bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Results of a Program for Developing Fracture Toughness Data on Ferritic Nuclear Pressure Vessel Steels
Authors: Stahlkopf KE , Smith RE , Server WL , Wullaert RA
Published: March 2009

A comprehensive fracture toughness testing program focused principally at providing statistical assurance of the American Society of Mechanical Engineers (ASME) KIR fracture toughness design curve is presently underway. While the overall program represents testing of 50 heats of typical production materials, including A533-B, Class 1 plate; A508, Class 2 forging; A540-B-23 and B-24, Class 3 bolting material; submerged arc, manual metal arc, and shielded metal arc weldments; and associated heat-affected zone material, the data presented herein represent the initial results of an interlaboratory round robin program and the first seven heats of A533-B Class 1 plate tested in the program. Mechanical tests performed include tension, drop weight-nil ductility transition (NDT) temperature, Charpy V-notch, instrumented precracked Charpy, static and dynamic compact fracture, and dynamic three-point bend. Of these tests, instrumented precracked Charpy, dynamic three-point bend, and dynamic compact fracture are nonstandard procedures. Methodology for performance of these nonstandard tests is outlined. The fracture mechanics tests were performed on specimens up to 1-in. thick (4-in.-thick specimens will be tested later). Loading rates ranging from quasistatic to stress intensity rates (˙K) of 5 × 105 ksi √in./s were applied.

Testing and data analysis procedures for dynamic fracture toughness testing were developed. Special emphasis was placed on the assurance of adequate electronic response in conjunction with control of the time to fracture for ensuring reliable test results. Elastic-plastic data analysis techniques were applied to test results and included both the J-integral and the equivalent energy approaches. Maximum load was used in the J-integral and equivalent energy analysis for lack of an experimental technique for determining crack initiation over a range of loading rates. It is recognized that this approach can lead to nonconservative toughness values when crack growth occurs prior to maximum load. However, for completeness elastic-plastic data analyzed using this criteria are included.
Fatigue Crack Growth and J-Integral Fracture Parameters of Ti-6Al-4V at Ambient and Cryogenic Temperatures
Authors: Tobler RL
Published: March 2009

Fatigue crack propagation and fracture parameters for 2.03-cm-thick compact specimens of an extra-low-interstitial Ti-6Al-4V alloy were measured at temperatures between 295 K (70°F) and 4 K (−453°F). Plane-strain linear-elastic and J-integral fracture toughness test results were in good agreement: the KIc values for this alloy decreased from 105 MN/m3|2 at room temperature to 54 MN/m3vb2 at 4 K, and a ductile-to-brittle fracture transition occurred in the range 125 to 76 K (−235 to −323°F). Despite this transition, the fatigue crack growth rates (da/dN) of this alloy remained temperature insensitive over the entire ambient-to-cryogenic range. These fatigue and fracture results are compared with data previously reported for a normal-interstitial Ti-6Al-4V alloy.
Effect of Cooling Rate on Fracture Behavior of Mill-Annealed Ti-6Al-4V
Authors: Lewis RE , Bjeletich JG , Morton TM , Crossley FA
Published: March 2009

Different cooling rates during duplex-annealing of mill-annealed Ti-6Al-4V 1-in. plate produce essentially indistinguishable microstructures and similar tensile properties, but significantly varying fracture properties. Duplex-annealing was performed by an initial heating at 1775°F (968.3°C) for 1/2 h and air-cooled; then reheated at 1450°F (787.4°C) for 1 h and cooled (1) by water quench, (2) in the air, or (3) in the furnace. Yield strength values, relatively unaffected by the annealing and cooling rate treatments, were grouped at 140±2 ksi (965 ± 14 MPa). Fracture toughness, however, varied from a low of 38 ksi √in. (42 MPa · √m) in the material with the fastest cooling rate (1) to nearly similar values of 50 and 51 ksi √in. (55 and 56 MPa · √m) for cooling rates (2) and (3), respectively. The stress-corrosion crack-growth, threshold stress intensities for the three cooling rates were (1) 34 ksi √in. (37.5 MPa · √m), (2) 30 ksi √in. (33 MPa · √m), and (3) 22 ksi √in (24.2 MPa · √m). Differences in fatigue crack propagation resistance brought about by the three cooling rates are illustrated with safe operating lifetimes obtained by computer simulation for a typical engineering application. The results reveal a fivefold advantage in safe life for air-cooled material. Although the fracture properties exhibited significant variation with cooling rate from the final anneal, light optical microscopy to a magnification of 3000 diameters did not reveal significant microstructural differences. Scanning electron fractographic evidence, however, is consistent with an inference that local ordering, that is, a precipitation process involving Ti3 Al, is the most probable reason for the furnace-cooled material's more rapid fatigue-crack propagation rates and enhanced susceptibility to stress-corrosion cracking.
Weight Functions for Three-Dimensional Symmetrical Crack Problems
Authors: Labbens RC , Heliot J , Pellissier-Tanon A
Published: March 2009

The knowledge of weight functions would be of great help for the solution of three-dimensional crack problems. A numerical method of computation of these functions by finite elements is developed, starting from the simple consideration of concentrated forces applied to the crack and the energy released by local extensions of the crack.

