bluuebunny/crossref_metadata_2025 huggingface dataset:
Representative Sampling in Location, Quality, and Size
Authors: Rowe PW
Published: March 2009

Large (260-mm) diameter samples are required to provide relevant laboratory consolidation and strength data on clay soils which exhibit a fabric of layers, varves, silt, and organic inclusions or fissures. Large clay specimens with permeable fabric can show coefficients of consolidation 103 to 104 times those measured on conventional small samples. The undrained strength of fissured clays decreases with increase in specimen size and improved representation of fabric.

Examination of initial small (76-mm) diameter continuous samples allows a selection of location, quality, and size of representative samples relevant to the geology and the engineering problems. Photographs of visual fabric are compared with laboratory data and field performance to illustrate when large samples are essential.

Use of a 260-mm thin-walled flush-tube piston sampler with 6 percent area ratio gives good quality samples. Handling and extraction of organic clays under water is necessary to prevent oxidation of rootlet channels. Laboratory test equipment is illustrated.
Loss of Strength Due to Sampling in a Glacial Lake Deposit
Authors: Adams JI , Radhakrishna HS
Published: March 2009

Large discrepancies between the undrained strength values measured by in situ vane and those measured by laboratory triaxial tests on tube samples, in a glacial lake deposit, are analyzed in terms of changes in effective stress during the sampling process. Data are presented to show that even in a relatively insensitive and reworked clay, significant loss in strength can occur due to the stress release effects of sampling at depth. The loss of strength is attributed to the loss of suction which occurs during sampling. Reconsolidating an undisturbed specimen to its estimated in situ vertical stress under Ko condition or to an equivalent isotropic stress, before running an undrained test, is shown to yield correct in situ strength, of a normally consolidated clay. A method of correcting for conventional undrained testing is proposed based on the computed loss of suction as related to change in moisture content due to swelling.
Effect of Sampling, Size, and Storage on Test Results for Marine Clay
Authors: Bozozuk M
Published: March 2009

Consolidation tests on a soft marine clay formation indicated that it was normally consolidated when the tests were performed on cores obtained with a 2-in.-diameter (54-mm) tube sampler and overconsolidated by 0.16 tons/ft2 (kg/cm2) when the tests were performed on cores obtained with a 5-in.-diameter (124-mm) tube sampler. From comparative tests on 20, 40, and 60-cm2 test specimens trimmed from a block of stiff overconsolidated marine clay, the maximum preconsolidation pressures were measured on the 40-cm2 size. Storing the block sample in a humid room at 55 F for one and a half years decreased the measured preconsolidation pressure. Coating the consolidometer rings with Teflon and molybdenum-disulphide-based grease was effective in reducing side friction.

Triaxial strength tests with pore pressure measurements were performed on the soft marine clay, sampled with both 2-in.-diameter (54-mm) and 5-in.-diameter (124-mm) tube samplers. Although the measured strengths were comparable, the tests on specimens trimmed from the 2-in.-diameter (54-mm) cores produced greater strains to failure and a smaller pore pressure parameter A than did tests on specimens from the 5-in.-diameter (124-mm) cores.
Sampling Disturbance in Champlain Clays
Authors: La Rochelle P , Lefebvre G
Published: March 2009

A comparison of the results of laboratory tests on block and tube samples shows that the “cemented” sensitive clays are disturbed severely by conventional thin-wall tube sampling. The undrained shear strength is reduced to 50 to 60 percent of its original value, and the recompression index at pressures smaller than the preconsolidation pressure is doubled. Even the effective stress parameters at low stress level are greatly affected by sampling. This effect is attributed to the presence at the contact between the clay particles of “cementation bonds” which have a high sensitivity to strain.
The Dependence of Fatigue Crack Propagation on Strain Energy Release Rate and Crack Opening Displacement
Authors: Barsom JM
Published: March 2009

Information on the growth of fatigue cracks in engineering structures is necessary for the prediction of service lives of structures subjected to fatigue loading. Thus, considerable work has been done to develop fatigue crack propagation laws. To determine the primary material parameters affecting fatigue crack growth, a review and analysis of existing fatigue crack propagation data were conducted.

The results show that the primary factor affecting fatigue crack growth rates in high yield strength steels, titanium, and aluminum is the applied energy release rate range, ΔGI, in psi ∙inches. The stress intensity factor, KI, can be related to GI by using the modulus of elasticity; consequently, crack growth rates usually are expressed in terms of ΔKI for a particular material. However, the primary factor affecting fatigue crack growth rate is ΔGI. Crack growth rates also can be expressed in terms of the crack opening displacement range, Δδ, because GI can be related to δ. By using a critical strain, crack extension criterion, analysis of crack propagation behavior for these metals suggests that a change to accelerated crack growth rates occurs when δ reaches a value of 1.6 × 10-3 in.
Material Toughness and Residual Strength of Damage Tolerant Aircraft Structures
Authors: Liu AF , Ekvall JC
Published: March 2009

