| Plastic Flow Normalizing the Fatigue Crack Propagation Data of Several Steels |
MAY 83 |
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| Authors:
J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON DC
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 | The model sees crack growth as a means of strain hardening material elements adjacent to the crack tip to counteract strength losses due to transient stress relaxation/creep and environmental surface attack. It defines limiting growth rates in terms of fixed as well as of strain-limited environmental action. Data on some 16 steels are compared to measured stress- strain data using the same model equations. Data fits are rather close, and ... |
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| Further Trials of a Strain Hardening Index of Fatigue Damage |
28 SEP 1982 |
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| Authors:
J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON DC
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| Previous cyclic-strain;, smooth-specimen fatigue tests of alpha-beta titanium alloys displayed an anomalous endurance enhancement for some of the alloy conditions. This could be explained by associating resistance to fatigue damage directly with the stress-normalized plastic strain hardening rate at the point of maximum cyclic tensile stress. Since this rate also controls the extent of stress-relaxation-induced tensile creep strain in each cycle, it was thought that fatigue damage might be associated ... |
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| Comparison of Notch-Stress with Strain-Controlled Low Cycle Fatigue of Alpha-Beta Titanium Alloys |
04 DEC 1981 |
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| Authors:
J. M. Krafft; G. R. Yoder; NAVAL RESEARCH LAB WASHINGTON DC
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| Prior studies of the present authors provided two different tests of low cycle fatigue endurance of the same set of titanium alloys. Strain controlled push-pull deformation of axial specimens covered crack initiation life of up to 1000 cycles. Notch stress controlled tensile load cycling extended the range to 1 million cycles. All of Ti-6Al-4V, the test materials varied in oxygen content and in effective grain size. The results could not ... |
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| Fatigue Crack Growth in A36/A283 Plate in Air and Sea Water Environments. |
26 MAR 1981 |
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| Authors:
F. R. Stonesifer; J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON DC
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| Extensive use of A36 type steels in wave-excited marine structures raises the question of its resistance to fatigue crack propagation in the sea water environment. Above its ductile-brittle transition temperature, static fracture of such a low strength steel usually entails extensive plastic deformation. However with cyclic loading, fatigue cracks can grow with little plastic flow, at crack loading levels well below that required for fracture instability. The hazard entailed has ... |
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| Effect of Stress-Strain Behavior on Low-Cycle Fatigue of Alpha-Beta Titanium Alloys. |
21 NOV 1980 |
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| Authors:
J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON DC
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| In earlier NRL work, Ti-6Al-4V in four levels of interstitial oxygen content and a single Ti-8Al-1Mo-1V alloy plate were heat treated to alter grain size and/or microstructural character; the effect on fatigue crack propagation rate was measured. In this work, small tensile specimens of these materials are subjected to slow strain-controlled cyclic deformation leading to rupture in the 5-500 cycle range. Indication of crack initiation as well as rupture life ... |
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| Case Studies of Fatigue Crack Growth Using an Improved Micro-Ligament Instability Model. |
30 JAN 1980 |
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| Authors:
J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON DC
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| The tensile ligament instability model TLIM has been refined and modified. A large set of new data cases is analyzed using the improved algorithm, most of these with high fidelity. In microstructurally varied titanium alloys, the process zone size is associated with the effective grain size; in structural and alloy steels it decreases with increasing yield strength, presumably here too related to grain refinement. The other fitting parameters, of environmental ... |
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| Application of Tensile Ligament Instability Model of Crack Propagation to UKOSRP Data on BS4360 Grade 50D Steel |
80 |
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| Authors:
J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON DC
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| Corrosion fatigue crack propagation data are given for BS4360-50D in sea water at 7 C and air at room temperature. Da/dN curves are also shown for A36 in air at room temperature. A mathematical model is presented which is called the tensile ligament instability model (TLIM) and is used to estimate fatigue endurance. |
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| Failure Studies of a Third Stage Fan Disk from a TF-30 Turbine Engine. |
13 NOV 1978 |
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| Authors:
W. H. Vaughan; R. J. Sanford; J. M. Krafft; W. H. Cullen; J. W. Dally; NAVAL RESEARCH LAB WASHINGTON D C
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| A detailed failure analysis was made of a fan disk from the third stage of the Navy's turbo-jet engine in order to gain a better understanding of the origing and growth kinetics of the cracks that had developed in service. The in service stress that had caused the cracks to originate was determined by a two dimensional photoelastic and holographic stress analysis. A further experimental stress analysis was made to ... |
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| Organizational Scheme for Corrosion-Fatigue Crack Propagation Data. |
JUL 1977 |
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| Authors:
J. M. Krafft; W. H. Cullen Jr; NAVAL RESEARCH LAB WASHINGTON D C
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| A model, proposed earlier, is modified in an attempt to explain a number of curious behaviors of corrosion-fatigue crack propagation (CFCP). The behaviors include effects of load ratio R in air and salt water vs. vacuum, and effects of loading frequency at fixed R in these environments. Assumptions of the modelling are reviewed in detail in view of earlier objections to them. The ingredients of CFCP per this model: Poisson ... |
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| Design and Verification Criteria for Missile Weight-Handling Equipment. |
OCT 1976 |
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| Authors:
E. R. Seibert; J. M. Krafft; H. L. Smith; George J. O'Hara; NAVAL RESEARCH LAB WASHINGTON D C
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| This report describes an NSPO sponsored task to evaluate the safety and structural reliability of TRIDENT-C4 missile handling equipment. In a first phase, draft of new design specifications were examined in view of current government and industry criteria for similar service. In this second phase, design stress allowables as well as a proof loading test policy for verification of structural integrity were assessed by study and experimental programs. Structural elements ... |
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| Acoustic Emission from Aqueous Stress Corrosion Cracking in Various Tempers of 4340 Steel. |
JUN 1973 |
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| Authors:
H. H. Chaskelis; W. H. Cullen; J. M. Krafft; NAVAL RESEARCH LAB WASHINGTON D C
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| A commercially available system is employed to detect and count acoustic emissions emanating from the aqueous stress corrosion crack propagation in 4340 steel. Standard ASTM E399 compact tension specimens are prepared in four tempering temperatures: 204, 316, 427 and 538C (400, 600, 800, 1000F). Crack length is monitored with a notch opening clip gage. Comparisons show the time rate of emission events to increase with stress intensity in rough correspondence ... |
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| IRRADIATION EFFECTS ON REACTOR STRUCTURAL MATERIALS. |
15 MAY 1970 |
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| Authors:
L. E. Steele; C. Z. Serpan Jr.; J. R. Hawthorne; J. M. Krafft; R. A. Gray Jr; NAVAL RESEARCH LAB WASHINGTON D C
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| The report includes: (1) results of a damage function approach to spectrum analysis for Army reactor SM-1, (2) analysis for fracture resistance in heavy thickness A533-B steel plate and weld metal, (3) the role of iron in the fracture of an irradiated pressure vessel steel, (4) the nature of observed radiation damage in vanadium, and (5) the effects of the fast reactor environment on the tensile properties of selected structural ... |
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| AN INTERPRETATION OF THE YODER-GRIFFIS-CROOKER OBSERVATIONS OF SUSTAINED-LOAD CRACKING IN TI-6AL-4V |
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| Authors:
J. M. Krafft
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Reports by Author
