bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.
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 &lt;1123&gt; 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.
Fracture of Zircaloy-2 in an Environment Containing Iodine
Authors: van der Schaaf B 
Published: March 2009

Many Zircaloy cladding failures and the results of out-of-pile iodine stress corrosion tests are so similar as to suggest that fission of uranium produces enough iodine to attack the cladding locally. This paper presents a study of the effects of iodine on the fracture of Zircaloy-2 sheet being stressed very locally. Discs produced from Zircaloy-2 sheet were bent biaxially by pressing an indentor into the center of the disc. The force necessary to penetrate the discs decreased when either the initial amount of iodine or the temperature was increased, for cold-worked as well as recrystallized Zircaloy-2. Uniaxial short-time creep tests and tests with stressed slotted rings, both performed in environments containing iodine, did not result in stress corrosion cracking.
Microprobe analysis of the regions adjacent to cracks revealed deposition of iodine compounds on the walls of narrow cracks or near the crack tips. The propagation of the cracks in cold-worked material is affected by the manufacturing process of the sheet. The main conclusion of this investigation is that a high degree of local deformation is needed before biaxially stressed Zircaloy-2 suffers from stress corrosion by gaseous iodine.