bluuebunny/crossref_metadata_2025 huggingface dataset:
Key Parameters Used in Modeling Pressure Loss of Fibrous Filter Media
Authors: Monson Donald R.
Published: September 2009

Accurate pressure loss modeling of randomly oriented fibrous filter structures over a broad range of solidity requires that one accurately account for the following effects:

1) Fiber crossings and the resulting effective transverse boundary proximity and shape parameters and the fiber dynamic shape factor which all vary with the average solidity.

2) Slip and transition flow effects on small fibers or at low gas densities.

3) Perturbations due to manufacturing processes and multi modal fiber size distributions which cause fiber curvature, random orientation and solidity gradients in both the transverse and axial directions.

Prominent pressure loss models of both the pore and fibrous type have been found lacking in their ability to predict measured pressure loss of randomly oriented fibrous filters made of near uniform size fibers over a broad range of solidity. A mitered cylinder layered screen like pressure loss model is described which is capable of accurately accounting for the effects described.
Automated Systems for Filter Efficiency Measurements
Authors: Remiarz Richard J. , Johnson Brian R. , Agarwal Jugal K.
Published: September 2009

New methods of filter testing have been developed which eliminate the shortcomings of previous methods. The systems are fully automated and easy to use. The systems use a continuous flow condensation nucleus counter. Filter efficiencies of 99.9999+% can be measured with these systems. One system uses monodisperse aerosols for the challenge and can measure filter efficiency as a function of particle size. The systems incorporate an air-operated filter holder assembly for ease of use. A microcomputer system is used for automation and data analysis.
Results of ASTM Round Robin Tests on Filter Efficiency Using Latex Spheres and on Airflow Resistance
Authors: Japuntich Daniel A.
Published: September 2009

A study was run to determine the appropriateness of the proposed ASTM filter efficiency standard procedure [3] at the designated limits of latex sphere diameter and face velocity. An analysis of variance of filter performance from six laboratories was performed in the form of a 22 factorial designed experiment with the variable levels: latex sphere diameter (microns) at .62, .90, 2.02 and face velocity (cm/s) at 1, 5, and 25. Observations were also made on the precision of the ASTM F778-82 Gas Flow Resistance Of Filter Media Standard.
Air Filter Testing: Current Status and Future Prospects
Authors: Rivers Richard D. , Murphy David J.
Published: September 2009

U.S. and foreign test standards for air filters used in general ventilation and as prefilters for high efficiency filters. are described. These existing standards provide means for comparing and ranking filters, but do not provide the complete information needed by air-handling system designers who need to meet specific requirements, or who want to minimize system costs and energy use. Better information about filter service life, quicker tests, and ones which are not dependent on random atmospheric dust are all needed. Committees of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) and the U.S. Department of Energy (DOE) are addressing these problems, and will add particle-size-penetration measurement to the codes.
Filter Tests to Support Gas Turbine Applications
Authors: Tatge R. Bruce
Published: September 2009

Gas Turbines are in worldwide use as prime movers, facing tremendous ranges of environment and inlet air quality. Inlet air filtration is widely used to extend the life of gas turbines and to maintain their output and heat rate. In designing an air filtration system, pressure drop, serviceability, and dust-holding capacity are almost as important as efficiency. Filter tests performed in the laboratory generally are idealized to a degree, and do not always reflect the service that filters actually experience in the field. Recommendations are made for tests which would address these concerns, particularly for self-cleaning filters, which are of increasing importance in this industry.
Industrial Fabric Filter Bag Test Methods: Usefulness and Limitations
Authors: McKenna John D. , Haley Leighton H.
Published: September 2009

Troubleshooting of a malfunctioning baghouse can often be cost-effectively guided by laboratory testing of the filter bags. Quality assurance programs of fabric can be successfully and fruitfully conducted in the lab. Bags made from different fabric candidates can be given long term, side by side, in plant comparisons, by periodic laboratory tests.

The recent recognition of the above and the increased use of fabric and bag lab testing has led to some controversy over the usefulness and limitations of the lab as a tool for better baghouse operation.

In the paper which follows a description of the tests employed, a profile of a few case histories and a discussion of the usefulness and limitations of lab testing is presented.
The Need for Standard Test Methods for Fiberglass Fabrics Used on Utility Coal-Fired Boilers
Authors: Felix Larry G. , Giovanni Dan V. , Gehri Robert P. , Smith Wallace B.
Published: September 2009

Baghouses are no longer new to the utility industry. As bags need to be replaced and the causes of bag failures determined, utility baghouse users have needed to learn more about fiberglass filter bag technology so they can write intelligent bid specifications, determine quality control procedures, and learn how to test new and used fiberglass filter fabrics. It has been found that no standard test methods exist to characterize new or used finished fiberglass fabrics used for filtration. The development of these standards for new finished fiberglass fabrics is urgently needed. The development of proper standard test methods for used fiberglass filtration fabrics is contingent on an understanding of the mechanisms which cause fiberglass filter media to fail while in service.
Fabric Filter Design: The Case of a Missing Parameter
Authors: Davis Wayne T.
Published: September 2009