Particular attention is paid to the consideration of the asymptotic value of the weight functions at the crack tip, which allows the definition of dimensionless weight functions and makes the numerical calculation easier.

Special weight functions are considered for the case when the applied stress depends on one coordinate only.

The method is checked by comparing the computed weight function for a penny-shaped crack in an infinite solid with the known closed form solution. It seems that the accuracy obtained could allow for solution of engineering problems; however this should be checked by other tests especially in the region of the singularity.

The computing time, however, is long because of the large number of nodes needed in three-dimensional bodies, and the calculation is costly. It seems advisable to investigate the possibilities of other methods of solution of elasticity problems, such as the method of boundary integral equations, for changing the order of magnitude of the computing time and the cost of the calculation.
Evaluation of a Proposed Standard Method of Testing for Susceptibility to Stress-Corrosion Cracking of High-Strength 7XXX Series Aluminum Alloy Products
Authors: Sprowls DO , Summerson TJ , Ugiansky GM , Epstein SG , Craig HL
Published: March 2009

A task group sponsored jointly by The Aluminum Association and the ASTM has recommended a standard method of test for susceptibility to stress-corrosion cracking (SCC) of 7XXX aluminum alloy products (ASTM G 47-76). The proposed standard is a comprehensive method that specifies the corrosive environment and period of exposure, type of test specimen and method of loading, procedures for sampling various manufactured product forms, and guidelines for interpretation of test results. Final selection of test procedures was based on round robin tests performed in nine different laboratories and 3-year exposures to the atmosphere in both seacoast and inland industrial locations. A summary of test results is given to illustrate how the relative performance of three different tempers of 7075 alloy plate can be influenced by the choice of a test specimen, differences in the outdoor atmosphere, and interlaboratory variations in performing the standard 3.5 percent sodium chloride alternate immersion test.
Air Pollution Effects on Stress Induced Intergranular Corrosion of 7005-T53 Aluminum Alloy
Authors: Haynie FH
Published: March 2009

Through a statistically designed, controlled environment experiment, it was found that atmospheric levels of sulfur dioxide induce a type of stress-accelerated intergranular corrosion in 7005-T53 aluminum alloy extruded tube material. Varying levels of nitrogen dioxide, ozone, relative humidity, and their interactions (including those with sulfur dioxide) did not cause statistically significant damage in this particular experiment. Some level of stress was necessary to cause this type of attack.
Evaluating Stress-Corrosion Crack-Propagation Rates in High-Strength Aluminum Alloys with Bolt Loaded Precracked Double-Cantilever-Beam Specimens
Authors: Sprowls DO , Coursen JW , Walsh JD
Published: March 2009

Propagation rates for stress-corrosion cracking (SCC) of high-strength aluminum alloys determined with mechanically precracked double-cantilever-beam (DCB) specimens provide a quantitative means of comparing the resistance to SCC of alloys and tempers. For relatively resistant materials however, the rates can be markedly influenced by test conditions and interpretation of the crack-growth data. This paper describes a relatively simple, accelerated testing method for determining SCC velocities that rank the SCC behavior of aluminum alloys in the same order as SCC propagation rates in a seacoast or industrial atmosphere. Practical difficulties associated with this test method, however, warrant further evaluation to justify this as a primary method of testing.
Aqueous Stress-Corrosion Cracking of High-Toughness D6AC Steel
Authors: Gilbreath WP , Adamson MJ
Published: March 2009

The crack growth behavior of D6AC steel as a function of stress intensity, stress and corrosion history, and test technique, under sustained load in filtered natural seawater, 3.3 percent sodium chloride solution, and distilled water, was investigated. Reported investigations of D6AC were considered in terms of the present study with emphasis on thermal treatment, specimen configuration, fracture toughness, crack-growth rates, initiation period, and threshold. Both threshold and growth kinetics were found to be relatively insensitive to these test parameters. The apparent incubation period was dependent on technique, both detection sensitivity and precracking stress intensity level.
Stress-Corrosion Cracking Properties of 17-4 PH Steel
Authors: Fujii CT
Published: March 2009

Recent unexpected occurrences of stress-corrosion cracking (SCC) with 17-4 PH structural components indicated a need for improved characterization of the alloy and application of more advanced analytical procedures for reliably predicting structural performance. Accordingly, the purpose of the present studies was to establish systematically the SCC properties of 17-4 PH steel over a wide range of yield strengths and applied cathodic potentials. Six different heat treatments were selected for the SCC studies. The data, when analyzed in terms of ratio analysis procedures, are immediately useful for predictions of service reliability of the steel in marine structures.

