NBSIR 76-1 1 55(R)

Development of Test Methods

for, and the Evaluation of.

Miles Transducers

John D. Ramboz

Engineering Mechanics Section, Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D C 20234

June 1 976

Final

Prepared for

U S. Air Force

Rome Air Develompent Center

Griffis Air Force Base

and

Electronics Surveillance Division

Hanscom Air Force Base

NBSIR 76-1 1 55(R)

DEVELOPMENT OF TEST METHODS

FOR, AND THE EVALUATION OF,

MILES TRANSDUCERS

John D Ramboz

Engineering Mechanics Section, Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D C. 20234

June 1 976

Final

Prepared for

U.S. Air Force

Rome Air Development Center

Griffis Air Force Base

and

Electronics Surveillance Division

Hanscom Air Force Base

U S. DEPARTMENT OF COMMERCE. Elliot L. Richardson. Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson. Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Acting Director

I
V»J

’ -> ' V

1 -.,
FOREWORD

The work performed was done under NBS Cost Center 2130546 and

was authorized by Hanscom Air Force Base Order No. Y76-901 dated

December 3, 1975.

l
CONTENTS

Page

FOREWORD

ABSTRACT 1

1. INTRODUCTION 1

2. LONG-TERM RESISTANCE TO CORROSIVE MOISTURE 2

2.1 Test Specimen Description and Test Procedure 2

2.2 Test Results for Corrosive Moisture 5

2.2.1 Electrical Leakage Resistance 5

2.2.2 Corrosion of the Flat Transducers 27

2.2.3 Test for Stress Corrosion 35

2.2.4 Leaks at Ends of Flat Transducers 35

2.2.5 Changes in Polyurethane Jackets of Round

Transducers 36

3. RESISTANCES TO FREEZE- THAW CYCLES 39

3.1 Description of the Freeze-Thaw Cycling Test 39

3.2 Results of Freeze- Thaw Cycling 40

3.2.1 Electrical Leakage Resistance 40

3.2.2 Mechanical Strain Measurements 40

4. RESISTANCE TO ROCK DAMAGE 42

4.1 Test Specimen Description and Test Procedure 42

4.2 Results of the Rock Damage Tests 44

4.2.1 Initial Tests 44

4.2.2 One Hundred-Hour Tests 46

5. DURABILITY OF POLYURETHANE JACKETING 50

6. REELING AND UNREELING DURABILITY OF FLAT TRANSDUCERS 54

6.1 Mechanical Characteristics and Strengths 54

6.2 Reeling and Unreeling Laboratory Tests 56

7. COST EFFECTIVENESS ANALYSIS 60

7.1 Original Cost-Estimate Comparisons 60

7.2 Life Expectancy and Cost 63

li
Page

8. SUMMARY AND RECOMMENDATIONS 67

8 . 1 Summary 67

8.1.1 Long-Term Resistance to Corrosive Moisture 68

8.1.2 Resistance to Freeze-Thaw Cycling 69

8.1.3 Resistance to Rock Damage 70

8.1.4 Durability of the Polyurethane Racketing 70

8.1.5 Reeling and Unreeling Durability of the

Flat Transducers 71

8.1.6 Cost Effectiveness Analysis 72

8.1.7 Final Choice: Round or Flat Transducers? 72

8.2 Recommendations 73

8.2.1 Flat Transducers 73

8.2.2 Round Transducers 74

9. ACKNOWLEDGEMENTS 74

10. REFERENCES 75

APPENDIX A.

APPENDIX B.

APPENDIX C.

APPENDIX D.

RELATIVE HUMIDITY AND RAINFALL DATA 77

MATERIALS WHICH OFFER GOPHER PROTECTION AND THOSE

WHICH ARE VULNERABLE 79

COST EFFECTIVENESS ANALYSIS EXAMPLES 80

SOIL ANALYSIS RESULTS FOR SAMPLES FROM GRIFFIS

AIR FORCE BASE SITE 2D ROME, NEW YORK 82

iii
LIST OF TABLES

Table

Table

Table

Table

Table

Table

Table

Table

Table

Table

1 Electrical Leakage for Flat and Round Transducers Subjected

to Hot Saline Solution (Corrosive Moisture Test).

2 Times to Failure for the Flat Transducers (Corrosive Moisture

Test)

.

3 Leakage Resistance Values from Freeze-Thaw Cycling Test.

4 Strain Measurements from Freeze-Thaw Cycle Test.

5 Ultimate Loads for the 25-cm Specimens (Rock Damage Tests).

6 Times to Failure for Half-Ultimate Load, 20-cm Specimens

(Rock Damage Tests)

.

7 Results of Tensile Tests on Stainless Steel Sheaths from

Flat Transducers.

8 Results of Strain Measurements from the Reeling and Unreeling

Tests of a Flat Transducer.

9 Estimated Cost Comparisons for New Round and Flat Transducer

Systems.

10 Estimated Cost Comparisons for Replacement of Transducers Only.

IV
LIST OF FIGURES

Figure 1 Steel tank used for long-term resistance to corrosive

moisture.

Figure 2 a thru g

Electrical leakage resistance for flat transducer

Nos. IB thru 7B.

Figure 3 a thru g

Electrical leakage resistance for round transducer

Nos. 1 thru 7.

Figure 4a Gash in polyurethane jacket of round transducer No. 6

prior to washing salt from transducer.

Figure 4b Gash in polyurethane jacket of round transducer No. 6

after washing salt from transducer.

Figure 5 Cross section of a flat transducer showing region of most

severe corrosion activity.

Figure 6 Dried "salt dome" on flat transducer 7B, location 47, at

edge of overlapped weld zone.

Figure 7 Small "salt domes" on flat transducer 7B, location 74,

on back lip (40x magnification).

Figure 8 Small "salt dome", front lip of transducer 7B, location 47

(20x magnification).

Figure 9 "Salt domes" and "whisker" on back of lip, transducer 7B,

location 74 (20x magnification).

Figure 10 "Salt domes", front lip of transducer 7B, location 47

(20x magnification).

Figure 11 Severe pit corrosion at lip crevice, transducer 7B,

location 47. Salt shown in Fig. 6 washed clear (80x

magnification)

Figure 12 Small elongated pit which penetrated transducer 7B,

location 74, back lip. Salt shown in Fig. 7 washed clear

(80x magnification).

Figure 13 Simple indicator used in rock damage tests for detecting

open coil or short between shield and coil or coil and core

Figure 14 Damaged braid shield of round transducer specimen No. 52

after a 100-hour exposure at a 375-lbf load.

v
Figure 15 An open sense-coil winding of round transducer specimen

No. 37.

Figure 16 The sense-coil winding of flat transducer specimen No. 71

after a 100-hour exposure at a 2043- lbf load.

Figure 17 Smashed sense coil for flat transducer specimen No. 71

after an exposure of 100 hours at a 2043-lbf load.

Figure 18 Damaged polyester tape insultation on flat transducer

specimen No. 72. Note holes exposing core material

beneath insulation.

Figure 19 A field of small pits observed on transducer MILES 96R-1

at Griffis Air Force Base. Pit diameters are approximately 0.04 to 0.09 mm (1.5 to 3.4 x 10 3 in).

Figure 20 Large crack in the polyurethane jacket of transducer

MILES 96R-1 located at Griffis Air Force Base.

Figure 21

a thru c Diagonal wrinkle in transducer stainless steel sheath.

Figure A-l Relative humidity and rainfall during testing period.

VI
DEVELOPMENT OF TEST METHODS FOR, AND THE

EVALUATION OF, MILES TRANSDUCERS

John D. Ramboz

ABSTRACT

The development of tests is discussed and

results are given for two types of Multiphenomenon Intrusion Line Sensors (MILES) transducers.

The round type is fabricated as a long coaxial

line having a polyurethane outer jacket. The

flat type is a coaxial ribbon housing a type 304

stainless steel outer sheath. Five main tasks

were completed: long-term resistance to corrosive

moisture, resistance to freeze-thaw cycling, resistance to rock damage, durability of the polyurethane jacketing, and reeling and unreeling

durability of the flat transducers. Comparative

results between the two types of MILES transducers

are given and indicate that neither type is ideally

suited for all field deployment environments. Chlorides in the soil cause pit corrosion in the crevice

region of the flat transducer sheaths. Rocks and

rodents penetrate the polyurethane of the round

transducers. Cost analyses are given with examples

illustrating cost effectiveness. Design recommendations are given.

Key Words: Evaluation methods; intrusion detectors;

MILES transducers; sensors; test methods; testing.

1. INTRODUCTION

This report describes the development of test methods and the

evaluation of transducers used as intrusion detectors. Multiphenomenon

Intrusion Line Sensors (MILES) are normally deployed as long buriedcable assemblies. They respond to seismic pressure changes and to

near-field magnetic changes. It is desirable to have a long servicelife expectancy, perhaps ten years or more. Transducer failures can

occur due to several causes. It was the purpose of the work described

herein to compare the performances of two different types of line sensors

and to determine comparable life-cycle cost analyses.
The two types of transducers are referred to as "round" and "flat".

A round transducer is fabricated as a round, cylindrical, coaxial line

having an outer jacket material of polyurethane. A flat transducer is

made as a flat ribbon coaxial line having stainless steel as the outer

jacket material. Accelerated life testing was done, as well as other

tests, to determine the amount of possible damage which might be incurred in handling, installations, etc.

The laboratory work was divided into the following five tasks:

Task A:

Task B:

Task C:

Task D:

Task E:

Long-term resistance to corrosive moisture.

Resistance to freeze-thaw cycles.

Resistance to rock damage.

Durability of polyurethane jacketing.

Reeling and unreeling durability of transducers.

Tests for each of the above tasks will be described in terms of the

work performed and the results. Comparisons between the round and the

flat transducers will be made and factors influencing the tests will be

discussed. The transducer sensitivity (magnetic sensitivity and seismic/

pressure sensitivity)^ was not evaluated. Only those factors listed

above which influence the transducer service life were investigated.

Testing under combined environments was not done, e.g., rock danger'

tests combined with freeze-thaw testing, etc.

2. LONG-TERM RESISTANCE TO CORROSIVE MOISTURE

This work was performed to satisfy the requirements of Task A.

Accelerated life testing was desired to determine the aging characteristics of both the round and the flat types of transducers and to obtain

an estimate of life expectancy under a normal service environment.

The nature of the failures are noted and suggestions for corrective

action are offered in some instances.

2.1 Test Specimen Description and Test Procedure

Prepared specimens of both the round and the flat transducers

were subjected to repeated exposures to hot saline solution followed

by drying/bake cycles. The sodium chloride solution was prepared having

a concentration of 5 percent by weight to simulate sea water

[1,2].*

*

The specimens were specially fabricated having an active transducer

length of nominally 2.1 m (84 in). The special flat transducers had

terminations and connectors on them which are identical to 100 m long

transducers used in normal service and fabrication procedures were

basically identical to those employed for the 100 m transducers. The

1 Proposed draft MIL spec, Transducer, Motional Pickup, TR-299/GC ) dated 4-10-75.

* Figures in brackets indicate the literature references in section 10.

2
short round transducers used for this task were the same as those used

in normal service except for length and the signal leads were made from

a twisted, shielded pair with an outer insulated jacket rather than the

normal armored lead. Additionally, the end of the transducer away from

the connector was sealed with heat-shrink tubing and epoxy. Normally,

the polyurethane jacket material is formed over the end of the transducer

to provide a durable seal.

Nine round and nine flat transducers were obtained from the manufacturer under the manufacturers part numbers 28107211 and 28111425,

respectively. Seven of each type were used in the testing and the remaining two of each type served as control samples.

A steel tank 0.53 m (21 in) in diameter and 3.5 m (11 ft. 4 in)

deep was fabricated from four steel drums. Figure 1 shows the tank.

Both drum heads were cut out of three of the drums. One head was removed

from the fourth drum; the head remaining served as the tank bottom. The

four drums were welded together at their ends to form one deep, cylindrical

vertical tank. A 3/8-in thick, 4 ft square, steel plate was welded to

the bottom of the lower drum to stablize the tall column and also to

strengthen the drum head against the 34.5 kPa (5 psi) pressure when the

tank was full.

A wooden rack was made to secure and support each of the fourteen

transducers (7 round and 7 flat) vertically in the tank. The lower ends

of the transducers were loosely secured 46 cm (18 in) above the bottom

of the tank. The upper portion of each transducer was tightly secured

about 15 cm (6 in) below the top level of the tank. This arrangement

allowed the transducers to change their lengths freely as they were heated

and cooled, without placing unnecessary strain on them, while confining

them horizontally at the ends. A steel heat exchanger was attached to

each of the vertical rack supports to provide a heat source during the

drying/bake cycle. It had an overall folded length of approximately

14.3 m (47 ft) and provided ballast to the wooden rack to keep it from

floating. The effective area of this heat exchanger was about 1.5 m

2

(16.2 ft 2 ). Low pressure steam was passed through this exchanger and

bled to the atmosphere during the drying/bake cycle.

The tank was filled about 80 percent (155 gallons) with water and

salt added to make the required 5 percent (by weight) solution. Live

steam was then released at the bottom of the tank and allowed to pass

directly into the solution. This process added water by steam condensation. By the time the solution boiled, the liquid was at its

nominal level, about 43 cm (17 in) below the top of the tank. The

total volume of solution was then about 730 liters (192 gallons)

.

Temperature was measured and monitored by a thermocouple located at

about one-third the height of the tank. Approximately 40 minutes were

required for the temperature to reach boiling. The solution was maintained at boiling for six hours, after which the tank was drained. Heat

3
Figure 1 Steel tank used for long-term resistance to

corrosive moisture.

4
was then applied with the dry heat exchanger and the temperature was

maintained at 38 ± 5 °C (100 ± 9 °F) for a period of two hours. 2 Between

the end of the drying/bake period and the beginning of the next boil

period, the drained tank was allowed to assume the outdoor temperature. 3

Twenty-one cycles of boil-drain-dry-and-bake were made during the

interval from May 4, 1976 through June 4, 1976. These were done on a

daily basis except for weekends, holidays and several days when personnel were not available. The transducers were exposed for an accumulative

120 h to hot saline solution and 39 h to the dry/bake environment.

2.2 Test Results for Corrosive Moisture

2.2.1 Electrical Leakage Resistance

Electrical leakage resistance was measured on each of the fourteen

transducers subjected to the hot saline solution. Resistance was measured between the shield and the sense coil/core circuits. 4 A megohm

bridge was employed, capable of making measurements over a range from

1 kft (10

3

fl) to 100 Tft (10 14 ft). A test voltage of 50 Vdc was selected

for all measurements. This provided adequate sensitivity while minimizing some of the instability problems when using a higher voltage.

It is common to use 500 Vdc when making such measurements. 5,6 ’ 7 However, once moisture has penetrated into the transducer, the resistance

values were very erratic with 500 Vdc applied. This made balancing

of the megohm bridges extremely difficult. Additionally, with the

higher voltages applied, slight motion of the transducer caused a great

2 The boil periods for cycles nos. 1, 2, 3, 4, 5 and 10 were 5 h long,

all other cycles were 6 h long. All dry/bake periods were 2 h long

except for cycles nos. 10 and 19; see footnotes to Table 1 for details.

3 These tests were performed during the month of May when the climate

was mild. Outdoor temperatures did not go below 4 °C (40 °F) nor

above 34 °C (93 °F) during this period. Light rain occurred from

May 14 to 18. See Appendix A for other climatic conditions.

4 Resistance was measured between pins A and C on the connectors for

the flat transducers and between the white lead and shield on the

round transducers.

5 Proposed draft MIL spec MIL-T-XXXXX Transducer Motional Pickup

TR-299/G( ) dated 4-10-75. Paragraph 3. 3. 1.6, calls for 500 ± 50 Vdc.

6 Manufacturer's drawing No. 28111425 dated 6-12-75, note 12, specifies

500 ± 50 Vdc.

