bluuebunny/crossref_metadata_2025 huggingface dataset:
Pilot Study of the Fracture Arrest Capabilities of A553B Steel
Authors: Hahn GT , Hoagland RG , Kanninen MF , Rosenfield AR
Published: March 2009

The arrest properties of A533B steel are derived from measurements of the crack velocity and crack length at arrest using: (a) 140 by 400-mm duplex double-cantilever-beam (DCB) specimens with hardened and welded-on AISI 4340 steel starter sections, (b) a wedge-loading procedure, and (c) the Timoshenko beam-on-a-generalized-foundation dynamic analysis. Propagation and arrest events were studied at temperatures from −18 to 33°C (nil ductility temperature + 61°C) and involved fractures propagating in the A533B at velocities up to 710 ms−1 and for distances up to 159 mm. The arrest capability of the steel is expressed in terms of the propagating crack fracture energy for the corresponding toughness, KD, and the velocity dependence of these quantities. The thickness, crack velocity, and temperature dependences of KD and its relation to KIc and KIa are examined. At −18°C, KD = 129 MNm−3|2, and Ka = 76 MNm−3|2. This method of evaluation promises to provide access to the full range of arrest properties of low and medium strength structural steels.
Predicting Fatigue Crack Retardation Under Single and Intermittent Overloading
Authors: Morman KN , Dubensky RG
Published: March 2009

An expression which simulates both retardation and delayed retardation in crack propagation subsequent to tensile overloading is presented and related to test data for Man Ten, Hadfield, and AISI 1020 steels, and Ti-8Al-1Mo-IV titanium alloy.

The crack growth expression is then generalized to predict the crack growth life in specimens for a variety of intermittent overload conditions. Agreement between the predicted and test data values for the four materials is within 20 percent for approximately one half of the more than 80 overload conditions studied.
Three-Dimensional Stress Distribution of a Double-Cantilever Beam with a Side Notch
Authors: Kirkwood WF , Prado ME
Published: March 2009

The effect of a side notch used as a crack guide in a double-cantilever-beam specimen is investigated. The resulting stress distribution along the section of symmetry ahead of the notch is obtained from a three-dimensional photoelastic model. The effect of the side notch through the thickness and down the side of the specimen is determined. After stress freezing, the model was sliced along principal planes. Along the x–x plane of symmetry, the principal stresses were determined by graphical integration of Filon's transformation of the Lamé-Maxwell equations and by subslicing along the x–z plane. Results of the investigation are in good agreement with those of other investigators. The side notch increases the value of the maximum tensile stress at the intersection of the starter notch and the side notch by approximately 22 percent.
Fracture Dynamics of Wedge-Loaded Double Cantilever Beam Specimen
Authors: Kobayashi AS , Mall S , Lee MH
Published: March 2009

Dynamic photoelasticity was used to analyze the Battelle-type wedge-loaded double cantilever beam (DCB) specimen machined from Homalite-100 sheets of 3/8-in. (9.5 mm) thickness. Dynamic stress intensity factors, dynamic energy release rate, crack velocities of straight and curved cracks were determined. Corresponding static stress intensity factors were calculated by the method of finite element analysis. These results were compared against Kanninen's analytical results and experimental results by Hahn et al using steel specimen. While dynamic photoelasticity results show qualitative agreement with Kanninen's results, the two differ in detail.
JIc Test Results From Two Steels
Authors: Underwood JH
Published: March 2009

Fracture toughness tests were performed with 10 by 20-mm, deeply notched bend specimens of a mild steel and a nickel-chromiummolybdenum steel. Using the recently proposed J-integral test method, critical values of the energy line integral for Mode I crack growth, JIc, were determined for the two materials. The JIc results were discussed in relation to various specimen geometry criteria and critical crack growth criteria which have been proposed for a standardized JIc test procedure. The JIc results from the nickelchromium-molybdenum steel are found to be in excellent agreement with the known KIc value when the elastic deflection corresponding to the uncracked specimen is taken into account.

The JIc results from both steels are shown to be closely approximated by a one-specimen JIc test procedure, which is described and suggested for use as a fracture toughness screening test.

An analysis is presented of the error which arises in JIc determination when the effect of uncracked deflection in bend specimens is ignored. The error can be significant for materials with large values of yield strength relative to fracture toughness, even for deeply cracked specimens.
Influence of Configuration on R-Curve Shape and Gc When Plane Stress Conditions Prevail
Authors: Adams NJ
Published: March 2009

Following a brief introduction, an examination is presented of the factors which define the fracture toughness, R-curve relationships, and the extent of stable crack extension. Use is made of the compliance calibrations for a center cracked sheet and a compact tension specimen to show how configuration influences the shape of the R-curve in specimens of equivalent width and identical thickness. The change in the shape of the R-curve is shown to affect stable crack extension and the G-curve tangency requirement to result in differing toughness levels in the different configurations.

