bluuebunny/crossref_metadata_2025_split huggingface dataset:
Learning from Experience of the Stress-Corrosion Failure of High-Strength Aluminum Alloy Forgings
Authors: Cina B , Kaatz T 
Published: March 2009

Despite the extensive literature on the subject and the known methods for preventing stress corrosion, the users of high-strength aluminum alloys are still on occasion faced with this problem particularly in wrought components. Examples from actual experience with aircraft forgings are cited to emphasize the susceptibility of the transverse direction, particularly at parting lines, and the complex and often unpredictable role of residual stresses. Despite the absence of a specific short transverse direction, cylindrical forgings can show considerable susceptibility in their single transverse direction. Attention is drawn to the possibly dangerous combination of stresses resulting from heat treatment, machining, and interference assemblies.
It is shown that the mere presence at the surface of a forging of residual compressive stresses resulting from heat treatment is no guarantee that stress-corrosion failure will not initiate from such a surface.
Residual stresses developed along the inside diameter of a blind hole on quenching are a major unknown, and methods for obviating such difficulties are discussed.
In addition to the factors known to affect stress-corrosion susceptibility, there would also seem to be a batch factor whereby some apparently small and temporary modification in manufacturing procedure can increase the susceptibility to stress corrosion significantly.
An example is quoted of the minute amount of moisture found sufficient to initiate a stress-corrosion failure.
The necessity is discussed and emphasized for determining the nature and gradient of residual stresses adjacent to potentially critical surfaces as a stage in the qualification of prototype forgings.
Stress-Corrosion Crack Growth in Surface-Cracked Panels of High-Strength Steels
Authors: Shahinian P , Judy RW 
Published: March 2009

Stress-corrosion crack growth in 17-4PH and 4340 steels in 3.5 percent sodium chloride solution was examined over a wide range of KIscc/σys values by electrochemically coupling the 17-4PH steel to aluminum, zinc, magnesium, and open circuit and by testing the 4340 steel at three strength levels in open circuit.
It was demonstrated that the parameter, KIscc, determined from small cantilever bend specimens can be used to predict the flaw size/stress level combinations required for the onset of crack growth in large surface-cracked tensile panels. For this purpose the stress-intensity values for the surface-cracked panels were calculated from the basic surface-flaw equation.
The microfracture processes in the stress-corrosion cracking included intergranular, cleavage, and microvoid coalescence, the proportion of intergranular became greater with increase in negative electrochemical potential.
Stress-Corrosion Cracking Evaluation of Aerospace Bolting Alloys
Authors: Taylor E 
Published: March 2009

The susceptibility of aerospace bolting alloys to stress-corrosion cracking has been of continuing interest especially since strength levels have by far exceeded 200 000 psi, the threshold above which failures are much more common. The search for a stress corrosion resistant material has progressed through a number of alloys with strength levels up to 300 000 psi.
All of the high-strength steel alloys exhibted a similar trend where time to failure decreases as strength level increases. However, different levels of immunity were observed for the different alloys. Martensitic stainless steels were found to be much more resistant to stress-corrosion cracking but were very sensitive to hydrogen embrittlement from plating or galvanic corrosion reactions.
The use of a MIL-STD-1312 test procedure to evaluate coated or plated alloy steel bolts is sanctioned because of the short time to failure required, the reproducibility of results, and the duplication of service failures. The same is not true for the more resistant alloys where times to failure are in thousands of hours and results are scattered. A more aggressive test is warranted.
Crevice corrosion and pitting at interfaces are the most common initiators of stress-corrosion cracking failures for high-strength fasteners. Since this is unavoidable with fastened joints, it behooves the consumer to realize all of the advantages and disadvantages of various materials so that he may select the best one for his needs.
Corrosion Thresholds for Interference Fit Fasteners and Cold-Worked Holes
Authors: Kaneko RS , Simenz RF 
Published: March 2009