7 Manufacturer's drawing No. 28107211, sheet 1 of 2, dated 3-1-73, note

16, specifies 500 ± 50 Vdc.
disturbance in the bridge reading. It is believed that this was caused

by an electrical charge displacement during transducer movement often

referred to as tr iboelectric noise.

The dielectric material within the transducer absorbs a certain

portion of the charge between the sense coil/core circuit and the shield.

When transducer motion occurs, the capacitance between the sense coil/

core and the shield changes because of minute transducer deformations.

With a constant applied voltage, when the capacitance changes, the

charge must also change inversely, because the potential equals the

product of the capacitance and the charge. While the charge is changing,

the transducer either liberates a charge or absorbs a charge. This

"charge-in-motion" is electrical current. The bridge cannot distinguish

between leakage current and "motional" current. Thus, as the transducer

moves, the bridge balance is unsteady, making reading difficult. This

unwanted signal is in addition to the current generated by the normal

operation of the transducer. When it is disturbed, however, this latter

source should not be sensitive to bridge excitation voltage. It was

impractical to keep the suspended transducers from undergoing some

motion and, therefore, the lower voltage (50 Vdc) was selected for

testing

.

Leakage resistance generally decreases with increasing applied

voltage. Hence, the values that were measured were somewhat greater

than if they had been measured at 500 Vdc, by perhaps one-half an order

of magnitude. As discussed later, whenever saline moisture penetrated

into a transducer, the electrical leakage resistance decreased so dramatically that it mattered little whether it was measured at 50 Vdc or

at 500 Vdc. However, more stable readings were generally obtained

at 50 Vdc.

Each of the fourteen transducers were measured for leakage resistance

after they had been mounted in the support rack, prior to any exposure

to the hot saline solution. Each of the round transducers had an initial

leakage resistance greater than 1 Tft (10-^ 2

ft) and each of the flat transducers had a value greater than 0.1 Tft (10-^ft) .

As the hot saline solution test progressed, the electrical leakage

was measured just prior to the beginning of the boil portion of the

cycle. The transducers had then been through a boil period, a dry/bake

period, and at least an overnight period. In some cases, the interval

between the end of the dry/bake period and the beginning of the next

boil period was several days due to weekends, holidays, etc.

Table 1 gives the results of the measurements of the electrical

leakage resistances on each of the seven flat and seven round transducers.

Figures 2 (a)-(g) and 3 (a)-(g) show graphs of leakage resistance versus

exposure time to hot saline solution. The seven round transducers

6
were randomly selected from the lot of nine and arbitrarily numbered

1 through 7. The remaining two round "control sample" transducers

were arbitrarily numbered as 8 and 9. The seven flat transducers were

selected in numerical sequence and had manufacturer numbers on them

of IB, 2B, 3B, etc., through 7B. Flat transducer Nos. 8B and 9B served

as "control samples".

The initial leakage resistance for the flat transducers was approximately 200 Gfl. Cycle-to-cycle variations of an half-an-order-of-magnitude

were common. In general, the resistances remained quite high, greater

than about 10 Gft, until moisture entered the transducer. The resistances

then decreased to less than 100 k£l . In three instances (tranducer

Nos. 3B, 4B and 7B) the resistances fell to less than 10 kft . Figures

2c, 2d, and 2g show this graphically. This suggests that significant

amounts of moisture had penetrated the stainless steel jackets. Overall,

five of the seven transducers "failed" when the leakage resistances

became less than 20 Mft. 8 9 The remaining two transducers (Nos. 5B

and 6B) gave indications of impending failure, i.e., decreasing resistance.

However, the resistances did not decrease to less than 20 MSI and therefore,

they were not considered as failures. Table 2 gives the time to failure

for each of the seven flat transducers tested. Examining Figures 2e

and 2f, it can be seen that the resistances exhibited dramatic decreases

near the end of the 120-h exposure time. It is probable that they

were near failure. The mean time for the five transducers which failed

is about 81 hours, as shown in Table 2. This value does not include

transducer Nos. 5B and 6B. Had the latter two been tested to failure,

the mean time would have increased to at least 92 hours.

Transducer No. 7B (see Fig. 2g and Table 1) showed a dramatic

decrease of leakage resistance after 20 hours of exposure; it then

went back to a normally high value. This low resistance measurement

(about 20 kft) was verified. The low value and the "healing" are unexplained.

Perhaos some insulation material shifted dr broke down, temporarily,

due to the temperature cycling, and repaired itself. This transducer

did not exhibit indication of moisture penetration until much later

(after about 108 hours of exposure)

.

The initial leakage resistances of the round transducers were

about 2TQ. In most instances, they decreased to about 0.1 Tf2 towards

the end of the test. Examination of the plotted data in Figures 3a

through 3g and of the data given in Table 1 shows an unusual decrease

in resistance over the exposure period from about 37 hours to 54 hours,

8 The 20-Mft value is specified by the manufacturer; drawing No. 28111425

dated 6-12-75, note 12.

3 Manufacturer's report 46234, dated 9-10-75, specifies 10 Mfl or more.

7
I

Table 1. Electrical Leakage for Flat and Round Transducers Subjected

to Hot Saline Solution (Corrosive Moisture Test).

Elect r ten 1 Leakage

Cycle

T ransducer

designation

number

b 4-30-76

Mon

1 5-4-76

Tue

’ 5-5-76

Wed

3 5-10-76

Mon

4 5-11-76

Tue

5 5-12-76

Wed

6 5-13-76

Thu

7 5-14-76

Fri

IB 2 30 G 1.8 T 1.7 T 500 C 70 G 500 C 780 C d

1

2B 215 G 1.0 T 980 G 600 G 400 G 40 G 950 G 450 G

3B 195 C 900 G 52 M 3.5 M 2.2 M 3.6 M 3.5 M 1.7 M

4B 240 G 1.2 T 870 G 550 G 45 G 700 G 900 G 350 G 5B 185 G 1.3 T 950 G 90 G 70 G 750 G 980 G 410 G 6B 250 G 1.5 T 138 G 200 G 10 G 700 G 1.3 T 380 G

7B 260 G 1.5 T 56 G 700 G 20 k

C 900 G 290 G 23 G

Boil exposure time, h

Per indicated cycle 0 5 5 5 5 5 6 6 Accumulative 0 5 10 15 20 25 31 37

Dry /bake exposure time, h Per Indicated cycle 0 2 2 2 2 2 2 2 t Accumulative 0 2 4 6 8 10 12 14

1 2.1 T 1.2 T 1 T 650 G 300 G 120 G 470 G 57 k !

2 3.2 T 550 G

1 48 G 500 G 200 G 30 G 34 G 2 M

3 2.3 T 800 G 1 T 800 G 500 G 13 G 200 G 180 k

4 2.0 T 750 G 860 G 500 G 300 G 200 G 2 30 G 10.8 M

5 2.5 T 700 G 1.2 T 700 G 300 G 500 G 220 G 1.4 M

6 3.6 T 660 G 150 M 500 k 150 k 125 k 85 k 62 k

7 1.95 T 450 G 790 G 900 C 300 G 120 G 190 G 5.2 M

fvalue given in ohms; k 10 3

, M « 10 6, G - 10 9

, T - 10 12

. All measurements made at nominally 50 Vde . Measurements made prior to beginning of exposure to saline solution.

Sleasured value verified; temporary low value which "healed", cause unexplained.

Tieasurement inadvertently omitted.

8
Table 1 Continued

Resistance'* at End of Indicated Cycle

Number

,

Date, Day

8» 5-17-76

Mon

9 5-18-76

Tue

10* 5-19-76

Wed

11 5-20-76

Thu

12 5-21-76

Fri

13 5-24-76

Mon

14 5-25-76

Tue

15 5-26-76

Wed

16 5-27-76

Thu

17 6 6-1-76

Tue

18

6-2-76

Wed

19 6-3-76

Thu

20

6-4-76

Fri

21 6-7-76

Mon

8.2 C 540 C 210 C 130 M 160 M 190 k 75 k 50 k 47 k 55 k 45 k 95 k 50 k 50 k

5.6 C 120 C 700 C 500 G 310 M 90 C 370 G 270 G 320 G 800 M 70 k 1.4 k 2.5 k 5.5 k

380 k 750 k <1 k <1 k <1 k <1 k <1 k <1 k <1 k <1 k <1 k <1 k <1 k <1 k

420 C 450 G 740 G 500 C 240 G <1 k <1 k <1 k <1 k <1 k 3 k 4 k 3.5 k 5 k

520 C 460 G 770 G 450 G 250 C 550 G 350 C 600 G 420 G 30 C' 70 G 140 G 650 M 850 M

15 G 84 G 120 G 90 C 37 C 40 G 40 G 25 G 9 G 4.5 G 4.1 G 32 G 15 M 600 M

520 G 550 C 950 G 600 G 310 G 650 G 450 G 500 G 550 C 190 G 220 M 1.5 k <1 k 1.4 k

6 6 5 e

6 6 6 6 6 6 6 6 6 6 6

43 49 54 60 66 72 78 84 90 96 102 108 114 120

2 2 1 C

2 2 2 2 2 2 2 • 2 ho 2 2

16 18 19 21 23 25 27 29 31 33 35 35 37 39

132 k 150 k 140 k 52 M 102 M 70 M 410 M 30 M 5.5 M 400 k 270 M 950 M 1.6 G 25 G

5.6 M 900 k 104 G 75 C 70 G 95 G 75 C 95 M 160 M 1.4 M 5.5 M 13 M 12 M 1.3 M

5.4 M 4 M 170 G 150 G 160 G 120 G 140 G 300 M 17 M 2.7 M 950 M 50 G 230 G 1.8 M

530 k 3.7 M 195 C 160 G 145 C 160 G 240 G 130 M 65 M 40 M 55 G 190 M 140 G 170 G

3 M 3.9 M l6u o 150 C 130 G 125 G 160 G 70 M 12 M 26 M 40 G 5.5 G 160 G 70 G

68 k 65 k 60 k 54 k 45 k 40 k 42 k 41 k 41 k 35 M 35 k 45 k 37 k 36 k

1.1 M 4.8 M 120 G 105 G 120 G 135 G 150 G 4.7 M 5.7 M 200 k 750 k 3 G 70 G 65 G

pSteam feed line broke loose. Temperature dropped to 63 °C for approximately 1 h; dry/bake period shortened to 1 h. Test leads measured for "self leakage” at end of cycle 8, values were 5 TO for flat and 10 TO for round.

^Test leads measured for "self leakage" at end of cycle 17, values were 10 TO for flat and 1.7 T for round.

Tank developed leak, boil test continued full 6 h period. Water and salt added to maintain level and saline

concentration. Leak repaired and tank was filled overnight with water to check leak; no dry/bake period.

Transducer lead fell into tank during cycle 1; washed and cleaned prior to measuring.

9
LEAKAGE

RESISTANCE,

OHMS

EXPOSURE TIME, HRS

Figure 2a. Electrical leakage resistance for flat transducer No. IB.

10
LEAKAGE

RESISTANCE.

OHMS

EXPOSURE TIME, HRS

Figure 2b. Electrical leakage resistance for flat transducer No. 2B.

11

1
LEAKAGE

RESISTANCE,

OHMS

EXPOSURE TIME, HRS

Figure 2c. Electrical leakage resistance for flat transducer No. 3B

.

12
LEAKAGE

RESISTANCE,

13

!
10

li 10

ic 10

9

10

8

10

7

10

6

10

5 10

10

4

IOTa

IOOGa

10 20 30 40 50 60 70 80 90 100 110 120

EXPOSURE TIME/ HRS

Figure 2e. Electrical leakage resistance for flat transducer No. 5B.

14
LEAKAGE

RESISTANCE,

OHMS

EXPOSURE TIME, HRS

Figure 2f. Electrical leakage resistance for flat transducer No. 6B.

15
LEAKAGE

RESISTANCE,

OHMS

lOT/v

Figure 2g. Electrical leakage resistance for flat transducer No. 7B.

1 6
Table 2. Time to Failure for the Flat Transducers

(Corrosive Moisture Test)

Transducer

Designation

Number

Exposure

3

Time, h

IB

I

70

2B 102

i 3B 54

4B 70

5B b

6B c

7B 108

d

Mean 81+23

Time when leakage resistance became less than 10 MO.

Resistance of 120 h was 850 MO; no failure.

Resistance of 120th was 600 M0 no failure.

Resistance measured 20 kO at 20 h, increased to greater than

10 GO until 108 h; cause unexplained. See footnote c of Table 1

and discussion in text.

17
LEAKAGE

RESISTANCE,

OHMS

EXPOSURE TIME, HRS

Figure 3a. Electrical leakage resistance for round transducer No. 1.

18
LEAKAGE

RESISTANCE,

OHMS

10 Ta

EXPOSURE TIME, HRS

Figure 3b. Electrical leakage resistance for round transducer No. 2.

19
LEAKAGE

RESISTANCE,

OHMS

IOTa

13

EXPOSURE TIME/ HRS

figure 3c. Electrical leakage resistance for round transducer No. 3.

20
LEAKAGE

RESISTANCE,

OHMS

EXPOSURE TIME, HRS

Figure 3d. Electrical leakage resistance for round transducer No. 4.

21
LEAKAGE

RESISTANCE,

OHMS

22

i
LEAKAGE

RESISTANCE,

OHMS

10 Ta

Figure 3f. Electrical leakage resistance for round transducer No. 6.

23
LEAKAGE

RESISTANCE,

OHMS

10 Ta 13

24
and another decreased resistance from about 84 hours to 102 hours.

These decreases were caused by periods of rain prior to and during

the time the resistance measurements were taken. Appendix A gives

relative humidity and rainfall data for the test period. A high degree

of correlation exists between periods of high humidity and rain and

the lower measured leakage resistances. It is felt that the active

portion of the transducer was not affected by the rain, but rather

the leads and the terminals where the megohm bridge was connected were

sensitive to atmospheric moisture. This effect and the resulting decrease of resistance during rainy periods cannot be considered as normal

transducer characteristics because these transducers had different

terminations than those used in normal service.

If the lower readings caused by rain are ignored, then the leakage

resistance appears better behaved and generally remained high during

most of the 120-hour exposure time. One notable exception exists,

namely, transducer No. 6. Figure 3f and Table 1 show that the resistance

decreased rapidly from the onset of testing. The resistance was measured

at less than 100 kft over most of the test. Examination of this transducer after removal from the tank showed a gash in the outer polyurethane

jacket which allowed large amounts of saline solution to enter the

transducer. No other transducers exhibited the same kinds of characteristics during the test period. It is, therefore, concluded that none

of the other round transducers had serious leaks and hence, did not

fail

.

The gash found in round transducer No. 6 is believed to have been

caused by the steam feed line. Early in the testing program, it was

noted that the feed line flailed inside the tank and repositioned itself.

It is possible that the flailing steam line could have slashed this

transducer jacket, causing the damage. Microscopic examination shows

definite signs of cutting, and not tearing as might occur as a result

of a pressurized rupture. Figure 4 shows the damaged polyurethane

jacket. After removing the outer jacket, discolorations inside indicated

that the solution had "traveled" the entire 2-m length of the transducer.

At several times during the test, the bridge test cable leads

were measured for their leakage resistance. In all instances their

resistance was very high, commonly greater than 1 TQ. Thus, the test

leads did not adversely affect the measurement process by shunting

the transducer leakage resistance.
Figure 4a. Gash in polyurethane jacket of round transducer No. 6

prior to washing salt from transducer.

Figure 4b. Gash in polyurethane jacket of round transducer No. 6

after washing salt from transducer.

26

v
The failure criteron for the round transducers was a leakage resistance of less than 100 Mft

.

10,11 Ignoring low resistance readings

during the rainy periods as previously discussed, four of the round

transducers (viz., transducer Nos. 1, 4, 5 and 7) maintained leakage

resistances greater than 10 Gfl. Two transducers (Nos. 2 and 3) had

final leakage resistances of just over 1 MQ each. Regarding the latter,

additional measurements were made to verify that the lower resistances

were inside the transducers and not in the transducer signal leads.