In support of the analytical results, tests have been conducted on two high strength aluminium alloys to establish the variations in the shape of R-curves, using both compliance-indicated and measured absolute values of crack length. Various toughness values which highlight the influence of plastic deformation on toughness have been calculated.
The Weight Function Method for Determining Stress Intensity Factors
Authors: Paris PC , McMeeking RM , Tada H
Published: March 2009

An alternate method to those of Bueckner and Rice is presented for the derivation of the two-dimensional weight function for determining crack tip stress intensity factors. The weight function has r−1|2 type displacement singularity at the crack tip. It is shown that this singular field can be formulated using Westergaard stress functions in a manner similar to the method used for r1⊢2 type fields in crack tip displacements.

A straight-forward approach for obtaining weight functions for cracked finite bodies is presented. This technique can be combined in a simple fashion with the finite element method. As an example, a weight function for the SEN strip is obtained in this manner. Moreover, closed form infinite body weight functions are also developed and used to derive some well-known stress intensity factor formulas.
A Laser Interferometry Method for Experimental Stress Intensity Factor Calibration
Authors: Macha DE , Sharpe WN , Grandt AF
Published: March 2009

A laser interferometry crack tip opening displacement measurement technique has been developed and is described here. This interferometric displacement gage was used to measure displacements near the crack tip in flawed specimens. Measured displacements were then converted to stress intensity factor calibration curves by means of the linear elastic fracture mechanics displacement equations. Application of this procedure to compact and edge-cracked aluminum specimens resulted in experimental stress intensity factor calibrations that agreed well with theoretical predictions for these two geometries.
Criteria for Growth of the Angled Crack
Authors: Swedlow JL
Published: March 2009

Mixed mode fracture in two dimensions has been of recent interest via study of a crack at an arbitrary angle to the axis of applied load. Three criteria for growth under tensile loads are reviewed and, although they proceed on distinct bases, give similar results. A corollary to a minimum energy hypothesis is inferred. A compression model is suggested and examined in terms of two criteria. Comparisons to data, to the extent they are available, are considered; observations on the nature of the data are followed by suggestions for further research.
Crack Tip Strain—A Comparison of Finite Element Method Calculations and Moiré Measurements
Authors: Hu W-L , Liu HW
Published: March 2009

The moiré crack tip strain measurements made on double-edge-notched specimens loaded into the region of general yielding are compared with the finite element method (FEM) calculations. If the ratio of specimen thickness and the total net cross-sectional width, (W-2a)/t, is equal to or more than ten, the bulk of the strain measurements agree well with the results of the plane stress calculations except in the small area close to the crack tip. The crack tip region is stiffened by the triaxial state of stress, and the deformation within the stiffened zone is less than that calculated for the plane stress model. The region affected by the crack tip stiffening extends to a distance from the crack tip equal to specimen thickness. This crack tip stiffened zone is imbedded in the characteristic plane stress zone if (W-2a)/t is larger or equal to ten.
Side-Cracked Plates Subject to Combined Direct and Bending Forces
Authors: Srawley JE , Gross B
Published: March 2009

The opening mode stress intensity factor and the associated crack mouth displacement are comprehensively treated using planar boundary collocation results supplemented by end-point values from the literature. Data are expressed in terms of dimensionless coefficients of convenient form which are functions of two dimensionless parameters, the relative crack length, and a load combination parameter which uniquely characterizes all possible combinations of tension or compression with bending or counterbending. Accurate interpolation expressions are provided which cover the entire range of both parameters. Application is limited to specimens with ratios of effective half-height to width not less than unity.
An Evaluation of Rising Load KIscc Testing
Authors: Clark WG , Landes JD
Published: March 2009

This report presents a detailed evaluation of the rising load, accelerated KIscc testing procedure proposed by McIntyre and Priest. Conventional long hold-time “bolt loaded” KIscc tests were conducted with 160 and 180-ksi yield-strength Type 4340 steel exposed to seawater, hydrogen, and hydrogen sulfide gas environments, and the results of these tests compared with similar data generated under rising load conditions. The results show that rising load KIscc testing in hydrogen sulfide gas can be used as a valuable technique for rapidly screening structural alloys with regard to their susceptibility to environment induced cracking in hydrogen bearing environments. However, this testing procedure cannot always be used to develop a quantitative measure of KIscc. Specifically, it is shown that for steels below about 200 ksi in yield strength, the KIscc measured in hydrogen sulfide gas is not the same as that measured in other hydrogen bearing environments (hydrogen and seawater). In addition, it is shown that gas pressure and loading rate can have a significant effect on the apparent KIscc measured under rising load conditions.
Retardation of Crack Propagation for D6AC High-Strength, Low-Alloy Steel in Aqueous Media by Addition of Oxidizing Inhibitors
Authors: Parrish PA , Chen CM , Verink ED
Published: March 2009

High-strength, low-alloy, martensitic steels are known to be subject to hydrogen embrittlement. This was demonstrated by measurements of crack-tip pH and localized hydrogen content at the fracture surface, and also by observation of electrochemical behavior of simulated “crevices.” The effect of certain oxidizing inhibitors was used to elucidate the mechanisms of stress-corrosion cracking (SCC) and to retard crack growth.