The design of fabric filters for removal of particles from dust-faden gas steams is dependent on the gas and dust characteristics. While the gas characteristics and the mass concentration of the dust are generally specified, the particle size distribution and other dust characteristics described in this paper are frequently unknown. The objective of this paper is to review those dust characteristics which have been found to affect the performance and to propose methods which might be suitable to obtain these missing parameters.
Progress in Fabric Filter Technology for Utility Applications
Authors: Pontius Duane H. , Smith Wallace B.
Published: September 2009

The use of fabric filtration for controlling particulate emissions from power generating plants has proven effective, both technically and economically. In most installations, the collection efficiency of these systems is much better than is required by law. Recent developments have centered on improvements in methods for removing collected ash (dustcake) from filter bags, applications in integrated emissions control systems, and studies leading toward a better understanding of the fundamental processes involved.
Air Cleanliness Validation for Cleanrooms
Authors: Flannery James L. , Walcroft James P.
Published: September 2009

Cleanroom air cleanliness validation is becoming increasingly important with the further miniaturization and susceptibility of products to airborne contamination. The rational for validation discussed, both for particle counting and for other testing. The documents covering cleanroom air validation are described, as is the general topic of “room classification.” Topics covered include validation methodology, testing modes, and room types. Factors affecting air cleanliness are discussed as well as other testing procedures to characterize cleanroom performance.
Retention of Pipe Stiffness for Polyvinyl Chloride (PVC) Pipe Samples Exposed to Various Environments and Constant Strain
Authors: Bishop Roland R.
Published: September 2009

The key physical design parameter for flexible buried non-pressure pipe is Pipe Stiffness. The ever broadening recognition of the inherent chemical resistance of polyvinyl chloride (PVC) pipe has led to a wide range of possible new applications. The effect of environment on PVC and other plastic pipe is typically measured by weight change or strength change on unstressed samples exposed to various environments such as described in ASTM D-1784, Standard Specification for Rigid Polyvinyl Chloride (PVC) Compounds or by stress or strain crack resistance. Herein a new method of measuring the long term pipe stiffness of samples exposed to various environments is proposed. This is accomplished by monitoring the instantaneous slope of the load deflection curve as a function of time. Six-inch (150mm) long pipe stiffness samples are tested to determine the initial stiffness by the method of ASTM D-2412-87, Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel Plate Loading. The sample is then clamped in a position of fixed deflection of either 5% or 7.5%. At time intervals of 1 day, 1 week, 2 weeks, 4 weeks, 8 weeks, 16 weeks and 32 weeks the load increment is increased to produce an added deflection increment to a total deflection of 7.5% or 10%. The slope of the load-deflection curve for this new load increment is calculated for each new time interval. Data from various PVC pipe samples in environments consisting of 5% sulfuric acid, 5% sodium hydroxide, tap water and air are presented. Results for up to two years exposure are included.
Fiberglass Pipe Product Standards — An Update on Performance
Authors: Pearson Lee E.
Published: September 2009

Widespread use of a piping product will only be achieved when there are detailed comprehensive product performance standards that can be confidently utilized by the specifying engineer. These standards should establish the performance criteria and requirements so that products made by different processes and materials can be validly evaluated and compared on the most important basis — performance.

Fiberglass pipe product standards issued by ASTM and the American Water Works Association have undergone substantial changes over the past few years. Among these significant changes have been the expansion to multiple stiffness ranges, a 50 year design basis criteria, increased deflection to crack-damage requirements, establishment of a long term ring bending strength test method, and updating and modification of test methods and performance criteria for strain corrosion and hydrostatic design basis. A major revision of the design appendix of AWWA C950 has been completed. AWWA and ASTM product standard requirements have been made consistent.

This review of fiberglass pipe product standards, the major revisions, and the upgrading of performance requirements will demonstrate that fiberglass pipe can be confidently evaluated, specified and used in a wide variety of applications.
ATVA 127 — As it Relates to Plastic Pipe Design
Authors: Schneider Hubert
Published: September 2009

The German specification ATV A 127 for static calculation of buried gravity pipes made of rigid and flexible materials is introduced. To show the handling of this regulation only for flexible pipes the set of equations is reduced to what is needed for those materials. Rules are given to work out the different types of loading and support conditions. Finally it is stated where the weak parts are and what should be done to modify it for flexible gravity and pressure pipes.
Field Experience with Fiberglass Pipe in the Middle East
Authors: Leondaris Kleovoulos G.
Published: September 2009

Glassfiber Reinforced Plastic (GRP) pipes were first introduced into the Middle East in the mid 1970's. High temperatures prevail, high and saline groundwater tables exist in coastal areas, and corrosive soils abound making GRP the ideal pipe material for water and sewer lines, cooling systems for power and desalination plants, storm-water networks, and other applications.
Recent Trends in Installation Standards for Plastic Pipe
Authors: McGrath Timothy J. , Chambers Richard E. , Sharff Phillip A.
Published: September 2009