Furthermore, a portion of the lead was removed and a fresh, clean portion

of lead was stripped. The same resistance values were measured. The

resistances were re-measured (14 days after the conclusion of the test)

and, again, the values were low and approximately as before. The polyurethane jackets were then removed for visual inspection of the insides

of the transducers. No indications of moisture were found. This suggests

that either the insulation inside the transducers broke down (probably

because of the temperature environment), or that undetected moisture

did penetrate into the transducers. If the former is the case, further

investigation would be required to determine just what was failing.

If the latter is the case, then it would appear that the jacket or

end seals failed, allowing moisture to enter. At this time, no firm

conclusion can be drawn as to the cause of the decreased resistances

for transducer Nos. 2 and 3.

2.2.2 Corrosion of the Flat Transducers

The flat stainless steel transducers which were tested in the

saline solution all showed signs of corrosion. The most serious corrosive activity was localized in the region of the weld zone on the

edges of the transducers.. Figure 5 shows a cross section of the transducer sheath and indicates the region of most severe activity.

Microscopic examination of the transducer revealed pitting in

many areas along the length of the transducer. Most of the severe

pits were localized to the region beneath or near the overlapped lip

of the weld zone, as indicated by Figure 5. The pit diameters ranged

from the lower limit of the optical resolution, 0.25 ym (10 4 in), to

about 25 ym (10 3 in) . Pit depths ranged from some that were shallow

and superficial to others that penetrated the full 125 ym (5x10 ^ in)

sheath thickness. There seemed to be little correlation between pit

diameter and pit depth. The pits which penetrated the sheath had diameters over the full range from 0.25 to 25 ym.

10 Manufacturer's information specifies 100 Mft; drawing No. 28107211,

sheet 1 of 2, dated 3-1-73, note 16.

Proposed draft MIL spec MIL-T-XXXXX, Transducer, Motional Pickup

TR-299/G( ) dated 4-10-75. Paragraph 3. 3. 1.6, specifies 100 Mft.

27
Figure 5. Cross section of a flat transducer showing region of most

severe corrosion activity.

28
Figure 9. "Salt domes" and "whisker" on back of lip, transducer 7B,

location 74 (20x magnification)

.

Figure 10. Salt domes", front lip of transducer 7B, location 47

(20x magnification).

!?

31
Figure 11. Severe pit corrosion at lip crevice, transducer 7B,

location 47. Salt shown in Fig. 6 washed clear

(80x magnification)

.

Figure 12. Small elongated pit which penetrated transducer 7B,

location 74, back lip. Salt shown in Fig. 7 washed

clear (80x magnification).

32
The pits that penetrated the sheath allowed saline solution to

enter, and the liquid then propagated inside the transducer. After

removal of the transducers from the test tank, they were wiped clean

with a sponge and water, and laid horizontally to dry. After several

days, saline solution emerged from the penetrated pits and the salt

dried, thus marking those particular pits which caused leaks. Figures

6 through 10 show small "salt domes" where the liquid had emerged and

dried. Pits that did not penetrate the sheath did not contain sufficient

saline solution to cause any noticable buildup of salt. This technique

was successful in locating extremely small pits which had penetrated.

For example, in Figure 9, note the two small salt domes to one side

of the large hollow dome, and also the salt whisker to the other side.

These microscopic pits are a small fraction of 25 ym in diameter, yet

penetrate the full thickness of the sheath.

Figures 11 and 12 show pits which penetrated. The corrosion shown

in Figure 11 began in the crevice at the edge of the overlapped lip

in the weld zone. In a length of about 400 pm, there were several

pits which penetrated. Also note that the upper lip of the lap was

corroded in a semicircular shape. Figure 6 shows this same region

prior to removal of the salt, at somewhat less magnification. Figure

12 shows a cell which had a long slender track of corrosive activity.

It had also penetrated the sheath. These illustrate typical corrosive

pits found in the sheaths of the transducers.

It is well known that solutions containing chloride ions attack

the family of 18-8 stainless steels. The pit-type of corrosion which

occurs in type 304 stainless steel in sea water is well documented

[3,4,5]. Pits begin by the failure of passivity at small selected

regions at the surface. The breakdown is followed by the growth of

an electrolytic cell, the anode of which is a microscopic area of active

metal and the cathode is the large surrounding region of passive surface.

Considerable current can flow in this small region, causing rapid corrosion at the small anode. The corrosion-resistant, passive metal

surrounding the anode, and the passivity-destroying characteristics

of the corrosion by-products within and very near the pit, force the

corrosion to penetrate the metal rather than to spread along its surface.

The rate of pit penetration is influenced by many factors. Temperature, ion concentration, solution velocity, pH, volume of dissolved

oxygen, corrosion by-products, fouling, geometry, surface contamination,

working history, residual stresses, heat treatment process, and weld

process are the more important factors. It is difficult to control

or to know each of the influencing factors in a test such as performed

on the flat transducers.

It is impractical to attempt a comparison between the accelerated

saline solution tests performed and real-life conditions because no

meaningful time-scale factor is available. The most important results

of the saline solution tests are knowing what kind of corrosion occurs

and where it occurs.

29
Figure 6. Dried "salt dome" on flat transducer 7B, location 47,

at edge of overlapped weld zone.

Figure 7. Small "salt domes" on flat

transducer 7B, location 74,

on back lip (40x magnification).

Figure 8. Small "salt dome", front lip

of transducer 7B, location

47 (20x magnification).

10
Buried transducers will not experience environments such as open

sea water boiling saline solution. It is conceivable, however, that

transducers will be deployed in beaches or other regions where salts

(particularly chlorides) are in high concentration. It is, therefore,

under these conditions that these results are relevent.

Comparisons can be made with other tests performed to evaluate

the corrosion properties of type 304 stainless steel. Tests performed

at Kure Beach, N.C., in warm sea water just offshore, indicated pitdepth growth rates of about 1750 ym (69x10 3 in) per year for type

304 stainless steel. 12 At this rate, a 125 ym (5x10 3 in) sheath thickness would be penetrated in about 26 days. Other references indicate

severe pit-crevice corrosion under similar testing conditions, but

fail to give pit-depth growth data.

Two other sources of information on the corrosion of stainless

steel type 304 indicate somewhat different results. Reference 6 13

gives results for type 304 stainless steel buried for up to 14 years.

It shows that the average maximum pit-depth penetration of the specimens

ranged between 27.9 and 203 ym (1.1x10 3 and 8x10 3 in) per year. The

average of all of the specimens over the entire 14-year period was

about 56 ym (2.2x10 3 in) per year. This suggests that a 125 ym thick

sheath could be penetrated in about two years under those conditions.

The soil was classified as aerated, poorly drained, docas clay containing about 2 percent sodium chloride. It was also observed that the

penetration rate was higher for the first six years of the test and

that the rate slowed considerably after six years. No reason for the

slowing was given. This is contrasted by a statement given in the

same reference, pertaining to burial tests in other soils, that, "steels

containing larger amounts of chromium and nickel (i.e., type 304) .. .were

wholly resistant to corrosion. 1Lf

Another reference [7] studied a variety of materials for use in

shielding underground telephone cables. Stainless steel type 304 was

among the materials examined. The test sites were selected to represent

a wide variety of soil properties. The soil types were classified

as, and located at:

Sagemoor sandy loam

Hagerstown loam

Clay

Lakewood sand

Coastal sand

Tidal marsh

Toppenish, Wash.

Loch Haven, Md

.

Cape May, N.J.

Wildwood, N.J.

Wildwood, N.J.

Patuxent River, Md

.

12 Reference 4, page

13 Reference 6, page

14 Reference 6, page

413, table 16 and associated discussion.

52, table 26, specimens K and R.

49, discussion under High Alloy Steels.

33
The chemical properties of these differ widely with respect to

their composition and the amount of soluble salts. The pH of the soils

ranged from about 4 to 8.8. The electrical resistivity of the soils

varied from about 55 ohm-cm (that of sea water) to about 30,000 ohmcm. Aeration ranged from good to very poor. The soils selected included

those which were known to be moderately corrosive to those which where

very corrosive.

The stainless steel shields tested were parts of special cables

intended for telephone usage. Six specimens were buried at each test

site at depths of 3 to 4 feet. One specimen was withdrawn from each

site each year for a total period of 6 years. The shielding material

consisted of 125 ym thick corrugated type 304 stainless steel sheath.* 5

A rating system of 0 to 10 was used, where 0 meant total distruction

of the specimen and 10 meant that the specimen was unaffected by corrosion, or "...excellent, unaffected, no indication of corrosion". 15

In all instances, these specimens were evaluated as having a rating

of 10 for all soil test sites, including coastal sand and tidal marsh

sites where chlorides are known to exist. Thus, in the 6 year period,

no evidence of corrosion was apparent in 36 specimens buried at six

different locations. 17 Additionally, combinations of stainless steel

and other materials used as composites were tested, with impressive

results

.

The apparent conclusion is that stainless steel type 304 is excellent for most applications of buried transducers but, according to

reference 6, one could expect to find soil and environmental conditions

that might result in corrosion attack on the subject transducers.

From the tests performed, it can also be concluded that if corrosion

occurs, it will most likely be pit corrosion in the crevice region

of the weld zone.

15 Reference 7, description of cables discussed under systems 17 and 18.

16 Reference 7, Table 3.

17 The test in the coastal sand was for a period of 5 years.

34
2.2.3 Test for Stress Corrosion

An important type of corrosion that needed examination was stress

corrosion. To test for this, a 38-cm (15-in) length of flat transducer

was bent into a "U" shape having a radius of about 4 cm (1.5 in).

This produced a high tensile stress along the outer fibre of the transducer. The specimen was exposed to a boiling saline solution for an

accumulated duration of 243 hours.

Microscopic examination of the transducer after exposure revealed

no signs of stress corrosion; only pit and crevice corrosion, as previously described, was evident.

2.2.4 Leaks at Ends of Flat Transducers

Careful examinations were made at the terminations of both ends

of each of the flat transducers. The "bell-shaped" adapter end fittings 18

at the end of the transducers, away from the cable, showed signs of

leakage. The plugs 19 soldered into the adapters were not water tight.

The bonds on the transducers appeared sound, but the plugged ends leaked

around the seam. It was the result of poor and inadequate soldering.

The epoxy coatings over the ends did not help to any measurable amount.

Several of the end plugs were physically removed, without heating,

to permit inspection of the soldering and to check for signs of corrosion.

The soldering was incomplete and, in several cases, the adapter ends

were full of saline solution.

This is a serious source of leaks, especially because there are

apparently no checks at this location during manufacturing. Leak tests

are performed by the manufacturer prior to the soldering of the end

plug into the adapter. A different method of applying the pressure

for leak tests needs to be developed for use after the end plugs have

soldered in place.

The adapter assemblies 20 and the hose adapters 21 at the cable

ends of the transducers all appeared sound. All seven of the transducers

which were exposed to the saline solution were inspected and none of

them showed signs of leakage at this location.

18 Adapter end, manufacturer's part No. 28109835-001

1

9

Plug, manufacturer's part No. 28109836-001

2 0 Adapter assembly, manufacturer's part No. 28111427-001

2

1

Adapter hose, manufacturer's part No. 0103-4-4C

35
2.2.5 Changes in Polyurethane Jackets of Round Transducers

Seven round transducers were subjected to the hot saline solution

as described in section 2.1 of this report. Two physical changes of

prinicipal interest was noted:

1) The hardnesses of polyurethane jackets decreased, and

2) The diameters of the jackets increased.

The main parameters of the test environment of interest are temperature and moisture. The saline content did not significantly affect the

test results.

Jacket hardness was measured with a Shore A type A~2 durometer.

Care was taken to ensure that bridging of the measuring point did not

influence the readings significantly. Also, great care was needed

in placing the durometer on the curved surfaces. A technique was developed that proved sufficiently reliable. In addition, a number of readings

were taken on each specimen at a number of different locations and

the results averaged. Generally, no less than ten readings per specimen

were used and readings occurring beyond one standard deviation from

the first mean were removed from the final average.

Twenty-centimeter (8-in) specimens were tested in a beaker of

boiling saline solution over a period of 320 hours prior to the beginning

of the main saline solution test. The original hardness prior to exposure

was measured as 88.5 ± 0.1. After 320 hours of accumulated exposure,

the mean of the hardness measurements was 78.5 ± 0.5. (The uncertainties

were computed on the basis of the one standard deviation values of

the data.) This represents an average decrease in hardness number

of 11.3 percent for 320 hours of exposure.

The specially fabricated 2.1-m long transducers (described in

section 2.1) tested had an original Shore A durometer hardness of 86.8 ±

2.3. After an accumulated exposure of 120 hours, the hardness was

measured as 80.0 ± 2.4. This represents an average decrease of hardness

number of 7.8 percent, for the 120-hour exposure, for the seventy locations measured.

Results contained in reference 8 for a number of polyether urethanes

tested at various temperatures and humidities correlates reasonably

well with these results. For example, a hardness decrease of 9 to

18 percent could be expected for testing performed at 97 °C and 95 percent

relative humidity. It is known that immersion in boiling water is

somewhat less severe than a noncondensing 95-percent relative humidity

environment; therefore, a smaller decrease of hardness could be expected.

The range of values measured in the present investigation are sufficiently

close to those published results as to verify the test results. This is

especially true when the specimen thicknesses and geometries are considered .

36
References also showed that accelerated testing at elevated temperatures and moisture content follows the Arrhenius equation [9,10]. This

equation permits the estimation of "failure" times at temperatures different from the test temperature. The Arrhenius equation is

c 2

In — = C

t l

Where t^ = time to reach a criterion at temperature Tj,

t 2 = time to reach the same criterion at temperature T 2 ,

T} = absolute temperature at which t^ was determined,

T 2 = absolute temperature at which t 2 was determined, and

C = a constant related to the chemical reaction rate and slope

of the activation energy line.

The constant C has been determined for a family of urethane polymers

and is sufficiently close to C = 8800 K so as to permit calculations

based on this value.

It is desirable to find an estimate of time t 2 for which the jacket

would have decreased its hardness by the same percentage (i.e., 7.8

percent) at some lower temperature, such as encountered in the soil,

rather than the elevated test temperature. If it is assumed that the

soil temperature were held at a constant 10 °C (50°F) , then

Tl = 373 K,

T 2 = 283 K,

tj = 120 hours = 5 days, and

C = 8800 K.

Rearranging equation (1) and solving for time t 2 ,

Ti-T2

TlT 2

( 1 )

t 2 = ti In 1 C

T 1 -T'

T1T2 ( 2 )

37
From this equation and the values shown above t 2 - 9066 days - 25 years. Thus, at a temperature of 10 °C, the polyurethane jackets

could be expected to decrease their hardness numbers from an original

value of 86.8 to 80 in about 25 years. Under these conditions, the

accelerating test factor is 1813; each 6 hours of test performed at

100 °C was equivalent to about 1.25 years of service at 10 °C.

In some typical areas, where these transducers may be deployed,

the soil temperature may exceed 10 °C for periods of summer days and

may cool to values less than 10 °C in the night. Moreover, during

winter months, the temperature will likely be less than 10 °C. It

is felt that the selection of 10 °C as an arbitrary value is conservative when an average temperature over a year's time is considered.

The aging effect is cumulative and irreversible and, therefore, the

slower aging rates at colder temperatures can be calculated with equation

(2) and combined with the rates at higher temperatures to simulate

different winter and summer aging.

The decrease in hardness number of about 8 percent, resulting

from the 120 hours of test, does not constitute a failure limit of

transducer usefulness. Certainly, some lower values of hardness could

be tolerated, but how much is not known. It should be emphasized that

hardness alone is not the sole parameter of jacket durability. The

material may fail due to low values of tensile or compressive strength,

tear strength, dielectric strength or other parameters. Relationships,

if any, between Shore A hardness and these other parameters are not

known. However, in the limit of durometer hardness of <_ 1, the estimated failure time for these materials at 10 °C can be extrapolated

to somewhere between 2000 and 60,000 years. Undoubtedly, some other

failure mechanism would occur first. These examples do, however, serve

to show that due to temperature and high humidity, polyurethane jacket

material would not be expected to degrade seriously for several decades.