Fracture tests were conducted on precracked panels reinforced with various crack stoppers. Motion pictures and continuous graphical records of load and local strains were taken during the tests. The purpose of these tests was to study variables affecting residual strength of reinforced panels. Results show that, for 2024-T3 aluminum skin panels reinforced with riveted or bonded flat straps made of various alloys, the residual strength increases with the product of reinforcement area and reinforcement strength. Reinforcement stiffness, which is of primary importance for other classes of panel configurations, was found not to be a significant variable for the panel configurations tested. A crack opening displacement model is proposed to illustrate the influence of the reinforcements, the skin fracture toughness, and the slow stable tear characteristics on the arrest of a stably propagating crack. The model helps to elucidate the interactions between skin variables and reinforcement variables.
The Significance of Fatigue Crack Closure
Authors: Elber W
Published: March 2009

Experiments on 2024-T3 aluminum alloy sheet are described which confirm the occurrence of fatigue crack closure under cyclic tensile loading. The results show that a fatigue crack can be closed at the crack tip for up to half of the loading amplitude, leaving this portion of the cycle ineffective in propagating the crack. An expression for the crack propagation rate in terms of effective stress amplitude is proposed. This expression is fitted to existing constant amplitude crack propagation data for 2024-T3 aluminum alloy. The parameters evaluated provide a better fit to the data than other empirical expressions available. Analysis of qualitative experiments on variable amplitude loading shows that the crack closure phenomenon could account for acceleration and retardation effects in crack propagation.
Fatigue Mechanisms in the Sub-Creep Range
Authors: Grosskreutz JC
Published: March 2009

A comprehensive description of the mechanisms of fatigue in metals is given for the temperature range in which creep processes are not important. The general response of materials to cyclic loading is discussed, including fatigue hardening/softening and the development of inhomogeneous plastic strains. The generation of fatigue cracks is treated by listing first the common sites for initiation and then discussing the various mechanisms for initiation which have been observed. Fatigue crack growth is described generally in terms of propagation modes and the appearance of fracture surfaces. Then the mechanisms of crack advance are considered in detail, and the effects of multiple load amplitude are included. Predictive theories of fatigue, from early “damage” theories to recent crack growth laws, are discussed in the light of fatigue mechanisms knowledge. Included is a discussion of the effects of crystal structure on fatigue strength. Finally, the practical implications of fatigue mechanisms knowledge are presented as they affect nondestructive inspection, repair of fatigue damage, the choice of fatigue-resistant materials, and development of new materials. There are 68 references to the fatigue literature.
Fatigue Damage Detection
Authors: Barton JR , Kusenberger FN
Published: March 2009

Relationships between the characterization and the nondestructive detection of fatigue damage are discussed and illustrated. Inspection methods presently used at overhaul facilities are reviewed, and examples of the equipment used and the results obtained are given. The advantages and limitations of currently used nondestructive methods are summarized. A perspective review of recent research efforts in nondestructive fatigue damage detection including descriptions of methods and typical experimental results is presented. Finally, nondestructive evaluation technology is appraised critically in relation to the desired results and practices, and this appraisal is used as a basis for a look into the future.
Avoidance, Control, and Repair of Fatigue Damage
Authors: Manson SS
Published: March 2009

A summary is presented of various methods available to the engineer for dealing with fatigue problems. Design, metallurgical, and service factors are considered. An attempt is made to provide a rational basis for each approach, resorting in each case to an understanding of the fundamental mechanism of the fatigue process.
Measuring the Apparatus Contribution to Bending in Tension Specimens
Authors: Schmieder AK
Published: March 2009

Methods are given for resolving measured bending strains into contributions from the following three sources: first, inaccuracies in the gages or their application; second, nonsymmetry of the specimen; and third, imperfections in the apparatus. The methods are applied to tests on tension specimens with three commonly used forms of grip ends. A method for correcting for inaccuracies in gage factors and gage misalignment is derived and applied. After correction by this method gage errors are insignificant. For the accurately machined, ½-in.-diameter specimen used, the specimen contribution to bending is small. The calculated apparatus contribution is most reproducible and significant when the load string has a minimum number of loose, threaded joints. The three specimens tested give bending strains well within the limit of ASTM recommended practices when the testing machine is in good condition.

A method also is explained for determining the maximum bending strain at any point in the reduced portion of the specimen. By this method it is shown that the maximum may be more than twice the value measured by using an extensometer or strain gages centered on the reduced portion.
Axiality Measurements on Fifty Creep Machines
Authors: Schmieder AK , Henry AT
Published: March 2009

Three types of creep machines were tested with a normal load string and specimen. One of these and one of a fourth type also were tested with a single rod replacing the normal load string. On the average, each type has bending strains within the ASTM allowable limits when tested at high stresses. The load strings with the higher temperature ratings also have the larger bending strains. For most machines the percent bending increases as the tensile stress decreases. Since the higher temperature tests usually are made at lower stresses, the two relationships above indicate that most of the tests at temperatures over 1800 F (1000 C) will have bending strains exceeding the allowable limits. Most of the nonaxiality of loading appears to be due to loose threads or machining imperfections in the couplings. The contributions to bending of crossed knife edge connectors, specimen imperfections, and strain gage inaccuracies are found to be small.
Plane Strain Fracture Toughness of Aluminum Alloys at Room and Subzero Temperatures
Authors: Nelson FG , Kaufman JG
Published: March 2009

