee, "Wear of Metal-Reinforced Phenolic Resins", Wear,

Vol. 18, p. 471, (1971).

97
J. E. Hines, Jr., R. C. Bradt, and J. V. Biggers, "Grain size and

Porosity Effects on the Abrasive Wear of Alumina", Wear of

Materials , edited by W. A. Glaeser, K. C. Ludema and S. K. Rhee,

ASME, New York, p. 462 (1977).

H. W. Schwartz and S. K. Rhee, "Brake Dynamometer Evaluation of

the Detroit Traffic Road Test", SAE Paper No. 770026 (1977).

98
ACCELERATED TESTING OF COMPRESSORS

Frank E. Kalivoda

Copeland Corporation

Sidney, Ohio 45365

Abstract: Refrigeration, heat pump and air-conditioning compressors

are expected to have long operating lives and low failure rates.

Accelerated tests are, therefore, a practical necessity, but, care must

be taken not to introduce extraneous failure modes. This paper dis- cusses a test plan used to qualify these compressors and some of the

complexities which must be considered.

I . Introduction

A large scale program to evaluate and improve the reliability of our refrigeration and air-conditioning compressors was initiated in 1973.

An independent group was set up for this purpose and equipped with

over 250 life test stands for testing compressors under a variety of

operating conditions (1). Since that time, we have been testing com- pressors at the rate of about 700 per year. The program is proving

its merit particularly at this point in time when requirements for

performance and service are undergoing dynamic change.

The tests performed in this program have, in many cases been verified

by field results. Areas have also been found, however, where the tests

themselves can be improved. The purpose of this paper is to describe

the tests which are being performed and the areas requiring further

refinements.

II . Discussion of the Problem

A refrigeration compressor is an electromechanical device operating in

a hermetically sealed environment with two fluids-lubricating oil and

refrigerant. Residual materials and moisture can also be present.

Electrical problems, wear of bearings, rods, and pistons or breakage

of valve reeds, discharge tubes or other components are failures that

can occur.

Temperature is a major variable, defining as it were both the operating

conditions and system stresses including reactions among the lubricant,

refrigerant, and the materials used in the compressor such as motor

insulations. Normally, these materials are selected to have very low

reactivities with screening tests of new materials being performed in

sealed tubes (2). Erdman has indeed used the chemical half life theory

which states that for each 18 F rise in temperature the rate of a

99
chemical reaction doubles to design a test plan (3).

There are, of course, temperatures which must not be exceeded if con- ditions such as lubricant or insulation breakdown are not to occur too

rapidly and invalidate the test completely. Our normal limits are

230 F for the oil sump, 250°F for the discharge line, 270 F for the

motor and 330 F for the valve plate.

Another unusual attribute of the system is that oil and refrigerant 22

have limited solubility with one another. For example, at -15 F, a single phase will exist between R22 and one of the common refrigeration

oils when the concentration of oil is between either 0 and 3% or between 75 and 100%. The actual concentration will depend on the pressure. Between these two concentration ranges, two phases will exist

(4). This has two effects. The first of these is a decrease in the

viscosity of the lubricant. A 32 centi poise viscosity oil, for example, is reduced to 5 centipoise by dilution of 25% refrigerant (5).

Bearing lubrication is, therefore, directly affected.

The second effect is less obvious. A refrigerant can separate from the

oil whenever the pressures change rapidly such as during system start

up. If these conditions are not considered in design, vapor binding

of the lubrication system or perhaps even a complete loss of lubricant

could result. Crankcase heaters are one means used to protect the

compressor during this type of condition (6). Proper oil pump venting

arrangements and selection of oil solubilities are other ways of

avoiding problems.

The compressor also experiences other unusual operating conditions.

Although designed as a vapor compressor, it can be suddenly subjected

to large quantities of liquid refrigerant during periods such as the

defrost cycle of a heat pump particularly if the system is not designed

with the proper accumulators. This can lead to valve breakage and

bearing surface washout. And finally, there are conditions where

failure of other system components can produce high stresses on the

compressor.

These conditions must be factored into test plans which must also ac- count for operating life expected from compressors. Table I shows

operating hours and cycle targets for 10 years of operation for airconditioning, heat pump and commercial applications. Operation of a compressor on a test stand on a 24 hour day basis provides about 8,000

running hours per year. To qualify a heat pump compressor for 30,000

hours on that basis would require 3 3/4 years. This is obviously too

long for new product development, and some form of accelerated testing

is required.

III. Reliability Tests

The types of reliability tests we run are of two general types: bench

100
and life test. Ideally, bench tests can be used to qualify each component. Components such as valve plates and discharge tubes can be

strain gaged, for example, and the design adjusted so that the stresses

are kept below the fatigue limits. One problem, however, is in designing the test rig to simulate the actual operating conditions. Then too we have the physical size of the strain gage itself, and the difficulties in locating the gage exactly at the point of maximum stress.

Furthermore, in cases of components such as valve reeds, the effect of

combined stresses involving impact make the actual failure mechanism

difficult to determine. With bearings, there are difficulties simulating lubricant conditions. Therefore, these tests must be used with

careful evaluation and interpretation.

One advantage of testing compressors in the smaller sizes is that they

are relatively inexpensive compared, for example, to something like a large engine. Thus, the compressor itself becomes a relatively inexpensive test stand or dynamometer, although costs can exceed

$1,000 apiece for early prototypes. Then too, all of the variables

involved in the compressor, its manufacture and operation are covered

directly in statistically planned system tests.

Life tests involving complete compressors can be of two different

types. First we test directly in complete heat pump or refrigeration

systems. This can provide excellent correlation to field data. For our purposes, however, where we supply a variety of compressors to

many different system manufacturers, there are problems with cost,

flexibility, and reliability of other system components. Units are absolutely necessary for the performance of certain tests such as blocked fan, but we do the greatest part of our life testing in specially designed water cooled life test stands which can be set and

monitored for various operating conditions.

Setting up the test conditions is fairly complex. Cole and Pietsch

presented an excellent discussion of the variables and stress zones involved in testing heat pumps (7). Our conditions shown in Figure 1 and Table II have been developed along the same general lines.

Figure 1 shows typical compressor operating regions for cooling and

heating on a chart of condensing and evaporating temperatures. These

are the basic temperatures mentioned before as those which establish

the service conditions of the compressor. There are four general

zones in this chart: one a high load zone with resulting high bearing

loads; another a high flow zone where the valve reeds are stressed to

their fullest extent; third, a high compression ratio zone where the

running gear is stressed at high operating temperatures; and finally,

a low flow area where the motor cooling can be a problem. The normal

operating regions for a compressor in the cooling and heating modes

are shown on this graph. The boundaries of the regions are established

either by maximum temperatures or by standard use.

101
The rating point for cooling, point 1 and for heating, point 2, can be seen to be comfortably within these areas. Life tests performed only

at those conditions would leave unanswered the compressor durability

when operated across the whole range of conditions. One objective is

to test the compressor to values at the extremes of the operating zones without exceeding catastrophic failure conditions. Conditions 4, 5,

and 6 fulfill this requirement for high load, high density flow, and

high compression ratio conditions.

Point 7 is a heat pump operating condition. It can be encountered in

operation since our policy is to let the compressor operate during

periods of cold outside ambients. If, however, the compressor were allowed to operate with the norma J superheat, valve plate temperatures

would get much too hiqh-about 380 F. For this reason, we reconmend

that the system flood liquid back to the compressor at this condition

to keep the compressor operating at reasonable temperatures (8). A

typical recommendation is for S% dilution of the oil with liquid re- frigerant. This can be accommodated readily in systems, but does lead

to problems in controlling life test stands because of the solubility

characteristics of refrigerant and oil. A careful job of instrumentation and control is required. Thus, another test variable requiring

close measurement of oil temperature and shell pressure is added to the

test requirements.

Other conditions are shown in Table II. A stop/start test stresses the

compressor suspension and electrical components. A defrost test where

liquid is repeatedly introduced into the compressor while it is operating stresses the valves. A flooded start test causes the compressor

to be started with various amounts of liquid in the shell. Finally, a blocked fan test is imposed on the compressor in an actual system to

simulate a system problem involving a blocked condenser or failed fan.

In this case, the head pressures rise opening an internal pressure

relief valve and causing the motor protector to break the line current.

All ten of these tests are used in the qualification of new compressor

designs. For qualification, conditions one and two are run 6,000 hours,

and the remaining conditions from 2,000 to 4,000 hours each on various

compressors in a statistical test plan involving as many as 60 compressors. The first seven are normally used in the audit of production

compressors to ensure ongoing product reliability. For the audit test, we use a test sequence involving about 1,000 total hours of testing.

These tests are, incidentally, preceded by a transit test (shake and

impact) to simulate shipment.

The chemical half life theory can be used to help evaluate the severity

of a test. In the condition shown in Figure 1 for point 7 which is a heat pump test, the valve plate temperature measured with Ig F superheat at that condition on a typical compressor would be 380 F, whereas

normally, we would not want this to exceed 330 F. This would, therefore,

show an acceleration factor of about two cubed or 8. In going from

102
330 F to the 240 F experienced under the rating condition, we would

have an additional acceleration factor from a chemical standpoint of

two to the fifth power or 32. The overall acceleration between point

7 and point 2 would, therefore, be an enormous 256 from a chemical

standpoint.

The acceleration factors are further complicated in some of our com- pressors such as those used for low temperature refrigeration by the

fact that they already operate under severe conditions to just about

the limit of operation on a 24 hour day basis. The maximum compression

ratios for the air-conditioning tests shown in Table II, for example,

are about 8.6 to 1. For a refrigeration machine, operating with a -40 F evaporator and a 130 F condenser, the compression ratio, however,

is about 18 to 1. If we attempt to further accelerate the test by

reducing the evaporator temperature to -50 F, we would increase the

compression ratio to 23 to 1 which could lead to catastrophic failure

since at these high compression ratio conditions, we do get high

values of temperature as can be calculated from thermodynamic fundamentals (9).

IV. Correlation with Field Data

The correlation of results from this type of test is underway with

field failure statistics, and in many cases good correlation has already

been found. Another approach that we're taking is through a large

scale field test now underway on heat pump systems. Thirty of these

units have been placed in residences with records kept on operating

hours and cycles of operation. Six of these systems have also been

very heavily instrumented with field data system incorporating a microprocessor.

This system measures 15 system operating temperatures and two pressures

every 30 seconds while the unit is in operation. This data is transferred to our IBM 360 computer for analysis, and we will have more and

better information on the operation of such systems than currently

available.

V. Conclusions

Accelerated testing of compressors is a practical necessity for high

volume production compressors with expected long lives. In order to

have validity, however, such tests must be performed carefully with a great deal of attention to detail.

References

1. F. E. Kalivoda and K. W. Yun, "Modeling Mechanical System

Accelerated Life Tests," Proceedings of the 1976 Annual Reliability

and Maintainability Symposium, IEEE, p. 206.

103
2. H. M. Parmelee, "Sealed Tube Stability Tests on Refrigeration

Materials," ASHRAE Transactions, Vol. 71, Part I, 1965, p. 154.

3. F. G. Erdman, "Compressor Application Life Testing," Proceedings

of the 1972 Purdue Compressor Technology Conference, Roy C. Herrick

Laboratories, p. 142.

4. R. C. Downing, "Freon Refrigerants & Lubricating Oils," E. I. DuPont

deNemours and Company, Wilmington, Delaware, June 1971, Fig. 11.

5. ASHRAE Handbook & Product Directory 1976 Systems, American Society

of Heating and Air-Condi tioning Engineers, New York, 1976, p. 32.13.

6. R. E. Cawley and S. A. Parker, "Evaluation of Crankcase Heater and

its Effectiveness with a Hermetic Compressor," Proceedings of the 1972

Purdue Compressor Technology Conference, Roy C. Herrick Laboratories,

p. 475.

7. M. H. Cole and J. A. Pietsch, "Qualification of Heat Pump Design,"

ASHRAE Journal, July 1973, p. 43.

8. Application Engineering Bulletin, AE-1243-R3, Copeland Corporation,

July 15, 1977.

9. ASHRAE Handbook of Fundamentals. American Society of Heating

Refrigeration and Air-Condi tioning Engineers, New York, 1976, p. 9.

lOk
TABLE I

Reliability Targets

Application Life Hours Cycles

Air-Conditioning 10 Years 15,000 75,000

Heat Pump 10 Years 30,000 150,000

Commercial 10 Years 58,000 350,000

TABLE II

Life Test Conditions

Test

Head

(PSIG)

Suction

(PSIG)

Suctign Temp.

1

.

Design Condition Heating 130 45 20

2. Design Condition Cooling 110 30 10

3. Stop/Start 360 80 65

4. High Load 550 100 65

5. High Density Flow 170 100 59(Max.)

6. High Compression Ratio 360 50 65

7. Heat Pump 226 13 0 to -10

8. Defrost 300 24 20(Min.)

9. Flooded Start (Approx.) 250 60 60

10. Blocked Fan (Approx.) 700 200 Varies
LlI

LUoMOo

CD

CO

2:o'-' I—

I— <=3: d: I—I uj o Q

oo o uj LU O Q_

q: ZD

Q.

O OO

O 1—t u. o [—0 < o d; I—

LUo

LU

LU

LU

I—

_J

O-

>-

LUoM

LT)

OO LU LU O

CL. 2: o o •-« o I—<c o ^ F 1 1

l-Lj1 1 , ~ CD

~o

LO U—

J * 0 p—

** 1—] • CI. 0 1 1 1 - h- 1— -0 O) CO CD S- LUI— 1—1 CD

1— -r- < Ll_ 1— q:0

q; D_

LU

U_ > LU -0 LU

d:00

a:

LU

CQ

r)

2: _ooCMI o1^ o oLT) o o00 o o o f— o o o00 o

106
AUTOMOBILE DURABILITY

C. J. Brady

General Motors Corporation

Engineering Staff

Warren, Michigan 48090

H. W. Larsen

General Motors Corporation

Engineering Staff

Mil ford, Michigan 48042

Abstract: The automobile industry is designing and testing vehicles to

meet increasing requirements for durability, safety, emission control,

and fuel efficiency. Recent technical developments at General Motors

have provided previously unavailable quantitative information on usage

of vehicles by customers. This presentation discusses an electronic

field data collection program and the way General Motors is combining

the resulting information with modern design analysis and test methods

to estimate the service life of vehicles.

Discussion: When we examine U.S. vehicle registrations, we find that

about 93% of the vehicles are still in service in five years (Figure 1)

.

Presumably, the others are no longer registered because of collision,

fire, theft, or export. About half of the vehicles are still in service

after ten years, and about 11% are still registered after 15 years.

These numbers, obviously vary year to year, but these figures represent

the general population of passenger cars over several model years. We

see from this that vehicles have potential durability upwards of 15

years. Vehicles that do not receive reasonable maintenance and are exposed to more abusive operation go out of service early.