Hydrazine additions reduced the crack growth rate by an order of magnitude for D6AC in aqueous solutions. A 2 percent addition of hyrazine to solutions either with or without chlorides increased KIscc from 12 (without inhibitor) to 25 ksi∓in. (with inhibitor). The critical flaw size varies as the square of KIscc, so doubling KIscc is the equivalent of increasing the size of a critical flaw fourfold, which in turn makes more likely its detection non-destructively. Localized hydrogen analyses at various locations on the fracture surface of a D6AC specimen pulled to failure after exposure in hydrazine-inhibited solution (with or without chlorides) showed no hydrogen enrichment of the fracture surface (as compared to the bulk specimen remote from the fracture), hence no hydrogen embrittlement.

While sodium dichromate additions also increased KIscc and reduced the crack-growth rate in chloride-free solutions, they were not effective in 0.1 N sodium chloride solutions.

Special electrochemical measurements (with and without chlorides) showed that in the presence of the hydrazine inhibitor, the electrode potential of D6AC at the tip of an advancing corrosion fatigue crack was above (more noble than) the potential of the equilibrium hydrogen electrode. By contrast, the electrode potential at the apex of an advancing corrosion fatigue crack in D6AC exposed in dichromate-inhibited, chloride-containing solution was below (more active than) the potential of the equilibrium hydrogen electrode. Thus dichromate additions did not prevent hydrogen entry into D6AC in chloride solutions.
Review of Recent Studies on the Mechanism of Stress-Corrosion Cracking in Austenitic Stainless Steels
Authors: Dean SW
Published: March 2009

A review of the work done to elucidate the mechanism of stress-corrosion cracking of austenitic stainless steels is presented. The major emphasis is placed on the cracking which occurs in chloride environments, although other environments are mentioned. This paper is intended to update earlier reviews and is concerned mainly with works published in the period 1960–1971.

The various studies on the effects of environmental and metallurgical factors on the kinetics of the cracking process are reviewed in detail. Variables such as temperature, chloride concentration, pH, stress, and metallurgical state are discussed. Also, the various studies on the electrochemistry of the system are reviewed.

The major theories on the mechanism of the cracking process are divided into two groups: The electrochemical theories postulate that the effect of tensile stress is to accelerate the localization of the corrosion process at crack sites. These theories include stress assisted segregation of damaging elements in the steel to the crack region, moving crystal imperfections including dislocations, and slip steps. The hydrogen entry theories, such as the formation of an easily corroded hydride phase or eta martensite formation, also fall into this category. The quasi-mechanical theories involve a mechanical fracture step in addition to corrosion. Tunnel pitting, corrosion produced wedging, and reduction of stress energy required to propagate a crack through chemical adsorption are examples of these theories. Finally, some areas of future work are discussed, and questions which need to be resolved are delineated.
Hydrogen Induced Delayed Failure of Type 310 Stainless Steel Foils
Authors: Kolts J
Published: March 2009

Hydrogen has been generally dismissed as playing a significant role in the mechanism of stress corrosion cracking of stable austenitic stainless steels because of the absence of brittle, delayed failures under cathodic charging conditions. In this investigation, 5-µm-thick foils of T310 (25Cr-20Ni) stainless steel have been embrittled with the application of cathodic potentials. Static delayed failures were observed in 1 N sulfuric acid (H2SO4) at ambient temperatures. Increased cathodic polarization resulted in decreased times to failure. The presence of 5-ppm arsenic greatly reduced the time to failure at a given applied potential. At a given current density, the time to failure for foils was considerably longer in solutions with pH 6 than in 1 N H2SO4.

Scanning electron microscopy of fracture surfaces from cathodically charged specimens demonstrated a severe loss in ductility. The fracture mode following hydrogen charging was planar and was distinctively different from the ductile mode of failure in the absence of hydrogen.

Classical hydrogen embrittlement of high-strength steels may be shown to be a reversible phenomenon by alternate hydrogen charging and degassing for many cycles. This results in a long total charging time with no concomitant permanent damage. In the present experiments, this was demonstrated for the T310 stainless steel by application of the proper potentials. The ductility of hydrogen charged specimens was recovered after baking at 400°F for 4 h.

The hydrogen content of foils was found to exceed 4000-ppm hydrogen after charging in arsenic poisoned acid solutions. Charging times, high-hydrogen content and embrittlement of the stainless steel foils were related.
Compliance Calibration of Specimens Used in the R-Curve Practice
Authors: McCabe DE , Sha GT
Published: March 2009

The compliance calibrations for the compact (CS) and crack-line-wedge-loaded (CLWL) specimens have been determined by experimental measurements and by boundary-collocation analysis. The CS and CLWL specimen configurations were modeled more accurately than those used in previous analytical investigations. Polynomial expressions for the compliance at various stations along the crack line for the CS and CLWL specimens are presented. The compliance calibrations for the center-crack tension (CCT) specimen have been determined theoretically by boundary-collocation and finite-element analysis. The calculated compliance values for the CCT specimen are compared with values obtained from the Irwin-Westergaard expression and from a modification to the Irwin-Westergaard expression proposed by Eftis and Liebowitz. The Eftis-Liebowitz expression was found to be in good agreement (± 2 percent) with both analyses for crack aspect ratios up to 0.8 and for gage half-span to specimen width ratios up to 0.5.
Corrosion Fatigue of Structural Steels in Seawater and for Offshore Applications
Authors: Jaske CE , Broek D , Slater JE , Anderson WE
Published: March 2009