Empirical relationships were obtained between fastener interference or hole expansion and the stress-corrosion thresholds of aluminum alloys. Tensile and stress-corrosion threshold properties were determined for single heats of 2024-T3, 7075-T6, 7075-T76, and 7050-T76 extruded bar used in the studies. The various fastener and hole expansion systems, with a range of interference levels to over 10 mils, were installed in the principal grain directions of each alloy. Specimens were subjected to 3.5 percent sodium chloride alternate immersion and seacoast exposures, then analyzed by visual and metallographic techniques.
The residual tensile stresses created around the holes appeared to rise sharply with increasing amounts of interference, approaching a theoretical limit. Even low interference fits of a few mils caused stress corrosion under the more susceptible conditions. Crack initiation tended to occur further from the hole as interference increased; wet sealant installation helped to reduce galvanic reactions in the vicinity of the hole. Estimated stress corrosion potential over a range of interference fits in aluminum alloys is presented.
Effects of Ferrite and Sensitization on Intergranular and Stress-Corrosion Behavior of Cast Stainless Steels
Authors: Beck FH , Juppenlatz J , Wieser PF 
Published: March 2009

Cast stainless steels of the CF grades (19Cr, 9Ni), which find widespread application in the chemical, petrochemical, and power generating industry, were subjected to intergranular corrosion tests (Huey) and stress-corrosion tests (vapor phase of aqueous 875-ppm sodium chloride (NaCl) solution at 477 K [400°F]) to evaluate the effect of ferrite in the range of 0 to 40 ferrite numbers, in the solution-annealed and in the sensitized condition.
The intergranular corrosion tests demonstrated beneficial effects of ferrite for all the alloys tested in the solution-annealed condition and for the molybdenum-free cast steel grades in the sensitized condition. Ferrite increased the sensitization effects on intergranular corrosion for the molybdenum-bearing grades. Highest corrosion rates in Huey tests, based upon weight loss measurements, do not necessarily mean deepest intergranular attack. Intergranular attack was found to terminate at ferrite-austenite grain boundaries. The intergranular corrosion test results would indicate that ferrite numbers exceeding 10 offer greater operating safety for cast, corrosion resistant grades, CF-3, CF-3M, CF-8, and CF-8M in the solution-annealed condition and also, in the event of sensitization, for cast corrosion-resistant grades CF-3 and CF-8.
Significantly increased resistance to stress-corrosion cracking with increasing ferrite content was observed for cast steels in the solution-annealed and in the sensitized condition. These stress-corrosion cracking tests would indicate that ferrite numbers of 10 or more offer greater operating safety for cast corrosion-resistant CF grades in the solution-annealed as well as in the sensitized condition.
Effect of Inclusions on Sulfide Stress Cracking
Authors: Ohki T , Tanimura M , Kinoshita K , Tenmyo G 
Published: March 2009

Sulfur was taken as a residual element in steel for investigating the sulfide stress-cracking characteristics. The tests were performed by controlling the shape and the amount of the sulfide inclusions by adding rare earth metal (REM) and varying the sulfur content from 0.002 to 0.019 percent. Susceptibility to sulfide stress cracking was found to be correlated to the sulfur content and also to the shape of the inclusions.
Detailed observation of crack nucleation showed that though precracks nucleate and grow from elongated sulfide inclusions to form large cracks in conventional steels, the nucleation can be suppressed by controlling the shape of sulfide inclusions to the globular type.
The results of this work suggest that controlling the shape of sulfide inclusions by adding an optimum amount of REM is so effective that it would completely minimize the detrimental effect of sulfur against hydrogen sulfide stress cracking.
Fracture Toughness Testing Using the C-Shaped Specimen
Authors: Underwood JH , Kendall DP 
Published: March 2009