It was noted that the jackets of the transducers loosened around

the braided shield beneath it. It was possible to slide the urethane

jacket back and forth for a small distance along a transducer's length,

or to twist the jacket around the transducer, after exposure to the

test environment. Attempts to measure the change in jacket thickness

(or jacket diameter) were unsuccessful. The transducers were sufficiently

out-of-round as to require a multitude of dispersed measurements.

Furthermore, the urethane jacket material varied by as much as 2:1

in thickness on some of the transducers. The change of thickness or

diameter due to testing is only a small part of these dimensional variations due to manufacturing inconsistencies. With some careful experimental

planning, the dimensional changes needed to estimate material property

changes could possible be determined, but it was felt not worthwhile

at this time.

38
3. RESISTANCES TO FREEZE-THAW CYCLES

This work was done to satisfy the requirement of Task B. Flat

and round transducers were exposed to a cycling temperature environment

over a range from nominally -18 °C to 38 °C (0 °F to 100 °F) . Electrical leakage resistance was measured on all of the transducers and strain

was measured on selected flat transducers.

3.1 Description of the Freeze-Thaw Cycling Test

Seven flat and seven round transducers were specially fabricated

for the freeze-thaw cycling test. The transducers had a 1.06-m (42-

in) active nominal length exclusive of their leads. The flat transducers

had leads similar to a normal transducer. The round transducers had

leads selected for this test and are the same as those on the round

transducers tested in the corrosive moisture test. (See section 2.1

for a description.)

Three of the flat transducers had small foil-type resistance strain

gages attached to the folded edge of the stainless steel sheath in

the weld zone at about mid-length. Transducers 1A and 5A each had four

gages mounted on them while transducer No. 2A had only two gages.

The gages were sealed against moisture with wax.

Each of the fourteen transducers were packed separately in sandfilled aluminum trays. Approximately two inches of sand were put in

the tray, followed by careful placement of the transducer on the bed

of sand. The top of each tray was then filled with sand for a total

depth of approximately four inches and the sand was saturated with

water. This required a total of about 700 pounds of sand and 14 gallons

of water. The rack assembly was located horizontally in a freezer

chest. A 2600-watt heater and an air circulating fan was also placed

in the bottom of the freeze chest. Air and sand temperatures were

monitored with a thermocouple and a strip-chart recorder.

The freeze portion of the cycle required about three days for

the wet sand to reach -18 °C. It was kept at this low temperature

for an additional day, making the freeze portion of the cycle normally

four days long. The heating capacity was greater than the cooling

capacity. It was, therefore, possible to thaw the frozen sand and

raise its temperature to 37 °C easily, within one day. Thus, a normal

freeze- thaw cycle was 5 days. 22 The test profile provided ten complete

freeze- thaw cycles.

22 On several occasions, the freeze portion of the cycle was extended

by one or more days because of weekend or holiday schedules. In

no instance was the heating portion of the cycle permitted to exceed

one day.

39
3.2 Results of Freeze-Thaw Cycling

3.2.1 Electrical Leakage Resistance

Electrical leakage resistance was measured on each of the fourteen

transducers subjected to the freeze-thaw cycling test. The resistance

was measured between the shield and the sense coil/core circuits.

The measurements were made similar to those for the hot saline solution

test

.

2 ^

Table 3 gives the results of the measurements. Measurements were

made at the end of each 4-day freeze period and at the end of each

1-day thaw period. (Measurements for the first and second freeze cycles

were not made, only the "thawed" leakage resistances were taken.)

A general trend was that the cold leakage resistance was usually somewhat

greater than the warm resistance during thaw. The leakage at the low

temperature was greater than 15 G£2 for transducers which did not fail.

The leakage at the warmer temperatures was greater than 20 GO, in most

instances

.

Notable exceptions are shown for flat transducers 2A and 7A and

round transducer 27. The resistance fell rapidly in transducer 2A

by the third freeze cycle. It was later determined that moisture had,

indeed, penetrated the stainless steel jacket. No explanation for

the lower "thawed" resistances in transducer 7A is offered. The value

did not fall below about 6 Gft at anytime and, therefore, it was not

considered a "failure". Round transducer 27 showed an unusual decrease

at thaw in Cycle No. 4 and at freeze in Cycle No. 9. It is suspected

that the recorded value of 420 kft should have been 420 Gft and can,

perhaps, be ignored as an anomaly. However, the value of 6 GO, at Cycle

No. 9 was rechecked several times and did, in fact, exist. Apparently,

the temperature cycling repositioned portions of the insulation, thus

temporarily changing the internal leakage paths.

Overall, only one flat transducer (transducer 2A) and none of

the round transducers failed.

3.2.2 Mechanical Strain Measurements

Flat transducer No. 2A was later pressure tested to find the location of the leak. Microscopic examination revealed it to be a crack

in the weld zone very near the inside of the welded lip. It appeared

that the jacket had skewed sideways by a small amount during the welding

process and "weld nuggets" had been formed beyond the region normally

welded. It is likely that residual stresses were present in this macro

region. Reeling and unreeling in normal handling may also have aggrevated

the region and initiated the small crack.

23 See section 2.2.1 for a description of the measurements.
Table

3.

Leakage

Resistance

Values

from

Freeze-Thaw

Cycling

Test

(Values

in

Ohms

and

the

Appropriate

Power

of

10;

k

=

10\

M

=

10 &

, G

=

10^,

T

=

10

12

).

o o o o o o O o O o o o o o m o o o o uo O o O o o o O

CM CM O' O' CM O in CM uO o CM

E- CM r—

1

i—4 CO co <3 CO CO co ^3 UO o

o o o o O 8- H E- E-* H H E-* Eh N o o o o o O CM >3 CM CM m o uo vO o O

CM CO *—

>—

1

r-« O' —4 —4 i—4 H H —

i

r—4 1—4 fa O O o O o u o o O o O o o o O o o o o o o O o o o o

CM vO 00 CM o uo vO CO O' 00 uo o

H *-< CM CO CO CO CO CO Mf CO

O'

(U O o o e> o O O H o H E-> H O

N O o o o o o uo O o in CM vO

co vO in 'O- 3 in r^. O

co CO 00 r—l n UO oo i—

4

iH 1—4 H

fa O O o O o O o o O o o o o O O o o O O m o o o o o o o

3 m vO 00 i—4 i—

4

uo CO o H o o o 1—4 i—4 CM vO co CO Ml- ^3 uo <f

co

<u O o o o O O o H H Eh E- Eh Eh N o o o o o o o o co CO UO i—

4

00 o CO O' CO uo CO uO m cr> CO co CM CM CM i—4 pH H I—i iH rH

fa O o o o o o H o o O o o o o o o o O in M0 o o O o o o m CO CM 00 O' o CO in m o o

H •H r—

(

1—

1

H <r CM vO co uo 3

(1) H £ o o o O O H H H H Eh Eh N 3 o o uo o MT o co CM t—4 H i—i o in lO vO O'

>-4 CM H co p—

4

r—4 H H H H i—l fa O 4* O o o o o o O o o o o o O O O m uO o in o o o o o o o

4= O O' O' UO 00 vO vO c- o vD in in in H H t—

i

i—4 r>* CM CM CO CM CM iH CM

v£>

<U H H o o H O O H H EH H H H

N o 3 IT, o CM O o CM uo iH CM c> co o vC i—4 co o

o U 00 r—l CM i—i pH O' i—l i—4 rH r—4 rH H

z fa

0) i—

1

O o o o O o o O o CJ o o o

u 5 > vO o o o O o uo o o o o o o o

U JZ r* 3 CM CM oo CM CO uo vO r- CM CO 1—4 H 1—1 00 uo <3 uo c- * m

(0 JZ a; O x O e> H o O H u H H H H Eh H N

1 OJ O v£> o CO CM o n O' O in co co co uo

0* c- m vO o vO UO N u< CM i—4 co i—4 CM i—4 in rH H

<D fa a

n

fa O X O o o u O o O o O O O r* 3 S) o UO in o o O o O O o o

. JS vO ON r-^ vO vO co in CO c~ CM H 1—4 co co co CM CO <3 3

3

0J H X H H H CJ) O O H H O O o o

N

(V <3- m vO CM vO m O O c- MJ- O O o o

0J co i—l ^3- i—4 O O UO o CM CM CM r—4 CO pH iH co O' v£> 00

fa O X o O o o o O o o O O O O

CO O vO c- o UO o 00 O o o O O O o

sz 3 av >3- 00 vD uo o O co U0 H

H rH i—i p—

i

-3- c- >3- U0 Mt c~ 3 co

<D H X o H H H o O O H H H O O

N

0) 3 m o CM <r CM o O O CM MT CM O O

a> co O' M0 in o UO 3

3 <r <r O' 00 pH iH rH v£> 00

fa o O o O O o o O H o e> o O Eh

C0 O m o O o o o o >3- o o o O CO

co m vO n m CM o in o in pH H H CM in 00 CM co

CM

a>N

0)

0)

fa o O o o o O o O O O o U O

co o O o o o O o o o o o o o 1 42 co in CM CM O' vO o CM CM o o UO 1 H •H •h rH 1—4 pH 00 O' 00 vO c» h

<UN

CUa>u

fa < < < < < < < pH CM co n vO

rH CM 3 m vO CM CM CM CM CM CM CM saaonpsuIiL_lLLi_ siaonpsueaj, puno)[

41
Table 4 gives values of strain as measured on the three transducers

instrumented with gages. In most cases, the strain increased with time.

It is likely that the continual increase in measured strain was due

to a slow repositioning of the transducers within the sand. The freezing and thawing action of the wet sand produced heaving, which could

have caused the transducers to slowly change position. The first column

of Table 4 shows the mean of the differences between the strains measured

when frozen and when thawed. The maximum difference measured was 1526 x

10 6 in/in. This occurred on transducer No. 2A during Cycle No. 4.

The mean differences for transducer Nos. 1A and 5A were between about

300 and 500 x 10 6 in/ in. The mean for transducer No. 2A was 800 x 10 6

in/ in for Gage 2. There is some indication that transducer No. 2A

experienced more strain than the other two; no reason is apparent.

The thermal expansion calculated from a linear coefficient of 8 x

10 6 to 9 x_10 6 Cin/in)/°F for the full 100 °F temperature difference

is 800 x 10 6 to 900 x 10 6 in/ in. This compares favorably with the

measured_values of strain difference which lie between 300 x 10 6 and

800 x 10 6 in/in on the average. The calculated values do not account

for such factors as heaving of the freezing sand, nor that the ends

were frozen in place prior to the center span of the transducers.

Tf it is assumed that the transducers were free to expand and contract

due to change of temperature while the sand was fully thawed, and that

the two ends of each transducer were rigidly locked at the freezing

point (i.e., 0 °C), then the maximum tensile load would be about 311N

(70 lbf), based on the entire cross sectional area of the transducer.

This, compared with the ultimate load capability of nearly 4900N (1100

lbf), does not explain the crack noted in the weld zone.

21* It is probable that the crack was initiated by handling or other effects, and

that the freeze-thaw action merely aggravated it to where moisture

could enter the transducer.

4. RESISTANCE TO ROCK DAMAGE

This work was done to satisfy the requirements of Task C. Both

round and flat transducers were transversely loaded to determine the

ultimate loads that could be sustained up to failure. Then, a number

of specimens of round and flat transducers were loaded at one-half

of their respective ultimate loads for a period of 100 hours. Comparisons of the types of failures are noted and discussed.

4.1 Test Specimen Description and Test Procedure

Ten round and ten flat sections of the transducers, nominally

25 cm (10 in) long, were prepared for the first portion of this test.

The shields and outer insulation were removed from both ends of the

24 See section 6.1 of this report for the yield and ultimate load

values determined by testing of the flat transducers.

42
Table 4. Strain Measurements for Freeze-Thaw Cycle Tests

Values given in table are strain in units of

10 in. /in.

Freeze--Thaw Cycles No • Mean 2 3 4 5 6 7 8 9 10

F reeze 0 - 20 -142 + 63 - 20 + 20 +102 +122 +144

<CN d>Ov Thaw +408 +443 +500 +480 +516 +489 +505 +553 +720

U

V O Diff461 408 463 642 417 536 469 403 431 576

up

ca OJ Freeze 0 - 26 -118 +632 +647 +693 +770 +726 +690

cU

<uao Thaw 418 +469 +1408 +1402 +1552 +1496 +1483 +1498 +1488

H O Diff. 800 418 495 1526 770 905 803 713 772 798

Freeze 0 + 58 - 57 +112 + 8 + 71 +100 + 35 + 60

<Uac Thaw +388 +430 +448 +465 +448 +393 +370 +398 +387

3

o Diff

366 388 372 505 353 440 322 270 363 327

< vO Freeze 0 40 - 42 125 323 401 488 634 1185

rHU

0)tc Thaw 349 395 464 408 785 768 922 1720 1862

0)uto o Diff

502 349 355 502 283 462 367 434 1086 677

T3

cnc m

Freeze 0 40 - 42 125 36 95 208 105 242

i- Hcuao Thaw 349 395 464 408 467 442 455 482 508

C0 o Dif f

351 349 355 506 283 431 347 247 377 266

m

Freeze 0 498 - 36 70 - 28 24 158 234 205

01ao Thaw 338 414 547 358 393 412 448 511 477

c0 O Diff

308 338 - 84 583 288 421 388 290 277 272

c

i—

Freeze 0 198 -106 125 87 111 164 196 192

cuat Thaw 437 987 582 534 565 560 562 630 612

O Diff. 500 437 789 688 409 478 449 398 434 420

oo F reeze 0 75 15 482 470 544 694 790 833

<

m <uat Thaw 487 554 858 878 960 1000 1062 1273 1336

o o Diff. 501 487 479 843 396 490 456 368 483 503

3

"3

Cfl Freeze 0 - 36 167 25 - 41 - 12 24 12 10

3

U

0)au Thaw 492 497 530 468 455 432 415 431 428

H co o Diff. 444 492 533 363 443 496 444 391 419 418

Gage

9

Freeze 0 11 - 92 100 54 72 132 103 98

Thaw 287 307 375 366 388 368 366 377 388

Dif f

305 237 296 467 266 334 296 234 274 290

43
specimens. The shield, coil and core were then each made available

separately for connecting into a test circuit. Three modes of failure

could be detected:

an open sense coil,

a short between the shield and the coil, and

a short between the coil and the core.

A simple neon-lamp test circuit was assembled to indicate "shorts"

and "opens" and is shown in Figure 13. As soon as the leakage resistances

in the shield-to-coil or the coil-to-core circuits decreased to 200

kft or less, the "short" indicators would illuminate. The open-coil

indicator illuminate on as soon as the coil was cut open.

Both the round and flat MILES Transducer specimens were initially

tested for simulated rock-damage resistance by impressing a known load

transversely across them with a 6.4 mm (0.25 in) diameter, round steel

rod. The steel rod was placed transversely to the length of the transducer at about its mid-length. The bottom of the transducers were

supported on a simple flat steel surface. The load was smoothly increased

with a universal testing machine until a failure was indicated.

Twelve specimens each of the round and the flat transducers, nominally

20 cm (8 in) long, were then continuously loaded at nominally one-half

of their respective average failure loads for a duration of 100 hours.

The failures were noted.

4.2 Results of the Rock Damage Tests

4.2.1 Initial Tests

For the ten round transducers tested first, the average ultimate

load was 3.22 kN (725 lbf ) , with a range of 2.29 to 4.29 kN (515 to

965 lbf). Table 5 shows the failure loads and the types of failure.

In three of the ten specimens, the failure was an open sense coil.

In six of the ten specimens, the failure was a short between the shield

and the sense coil. In one specimen, the sense coil opened simultaneously

with a shield-to-coil short. There were no failures due to a short

between the sense coil and the core.