107
20 - ^ 11%/15YRS.

ol 1 I I I I I L_

2 4 6 8 10 12 14 VEHICLE AGE (YEARS)

Figure 1

The domestic automobile industry is presently engaged in a major

redesign of passenger cars to meet the national requirements for

emission control, fuel conservation, and safety. It is General Motors'

plan to produce cars that meet those requirements with as much utility

and durability as possible.

To design, test, and develop vehicles to have a long, useful life, we

need to know some things about the way the whole spectrum of customers

uses our products.

A few years ago, we prepared some cars to record a variety of temperatures, pressures, forces, and motions (Figure 2). Data from this

program were then combined with other available information such as government road statistics and past test versus field durability data.

At that time, our road test schedules were modified to better match

customer vehicle usage. This early work also gave us insight into some of the concepts and philosophies which would later be employed to more precisely define the customer usage spectrum.

This method of data collection tells us much about traffic patterns in

general but not enough about individual car usage over extended time

peri ods

.

108
Figure 2

In order to determine how the whole population of vehicles is used

we decided to measure the vehicle usage of randomly selected customers

over extended time periods. Certain vehicle performance parameters

and system or component loads and motions would be used to characterize

vehicle usage.

This has become practical with the advent of micro-electronics. To

monitor individual car usage, we have developed some instruments that

can be installed in customers' cars and operate unattended for several

months

.

Figure 3 illustrates a complete instrumentation system to record

steering linkage forces. These instruments contain their own power

supply, signal conditioning, and data reduction electronics. This

complete package concept allows data storage capacity for up to 10

million bits of data that can be produced in a few months of customer

operation. A similar setup to record dynamic front suspension loads

is shown in Figure 4.

109
Figure 4

110
It is important to us that the owner use the vehicle just as he would if

the devices were not present. The owners are generally not told the

details of the measurement until the data collection is complete. These

devices are installed in the customer's vehicle so they do not interfere

with his vehicle usage in any way (Figure 5).

Figure 5

The locations of some randomly selected owners of one model of vehicle

with suspension force recorders is shown in Figure 6.

In many cases, we continue with the instrumentation with the second,

and sometimes third owner, since our objective is to measure the vehicle

activity over an extensive portion of the service life. In almost all

cases, we have found the owners of these vehicles to be enthusiastic and

willing to participate in this type of program (Figure 7).

An example of typical data resulting from this program is shown in

Figure 8. Specifically, this shows variation in front suspension forces

experienced by just 5 of the 20 customers used in this particular

project.

Figure 9 shows another example. Here we have determined the average

miles driven in various speed ranges by a randomly selected group of 20

1973 intermediate car owners over a 2-year period.

Ill
Figure 7

112
MUSPER

1.000 iMKES

Figure 8

AVERAGE CUSTOMER

MILES DRIVEN IN SPEED BANDS

20 1973 A CAR CUSTOMERS

378,568 COMBINED DATA MILES

17.5 27.5 37.5 47.5 57.5 67.5 77.5

Sf>EH> BANDS

Figure 9

115
In Figure 10, the data has been analyzed to provide a statistical estimate of the number of brake stops in various kinetic energy bands that

the 80th percentile vehicle will experience. This statistical estimate,

based on a rather small sample, indicates that 80% of the customer population makes fewer brake stops in each kinetic energy range than the

graphed values.

BRAKE APPLICATIONS PER 1000 MILES

IN KINETIC ENER(3Y.BANDS

0 10 20 30 40 50 60 . 70 80 KINETIC ENERGY DISSIPATED

(FT. LB./LB.)

Figure 10

Since beginning this type of program in late 1973, 757 channels of this

type of instrumentation have been installed in over 100 different ran- domly selected customer vehicles throughout the country. Over this

period, more than 2.5 million vehicle miles of data have been collected,

analyzed, and used to design and develop products to have durability

that is well matched to the customers' needs. These data are the basis

for various laboratory tests and design analysis.

In addition to the direct instrumentation measurements, surveys and

inspections of customer vehicles are frequently conducted to add to our understanding of vehicle usage in the hands of the customer.

For example, recently we conducted a survey to determine how brake pads

and shoes wear on customer vehicles. To accomplish this, we replaced

the brake pads and shoes (Figure 11) on 200 customer owned, randomly

selected 1974 and 1975 cars. The friction materials remaining on their

pads and shoes were measured, and from measurements and mileage on the

vehicle, we were able to project the mileage at wearout.

lli^
Figure 11

The distribution of projected wearout life from this sample of 200 car owners is shown in Figure 12.

FRONT LINING SET

/198 CUSTOMER OWNED

/ 1974 & 1975 A CARS

j

PROJECTED WEAROUT MILES

Figure 12

115
We have also made similar friction material measurements on vehicles | where we are measuring their brake usage with instrumentation in order ! to determine the variables that are related to brake wear.

| The relationship between projected brake wearout mileage and the average I kinetic energy dissipated per mile by a sample of 1973 "A" car customers

j is shown in Figure 13.

I Using these data, we now design vehicles with an improved understanding i of the operation they will be exposed to by the customer, and we now I have a family of passenger car durability schedules that are factually I related to customer usage and allow prediction of the product endurance

in the hands of the customer.

Figure 13

116
The load spectrums measured on customer vehicles are used in the finite

element design of new vehicle structures to achieve a desirable balance

of stress distribution with the least massive structure (Figure 14).

Estimates of production process variations that affect component

strength must be included in these analyses. When prototypes of the new design are available, the presumed load spectrum and calculated

strain values are refined with road test measurements on the customer

related Proving Ground durability schedules.

Figure 14

Corrosion and other aging processes are difficult to evaluate in a short

test time simply because they are time dependent chemical processes;

however, an approximate precursor of customer vehicle corrosion has been

reasonably successful.

Vehicle and component corrosion rates are accelerated by exposing them

to the road salt and mud comparable to the northeastern United States,

and periodically placing them in a warm, humid chamber to speed-up the

chemical processes (Figures 15-17).

The corrosion of test vehicles and standard steel corrosion coupons

attached to them (Figure 18) has been correlated with similar customeroperated vehicles also with corrosion coupons in various United States

and Canadian locations.

117
Figure 16

118
Figure 18

119.
You are no doubt aware that General Motors has removed several hundred

pounds from many of the vehicles in the past two model changes to

improve fuel economy. My discussion indicates the extent of the engineering that went in when the pounds came out.

I suspect many of the techniques we are using today, such as cumulative

damage analysis and finite element analysis, were pioneered by people

attending this symposium. We appreciate these new tools; they enable

us to do a more precise job of engineering durability into our products

today than was possible a few years ago.

It is General Motors' plan to apply all available technology that will

make it possible to produce vehicles that have a balance of emission

control, fuel efficiency, durability, utility, performance, safety,

comfort, and convenience that is acceptable to the regulators, and

desirable and affordable to the consumer.

120
WEAR ANALYSIS IN OFFICE MACHINES

P. A. Engel

IBM Corporation

System Products Division

P.O. Box 6

Endicott, NY 13760

Abstract: In many input-output devices, such as printers, impact combined with

sliding between mechanical components is the chief cause of wear. This paper

first describes the phenomenoiogical aspects of this type of wearing and then analytical formulation is discussed. Wear prediction for industrial design purposes hinges on the recognition of the wear mechanism and on the determination of the wear

parameters by simple tests. Computation of the contact loading intensity and of the

wear formation geometry are the analytical aspects of the wear prediction process.

Introduction

The input-output devices used in business machines (such as computers) have stringent requirements for durability and long wearlife. As a result they place special

requirements on the mechanical designer. Two of the principal types of designs that are involved are classified as (1) printer and (2) carriage (shifting) mechanisms.

Carriage devices operate primarily on rolling and sliding bearing elements, with

various gear-type transmissions. In these devices, hydrodynamic or boundary lubrication is often possible, loads are usually moderate and predictable, and a choice of

materials can be made by more-or-less conventional wear-test methods.

In mechanical printers the tribological (relating to friction, wear, and lubrication)

problems tend to be unique. Impact loads, aggravated by associated sliding, abound.

Lubrication is often severely limited or excluded. The contact geometry, typically

confined within narrow limits, gives rise to large local (contact) stresses. A variety

of wear mechanisms have been noted depending on the materials that ore used.

The success of a wear design is dependent on recognition of the correct wear mechanism in the prototype and on simulation of the relevant loading parameters to be

incorporated in a "robot" wear test procedure. Based on these preliminary investigations, the quantitative engineering wear predictions may be construed and eliminate the need for generating expensive prototype test data [ 1] . We should consider a few of the concepts which are helpful to aid in the further discussion of wear in general.

121
One-body-wear is a terminology applied to the significant wear on only one of the

two repetitively impacting solid surfaces. Two-body-wear is defined as the simultaneous wearing of both surfaces.

The three basic contact modes (sliding, rolling, and impacting) are often present in

hybrid (compound) forms; in fact, compound impact with sliding is the most damaging wear mode in unlubricated contacts. In comparison, pure, normal impact is often more severe than compound impact in lubricated contacts.

The wear mechanism, a physical phenomenon, usually suggests an empirical formulation, such as an equation connecting wear volume W with contact force P and the

number of cycles N,

W = KP' N, (1)

for a given range of P. Here, K and c are experimental constants.

The following descriptions are examples of a few basic cases of printer wear analysis .

Type Wear Against Paper or Ribbon

The first description is the development of a wear prediction formula and a preliminary test procedure for the typical impact wear application of metal type [2] repetitively striking against paper or ribbon. We are considering computer type that was designed for impact on paper supported on a platen. The impact occurs "on

the fly" to create a faster printing operation; this wear is a compound impact-withsiiding contact mode.

The impact force of this type can be measured by a transducer replacing the platen.

This condition, of course, somewhat alters the impulse; however, in the test cases we

could verify the fact that an approximate sinusoidal force-time relationship is produced which is unchanged as repetitive impacts create wear on the type.

The wear process results in the smoothing of the metal surface. For a metal surface

to be resistant, it has to be hardened or plated with a hard layer such as chrome.

The process of printing causes this hard surface to strike against a constantly changing, nominally soft paper surface, creating a "one-body wear" situation for the

harder contact partner which is the metal. Close investigation indicates an abrasive wear mechanism operative, activated by occasional fibrous matter in the paper.

The following description briefly outlines the test procedure applied in our laboratory. The abrasive wear constant K of the paper was found by special sliding wear

tests. A large,! .2 m diameter drum tester [3] , with a cylindrical surface had the

paper stretched over its circumference. A ball specimen of the type material was

122
pressed against it with fixed force P. While the drum was rotated, the ball holding

fixture was also given a small transverse motion so as to touch consecutively new

areas of paper. The test facilitated evaluation of the abrasive wear constant

H W

K

~' (2)

where H^^ is the hardness of the type and x is the total sliding distance.

The constant K was found quite different for the various papers (in a range of two

orders of magnitude) with an approximate 10 as an average value. This value is probably three orders of magnitude lower than that commonly encountered for metals,

In addition, there is a great deal of dependence on conditions such as temperature,

humidity, and others. More wear was found when the type was attached to a stiff cantilever which resisted bending in the tangential plane during impact. A freely

rotating, "point-mass" style of type showed less wear.

Proceeding from the phenomenological description to the wear analysis

we consider a tangential ly spring-restrained type slug (containing a print character)

impacting a platen-supported layer of paper. A compound impact is generated by

the relative sliding speed v of the platen (to which the paper is assumed to adhere)

with respect to the normally approaching type. Consider an individual impact after

the first contact with the paper. The type is gradually accelerated by the platen in

the X- direction, while it slips. If the impact is of sufficient length, the horizontal

momentum exchange is completed at some time t < t* (t* being the contact time).

At this time, adherence, in the tangential sense, has occurred and slipping has

stopped

.

The slip during an infinitesimal time dt is dX = v.dt - dx, (0 < t < t < t*).

Assuming that wear is only accrued during slipping, but not in the adhering phase,

the infinitesimal wear dW caused by slip dX can be formulated if an empirical wear

mechanism equation is available. For a linear abrasive wear mechanism, such as the one involved in Eq . (2), we can write

dw(t) = mLixW

(3)

m

The impact force may be related to the tangential position x of the slug at time t by

its equation of motion. Considering the type slug as a point mass m, acted upon by

the Coulomb friction force, we obtain the differential equation

mx = p

P(t) - kx, (0 < t < t) (4)

125
with initial conditions t = 0; x = x = 0. Here |j is the coefficient of friction and

k is the spring restraint of the type holding member.

Integration of Eq. (4) is facilitated by the pulse shape approximation P(t) =

sin TTt/t*. The wear per cycle may be integrated over the impact duration, yielding

t* t AW = f dW = r dW = ^^^^°C(f) (5)

where f = -nrnV/^P^f* is the "slip factor." For the simple case of unrestrained

type (k = 0),

C(f) = f/2, (0 < f < 2)

= 2(1 - 1/f), (f > 2)

It is noted that the value of f is between 0 and 2 for adherence occurring during

impact (t < t*), while f > 2 means continual slipping during the whole impact

duration.

The linear wear model suggests that the final wear occurring after N load cycles

will be W = N. AW. The depth of wear over the type character may be obtained

by averaging a depth h uniformly over the impacted surface area.

An examination of Eq. (5) shows that the wear is proportional to the sliding speed

V and, also, to the normal impulse (which, for a sinusoidal pulse is 2Pot*/iT'). The

hardness of the type is critical, and its role is wear resistance. Of course, when a hard plating is worn off, wear resistance is dictated by the sublayer.

The above wear formulation has proven quite reliable, and it allows a rapid evaluation of various prospective materials to be used for type. The preliminary testing

includes hardness test for the metal, a sliding wear test for the friction coefficient

and the abrasive constant, and a relatively simple impact robot test to examine the

relevant wear mechanism.

Several, similar type elements have been analyzed using this method. An example

is the wire printer [ 1] where the wear on the thin wire tips is due to penetration

slip.

The wear of metal-plated plastic type depends on the ductility of the plating and

the bond strength of the metal-plastic junction [4] . When the ductility and bond

strength are sufficient, the abrasive action of printing can be evaluated by the same method as for solid metal type. Numerous cases for wear are listed in Ref, 4.

12k
Impact Wear Bel-ween Mechanical Componenl's

Repetitively impacting mechanical components often develop fretting wear which

is a hybrid mechanism. In a simple form of this wear mechanism the metal surface

would be oxidized and the oxide layer removed by successive impacts, which exposes pure metal; the process is then repeated, resulting in wear. When the tangential impact speed component is small (small oscillations are often possible due

to finite sideways constraints), the oxidized debris can remain for a longer period

of time in the contact area, and it assumes a protective role. A large tangentialimpact speed component tends to remove the debris that is generated. Thus, for

dry contact, the conspicuous difference between normal impact and sliding impact

appears to be manifested in the amount of "scrubbing action" involved. Another

way of accounting for differences between normal and compound impact is to consider the shear stresses caused by the two processes. The normal impact tends to cause subsurface damage, while the compound impact yields maximal shear stresses on the surface. In addition, slipping tendencies increase with the relative sliding

speed V. The two quantities which combine to cause wear damage are contact

stress and slip.