Plane strain fracture toughness tests have been made at room temperature, -112, and -320 F on plates of six aluminum alloys and tempers: 2014-T651, 2024-T851, 6061-T651, 7075-T651, 7075-T7351, and 7079-T651. The data indicate that the plane strain fracture toughness, KIc, of each of the alloys at the subzero temperatures is as high as or higher than that at room temperature. At -320 F apparently valid values of KIc ranged from 4 (7075-T7351) to 23 percent (2014-T651 and 7075-T651 ) higher than at room temperature. An even larger difference was indicated for 6061-T651 (about 40 percent higher), but the specimens tested at -320 F were not thick enough to satisfy the requirements of ASTM Test E 399 - 70 T. For the alloys of most interest for cryogenic applications, 2014-T651 and 6061-T651, the critical crack sizes at cryogenic temperatures are indicated to be as large as or larger than those at room temperature when evaluated at either a fixed operating stress or a constant percentage of the yield strength.
Microfractographic Features of Stretched Zone in an Aluminum Alloy Fracture Toughness Specimen
Authors: Wolff UE
Published: March 2009

The fracture surfaces of fracture toughness specimens comprise three zones; the fatigue pre-crack, the ductile portion, and a stretched zone between those two. The ASTM Subcommittee on Fractography is working on means to correlate features of the stretched zone with fracture toughness parameters. A thorough analysis of the stretched zone of an aluminum alloy fracture toughness specimen was undertaken. Quantitative measurements of the zone width and qualitative evaluation of the zone profile on stereo electron microfractographs gave the following results: The average width of the stretched zone was 10 ± 1 μm. The range of zone widths was 0 to 23 ¼m. The profile of the stretched zone was quite varied, but, statistically, the stretched zones of the two fracture halves appear to form a V, the apex of which is the start of the ductile (dimpled) fracture.
Failure Analysis of a Bonded Honeycomb Structure: A Case Study Employing SEM
Authors: Bailey CD
Published: March 2009

The scanning electron microscope (SEM) was used in determining the causes of fracture which occurred in an adhesively bonded aluminum honeycomb sandwich panel. The panel fractured during structural tests conducted while it was submerged in water. Similar panels structurally tested in air did not fracture indicating that applied loads were not the major cause of fracture. A thorough examination of the fractured panel was conducted, and the following factors were identified as the causes of fracture : ( 1 ) Water entered the panel through the adhesive bond on the edge close-out members and then migrated from cell to cell around the edges of the honeycomb core. Porosity in the supported adhesive film and capillaries through the film, which were caused by incomplete bonding to the adhesive carrier, provided paths for water migration. (2) Water caused corrosion both on the honeycomb cell walls and at the edges of the core which were against the adhesive carrier. (3) Adhesive bonding to the core was either nonexistent or destroyed in the presence of water.

The unique features of the SEM provided a new approach to fracture analysis of specimens with complex topographical surfaces. The advantages of directly viewing the specimen in three dimensions at high magnifications are illustrated in SEM photomicrographs.
Materials in Nuclear Applications
Authors: Committee E-10  , Committee D-9  , Committee D-20  , Committee C-21
Published: March 2009

Description

Thirty papers cover Radiation Effects and Dosimetry, Post Irradiation Effects in Polymers, Industrial Water for Reactor Use and Ceramics in Nuclear Energy
Symposium on Road and Paving Materials—1959
Authors: ASTM Committee D-4
Published: March 2009

Description

Eight papers cover asphalt and aggregates for roads and paving
A Brief Survey of Empirical Multiaxial Strength Criteria for Composites
Authors: Sendeckyj GP
Published: March 2009

A brief survey of various empirical strength theories that have been proposed for anisotropic materials is given. Working equations for the various strength criteria are discussed and the best criteria are selected. Weaknesses of some of the criteria are also indicated.
Design and Fabrication of Tubular Specimens for Composite Characterization
Authors: Whitney JM , Pagano NJ , Pipes RB
Published: March 2009

An overall view of the current state-of-the-art in testing of composite tubular characterization specimens is presented. In addition to an outline of a set of equations for determining the proper tube dimensions, the problems of end attachment and fabrication are discussed.
Mechanical Behavior of Three-Dimensional Composite Ablative Materials
Authors: Adsit NR , Carnahan KR , Green JE
Published: March 2009