For the ten flat transducers tested first, the average ultimate

load was 17.66 kN (3970 lbf) with a range of 16.04 to 18.90 kN (3605

to 4250 lbf)

.

The lower half of Table 5 shows the failure loads and

the types of failure. In six of the ten specimens, the failure was

a shield-to-coil short. For three of the ten, the failure was a coilto-core short. In one test, a shield-to-coil short occurred simultaneously

with a coil-to—core short. There were no failures due to an open sense

coil

.

44
Figure 13. Simple indicator used in rock damage tests for detecting

open coil or short between shield and coil or coil and core.

Table 5. Failure Loads for the 25 cm Specimens

for Ultimate Load. (Rock Damage Tests)

45
4.2.2 One Hundred-Hour Tests

During the 100-hour, half-load test, one of the twelve round transducers failed immediately upon the application of the "half load".

The "half load" for the round transducers was nominally 1.670 kN (375

lbf) and 9.074 kN (2040 lbf) for the flat transducers. Each transducer

was checked seven hours later and no additional failures were noted.

At the end of 100 hours, two additional failures had occurred. In

each of the three failures of the round transducers, the failure was

a short between shield and the coil. Table 6 shows the times to failure

for the 100-hour test.

For the flat transducers during the 100-hour test, two failed

immediately upon the application of the "half load"; both were coilto-core shorts. At the end of seven hours, another flat specimen failed;

it was a shield-to-coil short. At the end of 100 hours, no further

failures had occurred. In all, three flat transducers failed. Table

6 shows the times to failure for the 100-hour test.

Figure 14 shows a photograph of the damaged shield of round transducer specimen No. 52 after the conclusion of the 100-hour test. This

was typical of all of the round transducers. The braided shield is

deformed with a number of individual strands cut.

• • Figure 15 is a photograph of round transducer specimen No. 37.

The urethane jacket, braided shield, polyester insultation and polytetraf luoroethylene insulation have been removed from over the sense coil.

A break in the sense coil can be seen. Also, one strand of the inner

core can be seen directly beneath the broken sense coil. In all instances

where the coil opened, it was a result of the load crushing a turn

of the coil against a predominant strand of the inner core. In this

particular case, a coil - to-core short also occurred.

Figure 16 shows the sense coil of flat transducer specimen No

.

71 after the 100-hour test. Note how the turn of the coil has been

flattened and spread apart. Figure 17 shows the same transducer with

greater magnification. The insulation on the coil wire can be seen

to be "blistered". This is a result of the copper wire being flattened

and the insulation being unable to "stretch" as much as the wire.

This left holes in the insulation where bare copper material is exposed.

This happened on both sides of the copper conductor.

A polyester tape was used as an insulating material between the

coil and the core. When a coil-to-core short occurred, the polyester

tape insulation was squeezed so thin that it finally spread open, leaving

the core bare. Figure 18 shows an instance where the core was exposed

through small holes in the polyester tape for flat transducer specimen

No. 72.

46
Flat

Transducers

Round

Transducers

Table 6. Time to Failure for Half-Ultimate Load

20 cm Specimens, Rock Damage Tests. (Load

on round transducers = 37b lbf; load on

flat transducer = 2043 lbf)

Time to Failure, h

Specimen

Number

51

52

53

54

55

56

57

58

59

60

61

62

71

72

73

74

75

76

77

78

79

80

81

82

Open

Sense Coil

Short

Shield-to-Coil

100 h

0 h

100 h

7 h

Coil-to-Core

0 h

0 h

Jacket

Penetrated

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

Yes

Yes

No

Yes

No

No

No

No

No

No

No

No

No

No

No

No

47
Figure 14. Damaged braid shield of round transducer specimen No. 52

after a 100-hour exposure at a 375- lbf load.

Figure 15. An open sense-coil winding of

round transducer specimen No. 37.

Figure 16. The sense-coil winding

of flat transducer

specimen No. 71 after

a 100-hour exposure at

a 2043-lbf load.
Figure 17. Smashed sense coil for flat transducer specimen No. 71

after an exposure of 100 hours at a 2043- lbf load.

Figure 18. Damaged polyester tape insulation on flat transducer

specimen No. 72. Note holes exposing core material

beneath insulation.

49
For each of the ten round transducer specimens tested to a "full

load" failure, nine of the ten polyurethane jackets crushed to the

point where a hole had penetrated completely through the outer jacket

material. For the "half load" tests, ten of the twelve jackets ruptured.

So, even though only a few had failed electrically, ten would have

been rendered unuseable because of a penetrated jacket. Therefore,

the true failure of the round transducers was not the electrical opens

and shorts but more importantly, the penetrations of the outer polyurethane

jacket material. The load at which the jacket was penetrated was not

determined, but was generally less than the 1.670 kN (375 lbf) test

load used. In no instances were the stainless steel sheaths penetrated

in these tests, not even under the full ultimate loading of as much

as 18.90 kN (4250 lbf).

A variety of load-bearing geometries could have been used; however,

a comparative test of both the round and the flat transducers was desired,

under similar test conditions. In a test performed by other experimenters, 25 the use of a 8 mm (5/16 in) diameter round rod led to an

average load-bearing strength of 1.61 kN (363 lbf) for the round transducers. They also stated that the flat transducers appeared to be

at least 150 percent stronger than the round transducers. These conclusions are supported by the testing discussed in this report.

Overall, and under the conditions of these tests, the flat stainless

steel transducers proved far superior to the round transducers. The

flat transducers could sustain a load more than five times that of

the round transducers.

5. DURABILITY OF POLYURETHANE JACKETING

The jacketing material is a modified tetramethylene-ether glycolmethylene bis (4-phenyl diisocyanate) polyurethane elastomer. It seems

to have almost every desirable quality for this application except

a high resistance to penetration by sharp objects. Its weatherability

is only slightly less than that of some polyethylene materials. The

polyurethane has certain advantages where good sealing is important,

such as for the MILES transducers. Its tear resistance is high and,

most important of all, it exhibits excellent hydrolytic stability,

that is, moisture affects its physical or chemical properties only

to a very minor extent.

The physical and chemical properties are maintained over a very

wide temperature range. For example, the Shore A hardness and tensile

strength measured at 300 °F are about 80 percent and 50 percent of

the room temperature values, respectively. Experimental measurements

25 Manufacturer's Report No. 6464, dated January 18, 1974.

50
after exposure to 300 °F for 1500 hours in an aging test showed "...virtually no loss in tensile strength through 1000 hours of exposure" [11].

Testing in an environment of elevated gas pressures (air and oxygen)

as required by Underwriters Laboratories, as well as for military and

utilities test specifications, shows little loss of tensile strength

or elongation. The polyurethane polymer maintains good flexibility

at temperatures as low as -60 °F; embrittlement does not occur until

a temperature of about -80 °F is reached. Weatherometer and fadeometer

tests show comparable or better resistance to the natural elements

than cross-linked polyethylene, which is known to be excellent. The

electrical properties are essentially the same as for cross-linked

polyethylene. Tests predict ambient-temperature lives ranging from

several decades to several centuries (even in high humidity conditions)

[ 8 , 12 ].

An important weakness of the polyurethane jacket is its inability

to resist penetration by sharp objects, such as rocks or rodent teeth.

It offers almost no protection against gophers, for example. Three

genera of pocket gophers are reported to be the principal offenders:

Thomonys, Geomys, and Cratogeomys [13]. The plains gopher, Geomys

bursarius is generally the largest and most widely distributed of the

three. It is an accepted hypothesis that gophers are attracted to

freshly disturbed soils such as those around new cable installations.

One theory explains gopher damage as a result of the animals' natural

chewing on soft cables, believing them to be roots from which they

expect water [14] . Another theory states that gophers chew to maintain

sharp incisors and to keep them from growing too long. The depths

that gopher damage occurs at the greatest incidence is between 12 and

38 cm (5 and 15 in) and again at a depth of 1 m (40 in) . They have

been found as deep as 150 cm (60 in). 2 ^

The types of soils also have been found to be a significant factor

in gopher damage. While few voids are left by back-filling sandy soils,

5 to 13-cm (2 to 5-in) voids are often left in back-filled hard clay

soils, providing natural tunnels for the gophers. 27 Rodent-repellent

soil treatment using kerosene diluted tert-butylsulf enyl dimethyldithiocarbonate applied in a 5 cm region surrounding the buried cable is

reported as an effective gopher deterrent [15]

.

26 Welch, J. F., "Investigation of Pocket Gopher Damage to Buried

Telephone Cable in Nebraska", unpublished report 16, December 1943,

Denver Wildlife Research Center.

27 Issac, R. L., "Pocket Gopher Damage to Underground Telewire in Caddo

County, Oklahoma", unpublished report. Division of Wildlife Services,

Oklahoma City, Oklahoma, December 1956.

51
Tests on both armored and unarmored buried cables of various sizes

show that cable diameters greater than 5.33 cm (2.10 in) are unaffected

by gophers. The degree of damage is inversely proportional to the

diameter [16]. In view of this, the round MILES transducers, whose

nominal diameter is about 1.14 cm (0.45 *in), would be subject to catastrophic gopher damage if deployed in areas where gophers exist. The

polyurethane jacketing material, although excellent from the hyrolytic

stability standpoint, will not withstand gopher attack.

Prior studies of this subject by others concluded that the only

effective protection against gophers and rodents was a metallic armor

such as stainless steel [16,17]. However, it was reported that polyurethane jacket penetrations due to rodent attack or rock damage account

for only a very few of the field failures of deployed round transducers. 28

However, gopher population density was not known, but it is hypothesized

to be low, otherwise damage and failures would be known.

Several buried transducers in a test field site at Griffis Air

Force Base Site 2D were closely examined. 29 Rodent damage was not

present but other defects were. Of particular interest was a transducer

designated as MILES 96R-1. It -has been buried in that site continuously

since its installation in June, 1972. Microscopic investigations revealed

different "blemishes" on the surface of the polyurethane jacket which

can be described as scratches, abrasions, dents, pores, pits and cracks.

All except the cracks were superficially shallow, perhaps a small fraction

of a millimeter in depth, and thus considered insignificant. The cracks,

on the other hand, were much larger and deeper.

Figure 19 shows a field of small "pits" on the surface of the

jacket. This is typical of pitting seen at several places along the

transducer. _ The pit diameters are approximately 0.04 to 0.09 mm (1.5

to 3.4 x 10 3 in) and the depths appear to be about equal to the diameters.

Although these pits are, indeed, very shallow, they occur often enough

in "clusters" to make one wonder what their origins are and, further,

to raise the question of their growth rate, if any.

Figure 20 shows a large crack running in the direction of the

transducer's length. 30 Close inspection reveals that it is a split

of some type, and not a clean cut. It is approximately 8.6 mm (0.340

in) long and 0.32 mm (0.013 in) wide. The depth appears to be nearly

the entire thickness of the polyurethane jacket, which is nominally

28 Discussion held at a briefing session, Hanscom Air Force Base, Aug. 19,

1976.

9 Q _ _ _ On site inspection was done on December 17, 1975.

30 The large crack is located approximately 152 cm (60 in) from the

cylindrical boot near the cable end of the transducer.

52
Figure 19. A field of small pits observed on transducer MILES 96R-1

at Griffis Air Force Base. Pit diameters are approximately 0.04 to 0.09 mm (1.5 to 3.4 x 10 ^ in).

Figure 20. Large crack in the polyurethane jacket of transducer

MILES 96R-1 located at Griffis Air Force Base.

irr53
1.1

mm (0.045 in) thick. The origin of this crack is not known, but

it constitutes a near failure of this particular transducer. Only

one such crack was discovered in the several-meter length examined.

At this time, no other rubber-like materials are known which would

be more suitable for this application. The selection of this particular

polyether-based urethane appears to be an excellent choice. Appendix

B gives information on other materials that offer gopher protection,

and some which are known to be vunerable to gopher attack.

6. REELING AND UNREELING DURABILITY OF FLAT TRANSDUCERS

This work was done to satisfy the requirements of Task E. This

task was divided into two major parts: 1) determining the physical

strengths and characteristics of the flat transducer stainless steel

sheaths, and 2) determining the strains and equivalent forces that

the flat transducers experience during typical reeling and unreeling

operations

.

6.1

Mechanical Characteristics and Strengths

Seven specimens, about 107 cm (42 in) long, of the flat transducers

were used to determine the mechanical characteristics and strength

of the stainless steel sheath. The specimens were prepared by removing

the inner core, the sense coil and all insulation material, leaving

only the stainless steel jacket. Three of the seven specimens were

instrumented with small, foil-type, resistance strain gages. Each

gaged specimen had four gages located on both edges and both sides

at about their mid-lengths. All specimens were tested in tension in

a universal testing machine. Table 7 shows results of the laboratory

measurements and subsequent calculations. The listing below summarizes

the findings and also makes comparisons with expected values, given

in references 18 through 21, for austenitic stainless steel type 304.

Parameter

Ultimate load, lbf

Ultimate strength, psi

Elongation, %

Effective Modules, psi

Measured or

calculated value

(for transducer sheath)

1096 ± 32

93,250 ± 2710

21.7 (in 18 inches)

20.1

x 10 6

Expected value

(for flat strip)

44,000

75,000 to 100,000

40 to 71 (in 2 inches)

28 x 10 6 to 30 x 10 6

Yield load, (0.2% off set) lbf 681

Yield strength (0.2% offset) psi 57,917 28,000 to

Cross-sectional area, in 2 0.01175

54
Table 7. Results of Tensile Tests on Stainless Steel

Sheaths from Flat Transducers.

Yield Load Yield Strength Ultimate Ultimate Elongation

Specimen 0.2% Offset 0.2% Offset Load Strength % in

Number lbf psi*3 lbf psi° 18 inches

A — — 1055 89,800 23.3

A.

i — — 1130 96,200 —

B 708 60,250 897 76,300 6.3

B.

l — — 1135 96,600 —

C 664 56,500 1090 92,800 20.2

H — — 1093 93,000 22.3

I 670 57,000 1070 91,100 20,8

Mean 681 57,917 1096

a

93,250

a

21.

7

a

Std .Dev. — — + 32

a + 2710

a ,

Footnote a: Values from specimen number B were not used in calculating

the means.

b: A cross sectional area of 0.01175 in. was used in calculating

yield and ultimate strengths.
The yield strength as determined by the 0.2 percent offset method

was almost 58,000 psi. The expected range of values is 28,000 to 44,000

psi. The high value determined by testing is the result of a different

geometry than the flat strips used for the reference values. The corrugated central portion of the transducers must all stretch out prior

to the outer lips picking up the load. This same effect causes a lower

elongation and modulus than expected for flat strip specimens.

The value used for the cross-sectional area was calculated as

0.01175 in 2

. This value was determined from the dimensions given by

the manufacturer of the material from which the transducer sheath is

made. There is a chance of considerable error in the value due to

the dimensional tolerances allowed. The maximum and minimum values

for the area are (based on the manufacturer's dimensional tolerances):

Maximum area: 0.01298 in2

Nominal area: 0.01175 in2

, and

Minimum area: 0.01053 in 2

There could be as much as a 23 percent range in the value used

for the area, based on this method of calculation. Two specimens were

carefully measured in the laboratory to experimentally determine the

cross-sectional area. It was based on a measured length, measured

weight, and a reference value for density. 31 The value obtained by

this method was 0.01090 in2

, with a probable uncertainty of less than

± 1 percent. This value agrees with the formerly calculated value

to within about 7.2 percent. The value of 0.01175 in2 was used for

all of the calculations requiring the cross-sectional area since it

seemed reasonably close to the expected value.