ASTM Committees are nearing the end of long projects to revise and upgrade Standard Practices D 2321 and D 3839 for the installation of buried thermoplastic and fiberglass pipe, respectively. These revisions include improved and expanded guidance for selection of soils, control of construction procedures and compaction of backfill. The Appendices to D 2321 provide a commentary on installation issues that are critical to the long term performance of flexible pipe and specific guidance to engineers on important topics to be considered in preparing project specifications. The task group working on D 3839 is considering modifications to the deflection prediction equation that will treat flexible pipe deflection in a broader, more rational way than previous versions. This paper highlights the important revisions being addressed in these standard practices and provides background on their development.
Reduction, Reversion, Renovation:R3
Authors: Svetlik Harvey
Published: September 2009

Polyethylene pipes for industrial and nunicipal vises have been installed since 1960, thirty years ago. Insert Renewal of gravity flow sewers is a widely accepted process using high density polyethylene pipe (ie: a pipe in a pipe). The placement of high density polyethylene (HUE) liner in a high pressure metal pipe began in the early 1960's. That 60's technology was advanced during -the 1980's using an expanded liner approach based on the ductility, toughness, and durability of HDPE, as well as using more effective installation equipment, product design, and construction methods. Ihe 1980's innovations were directed towards longer distance, higher pressure, transport pipelines in sizes of 2" (51mm.) through 24" (610mm.) diameter. During the last decade, a new proliferation of HDPE lining products and processes have evolved to meet the challenges of the 1990's. This paper briefly evaluates the requirements and effect of each design and installation approach on the HDPE liner. The growing industry of HDPE lining of pipes has expanded to oil patch downhole tubulars, transport pipelines (oil, gas, and product), industrial/municipal water and gas distribution mains, and in some cases, nunicdpal sewers. The four generic processes considered herein are: 1. liner Expansion 2. liner Rolldown Reduction 3. liner Hat Swage Reduction 4. liner Visco-elastic Reducticn
“Cured-In-Place Pipe: An end User Assessment”
Authors: Hannan Philip M.
Published: September 2009

Trenchless technology is rapidly entering the North American marketplace as demand creates an increasing need for cost-effective pipe renovation. One of these technologies is Cured-In-Place Pipe (CIPP). Generally, these lining processes consist of a resin impregnated flexible tube, inserted into the existing pipeline by winch, air pressure or hydrostatic head, and cured to final structural properties through the application of heat. CIPP technology will be reviewed and its position in the marketplace discussed. Factors affecting selection of this type of process will be assessed. Performance criteria and installation requirements will also be discussed.
Use of Continuum Buckling Theory for Evaluation of Buried Plastic Pipe Stability
Authors: Moore Ian D. , Selig Ernest T.
Published: September 2009

A buckling theory for design of buried plastic pipes is described, which combines linear shell stability theory for the structure with elastic continuum analysis for the assessment of ground support. The theory provides stability estimates which are superior to those generated using ‘spring’ models for the soil, predictions of phenomena such as long-wavelength crown buckling without the need to pre-guess the deflected shape, and rational assessment of the influence of shallow cover and the quality and quantity of backfill material. As well as describing the continuum buckling theory, the literature is briefly reviewed, buckling as a performance limit for buried plastic pipe is discussed, and the selection of appropriate soil and polymer moduli for use in the theory is also considered.
Plastic Pipes Under High Landfills
Authors: Watkins Reynold K.
Published: September 2009

Plastic pipes have long life because of their resistance to corrosion and erosion. Consequently, they are attractive for use under long-term landfills and in aggressive environments such as sanitary landfills. But sanitary landfills are usually high landfills. Tests at Utah State University investigated the performance of plastic pipes under high landfills. It was found that a plastic pipe can perform under enormous soil loads -- hundreds of feet -- if an envelope of carefully selected soil is carefully placed about the pipe. The creep of plastic materials allows the pipe to relax and so to conform with the soil in a mutually supportive pipe-soil interaction.
15 Year Old Polyvinyl Chloride (PVC) Sewer Pipe; A Durability and Performance Review
Authors: Bauer Dennis E.
Published: September 2009

A sample of 15 year old 257 mm (nominal 10 inch) diameter Polyvinyl Chloride (PVC) sewer pipe was excavated and tested in accordance with the ASTM standards to which it was manufactured. Test results for standard requirements such as workmanship, dimensions, flattening, impact resistance, pipe stiffness, joint tightness and extrusion quality are presented and compared to current requirements of ASTM D 3034, “Standard Specification for Type PSM Poly(Vinyl Chloride) (PVC) Sewer Pipe and Fittings.” This information serves as a basis for review of the physical durability of PVC sewer pipe.