The mechanical behavior of a variety of three-dimensional reinforced ablative materials is investigated. The mechanical properties of these materials, which form the outermost surface of reentry vehicles and, therefore, are subjected to external loads, must be known to design the structure. Materials studied included three carbon/phenolics, a quartz/ phenolic, and a quartz/carbon material. Four different weave or reinforcement concepts were used in making these various materials: Narmcowrap, Intremold III, Omniweave, and PFR 3007. Mechanical properties were determined from tension, compression, and flexure tests. All of the tests were conducted at room temperature, and in the tension and compression tests strain gages were installed to obtain the modulus and Poisson's ratio. Results from each of the five systems are presented. Intremold III carbon/phenolic has properties that can be predicted from the properties of its constituent materials. The specimens as manufactured were not symmetrical and, hence, were not uniformly loaded, resulting in predictably lower average failure stresses. Narmcowrap carbon/phenolic was also an asymmetrical material, but the reinforcement prohibited the calculation of an expected load from constituent material properties. Attempts to separate the material into two symmetrical parts were not successful. Results from two types of Omniweave materials are also presented. These materials exhibited some nonlinear stress-strain behavior due to the weaving pattern. The final material, PFR 3007, exhibited a Poisson's ratio close to 1.0 in one direction and 0 in the orthogonal direction. Comparisons of the various materials are made with respect to mechanical behavior. An evaluation of the testing methods and procedures for this class of materials is also given.
Fatigue of Composites
Authors: Salkind MJ
Published: March 2009

Composite materials appear to offer substantial improvements over metals for application to structures subject to fatigue loadings. Their characteristic response to fatigue, however, is substantially different from that of metals. Whereas metals exhibit one failure mode, cracking, composites can exhibit one or a combination of failure modes, including fiber breakage, delamination, matrix cracking, interface debonding, and void growth. Much of the fatigue data for composites in the published literature relate to cycles to fracture, whereas composites generally exhibit changes in elastic and strength properties, which could result in structural failure at a fraction of the fracture life. In addition, the relatively flat S-N behavior exhibited by composites indicates that consideration of high amplitude, low cycle fatigue loading will be more critical than for metal structures. This paper reviews the available literature on the fatigue behavior of composites. It is suggested that fatigue test data be reported in terms of cycles to a given change in stiffness rather than cycles to fracture. It is further suggested that multiple damage detection schemes be used for both material and structural testing.
The Influence of Local Failure Modes on the Compressive Strength of Boron/Epoxy Composites
Authors: Suarez JA , Whiteside JB , Hadcock RN
Published: March 2009

The compressive strengths of boron/epoxy laminates are developed theoretically and verified by tests on coupons, honeycomb sandwich columns, and honeycomb sandwich beams. Filament fracture occurs at high stress levels but laminate strengths are limited by overall and local instability. The effects of normal (interlaminar) shear stiffness on laminate stability are found to be significant. Layer instability, sandwich face wrinkling, and sandwich face dimpling are investigated. Associated with sandwich face wrinkling are laminate local instability, separation from core (bond tensile failure or honeycomb core tensile failure), core crushing, and core shear failure. Consistent assumptions of initial laminate waviness provide good correlation between analyses and tests.
Impact Resistance of Unidirectional Fiber Composites
Authors: Chamis CC , Hanson MP , Serafini TT
Published: March 2009

Composite micromechanics and macromechanics and the miniature Izod impact test are used to investigate the impact resistance of unidirectional composites. Several composite systems are examined both theoretically and experimentally. The composites are classified theoretically with respect to their impact resistance for longitudinal, transverse, and shear modes. Experimental results are reported only for Izod impact with the fibers either parallel or transverse to the cantilever longitudinal axis. Impact resistance design criteria which evolved during this investigation are used to design hybrid composites with improved impact resistance. This is illustrated theoretically and demonstrated experimentally. The results show that in situ fiber and matrix elongation to fracture, matrix modulus, fabrication process, fiber and void volume ratios, and microresidual stresses are variables which affect the impact resistance. The ranking of composite impact resistance on the basis of measured and predicted results is in excellent agreement.
Stress Concentrations and Failure Criteria for Orthotropic and Anisotropic Plates with Circular Openings
Authors: Greszczuk LB
Published: March 2009

Theoretical solutions and results are given for stress concentrations and failure stresses in orthotropic and anisotropic composite plates. Solutions for the stresses around the opening are given for plates subjected to uniaxial, biaxial, and shear loading. The types of composites for which equations are given for stress concentration factors include unidirectional laminates, unidirectional laminates with oriented fibers, bidirectional balanced laminates, and multilayered laminates. A failure criterion based on modified Hencky-Von Mises distortion energy theory is also presented for predicting (1) the externally applied load which will initiate failure at the opening and (2) the location of the failure. The strength of composite plates with cutouts is less sensitive to stress concentrations than the strength of plates made of isotropic materials. Typical numerical results are presented for stress concentrations and strength of fiberglass/epoxy, boron/epoxy, and graphite/epoxy plates with cutouts. A test-theory comparison is also shown for stress concentrations in fiberglass plate containing circular opening and subjected to uniaxial tensile loading.
The Strength of Bolted Connections in Graphite/Epoxy Composites Reinforced by Colaminated Boron Film
Authors: Padawer GE
Published: March 2009