The design of fixed platform structures for deeper water and more hostile environments places increased emphasis on the consideration of long-life (> 106 cycles) corrosion-fatigue behavior of low- and medium-strength structural steels in seawater. An interpretive review of available information on this technical area has been conducted, with separate consideration given to both fatigue-crack initiation and propagation. Emphasis is placed upon weldments because welded tubular joints are the areas of main concern in the fatigue evaluation of conventional offshore platform-type structures. Effects of strain range or range of stress intensity, stress ratio, cycling frequency, and type of loading spectrum are addressed. Also, environmental effects of oxygen level, temperature, pH, cathodic polarization, and high hydrostatic pressure are covered. The merits of cathodic protection in mitigating corrosion-fatigue damage are discussed in detail. Finally, results of this review are used to develop recommendations of the variables to be included in future experimental studies of long-life corrosion-fatigue resistance of such steels in seawater.
Small Randomly Distributed Cracks in Corrosion Fatigue
Authors: Kitagawa H , Fujita T , Miyazawa K
Published: March 2009

Very small distributed cracks often can be observed on the surfaces subjected to corrosion fatigue. In some cases, the fracture process can be characterized by the interaction and connection of these small distributed cracks. An analysis of such a corrosion-fatigue fracture process is presented by combining the techniques of fracture mechanics, reliability analysis, and graphical display. Many small cracks are measured and their statistical distribution functions, with respect to their sizes and locations, are determined. Using these functions as input data and a condition of the connections of cracks, a statistical simulation of a corrosion fatigue process is performed and its fracture process is output on a two-dimensional graphical display of an x-y plotter. The graphical display facilitates the simulation. The distribution of corrosion fatigue lives can be derived for some cases. Abrupt acceleration of the fracture process by the connection of distributed cracks is demonstrated.
Corrosion-Fatigue Behavior of 13Cr Stainless Steel in Sodium-Chloride Aqueous Solution and Steam Environment
Authors: Ebara R , Kai T , Inoue K
Published: March 2009

To clarify the influence of sodium-chloride (NaCl) content and steam environment on fatigue strength of 13Cr stainless steel, rotating-bending fatigue tests were conducted. Fatigue strength at 107 cycles in 3 percent NaCl aqueous solution was 70 percent lower than that in air. The lower the NaCl content, the longer the fatigue life is in the same stress level. The degree of the influence of steam on fatigue life decreases with decreasing the stress, and no influence was found in the fatigue limit. Corrosion pits and subcracks were found in all tested environments except air.

Corrosion pits were also observed at crack initiation region on fracture surface. Striation was predominant at fatigue life lower than 6 × 103 cycles in 3 to 3 x 10−3 percent NaCl and 2 x 104 cycles in steam environment.

At longer fatigue life, intercrystalline fracture pattern was predominant.
Influence of Advanced Ingot Thermal-Mechanical Treatments on the Microstructure and Stress Corrosion Properties of Aluminum Alloy Forgings
Authors: Zola J
Published: March 2009

A new approach, the application of microstructure control to products possessing an optimized alloy chemistry, has been taken to develop an improved combination of properties in 7000 series wrought aluminum products. The technique developed is an ingot (intermediate) thermal-mechanical treatment (ITMT) process which optimizes the combination of static strength, fracture toughness, fatigue strength, and stress corrosion resistance of commercial aluminum alloy die forgings. Previously, high fracture toughness had been achieved in wrought products by sacrificing tensile strength or stress corrosion properties. The ITMT processes produce either a recrystallized grain structure by thermal treatments prior to working at lower-than-conventional (warm) working temperatures or an altered grain structure by hot working the previously recrystallized structure. In both cases, the resulting grain morphology is desirable for good fracture toughness. Results of testing forging material show that ITMT on a high purity 7475 alloy produces advantageous fatigue crack propagation rates in 3.5 percent salt solution in comparison to 7075-T73, and stress corrosion resistance equivalent to 7075-T73 in addition to attractive tensile properties and high fracture toughness.
Corrosion Fatigue of 5456-H117 Aluminum Alloy in Saltwater
Authors: Chu HP , Macco JG
Published: March 2009

Fatigue behavior of 5456-H117 aluminum alloy has been studied by fracture mechanics and conventional test methods in air and saltwater environments. The results show that fatigue resistance of the alloy is reduced greatly by the presence of saltwater at low stress or stress intensity levels. Test data of smooth and precracked specimens are combined and discussed with regard to failure predictions.
Effect of Hydrogen Gas on High Strength Steels
Authors: Mukherjee B
Published: March 2009

A possible failure mode of high strength steels that are used in hydrogen gas-cooled turbine generators can be described by a combination of environment-assisted crack initiation, crack propagation by fatigue, and sustained load and final fracture. Therefore, a project was initiated to study the fracture properties in hydrogen and hydrogen sulfide (H2S) gas of two high strength steels, 3.5 nickel-chromium-molybdenum-vanadium ferritic and 18Mn-4Cr austenitic, which are commonly used for generator end rings. Two specimen types were employed, blunt notch specimens for crack initiation studies and precracked specimens for crack propagation and stress corrosion cracking studies. Tests were conducted to determine crack initiation due to incrementally rising load in H2S, crack propagation due to fatigue loading in hydrogen (H2), and KIscc in H2. This paper presents experimental data and provides metallurgical evidence to show that the failure mechanism in the specimens is environment assisted.
Materials and Liquefied Natural Gas
Authors: Weiss MJ
Published: March 2009

This is a general discussion of liquefied natural gas, sources of supply, costs of gas, and a description of the process most commonly used for base-load liquefied natural gas facilities.