6.2 Reeling and Unreeling Laboratory Tests

A 30-m length of flat MILES transducer was used during reeling

and unreeling tests. Two small, foil- type, resistance strain gages

were placed on the welded lips of the transducer at 7.5 m, and another

two gages at 15 m, from the free end. Gages 1 and 2 were at the 15-

m location; gage 1 was on the "outside" of the rolled transducer and

gage 2 was on the inside when rolled. Gages 3 and 4 were at the 7.5-

m location; gage 3 was on the inside and gage 4 was on the outside

when the transducer was rolled. The strain-gage bridge circuitry was

zeroed in the initial rolled-up configuration. The free end of the

transducer had a "pop rivet" placed through its thickness to help prevent the core and sense coil from sliding in and out during the reeling

31 An average density value of 0.2895 lbf/in 3 was used.

56
and unreeling operations. The transducer was unreeled and reeled a total of seven times to determine the strain differences. The transducer

was reeled and unreeled on a spool that the manufacturer typically

uses for shipping. The radius of curvature was never less than about

0.4 m (17 in)

.

The strain assumed some permanent shift in the second and third

tests, as shown in Table 8. The column means and standard deviations

shown do not include the values from test Nos. 1, 2 or 3. The strain

differences between the unrolled and rolled conditions were determined

and are shown at the bottom of the table. The grand mean of the absolute

strain differences was 463 x 10 6 in/in.

This average strain difference implies a calculated stress of

about 13,900 psi. This, compared with the yield strength of 57,900

psi determined earlier, appears reasonably low, and careful reeling

and unreeling would not be expected to cause serious problems. Taking

an extreme case where the measured strain difference was about 1000 x 10 6

in/in, the calculated stress would be about 29,000 psi. This is about

50 percent of the yield strength. It is conceivable that local stresses

could be higher, especially if the transducer were bent or twisted

beyond the 0.4-m radius limit.

Indications of exceeding the yield strength were evident from instances where "buckling" and "wrinkling" of the stainless steel sheath

occurred. It was noted that severe permanent buckling could easily

occur in the steel jacket by very slight twisting of the transducer.

In fact, in careful laboratory handling, it was difficult not to induce

buckling which caused permanent "wrinkles" in the stainless steel sheath.

Similar wrinkles were noted on transducers examined at Griffis Air

Force Base Site 2D. The end effect or seriousness of such wrinkles

was not evaluated, but it is evident that stresses greater than the

yield strength were present to cause the permanent deformations. Figures

21a, b and c show typical wrinkles of the stainless steel sheath.

The transducer was received from the manufacturer with some wrinkles

present, while additional wrinkling occurred in the course of the laboratory testing.

Microscopic examination of the flat transducer prior to, and after,

the multiple reeling and unreeling revealed no detectable cracking

anywhere along the lengths examined. However, crack detection by optical

means is difficult, at best, and small cracks may have formed and were

not detected. This would mean, of course, that the localized stresses

were greater than the ultimate material strength at the point of cracking.

The only difference noted, when the transducers were examined optically,

were additional shallow abrasions caused by dragging the transducer

across the concrete laboratory floor.
Table

8.

Results

of

Strain

Measurements

for

the

Reeling

and

Unreeling

Tests

fora

Flat

Transducer.

c

•HC

•H

CO

MO

4-1 •H

QJOc(1) VlQJ

4-1

4-1 •H03c

•H

CO

Vi

J-i

C/3

4-1Oc

CO

QJS

TOC

CO

Vi O

'rHCO

4-J OJ TO

VlO

4-J

CM

M3CO

•H

J-i a

OJ

C/3

QJ

QJ

C/0

TO

QJ M) CO 00 LO <r 00

o CO cn

rH

o

m O-i O' CMm rH CM in

rH MO

m «<rm MO

m

CO

o

++++

+

+

+

+ 1 Pi rH

QJm CO

0£ 03

cO TO

+

+ 1 O 0) O rH o o CO o m

CV rH

O rHo rH C3^ <•

m MO

•H rH

o 00

m <r

m <t

m CO 1—1 o 1—1 <—1

rH r-H rH rH i—i i—i + | vi + 4- + + + + +

4H

c

o 30

CL)

•H QJo

m CN co CO MO CO

o CM

0) rHo mi- <3* CO O'* 00

m cn To rH CO CO CO CO CO co CO CO M Csl o 1 1 1 1 1 | 1 1 + 1 pi

QJOC

m rH • CO TO CO c O OJ •H + 1 rH +

rH

o 00

c ino CMo

m MO • o o rH m rH OO MO rH CO 00 CM

to Vi

om i—1

rH

•H

C

++++

+++

+

+ 1 3o

c£31 o TO

rH QJ rH rH co co OJ co 00 MO X rH r^. m MO CM CO <r i—i

<r

o r-H rH 1—1

rH rH 1—1

rH

Pi

+ 1 i 1 1 i 1 i +i

C QJ •H OC

o CO

cO cO TO cn

Vi

O QJ 1 + 1 4-) rH o m <r CO rH ON CO in MO m

c/o 34 rHo i—1

co CN 00 MO M> 00 CO

•H

o

o i—1

CN CM rH rH i—H

rH rH <—1 u + 1 1 l l i l 1 + 1 c

4-1 30 o

0) TO

QJ 00

m CO COo MO MO

•H rH in <r

o CO

o CM CM rH

U) rH i—1

CO <r

4-1

o 1 i i i 1 I i i + 1 3 QJ pi O 00 CM CM

cO O TO i + 1 QJ rH o o rH rH CO 00 CO CK co CM

rH

omm rH MO

m MO MOm CM

o

o

m 00 00 00 00 00 00 00

Vi l l l | 1 1 1 l + 1 C

30 i TO

QJ

03 rH

OJ rH • 3 • o • O 1 1 > S-J TO > 2 rH CO m nJ QJ QJ QJ (

1 CO m r-x CT\ rH rH rH C > TJ * rH TO

4-J

e • i—1 co 3 C • 4-1 O •

QJ CM MO 00

o CN i—i cd TO 4-1 Vi TO

H rH rH rH

O QJ 4-» •H

e 4-»

O

S C/3

Q 3 CO

58

Note:

Values

from

test

nos.

1,

2,3

were

not

used

in

calculating

the

means

or

standard

deviations.
Figure 21a. Diagonal wrinkle in transducer

stainless steel sheath.

ire 21b. Diagonal wrinkle in transducer

stainless steel sheath.

Figure 2lc. Diagonal wrinkle in transducer

stainless steel sheath.

59
7. COST EFFECTIVENESS ANALYSIS

The ownership costs of MILES transducers include many factors.

Original hardware costs (transducer and accompanying electronics)

,

test equipment, maintenance, procurement costs, installation costs,

training and replacement costs are considered the major cost items.

Of these items several are essentially the same for either the flat

or the round transducer, namely, procurement, installation, training

and a portion of replacement costs.

Test equipment, more than likely, would also be the same, with

the exception that some modifications would probably be required for

the flat transducer and, in fact, some duplication of test equipment

may be needed in areas where both flat and round transducers are deployed. The transducers themselves should not require significant

maintenance over their lifetimes; however, the soil region at and near

a transducer's location does require periodic maintenance such as grass

cutting, weed removal, soil replacement in cases of erosion, etc.

Combatting rodents and other pests could also be included under the

maintenance costs. These routine maintenance costs are essentially

the same for either the flat or the round transducers with the expection

of pest control, where the stainless steel armor would be expected

to offer significantly more protection and, thus, require fewer precautions and a lower maintenance cost.

Providing that the above assumptions are correct, the items that

would have a major cost difference reduce to the original transducer

cost, the original electronics costs, and the life expectancies of

the transducer and the electronics. A further assumption is that the

replacement of batteries, and other minor maintenance, for the deployed

electronics is the same for either type of transducer system.

7.1 Original Cost-Estimate Comparisons

The original transducer costs can be compared in terms of ratios,

thus removing factors due to inflation, assuming that the same inflationary factor applies to both. Ratios between the flat and the round

transducers, and for different quantities, have been estimated.

In order for a manufacturer to begin production of stainless steel

flat transducers, there are a number of costs associated with the first

production year. These costs can be grouped into the following three

categories having the approximate proportion of costs as indicated:

60
Transducer (100 m)

Data upgrading

Tooling

Test equipment

Training

Misc. nonrecurring

Electronics

Modification to electronics

47%

6 %

47%

The percentages will vary slightly from the above figures depending

on quantities. What is important to note is that the transducer and the

electronics costs are nearly equal and are the major items and thus are

the controlling considerations in this cost analysis.

For the second, third and fourth production years, several of the

initial costs will have been paid and the overall system costs decrease.

These can be grouped into the two major categories and estimated as:

Transducer (100 m) 46%

Electronics 54%

Thus, after full production begins and continues, the relative

costs of the transducer and the electronics are about equal. Considering

all of the factors given above, the cost-estimate comparisons for both

the flat and the round transducers are given in Table 9 for the indicated

production year and for the quantities shown. The cost values have

been normalized to the system cost of the flat transducer systems in

quantities of 2500. Both the round and the flat systems include an

estimated cost of $750 for the necessary electronics. No discounts

were assumed for increased quantities of the electronics. The values

61
Table 9. Estimated Cost Comparison for New Round

and Flat Transducer Systems. (See text

and footnotes for the assumptions made.)

Production Yr. Quantity

Cost Estimate Cost Ratio

Flat/

Round

Savings/

Round*

5 Flat

0

$ioood

1500 1.150 1.071 0.931 103,500

First 2000 1.137 1.026 0.902 196,000

2500 1.134 1.000 0.882 295,000

3000 1.131 0.978 0.865 405,000

Second 2500 1.113 0.864 0.776 560,000

Third 2500 1.101 0.845 0.767 582,500

Fourth 2000 1.089 0.830 0.762 476,000

Footnotes: a. Cost estimate is given in normalized values using

the estimated cost of flat transducers in quantities

of 2500 as the normalization factor.

b. Includes the cost of the tranducer plus a value of

$750 for electronics.

c. Includes the cost of the transducer plus a value of

$750 for electronics plus other production costs for

the first year.

d. Dollar amounts shown are based on the cost of the flat

transducer system in quantities of 2500 expressed per

$1000 of cost. For example, if the transducer system

costs $1650, the net savings can be computed by

multiplying the savings/$1000 by 1.650 which equals

$486,750.

62
also include a profit factor of 15 percent. Quantity discounts for

the round transducers follow a 96 percent curve while the discount

for the flat transducers follow a 92 percent curve. The column headed

"Savings/$1000" , in Table 9, indicates the estimated cost savings for

a transducer and the electronics package, expressed in terms of the

per-$1000 cost in the quantities indicated.

Estimated savings can be calculated, using Table 9, for any of

the quantities shown when the cost per system is known. It is obvious,

from examining the table, that the greatest savings, when buying complete

new systems, occur after the first production year and when the quantities

are the greatest.

A second aspect to be considered is the situation where only a

portion of the system is to be replaced, namely, the transducer, and

the original electronics package is only modified to be compatible

with the new transducer. It is assumed, for the sake of this analysis,

that an old round transducer is being replaced with a new flat transducer.

It is also assumed that production quantities are already being delivered

and that the additional replacement transducers are available at costs

which already reflect discounts for quantity. Table 10 shows estimated

cost comparisons when old round transducers are replaced with new flat

transducers. The values have been normalized to the estimated cost

of a flat transducer plus a modified and upgraded electronics package

produced in the first year in quantities of 2500. A cost of $250 was

included for retrofitting existing electronic packages. Profit factors

and discount rates are the same as for the data shown in Table 9.

For transducer replacement, estimated savings can be calculated

by knowing the transducer cost and quantity under the above stated

assumptions and using the values given in Table 10. Again, as in Table

9, the greatest savings are realized after the first production year.

Here, however, the quantity of replacement transducers is far less

important because it is assumed that at least 2500 flat transducers

are already being produced and the quantity discounts apply to replacement transducers.

7.2 Life Expectancy and Cost

Ownership costs of MILES transducers can include many factors.

By far, the largest single cost factor for short periods of ownership

time is the original cost of the transducers and associated electronics.

It is estimated that 85 to 90 percent of the first-year cost goes into

these two items. Other factors, such as data upgrading, test equipment,

modifications and training, account for only about 10 to 15 percent

of the overall short-time costs.

63
Table 10. Estimated Cost Comparisons for

Replacement of Transducers only

(See text and footnotes for the

assumptions made.)

„ „ a Cost Estimate Cost Ratio

Flat/

Round

Savings/

Production Yr. Round^ Flat° $1000/System

First 1.104 1.000 0.906 94.00

Second 1.069 0.911 0.852 148.00

Third 1.050 0.881 0.839 161.00

Fourth 1.030 0.856 0.831 169.00

Footnotes: a. Cost estimate is given in normalized values

using the estimated cost of flat transducer systems

in quantities of 2500.

b. Cost estimate of transducer only.

c. Includes cost of $250 per system for modification

and upgrading.

d. Dollar amounts based on the cost in thousands

of flat replacement transducers. For example,

if a new flat transducer cost is $670 during the

second preduction year, the net savings for

500 transducers can be computed by multiplying

the savings/$1000/system by the transducer cost

by the quantity, or (148. 00) (0. 670) (500) = $49,580.

64
For longer periods of time, the ownership costs are largely controlled by the maintenance costs and component replacements. The two

most expensive components are the transducer and the eleectronics package. Assuming that maintenance costs are the same for the round

transducers as for the flat transducers, then the ownership cost difference between the two reduces to mainly the costs of the replacement

transducer and electronics packages.

For the sake of this analysis, the assumption is made that the

electronics packages will operate satisfactorily for much longer periods

than the transducers. 32 Tf an oversimplification of the cost algorithms

for the round and the flat transducers is made, comparison of the cost

effectiveness of one type of transducer versus the other is possible

in rather direct and simple terms using values of initial transducer

costs and life expectancies. In a situation where both the round and

the flat transducers have finite but different life expectancies, the

total long term costs can be derived from the cost of the transducer

and the number of times that the transducer must be replaced, as,

C = T£

t £ and C = T t , (1, 2)

f f f r r r

where and Cr are the total costs of the transducers for long periods

of time, T r and T are the initial costs of the transducers, and t r r £

and t are the numbers of times the transducers are replaced, an integer,

where t >_ 1

.

The subscripts f and r denote flat and round, respectively. The

number of times the transducers are replaced depends directly upon the

life of the transducer; the parameters t^. and t can be derived from

tf = N/n^ and t = N/n^, (3, 4)

where N is the time the transducers are deployed, usually expressed in

years, and n^ and n^ are the life expectancies of the transducers,

expressed in the same units of time as N.

If P is the prorata cost per time interval N, then P = C/N and

P r = t r /N and P = T t /N. (5, 6)

f f f r r r

32 Life expectancy analysis in this report is limited to consideration

of the transducers; electronics package life expectancy was not

included within the scope of these project tasks.

65
In the limit where N °° (or for practical engineering considerations,

N >> n) , the long term prorata cost, P, can be shown to be the transducer

cost divided by the life expectancy, as

P

f

T,_/n c and P = T /n . f f r r r (7, 8)

It is interesting to note that these relationships are independent

of N, so long as the inequality N >> n is met. From Eqs . (7) and (8)

one can derive a measure of cost effectiveness in terms of transducer

cost and life expectancy. When the prorata costs are equal, then the

two transducer types are equally cost effective. This condition is

established when P £ = P , as

f r

T

f n

f

T

r or (9, 10)

A cost effectiveness factor, Q, can be defined as

( 11 , 12 )

Decisions on cost effectiveness can be based on the foregoing

relationships

.

1. When Q = 1, the cost effectiveness of the flat transducer is

equal to the round transducer. (T^/T^ = n^/n^, as in Eq . (10)).

2. When Q > 1, the flat transducers are more cost effective

(T

r /Tf

> n

r /nf ).