Fiber reinforced composites are weakened when bolt or rivet holes pierce the laminate to form mechanical joints. Premature failures occurring in the joint area have been a well recognized problem. In this investigation, unidirectional (all 0 deg), bidirectional (±45 deg), and tridirectional (0 deg, ±45 deg) graphite fiber/epoxy resin composites were fabricated to form a series of double-lap bolted joint models. These were tested to measure the joint strength effectiveness of transversely isotropic boron film colaminated locally at 6 and 12 volume percent levels. Results show that the addition of film plies to the highly directional fiber laminae increases the joint strength and stiffness up to 200 percent, the chief contribution of the boron film being high bearing strength and resistance to shear distortion. A novel test method for bolted lap joints was developed in which the bolt head pressure was maintained constant by means of preloaded springs, thus eliminating the ambiguity resulting from an inconstant contribution of the bolt clamping friction to the total joint strength. The strength weight effectiveness of boron film reinforcement in this particular application is demonstrated.
Evaluation of Unidirectional Glass-Graphite Fiber/Epoxy Resin Composites
Authors: Kalnin IL
Published: March 2009

As an all-fiberglass reinforcement is progressively replaced by graphite fiber, the longitudinal composite fracture stress and strain decrease rapidly for all loading modes except shear, accompanied by a substantial increase in the tensile and compressive stiffness. Conversely, upon introducing some fiberglass into a graphite composite, its strength declines in proportion to the decrease in graphite fiber content. The maximum torsional shear stress is approximately 8 ksi for all combinations of glass and graphite. Most of the transverse mechanical properties decrease linearly upon progressive replacement of the fiberglass by graphite. The transverse torsional shear properties are about 20 percent lower than the longitudinal ones.

The magnitude of the flexural modulus, which depends not only on the graphite content but even more so on the distance of the graphitic plies from the center plane of the laminate, may be calculated by means of the existing theory of bidirectional laminates. It is concluded that the large increase in composite stiffness upon addition of a small amount of oriented graphite fiber is the most salient characteristic of glass-graphite hybridization.
Symposium on Air Pollution Control
Authors: Committee D-22
Published: March 2009

Description

Six papers discuss the influence of weather conditions on air pollution potential on industrial areas as well as means of detection.
Symposium on Nuclear Methods for Measuring Soil Density and Moisture
Authors: ASTM Committee D-18
Published: March 2009

Description

Six papers describe nuclear methods for accurate determination of moisture content and density of soil.
Chapter 1—The Bases for Surveillance Programs
Authors: Steele LE
Published: March 2009

The Metal Properties Council (MPC) has accepted the task of obtaining data on the properties of metals in critical areas of special need for industry in the United States (U.S.). One such area involves data on radiation effects in metals used as nuclear reactor pressure vessels. The MPC Subcommittee 6 on Materials for Nuclear Reactors, among other tasks, seeks information on availability and applicability, as well as the interpretation of data on radiation effects in reactor structural materials. In 1968, Subcommittee 6 sponsored an analytical review of data produced by periodic removal of surveillance capsules for assessing radiation effects on operating reactor pressure vessels. This work was prepared for the MPC by L. E. Steele and C. Z. Serpan, Jr., and was published in 1970 by ASTM as Special Technical Publication (STP) 481, entitled Analysis of Reactor Vessel Radiation Effects Surveillance Programs [1].
Chapter 3—Radiation Surveillance Program for Combustion Engineering, Inc. Reactor Vessel Materials
Authors: Koziol JJ
Published: March 2009

The Radiation Surveillance Program for Combustion Engineering (C-E) Reactor Vessel Materials is designed to provide the operating utility with the capability of determining the radiation-induced changes in the mechanical and fracture toughness properties of the materials in the region of the reactor vessel encompassing the core. The term “materials” is used to collectively describe the metallurgical characteristics of base metal, deposited weld metal, and the heat-affected-zone (HAZ) metal. By conducting such determinations periodically, the neutron-induced changes in the initial reference temperature (RTNDT) can be assessed by direct measurement and the conservatism in the planned adjustments to plant operating parameters to compensate for the RTNDT changes can be verified.
Chapter 4—The General Electric Company Surveillance Programs for Boiling Water Reactor Pressure Vessels
Authors: Higgins JP , Kass JN
Published: March 2009

At neutron (n) fluences above a threshhold level of approximately 1017 n/cm2, exposure to neutron radiation (>1 MeV) has been shown to have a measurable effect on the mechanical properties of ferritic steels such as the low-alloy steels used for fabrication of light-water reactor pressure vessels (RPV's).
Multicylinder Test Sequences for Evaluating Automotive Engine Oils: Part 3: Sequence V-D
Authors: Committee D02
Published: March 2009

Description

The test method described in this publication has not been subjected to the ASTM Standardization Procedure. It is not a standard or standard recommended practice of the American Society for Testing and Materials.
Special Fractographic Techniques for Failure Analysis
Authors: Whiteson BV , Phillips A , Kerlins V , Rawe RA
Published: March 2009

In order to assist the investigator of service failures, work was performed using electron fractographic methods to resolve three separate problems that have not been solvable using the more conventional macro- or light microscopic techniques. Three independent problems were examined, and solutions were achieved. These were: (1) determination of fracture direction in thin sheet metal components, (2) differentiating between hydrogen embrittlement and stress corrosion in high-strength steels, and (3) determination of applied cyclic stress as a function of fatigue striation spacing.