The cryogenic heat exchanger and materials for pipe, fittings, valves, equipment, and hardware are discussed. Materials for liquid transfer lines, storage tanks, and flare systems, plant capacities, and facility costs are included.
Crack Growth and Fracture of Thick 5083-0 Plate Under Liquefied natural Gas Ship Spectrum Loading
Authors: Kelsey RA , Wygonik RH , Tenge P
Published: March 2009

Data are presented on the growth rate of surface flaws and through cracks in thick aluminum alloy 5083-0 plate for spherical liquefied natural gas (LNG) cargo tanks. Tests were made using 135-mm (5.3-in.) thick specimens loaded so as to simulate the bending and membrane stresses in the equatorial ring and 43-mm (1¾-in.) thick specimens loaded to simulate the membrane stresses in the bottom region of the tank. The investigation included: (a) determination of crack growth rate under ship spectrum loading; (b) measurement of leak rates through penetrated cracks; and, (c) fracture strength of the cracked specimens.

The tests demonstrated that there is a large margin of safety against the occurrence of leaks; but, if leaks should occur, the design requirement of “leak-before-failure” is satisfied. Even after penetration, the growth rate of through cracks is extremely slow. Finally, static failure of specimens containing cracks with lengths six times the thickness occurs by ductile tearing rather than by unstable crack growth.

Tests were also made to evaluate the tensile properties and the fracture toughness and fatigue crack growth characteristics of the plate and welds used for the large surface-flawed specimen. The plain and welded plate had exceptionally high toughness at room temperature, -162°C (-260°F), and -196°C (-320°F), as demonstrated by the fact that no rapid crack growth was observed in any of the 178-mm-thick notch bend fracture tests. There was no fracture instability in any of the tests, and all failures occurred by ductile tearing.
Toughness Variations Through the Thickness of Thick 5083-0 Aluminum Alloy Plate
Authors: Lake RL
Published: March 2009

Dynamic tear tests at the Naval Research Laboratory (NRL), using a series of beam specimens with increasing depth, have shown that the toughness of 3-in.-thick 5083 plate varied from surface to mid-plane. To explore the possible extent of such variation in still thicker plate and provide an economical test for assessing the effect of process variables on toughness, similar specimens were tested under static loading.

The data obtained could be interpreted with the aid of the plastic resistance concept used by NRL. We found that they would also yield approximate values of strain energy release rate at crack initiation (GIc), thus, linking the dynamic tear test and ratio analysis diagram directly to elastic-plastic fracture mechanics. The test method is much more economical than full plate thickness tests, and the results are believed to be more indicative of the materials' resistance to fracture than small specimen (invalid) KIc values, which are more indicative of material yield strength and the crack length dictated by specimen size, than they are of toughness.

Surface layers of one 5083-0 plate, 7.75 in. thick (195 mm), were found to be 20 to 30 percent tougher than center layers at room temperature. Toughness of the surface layers improved somewhat as the temperature was lowered to -260°F (-162°C). However, the improvement of the center layers was more dramatic. At the lower test temperature toughness was essentially uniform throughout the plate thickness.
Design Stresses for Aluminum Alloy 5083-0 and 5183 Welds at Cryogenic Temperatures
Authors: Bogardus KO , Malcolm RC
Published: March 2009

Data from more than 300 tension tests made at several laboratories on 5083-0 sheet and plate at cryogenic temperatures have been evaluated. Based on these data, minimum, allowable design stresses have been developed for temperatures as low as -320°F for inclusion in Section VIII, Division 1 of the American Society of Mechanical Engineers ASME Boiler and Pressure Vessel Code.
General Discussion on the Toughness of Nine Percent Nickel Steel
Authors: Omsén A
Published: March 2009

When discussing the properties and especially the toughness of 9 percent nickel (9Ni) steel, references are often made to the two different specifications for producing the steel: ASTM Specification for Pressure Vessel Plates, Alloy Steel, Nine Percent Nickel, Double-Normalized and Tempered (A 353-74); and, ASTM Specification for Pressure Vessel Plates, Alloy Steel, Quenched and Tempered 8 and 9 Percent Nickel (A 553-72).
Instrumentation of a 50-ft (15.2-m) Deep Braced Excavation
Authors: Bauer GE
Published: March 2009

An extensive instrumentation program was carried out over a 6-month period on a 50-ft (15.2-m) deep braced cut in dense sand. The temporary bracing system consisted of interlocking steel sheet piles (Larssen type IIIN), wales, and struts from wide-flange steel sections. The soil consisted of fine, uniformly graded sand with varying relative densities from medium to very dense. The loads of the struts on each side of the center bay for three strut levels were obtained by measuring the strains in the struts with a mechanical dial gage over an 8-in. (20.3-cm) gage length. The reliability and precision of these measurements are discussed.