Fracture toughness testing of material with cylindrical geometry is discussed, and the inherent advantages of the C-shaped specimen in this situation are given. A K calibration equation for the C-shaped specimen is presented which is based on boundary value collocation results. The C-shaped specimen K calibration is compared with those for the standard compact specimen and the single-edge-notched bar specimen.Guidelines for measuring plane-strain fracture toughness (KIc) using the C-shaped specimen are described, including (a) a KI calibration which applies over a wide range of diameter ratios and to two load point locations in segments of hollow cylinders, as well as over a range of crack lengths, (b) compliance and crack-mouth-displacement analyses and their use to obtain critical value of KI in a fracture toughness test, and (c) suggested specimen geometries to be used in performing KIc tests with C-shaped specimens.The use of C-shaped specimens for performing J-integral fracture toughness tests and fatigue crack growth tests is described, and some preliminary testing guidelines are offered. Included are suggested methods of load-point-displacement measurement for J-integral tests and suggestions for the geometry and K calibration which could be used in fatigue tests.
Recent Developments in JIc Testing
Authors: Landes JD , Begley JA 
Published: March 2009

The J-integral, as proposed by Rice, has been shown to characterize the crack-tip stress and strain field under both elastic and plastic stress-strain conditions. The parameter offers a logical extension of linear elastic fracture mechanics concepts to include cases of large-scale plastic behavior. Begley and Landes proposed the J-integral (labeled JIc) as a measure of material fracture toughness under plane-strain conditions ranging from linear elasticity to large-scale plasticity. Data originally presented by Begley and Landes on two steels showed that JIc characterized fracture toughness under fully plastic conditions and was compatible with KIc in the linear elastic range. Subsequent work has shown that this approach is successful in a variety of metal alloy systems.
In this paper the basis for the JIc approach to fracture toughness characterization is discussed. The recent developments in the method for determining JIc experimentally are explained as well as the future trends in the development of the test method. The present test method relies on the development of a fracture resistance curve where J is plotted as a function of stable crack extension. The present method employs multiple specimens where each specimen supplies one point on the fracture resistance curve. New test methods have been developed which allow this curve to be developed from a single specimen.
Sample data are presented to illustrate the method. The relationship between KIc and JIc is illustrated in regions where both test methods apply. The present work directed at establishing the limitations of the JIc test method is presented, A brief description of the extension of the J-integral approach to other areas of cracking behavior is also included.
Heavy-Section Fracture Toughness Screening Specimen
Authors: Shannon JL , Donald JK , Brown WF 
Published: March 2009

Size requirements for a pin-loaded double-edge notch plus crack tension specimen proposed for fracture toughness screening heavy-section alloys were studied. Ranking of eight selected alloys based on the specimen's net strength was compared with that based on the valid plane-strain fracture toughness separately determined. Performance of the specimen was judged on the basis of that comparison.
The specimen's net strength was influenced by three critical specimen dimensions: distance between the crack plane and the loading hole, specimen width, and specimen thickness. Interaction between the stress fields of the crack and the loading holes reduced the net strength, but this effect disappeared as the separation reached a dimension equal to the specimen width. The effects of specimen width and thickness are interrelated and affect the net strength through their influence on the development of the crack-tip plastic zone. Correlation between the net strength of the screening specimen and the plane-strain fracture toughness was enhanced by increasing thickness and decreasing width of the screening specimen.
The work described is intended to form the technical base for the development of a standard fracture toughness screening test method for heavy sections to supplement ASTM E 338 Standard Method of Sharp Notch Tension Testing of High-Strength Sheet Materials. Development of the test method is the responsibility of the ASTM E24.01.02 Task Group on Revision of E 338.
Investigation of Some Problems In Developing Standards for Precracked Charpy Slow Bend Tests
Authors: Succop G , Bubsey RT , Jones MH , Brown WF 
Published: March 2009