Studies of compound impact wear tests resulted in the observation of a "zero wear

limit," similar to the case of sliding wear [5] . The zero wear limit is reached in

Nq load cycles when the surface geometry has been distinguishably changed from

the original . This change has been arbitrarily defined as the depth of wear cor- responding to half the original peak- to- vol ley finish, i.e., h^ = 5/2.

An experimental-analytical investigation [1] found the following zero-wear formula for several steels and aluminum alloys impacted in the elastic contact stress range:

N = -i-^ . I2l \ . 2000 (6)

° 1 + P \ o /

^

'

In the above formula, P is the relative surface damage contribution, defined as the

ratio of surface damage to subsurface damage. The damage quantities are themselves time-integrals of the maximum surface or subsurface shear stress (t^ and T2

respectively), y is a wear factor, with a value of 1 . 1 for those steels referred to above, a 's the Hertz pressure.

After the zero wear limit has been determined, one point of the impact wear curve

is fixed. The curve, usually given in a double logarithmic graph of wear depth h

vs. cycle number N, can be established for the gradual wear processes with only one more constant outside of y; this can be the parameter c in Eq. (1).

125
At this point wear may be considered an impact-stress-dependent geometrical process, resulting in a gradually widening wear scar. For simple indenters (e.g.

sphere vs. plane) and a suitable contact theory (e.g. Hertz's), the widening of the

wear scar may be mathematically related to the number of cycles. The experimental

wear curves in a log-log representation show a typical slowly declining slope, and

this variation can be also shown by use of the theoretical model.

It is possible to express a nondimensional geometric wear-scar parameter in terms of

the number of cycles. The method found useful in the analysis of impact wear situations recognizes that the corresponding physical wear curves may be obtained by

shifting the nondimensional curves with the severity of the loading.

For example, consider the one-body wear of a "softer" plane by a hard (i.e. nonwearing) sphere of radius . The spherical-shaped wear scar on the plane may be

described at any stage of measurable wear by two geometric data. The nondimensional geometric parameter p = R^/R (where R is the changing meridional radius of

the wear-scar curvature) may be one of the two data. Another one of the two parameters (say the crater radius) will be completely dependent on p if the momentum

of impacts remains constant, and the impact stress continues to follow the Hertz

theory, we have the following relation for the hard ball vs. soft plane, based on

Eq. (1):

p/p

] +

1 + p

J

5

where Nq, p^ are the zero-wear-point coordinates. The conversion from p to "physical" wear depth h is, by use of geometry and Hertz theory:

h = - C p(l +p)"''' (8)

where

C = 0.77 {Vm^E^ R-; )'^^ (9)

and V is the impact velocity, m the mass, E^. the reduced modulus of elasticity.

For the various descriptive parameters (5, V, m, Er , Ri, etc. involving the surface,

the loading, the geometry and the material), not only is the zero-wear-point different, but, Cs the "scale" is also changed. Therefore, the typical slowly- level ling

impact wear curve can be basically shifted to the left with the increased severity of

wearing conditions. With this method families of impact wear curves can be

126
generated for a given industrial design situation. As a result, economically feasible,

competitive designs can be selected based on a predictive theory, reducing a long

and costly test period.

References

1. P. A. Engel, Impact Wear of Materials, Elsevier, New York, 1976.

2. P. A. Engel and R. G. Bayer, "Abrasive Impact Wear of Type," J. Lub. Tech.,

Trans. ASME, Vol. 98 (1976), pp. 330-334.

3. D. D. Roshon, "Testing Materials for Evaluating Wear by Paper," Wear, Vol. 30

(1974), pp. 93-103.

4. P. A. Engel et al., "Review of Wear Problems in the Computer Industry,"

ASME-ASLE Joint Lub. Conf., Kansas City, Mo., Oct. 1977; ASME Paper

77- Lub-4.

5. R. G. Bayer etal., "Engineering Model for Wear," Wear, Vol. 5, (1962),

pp. 378-391

.

127

SESSION IV

PRODUCT PERFORMANCE

- WHY CARE?

CHAIRMAN: M. R. MEYERSON

i NATIONAL BUREAU OF STANDARDS

i

i

HOUSEHOLD RETENTION OF CONSUMER APPLIANCES: USDA ACTUARIAL ESTIMATES

Marilyn Doss Ruff in and Katherine S. Tippett

Agricultural Research Service

U.S. Department of Agriculture

Hyattsville, Maryland 20782

Abstract: Methodology and results of USDA studies of appliance service

life, under one owner, are discussed. Since the 1950's USDA has estimated the retention period of most major appliances by means of actuarial or life tables constructed from ownership and discard data obtained

in nationwide household surveys. The most recent such estimates are based on a 1972 survey of 11,696 households and include seven major

consumer appliances: range, refrigerator, freezer, dishwasher, washer,

dryer, television. The best-known use of the actuarial or life table

method is, in estimating the life expectancy of persons in the population. The advantages of this method for estimating the service life

of appliances are that it minimizes the effect of trends in appliance

saturation and population change, minimizes the effect of year-to-year

variation in the number of units marketed, and reflects the experience

of units remaining in service as well as of those that have been discarded. For life study by the actuarial method, the product must have

been on the market long enough for the maximum life span to have

elapsed; there must be sufficient numbers in the population to provide

a reasonable sample; and the item must be of sufficient importance that

the owner-user will be likely to recall the date of acquisition.

Key words: Actuarial table; clothes dryer; consumer appliance retention; dishwasher; freezer; kitchen range; refrigerator; service-life

expectancy; television set; washing machine.

Since the 1950' s the U.S. Department of Agriculture has published actuarial estimates of the average "service-life expectancy", under one

owner, of major consumer appliances as part of a program of research

contributing to the understanding of family use of resources (1,2,3,4,

5,6,7,8). The estimates represent the period of retention by the

household rather than the mechanical life of the appliance and pertain

only to user-owned household items. Separate estimates were made for

equipment obtained new and for that obtained used. The most recent

such estimates were based on a 1972 nationwide survey and include seven

major appliances: range, refrigerator, freezer, dishwasher, washer,

dryer, television (7).

A number of conceptual and methodological problems had to be resolved

when USDA began the studies of service-life expectancy of household

151
appliances: how service life should be defined; choice of method for

estimating service life; and specification of population, both of

households and of appliances. Following a discussion of these questions

the resulting estim.ates and variation by household characteristic will

be presented.

Definition of Service Life

The first problem was to define service life in a way that would be

meaningful with respect to decisions families make about resources and

in a way that would be measurable. For budgeting purposes, families

need to know probable times of replacement for appliances. Families

often discard an appliance before the full potential for use is ex- hausted, so the mechanical life of the appliance is not the piece of

information that the family budget-maker needs. Families may replace

or dispose of an appliance because it has ceased to function and cannot

be repaired, or for a variety of other reasons: availability of new

convenience features, changes in equipment needs over the family life

cycle, a move to a new residence, or marginal or unreliable performance

of the item. Furthermore, to determine which appliances had exhausted

the full use potential and locate them and count them would be virtually

impossible. The definition of service life used in the USDA studies is

the expected period of retention by one owner—the time elapsed from

acquisition to removal from use. Removal from use was defined either as disposal by the household or storage of the appliance with no specific

plans for returning it to use. The length of the retention period can

be determined by questions that are direct, simple, and factual in

nature—no subjective evaluation of the future serviceability of the

discarded appliance is necessary. The service life or expected

retention period in the household was estimated separately for items

obtained new and items obtained used. Adding the new and used retention

periods will not yield the total mechanical life of the appliance,

however; some appliances remain with the original owner until the mechanical life is exhausted, while others may change ownership several

times. The retention period estimated by USDA pertains only to equipment owned and used by the same household, because an estimate based on family-owned items best serves family budgeting needs.

Method of Estimation

A second problem was how to make estimates that would be useful into a future period. The most direct way might be to use the average age of

currently-owned appliances or of appliances discarded during the previous year. However, both methods would bias the estimate toward a lower average age if there has been a long-term increase in the number

of households or in the proportion owning appliances; either increase

would result in over-representation of appliances of low age in the

sample. In addition, the average age of currently-owned appliances is

always somewhat lower than their age when taken out of service.

152
The method selected by USDA to estimate the retention period in the

household is the actuarial or current life table method. The estimation

procedure reflects the combined current experience of all age groups in

the appliance population; it reflects the longevity of those that

continue in service and of those that have been removed from service

during the recall interval. The best-known use of the actuarial or current life table method is in estimating the life expectancy of persons in the population. The method also is a valuable tool for the

study of consumer product data, because it minimizes the effect of

long-term trends in the number of households and the percent who own

appliances; minimizes the effect of year-to-year fluctuations in the

number of units marketed; and reflects the survival experience of

items remaining in service as well as of those that have been removed

from use. The life table is a convenient method for summarizing the

mortality experience of a population, providing concise measures of the

longevity of that population. Basically, there are two types of life

tables—the cohort life table and the current life table or actuarial

table. Both methods are based on observed probabilities of surviving

consecutive intervals of the lifespan. The cohort table is longitudinal, following a particular cohort (a group beginning life or other

condition at the same time) from birth (or onset of the condition) to

death (or termination of the condition) . The resulting life-expectancy

figure applies only to the one cohort observed; and, because the entire

population group must have lived out its lifespan before the cohort

table can be calculated, the method is useful mainly to those interested

in the historic perspective. The current life table or actuarial table,

which has been used by USDA to estimate the appliance retention period,

is a cross-sectional method. The estimation is based on the observation at one point in time (or in one time period) of many cohorts. The

"lif e"-expectancy estimate derived by that method reflects the combined

current experience of the many cohorts that make up the population.

Reference of application of the method to industrial equipment dates

back many years.

Study Population

Once the questions of definition and method were agreed upon, other

questions had to be resolved regarding the population of households to

be surveyed and the selection of appliances to be studied. For calculation of the expected household retention period for an appliance, data

are needed on the number in the appliance population that have been

discarded during a recent interval of time and the number that have

been retained in the household. Retention and discard information are

needed for each age group represented in the appliance population distribution in order to compute age-specific "survival" rates. The

survival rates are used to construct an actuarial table for a hypothetical cohort of appliances, whose total life is a composite reconstructed

from the various age groups' survival of the recall interval. Life

tables for the human population are constructed from census data, from

public records of births and deaths, or from insurance statistics.

155
Since no such sources of data are regularly available for the appliance

population, special surveys must be conducted in order to construct

life tables for appliances. The sample must be quite large, as only a small percentage of surveyed households (generally 5 to 10 percent)

will have discarded any particular appliance during a one-year recall

Interval, and the actuarial table calls for discard information on all

age groups in the appliance population distribution. In addition, there

is wide variation in the age at which appliances are discarded. Many

are discarded quite early in the life span, often in connection with a change in the household's place of residence; others are quite longlived.

For the collection of data from which actuarial tables could be con- structed with reasonable reliability and which would represent the

experience of all households in the country, USDA contracted with the

U.S. Bureau of Census. Most recently, a questionnaire was attached

to the July 1972 Quarterly Survey of Consumer Buying Expectations;

11,696 interviews were obtained. All households (renters as well as owners) were asked questions about appliances they currently owned or which they had removed from use within the past year. Even if a household did not currently own an appliance, interviewers were to ask about

the past year's removals so that results would reflect the experience

of all user-owned household appliances—not just discards due to re- placement. An owned item was considered to be currently in inventory

if it was in use in the household's main residence or was temporarily

out of service but intended for future use. Landlord-owned items were

not covered by the survey. For each appliance, the household respondent was asked if the household owned one; and if so, when had it been

acquired. In addition, certain appliance classification information

was recorded so that length of use for new and used items could be estimated separately and so that product characteristics (such as gas vs . electric, built-in v_s. portable or freestanding) could be considered.

Certain information about the household also was recorded.

Criteria for identifying appliances suitable for life study by the

actuarial method were established through methodological studies: the

product must have been on the market long enough for the maximum lifespan to have elapsed; there must be sufficient numbers in the population to provide a reasonable sample; and the item must be of sufficient

importance that the owner-user will be likely to recall the date of

acquisition (3). With these criteria, seven appliances were selected

for study in 1972: range, refrigerator, freezer, washer, dryer, dishwasher, and television. Service-life estimates had previously been

made for all but the dishwasher, but needed to be updated to reflect

the considerable changes that had occurred since the 1957-61 period:

marked increases in saturation levels for some appliances; the impact

of innovations such as frost-free refrigerators, self-cleaning ovens,

and color televisions; changes in family characteristics such as income

level, mobility, and employment of wives.

I5U
Estimated Service Life

Sufficient data were obtained from the 1972 survey to develop actuarial

tables and service-life estimates for 18 appliance categories (7,9).

The average service-life expectancy under one owner for items acquired

new ranged from a high of about 20 years for freezers to a low of about

11 years for black and white television sets and for washing machines

(see table)

Table — Selected Major Appliances: USDA Estimates of

Service-life Expectancy Under One Owner"'"

Appliance Obtained new Obtained used

1972 survey prior survey"^ 1972 survey prior survey'^

years years years years

Kitchen range

12 16 6 8

13 16 7 9

15 16 7 8

20 15 9 11

11 7 Washing machine^. 11 11 5 5

Clothes dryer:

14 14 5 Gas ^. 13

Television set:

Black and white 11 11 5 6

Color 12

Indicates how long, on the average, households keep each appliance —not how long the appliance could have been made to last. New and

used are not additive. Based on actuarial analysis of household survey

data.

Survey years: kitchen range, 1959; refrigerator, 1960; freezer,

1961; clothes dryer, 1961; washing machine, 1957; television set, 1960.

3 Freestanding only.

4

Built-in and portable.

^ Automatic.

" Excludes portables under 12 inches.

135
For items acquired used, the freezer again had the longest retention

period and the washing machine had the shortest. Although figures

suggest that gas ranges may have longer household service-life expectancy than electric ranges, and that electric dryers may be kept longer

than gas dryers, tests of significance did not reveal any differences

significant at the .05 level. Neither a pattern of lengthening nor of

shortening retention period was observed when results from the 1972

survey were compared with earlier USDA surveys. Estimates for four of

the seven items acquired new for which comparison was possible were

about the same as the most recent previous estimate. Two items—gas

and electric ranges —appeared to have a shorter retention period than

previously, and one item—the freezer —appeared to have a longer one;

however, these apparent differences were not significant at the .05

level. All items acquired used for which comparisons with earlier

years were possible had slightly lower service-life expectancies than

previously. However, these apparent differences were generally within

the range of 2 standard errors, and therefore individually not

significant; nevertheless, such uniformity in the direction of change

may indicate a trend toward a shortening period of use of used

appliances by one household.

Explaining Variation in Product Retention

The estimates from the 1972 survey that were published in 1975 (7) are averages for all households in the population, and of course conceal

considerable variation among families. The actual length of time that

individual families held on to their various appliances ranged from

less than 1 year to about 40 years. Data were insufficient for con- structing separate actuarial tables by family characteristics for individual appliances with reasonable reliability. The dilemma then was how to use what data that had been collected a) to see what characteristics of families might account for variation in the age of the discard, and b) to be able to make concrete statements about variation in

the period of retention by families with those characteristics.