The active and passive earth pressures were measured with 13 vibrating-wire, earth pressure transducers mounted flush on two adjacent piles at the center of the wall. The pressure cells were attached to the piles prior to driving and were subjected to severe conditions due to the extreme driving resistance of the piles. The calibration methods of these transducers prior to driving and on retrieval after completion of the construction are discussed in detail. The ruggedness and precision of the cells were evaluated.

The relatively large deformations of the cut were measured from lines of sight in the horizontal and vertical planes. In its final construction stage the wall had moved out more than 3 in. (7.6 cm) at the top and over 7 in. (17.8 cm) at the bottom of the sheet piles. The large inward movement of the bottom of the wall was mainly due to a hydraulic failure which significantly reduced the passive resistance of the soil inside the excavation.

Since the earth pressure cells measured total pressures only, it was necessary to measure the stresses due to water pressure to calculate the effective earth pressures. The water levels were obtained from borehole and open-standpipe observations. Each water pressure indicator consisted of plastic tubing with an open-end, screened fitting tapped through the sheet piles. The standpipes were installed during the excavation, and proved to be simple, inexpensive, and accurate.

The instrumentation program was considered successful despite many problems which were encountered mainly during the excavation period.
Comparison of Inclusion Distributions on Fracture Surfaces and in the Bulk of Carbon-Manganese Weldments
Authors: Passoja DE , Hill DC
Published: March 2009

Techniques are developed for determining the spatial and size distributions of spherical inclusions in mild steel. The relations between these distributions as found on electropolished surfaces and as found on fracture surfaces are determined. It is shown that the first neighbor spatial distributions on electropolished surfaces can be described analytically. The average dimple size on a fracture surface is always greater than the most probable first neighbor spacing. The inclusion size distributions both on electropolished and fracture surfaces are shown to be log-normal. The mean inclusion size on a fracture surface is always smaller than that on an electropolished surface. These variations are believed to arise from the nature of the fracture process.
Micro-Mechanistic Interpretation of Cyclic Crack Growth Behavior in 17-4 PH Stainless Steels
Authors: Crooker TW , Hasson DF , Yoder GR
Published: March 2009

A fracture mechanics and fractographic study has been made of cyclic crack growth in heat-treated samples of 17-4 PH stainless steel. Two 1/2-in. (1.27-cm) thick rolled plates were studied: a vacuum-melted (VM) sample in the H1050 condition and an argon-oxygen melted (AOM) sample in the H1050 and H1150 conditions. Crack-growth rates, da/dN, were obtained in ambient laboratory air as a function of stress-intensity factor range, ΔK, using single-edge-notched (SEN) tension specimens. Stress ratio, R, values of 0.04, 0.40, 0.67, and 0.80 were investigated. Microscopic modes of crack extension were determined by electron fractography and were utilized to explain differences in macroscopic crack-growth behavior. Cleavage and microvoid coalescence can appear as modes of cyclic crack propagation in this family of steels, to the detriment of cyclic crack-growth resistance. In particular, the following notable features were observed: (1) the amount of cleavage present appears to be independent of ΔK over a wide spectrum of ΔK levels; (2) the incidence of cleavage (and accelerated cyclic crack-propagation rates) increases significantly with R; (3) heat treatment can be adjusted to minimize the incidence of cleavage; and (4) slight variation in alloy processing serves to eliminate cleavage and promote striation formation, while enhancing the fracture toughness.
Character of Fatigue Fracture Surface Micromorphology in the Ultra-Low Growth Rate Regime
Authors: Hertzberg RW , Mills WJ
Published: March 2009

The fatigue fracture surface micromorphology in the ultra-low growth rate regime has been examined in aluminum, copper, nickel, titanium, and iron based alloys. A transition from striated to faceted fracture surface appearance is found for all materials examined. For the aluminum alloys a faceted appearance was observed over a three decade growth rate regime down to 5 × 10−9 mm/cycle for which macroscopic test data are available. At intermediate crack growth rates (2 × 10−5 to 1 × 10−4 mm/cycle) where the striation mode usually dominates, evidence of the faceted morphology is also seen and persists to higher growth rates within this growth rate range the lower the stacking fault energy of the material. This is believed related to a preference for faceted growth in planar slip materials. Faceted growth is produced at low ΔKapp levels under uniform loading conditions and at low ΔKeff levels associated with complex load interactions. The fracture facets generated by these two conditions are not readily distinguishable. Finally, it is not yet possible to identify the increment of discontinuous crack extension on the fracture facets in the crack growth regime where discontinuous crack extension must occur.
Approaches to Subjective/Objective Correlations in Flavor
Authors: Dravnieks A
Published: March 2009