The results show that 17-4 PH steel is moderately sensitive to SCC at high-strength levels, less sensitive to SCC at intermediate strength levels, and relatively insensitive to SCC in the metallurgically overaged, low yield strength condition. Increased applied cathodic potentials increase the SCC susceptibility of the alloy significantly which strongly suggests the involvement of hydrogen in the SCC mechanism. The minimum specimen thickness required for determining a thickness-independent KIscc for steels by the cantilever method appears to be considerably less than for a standard KIc test.
Corrosion Fatigue and Stress-Corrosion Cracking of High-Hardness Laminar Composite Steel
Authors: Chait R , Campbell MD
Published: March 2009

In this study both corrosion fatigue and stress-corrosion cracking behavior of a high-hardness laminar composite steel are examined in the presence of a 3.5 percent sodium chloride (NaCl) environment and compared to the behavior in air. It is shown that the susceptibility is not limited to specimens with a crack or notch. Smooth specimens with a machine ground surface tested under static as well as cyclic loading are affected adversely by the 3.5 percent NaCl environment. Using center notched panels to study crack growth behavior, it is shown that the influence of the 3.5 percent environment becomes more apparent as the maximum cyclic stress decreases. Ballistically damaged panels were also examined in a corrosive environment under the same cyclic stress conditions. Compared to the center notched panels a longer life is observed. It is suggested that this is due to the orientation of the ballistically induced cracks with respect to the loading axis. Environmental effects are also seen in the static loading of ballistically damaged panels. KIscc estimates were obtained from these panels and compared to the results of conventional specimens. Both sets of results indicate significant susceptibility of the laminar composite steel to stress corrosion.
Crevice Corrosion and Its Relation to Stress-Corrosion Cracking
Authors: Chen CM , Froning MH , Verink ED
Published: March 2009

Crevice corrosion of high-strength low-alloy D6AC and Type 316 stainless steel was surveyed using artificial crevice assemblies. A critical potential, referred to as the “crevice protection potential” was found, above which crevice corrosion occurs and below which it does not. The corrosion condition in the crevice is related importantly to the mechanism of cracking, that is, stress-corrosion cracking or hydrogen embrittlement.
Analysis of Radially Cracked Ring Segments Subject to Forces and Couples
Authors: Gross B , Srawley JE
Published: March 2009

Results of planar boundary collocation analysis are given for ring segment (C-shaped) specimens with radial cracks, subjected to combined forces and couples. Mode I stress intensity factors and crack mouth opening displacements were determined for ratios of outer to inner radius in the range 1.1 to 2.5 and ratios of crack length to segment width in the range 0.1 to 0.8.
Estimation of KIc from Slow Bend Precracked Charpy Specimen Strength Ratios
Authors: Succop G , Brown WF
Published: March 2009

The Committee on Rapid Inexpensive Tests for Determining Fracture Toughness of the National Materials Advisory Board recently recommended that action be taken by the American Society for Testing and Materials to standardize the slow bend precracked Charpy test for the purpose of providing an index of plane-strain fracture toughness based on the nominal strength of the Charpy specimen. This paper reports results of an investigation to explore the possibility of using nominal strength values for this purpose. Precracked Charpy specimens were cut from plate stock having well established KIc values. The alloys investigated were 4340 steel, 18Ni maraging steel, several high-strength aluminums, and a titanium alloy. For each alloy a range of toughness levels were tested. Nominal strength values from the Charpy specimens were calculated from their maximum loads, and the ratio between these strength values and the tensile ultimate strength σut was correlated with KIc2/σut2.

The results show that the range of plane-strain toughness over which a useful relation between Charpy strength ratios and KIc can be established is limited by excessive plasticity in the Charpy specimens at high-toughness levels. The effect of this plasticity is to cause a gradual loss of sensitivity of the Charpy strength to changes in KIc. The Green and Hundy limit developed for a nonstrain hardening rigid plastic material is useful in estimating the sensitivity limits. If the toughness range is suitably restricted to avoid this loss of sensitivity, it appears that the Charpy strength ratio is a useful index of KIc and can be used to estimate KIc with confidence equal to that as obtained by using W¯/A values derived from the same specimens.
Fracture Testing with Surface Crack Specimens
Authors: Orange TW
Published: March 2009

This paper is a report of ASTM Task Group E24.01.05 on Part-Through Crack Testing. It includes recommendations for the design, preparation, and static fracture testing of surface crack specimens based on the current state of the art. The recommendations are preceded by background information including discussions of stress intensity factors, crack opening displacements, and fracture toughness values associated with surface crack specimens. Cyclic-load and sustained-load tests are discussed briefly. Recommendations for further research are included.
Effects of Flowing Natural Seawater and Electrochemical Potential on Fatigue-Crack Growth in Several High-Strength Marine Alloys
Authors: Crooker TW , Bogar FD , Cares WR
Published: March 2009

Fatigue crack propagation studies were conducted on specimens of four high-strength marine alloys to determine the sensitivity of fatigue-crack growth rates to seawater and electrochemical potential. The materials studied included HY-130 steel, 17-4 PH steel in several combinations of melt processing and temper, Ti-6A1-2Cb-1Ta-0.8Mo, and 5456-H116 aluminum. Fatigue testing was conducted at low cyclic frequency, and the fatigue data are presented in terms of fatigue-crack growth rate (da/dN) versus crack-tip stress-intensity factor range (ΔK). Specimens were exposed to fresh flowing natural seawater under freely corroding and potentiostat-controlled electrochemical conditions while undergoing corrosion-fatigue testing. The results of this investigation reveal significantly distinct differences among the four alloys under the conditions of corrosion fatigue. Both seawater and potential acted to accelerate crack growth rates in the ferrous alloys, which proved to be much more sensitive to seawater and negative potential than the nonferrous alloys studied. The titanium alloy exhibited no measurable sensitivity to either seawater or negative potential. The aluminum alloy exhibited only moderate sensitivity to seawater and beneficial effects from both positive and negative potentials. These exploratory studies indicate that high-strength marine alloys exhibit widely differing responses to corrosion-fatigue crack growth and that high-strength steels currently aimed for marine service are among the alloys most deleteriously affected.
Supplement to the Bibliography and Abstracts on Thermostat Metals
Authors: Committee B-4
Published: March 2009