Pooling standardized data for several appliances overcame the problem

of small sample size and permitted use of the actuarial method to

develop service-life estimates by family characteristics (8) . The

disadvantage of pooling data, of course, is that the estimate is not

as precise as an estimate for each appliance would be.

Prior to pooling, multiple regression was performed to learn how family

characteristics are related to discard behavior. The results were

examined to determine which appliances were similarly related to the

family characteristics and could therefore be pooled. Ages at discard

of major appliances —ranges, refrigerators, washers, dryers, and dishwashers—were found to be similarly related (as indicated by sign and

significance of b coefficients) to age of head, household income, and

whether the family had recently moved. The age of each owned and

discarded appliance was standardized and given a proportionate share of

the sample weight for the household. Data were then pooled into two

156
groups—one for appliances acquired new and one for appliances acquired

used; actuarial tables were constructed from the standardized, pooled

appliance age data for all households and for subsets having specified

characteristics. The resulting estimates of the household retention

period (service-life expectancy) for each subgroup were expressed as a percentage of that for all households. Confidence intervals were

computed to provide an indication as to whether the adjusted servicelife estimate for families with each specified characteristic differed

from the population average.

Results from pooled standardized data revealed several trends in variation by family characteristics. For appliances acquired new, the

greatest variation from the average retention period was among households that had moved in the 18 months prior to the survey; on average,

these households shortened the service life of their appliances by 60

percent, compared with all households. Estimated service life of

appliances owned by households that did not move in the 18 months prior

to the survey was more than three times as long as for households that

did move. Retention was shorter for households in which the head was under age 50 than for all households (about 20 percent less) and about

40 percent greater than the average among households whose head was

over 50 years. The least variation occurred by income groups, although

the service life of appliances owned by households with lower incomes

tended to be longer.

The pattern of variation for appliances acquired used was similar to

that of appliances acquired new although the amount of variation was

less, perhaps because the retention period was shorter.

References

(1) Jaeger, CM., and Pennock, J.L. Household service life of

appliances. Journal of Home Economics , 1957, 49^, 787-788.

(2) Jaeger, CM., and Pennock, J.L. An analysis of consistency of

response in household surveys. Journal of the American

Statistical Association , 1961, _56, 320-327.

(3) Pennock, J.L., and Jaeger, CM. Estimating the service life of

household goods by actuarial methods. Journal of the American

Statistical Association . 1957, 52^, 175-185.

(4) Pennock, J.L. Planning for the replacement of durable goods.

Talk at the Annual Agricultural Outlook Conference, U.S. Department of Agriculture, 1958. (Mimeographed copy available from

Consumer and Food Economics Institute, U.S. Department of Agriculture, Federal Building, Hyattsville, Md. 20782.)

157
(5) Pennock, J.L. Planning ahead for the buying of major equipment.

Talk at the 40th Annual Agricultural Outlook Conference, U.S.

Department of Agriculture, 1962. (Mimeographed copy available

from Consumer and Food Economics Institute, U.S. Department of

Agriculture, Federal Building, Hyattsville, Md . 20782.)

(6) Pennock, J.L., and Jaeger, CM. Household service life of durable

goods. Journal of Home Economics , 1964, ^56, 22-26.

(7) Ruffin, M.D., and Tippett, K.S. Service-life expectancy of household appliances: new estimates from the USDA. Home Economics

Research Journal , 1975, 3^, 159-170.

(8) Tippett, K.S., Magrabi, F.M., and Gray, B.C. Service life of

appliances: variations by selected family characteristics.

Home Economics Research Journal, 1978, 6^ (March 1978, forthcoming).

(9) U.S. Department of Agriculture, Consumer and Food Economics

Institute. Life tables for major household appliances—July 1972

survey. 1975. (Copy available from Consumer and Food Economics

Institute, U.S. Department of Agriculture, Federal Building,

Hyattsville, Md. 20782.)

158
APPLICATION OF HISTORICAL REPAIR DATA

IN LIFE CYCLE COSTING ANALYSIS

S. Wayne Stiefel

William B. Seine

Center for Consumer Product Technology

National Bureau of Standards

Washington, D.C. 20234

Abstract: Historical repair data are useful for estimating

life cycle costs as well as guiding development of life

cycle performance laboratory tests. A general model is

discussed which integrates available data for electric

clothes dryers to estimate repair costs. Results are

presented and their implications for various purposes are

considered. The applicability of the model and extension of

the technique to other appliances is also discussed.

Key words: Life cycle costing, repair cost analysis;

frequency of failure; electric clothes dryer

1. Introduction

Life cycle costing (LCC) has a long history of use by

the military and industrial sectors of our economy to

compare ownership costs for alternative products. The LCC

technique considers the total ownership costs and accounts

for the timing of cash outlays and the time value of money

in converting all costs to a present value [1] . A general

expression of the LCC formula can be shown as follows.

^ 1 1

LCC = PLC + E =^ [(OC). + (MTC), + (RC).] + ^ (DC)

t=l (1+r)^ t t t

(i+r)^^

present value of costs incurred during N periods,

consumer's initial price and logistics (i.e., transportation and installation) cost,

discount rate (per period)

,

operating (energy, water, etc.) cost for specified

maintenance, repair, and use conditions,

maintenance cost,

repair cost, and

disposal cost (This item becomes negative if a

where

,

LCC = PLC =

r = OC =

MTC = RC = DC =

139
consumer received money when disposing of an old

product .

)

The widespread use of LCC analysis for weapon systems

and plant equipment by the military and industry may be

attributed to their control over operation, repair and

maintenance as well as their record keeping activities. A

similar observation cannot be made for consumer products.

The application of LCC to consumer products is new.

Application to consumer products to date has concentrated on

combining energy costs with purchase price ignoring other

costs, such as repair [2] . The reason repair costs have

not been included is in large part due to the lack of data

and the difficulty in obtaining repair cost information,

especially beyond the warranty period. This paper will

present a repair cost model suitable for estimating

appliance repair rates and their associated costs and will

illustrate the model's use on a major consumer durable, the

electric clothes dryer.

Repair rate and cost estimates have multiple purposes.

In the context of LCC analysis it is possible to examine the

importance of repair costs relative to total ownership

costs, to examine the variability and sensitivity of cost

estimates to machine and non-machine related parameters and

to provide a basis for translation of failure rate data to

estimated repair costs. Because LCC information is needed on

appliances at time of purchase and yet these appliances will

be in use for more than ten years, accelerated testing under

controlled laboratory conditions is a possible approach to

estimate failure rates. Two underlying problems associated

with accelerated testing involve the uncertainty that

results are representative of actual experience and the

scaling factor between laboratory time and field use time.

Therefore, estimates of failure rates on similar machines

provide useful information for directing the development of

test methodologies. Specifically historical repair data

provide

® estimates of expected failure rates and average

time to first failure,

9 indication of most frequent repaired components,

and

• a means for translating laboratory results to the

consumer's environment.
2. Repair Data Sources and Requirements

Potential sources for appliance repair data include

manufacturers, consumers and repair agencies. Manufacturers

are reluctant to provide repair data either because their

records are not adequate beyond the warranty or the possible

advantage it may offer to a competitor.

Consumers of appliances were also investigated as

repair data sources. The individual purchaser generally

does not keep good records and use of recall for extended

periods is not accurate. Aggregate data based upon an

extensive survey of many thousands of consumers over a short

recall period was not feasible. However, future analysis of

the Department of Labor Statistics Consumer Expenditure

Survey data tapes (soon to be available) may provide

aggregate repair data. Large institutional purchasers, such

as the Federal Government, local housing authorities,

laundry companies and apartment complexes, generally do not

have data at the level of detail required. However, many

organizations expressed their willingness to collect data

for future analyses.

Repair agencies proved to be the most fruitful source

for data, particularly the repair organizations located in

utility companies. The utility company's customers

typically buy the machine from the utility, purchase a longterm service contract and continue to rely on the company

for service after the service contract terminates. Utility

companies, having a high proportion of units under service

contract, maintain complete well kept records for purposes

of providing service and analyzing their costs for providing

the service.

The repair information being sought during data

searches consisted of a continuous set of records from

installation through disposal including for each machine:

• make and model.

date of installation.

® warranty or service contract status,

« date of repair,

description of repair,

f> part numbers.

• labor time , and

• cost.

Based upon the information located during the search an

expected repair cost model was developed which integrates

the available data. Although records exist which provide

the time trace of repairs, their collation from company files
involved approximately one-half hour per machine.

Obviously, for a large sample size this longitudinal

approach is very expensive. The repair cost model permits

use of either cross sectional or longitudinal data sets.

Cross sectional data provide information on machines of

various ages repaired during a one or two year period. For

the purpose of exercising the repair cost model a combination of cross sectional and longitudinal data were

used. The longitudinal data were obtained from a master

chronological file for consumers maintained for over 15

years. The chronological record contained information on

date of purchase, date of repair, warranty and service

contract data and possibly date of- repurchase. The cross

sectional data consisted of repair records containing the

detailed information on manufacturer and model, machine age,

cost of repair, warranty status, labor time and a description of repair procedures. The description of repair

procedures included the:

1. action taken (e.g., installed, adjusted, replaced,

repaired, cleaned, lubricated, etc.),

2. major subsystems affected (e.g., electrical, drive

system, drum assembly, blower assembly,

cabinet/console, etc.),

3. components affected (e.g., heater element, timer,

motor, etc.) and

4. part costs if parts were replaced.

3 . Expected Repair Cost Model

The following cost equation was derived to construct a distribution of expected annual repair costs over a prescribed number of years of operation. The equation

specifies the data required and is in a form consistent with

repair records of many repair firms.

:.(C) = E R. . • (ST.. • SR. + PC.) j = 1,2,. ..,t.

where

,

E . (C) = expected repair cost for the jth year of

^ operation (year since purchase)

f

R^j = number of repair procedures i divided by the

number of units in their jth year of operation.

1^2
= average service time per procedure i in year j

,

SRj = service fee per unit of service time in year j ,

PC. . = average part cost associated with procedure i

in year j .

The model is flexible and allows for gauging the sensitivity

of repair costs as a function of different values for the

repair rates, labor and parts cost parameters.

3.1 Repair Rates

It must be emphasized that the intent of this paper is

to demonstrate the application of LCC to electric clothes

dryers and only to illustrate the process for

characterization of repair costs for this appliance.

Consequently, emphasis was placed on developing methodology.

Requirements for a statistical sampling of repair data that

could provide the repair cost characterization were relaxed

to facilitate this approach. The results which follow are

based upon relatively few repair agencies and brands and

therefore are not meant to be representative for the

electric clothes dryer as a class.

Repair rates provide measures of the incidence of

repair relative to the number of units in operation. They

are derived from repair records and, as such, may exhibit

characteristics stemming from decisions that determine

repairs. Unlike failures, defined by established

substandard levels of performance, the existence of a repair

record is the result of a decision by the owner or user of

an appliance to seek the services of a repair firm. This

decision is predicated on the user's perception of an

abnormal symptom and the influence introduced by the

presence of external variables, such as cost, inconvenience,

within warranty period, among others. These influencing

factors are observable but extremely difficult to quantify.

The influence of warranty on repair rates for televisions

and refrigerators is discussed in a report by the

Massachusetts Institute of Technology [3] . The authors of

that report claim repair rates during warranty are inflated

beyond that normally attributable to strict machine failure.

According to the authors, calls "of the education type" or

nuisance calls make up about 30 percent of all warranty

service calls. Further, other service center practices,

according to that report, tend to raise the repair rate even

higher than expected.
A second factor influencing repair rates is the 5-year

service contract. The influence of this factor is

demonstrated in repair rates provided by company B. These

rates, shown in figure 1, correspond to two time periods.

The first period is for units operating in the 2nd through

5th year prior to implementing a 5-year service contract.

During this period the rates are relatively constant,

averaging 0.26 repairs per unit per year. The second period

involves dryers with 5-year service contracts. These rates

begin at the level of previous period but dramatically and

continually increase to 0.46 in the last and final year of

the 5-year service contract. The average repair rate is

0.33 repairs per unit per year for a 27% increase in the

average repair rate between the two sets of repair rates.

FIGURE 1 REPAIR RATES FOR ONE BRAND OF ELECTRIC DRYERS SOLD AND SERVICED

BY COMPANY B PRIOR TO IMPLEMENTING A S-YEAR SERVICE CONTRACT

AND FOR YEARS IMMEDIATELY FOLLOWING FOR DRYERS SOLD

WITH A S-YEAR SERVICE CONTRACT

.40

.30

I-<

.10

*

• * • * • •

PBIOR TO INITIATING 5-YEAR • SERVICE CONTRACT

AFTER IMPLEMENTING 6-YEAR

1 1 1

*

1

SERVICE CONTRACT

1 2 3 4 5 6 YEAR OF OPERATION The repair rates computed from the repair frequency

data obtained from company A also exhibit these

characteristics. These rates are displayed graphically in

figure 2. Consistent with the previous data, the first year

rate is high and rates for the 2nd through 5th years of

operation increase more rapidly than the overall average

increase. This 2nd through 5th years increase, in part, is

possibly due to the 5-year service contract since all dryer

sales made by company A after approximately 1963 included a 5-year service contract. The linear fit of the data was

included to reduce this effect.

Ikk
FIGURE 2 REPAIR RATE VERSUS YEAR OF OPERATION

(RATES ARE FOR ALL MODELS OF THE SAME BRAND

SERVICED BY COMPANY A)

.15

.10

.05

• OBSERVED RESPONSE

X- PREDICTED RESPONSE

J I I I I I I I I L

1 23456789 10 YEAR OF OPERATION

Repair rates vary between brands and repair firms. For

example, the fifth year repair rates were 0.4 6 for company B

and 0.13 for company A.

Different levels of repair rates between 3 major brands

of electric clothes dryers are also indicated in first year

(warranty) sales and repair data provided by company C.

These repair rates, shown in table 1 are for the 12 months

of 1976 and first 7 months of 1977. Repair rates vary

slightly across years for each brand. However, the repair

rates for Brand III differ considerably from Brands I and

II.

Table 1. First year (warranty) repair rates

for three brands of electric dryers

serviced by company C

Year

Repair Rate s Brand

I

Brand

II

Brand

III

1976

1977

(7 months)

0.22

0.22

0.20

0.18

0.12

0.12

lJ+5
There is agreement in the year-to-year pattern of

repair rates between data provided by the three companies.

There is also evidence that repair rates are influenced by

external factors such as warranty and five-year service

contracts. Finally, repair rates differ between brands and

different repair firms.

3.2 Results of Sensitivity Analyses on Expected Repair

Costs

This section will address the effects of observed

variations in the parameters of the repair cost model on the

expected annual repair costs. The expected costs are more

affected by changes in some parameters than others. The

repair costs which follow exclude the first year of

operation, which are absorbed by the manufacturer and passed

back to the consumer through the initial purchase price.