Flavors are combinations of many subjective (sensory) properties, each of which depends in a complex way on the objective compositional characteristics of a product. A systematic approach to the design, control, and modification of flavor requires uncovering the functions that relate the various sensory properties to the analytical parameters, including the composition of headspace vapors. Available low-cost computerized programs are easily and routinely applicable to the search for such complex subjective/objective correlations. Allowances must be made in the data treatment for nonlinear correlations and interactions between the parameters. This approach is illustrated by a study of beer flavor.
General Guidelines for Selecting Objective Tests and Multiple Regression Applications
Authors: Kramer A
Published: March 2009

The objective assessment of any sensory quality parameter must be based on its agreement with subjective “panel” evaluation. First, each sensory parameter must be accurately defined by a profile-type panel and results on a limited number of specimens correlated with several proposed objective tests. The selected procedure (r = 0.9<) is then correlated with difference-type panel scores on an adequate number of specimens (40+). The objective test should then be refined to improve precision and calibration. For scaling purposes, a consumer preference-type panel must be used, and the quality levels (grades) must be determined from the regression equations where panel scores are the dependent (y) variable and the objective test data are the independent (x) variable(s).
High-Strength Steels—Formability and Applications
Authors: Dinda S , Kasper AS
Published: March 2009

Several high-strength sheet steels have been developed for the automotive industry for weight reduction. These high-strength materials have different forming characteristics compared with commonly used low-carbon steels. Formability parameters obtained from tension tests are discussed in detail to predict the forming behavior of these steels in stamping operations. The economic justification for material substitution in terms of strength levels and grades is discussed. Examples of formed automotive components are shown, and the material grade selections for these parts are also explained.
Relationship Between Microstructure and Formability in Two High-Strength, Low-Alloy Steels
Authors: Rashid MS , Cprek ER
Published: March 2009

Variations in the strain hardening behavior of GM 980X and a vanadium-strengthened SAE 980X steel were investigated as a function of strain. Changes in the microstructural deformation characteristics of the two steels were evaluated by scanning electron microscopy after biaxial and uniaxial deformation. Plastic deformation was found to occur in the SAE 980X steel by deformation of the ferrite matrix, while in GM 980X it occurred by deformation of both the ferrite and martensite phases. The GM 980X ferrite matrix was found to have a much higher work-hardening rate than that of the SAE 980X steel. Failure occurred in the SAE 980X steel when the ferrite was highly strained. In GM 980X it occurred after more extensive deformation had occurred, and the martensite phase was also highly strained. It was concluded that the higher work-hardening coefficient of the ferrite matrix and the deformable martensite phase combine to give GM 980X its superior formability.
Relationship Between Surface Characteristics and Galling Index of Sheet Steel
Authors: Hilsen RR , Bernick LM
Published: March 2009

The influence of annealing atmosphere and surface finish of cold-rolled steel on the occurrence of galling during stamping operations has been noted empirically for many years. In order to minimize the galling tendencies of drawing quality sheets a program was carried out to define pertinent surface features and their interaction during stamping.

Commercial steel coils were processed in two types of annealing atmospheres, a hydrogen and nitrogen mixture (HN) and DX-type exothermic gas. The coils were then skin rolled to achieve a wide range of surface roughness. The sensitivity to galling was rated during the stamping of quarter panels and also by means of a sliding friction test in which the ratio of static to dynamic drawing force was used to designate a friction ratio that appeared to correlate well with performance. Surface finish was recorded by standard profilometry techniques, and chemical differences between the types of surfaces were examined by auger electron spectrometry; general aspects of the surfaces were studied by scanning electron microscopy.

The critical frictional ratio was found to be 1.3, above which sheet steel has galling tendencies. Galling in HN-annealed steel was found to be surface-finish sensitive, and a range of surface finish parameters for nongalling characteristics has been established. DX-annealed steel appeared to be insensitive to the effects of surface finish, and differences in surface films were detected to account for the frictional changes.
Multicylinder Test Sequences for Evaluating Automotive Engine Oils
Authors: ASTM Engine Test Monitoring Center
Published: March 2009

Description

The test methods described in this publication have not been subjected to the ASTM Standardization Procedure. They are not standards or standard recommended practices of the American Society of Testing and Materials.
Defect Sensitivity in “Lamb Wave” Testing of Thin-Walled Tubing
Authors: Wiklund J
Published: March 2009

Ultrasonic testing of fuel cladding usually involves the use of moderate- frequency search units. The relatively thin wall, small radius of curvature, wave length, and physical size of sound beam are considerations in describing the predominant type of ultrasonic wave resulting and the nature of the energy reflection process at a defect.

Shear and Lamb waves are generally assumed to be the main wave forms pertinent to fuel clad testing. The observed waves are discussed with regard to their nature and ability to permit excitation over wide incident angle ranges and to such properties as attenuation and sensitivity to some types of defects. General Lamb wave theory is not sufficient to explain the behavior of the waves. A new model describing a surface wave or possibly a degenerated Lamb wave is outlined and discussed with reports of laboratory measurements as well as observations from practical testing using both echo technique and through-transmission.
Effect of the Annealing Temperature on the Creep Strength of Cold-Worked Zircaloy -4 Cladding
Authors: Frenkel JM , Weisz M
Published: March 2009

Transverse creep strength of Zircaloy-4 tubing annealed in the range of 440 to 650°C has been evaluated by internal pressure tests, short-time control tests at 400°C, and long-time tests, as well as out-pile or in-pile, between 330 to 400°C.