A substantial amount of initial installation data was available for this particular sewer project. Information such as bedding and haunching requirements and initial deflections were retrievable as well as original plans. Several pre-excavation procedures were completed in an effort to assess current performance. These included a review of City maintenance records, measuring depth of flow, televising the line and pulling a deflection mandrel. Actual in-situ soil classifications and density measurements were completed as the excavation proceeded. This information serves as a basis for a review of the performance of the PVC sewer line.
Elevated Temperature Resistant Metal-to-Metal Adiiesives Derived from Organic-Inorganic Polymer Systems
Authors: Janis Edward C.
Published: September 2009

Privent day organic adhesives for elevated temperature resistant metal-to-metal bonded structures are primarily of a phenolic or epoxy modified phenolic nature. Each can produce bonded joints able to withstand short time exposure at temperatures ranging from 500 F to 1000 F and still yield useful structural strength.
Preliminary Evaluation of Ceramic Adhesives for Stainless Steel
Authors: Gates L. E. , Lent W. E.
Published: September 2009

Stainless steel honeycomb structures are being considered for wings and control surfaces of advanced missiles. To meet the structural and environmental requirements, the honeycomb assemblies must be bonded with an adhesive whose strength is satisfactory to temperatures of 1200 to 1500 F.
Tensile Shear Strength of Adhesive Bonded Metals as a Function of the Rate of Loading
Authors: George Desmond A. , Butzlaff Harry R. , Mandel John
Published: September 2009

An interlaboratory test program was devised by ASTM Committee D-14 on Adhesives to study the effects of the rate of loading of the ultimate tensile shear strength of metal-to-metal adhesive-bonded lap-shear specimens. Two metals, three adhesives, two overlap lengths, and four rates of loading were studied. The tensile shear specimens tested at rates of stressing from 600 to 2000 psi per min showed very little change in strength due to the rate of stressing. For a given rate of stressing the rate of strain which was observed by changes in crosshead speed increased as the modulus of elasticity of adhesives decreased. It is not possible, therefore, to express one rate of stressing as being equivalent to a particular rate of strain for adhesives that have different moduli of elasticity.
The Use of Water in Atomic Reactors
Authors: Huntley H. W. , Untermyer S.
Published: September 2009

An ample supply of cooling water is a prerequisite for any large-scale atomic enterprise. Since presently conceived atomic power plants have lower thermal efficiencies than modern steam plants, more cooling water is required for the same electric output (Table I); also, reactor plants can be expected to be much more sensitive to the economics of cooling water supplies.
Special Corrosion Study of Carbon and Low-Alloy Steels
Authors: Blaser R. U. , Owens J. J.
Published: September 2009

A great deal has been published on the use of carbon steel as a structural material; on corrosion problems in hot water, steam boilers, and heat transfer applications; and on water treatment procedures to inhibit such corrosion. It is therefore surprising to find little, if any, quantitative corrosion data on carbon steel in high-temperature pure water. This is particularly disappointing if one is interested mainly in quantitative amounts of corrosion as actual metal lost, in the form of some average figure of weight per unit area. The support of various government agencies and prime contractors has enabled procurement of such data reported in this paper.
Standardization in Poland
Authors: Boleslaw Mrozowski
Published: September 2009

The name of the National Standardization Organization in Poland is “Polski Komitet Normalizacyjny” (PKN) (Polish Standardization Committee).
Standardization in Rumania
Authors:   the OSS Staff
Published: September 2009

Some work on standardization, of a sporadic nature and lacking in continuity, was begun in Rumania in 1928. Organized activity for standardization was begun in 1948 with the creation of a state institution for standards under the Council of Ministers of the Romanian Popular Republic.
Standardization in the United Kingdom
Authors: Glass H. M. , Weston G.
Published: September 2009

The United Kingdom of Great Britain and Northern Ireland is served by the British Standards Institution (BSI) as the recognized national organization for the preparation and publication of national standards.
Standardization in the USSR
Authors:   the USSR Standards Committee
Published: September 2009

In the Soviet Union, industrial standardization is considered to be of utmost importance to the State. The development of industry in accordance with a single state plan creates very favorable conditions for standardization.
Anisotropic Effects in Testing Plastics
Authors: Högberg Hilding
Published: September 2009

The anisotropy of some plastic articles, both in the mechanical and the optical senses, is well known in practice. These effects are related to the chemical structure of the material as well as to the mold design and manufacturing conditions. Standardized testing methods for examining anisotropy of plastics could provide designers and molders with more reliable data than hitherto. Examples are given of a technique for the measurement of anisotropy in different materials, and of the influence of molding conditions on anisotropy.
On the Most Suitable Specimen Shape for Testing Shear Strength of Plastics
Authors: Goldenberg N. , Arcan M. , Nicolau E.
Published: September 2009

The determination of the shear strength is one of the tests to which a material must be subjected in order to establish its behavior under different practical conditions.
The Vicat Softening Point Test Method: Correlations, Uses, and Variants
Authors: Stephenson C. E. , Willbourn A. H.
Published: September 2009

This test method has been described in an earlier publication; it has been adopted in the United Kingdom as Method 102-D of British Standard 2782 (1956) and in the United States by ASTM.