Thus the consumer's expected annual repair cost would be

those of the second and successive years of operation. The

repair rate has the greatest influence over expected costs,

given the same percentage increase in each of the parameter

values. Figure 3 illustrates the possible effect of the

extremes in expected annual repair costs resulting from

observed differences in repair rates between firms. The

lower value ($3.57) represents a ten year average (2nd

through 10th year of operation) for the repair rates

observed in figure 2. The calculated average values were

nearly constant ranging from $3.47 in year 2 to a high of

$3.65 in year 5. The higher value in figure 3 ($11.21)

results from averaging the repair rates indicated in figure

1 for the 2nd through 5th year of operation and holding the

remaining cost parameters constant.

FIGURE 3 EXTREMES IN EXPECTED ANNUAL REPAIR COSTS RESULTING FROM OBSERVED DIFFERENCES IN REPAIR RATES BETWEEN

REPAIR FIRMS

Ei(C)-$3.57

3 4 5 YEAR OF OPERATION

lk6
In addition to observed differences in repair rates,

table 2 indicates the extremes in parts costs and service

charges for labor time observed during a survey of nine

repair firms [4] . Using these values as an index relative

to the base case shown in figure 3, the expected annual

repair costs attributable to variations in service fees and

parts cost were computed for years 1 through 10. These

average annual repair costs are shown graphically in figure

4. The value of $3.71 corresponds to the $3.57 value shown

in figure 2, but includes $4.92 for the first year of

operation

.

Table 2. Parts cost and service charge variability

Average Part

Costs Based on

Hourly A Selected Set

Service Fee of Parts

Low $15.00 $ 8.73

High $47.50 $16.20

FIGURE 1 EXTREMES IN EXPECTED ANNUAL REPAIR COSTS AS A RESULT OF

OBSERVED DIFFERENCES IN PART COSTS AND SERVICE FEES

(REPAIR RATES ARE NOT VARIED)

i 6.00

< 4.00

E|(C)-ie.82

• E|(C)ii«3.71

E J (0^.80

-I 1 1 L 1 I 3*56789I I 10 YEAR OF OPERATION

The extremes of $2.80 and $5.82 reflect their

respective low and high service fee and parts cost shown in
table 2. The repair rate was held constant for all three

values in figure 4.

4. Application of Historical Repair Data

to Test Method Development

Historical repair data have application beyond LCC

analysis. They provide useful information for guiding the

development of laboratory tests. Estimates can be derived

for expected failure rates and average time to first

failure. They also can provide indications of the most

frequently repaired components, a means for translating the

results of laboratory testing to the field environment and

guidance in determining acceptable levels of accuracy.

4.1 Failure Rate and Average Time to First Failure

Repair rates are measures of the incidence of repairs

relative to the number of units operating in year j . These

rates are derived from repair records which in turn exist as

a result of decision processes invoked by consumers to

repair. External factors exist that influence these

processes (e.g., existing warranty and extended service

contracts) . In instances where the influence of these

factors can be quantified and ultimately subtracted out of

the repair rate estimate or where their influence is simply

not substantial, repair rates provide reasonable estimates

of failure rates.

Table 3 provides estimates [5] of failure rates for the

first ten years of operation. Also shown are values which

indicate the probability that the first failure occurs in

year j. An average time to first failure of 7.3 years has

been derived for this sample by extrapolating the failure

rate for 20 years and terminating the survivors at the 21st

year

.

IkQ
Table 3. Failure rate and probability of first failure

estimates based on data obtained from Company A.

Year of

Operation ( j

)

Estimated

Failure Rate*

Estimated Probability

of First Failure

1 0.133 0.133

2 0. 096 0.083

3 0.100 0. 078

4 0.105 0.074

5 0.110 0.069

6 0.114 0.064

7 0 . 119 0.059

8 0.124 0.054

9 0.129 0.050

10 0.133 0.045

*Based on a linear fit of the original data.

This value can be placed in more useful terms by

incorporating results of other studies. A field study of

clothes dryer usage found that dryers are used at a rate of

7.1 loads per week [6]. This value was applied to the

average time to first failure as follows:

^ ^ _ T loads 52 weeks near: 7.3 years x 7.1 ^^^^^ x y^^^ = 2695 loads.

This value is an estimate of the average number of loads to

first failure. The validity of this estimate is related to

four assumptions:

(1) The average number of loads per year estimate is

valid over all years of operation.

(2) The expected number of repairs is a function only

of the number of loads.

(3) The repair rate is a good estimator of the failure

rate

.

(4) Repairs occur independent of previous history.

The average time to first failure can be expressed another

way, that is, in terms of hours of use. The operating time

per dryer load is required for this transformation. An

estimate of operating time has been derived from two studies

which provide dryer performance estimates [7] and energy consumption per load estimates [8]. The estimate derived is

lk9
28.5 minutes per load. The average use time to first

failure can then be estimated as follows:

o^nc 1 J no c minutes hour noon u 2695 loads x 28.5 -^j 3 x . = 1280 hours. loads 60 minutes

Thus, for each 1280 hours of operation, one failure would be

expected

.

4.2 Most Frequently Repaired Components

The repair procedure data provide informatibn at the

component level. This information is essential to compare

the laboratory setting as a surrogate for field conditions

and use environment. A percentage distribution of repair

procedures by affected system and component is shown in

figure 5.

FIGURE 5 PERCENTAGE DISTRIBUTION OF REPAIR PROCEDURES

BY AFFECTED SYSTEM AND COMPONENT

(1677 OBSERVATIONS)

In addition for each component the type of repair

performed can be provided. Figure 6 is an aggregate

distribution of types of repairs performed on the entire

electric clothes dryer system.

150
FIGURE 6 PERCENTAGE DISTRIBUTION OF REPAIR PROCEDURES

BY TYPE OF REPAIR

4.3 Translating the Results of Laboratory Testing to the

Consumer ' s Environment

Laboratory test data to be of value in consumer

decisions must be put into appropriate units. This process

can be thought of as the reverse of that previously

discussed in section 4.1. It also has implications for LCC

analyses. For example, the frequency of a specific

component failure can be determined in laboratory testing.

How this affects the repair cost is determined by merging

these test data with field parameters, such as, usage

patterns, service fee per unit of time, part cost, and

average time required to perform the appropriate repair

task. A histogram indicating the distribution of service

times, averaging around one hour, to repair the aggregate of

repair procedures is shown in figure 7. A similar histogram

can be generated for each repair procedure (e.g., replacing

a belt) . Integrating these data with laboratory results can

provide estimates of expected repair cost.

151
FIGU;€ 7 HISTOGRAM FOR THE DISTRIBUTION OF SERVICE TIMES PER REPAIR

200

i 150 <>

UJ

185 185

100

50

171

MEAN=62.4 MINUTES

83

74

45

50

18 16

12 13 „ ,

,

15 30 45 60 75 90 105 120 135 150 165 180 195 >195 SERVICE TIMES PER REPAIR (MINUTESl

5. LCC Analysis for Electric Clothes Dryers

In the introduction to this paper the LCC formula was

presented. The LCC formula consists of initial purchase

price plus the discounted values for operating, maintenance,

repair and disposal costs. For electric clothes dryers

maintenance and disposal costs are negligible compared to

the other ownership costs. The average purchase price was

$227 in 1976 [9] and the operating cost reduces to energy

consumption cost. Based upon 7.1 uses per week and a value

of 2.4 3 kWh per use [10], the average annual energy

consumption is 897 kWh. Using electricity costs of 4<: per

kWh the average annual energy cost is $36. Therefore, the

ten year ownership cost picture involves an initial outlay

of $227 and annual expenditure of $36 for energy and $3.57

for repairs in years 2 through 10 [11] . Figure 8 indicates

the relative share of ownership costs attributable to

purchase, repair and energy costs at a 5 percent discount

rate. Repair costs only contribute 4 percent and are

dominated by energy costs and purchase price. Certainly

these relative costs have implications for the type of

information which should be emphasized to consumers, as well

as the level of accuracy necessary in characterizing repair

versus energy costs in laboratory testing. Even doubling

the repair rate, as shown in the figure 8 pie chart, only

152
increases the repair cost share to 9 percent. Repair costs

are also insensitive to variations in discount rate. At a zero discount rate the repair cost share increases by one

percent while at a 10 percent discount rate the repair cost

contribution decreases by one percent.

FIGURE 3 DISTRIBUTION OF ESTIMATED TEN YEAR

OWNERSHIP COSTS FOR ELECTRIC CLOTHES DRYERS

(USING A 5% DISCOUNT RATE AND ENERGY COST OF 40/KWH)

BASED UPON ONE DOUBLING REPAIR COSTS COMPANY'S REPAIR DATA

6. Conclusion

Historical repair rates and cost estimates have

multiple purposes. Using LCC analysis it is possible to

ascertain the importance of repair costs relative to total

ownership costs, to examine the sensitivity of cost

estimates to variations in machine and non-machine related

parameters and to provide a basis for translation of failure

rate data to estimated repair costs. Analysis of repair

frequency data indicated general agreement in the year-toyear pattern of repair rate between three different

companies. There are also indications that repair rates are

influenced by external factors such as warranty and service

contracts and that repair rates differ between brands and

repair firms.

The repair cost model is applicable to major household

appliances and permits not only computation of a

155
distribution of expected annual repair costs, but also the

flexibility to observe the effects of variations in the

parameters values of repair rate, service fees and parts

cost on expected repair costs. Since the repair data

sources located for electric clothes dryers can provide

information on other major household appliances, the

techniques developed could be extended to these appliances.

Historical repair data have application for guiding

development of laboratory based testing. Estimates can be

derived for expected failure rates by component and average

time to first failure. Using usage pattern data together

with failure rate estimates it is possible to translate from

the field use (calendar) time to laboratory (operating)

time. Finally, the use of the LCC approach permits a comparison of the relative share of ownership costs

attributable to purchase, repair and energy consumption.

These relative costs have implications for addressing the

required level of accuracy of test methods intended to

generate repair or energy cost estimates.

r
7. References and Notes

[I] Grant, E. L. and W. G. Ireson, Principles of

Engineering Economy , 5th ed., Ronald Press, New York,

1970.

[2] Stiefel, S. W. , S. J. Kim and H. Hung, Life Cycle Costing:

An Assessment of Practicability for Consumer Products , NBSIR 77-1212, December 1976, p. 15.

[3] Center for Policy Alternatives, The Productivity of

Servicing Consumer Durable Products , Massachusetts

Institute of Technology with the Charles Stark Draper

Laboratory, Inc., Report No. CPA-74-4, 1974, p. 93.

[4] The study was limited to nine firms because of time constraints involved with securing Office of Management and

Budget approval to exceed nine firms.

[5] An intrinsic assumption is that the sample is truly

representative of the respective population. The sample

used in this study was adequate for the purpose of this

study but, since it represents a single repair firm, may

not be adequate for predicting time to first failure.

The procedures used, however, are valid.

[6] Proctor and Gamble, field study results submitted to the

Federal Energy Administration "Appliance Proposed Energy

Efficiency Improvement Targets," June 10, 1976.

[7] Consumers' Research Magazine , "Electric clothes dryers,"

July 1975, p. 7.

[8] Oklahoma Gas and Electric Company, "Field Study

Electric Clothes Dryer Energy Consumption," 1971.

[9] Merchandising , "1977 Statistical and Marketing Report,"

March 1977, p. 60.

[10] Oklahoma Gas and Electric Company, loc . cit .

[II] The base case value of $3.57, as shown in figure 3, was

chosen for the purposes of illustration. However, the

above caution (see note 5) also applies here.

155
ENVIRONMENTAL AND

ECONOMIC IMPACTS OF PRODUCT DURABILITY AND LIFE

P. L. Fontaine

Stevenson & Kellogg, Ltd.

Ottawa, Ontario, CANADA

Abstract: The economic and environmental impacts of increasing the

durability of major domestic appliances and automobile tires in

Canada were assessed. Increased durability was also compared to

other major alternatives such as recycling and reuse. Energy, solid

waste, resources consumption, air and water pollution, employment

and industry sales were considered. Also, approaches which the

federal government might follow to affect product durability were

evaluated. Basic data were developed by examination of published

data, through personal interviews with members of a wide range of

related organizations, manufacturers, distributors, reconditioners,

commercial users, etc. , and from a national consumer survey conducted to establish how and why people dispose of major appliances.

The study concluded that increased durability is practical and does

decrease materials and energy usage for passenger car tires. However, the same comments cannot be made for major appliances for a

number of reasons. These reasons include the difficulty of insuring

that increased durability will in fact be used by consumers and the

lack of hard technical data on the materials and energy costs of increasing appliance durability.

Key words: Environmental impact; appliance durability; tire

durability.

In this study the implications of increasing the life of the following

products were evaluated:

Electric ranges and microwave ovens;

Refrigerators and freezers;

Automatic clothes washers and dryers;

Home air conditioners;

Automobile tires.

156
In particular, we studied the effects of increased product life on:

Energy consumption;

Consumption of resources;

The environment;

The economy.

The project was split into four sections:

1 . Gathering Public Data

In this section, data were obtained from published sources, and

by discussion with public bodies -- departments of the governments of Canada and the U.S.A.

2. Field Research

We interviewed a wide range of people involved in the manufacture, use, and disposal of these products. These sources

included:

Relevant associations, including major tire and appliance

associations in Canada and the U.S.A.

Works departments, including those of most of the major

metropolitan centers in Canada.

Major manufacturers and distributors of tires and appliances.

Service organizations, reconditioners, and major users.

Industry experts and others.

3. Consumer Survey

A national consumer survey was conducted to assess:

the proportion of appliances which replaced a previous model;

the disposition of the previous appliance.

157
4. Analysis of Relationships and Impacts

The environmental impacts and other relationships were

analyzed and approaches were discussed with the representatives

of the various government departments involved.

From the analysis, it was concluded that increased durability is

practical and does decrease materials and energy usage for passenger car tires. However, the same statement cannot be made

for major domestic appliances because:

The impact of consumer behaviour is much more important.

We cannot be sure that the increased durability will be used.

There is a lack of hard technical data on the materials and

energy costs of increasing the durability of appliances.

Major Domestic Appliances

About half of all new appliances are purchased to replace old appliances. The majority of the replaced appliances are retained in use. When they are finally disposed of, about 70% of appliances

are send to landfill, the remainder are recycled. Appliances contribute approximately 1% to total residential and conmiercial landfill by weight.

Appliance manufacturing uses around 1% of Canadian production of

steel, polyethylene and polyvinyls. It consumes about 0. 14% of

Canadian energy production. Appliance manufacturing uses less than

one- fifth of the steel used by the fabricated structural steel industry.

Appliances use less than one-tenth of the steel of the Canadian motor

vehicle industry.

The main source by far of energy consumption and environmental

pollution during the lifetime of washing machines (which we looked

at in detail) was derived from the energy production necessary for

the heating of the water used. The average automatic washing

machine uses four hundred fifty tons of hot water in its lifetime.