Precracked Charpy slow bend tests and plane-strain fracture toughness (KIc) tests were made on the following alloys: (1) 4340 and 18Ni maraging steels heat treated to a wide range of strength levels; (2) several 2000 and 7000 series aluminum alloys; and (3) a metastable beta titanium alloy, Ti-8Mo-8V-2Fe-3Al. Load-deflection records for the precracked Charpy specimens were obtained from measurements of tensile machine screw rotation and directly from the specimen deflection. It was shown that records obtained from screw motion measurements contained large extraneous components of deflection arising primarily from elastic strains in the tensile machine. The magnitude of these components will be a function of the compliance of the testing machine and, depending on the method of record analysis, can have a substantial influence on the derived W̄/A values. Load-deflection record analysis procedures are presented which minimize the effects of these extraneous deflections. If the deflections are obtained from measurements made directly on the specimen, the influence of the tensile machine compliance for practical purposes may be neglected, and a simplified method of record analysis can be used which does not involve graphical integration of the load-deflection trace.
Relations between W¯E/Aσ ys2 and the crack size factor KIc2/σ ys2 are presented for the alloy conditions investigated. In all but a few cases there was a general upward trend in the Charpy energy values with increasing crack size factor. In some cases, excellent correlation was obtained. Where relatively large scatter was observed, the Charpy derived values in a few cases did not follow the trend of the crack size factor. Apparently no generalizations can be made concerning the degree of correlation that can be expected between precracked Charpy energies and plane-strain fracture toughness. Correlations can be useful but should be established carefully over the complete range of toughness of interest.
The authors recommend that an ASTM test method be developed for the slow bend precracked Charpy test and believe there is sufficient information available to do this now. Some suggestions along these lines are presented in this paper.
Influences of Secondary Stress Fluctuations of Small Amplitude on Low-Cycle Corrosion Fatigue
Authors: Endo K , Kormai K 
Published: March 2009

The influences of small superimposed stress fluctuations on low-cycle corrosion fatigue under trapezoidal waveform are varied by the susceptibility of the test materials to stress corrosion cracking (SCC).
The corrosion-fatigue life of the materials which are insensitive to SCC is greatly diminished if small stress fluctuations are superimposed. The crack initiation is shortened somewhat by such a superposition.
In materials sensitive to SCC, the corrosion-fatigue life is almost occupied by the crack growth period, and the crack rate greatly decreases with the superposition of small stress fluctuations under Kmax higher than KISCC. Under low Kmax which is nearly equal to KISCC, the similar characteristics to that of the materials insensitive to SCC are obtained. The effects of stress change on corrosion fatigue component and SCC component have been discussed.
Corrosion-Fatigue Behavior of Some Special Stainless Steels
Authors: Amzallag C , Rabbe P , Desestret A 
Published: March 2009

We have studied the corrosion-fatigue crack initiation and propagation of different types of steels: two austenitic, one austenitic-ferritic, and one ferritic. The testing program had been established in order to define, particularly, the part in corrosion fatigue of electrochemical effects and mechanical damage. Tests were carried out on smooth specimens in rotating bending and on precracked specimens in tension in air, and in a 3 percent aerated solution of sodium chloride.
The capacity of the metal for dissolution and repassivation seems largely responsible for the behavior of the metal in the corrosive solution. This capacity varies notably with the composition of the metal, the loading conditions of the specimens, and the characteristics of the corrosive medium.
Fatigue of Tantalum in Sulfuric Acid at 150°C
Authors: Seastrom CC 
Published: March 2009

Tantalum is resistant to 80 percent sulfuric acid (H2SO4) at 150°C (302°F). However, data on fatigue of tantalum under these conditions were unavailable. To determine design criteria for a tantalum pump impeller, high frequency fatigue tests were conducted over a range from less than 106 to over 9 x 109 cycles, establishing approximate stress amplitudes which allow tantalum to achieve up to 8 × 109 cycles of loading without failure. These stresses were found to be about 11 ksi (7.7 kg/mm2) for unalloyed tantalum and about 12.4 ksi (8.7 kg/mm2) for Ta-2.5W. These two tantalum alloys were deliberately processed to create very soft materials with large grain sizes. Such materials may indicate behavior of these alloys in or near weld areas.
Case histories are presented on two Ta-2.5W pump impellers which failed in 80 percent H2SO4. The cracks were generally associated with welds. The crack surfaces show evidence of corrosion fatigue and cleavage fractures. The areas of cleavage fracture suggest an environmental effect such as hydrogen-assisted stress corrosion cracking.
Static and Dynamic Strain Measurements for Embankments
Authors: Dietrich RJ , Salley JR 
Published: March 2009