For low and intermediate stresses (lower than 133 MPa), it is observed that transverse creep strength increases while the annealing temperature is increased from 440 to 650°C. In-pile tests do confirm this trend.

The effect of the annealing temperature on the yield and creep anisotropy of the tubes has been evaluated at 400°C. From these results, it is concluded that the beneficial effect of a recrystallization treatment on the creep strength of Zircaloy-4 tubes is related to an effect of texture variation.
Creep Strength of Zircaloy Tubing at 400°C as Dependent on Metallurgical Structure and Texture
Authors: Källström K , Andersson T , Hofvenstam A
Published: March 2009

Zircaloy tubes were cold worked 50 or 80 percent to a series of textures and annealed at 475 to 575°C. Tube specimens were creep tested under internal pressure at 400°C with the transverse creep stress 152 MPa for 240 h, after which the transverse strain was measured.

Annealing at 510 to 520°C in the temperature range of partial recrystallization gives maximum transverse creep strength. The creep strength maximum is higher the lower the degree of cold work. The high creep strength is caused by an optimum dislocation structure which is reached through recovery without copious recrystallization.

Complementary creep tests under tensile load showed that the creep strength is lower transversely than longitudinally. This creep anisotropy may be explained in relation to texture by the action of <1123> dislocations. The transverse creep strength dependence on texture variations indicates that more radial basal poles give lower creep strength than more tangential basal poles. However, this texture effect is smaller than the effect of cold work, within the ranges of practical interest.
In—Reactor Creep of Zr—2.5Nb Tubes at 570 K
Authors: Ibrahim EF
Published: March 2009

Tubular specimens of Zr-2.5Nb, 23 mm internal diameter, have been creep tested in-reactor at 570 K. Specimens were biaxially stressed by internal pressure, with transverse stresses from 103 to 317 MPa. Two separate experiments are reported (a) U-501/2 which has specimens quenched from 1045 K; cold drawn 2, 12, or 20 percent and aged at 773 K for 24 h, and (b) U-501/3 which has specimens extruded; cold drawn 10, 23, or 33 percent and stress relieved at 673 K for 12 h.

Creep curves for quenched, cold-worked, and aged specimens (U-501/2) are best fitted by linear creep rates beyond 1000 h. Increasing cold-work between quenching and aging decreases creep strength; material with 20 percent cold-work creep at about twice the rate of material with 2 percent cold-work at the same stress.

Creep curves for cold-drawn and stress-relieved specimens (U-501/3) are best fitted by a time exponent of about 0.8, that is, creep strain = A × Bt0.8 where t = time and A and B are parameters which depend on material and stress indicating that creep rate may be decreasing with time. Creep rates increase with amount of cold work: the specimens with 33 percent cold-work creep about 40 percent faster than those with 10 percent cold-work.

Increasing amounts of cold-work is, therefore, detrimental to the in-reactor creep strength of Zr-2.5Nb either after extruding or between (α + β)-quenching and aging.
Microstructure of the Oxide Films Formed on Zirconium-Based Alloys
Authors: Sabol GP , McDonald SG , Airey GP
Published: March 2009

Microstructural characterization of oxide films formed on zirconium-based alloys was performed by use of scanning and transmission electron microscopy. Examination of pre-transition films formed on Zircaloy-4 oxidized in 360°C (680°F) water revealed a small grain size of approximately 100 Å (10 nm) diameter. In addition, a gradation of grain size was observed throughout the film thickness, such that at the oxide-water surface (oldest oxide), a grain size of less than 50 Å (5nm) was observed, and at the metal-oxide surface (newest oxide), the grain size was approximately 200 Å (20 nm). In post-transition films the outermost oxide still possessed the very fine 50 Å (5 nm) diameter grain size. However, the newest oxide of post-transition films consisted of relatively large grains, with grain diameters of 1000 to 5000 Å (100 to 500 nm). At the midthicknesses of these oxides intermediate grain sizes were observed. The bulk of the post-transition films was highly porous. Pore sizes ranged from approximately 10 to 150 Å (1 to 15 nm), and many connected pores were concentrated at the grain boundaries. Under more severe oxidizing conditions, imposed by increasing the corrosion temperature to 427°C (800°F), the growth of large grains at the metal-oxide interface was unstable and film growth proceeded by the nucleation of finer grains.

The results obtained conclusively establish the belief that the bulk of the post-transition oxide film is of nonprotective character as is obvious from the connected pore networks. A film growth model consistent with the experimental observations is that initial oxide formation is by nucleation at many sites. Growth of grains of certain orientations is favored, however, and these select grains expand in size at the expense of the less favorably oriented grains as the film thickens. Grain growth proceeds until a limiting size of 2000 to 5000 Å (200 to 500 nm) is reached. Further film growth induces nucleation of new grains at the metal-oxide interface. In thick scales, sequences of grain nucleation and growth are believed to occur.