Description

This is the third supplement to the Bibliography and Abstracts on Thermostat Metals 1806;—1959, Special Technical Publication No. 288, published by the American Society for Testing and Materials. The first supplement, STP No. 288-A, contained additional references for the years covered by STP No. 288 and references for the years 1960 – 1961. The second supplement, STP No. 288-B, contained additional references for the years covered by STP No. 288 and STP No. 288-A and references for the years 1962;—1965. This supplement, STP No. 288-C, contains additional references for the years covered by STP No. 288, STP No. 288-A and STP No. 288-B and references for the years 1966 – 1973.
Fatigue Crack Growth and Fracture Toughness of 5083-0 Aluminum Alloy
Authors: Argy G , Paris PC , Shaw F
Published: March 2009

Certain material properties of 5083-0 aluminum alloy which would be of interest to designers of liquefied natural gas (LNG) tankage are presented and discussed. Fatigue crack growth rates obtained both from specimens containing a semielliptical surface flaw and from compact tension specimens are given and compared to other published data. Values of Kc for 2-in.-thick plate obtained from center-cracked specimens at room temperature and from compact tension specimens at both room temperature and -260°F and static and dynamic loading are presented. For the latter specimens, R-curves used in the determination of Kc values are also given. Finally, KIc values are estimated using the J-integral technique.

The application of these data to the design of LNG tankage is discussed, paying particular attention to conditions required to assure “leak before failure” behavior.
Studies on Nine Percent Nickel Steel for Liquefied Natural Gas Carriers
Authors: Sakai T , Takashima H , Tanaka K , Matsumae H , Yajima H
Published: March 2009

The spherical tanks for the Moss-Rosenberg type of liquefied natural gas (LNG) carriers are to be fabricated from rolled and forged nine percent nickel (9Ni) steels, with the former steel being used as tank shell-plate material and the latter as tank equator-ring material. Accordingly, the authors carried out a series of experimental studies to evaluate the fatigue strength, resistance to fatigue crack propagation, fracture toughness, etc., of these tank steels having due regards to the “leak-before-failure” premise of the Moss-Rosenberg LNG containment system.

Various forms of plain and welded test specimens were prepared from actual shell-plate and equator-ring materials for fatigue tests; and, the effects of stress ratio and surface finish of reinforcement weld on the tank-steel fatigue strength were closely studied.

Wide-plate test specimens were fatigue tested under repeated tensile and bending loads, and configurations of through cracks immediately after penetration and crack propagation rates were examined.

Notched plain and welded wide-plate test specimens of different thicknesses were prepared from tank steel plates produced from different heats and submitted for tension tests to determine the critical stress intensity factor (Kc value) at the cryogenic temperature of LNG.

Using data obtained on material properties of the rolled and forged 9Ni steels, the authors evaluated the structural safety of the spherical LNG tank and confirmed that the 9Ni steel LNG tank completely satisfied the leak-before-failure criterion.
Fatigue Crack Growth Rate Studies of Partial Thickness Cracks in ASTM Method A 645-74, Five Percent Nickel Steel
Authors: McCabe DE , Sarno DA , Feddersen CE
Published: March 2009

Importation of liquefied natural gas (LNG) by ocean-going tankers is one short-term solution to the energy crisis. One of the promising candidate materials for the LNG tankage on these vessels is a specially heat treated 5 percent nickel alloy steel according to ASTM Specification for Pressure Vessel Plates, Five Percent Nickel Alloy Steel, Specially Heat Treated (A 645-74). Fatigue data were developed to determine the growth rates of partial-thickness cracks (PTC) as a function of temperature, stress ratio, and fundamental parameters pertinent to spectrum loading. Constant amplitude PTC growth rate was reduced as the test temperature was lowered, accelerated as the stress ratio was increased, and shown to be approximately equivalent to through-thickness crack growth rates available in the literature. Results of variable amplitude tests showed a significant crack growth retardation effect. These data plus a typical ship spectrum loading histogram were programmed into a computer to make in-service fatigue life predictions. The performance of this computer program was checked against an actual spectrum loaded specimen.
Cryogenic Toughness Through Microstructure Control in an Iron-Nickel-Titanium Alloy
Authors: Jin S , Whitaker B , Morris JW , Zackay VF
Published: March 2009