One advantage of the Vicat softening point (VSP) test is that it can be carried out on small specimens. It was therefore of interest to establish correlations between VSP values and test results by ASTM Method D 648 and B.S. 2782 Method 102-C (softening test on cantilever specimens) for a range of thermoplastics. The VSP test is not suitable for highly crosslinked materials since they cannot accommodate an indentation of 1 mm. Measurements of 110 VSP can, however, be made.

It is well known that test results by ASTM Method D 648 are affected by stress in the test specimens, and this may be a large effect if the specimens are injection molded. It was found that VSP values are not so affected, and the VSP therefore gives a measure of intrinsic softening behavior. Comparison with Method D 648 test results gives some measure of molding stresses.

Reproducibility of VSP results on crystalline plastics tends to be poor compared with the reproducibility attainable on amorphous thermoplastics. A variant of the test has advantages, namely, the use of a large area indenter (14-in. diameter) and a low load (about 100 g); temperatures measured in this way on a range of ethylene polymers were almost identical with their crystalline melting points determined by conventional optical means.
The Use of Infrared Spectroscopy in Characterization of Polymer Structure
Authors: Potts W. J.
Published: September 2009

It is well known that all molecules vibrate with certain definite frequencies, the number of different vibrations possible being 3N-6, where N is the number of atoms in the molecule. The frequencies of these various vibrations are determined by only (a) the masses of the atoms in the molecule and their geometric arrangement, and (b) the various force fields between the atoms. A knowledge of the vibrations of a molecule can hence lead to an intimate knowledge of the structure of the molecule, if we are but clever enough to make the proper interpretations.
Nuclear Resonance Studies of Polymer Chain Flexibility
Authors: Slichter W. P.
Published: September 2009

Molecular movement underlies many of the familiar properties of high polymers. It is important in such diverse phenomena as rubber elasticity, viscous flow, dielectric loss, and the melting of crystalline regions. The flexibility of polymer molecules involves not only features of structure within individual chains but also constraints between neighboring chains. There is as yet no explicit measure of what we mean by “flexibility,” but there are several important methods for detecting motion in molecules. Among these are dielectric relaxation studies and a variety of mechanical measurements. One may also deduce molecular motion from studies of structural transitions, using techniques such as X-ray diffraction and calorimetry. To these familiar techniques there has quite recently been added an important new method—nuclear magnetic resonance spectroscopy (NMR).
Fatigue Testing of Aluminum in Vacuum
Authors: Ham John L. , Reichenbach George S.
Published: September 2009

The fatigue life of type 1100-H14 commercial aluminum in reverse bending at 125 to 140 cps is about seven times longer in high vacuum than in wet air and about four times longer in high vacuum than in dry air. Life is independent of pressure in the range 760 to 10−2 torr, increases rapidly in the range 10−2 to 10−4 torr, and is again independent of pressure in the range 10−4 to 7 × 10−9 torr. There is some indication that life is longer under argon bombardment than in high vacuum. The cyclic strain causes more surface roughening in vacuum than in air.

A hypothesis based on adsorption equilibria is proposed to explain the step change in life with pressure as well as the improved life in vacuum.
Method of Test for Hydrogen Embrittlement Due to Electrolytic Cadmium Plating
Authors: Johnson B. G.
Published: September 2009

The small quantities of hydrogen that cause embrittlement of most high-strength steels require careful consideration, especially when selecting a cadmium plating process to be used for plating high-strength steels. It would be highly desirable to measure the exact quantity of hydrogen introduced by a given plating process. Unfortunately, presently available analytical methods are not sufficiently accurate to measure the small quantities of hydrogen that can cause embrittlement. An alternative is to evaluate the quantity of hydrogen present by measuring some mechanical effect of the hydrogen under carefully controlled conditions.
Effect of Decarburization on Fracture Toughness of an Ultrahigh-Strength Sheet Steel
Authors: Sheehan J. P. , Manning R. D.
Published: September 2009

In recent years the problem of brittle fracture has been one of great importance to fabricators of solid-propellant missile-motor cases, and many tests have been developed to determine the “fracture toughness” of sheet materials as a measure of their resistance to rapid crack propagation (1). After studying many of the tests proposed for the evaluation of fracture toughness, a special ASTM committee recommended the center-notch tension test for the screening of materials in laboratory tests (2).
An Analysis of Strain Gage Measurements Under Transient Heating Conditions
Authors: Johnson Curtis E.
Published: September 2009

Serious errors are sometimes encountered in strain gage data when testing is conducted in transient heating environments. Variations in thermal gradients, temperature compensation, and monitor temperature sensor locations all contribute to the inaccuracies. The temperature of a strain gage wire is different (150 F with 100 F per sec heating rates) than that of the specimen surface under or adjacent to the gage. Strain gages respond faster to a step-function heat input than do thermocouples; resistance thermometers respond at about the same rate as strain gages. Theoretically, a quartz-compensated strain gage, when installed with adequate temperature sensors and when properly calibrated, will result in more accurate data because the strain gage output is independent of the grid wire temperature.
Shear Test for Adhesive Bonds
Authors: Lunsford L. R.
Published: September 2009

The theoretical expressions presently being developed for the design and analysis of bonded joints invariably involve the shear strength and shear modulus of elasticity of the adhesive. A brief summary of currently used adhesive shear specimens indicates that these specimens do not provide a means of obtaining actual material properties. In order to obtain these data for adhesives as they occur in thin layers restrained by the relatively higher modulus of the adherends, an idealized specimen simulating the torque loading of a large-diameter, thin-walled tube has been developed.