When Q

< 1, the round transducers are more cost effective

(T /T_ < n In ) . r r r f

The savings or cost of deploying one type of transducer rather than

the other depends on the cost effectiveness and the length of time the

transducers are deployed. This can be expressed simply as

S = C

r - Cf (13)

where and are the total costs, respectively. This leads to three

economic results:

1 . When S — 0, there is no savings for one type of transducer

over the other,

66
2. When S > 0, there is a cost savings by deploying the flat

transducers, and

3. When S < 0, there is a cost loss by deploying the flat

transducers

Equation (13) can also be expressed as

S T t r r (14)

wherein t and t^ are integers and give the savings (or losses) for

short periods of time, i.e., when N is not much larger than n^_ or n^

The maximum that the savings can approach for long periods of time

when N >> n can be expressed as

S " = N (T

f

/ n

f

) (Q-l) = N (T

r /nr )(l-l/Q). (15)

* On a yearly basis, S may be divided by N to obtain the maximum possible

savings per year. This is useful for comparison purposes and removes

the effect of the fractions left over when t^ and t are made integers.

Several examples are given in Appendix C which demonstrate the usefulness of the above relationships.

In these examples and the discussions, consideration was not given

to the "logistic value" of maintaining intrusion detection, nor to

the problems and costs associated with troubleshooting transducers

which have failed, especially those which begin by generating intermittent false alarms. The final choice must, of course, consider these

and many other factors, thus making the choice between types of transducers much more complex and considerably more than simply a "cost

effectiveness" choice.

8. SUMMARY AND RECOMMENDATIONS

This section is divided into two portions; the summary, which

is organized by order of tasks, and secondly, selected recommendations

which are felt would improve the quality and durability of the transducers or would lead to better knowledge regarding their performance

and life.

8.1 Summary

In the laboratory tests, such as were performed and are reported

herein, a finite sample of specimens was selected for testing. A question is always present as to whether the tests represented conditions

of real life and whether the few specimens tested were truly representative of the large number of transducers which would ultimately

be produced and deployed.

67
It is known , in some instances, that the test conditions intentionally did not represent "real life" conditions, for purposes of accelerated

life testing. Where conditions differed, an attempt to distinguish

the important differences was made. As to whether the selected specimens

were truly representative of a large population is conjecture, for

the most part, and the reader is cautioned to bear this fact in mind.

8.1.1 Long-Term Resistance to Corrosive Moisture

Specially fabricated round and flat transducers (seven of each

type) were exposed for 120 hours to boiling saline solution mixed to

simulate sea water. Two others of each type were used to control

specimens. The individual test cycles consisted of six hours of boiling,

two hours of 100 °F drying and baking, and an overnight "rest" in an

ambient outdoor environment.

Electrical leakage resistance was measured on each transducer

at the beginning of each test cycle. When a transducer's leakage resistance became less than 20 Mfl, it was considered a "failure". After

120 hours of accumulated exposure to the hot saline solution, five

of the seven flat transducers had leakage resistances less than 20

Mft. The other two flat transducers showed signs of imminent "failure"

due to moisture penetration. Moisture penetrated in two places, either

through small corrosive pits in the weld zones of the jacket's rolled

lips, or at the "end plugs" of the transducers. Both sources of leaks

allowed significant moisture to enter the flat transducers, rendering

them useless.

It is extremely difficult to estimate an equivalent aging factor

for the 120 hours of the boiling saline solution test. Using the worst

case data available, an equivalent ambient-temperature life could be

only 26 days. This is contrasted by best case data where the ambienttemperature life would be in excess of 50 years in a chloride environment.

It is doubtful that the transducers would survive 50 years of service

but, certainly, 26 days is likewise unrealistic.

These tests did reveal the type and location of expected corrosion.

The end-plug leaks are of considerable concern and probably would control the life of the transducer in a large number of instances.

Only one of seven round transducers failed during the 120 hours

of test exposure. The steam heating line broke loose during one test

cycle, allowing it to flail inside the tank. It apparently slashed

one round transducer, cutting through the polyurethane jacket. The

remaining six round transducers tested showed signs of decreasing electrical leakage resistance. This was attributed to changes in the dielectric

properties of the insulation material within the transducers, and not

to moisture penetration. The jacket lost its bright, shiny appearance

and decreased in hardness. Also, the jacket had a tendency to become

68
loose over the braided shield, indicating a dimensional instability

of the urethane. Using test data from other researchers, the equivalent

test time would be 25 years, based on the same decrease in Shore A

hardness (7.8 percent) and an ambient temperature of 50 °F. The transducers probably could be serviceable for longer periods because a larger

decrease in hardness certainly could be tolerated. However, hardness

alone cannot be used as the sole controlling parameter of jacket durability.

Under the conditions of this test, the round transducers proved

to be superior to the flat transducers by a large margin. In a less

severe environment (and ignoring the end plug leaks) , the margin would

not be as great.

8.1.2 Resistance to Freeze-Thaw Cycling

Seven round and seven flat 42-in long transducers were subjected

to freeze-thaw temperature cycling. The transducers were each buried

in a tray of water-saturated sand. Electrical leakage resistance and

mechanical strain were measured to determine the effects of this environment. Temperature extremes ranged from 0 °F to 100 °F. Ten cycles

were completed.

None of the round transducers showed any signs of failure. The

jackets remained shiny in appearance, the Shore A jacket hardness showed

no measureable change, the electrical leakage resistance remained high

and, in general, no effects of the freeze-thaw cycling were detectable.

One of seven flat transducers failed early in the cyling sequence.

It showed a significant decrease of leakage resistance after only two

cycles. Microscopic examination of the transducer after the completion

of the ten cycles revealed a small crack at the edge of the weld zone.

It is likely that this small region accumulated a residual stress.

The additional stress caused by the freeze-thaw cycling ultimately

caused a crack in the stainless steel jacket which penetrated its full

thickness. Strain measurements on this particular transducer were

also higher than on the other transducers by a factor of almost 2:1.

The freeze-thaw stresses alone would not be expected to have caused

the noted failure except, perhaps, for the residual stresses at the

location of the failure. Furthermore, reeling and unreeling of the

transducer during and after manufacture could have initiated a small

crack and the freeze- thaw cycling could have caused its growth.

Under the test conditions discussed, the round transducers were

superior to the flat transducers, notably because of the one failure.

Had the one flat transducer not failed, then the results would have

not been in favor of the round transducers but, rather, the two transducer types would have appeared equally resistant to freeze-thaw cycling.

69
8.1.3 Resistance to Rock Damage

Round and flat MILES transducer specimens were tested for rock

damage by impressing a known load across them with a 6.4 mm (0.25-in)

diameter round steel rod. For the initial testing, ten round and ten

flat specimens, nominally 25.4 cm (10 in) long, were loaded to failure.

For the round transducers the average failure load was 725 lbf . For the

flat transducers the average failure load was 3970 lbf.

For the 100 hour test, twelve specimens each of the round and the

flat transducers, nominally 20.3 cm (8 in) long, were continuously

loaded to nominally one-half the average failure load for a duration of

100 hours. The round transducers had a load of 380 lbf on each specimen

while the flat transducers had a load of 2040 lbf on each.

For the round transducers, one of the twelve failed immediately

upon the application of the "half load". At the end of 100 hours, two

additional failures had occurred. In each of three failures a short

between shield and the coil was noted.

For the flat transducers, two failed immediately upon the application of the "half load". At the end of 100 hours, one other failure

occurred. In all, three flat transducers failed.

For the ten round transducer specimens tested to "full load" failures, nine of the ten polyurethane jackets crushed to the point where a hole had penetrated completely through the material. For the "half

load", 100 hour tests, ten of the twelve jackets were penetrated. Even

though only a few had failed electrically, ten would have been rendered

unuseable because of a penetrated jacket. Therefore, the true failure

of the round transducers was not the electrical opens and shorts but,

rather more importantly, the penetrations of the outer polyurethane

jacket material. The load at which the jacket was penetrated was not

determined, but was less than those loads stated above.

In no case was the stainless steel sheath penetrated. Under the

conditions of these tests, the flat stainless steel transducers proved

far superior to the round transducers. The flat transducers could

sustain a load more than five times that for the round transducers.

8.1.4 Durability of the Polyurethane Jacketing

The jacketing material was a modified tetramethylene-ether glycolmethylene bis (4-phenyl diisocyanate) polyurethane elastomer. It seems

to have almost every desirable quality for this application except a high resistance to penetration by sharp objects. (It offers no protection against gophers, for example). Its weatherability is only slightly

less than some polyethylene materials. The polyurethane has certain advantages where good sealing is important, such as for MILES transducers.

70
Its tear resistance is high and it exhibits excellent hydrolytic stability. Tests predict ambient temperature lives ranging from several

decades to several centuries.

Several buried transducers, at Griffis Air Force Base Site 2D, were

temporarily dug up and examined. Of particular interest was a transducer designed as MILES 96R-1 which had been deployed since June 1972.

Microscopic observations revealed different surface "blemishes" on the

polyurethane jacket which can be described as scratches, abrasions,

dents, pores, pits and cracks. All were superficially shallow and

insignificant except for certain cracks. One crack, in particular, was

about 8.6 mm long, 0.32 mm wide, and appeared to have a depth of nearly

the thickness of the polyurethane jacket. This crack constitutes a "near failure" and would likely control the life expectancy of that

transducer

Even with the weakness of poor rodent resistance, the choice of

this polyurethane elastomer material, as compared to all other known

rubber or rubber-like materials and other elastomers, was an excellent

choice. No better material for this purpose is known to exist.

8.1.5 Reeling and Unreeling Durability of the Flat Transducers

To determine the characteristics and strength of the flat transducers, specimens about 107 cm (42 inches) long were tensile tested in a

universal testing machine, and revealed a yield strength of 57,900 psi.

This implies a calculated stress of about 13,900 psi. Compared with a yield strength of 57,900 psi, it appears reasonably low and careful

reeling and unreeling would not be expected to cause serious problems.

A 30-m length of flat MILES transducer was used to help determine

the durability during reeling and unreeling of the transducer in actual

use. Four small, foil-type, resistance strain gages were placed on the

welded lips of the transducer at 7.5 m, and another four gages at 15 m,

from the free end. The transducer was unreeled and reeled a total of

seven times to determine the strain differences. The overall average of

the absolute strain differences was 463 x 10 6 in/in between the reeled

and the unreeled conditions.

It was noted that permanent and severe buckling could easily occur

in the steel jacket by very slight twisting of the transducer. In fact,

in careful laboratory handling it was difficult not to end up with some

buckling which caused permanent "wrinkles" in the stainless steel sheath.

The end effect or seriousness of such wrinkles was not examined, but it

is evident that local stresses occur that exceed the material's yield

strength enough to cause permanent deformations. It is not known how,

or by what amount, these deformations decrease the durability of the

flat transducers.

71
8.1.6 Cost Effectiveness Analysis

Ownership costs of MILES transducers can include many factors. The

largest single cost factor (about 85 to 90 percent) for short periods is

the original cost of the transducers and necessary electronics. Other

factors are data upgrading, test equipment, modifications and training

which account for about 10 to 15 percent of the costs.

This analysis treated original costs of transducers and the related

electronic packages in terms of normalized ratios. Data, thus given,

largely remove factors of economic inflation while retaining most of the

considerations of quantity pricing and production rates. The assumptions made were stated and discussed. Comparisons between the round and

the flat transducers show that the flat transducers are less costly,

especially after the first-year non-recurring costs have been recovered.

Costs and savings can be calculated by using the estimated factors given

in Tables 9 and 10.

For long periods of time, the ownership costs are controlled by the

maintenance costs and component replacement. Maintenance costs would

probably be about the same for the round and the flat transducers.

Therefore, the long-term costs reduce to component replacement. Simplified long-term cost algorithms were given. Costs and savings can be

calculated using these algorithms for any period, and for the number of

times any one type of transducer would be replaced. A cost effectiveness factor, Q, was given in terms of transducer costs and life expectancies.

Decisions can be made by evaluating Q; when Q

= 1, the two transducers

are equally cost effective; when Q

> 1, the flat transducers are more

cost effective; when Q < 1, the round transducers are more cost effective.

Examples are given in Appendix C of this report which illustrate typical

situations.

8.1.7 Final Choice; Round or Flat Transducers?

The final choice of which transducer to deploy rests on two main

factors: 1) the cost effectiveness, and 2) the logistic-protection

effectiveness. Cost effectiveness can be estimated if costs and life

expectancy estimates are known. Unfortunately, there are still little

reliable data available with which to predict service life expectancies

with great confidence. Exact values are not required to decide cost

effectiveness. The advantage of one type of transducer over the other

can either be apparent by a wide margin ( | Q

| >>1) or the margin will

likely be small ( Q

— 1 ) . In the former instance, the decision will be

clear cut in favor of the highest cost effectiveness, barring some high

over-riding logistic consideration. When Q approaches unity, other

factors will control the decision.

72
The "logistic value" of maintaining intrusion protection, and

combatting intermittent or erratic false alarms, is difficult to assess.

Certainly, these annoying incidents have to be considered in the final

choice and are outside the realm of cost-effectiveness choices. In the

end, the choice between type of transducers will probably be a complex

decision of cost effectiveness and logistic protection.

It may, indeed, be found that the best choice is the deployment of

both round and flat transducers; for example, round polyurethane-jacketed

transducers in sandy beach regions where chlorides are a problem, and

stainless steel flat transducers where rocks and rodents are a problem.

At this time, neither transducer type answers all of the problems known

to exist in the many deployment regions.

With the evidence present at hand, it is felt that the round transducers would be the better choice until such time as the welding quality

improves and the end-plug leak problem is solved. Upon making these two

improvements, then the stainless steel flat transducers could well be

superior to the round transducers.

8.2 Recommendations

Based on the results of this work, the following recommendations

are offered which are felt would improve transducer durability, increase

cost effectiveness, or increase the knowledge regarding both. The recommendations offered should not be interpreted as the only ones needed,

but seem to be the more important ones at the moment.

8.2.1 Flat Transducers

It was apparent from examining a number of flat transducers that

manufacturing improvements are needed in the forming of the stainless

steel ribbon into sheath halves, and in the welding process. Inconsistencies in the embossing process which formed the transverse-stiffening

corrugations weaken the transducer; the extent was not determined, nor

were the consequences.

The crevices which were formed beneath the rolled lips in the

welding process created undesirable regions of highly corrosive activity,

generally known as crevice corrosion. Elimination or treatment of this

region is desirable to decrease corrosive susceptibility.

The brazing process used in securing and sealing the end plugs

needs to be improved and a method developed for testing for end-plug

leaks. One possibility would be to drill and thread a hole through the

end plug and to add a tubing fitting on which a water tight cap can be

placed. Satisfactory sealing could easily be achieved with the selection of a suitable fitting This would allow pressure testing of the

end-plug braze (as well as the whole transducer) at any time.

73
Failures of transducers deployed in the field need to be carefully

examined to determine the exact nature of such failures and data need to

be collected so that the mean time between failures can be determined.

It is felt that this would be the only meaningful method of determining

service-life expectancy.

The change of sensitivity of the transducer, that results from . natural aging and as a result of handling, needs to be determined.

8.2.2 Round Transducers

The major weakness of the round transducers appears to be their low

resistance to penetration from sharp objects or from heavy loads applied

to them, such as was done in the rock damage tests. Methods of increasing the resistance to penetration need to be examined. No specific

recommendations to this end are offered.

As was recommended for the flat transducers above, the field failures of round transducers need careful examination and data need to be

collected. Also, possible changes in sensitivity, with age or environmental conditions, need study.

9 . ACKNOWLEDGEMENTS

The author expresses thanks and appreciation to the many staff

members of the National Bureau of Standards for their efforts in performing the necessary tests, consulting with the author on the many

details of the tests and providing the author with data and information.

The following deserve special mention: Dr. L. Mordfin for his guidance

and advice throughout the project, R. L. Bloss and R. Snyder for their

advice and laboratory assistance in making strain measurements, J.

Michalak for his help in operating the universal testing machines, and

N. Halsey, 0. Owens, F. Davis, and 0. W. Price for help on several

tasks. Special recognition and thanks go to J. D. Pollard for his many

hours spent during the corrosion testing and the freeze-thaw cycling

tests, many under adverse weather and other undesirable conditions. Dr.