The results of the investigation indicated that: 1. Fracture direction in thin sheet-metal components can be determined by replicating the acute angle shear lip. The direction of open dimples with respect to the fracture edge indicated the fracture direction in the plane of fracture. 2. There is reasonable evidence that stress corrosion and hydrogen embrittlement fractures in high-strength steel can be separated by the following: (a) Hydrogen embrittlement fractures initiated subsurface, while stress corrosion fractures initiated at the free surface. (b) The corrosion attack in hydrogen embrittlement fractures, if present, was random while in stress corrosion the oxidation products were more concentrated at the nucleus. (c) Stress corrosion fractures had stronger indications of secondary cracking than hydrogen embrittlement failures. (d) The fracture features on the hydrogen embrittled specimens were more clearly defined than those on the stress corrosion fractures. 3. A correlation was established between cyclic stress and fatigue striation spacing for several aluminum alloys over a wide range of alternating and mean stresses in thicknesses of 0.050 and 0.500 in. The correlation was empirically derived.
Fractography and Microstructure of Aluminum Alloys 7075-T651 and 7075-T7351
Authors: Hunter MS , McMillan JC
Published: March 2009

Specimens from 1⅜-in.-thick plate of 7075-T651 and 7075-T7351 alloys were examined by electron transmission, light microscopy, and electron fractography to relate microstructure, fracture topology, and mechanical and fracture properties. Material in the T7351 temper had a lower yield strength, smaller and more numerous fracture dimples, and an entirely transgranular fracture path. The T651 temper had a higher yield strength, fewer and larger dimples, and a partly intergranular fracture path. It was concluded that the beneficial effect of the lower yield strength more than offset the disadvantage of more numerous fracture dimple sites, and led to greater fracture toughness in the T7351 temper. The partially intergranular fracture was not significant in relation to fracture.
Techniques for Electron Microscopic Fractography
Authors: Warke WR , Nielsen NA , Hertzberg RW , Hunter MS , Hill M
Published: March 2009

The basic techniques of electron microscopic fractography are reviewed. Steps to be prior to replication for preventing damage and for cleaning are briefly covered. The three most common replication methods are discussed in detail. These methods are the plastic carbon, direct carbon, and oxide techniques. Examination techniques are also discussed covering the range for visual selection of areas to be studied through photography of representative areas. Stereoscopic viewing is given heavy emphasis because of the special advantages of this technique. Finally, the complementary technique of fracture sectioning is described.
Effect of Deep-Ocean Environment on Plastics
Authors: Muraoka JS
Published: March 2009

As part of a research program to determine the effects of the deep-ocean environments on materials, the U.S. Naval Civil Engineering Laboratory (NCEL) placed various plastic materials, such as Teflon, polyethylene, delrin, acrylics, etc., in rod form and vinyl plastics in tube form on the sea floor of the Pacific Ocean. The specimens were exposed for periods up to two years at depth of 5640 ft and one year at depth of 2370 ft. When recovered from the sea, the plastic specimens were examined for biological deterioration and marine growth. These plastics were also tested for hardness and moisture absorption. Many of the plastic specimens were damaged by marine boring organisms. Teflon absorbed the least amount of moisture while cellulose acetate absorbed the most amount of moisture during the exposure period.
Predicting Limits for Safe Application of Combustible Materials
Authors: Hilado CJ
Published: March 2009

Limits for safe application of combustible materials can be calculated on the basis of the performance characteristics of the materials and the response characteristics of the systems in which they are employed. The calculation required is a function of the criterion selected as a determinant of hazard. When the concentration of flammable volatiles or combustion products is the criterion of safety, calculations require material balances involving quantity of material, rate of evolution, and degree of ventilation.
Use of Aggregates Producing High Shrinkage with Shrinkage-Compensating Cements
Authors: Polivka M , Mehta PK
Published: March 2009

Coarse aggregate has a large influence on drying shrinkage which is one of the major causes of cracking in concrete structures. The stiffer an aggregate, the lower is the drying shinkage of concrete. Since it is not possible to alter the stiffness characteristic of an aggregate, a practical method of minimizing cracking of concrete when high-absorption or low-modulus aggregates must be used can be the application of a shrinkage-compensating cement in combination with these aggregates of marginal quality.

Data are presented showing that the use of high-absorption aggregates in combination with a Type K shrinkage-compensating cement produced concretes whose net contraction due to drying was equal to or lower than the drying shrinkage of a Portland cement concrete made with a low-absorption aggregate. The shrinkage-compensating cement concretes developed higher strength than the corresponding Portland cement concretes.