A torsional shear load which produces peripherally uniform shear stresses in the adhesive is applied to the specimen. The maximum shear stress at failure represents the ultimate shear strength of the adhesive. By carefully measuring the adhesive strain as a function of load, the stress-strain curve and shear modulus of elasticity of the adhesive can be obtained. The test has proved to be quite sensitive to variations in adhesive quality and is currently being used to determine the material properties of various adhesives.
An Automatic Pavement Surface Distress Inspection System
Authors: Huang Y. , Xu B.
Published: September 2009

This paper presents a customized image-processing algorithm for the high-speed and real-time detection of pavement surface distresses. The algorithm was developed based on the “grid cell” analysis, in which a pavement image is divided into a grid of 8 × 8 pixel cells, and each cell is classified as a non-crack cell or a crack cell based on the statistics of the grayscales of the cell pixels. A crack cell can be regarded as a seed for crack formation. Adjacent crack seeds or seed clusters are connected to a crack segment. Each segment has it own direction and contrast traced from all seed in the path. A full crack is a connection of nearby segments with similar directions and contrasts. Most importantly, there must be a clear crack path along these segments. Because many operations are performed on the grid cells rather than on the original image, the algorithm can detect the cracks in the current image during the time when the camera is capturing a new image. Therefore, the survey can run at real time at a highway speed. The trial test results showed a good repeatability and accuracy when the system conducts multiple surveys and runs at different speeds and different weather conditions.
Analysis of Error in Pavement Ground Truth Indicators for Evaluating the Accuracy of Automated Image Collection and Analysis System
Authors: Lee Hosin , Kim Jungyong
Published: September 2009

The main purpose of this paper is to present the Automated Image Collection System (AICS) and Manual Image Analysis System (MIAS) as “ground-truth” for evaluating Automated Image Collection System (AICS) and Automated Image Analysis System (AIAS) for highway asset management. The proposed “ground-truth” is evaluated with respect to its repeatability against a traditional “ground-truth” procedure based on Manual Distress Collection System (MDCS) and Manual Distress Analysis System (MDAS). To capture digital images automatically, a vehicle mounted with a digital video camera was driven on the pavement test section. To determine the repeatability of MIAS, the images were evaluated by three individuals twice per individual. To determine the repeatability of MDCS/MDAS, the same individuals were asked to evaluate the same pavement section in the field twice per individual. Repeatability on three crack types was evaluated for two survey methods and three individuals. Overall, the average relative precisions of AICS/MIAS-based procedure by three individuals were 10, 8, and 19 % for longitudinal, transverse, and block cracks, respectively, whereas those of MDCS/MDAS-based procedure were 43, 45, and 41 % for longitudinal, transverse, and block cracks, respectively. In conclusion, the proposed AICS/MIAS-based “ground-truth” measurements can be considered as more repeatable by human operators than MDCS/MDAS-based “ground-truth” measurements.
Analysis of Surface Inertial Profiles Measured on Jointed Portland Cement Pavements
Authors: Gagarin Nicolas , Mekemson James R.
Published: September 2009

The feasibility of measuring slab curling using high-speed profilers was assessed by the Turner-Fairbank Highway Research Center of the Federal Highway Administration. The primary objectives of the study were to: (1) measure the surface profile of the concrete slabs using state-of-the-art profiling technology, (2) establish a standard procedure to identify warping and curling of the slabs using the measured surface profiles, (3) relate the changes in pavement surface profiles to the change in surface temperature, (4) determine the relationship between changes in pavement surface profile, roughness, premature transverse cracking, and construction condition, and (5) establish a standard procedure to analyze the condition of joints, including rotation and faulting, and determine the relationship between joint condition, and roughness. The paper discusses data mining on a database of 16 000 slabs measured during four time windows in a 24-h period. A visualization of all parameters and samples at all four times of the day show the groups of slabs which have cracked and are likely to crack shown by the divergence from the normal response measured in most slabs.
Probabilistic Analysis of the Creep Crack Growth Rate of Type 316LN Stainless Steel by the Monte Carlo Simulation
Authors: Kim Woo-Gon , Yoon Song-Nam , Ryu Woo-Seog , Kim Seon-Jin , Yi Won
Published: September 2009