The energy used to heat this water is approximately fifty times the

energy used to make the washing machine.

158
In the last fifteen years there has been little change in the recorded

durability of appliances. However, the available data are only for

the "first owner" lifetime, such that the ultimate durability of appliances through second and third-hand ownership is not readily apparent. Servicemen report, though, that the number of appliances

rebuilt for sale second-hand has recently been declining, partly due

to the fact that appliances are becoming less durable. However, this

observation was not substantiated in our study in any statistical way.

The cost of appliances compared to total consumer income decreased

nearly 50% between 1966 and 1974. The cost of repairs relative to

the price of new appliances has increased sharply as a result. Consequently, the economics of rebuilding appliances have recently

become very poor, and the market has thus become almost non-existent.

The most frequent failures in washing machines occur in pumps,

switches, agitators and transmissions. A major cause of failure

is seized bearings in pumps and transmissions. Bearings are also

a problem in motors.

The useful life in terms of cycles performed is nearly three times

longer for commercial washing machines than domestic machines.

However, the mechanics of both types are nearly identical. The

different usage obtained is partly the result of better maintenance in

the commercial environment, and partly a greater propensity to

repair the commercial machines rather than purchase new ones.

Consumer behaviour has a major influence upon appliance life. In

particular, for washing machines, excessive or imbalanced loads

cause increased wear. Other factors which alter the life of a washing

machine are the detergent used, water chemicals, and the temperature selected.

We conclude in this study that:

Appliances do not consume a significant proportion of Canada's

resources during their manufacture. However, the consumption

can be economically and effectively reduced by recycling through

scrap metal shredders.

159
Durability has a low priority with consumers. This, we believe,

is largely due to the fact that most appliances already last about

ten years. The perceived present value to the consumer of additional durability whose benefits will not be received for ten years

is low.

Consumers know very little about durability. There are no

comparative tests to guide them. (It is very difficult to compress a ten year life into a reasonable length of time for a test. ) Hence, they are guided by the apparent visual quality and the

brand's reputation.

Automobile Tires

Tire manufacturing uses 65% of all the rubber consumed in Canada.

It also uses about 0.4% of Canadian energy production. This is

nearly three times the energy consumed by appliance manufacturing.

However, nearly half of that energy can be saved through tire reclamation.

The durability of tires has increased considerably in recent years.

This is principally due to the trend toward radial ply tires. Of the

three main types of automobile tires -- bias ply, belted bias, and

radial ply -- the radials give the highest mileage.

Radials provide a significant reduction in materials used per 1,000

miles of driving. This saving is due to their increased durability,

despite the higher consumption of materials and energy during

manufacture. Because radials are more expensive, the cost to the

consumer per 1, 000 miles is comparable or higher than the other

types of tire. However, this cost is offset by the reduced fuel consumption resulting from their low rolling resistance.

The tread life achieved by a set of tires is closely related to the way

that they are driven. "Hard" driving with sharp acceleration and

braking reduce tread life drastically. Conversely, smooth driving

increases tread life, obtaining up to three times the tread life of

hard driving.

Tire maintenance also affects tire durability. Incorrect inflation,

especially under- inflation, shortens tread life considerably. It also

reduces the value of the carcass for re- capping purposes, as the

i6o
walls may be seriously damaged. Other maintenance, often neglected, includes correct suspension set-ups and tire rotation.

The majority of the materials in a tire are in the carcass. Recapping

enables these materials to be re- used, hence increasing their useful

life and effectively reducing the materials and energy used per 1,000

miles of driving. Unfortunately, to date the availability of sound

carcasses has been limited because there is little incentive for users

to return old tires, sound or otherAvise.

Nearly 50% of the energy in a tire can be recovered by thermal

cracking. This process can produce a gas suitable for burning, a

fuel oil fraction, and char which can be re- used in tires.

We conclude that:

Tires are a better subject for government action than appliances because they consume more energy, their manufacture

is simpler to regulate and influence, and their durability can

be much more explicitly measured.

There is little evidence that the tire companies can improve the

durability of their best tires without adversely affecting other

desirable features such as safety and "ride".

The use of the top quality radial ply tires should be encouraged

as they cause less energy to be consumed and use less material

per 1, 000 miles of driving.

Contract Authority

This study was carried out under joint contract to the Department o£

Fisheries and Environment (Waste Management Branch) and the Department

of Energy, Mines and Resources o£ the Government of Canada.

l6l
I
SESSION V

PANEL DISCUSSION:

CAN AND SHOULD PRODUCT

LIFE BE EXTENDED?

CHAIRMAN: E. PASSA6LIA

NATIONAL BUREAU OF STANDARDS
I

I

1

I

i
INTRODUCTORY REMARKS TO PANEL DISCUSSION -- CAN AND SHOULD PRODUCT LIFE BE EXTENDED?

William E. Davis

Office of Technology Assessment

Congress of the United States

Washington, DC 20510

Introduction

I am by training and inclination a behavioral scientist; thus the

perspective I bring to this panel is from the human point of view. That

is to say, the point of view of the scientist of human behavior -- since

I assume that all of us here today are to some degree human.

The behavioral sciences, which more or less encompass anthropology,

psychology, and sociology, seek to provide an objective description and

analysis of behavior -- both individual and social. I have assumed my

appearance today is to see if any of these disciplines can shed light on the issues of the Symposium. I think they can and I hope to share some

of my ideas with you.

Declaration of Ignorance

Since it is customary for foreigners entering a new territory to protest

their ignorance, I shall begin by emphasizing that I know nothing about

your areas of technical proficiency. Indeed, in my own professional

jargon, "stress" is what occurs when you get too many white rats in a cage or too many people in a big city; a "clutch" is something you get

into when it's fourth down and you are only three yards from a first;

and "abuse" is measured by the number of times you beat your wife or children and tends to be independent of maintenance.

Having thus declared my ignorance, I feel free to plunge ahead and

express my opinion about anything and everything I have heard during

the Symposium. I also view my ignorance as license to ignore the Panel

Chairman's request that we address issues of importance.

On the Nature of our Knowledge About Human Behavior

I want to stress one thing about the state of our knowledge of human

behavior. To state the situation kindly, our understanding is at best

meagre. We really know very little about how and why individuals and

groups behave; to be sure, there is an abundance of hypotheses, a plethora of speculation, and even a few pockets of hard data. The state

of our science, however, is far from being able to predict behavior even

when we have a good understanding of the forces operating in a given

situation

.

165
Thus I will offer you no sure answers today. Instead I would like to

offer some suggestions about a few of the factors which play a role in

product usage, which may influence durability, which influence how we approach these topics, and which I believe should be remembered when we approach the technical questions at hand.

Some Dangers of False Categorization

The first factor that I would raise has to do with the placing of

individuals in categories. In the normal discourse of life, we must of

necessity sort out those with whom we come into contact; we do this

using various common characteristics. So it is we treat ladies differently than ruffians and children differently from grown-ups.

A careful analysis of behavior, however, must examine these categories

to verify their importance. Let me cite a few examples.

We have heard several references to a little old lady in tennis shoes

who only drives her car to the supermarket and to church. The example

conjures up a certain class of product users. I suggest that there

needs to be an empirical check on whether there are such people, and

if so just exactly how they do handle their cars.

Similarly the general category of "consumer" has been used. I suggest

that this is a most unusual way to lump people and the sooner the class

labeled "consumers" is broken down into more meaningful categories, the

better off we all will be.

There are retail consumers, industrial consumers, affluent consumers,

poverty-stricken consumers -- and each manifests significantly different

kinds of behavior. If we must use the label "consumer," then the least

we can do is qualify the usage with some additional descriptive

attributes.

You yourselves have admitted that you drive your cars for years. You

are therefore a very peculiar category of consumers. You should refer

to yourselves as "professional consumers", or "weird consumers", as the case may be. There are differences in consumer behavior as a function of whether or not the individuals are ladies or ruffians, young

or old, rich or poor, professionals or weirdo's. Not to include these

important qualifiers obscures essential information.

When it comes to categorizing people or groups we must be sure we are using reasonable and relevant criteria for that categorization.

Related to this is what I see as a need for greater communication between the real categories of consumers which exist in society and those

who supply those groups. I have no ready means to increase this

166
contact, but I do believe that some of the problems which I am con- vinced arise from false categorization might evaporate if we purged

ourselves of our false groupings.

On the Importance of Perception

The third factor which I would like to stress relates to how we view

the world. One of the most intriguing qualities of human beings is our ability to take raw information and process it -- the results of that

processing constitutes our perceptions.

There is a fundamental importance to the distinction between objective

reality and to an individual's or a society's perception of that reality. Again a few examples.

I would suggest that in our culture, both consciously and unconsciously,

we have equated "new" with "good" and "not new" with "not-so-good." I have heard from you that if we are going to save materials and energy

and yet retain a decent life, we must depend more and more on re-cycled

and remanufactured goods. We are also going to have to get used to

keeping things around much longer. But I suggest to you that there are

a lot of people in this country who are going to be uncomfortable doing

this because of the way they perceive "not-so-new" products. Many of

us are suspicious of used-car dealers (especially former ones) and we

are reluctant to buy from them.

In other words, regardless of the objective quality of products, so long as they are perceived as "second-hand" they will not be as welcome

as "new" products.

In a similar vein, so long as new models of anything are perceived as endowing their owner with prestige, they are going to be more valued

than older models.

Again I have no quick or certain solutions to go about changing perceptions. But, believe me, until our perceptions are changed, it will be

a long haul before products with long-lives will be generally accepted.

Values and Facts

My final point is to raise the issue posed by the title of today's

discussion: "Can and Should Product Life be Extended?" The "can" part

really is your area -- that is to say, "Can it be done?" is a question

to be answered by technical analysis.

The "should" part is everybody's business.

167
I am sure that you recognize this as the traditional distinction between values and facts. Whether or not a product's life can be

extended is a matter depending on our knowledge about the properties

of that product and the factors bearing on its degradation. These are matters of fact.

Whether or not a product should be built with those properties is a matter of values. Here we ask, "Is it a good idea to spend the money,

time, and resources to make the beast?"

It is my personal conviction that all scientists and engineers should

spend far more time addressing the question of values than we presently

do -- and I include behavioral scientists, too.

We all carry far too many unstated values and we all too often act on our value assumptions without considering their consequences.

I have been impressed by the way this Symposium has struggled with some of the issues involved on the "Should We?" side of this equation. I commend you for this and hope that you will continue to do so in the

future.

168
INTRODUCTORY REMARKS TO PANEL DISCUSSION -- CAN AND SHOULD PRODUCT LIFE BE EXTENDED?

Some Technical Aspects of Extending Product Life

W. A. Glaeser

Battel le Columbus Laboratories

Columbus, Ohio 43201

Do we have the technology at hand to extend product life? I see two

questions which should be answered first. Will it be necessary to

predict product life within a given confidence limit? Will it be

sufficient to just improve durability with no guarantee on how much

the life is extended?

Products involving mechanical action have multiple parts comprising a system often vulnerable to the weakest part. Some components most

likely to fail include:

Component

Seal s

Spline couplings

Piston-Cyl inder

Brakes

Rolling Contact Bearings

Impel lers

Gears

Failure Mode

Wear, distortion, spring breakage

Wear, fretting corrosion

Scuffing, fouling, corrosion

Wear, thermal degradation, change in

friction properties

Wear, spalling, retainer breakage, corrosion

Erosion, corrosion, fracture

Wear, spalling, scuffing, corrosion, tooth

fracture

The components listed above usually cannot be designed to avoid some

kind of moving surface contact. Thus, they are subject to some degree

of surface degradation. The extent of surface damage (wear, erosion,

spalling) depends on the whole operating environment (temperature, load,

fluids, gases, velocity). Surface damage can suddenly become excessive

when the right combination of operating conditions exist. The probability of expected -- or worse yet -- unexplained component failure

increases as its sensitivity to changes in operating conditions in- creases. The sensitivity of the system can be reduced by proper design

169
and use of appropriate materials that exist today. Thus, the operating

conditions, over which the manufacturer of a product often has no control, can determine life of the product more than deliberate design.

However, the manufacturer can reduce early failures by proper use of

materials and design. This will probably involve bench tests and proof

tests on the product before the required reduction in system sensitivity is achieved. Testing is necessary because most of the information

on solid contact performance is based on empirical means.

For instance, a critical seal in a sewing machine (we don't want oil

stains on the fabric) might require more attention in design than one

in a hand drill. If the seal were a lip type, special attention might

be given to the rubber material, to the way in which the lip is molded,

the location of the load spring, and the surface roughness of the shaft

against which the lip rides. Perhaps an integral dust seal might be

required to prevent wear of the seal lip by debris.

All of this improves the durability of the product but in no way does

it allow us to predict its life. Even with bench testing, expected

scatter in results for surface contact mechanisms makes life prediction

very chancy. That is, we do not have analytical tools as yet by which

we can predict wear rate for real operating conditions even if we can define them quite precisely. So that in answer to the first question,

we cannot sit down and design a washing machine to last for X years

with a 99 percent probability. I believe we can design a washing

machine that will not show an unreasonable number of early failures in

the field.

0

170
INTRODUCTORY REMARKS TO PANEL DISCUSSION —

CAN AND SHOULD PRODUCT LIFE BE EXTENDED?

N. R. Pugh

Sears, Roebuck and Company

Chicago, Illinois 60684

The first question for this panel, "Can product life be extended?",

seems easy to answer -- "Yes, and fairly economically." Furthermore,

Marshall Peterson gave us some insight into that question this morning.

It took a while, however, to realize that a significant change took

place with the addition of the second operative word, "Should product

life be extended?" As a result, Elio Passaglia, that most objective,

analytical and handsome of scientists, finds himself presiding over what

has to be a metaphysical discussion.

The question posed is what Schumacher calls a "divergent" problem. That

is, it cannot be solved by logical reasoning, but requires balancing of

opposites which cannot be handled by pure logic. Instead, "human

values," i.e. moral/ethical considerations, etc. must be the bases of

decision.

Perhaps this group would prefer to say that what is needed is a better

medium of exchange for expressing human values, and long range effects,

often called "societal values," without making clear the subjective base

for such values.

Two great examples were given in the first two papers of this conference.

Mike Denney showed the importance of the matrix of technological factors

and human behavior (consumer usage of products) on one axis; and shortrange/ long-range policy impacts on the other.

The concept of remanufacturing as a strategy, which the MIT paper emphasized, seems to me an admirable example of a strategy evolved through a sound problem-solving process. First -- gathering, second -- analysis

of data to produce meaningful information, third -- applying judgement

to select (or recommend) courses of action.

This judgement need not necessarily reflect currently favored techniques

for judging strategies. For example, Dr. Lerman showed us so well that

use of the "net present value" equation would militate against starting

any major program that cannot be expected to provide quick returns.

The point is that remanufacturing as a strategy does not meet that

criteria. It does, however, meet the criteria of helping to cope with

long-range societal needs predictable by extension of trends which are

171
painfully evident today such as the need to shift from energy-intensive

to labor-intensive activities, wherever this can be done without exces- | sive trade-off disadvantages.