High-absorption or low-modulus aggregates when used in appropriately proportioned shrinkage-compensating concretes can meet even the most rigid shrinkage limitations specified to minimize cracking and deflections in concrete structures.
Controlled-Strain Testing Procedures
Authors: Slot T , Stentz RH , Berling JT
Published: March 2009

Experimental procedures are described for conducting fatigue investigations at high temperatures on servo-controlled testing machines. Specially developed equipment permits programming of push-pull tests on hourglass specimens with closed-loop control of either stress, axial strain, transverse strain, or plastic strain at the minimum diameter of the specimen.
Structural Ductility of High Strength Titanium Alloys
Authors: Papirno R
Published: March 2009

The concept of the ductility ratio was introduced by Gerard in 1961, as a quantitative measure of structural ductility useful design. An experimental technique for determining ductility ratio was established which involved the testing to failure of internally notched tension specimens containing a variety of stress concentration values, and this technique was applied in preliminary tests on high-strength aged beta titanium alloy. In the work reported here, more extensive test programs involving the all beta titanium alloy Ti-13V-11Cr-3Al in several thicknesses of sheet are described. The test materials were aged to give the highest strengths prior to testing. The paper presents the technique for performing the tests, the method of reducing the data, as well as giving the experimental results. The results of a literature survey of notch strength data from which ductility ratio values could be derived are also given, and from this survey the effect of decreasing the temperature in increasing the ductility ratio is demonstrated. The value of the ductility ratio varies from zero for a perfectly plastic material to unity for a perfectly brittle material. For the limited ductility alloys tested in the program the ductility ratio was in the range 0.1 to 0.2. There appeared to be a size effect evident with the thinnest sheet displaying the lowest ductility ratio values (highest ductility). The range of thicknesses tested was from 0.040 to 0.093 in. The test results lend additional experimental verification to the relation delineated by Gerard between the strength/weight ratio and the ductility ratio: σtu/ρ = 1.6 × 106 e1/6.
Biaxial Properties of Titanium Alloys at Cryogenic Temperatures
Authors: Frederick SF , Corn DL
Published: March 2009

The biaxial properties of Ti-6Al-4V and Ti-5Al-2.5Sn were determined at -423 F. Texture strengthening was found to be operative at this temperature, but the magnitude of the increase in strength over uniaxial properties could not be predicted from tension-test techniques for measuring texture strengthening. The strengths of welded joints in Ti-6Al-4V at -423 F were found to be equal to that of the textured parent metal. The dependence of texture strengthening on temperature, strain, and stress state is discussed.
Texture Strengthening and Fracture Toughness of Titanium Alloy Sheet at Room and Cryogenic Temperatures
Authors: Sullivan TL
Published: March 2009

Biaxial yield strengths as high as 1.53 times uniaxial yield strength were obtained from burst tests of 6-in.-diameter cylindrical pressure vessels (1 to 2 stress field) fabricated from two textured titanium alloys, Ti-4Al-0.2O and Ti-5Al-2.5Sn ELI. Material nominally 0.020 in. thick was tested at 70, -320, and -423 F. While the Ti-4Al-0.2O alloy generally had superior biaxial smooth properties at the three test temperatures, the Ti-5Al-2.5Sn ELI alloy exhibited less notch sensitivity at-320 and -423 F. It is demonstrated that plastic Poisson's ratio obtained from a uniaxial test could be used to characterize the degree of texture in the two alloys and provide a means for predicting biaxial strengthening.
Vertical Vibration of a Rigid Foundation Resting on Sand
Authors: Ho MMK , Burwash WJ
Published: March 2009

The Reissner-Sung elastic half-space theory has often been considered and utilized for the design and analysis of the behavior of foundations subjected to vibrations. Findings from laboratory tests performed on a model footing resting on sand were used to arrive at the degree of validity and applicability of the theory. This investigation includes the determination of the magnitudes and phase relationships of the dynamic contact pressures at various locations across the bottom surface of a relatively rigid footing as well as its force-displacement characteristics. Five different mass ratios were used. By means of the displacement functions, the experimental results are shown to be compatible.
Interactions Between Creep and Low-Cycle Fatigue in Udimet 700 at 1400 F
Authors: Wells CH , Sullivan CP
Published: March 2009

The cumulative damage concept in low-cycle fatigue with intermittent hold times was assessed for Udimet 700 at 1400 F. A 20 or 60 min period of tensile stressing in each strain cycle reduced the cyclic life in conservative agreement with the linear cumulative damage rule. However, the effect of holding compressive strain was more damaging than holding tensile strain. Similarly, the effect of creep prestrain on the subsequent fatigue behavior was more deleterious when applied in compression than in tension. Furthermore, the creep rate in compression was less than half that in tension and continuously decreased with strain.