This paper presents a probabilistic analysis for evaluating the creep crack growth rate (CCGR) of type 316LN stainless steel. The CCGR data was obtained from the creep crack growth tests, which are conducted under various applied loads at 600°C. The crack growth rate was characterized as a function of the C* fracture parameter. In order to logically obtain the B and q values in the CCGR equation of a = B(C*)q, three methods of the least square fitting method (LSFM), a mean value method (MVM), and a probabilistic distribution method (PDM) were adopted. Also, using the Monte Carlo simulation, a number of random variables was generated, and the CCGR lines were predicted probabilistically. The three methods did not show a large difference in the CCGR lines, but the PDM was most useful because the CCGR line can be evaluated with a probabilistic reliability. Both the B and q coefficients followed a lognormal distribution, even though the B ones were a little scattered for the points of the data. In the case of a standard deviation of 1 σ for the probability variables, P (B,q), the results of the MCS and the PDM for the distribution ranges of the CCGR lines were compared and discussed.
Mechanistic Studies of High-Temperature Crack Initiation in Single Crystal Materials
Authors: Busso E. P. , O'Dowd N. P. , Nikbin K.
Published: September 2009

In this work, the results of mechanistic studies of surface crack initiation due to the coalescence of microcracks from casting defects are presented. Two approaches are considered; namely, a continuum damage (CD) one and another where a microvoid is explicitly introduced in the vicinity of a notch. In both cases, a rate-dependent crystallographic theory is relied upon to describe the visco-plastic behavior of the single crystal. The numerical studies are conducted on a notched compact tension (CT) specimen with and without a single casting defect, idealized as a cylindrical void close to the notch surface. CD predictions of the formation of surface cracks under constant far-field loading, linked to the nucleation and coalescence of microcracks from internal porosities, are obtained from a recently proposed mechanistic anisotropic void growth model. In the explicit-void modeling approach, the time to crack initiation under constant load has been predicted using a strain-based failure criterion. Finite element analysis of the CT specimen revealed that, due to the strong localization of inelastic strain at the void, a microcrack will initiate in the vicinity of the void rather than at the notch surface. The numerical results have also shown that the time to crack initiation depends strongly on the applied load level and the void location. These results and those obtained from the CD predictions are compared and discussed. The applicability of a failure assessment approach, based on the linear elastic stress intensity factor to predict the crack initiation time under creep loading, is also considered.
Prediction of Scatter in Creep Crack Growth Data from Creep Failure Strain Properties
Authors: Wasmer K. , Nikbin K. M. , Webster G. A.
Published: September 2009

Procedures are available for determining the creep crack growth (CCG) properties ot materials experimentally in terms of the creep fracture mechanics parameter C*. When these properties have not been measured, predictions can be made from models of the cracking process. These models show that creep crack growth rate at a given value of C* is most sensitive to the creep ductility εf* appropriate to the state of stress at a crack tip. For plane stress conditions, it is found that εf* can be taken to be equal to the uniaxial creep ductility εf of a material and for plane strain to be given by εf/30. Hence, in this paper, uniaxial creep properties on type 316 L(N) austenitic stainless steel and two 9 %Cr steels, designated P91 and P92, in the temperature range 500–750°C are reported and scatter in the data identified from statistical analysis. For each steel, the dependence of creep ductility on stress and temperature is determined. It has been found that none of the rupture time (tR), creep strain rate (έ), and net section stress (σnet), parameters has a better relationship with the creep failure strain. Hence, none of these parameters characterizes better than the other the creep ductility's behavior. Additionally, it has been observed that although the creep failure strain of 316 L(N) is independent of these parameters, it increases with temperature. In contrast, the creep failure strain of P91 is slightly sensitive to σnet but is overcompensated by the scatter and so can be assumed stress independent. The creep failure strain of P91 is seen to be also insensitive to temperature. For P92, εf goes from a lower to an upper shelf through a transition region. Thus the best solution to characterize the failure strain behavior is to use a polynomial solution. Creep crack growth properties obtained on cracked compact tension and C-shaped specimens are also presented. Probabilistic analysis, based on Monte Carlo simulation methods, is employed to predict scatter in the creep crack growth data from scatter in the uniaxial creep properties. In most instances, close agreement is found between the experimentally measured scatter in the cracking results and that predicted from the scatter obtained from creep ductility data.
Life Prediction of Fretting Fatigue of Ti-6Al-4V
Authors: Jin Ohchang , Calcaterra Jeffrey Ronald , Mall Shankar
Published: September 2009

The present study was aimed towards improving the prediction capability of fretting fatigue life of Ti-6Al-4V. Incremental and interrupted fretting fatigue tests were conducted. Based on the crack propagation pattern observed on the fractured surface fretting fatigue life was predicted. The disappearance of contact stresses was evidenced by the change in crack growth direction from oblique to perpendicular path to the loading direction. Thus, fatigue crack initially propagated under the influence of the contact stress, and then it grew due to the applied stress amplitude to the substrate. The transition crack length between these two conditions varied between 20 to 30 μm and depended on the contact load. This enabled the prediction of short and long crack propagation life. There was good correlation between the predicted fretting fatigue life and the experimental life.
Verification of Analytical Models in a Fracture Mechanics Based Approach to Modeling Fretting Fatigue
Authors: Prost-Domasky Scott A. , Brooks Craig L. , Young Nichole
Published: September 2009