This paper discusses the selection of composition and processing of an iron-nickel-titanium (Fe-Ni-Ti) alloy having a favorable combination of strength and toughness at cryogenic temperatures. Criteria on alloy composition lead to the choice of low interstitial Fe-12Ni-0.25Ti. The alloy has a naturally favorable microstructure, but cryogenic toughness must be imparted through grain refinement. Several alternate procedures are identified; four of these are discussed in detail, along with the resulting tensile properties at 77 K, Charpy impact energies at 77 and 5 K, and behavior in fracture toughness tests at 77 K. Alloys are obtained having yield strengths to 150 ksi with excellent impact toughness to 5K.
Cryogenic Properties of Iron-Manganese and Iron-Manganese-Chromium Alloys
Authors: Schanfein MJ , Yokota MJ , Zackay VF , Parker ER , Morris JW
Published: March 2009

A wide range of microstructures were obtained in iron-manganese alloys by varying the manganese and chromium contents. When a body centered cubic α structure was produced, increasing amounts of manganese were found to be detrimental to low temperature toughness. At manganese levels greater than 12 percent where appreciable amounts of ε and γ phases formed, the ductile-brittle transition temperature dropped rapidly. In terms of the ϵ + γ phases present, the ductile-brittle transition temperature decreased at a rate of 1.3°C/volume percent ε + γ. Increasing the ε + γ content to achieve good low temperature toughness, however, also caused a decrease in the yield strength. Increases in the yield strength were achieved without appreciable increase in the ductile-brittle transition temperature by greater manganese and chromium additions.
Strain-Cycling Fatigue Behavior of Ten Structural Metals Tested in Liquid Helium, Liquid Nitrogen, and Ambient Air
Authors: Nachtigall AJ
Published: March 2009

The strain-cycling fatigue behavior of 10 different structural alloys and metals (two aluminum alloys, two titanium alloys, two stainless steels, a maraging steel, a high-nickel alloy, pure nickel, and pure copper) was investigated in liquid helium, liquid nitrogen, and ambient air at room temperature. Cylindrical hourglass-shaped specimens were loaded in compression and tension about zero mean strain to produce the desired strain ranges. Tensile properties were also obtained for each material and environmental temperature so that they could be used with the Manson-Hirschberg method of universal slopes to predict the fatigue behavior at each temperature.

At high cyclic fatigue lives, fatigue resistance increased with decreasing temperature for all the materials investigated. At low cyclic fatigue lives, fatigue resistance generally decreased with decreasing temperature for the materials investigated. Only for Inconel 718 did the fatigue resistance increase with decreasing temperature over the entire life range investigated. Comparison of experimental fatigue behavior with that predicted by the Manson-Hirschberg method of universal slopes showed that the strain-cycling fatigue behavior of these materials at cryogenic temperatures can be predicted with an accuracy comparable to that achieved in earlier investigations conducted at room temperature. Of the fatigue data obtained at cryogenic temperatures 80 percent were predicted within a life factor of 3.
Low Temperature Elastic Properties of Aluminum 5083-0 and Four Ferritic Nickel Steels
Authors: Weston WF , Naimon ER , Ledbetter HM
Published: March 2009

The low-temperature elastic properties have been determined for five commercial alloys that have possible structural applications at cryogenic temperatures. The alloys are 5083-0 aluminum and four ferritic steels: 3.5, 5, 6, and 9 percent nickel. An ultrasonic (10 MHz) pulse-superposition method was used to measure longitudinal and transverse wave velocities. Using the velocities and the mass density as input, the following elastic constants were calculated: longitudinal modulus, Young's (tensile) modulus, shear (rigidity) modulus, bulk modulus (reciprocal compressibility), and Poisson's ratio. Measurements were made semicontinuously from 300 to 4K. The room-temperature composition dependence of iron-nickel alloys is reviewed comprehensively up to 12 percent nickel. Debye temperatures were calculated from the elastic constants. A discussion is given of the temperature dependences of the elastic constants and differential relationships among the elastic constants.
Monitoring of Two Braced Excavations in Chicago
Authors: Cunningham JA , Carpenter LD
Published: March 2009

The Sears Tower and Harris Bank projects, both in Chicago, involved deep basement excavation in soft clays. The Sears Tower project encompasses an area of approximately 300 by 400 ft. A concrete slurry wall forms the sides of the excavation which extends to a depth of approximately 35 to 45 ft below the adjacent street level. The Harris Bank project covers an area approximately 180 by 135 ft abutting the existing bank building. Excavation for the new building was about 45 ft deep in a 135 by 90 ft area in the southeast corner, and 30 ft deep in the remaining area. Soldier piles and lagging were used to form the sides of the excavation. The soil retention system for both projects used three levels of bracing. Corner braces and rakers extending to the interior sections of the base mat were used on the Sears Tower project. Corner braces and cross-lot struts were used at the Harris Bank project. This paper describes the apparatus and procedures used for obtaining strain data on the bracing members, and compares the measured forces with design forces in the bracing.
Measurement of Strut Loads by Means of Vibrating-Wire Strain Gages
Authors: O'Rourke TD , Cording EJ
Published: March 2009