Observations of the Bauschinger effect indicated that high internal stresses accompanied both creep and plastic deformation; these stresses are attributed to the pileup of dislocations at grain boundaries. It is postulated that the pileup is relaxed by cavitation and that the rate of deformation is governed by the growth of these cavities as they annihilate dislocations. These cavities were observed to be a source of intergranular cracking in creep and low-cycle fatigue. The rate of growth of the cavities, in turn, is affected by the hydrostatic component of stress, accounting for the decelerating creep in compression. In addition the shape of the cavities influences the rate of crack propagation and fracture toughness: round cavities promote toughness, while cavities flattened by compressive creep provide easy propagation paths.
A Statistical Evaluation of Atmospheric, In-Service, and Accelerated Corrosion of Stainless Steel Automotive Trim Material
Authors: Black HL , Lherbier LW
Published: March 2009

Stainless steel panels with various surface finishes were exposed to winter salt and ash conditions on trucks and automobiles, salt atmosphere, industrial atmosphere, and rural atmosphere for periods of one to four years. They were also evaluated by six accelerated tests either presently used by, or proposed by, the automobile industry.

Comparisons of the average results of the multiple specimens were made in an attempt to determine the relative superiority among the grades of stainless and among the surface finishes in each exposure environment. Statistical correlation coefficients were calculated to determine the degree of corrosion resistance correlation among the sites and to determine the correlation between “in-service” corrosion and the accelerated tests.

No clear superiority of any grade in all environments could be determined. With the exception of chromium flash plating, no surface finish tested was significantly superior to any other. The automobile and truck exposures showed that the varying weather conditions from one winter to another could cause unpredictable, conflicting results. The correlation between corrosion resistance and temperature, snow-fall, and de-icing agents was not clear. The statistical correlation analysis conducted showed that very limited or no correlation exists between in-service corrosion and and accelerated tests. Even among the tests, the correlation was poor or not existent. This study indicates that none of the accelerated tests evaluated can be expected to predict stainless steel corrosion performance in service.
The Effect of Initial Weather Conditions on the Atmospheric Corrosion of Aluminum and Its Alloys
Authors: Carter VE , Campbell HS
Published: March 2009

Weight losses for specimens of aluminum alloys exposed for one year to moderately severe industrial and marine atmospheres were similar for groups of specimens put out initially in winter or summer. The depth of pitting on those put out in the winter was, however, from 1½ to 2½ times as great as on those put out in the summer. The difference is explained by the specimens exposed in winter remaining covered with a film of moisture for a greater proportion of the time during their first few weeks or months on test. It is recommended that, when comparing the atmospheric corrosion resistance of aluminum alloys, tests should be started both in summer and in winter.
Corrosion Rates of Mild Steel in Coastal, Industrial, and Inland Areas of Northern California
Authors: Thomas HE , Alderson HN
Published: March 2009

The corrosion rate of mild steel specimens was determined at 15 sites in Northern California. Weight loss with time was measured. These sites included coastal, marine, bay, and steam-geyser areas. The methods of specimen preparation, corrosion product removal, and exposure location details are covered. The repeatability of the tests was checked and found to be good at two locations, and the agreement with ASTM results at the Point Reyes exposure test site was reasonably good.
Atmospheric Corrosion Behavior of Some Nickel Alloys
Authors: van Rooyen D , Copson HR
Published: March 2009

Nickel, nickel-copper, and nickel-chromium-iron alloys were included in an atmospheric corrosion test series in industrial, marine, and rural sites. Pit depths, losses in weight, and losses in mechanical properties were extremely small after a seven-year period of exposure. The nickel-iron-chromium materials had the lowest corrosion rates, about 0.01 milligrams per square decimeter per day (about 0.002 mils per year). The corrosion rates of the nickel-iron-chromium alloys appear to have decreased substantially with exposure time, while the nickel and nickel-copper alloy specimens follow approximately linear rates. Long time durability data have also been obtained for a number of nickel-copper-iron alloys. These were boldly exposed at Bayonne, N. J., for almost 40 years. Data led to the construction of isograms connecting compositions of equal durability on the nickel-iron-copper ternary diagram. Effects of exposure under shelter are also discussed.
Effects of Atmospheric Factors on the Corrosion of Rolled Zinc
Authors: Guttman H
Published: March 2009

A long term exposure program has been carried out at Birchbank, B. C., wherein rolled zinc corrosion data and certain atmospheric factor data were developed. Zinc is sensitive to variations in climatic and atmospheric pollution conditions, and as a result panels exposed on different dates for a specific period of time can corrode at different rates. An empirical equation has been developed for Birchbank which relates corrosion of zinc to the time of wetness of exposed panels and the average atmospheric sulfur dioxide content during the time panels are wet. The equation accounts for most of the observed variation in corrosion losses and is valid for exposure periods of up to 256-weeks' duration. This paper also presents information concerning the relative corrosion rates of the skyward and groundward surfaces of zinc panels, the relationship between time of panel wetness and relative humidity, and the relationship between atmospheric sulfur dioxide as measured by a Thomas autometer and by the lead peroxide method.
Toward Assessing the Effects of Crack Front Curvature (CFC)
Authors: Swedlow JL , Ritter MA
Published: March 2009

Crack front curvature (CFC) is shown to affect the K calibration of four special geometries for which analysis is currently practicable. The inference is drawn that assuming straight crack fronts in, say, test specimens having non-zero CFC may be non-conservative; the aim of this paper is to initiate further investigation of the effects of CFC.