A fracture mechanics-based approach which uses Mode I Stress Intensity Factor (SIFs) to estimate the influence of fretting fatigue loads (which can consist of normal and shear contact loads, as well as bulk or far-field loads) has been proposed by Rooke and Jones (“Stress Intensity Factors in Fretting Fatigue,” Journal of Strain Analysis, Vol. 14, No. 1, 1979, pp. 1–6), who proposed a cracking scenario in which a single edge crack propagates to failure under the influence of the contact and bulk stress damage drivers. A major shortcoming of this approach is that the underlying analytical method and closed form integral equations assume that the single edge crack propagates into a semi-infinite domain or half-space. Significant differences in the stress states for finite width domains have been postulated by Fellows et al. (“Contact Stresses in a Moderately Then Strip (with Particular Reference to Fretting Experiments,” Wear, Vol. 185, 1995, pp. 235–238) among others. SIFs can be roughly correlated with stress; therefore variations in the stress states normally result in variations in the SIFs. Variations in the SIFs due to shear and normal contact loads, and due to finite width effects are quantitatively evaluated with the finite element method (FEM). Results with the finite element approach are compared to those using the Rooke and Jones method, as well as other results from the open literature.
A Robust Structural Stress Parameter for Evaluation of Multiaxial Fatigue of Weldments
Authors: Dong P. , Hong J. K.
Published: September 2009

In this paper, the applicability of a new mesh-insensitive structural stress method is examined for the evaluation of multiaxial fatigue behaviors in welded joints. The mesh-insensitive structural stress method proves to be effective in characterizing stress concentration effects in multi-axial fatigue of welded components. In seeking an effective structural stress based fatigue parameter, some well-known published test data were analyzed. These include those published by researchers, e.g., from the Electric Power Research Intitute (EPRI), the Fraunhofer-Institute for Structural Durability (LBF), the University of Illinois at Urbana-Champaign (UIUC), and the Welding Institute (TWI) under bending, torsion, and in-phase and out-of-phase loading combinations. An effective structural stress parameter has then been formulated in a form of a proposed modified Gough's ellipse for considering both in-phase and out-of-phase multiaxial loading conditions. The aforementioned multiaxial fatigue data from a total of five independent sources can be effectively correlated with a structural stress based parameter presented in this paper, without introducing any other material-related empirical parameters. The present method is rather simple to use for day-to-day finite element based fatigue evaluation of welded joints in actual structures subjected to multiaxial loading conditions.
Observations on Photo-Emission and the Process Zone of a Fatigue Crack
Authors: Patterson Eann A. , Diaz Francisco A. , Yates John R.
Published: September 2009

Cyclic loading of a solid material induces a cyclic temperature fluctuation. The thermal cycle is asynchronous with the loading cycle when the strains are elastic. This is commonly known as the thermoelastic effect. In differential thermography, a sensitive infrared camera is used to measure this temperature variation; typically of the order of a few tens of milliKelvin. Since the magnitude of the temperature variation is proportional to the dilational strain, values of the surface elastic stress can be derived. Recent advances in infrared camera technology and data processing algorithms have enabled values of effective stress intensity factor ranges and the location of fatigue cracks to be determined from temperature fluctuations around the crack tip on the specimen surface. Careful observation in the region near a crack tip reveals deviations from the asynchronous behavior of the photon signal relative to the load cycle. Phase shifts up to π/8 are commonly observed. The spatial distribution of these phase shifts exhibits characteristic features which are described and discussed. The features in this distribution appear to be associated with high elastic strain gradients, regions of plasticity and contact between the crack faces. Interpretation of the phase shift and its spatial distribution may lead to a better understanding of the mechanics of fatigue crack growth.
Effect of Microstructure on Pit-to-Crack Transition of 7075-T6 Aluminum Alloy
Authors: Jones Kimberli , Hoeppner David W.
Published: September 2009

The focus of this research was to gain an increased understanding of how microstructure influences pit growth, pit-to-crack transition, and critical crack propagation to fracture. Two thicknesses of 7075-T6 aluminum alloy were etched and subjected to corrosion fatigue in a 3.5 % sodium chloride environment. 7075-T6 aluminum alloy is of particular interest to the aging aircraft community, as this alloy has been used extensively on wing and fuselage structures for both military and commercial aircraft in the past. Testing was interrupted at various intervals to obtain information on pit generation, growth, and potential cracking. Results indicated that microstructure has a significant influence on pit-to-crack transition and fatigue crack propagation. Short cracks (< 100 μm) in a corrosion fatigue environment were strongly influenced by grain boundaries and crystallographic grain orientation. Constituent particles competed with corrosion pits as critical crack nucleation sites. Post-fracture analysis confirmed the presence of noncritical cracks within the corroded region, related to pitting and constituent particles.