W. Gerhold of the Metallurgy Division gave valuable suggestions and

references.

Mr. R. Allen and A. Gurdo of the Rome Air Development Center gave

valuable guidance, as well as information and data, from first-hand

field experience.

And last, thanks are due the typists who had to trudge through the

many pages of handwritten draft and the monstrous tables to produce this

final version.

74
10.

REFERENCES

1. ASTM B117, Standard Method of Salt Spray (Fog) Testing.

2. MIL-STD-810B , Environmental Test Methods.

3. Uhlig, H. H. , The Corrosion Handbook (John Wiley and Sons,

New York, 1948)

4. Ailor, W. H. , Handbook on Corrosion Testing and Evaluation

(John Wiley and Sons, New York, 1970).

5. LaQue, F. L. , Marine Corrosion, Causes and Prevention (John Wiley

and Sons, New York, 1975)

6. Romanoff, M. , Underground Corrosion, National Bureau of Standards

Circular 579, April 1957.

7. Gerhold, W. F. and McCann, J. P. , Corrosion Evaluation of Underground

Telephone Cable Shielding Materials, paper No. 31, International

Corrosion Forum, March 22-26, 1976, Houston, Texas.

8. Gahimer, F. H. and Nieske, F. W. , Hydrolytic Stability of Urethane

and Polyacrylate Elastomers in Humid Environments, J. Electroplastics 1 (Oct. 1969).

9. Millard, E. B., Physical Chemistry for Colleges (McGraw Hill,

New York, 1941)

10. Rosato. D. V. and Schwartz, R. T. , Environmental Effects on Polymeric

Materials JL (Interscience Publishers, New York, 1968)

«* 11. Allen, K. R. , "Polyolefin Thermoplastic Rubber for Electrical/

Electronic Insulation", Proc. International Wire and Cable

Symposium , 1973.

12. Blaich, C. F., Tobias, A. R. , and Zimmerman, A. R. , "Polyurethane

Elastomers in Cable Jacketing", Wire Journal, Sept. 1970.

13. Howard, W. E. , "Tests of Pocket Gopher Gnawing Electric Cables",

Wildlife Management 17 , No. 3, July 1953, pp 296-300.

14. Gibbin, J. F., and King, W. T. , "The Damage to Lead-Sheathed

Cables by Rodents and Insects", Institute of Electrical Engineers , 101, Part 2, No. 129, May 1954, pp 123-128.

15.

Mailen, T. H. and Stansburg, R. E., "Protection of Geophysical

Communications and Power Transmission Cable Against Rodent

Species Attack by R-55 Rodent Repellant Treatment", 15th

Annual Wire and Cable Symposium , December 7-9, 1966, pp 1-5.

75
16. Connally, R. A. and Landstrom, R. E. , "Gopher Damage to Buried

Cable Materials", ASTM Materials Research and Standards , 1,

No. 12, December 1969.

17. ITT Federal Laboratories, Communications Cable for Tropical

Jungle Use, March 1964, AD437910.

18. Murphy, G., Properties of Engineering Materials (International

Textbook Co., Scranton, Pa. 1957).

19. Lyman, T., editor. Metals Handbook, Vol. 1, 8th Edition (American

Society for Metals, Novelty, Ohio 1961).

20. Anon., Aerospace Structural Metals Handbook, AFML-TR-68-115

,

(Air Force Materials Laboratory, Wright Patterson Air Force

Base, Ohio, 1970).

21. Anon., Mechanical and Physical Properties of Austenitic ChromiumNickel Stainless Steels at Ambient Temperature, Section 1,

Bulletin A (International Nickel Co., Inc., New York, N. Y. 1963).

76
APPENDIX A

RELATIVE HUMIDITY AND RAINFALL DATA

The relative humidity and rainfall data cover a period from April

30, 1976 through June 7, 1976. The data were obtained from the National

Bureau of Standards Exposure Station, Gaithersburg, Maryland, maintained

by the Materials and Composites Section (461.02), of the Structures,

Materials, and Safety Division. The Exposure Station site was less

than one-half mile from the location where the corrosive moisture tests

were performed. The relative humidity values were measured at 8 a.m.

daily.

The graphical data show both the relative humidity (in percent,

using the left ordinate) and the rainfall (in inches, using the right

ordinate) . The abscissa gives the same exposure times as in Figures

2 and 3

77
100

75

50

30

10 20 30 40 50 60 70 80 90 100 110 120

Exposure time, h

Figure A-l. Relative humidity and rainfall during testing period.

78

Rainfall,

inches
APPENDIX B

MATERIALS WHICH OFFER GOPHER PROTECTION AND THOSE WHICH ARE VULNERABLE

Listed below are materials which provide gopher protection for

wires and cables. See Reference 15 for a discussion. Even though

some of these materials offer good rodent protection, corrosion may

be a serious problem.

0.006 and 0.010 in steel

0.005 and 0.0010 in stainless steel

0.002 in Cu/0.002 in Fe/0.002 in Cu laminate

0.0005 in Cu/0.010 in Fe/0.0035 in Cu laminate

0.008 in phosphor bronze

0.010 in copper

0.010 in brass

1/8 in steel mesh (0.013 in wire)

1/4 in steel mesh (0.027 in wire)

0.005 by 0.625 in spiral bronze tape armor, 30% overlap

0.006 by 0.500 in steel tape armor

Glass reinforced epoxy tubing (0.125 in wall)

Listed below are materials which are known to be vulnerable to

gopher attack and damage. See Reference 15 for a discussion.

Aluminum shield and conductors

Asphalt flooding

Coal tar flooded jute

High density polyethylene containing tert-butylsulfenyl

dime thy ldithiocarbamate

Lead sheath

Poly(vinyl chloride), insultation and jacketing

Polycarbonate

Polyethylene - jacket and insulation

Polyethylene insulated conductors - aluminum shield

15% Polyethylene - 85% petroleum jelly blend

Polyethylene jacket coated with tert-butylsulfenyl dimethyldithiocarbamate

Polypropylene

Although polyurethane was not listed, its physical characteristics

are sufficiently similar to polyethylene that it falls into the latter

category of materials that are vulnerable to gopher attack.

79
APPENDIX C

COST EFFECTIVENESS ANALYSIS EXAMPLES

Examples given here use the relationships given in Section 7.2.

The assumptions made in developing these relationships are stated there.

The values used for costs and life expectancies are arbitrary. The

costs represent reasonably realistic estimates; however, there is a large margin for speculation regarding the realism of the estimates

of life expectancies. The reader is cautioned that the values used

in these examples can not be considered continuously realistic nor

precisely accurate.

Example I : Given that the cost of the round transducers and their

life expectancies are known, and that the estimated cost of the

new flat transducers is also known, what minimum life expectancy

must the flat transducers achieve in order to have the same cost

effectiveness as the round transducer?

Let T = $1180

r

n

r = 9 years, and

T

f = $670

n.

It is necessary to solve for the value of n^ under the conditions

that Q=l. The relationships are given in Eqs. (9), (10) or (12).

From these,

n

f “ n

r ( T

f/

T

r

) = 5.11 years.

Thus, the round and flat transducers are equally cost effective

when the less expensive flat transducer has a life expectancy of

5.11 years.

Example II ; Given that the cost of the round transducers and their

life expectancies are known and that the life expectancy of the flat

transducers is known, what is the maximum cost of the flat transducer

in order to have the same cost effectiveness?

$1180

9 years , and

7 years.

?

Let T =

r

n =

r

80
It is necessary to solve for T under the conditions of Q => 1.

Again, rearranging Eq. (12),

T

f = T

r (n

f

/n

r

> = $918

Thus, the flat transducer would cost $918 in order to have the same

cost* effectiveness as the round transducer under these conditions

chosen for this example.

Example III: Given the same conditions as in Example II except that

the flat transducer cost, T , is $670, which transducer is most cost

effective, by how much, howmany times must each transducer be

replaced

,

* and what are the cost savings (or losses) over a period of

25 years?

To determine which transducer is most cost effective, and by how much,

solve for Q from Eq. (12).

Q = (T /T r )(nJn ) = (1 . 761) (0 . 778) = 1.370

^ r f r r

Thus, from the fact that Q > 1, the flat transducer is more effective

than the round transducer by 1.370 times.

To determine how many times each transducer must be replaced, the

relationships of Eqs. (3) and (4) are used.

t = N/n = 25/9 = 2.8,

r r

tf = N/nf = 25/7 = 3.6.

Thus, the round transducer would have to be replaced twice, and again

when N = 27 years. The flat transducer would have to be replaced three

times, and again when N = 28 years.

The cost savings (or losses) can be determined by use of Eq. (14), as

S = ($1180 • 2) - ($670 • 3) = $350.

The value of S is, indeed, greater than zero and, thus, it is more

cost effective to deploy the flat transducers and there would be

a cost savings of $350 per transducer over a period of 25 years.

The maximum that could be saved, as derived from Eq . (15) and calculated on a yearly basis, is $886/25 = $35 per year. This compares

with the yearly amount calculated from $350/25 = $14 and indicates

that savings would accrue at a greater rate if the transducers

were deployed for periods greater than the 25 years selected for

this example.

81
The above three examples show only a few of the ways in which the

relationships can be used to help make an intelligent choice based on

cost effectiveness. The reader is cautioned that the true cost algorithms have intentionally been oversimplified, removing inflationary

considerations or other factors, such as the cost of labor in replacing

transducers or the costs of associated electronics.

APPENDIX D

SOIL ANALYSIS RESULTS FOR SAMPLES FROM

GRIFFIS AIR FORCE BASE SITE 2D, ROME, NEW YORK

Eight soil samples from site 2D, Griffis Air Force Base, Rome, New

York, were chemically analyzed for the following substances:

calcium

magnesium

sodium

potassium

bicarbonate

sulfate

chloride

nitrate

Each of the eight samples contained a slip of paper giving the

location from which the sample was obtained. The slips had been placed

inside the "zip-lock" plastic bags. Unfortunately, the ink was badly

diffused into the paper and the paper was deteriorated from the moisture.

As a result, information was lost on some of the locations. The samples

were reidentified with an arbitrary NBS sample number; as much of the

legible data as was recoverable are given below.

82
NBS Sample No. RADC Identifing Remarks

Sample A TRANSDUCER AQ

4_ METER LINE _

-9" DEPTH

Sample B TRANSDUCER AQ

62 METER LINE

1 FT EAST OF TRANSDUCER

4-9" DEPTH

Sample C TRANSDUCER A

2 METER LINE

’ EAST OF TRANSDUCER

4-_

Sample D (Illegible)

Sample E TRANSDUCER AG?

12? LINE

1 FT EAST OF TRANSDUCER

9 DEPTH

Sample F (Illegible)

Sample G ("9" was only legible marking)

Sample H TRANSDUCER _Q

(Remainder illegible)

The results of the chemical analysis is shown in the following

letter from the Engineering Research Center, Bureau of Reclamation.

Water content, visual clarification, and dry density information

from the same site are given in a Special Report SR 235, "Frost Penetration Measurements at the USAF Intrusion Sensor Site, Rome, New York,

197374" by Tobiasson and Atkins, September 1975, prepared by the U.S.

Army Corp of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire.

83
United States Department of the Interior

BUREAU OF RECLAMATION

ENGINEERING AND RESEARCH CENTER

P.O. BOX 25007

BUILDING 67, DENVER FEDERAL CENTER

DENVER, COLORADO 80225

432.

NOV 8 W6

National Bureau of Standards

Engineering Mechanics Section - EM219

Washington, D.C. 20234

« Dear Mr. J. Ramboz:

Enclosed are the results of chemical analysis performed on soil

samples as agreed to in your telephone conversation with

Mr. Howard Salman on September 16, 1976. The samples will be

stored for several months in case additional data is required.

Sincerely yours

Division of General Research

Enclosure

84
CHEMICAL

ANALYSIS

OF

SOIL

SAMPLES-

<rlxu

CO

n-i <D

CO <r »—

CO r^. CO

o cn

X

o • • • • • • • • a —> X v£) X a uO a a a

f—

0) AJ«p

AJ

oO

m f—1 CO O’ cn CO

•H cn

oa CNJ <3 O'

—„ z f—fj r—

OJ r-< fO|

CD r—

-o

•r-< 1-4 l—

r-J f—t i—

r—1 r—1 o p • • • * • • • co o <3

f—4 r-4 b£ XV OO <d C AJ co co

co • • tw ^3

o COO CM

p »-J I—

m

X CN

CD 3 1—

a CO

P 2 QJ (U t AJ AJ

co <o cO P c

be 0 r-4 in VO cn r- •O’

a

•H

X • • • • • • • -o p <r CO o 00 O' CM <3 0>

»-J CO <3-

m CO CO r—1 <3 CM O' I—

•r4

u t—<

E •r4 •H

CO 4-J OT -D E •H C 3 no 3 •H 0 co O' CO a 00 00 OT a W • • • • • • • • AJ E CO co r- m f"

r—

p

O AJ r*J r—

r-4 cO

u 0 a a c 0 E 01 O' X cn a o O' CM AJ

4J •H <r • • • • • • • c T) »—

a CM O’ -a a O'

o

CD

O AJ

E CO

0) T—* r-J E •H w 3 o OT •H m 03 m v* O' O' m UO cn O' 3

0) 4-J c CM O’ 00 cc r-- cn p CO bC CO > a X

cu

a

E

c 3 o 0) •H « CO o O a o o a a a •3 AJ o> 1—

cn

m <3-

aX

m CO <3

p cO

X

CO CO AJ U T3 3 C CD 4J

CO

X CO

4-J CJ CO cO 4J

cu

c

<4-1 0) 0 cn CO CD CM 3 AJ P

CO

a CO r—a

pc <llP 4) cO 2 a < CQ <_> Q w a o X O P CO CD E >- 3 AJ 3 CQ • #1 CO Z > 3 c

01 fc Z TO •r4 a > c P p

>sP - c 3 CO

P

O 0) *P 1 fJ AJ AJ E PJ P m co P <f m X oc O'. o r—

O CO •H 0

•H

p 3 oooOOo r-> r—1 a z < z E O X r- r*. r0) X E m m m uO in U0 m U0 X « 3 1 | 1 1 1 1 i 1 V O X Z Q a Q o CS o Q Q 1 r-l CM CO <3

I!
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 76-1155

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

DEVELOPMENT OF TEST METHODS FOR, AND THE EVALUATION OF,

MILES TRANSDUCERS

5. Publication Date

June 1976

6. Performing Organization Code

7. Ramboz

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.

Cost Center 2130546

11. Contract/Grant No.

Y76-901

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Department of the Air Force

Hq. ESD/ACFC-2

Hanscom AFB, MA 01731

13. Type of Report & Period

Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Work performed under the technical direction of Rome Air Development Center,

Griffis AFB, Rome, NY

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

The development of tests is discussed and results are given for two types of

Multiphenomenon Intrusion Line Sensors (MILES) transducers. The round type is

fabricated as a long coaxial line having a polyurethane outer jacket. The flat

type is a coaxial ribbon housing a type 304 stainless steel outer sheath. Five

main tasks were completed: long-term resistance to corrosive moisture, resistance

to freeze- thaw cycling, resistance to rock damage, durability of the polyurethane

jacketing, and reeling and unreeling durability of the flat transducers.

Comparative results between the two types of MILES transducers are given and

indicate that neither type is ideally suited for all field deployment environments.

Chlorides in the soil cause pit corrosion in the crevice region of the flat

transducer sheaths. Rocks and rodents penetrate the polyurethane of the round

transducers. Cost analyses are given with examples illustrating cost effectiveness,

Design recommendations are given.

!

17. 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

)

Evaluation methods; intrusion detestors; MILES transducers; sensors; test methods;

testing.

18. AVAILABILITY j | Unlimited

E For Official Distribution. Do Not Release to NTIS

Order F rom Sup. of Doc., U.S. Government Printing Office

Washington, D.C. 20402, SD Cat. No. Cl 3

£ J Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

22. Price

U SCOMM- D C 29042-P7