The performance of three models of vibrating-wire strain gages is judged in light of laboratory investigation and field experience. Gage models include the Telemac SC-11, Telemac SC-8, and Geonor acoustical gages. Measurement accuracy is controlled by gage sensitivity to changes in strain, zero drift of the gage readings, and thermal response. The Telemac SC-8 and Geonor gages show temperature dependencies of 2.5 microstrain/10°F (4.5 microstrain/10 K) and 1.5 microstrain/10°F (2.7 microstrain/10 K), respectively. Both of these gage models show little or no zero drift with time. The Telemac SC-11 gage shows a temperature dependency of 4.6 microstrain/10°F (8.3 microstrain/10 K) and exhibits a zero drift as high as 40 microstrain over a period of 50 days. For cross-sectional areas equal to or less than 50 in.2 (323 cm2), the Telemac SC-11 gage shows instrument error less than 10 percent of the strut load, provided that the gage reading has been corrected for temperature and zero drift. For similar conditions, the Telemac SC-8 and Geonor gages show an instrument error of approximately 5 percent of the strut load. The design of strut load instrumentation is detailed under five headings which provide recommendations concerning choice of gages, installation, positioning, remote observations, and supplemental measurement techniques. Strut load measurements from a 60-ft (18.2-m) deep braced cut are analyzed with respect to the special characteristics of the Telemac SC-11 gages. The magnitude and distribution of brace loads in response to the removal of bottom struts from the excavation are summarized.
Performance of Tied-Back Excavation at Water Tower Place
Authors: Gnaedinger JP , Gill SA , Keim PA
Published: March 2009

The earth retention system used for the construction of a four-level underground garage at the Water Tower Place project, located in Chicago, Ill., is described. The excavation covered an area of 530 by 212 ft and extended to a depth of 44 ft below ground surface. It was supported by a cast-in-place reinforced concrete wall, 30 in. thick, 62 ft deep, installed by the slurry trench method. The wall spanned between the shafts of perimeter foundation caissons spaced 30 to 31 ft on centers, bearing on “hardpan” at a depth of 88 ft. The shafts were designed to carry part of the lateral load and were encased in a steel shell ⅝ in. thick to a depth of 72 ft. The slurry wall was supported at two levels: by a row of grouted earth anchors at the upper level 11 ft from the top, and by inclined rakers at the lower level 27 ft from the top.

Performance of the earth retention system was monitored by load cells on tiebacks, strain points on rakers, inclinometers, and by surface measurements. The load carried by each tieback at the completion of substructure was measured by a hydraulic jack. Measured loads are compared with those predicted by the commonly used earth pressure theories. Terzaghi and Peck's pressure diagram appears to fit the observed data. Lateral displacements were generally comparable to those recorded elsewhere for excavations supported by concrete walls and tiebacks. Vertical displacements contiguous to the cut were much less than the predictions based on settlement data reported by Peck for basement excavation in the downtown Chicago area.
Excavation and Soldier Pile-Tremie Concrete (SPTC) Wall Instrumentation and Monitoring Program
Authors: Brown RE
Published: March 2009

The rationale and objectives of an instrumentation and construction monitoring program for a 30 to 50-ft-deep excavation are presented. The excavation was supported by a soldier pile-tremie concrete (SPTC) wall with auger-cast, soil-supported tiebacks. The instrumentation included slope indicators, dial gages, and load cells. The monitoring program included surveying horizontal and vertical movements, monitoring cracks and water levels, and reading the instrumentation. The accuracy of the readings are evaluated. It is concluded that backup systems and methods to cross-check data are required for a successful program. In addition, it is suggested that field calibration checks on the instrumentation be employed.
Modified Mat Foundation Design Over Soft Clay
Authors: Baker CN , Wiesinger FP
Published: March 2009

The case history of how design and construction were interdependent on a project involving a 26-story apartment building over Chicago soft clay is described. A modified mat foundation solution was selected as the most economical and feasible type of foundation for the structure. Due to the high stress levels induced in the soft clay layer from the building weight, an instrumentation program consisting of settlement readings, pore pressure measurements, and inclinometer readings was necessary to monitor performance of the structure and soil during construction. A reasonable factor of safety required that significant pore pressure dissipation and shear strength increase occur in the soft clay layer during construction of the project. The results obtained verified the design approach.
Instrumentation of Large Buried Culverts
Authors: Selig ET
Published: March 2009

The need for information on the performance of large buried culverts has resulted in implementation of three field-instrumentation programs. Soil stress, strain, and deformation sensors were developed for these studies using the induction coil system. The projects are described and the results are illustrated. This experience is used as a basis for assessing the capabilities of the instrumentation.
Use of Fractography and Sectioning Techniques to Study Fracture Mechanisms
Authors: Van Stone RH , Cox TB
Published: March 2009

Recent investigations of the effect of microstructure on the fracture mechanisms and fracture toughness of steels, aluminum alloys, and titanium alloys have used standard fractographic techniques and a sectioning technique on specimens plastically deformed to various strains up to fracture. The specimens are prepared metallographically for observation in both optical and electron beam instruments. This permits observations to be made about the fracture mechanism as it occurs in thick sections and helps remove speculation from the interpretation of fractographic features. This technique may be used in conjunction with other standard techniques such as extraction replicas and microprobe analyses. Care must be taken to make sure that the microstructural features which are observed to play a role in the fracture process using the sectioning technique can be identified with fractography.
Environmentally Induced Transitions in Fatigue Fracture Mode
Authors: Morris WL , Frandsen JD , Marcus HL
Published: March 2009