I This panel cannot do much about the broad overview of the question

"Should product life be extended?" in one afternoon. We can, however,

do some exploring of the micro-aspects of the question. That is, what | can be done and should be done, on an incremental basis, one step at a < time.

I For my part, I would like to dwell a bit on the concept of a National ' Information Center for product reliability.

In my talk, the concept was mentioned too briefly, and some people

assumed such a center would jump immediately into brand, and even model,

product life data. Actually, the paper specifically warns against

trying to do too much, too soon.

Instead, what is visualized is an evol utionary extension of some pioneering work that has been described at this seminar -- gathering

information on:

1. Consumer usage (such as the impressive GM work described by Mr.

Larsen)

.

2. Reasons for product discard (several papers had something to say

about this)

.

3. Maintenance, repair, and serviceability data (along the lines of

the work described by Wayne Stiefel).

172
I

I

I

APPENDIX A

Technical Durability of Products

Elio Passaglia

National Bureau of Standards

Washington, D.C. 20234

Abstract

When considering durability, it is useful to make a distinction between

two different aspects of it. These aspects may be called economic

durability and technical durability. Economic durability means the

length of time a durable good lasts in service. Technical durability-, , may be defined as the number of services embodied in the durable good— . Examples of technical durability are the number of shaves in a razor

blade, or the number of miles of travel in an automobile tire. Economic

durability is thus the quotient of technical durability and the rate of

use of the services embodied in the durable good. Technical durability

is not always easy to define, and one of the main technical challenges

is the determination of its magnitude. When the physical basis for loss

to service is known, technical durability can in principle be determined

quite easily. An example is the number of cycles a spring will operate

before failure by fatigue. In other cases, when the physical basis is

not known, technical durability is more difficult to determine. In such

cases, simulated service tests or exposure tests, which are a special

case of simulated service tests, are used to determine technical durability. In both cases the reliability of the durable good (the ability

to perform in service) must be considered. One problem of design is to

increase durability and reliability within the constraints of economics.

- R. Avinger, Jr. "The Economics of Durability", Thesis, Duke

University, 1968.

175
Materials Conservation Through Increased Durability

M. B. Peterson

Office of Technology Assessment

U. S. Congress

Washington, D. C. 20510

Abstract

OTA has been conducting a study on materials conservation in which it

is considering ways in which materials could be saved if and when it

becomes necessary to do so. At the beginning of this study it was felt

that extending product life would result in substantial savings of

material. Figuratively speaking, if all products lasted forever, no more materials would be needed. More realistically, even one year of

extended life would on the surface appear to save appreciable materials.

For this reason, a considerable amount of time was spent investigating

the potential for product life extension. Basic approaches were

fol lowed:

(1) A workshop was held to discuss product durability. To provide a focus, wear control was chosen as the means of achieving improved

product durability.

(2) A contractual study was undertaken to investigate materials savings

using refrigerators, automobiles, and containers as case examples.

(3) A study was conducted of the product end uses of a variety of

metals. From this, an analysis was made of the potential metal

savings possible.

The general conclusion from all of these studies was that increasing

product durability would not be an efficient means of saving materials.

Products are retired from service for many reasons other than poor

durability. The material savings which would result would not be fully

realized until all existing products had been retired (construction

machinery, electrical equipment, etc., already have long lives). A more effective strategy would appear to be the reuse of discarded parts and

components

.

176
The Concepts of Product Life and Consumer Product Safety

Joann H. Langston

Consumer Product Safety Commission

Washington, D.C. 20207

Abstract

This presentation highlights some of the needs for and uses of product

life information in the development of consumer product safety regulations. These needs include calculation of exposure rates, determination

of time until full compliance with a regulation and evaluation of the

effects of a standard on product performance, product demand, and

product safety. In the event of a product recall, this information is

needed to determine the number of affected products in the environment

and the appropriate refund deduction based on use of the product. This

presentation also presents the problems of choosing appropriate difinitions for product life and of gathering product life data at the appropriate level of detail. To date, most of the research of this area has

focused on industrial products and consumer durables which have measurable usage rates. The universe of products over which CPSC has jurisdiction is subject to many variations in use.

177
I

1

!

i
I

APPENDIX B

MECHANICAL FAILURES PREVENTION GROUP

27th Meeting

Product Durability and Life

List of Registrants

Lt. Col . Beason

United States Marine Corps

Code: LMM Navy Dept.

Washington, DC 20380

Donald A. Becker

National Bureau of Standards

B-50, Building 221

Washington, DC 20234

J. F. Belton

Whirlpool Corporation

Monte Road

Benton Harbor, MI 49022

L. E. Bensch

Oklahoma State University

Stillwater, OK 74074

Allan W. Beres

GSA Federal Supply Service

Rm. 1110, Crystal Mall Bldg. 4

Washington, DC 20406

Richard E. Berger

Caterpillar Tractor Company

100 N.E. Adams Street

Peoria, IL 61629

H. C. Burnett

National Bureau of Standards

B-264, Materials Building

Washington, DC 20234

D. B. Butrymowicz

National Bureau of Standards

A-151, Materials Building

Washington, DC 20234

Julius Cohen

National Bureau of Standards

A-113, Polymers Building

Washington, DC 20234

W. D. Conn

University of California

School of Architecture & Urban

Planning

Los Angeles, CA 90024

John Coutinho

U.S. Army Materiel Systems

Analysis Activity

602 Westgate Road

Aberdeen, MD 21001

W. Davis

Office of Technology Assessment

U.S. Congress

Washington, DC 20510

M. Denney

Massachusetts Institute of

Technol ogy

Cambridge, MA 02139

W. J. Derner

FMC Corporation, Bearing Division

7601 Rockville Road, Box 85

Indianapolis, IN 46206

Thomas Deutsch

Chief, Appliance Division

Consumers Union of U.S., Inc.

256 Washington Street

Mount Vernon, NY 10550

181
Madan G. Dhawan

Naval Ship Engineering Center

Code 6145F, Room 378, NC#4

Washington, DC 20362

Albert A. Domingorena

Oak Ridge National Laboratory

Oak Ridge, TN 37830

Andrew Dorney

American Standard Corporation

P. 0. Box 2003

New Brunswick, NJ 00903

George G. Earle

Boeing Vertol Company

P. 0. Box 16858

Philadelphia, PA 19142

Sonny G. Edwards

General Motors Corporation

1921 Ga rey Sue Lane

Mil ford, MI 48042

Peter A. Engel

IBM System Products Division

Endicott, NY 13760

Stephen N. Finger

Pratt & Whitney Aircraft

P. 0. Box 2691

West Palm Beach, FL 33402

Paul M. Fleming

National Bureau of Standards

B-264, Materials Building

Washington, DC 20234

Philip L. Fontaine

Stevenson 0. Kellogg, Ltd.

Toronto, Canada

A. J. Fowell

National Bureau of Standards

A-109, Polymers Building

Washington, DC 20234

W. Glaeser

Battel le Columbus Laboratories

505 King Avenue

Columbus, OH 43201

Nathan Glassman

David Taylor Naval Ship R&D

Center

Annapolis, MD 21401

Walter W. Gunkel

General Motors Corporation

Technical Center

Warren, MI 48090

John H. Haley

Black & Decker Manufacturing Co

701 East Joppa Road

Towson, MD 21204

John Haluska

Consumers Union of U.S., Inc.

256 Washington Street

Mount Vernon, NY 10550

H. D. Harback

FSS-General Services Admin.

Washington, DC 22406

Henry R. Hegner

GARD, Inc.

7449 N. Natchez Avenue

Niles, IL 60648

J. D. Hoffman

National Bureau of Standards

B-364, Materials Building

Washington, DC 20234

R. R. Holden

Hughes Aircraft Company

P. 0. Box 90515

Los Angeles, CA 90009

Bruce L. Huntley

TEAM Corporation

9949 Hayward Way

S. El Monte, CA 91733

182
R. B. Johnson

National Bureau of Standards

B-348, Materials Building

Washington, DC 20234

Frank Kalivoda

Copeland Corporation

Campbell Road

Sidney, OH 45365

Ellen F. Kandell

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, MD 20207

Elmer E. Klaus

The Pennsylvania State University

133 Chemical Engineering Building

University Park, PA 16802

J. Langston

Consumer Product Safety Commission

5401 Westbard Avenue

Washington, DC 20207

H. W. Larsen

General Motors Corporation

Warren, MI 48090

Paul Lerman

Fairleigh Dickenson University

Rutherford, NJ 07070

Paul Lewis

Mechanical Technology, Inc.

968 Albany-Shaker Road

Latham, NY 12110

Thomas E. Lewis

Armstrong Cork Company

1666 K Street, Suite 205

Washington, DC 20006

Kenneth Ludema

University of Michigan

Mechanical Engineering Dept.

Ann Arbor, MI 48109

James McGregor

Office of Naval Attache

Embassy of Australia

1601 Massachusetts Avenue, NW

Washington, DC 20036

M. R. Meyerson

National Bureau of Standards

B-364, Metrology Building

Washington, DC 20234

Raymond F. Misialek

U.S. Navy

NAVSEC Philadelphia Division

Philadelphia, PA 19112

Joseph Morton

Gillette Medical Evaluation Labs

1413 Research Boulevard

Rockville, MD 20853

Edward Mosley

Black & Decker Manufacturing Co.

701 E. Joppa Road

Towson, MD 21204

V. F. Mustafayev

National Academy of Sciences

2101 Constitution Avenue

Washington, DC 20418

Charles M. Overby

Office of Technology Assessment

U.S. Congress

Washington, DC 20510

Elio Passaglia

National Bureau of Standards

B-354, Materials Building

Washington, DC 20234

B. F. Perry

Black & Decker Manufacturing Co.

626 Hanover Pike

Hampstead, MD 21074

Marshal Peterson

Office of Technology Assessment

U.S. Congress

Washington, DC 20510

X83
LCDR W. K. Petrovic

Office of Naval Research

800 N. Quincy Street

Arlington, VA 22217

Wil 1 iam C. Pi rows ki

Naval Sea Systems Command

Navy Department

Washington, DC 20362

John Preston

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, MD 20207

Norman Pugh

Sears Roebuch and Company

Dept. 817, BSC 23-32, Sears Tower

Chicago, IL 60684

F. J. Quail

Canadian Standards Association

178 Rexdale Boulevard

Rexdale, Ontario, Canada

Mark Raabe

House Committee on Interstate & Foreign Commerce

2125 Rayburn House Office 81 dg.

Washington, DC 20515

Martin Rayl

RCA Corporation

RCA Laboratories

Princeton, NJ 08540

S. K. Rhee

Bendix Research Laboratories

Southfield, MI 48076

Saul Ricklin

Dixon Industries Corporation

Bristol, RI 02809

W. H. Rockwell

American National Standards Inst.

1430 Broadway

New York, NY 10018

A. W. Ruff

National Bureau of Standards

B-264, Materials Building

Washington, DC 20234

Marilyn Doss Ruffin

Agricultural Research Service, USDA

CFE-ARS-USDA, Federal Building

Hyattsville, MD 20782

Edwin Sage

General Motors Corporation

General Motors Road

Mil ford, MI 48042

Albert Schmudde

Caterpillar Tractor Company

Industrial Div. - Engineering

Peoria, IL 61629

John J. Scialdone

NASA/Goddard Space Flight Center

Code 726

Greenbelt, MD 20771

T. Robert Shives

National Bureau of Standards

A-111, Materials Building

Washington, DC 20234

William H. Skewis

Tel com Systems , Inc.

2300 S. Ninth Street

Arlington, VA 22204

Arlen J. Slobodow

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, MD 20207

Fred Smith

Environmental Protection Agency

401 M Street, SW

Washington, DC 20460

S. W. Stiefel

National Bureau of Standards

A-359, Metrology Building

Washington, DC 20234
J. E. Stern

NASA/Goddard Space Flight Center

Code 721

Greenbelt, MD 20771

D. A. Swankin

Swankin & Turner

1625 Eye Street, NW

Washington, DC 20006

W. S. VanDelinder

Lockheed California Co.

P.O.Box 551, Dept. 70-71, Bldg.90-2

Burbank, CA 91520

Stephen L. Vick

Black & Decker Manufacturing Co.

701 E. Joppa Road

Towson, MD 21204

David Wallace

Black & Decker Manufacturing Co.

701 E. Joppa Road

Towson, MD 21204

Theodore Wang

National Bureau of Standards

Room A-359, Bldg. 220

Washington, DC 20234

James R. Ward

Value Engineering Laboratory

2550 Huntington Avenue

Alexandria, VA 22303

Stanley Warshaw

National Bureau of Standards

A-355, Polymers Building

Washington, DC 20234

W. A. Willard

National Bureau of Standards

B-128, Materials Building

Washington, DC 20234

K. W. Yee

National Bureau of Standards

A-113, Polymers Building

Washington, DC 20234

185
MFPG PUBLICATIONS

Both printed and microfiche copies of the following MFPG publications

(1-11) whose catalog numbers start with "AD" or "COM" may be obtained

from the NTIS.

National Technical Information Center

5285 Port Royal Road

Springfield, VA 22151

1. Glossary of Terms . AD 721 354

2. Proceedings of Meetings 1-9 (set of 5) AD 721 359

Meeting Nos. 1-5 Papers and discussion on failure

analysis and control.

Meeting No. 6 "Detection, Diagnosis and Prognosis",

December 6, 1968.

Meeting No. 7 "Failure Mechanisms as Identified

with Helicopter Transmissions",

March 27, 1969.

Meeting No. 8 "Critical Failure Problem Areas in

the Aircraft Gas Turbine Engine",

June 25-26, 1969.

Meeting No. 9 "Potential for Reduction of Mechanical

Failure Through Design Methodology",

November 5-6, 1969.

3. Proceedings of Meeting No. 10 AD 721 912

"Vibration Analysis Systems"

January 21-22, 1970

4. Proceedings of Meeting No. 11 AD 724 475

"Failure Mechanisms: Fatigue"

April 7-8, 1970

5. Proceedings of Meeting No. 12 AD 721 913

"Identification and Prevention of Mechanical

Failures in Internal Combustion Engines"

July 8-9, 1970

186
6. Proceedings of Meeting No. 13 AD 724 637

"Standards as a Design Tool in Surface

Specification for Mechanical Components

and Structures"

October 19-20, 1970

7. Proceedings of Meeting No. 14 AD 721 355

"Advances in Decision-Making Processes

in Detection, Diagnosis and Prognosis"

January 25-26, 1971

8. Proceedings of Meeting No. 15 AD 725 200

"Failure Mechanisms: Corrosion"

April 14-15, 1971

9. Proceedings of Meeting No. 16 AD 738 855

"Mechanical Failure Prevention Through

Lubricating Oil Analysis"

November 2-4, 1971

10. Proceedings of Meeting No. 17 AD 750 411

"Effects of Environment Upon Mechanical

Failures, Mechanisms and Detection"

April 25-27, 1972

11. Proceedings of Meeting No. 18 AD 772 082

"Detection, Diagnosis and Prognosis"

November 8-10, 1972

12. Proceedings of Meeting No. 19 (NBS SP 394) COM-74-50523

"The Role of Cavitation in Mechanical Failures"

October 21 - November 2, 1973

Printed copies of the following MFPG publications (catalog numbers

starting with SD) may be obtained from the Government Printing Office.