The U.S. Department of Transportation and the Atchison, Topeka, and Santa Fe Railway Co. (ATSF) are jointly sponsoring a railroad test embankment on the main line of the ATSF system. The test embankment is nearly 2 miles long and is comprised of a minimum thickness of 6 ft of compacted, highly plastic clay. The embankment is divided into nine test sections, each with a unique track support system but having identical embankment instrumentation.
This paper discusses the considerations leading to final design, fabrication, and installation of the embankment instrumentation. The embankment instrumentation was developed to provide quantitative data on embankment performance and response to aid in the comparative evaluation of track structure performance. Emphasis was placed on reliable measurements of dynamic embankment strain. Provisions for measurement of long-term deformations and volume changes in the highly plastic clay embankment were also provided. Each of the nine test sections has one principal instrument array supplemented by additional instruments spaced to verify that the performance at the main arrays is typical for that test section. The main array instrumentation includes vertical extensometers, portable horizontal extensometers which will be inserted in flexible horizontal tubing embedded in the embankment, pressure cells, and moisture-temperature cells. The instrumentation was specifically designed for this project.
A Fractographic Study of the Edge-Sliding Mode in Fracture Toughness Testing
Authors: Jones DL , Chisholm DB 
Published: March 2009

A fractographic study of Mode II fracture surfaces has been conducted for the purpose of identifying the microstructural mechanisms responsible for fracture in the edge-sliding mode. A compact shear (CS) specimen developed by the authors was employed to generate the fracture surfaces and also to establish Mode II fracture toughness values (KIIc) for Ti-6Al-4V, A533-B steel, and several aluminum alloys. In all tests, one of the two edge cracks sustained complete Mode II fracture while the other exhibited only a limited amount of subcritical crack growth. Mode II fracture surfaces, which were unique in appearance, have been examined by optical and scanning electron microscopy.
It was determined that shear (or parabolic) microvoid coalescence was the dominant mechanism for Mode II fracture. The smallest dimples were about ½ to 1 µm in diameter and were about the same size for all alloys studied. However, a significant portion of the fracture surfaces were abraded against their mating crack surfaces so that no initiation mechanisms could be observed in these regions. It was established that most of the surface abrasions were created by the relative sliding of the fracture surfaces during unstable fracture rather than the crack initiation process. Some tendency for brittle fracture on crystallographic planes of maximum shear was also observed.
Formability and Fracture of Some Higher Strength Aluminum Alloys
Authors: Sowerby R , Sareen BK 
Published: March 2009

This work presents the comparative behavior of some formable grades of aluminum alloy sheet and an aluminum killed drawing quality (AKDQ) steel sheet in a number of formability tests. Tensile data were assembled from specimens cut at different orientations in the plane of the as-received sheet. An attempt was made to fit the stress-strain data with an empirical equation of the form σ¯ = k (ϵ0 + ϵ¯)n. The following quantities were also obtained from the tension tests: uniform strain, the plastic strain ratio (r value) and fracture strain. The aluminum alloys showed inferior r values and lower values of fracture strain when compared with the steel sheet; the n value did not always correlate well with the measured uniform strain in the alloys.
The aluminum alloys were deformed under different conditions of biaxial straining by stretching over a rigid punch, and forming limit diagrams were constructed. From the same test it was also possible to assess the fracture strains. The fracture thickness strain does not appear to be a single valued material property but can be dependent upon the deformation mode rather like the limit strain.
Additional tests performed on the materials included bulging in a circular die under hydraulic pressure, an in-plane torsion test, and an in-plane stretch test designed to promote a plane-strain deformation mode. The results from these tests supplemented the limit and fracture strain data gathered from the punch-stretch tests.
The aluminum alloys could be formed but showed inferior formability to the AKDQ steel. The lower fracture strains exhibited by the alloys may influence the behavior in certain plastic forming processes in a manner that would not be anticipated on the basis of n value predictions.