The introduction of various gaseous species into the test environment can have significant effects on fatigue crack propagation. This is usually noted as an increase in crack propagation rate in the aggressive environment compared to the baseline data. In this investigation fatigue crack propagation has been conducted in low pressure gaseous environments such as hydrogen and oxygen and a vacuum of 1 × 10−8 torr as reference for several iron and nickel base alloys and a titanium alloy. Other variables investigated include stress intensity level and temperature. Scanning electron fractography and replica fractography have been used to characterize the resulting failure mode. Fracture morphology varies from ductile transgranular fracture in vacuum for all materials to brittle integranular fracture for some of the nickel base alloys in hydrogen gas. Transitions in failure mode caused by oxygen gas and less severe cases of hydrogen embrittlement are more subtle. In some cases the transition in failure mode can be correlated with indications of changes in deformation mode. It is proposed that this transition in deformation mode is the result of an interaction between the adsorbed gas atoms and mobile dislocations within the plastically deforming region at the crack tip.
Fractography as Related to Macrostructures in Stress Corrosion Cracked Welds in 5Ni-Cr-Mo Steel
Authors: Metzbower EA , Fujii CT , Stoop J
Published: March 2009

Correlations were found between the fractography of stress corrosion cracked surfaces and the macrostructure of shielded metal arc weldments of a 5Ni-Cr-Mo steel. The fractography of the stress corrosion regions revealed fracture modes consisting of cleavage, microvoid coalescence, and intergranular separation. Cleavage was often associated with a coarse irregular fracture, whereas with microvoid coalescence the fractures were generally flat. Fractures of intergranular separation were characterized by dot-like facets on the macrographs. The macrostructures corresponding to intergranular separation consisted largely of coarse equiaxed grains and to a lesser extent of columnar grains. The latter quite often were too large to be completely revealed by transmission electron microscope fractography and in some instances were more favorably oriented for transgranular failure by cleavage than for intergranular failure.
Fractography of the High Temperature Hydrogen Attack of a Medium Carbon Steel
Authors: Nelson HG , Moorhead RD
Published: March 2009

A systematic study was made of the microscopic fracture processes associated with hydrogen attack of a medium carbon steel in a well-controlled, high-temperature, high-purity hydrogen environment. Exposure to a hydrogen pressure and temperature of 3.5 MN/m2 and 575°C was found to progressively degrade room temperature tensile properties with increasing exposure time. After 408 h, the maximum exposure time of this study, yield and ultimate strengths were reduced by more than 40 percent and elongation was reduced to less than 2 percent. Initial fissure formation was found to be associated with managnese rich particles, mostly probably manganese oxide, aligned in the microstructure during the rolling operation. Fissure growth was found to be associated with a reduction in carbide content of the microstructure and was inhibited by the depletion of carbon. The interior surfaces of sectioned fissures or bubbles exhibit both primary and secondary cracking by intergranular separation. The grain surfaces were not smooth and flat but instead were rough and rounded, suggesting a diffusion-associated separation process. Finally, specimens that were failed at room temperature after exposure to hydrogen were found to exhibit mixed mode fracture having varying amounts of intergranular separation, dimple formation, and cleavage, depending on exposure time.
Relationship Between Mechanical Properties, Microstructure, and Fracture Topography in α + β Titanium Alloys
Authors: Chesnutt JC , Rhodes CG , Williams JC
Published: March 2009

The influence of forging schedule and subsequent heat treatment on the microstructure and mechanical properties of three α + β titanium alloys has been investigated. The alloys studied were Ti-6Al-4V, Ti-6Al-6V-2Sn, and Ti-6Al-2Sn-4Zr-6Mo. The microstructural comparisons included (α + β) finished and β-processed material, variations in primary α volume fraction, primary α particle aspect ratio, and the nature of the β-transformation products. Careful selection of forging history and heat treatment permitted comparisons of fracture properties at essentially constant strength levels. This paper describes the influence of forging and heat treatment on the microstructure of these alloys as shown by light and thin foil electron microscopy. The microstructural information was then used to analyze the variations in topography of both fatigue and fast fracture regions as observed by scanning electron microscopy. In some cases, good correlation between fracture topography and microstructure has been established but such correlations depend on microstructure and on loading conditions. For example, fast fracture in the β-processed materials occurs largely along prior β-phase grain boundaries, whereas fatigue cracks propagate by a predominantly transgranular mode. Further, the occurrence of fatigue straiations strongly depends on microstructure and on the cyclic stress intensity, with cyclic cleavage predominating at low growth rates in those alloy conditions containing primary α particles which have at least one dimension greater than ∼25 µm. Other correlations between fracture topography, microstructure, and properties were obtained and comments for microstructure selection to control properties are included.
Fractography: Fracture Energy and Quantitative Metallographic Correlation for Tungsten-Silver Composite Materials
Authors: Warke WR , Witter GJ
Published: March 2009