Superintendent of Documents

U.S. Government Printing Office

Washington, DC 20402

Microfiche copies of these publications (catalog numbers starting with

NBS-SP) may be obtained from NTIS.

13. Proceedings of Meeting No. 20 (NBS SP 423) SN 003-003-01451-6

"Mechanical Failure - Definition of the Problem"

May 8-10, 1974

Cost: Printed copy $6.10

187
14. Proceedings of Meeting No. 21 (NBS SP 433)

"Success By Design: Progress Through

Failure Analysis"

November 7-8, 1974

Cost: Printed copy $3.50 SN003-003-01639-0

Microfiche copy $2.25 NBS-SP-433

15. Proceedings of Meeting No. 22 (NBS SP 436)

"Detection, Diagnosis and Prognosis"

April 23-25, 1975

Cost: Printed copy $4.25 SN003-003-01 556-3

Microfiche copy $2.25 NBS-SP-436

16. Proceedings of Meeting No. 23 (NBS SP 452)

"The Role of Coatings in the Prevention

of Mechanical Failures"

October 29-31 , 1975

Cost: Printed copy $2.65 SN003-003-01 664-1

17. Proceedings of Meeting No. 24 (NBS SP 468)

"Prevention of Failures in Coal

Conversion Systems"

April 21-23, 1976

Cost: Printed copy $3.00 SN003-003-01 760-4

18. Proceedings of Meeting No. 25 (NBS SP 487)

"Engineering Design"

November 3-5, 1976

Cost: Printed copy $5.25 SN003-003-01829-5

19. Proceedings of Meeting No. 26 (NBS SP 494)

"Detection, Diagnosis and Prognosis"

May 17-19, 1977

Cost: Printed copy $4.50 SN003-003-01 844-9

188
tfBS-H4A (REV, 7-73)

U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession BIBLIOGRAPHIC DATA NBSSP514 5n t c T

3. Recipient's Accession No.

t1. TITLE AND SUBTITLE

Product Durability and Life - Proceedings of the 27th

meeting of the Mechanical Failures Prevention Group,

held at the National Bureau of Standards, Gaithersburg,

Maryland, November 1-3, 1977

5. Publication Date May 1978

6. Performing Organization Code

T. Robert Shives and William A. Willard

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

1. v—oiiLi dc t / vrrant iNO.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) Inst. for Matls.Res.,& Ctr.for Cons. Product Tech.,NBS, Wash, DC

20234; ONR, Arlington, VA 22217; NADC, Warminster, PA 18974;

NASA, Greenbelt, MD 20771; DoE, Fossil Energy, Washington, DC

20545

13. Type of Report & Period Covered

14. Sponsoring Agency Code

IS. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 78-606044

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

These proceedings consist of a group of nineteen submitted papers from the

27th meeting of the Mechanical Failures Prevention Group which was held at

the National Bureau of Standards in Gaithersburg, Maryland, on November 1-3,

1977. The central theme of the proceedings pertains to the durability of

consumer products. Special emphasis is on durability technology, product

testing, product performance, the economics of extending product life, and

labeling products for durability.

7. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper

name; separated by semicolons

)

Design quality; durability; durability technology; materials conservation;

product life; product performance; product testing; wear analysis

18. AVAILABILITY XS Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

1 For Official Distribution. Do Not Release to NTIS UNCL ASSIFIED 188

^ Order From Sup. of Doc, U.S. Government Printing-office

Washington, D.C. 20402. SD Stock No . 003-1)03-

20. SECURITY CLASS

(THIS PAGE)

22. Price $3.75

( Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED

C 29042-P74
There's

anew

look

/ A. \^ 1 / ' ' ' monthly

y / / magazine of the NationBureau of Standards.

/ X Still featured are special ar- ^^^^f^kY^^x tides of general interest on ^ X current topics such as consum- \ >^ y / er product safety and building ^^^^ / technology. In addition, new sections are designed to . . . PROVIDE

SCIENTISTS with illustrated discussions

of recent technical developments and

work in progress . . . INFORM INDUSTRIAL

MANAGERS of technology transfer activities in Federal and private labs. . . DESCRIBE TO MANUFACTURERS advances in the field of voluntary and

mandatory standards. The new DIMENSIONS/NBS also

carries complete listings of upcoming conferences to be

held at NBS and reports on all the latest NBS publications,

with information on how to order. Finally, each issue carries a page of News Briefs, aimed at keeping scientist and consumalike up to date on major developments at the Nation's physical sciences and measurement laboratory.

(please detach here) SUBSCRIPTION ORDER FORM

Enter my Subscription To DIMENSIONS/NBS at $12.50. Add $3.15 for foreign mailing. No additional postage is required for mailing witfiin tfie United States or its possessions. Domestic remittances

sfiould be made either by postal money order, express money order, or check. Foreign remittances should be made either by international money order, draft on an American bank, or by UNESCO

coupons.

Send Subscription to:

Q Remittance Enclosed (Make checks payable

to Superintendent of Documents)

Q Charge to my Deposit Account No.

NAME-FIRST, LAST

I I I I I I I I I I I I I I I I I I I I I I I I I I I I COMPANY NAME OR ADDITIONAL ADDRESS LINE

I I I I I I I I I I

STREET ADDRESS

I I I I I I I

I I I I I I I I I I I I

JJ. 11 i_L I I I I

MAIL ORDER FORM TO:

Superintendent of Documents Government Printing Office Washington, D.C. 20402

PLEASE PRINT
WsteHeat

MangniHit

A typical plant can save about 20 percent of Its fuel—just by installing waste heat recovery equipment. But with so much equipment on the market,

how do you decide what's right for you?

Find the answers to your problems in the Waste

Heat Management Guidebook, a new handbook

from the Commerce Department's National Bureau

of Standards and the Federal Energy Administration.

The Waste Heat Management Guidebook is designed to help you, the cost-conscious engineer or manager, learn how to capture and recycle heat

that is normally lost to the environment during in- dustrial and commercial processes.

The heart of the guidebook is 14 case studies of companies that have recently installed waste heat

recovery systems and profited. One of these applications may be right for you, but even if it doesn't

fit exactly, you'll find helpful approaches to solving

many waste heat recovery problems.

In addition to case studies, the guidebook contains

information on:

• sources and uses of waste heat • determining waste heat requirements

• economics of waste heat recovery • commercial options in waste heat recovery

equipment

• instrumentation • engineering data for waste heat recovery • assistance for designing and installing waste

heat systems

To order your copy of the Waste Heat Management

Guidebook, send $2.75 per copy (check or money

order) to Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

A discount of 25 percent is given on orders of 100

copies or more mailed to one address.

The Waste Heat Management Guidebook is part of the EPIC industrial energy management program

aimed at helping industry and commerce adjust to the increased cost and shortage of energy.

U.S. DEPARTMENT OF COMMERCE/National Bureau of Standards

FEDERAL ENERGY ADMINISTRATION/Energy Conservation and Environment

* U. S. GOVERNMENT PRINTING OFFICE : 1978 261-238/116
Business Operations—Books and Journals Dept. American Chemical Society 1155 16th Street, N.W. Washington, D.C. 20036

Please send copies of

A. "PHYSICAL AND THERMODYNAMIC PROPERTIES OF ALIPHATIC ALCOHOLS." (First supplement to Vol. 2 ol the Journal at Physical and

Chemical Relerence Data.) Hard Cover -.$33. 00. Salt Cover: $30 00.

B. "THERMAL CONDUCTIVITY OF THE ELEMENTS. A COMPREHENSIVE

REVIEW." (First supplement to Vol. 3 ol the Journal ol Physical and

Chemical Relerence Data.) Hard Cover - $60.00. Salt Cover: $55.00

C. "ENERGETICS OF GASEOUS IONS." (First supplement to Vol. 6 ot the Journal ol Physical and Chemical Relerence Data.) Hard Cover: $70.00

Soft Cover: $65.00.

/ am enclosing a check / am enclosing a money order

Important

Additions

TO THE JOURNAL OF PHYSICAL AND

CHEMICAL REFERENCE DATA

Three comprehensive reference volumes,

each, as the Journal Itself, published by the American Institute of Physics and the American Chemical Society for the National Bureau of Standards . . . your triple assurance of their accuracy, immediacy, and usefulness.

Supplement No. 1 to Vol. 2 "PHYSICAL AND THERMODYNAMIC

PROPERTIES OF ALIPHATIC ALCOHOLS"

by R. C, Wilhoit and B. J. Zwolinski, Thermodynamics Research Center, Department ot Chemistry. Texas A & M University Represents the most exhaustive review and critical analysis of selected physical and thermodynamic properties of aliphatic alco- hols that has been published in the world literature of chemistry.

Supplement No. 1 to Vol. 3 "THERMAL CONDUCTIVITY OF THE ELEMENTS:

A COMPREHENSIVE REVIEW"

Powell, and P. E. Liley, Thermophysical Properties Research Center, Purdue University, West Latayette, Indiana This comprehensive review of the world's thermal conductivity data presents recommended or estimated values for all 105 elements.

Supplement No. 1 to Vol. 6 ENERGETICS OF GASEOUS IONS

by H. M. Rosenstock, K. DraxI, B. Steiner, and

J. T. Herron. National Bureau ol Standards Provides a comprehensive body

of critically evaluated information on ionization potentials, ap- pearance potentials, electron af- finities and heats of formation of gaseous positive and negative

ions. It is a complete revision and

extension of the earlier reference work, "Ionization Potentials, Ap- pearance Potentials and Heats

for Formation of Gaseous Positive Ions," NSRDS-NBS 26.

at $_

Name

Address .

City Zip Code

.

Title Employer

PIcose add $ 1 .LO ex (ra for (orcign postcxje and hanijling.
NBS TECHNICAL PUBLICATIONS

PERIODICALS

JOURNAL OF RESEARCH—The Journal of Research

of the National Bureau of Standards reports NBS research

land development in those disciplines of the physical and

lengineering sciences in which the Bureau is active. These

include physics, chemistry, engineering, mathematics, and

'computer sciences. Papers cover a broad range of subjects,

'with major emphasis on measurement methodology, and

Ithe basic technology underlying standardization. Also in-

'cluded from time to time are survey articles on topics closely

Ireiated to the Bureau's technical and scientific programs. As

!a special service to subscribers each issue contains complete

[citations to all recent NBS publications in NBS and non-

|NBS media. Issued six times a year. Annual subscription:

jdomestic $17.00; foreign $21.25. Single copy, $3.00 domestic;

j$3.75 foreign.

iNote: The Journal was formerly published in two sections:

Section A "Physics and Chemistry" and Section B "Mathematical Sciences." DIMENSIONS/ NBS

IThis monthly magazine is published to inform scientists,

jengineers, businessmen, industry, teachers, students, and

consumers of the latest advances in science and technology,

with primary emphasis on the work at NBS. The magazine

highlights and reviews such issues as energy research, fire

protection, building technology, metric conversion, pollution

labatement, health and safety, and consumer product performance. In addition, it reports the results of Bureau programs in measurement standards and techniques, properties

of matter and materials, engineering standards and services,

instrumentation, and automatic data processing. Annual subscription: Domestic, $12.50; Foreign $15.65.

I NONPERIODICALS

iMonographs—Major contributions to the technical literature on various subjects related to the Bureau's scientific

and technical activities. Handbooks—Recommended codes of engineering and indusIrial practice (including safety codes) developed in cooperation with interested industries, professional organizations,

and regulatory bodies.

Special Publications—Include proceedings of conferences

sponsored by NBS, NBS annual reports, and other special

publications appropriate to this grouping such as wall charts,

pocket cards, and bibliographies.

Aipplied Mathematics Series—Mathematical tables, manuals, and studies of special interest to physicists, engineers,

chemists, biologists, mathematicians, computer programmers,

bnd others engaged in scientific and technical work.

National Standard Reference Data Series—Provides quanti-

|tative data on the physical and chemical properties of

jmaterials, compiled from the world's literature and critically

jevaluated. Developed under a world-wide program colordinated by NBS. Program under authority of National

Standard Data Act (Public Law 90-396).

NOTE: At present the principal publication outlet for these data is the Journal of Physical and Chemical Reference Data (JPCRD) published quarterly for NBS by the American Chemical Society (ACS) and the American Institute of Physics (AIP). Subscriptions, reprints, and supplements

available from ACS, 1155 Sixteenth St. N.W., Wash., D.C.

20056.

Building Science Series—Disseminates technical information developed at the Bureau on building materials, components,

systems, and whole structures. The series presents research

results, test methods, and performance criteria related to the

structural and environmental functions and the durability and safety characteristics of building elements and systems. Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a subject.

Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often

serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures

published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The purpose

of the standards is to establish nationally recognized require- ments for products, and to provide all concerned interests with a basis for common understanding of the characteristics of the products. NBS administers this program as a supple- ment to the activities of the private sector standardizing

organizations.

Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest

to the consumer. Easily understandable language and

illustrations provide useful background knowledge for shopping in today's technological marketplace.

Order above NBS publications from: Superintendent of Documents, Government Printing Office, Washington, D.C.

20402. Order following NBS publications—NBSIR's and FIPS from

the National Technical Information Services, Springfield, Va. 22161.

Federal Information Processing Standards Publications (FIPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register.

Register serves as the official source of information in the Federal Government regarding standards issued by NBS

pursuant to the Federal Property and Administrative Services Act of 1949 as amended. Public Law 89-306 (79 Stat. 1127), and as implemented by Executive Order 11717

(38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal Regulations).

NBS Interagency Reports (NBSIR)—A special series of interim or final reports on work performed by NBS for outside sponsors (both government and non-government).

In general, initial distribution is handled by the sponsor;

public distribution is by the National Technical Information

Services (Springfield, Va. 22161) in paper copy or microfiche form.

BIBLIOGRAPHIC SUBSCRIPTION SERVICES

Hie following current-awareness and literature-survey bibliographies are Issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A literature survey issued biweekly. Annual subscription: DomesI tic, $25.00; Foreign, $30.00.

tiquified Natural Gas. A literature survey issued quarterly.

jAnnual subscription: $20.00.

Superconducting Devices and Materials. A literature snrvey

issued quarterly. Annual subscription: $30.00. Send subscription orders and remittances for the preceding bibliographic

services to National Bureau of Standards, Cryogenic Data

Center (275.02) Boulder, Colorado 80302.
U.S. DEPARTMENT OF COMMERCE

IMational Bureau of Standards

Washington. D.C. 20234

OFFICIAL BUSINESS

Penalty for Private Use. $300

POSTAGE AND FEES PAID

U.S. DEPARTMENT OF COMMERCE COM-215

SPECIAL FOURTH-CLASS RATE BOOK

*