Tungsten-silver materials were made by two different powder metallurgical techniques which resulted in alloys having a wide latitude of structural variation in terms of volume fraction, particle size, and distribution. A correlation of GIc, the critical strain energy release rate, was made with the quantitative metallographic parameters ¯L3Ag, the mean intercept length within the silver phase; C, the contiguity of the tungsten phase; and VνAg, the volume fraction of the silver phase. A term composed of these three parameters was found to have a good correlation with GIc for all the alloys. A study of the fracture surfaces of each alloy by energy-dispersive X-ray analysis shows the silver content of the fracture surfaces decreases as the toughness of the alloys decreases.
Univariate Psychophysical Functions
Authors: Moskowitz HR
Published: March 2009

Psychophysical scaling is discussed in terms of two basic approaches: measurement of the errors of discrimination and the erection of a scale based upon variability of judgments (Weber-Fechner approach) and measurement of magnitudes by direct subjective judgments (category and ratio scaling approaches). Each approach yields its own unique psychophysical function relating physically measured magnitudes to subjective intensities. The more direct approaches of category and ratio scaling are preferred because of their simplicity of use and because experimental findings can be translated into applications with greater ease.
Overview of Applied Multivariate Analysis
Authors: Stungis GE
Published: March 2009

Multivariate methods are overviewed from a systemic approach. The techniques are briefly discussed and simple examples are used to acquaint the nonstatistician with the rudimentary concepts and vocabulary. Comments on other possible modeling schemes will be briefly discussed. Some of the computer programs which are currently available are referenced.
Formability Testing and Deformation Analysis of Steel Sheet
Authors: Newby JR
Published: March 2009

The success of production sheet metal stamping operations is determined by material properties, in conjunction with the forming process. The uniaxial tension test provides useful values to compare materials. These may relate to properties for improved biaxial stretchability and deep drawability as determined by simulative tests. Mathematical models derived from continuum mechanics and microplasticity theory may be used to explain simple deformation processes.

The failure of most production stampings results from local necking. For this reason, if the forming operation can be designed such that no thickness straining occurs, forming performance can be improved. An experiment demonstrating this was conducted.
Formability of Aluminum Alloys Using Cup Tests*Original experimental data were measured in U.S. customary units.
Authors: Gricus FV , Drittler OE
Published: March 2009

Cup height testing remains an important means of judging relative formability of aluminum alloys. This is true in both alloy development work and plant quality control. In this paper a comparison is given between Ball Punch Deformation Testing (Olsen cup) and a cupping test incorporating a 10.2-cm (4-in.)-diameter spherical punch. The merits and inadequacies of both tests in distinguishing differences in formability of aluminum alloys is discussed.
Predicting Sheet Anisotropy from the Fracture Angle of Tension Specimens
Authors: Lege DJ
Published: March 2009

Fracture angles and plastic strain ratios (r values) for aluminum alloys 2036-T4, 3004-H19, 5182-O, and 5352-H19 were determined and compared to the theoretical relationship between localized necking angle and r value. Data determined for 3004-H19 and 5352-H19 specimens, which exhibit minimal diffuse necking prior to localized necking, follow the theoretical relationship, while data determined for 2036-T4 and 5182-O specimens, which exhibit considerable diffuse necking, do not. Empirically determined fracture angle correction terms were developed for 2036-T4 and 5182-O to permit reasonable estimates of r based on the theoretical relationship.
Stress-Peen Straightening of Complex Machined Aircraft Parts
Authors: Skinner RD
Published: March 2009

The forming and straightening of complex aircraft parts usually requires development to overcome springback, and often requires elevated temperature to minimize scrappage and reduce detrimental stresses. Also, it is more of an art than a controlled process. A new forming concept has been developed which employs shot peening of the part while it is restrained to a predetermined, elastic tensile stress. The process, called stress-peen forming, demonstrates excellent predictability by balancing the stress profile across the cross section, applying standard, strength-of-materials equations. The process provides ideal compressive stresses on all surfaces.

This paper presents the development of the process from its initial theory to preliminary straightening tests. The work includes the development of a mathematical model which (a) determines the initial stress in a complex forged part when it has been restored to its straightened position, and (b) predicts the amount of elastic prestress and permits the determination of the selected peening process parameters to produce the required balance stress equilibrium across the section. Limited compressive stress profiles due to shot peening and preliminary straightening test data are also presented.
Dual Analysis of Longitudinal and Transverse Zirconium Tensile Stress-Strain Data
Authors: Garde AM , Reed-Hill RE
Published: March 2009

An analysis of zirconium tensile stress-strain data was made by the Crussard and Jaoul method and an analogous method based on the Swift equation ϵp = ϵpo + cσm. Data from transverse and longitudinal specimens from 4 to 813 K were considered. Also investigated were the effects of a small 77 K prestrain on the 300 K deformation behavior, and the effect of composition on the deformation at an intermediate temperature (≅575 K). The two analyses revealed the same basic deformation stages in all specimens. Transverse and longitudinal specimens exhibited, in general, a different pattern of stages. At elevated temperatures (above 550 to 600 K) pure zirconium tends to exhibit single-stage behavior. Specimens in which kinking or twinning are significant factors showed multi-stage behavior. The basic pure zirconium stress-strain curve is one in which the stress-strain curve slope decreases rapidly with increasing stress.