| The Effect of Load Ratio and Grain Size on Fatigue Crack Growth Rates in Nickel Base Superalloy AP-1. |
1991 |
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| Authors:
S. Kim; J. F. Knott; RESERVED SOURCE
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 | Fatigue crack propagation rates have been investigated in the powder metallurgy formed nickel base superalloy AP-1. Fatigue crack growth data are presented for different microstructures and load ratio throughout the life history of the crack and discussed in terms of current theories of fatigue crack propagation. The experimental results indicate that threshold values for crack growth depend on load ratio and grain size. However, the effective threshold values are virtually ... |
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| Effects of Testing Method on Cyclic Hardening Behavior in Face-Centered-Cubic Alloys, |
JAN 1988 |
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| Authors:
A. C. Pickard; J. F. Knott; CAMBRIDGE UNIV (ENGLAND) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| Several types of test methods are employed to evaluate the cyclic hardening behavior of engineering alloys. Three such tests are the plastic-strain limit (PSL) test, the multiple-step test (MST), and the incremental-step test (IST). In each type of test, the material experiences a different plastic-strain history prior to measurement of the saturation stress. The present paper examines effects of these different histories on cyclic hardening behavior in a number of ... |
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| Fatigue Crack Retardation in Aluminium Alloys, |
JUN 1987 |
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| Authors:
D. J. Alexander; J. F. Knott; CAMBRIDGE UNIV (ENGLAND) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| Fatigue crack retardation due to single tensile over-loads has been studied in aluminum alloys 7010-T7651 and 8090-T851, for delta K = 7 MPa square root of m, R = 0.1 and 0.5, and specimen thicknesses of 6.35, 13 and 35 mm. Retardation lasts for many more cycles and extends over a greater distance in the 8090 alloy, for similar test conditions. Crack closure cannot explain retardation in the 7010 alloy. ... |
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| The Effect of Temperature on Fatigue Crack Initiation from Aluminosilicate Inclusions, |
JUN 1987 |
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| Authors:
P. Woollin; J. F. Knott; CAMBRIDGE UNIV (ENGLAND) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| Fatigue cracks have been observed to initiate and grow from aluminosilicate inclusions in powder formed alloy AP-1 at stress intensities below the long crack threshold, both in air and under vacuum. Measured crack growth rates lie below previously reported short crack growth rate data for Astroloy under similar conditions. This is consistent with the presence of residual, tessellated stress fields associated with the inclusions. In vacuum, higher crack growth rates ... |
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| Microstructural Effects on Flow Localization in 7000 Series Aluminium Alloys (Al-Zn-Mg-Cu), |
1986 |
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| Authors:
J. J. Lewandowski; J. F. Knott; CAMBRIDGE UNIV (ENGLAND) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| Cylindrical (5.4 mm in diameter) specimens of 7010 and 7475 were prepared in peak-, under-, and over-aged conditions to vary microstructure. Room temperature tensile, torsion and notch bend test results are reported. An attempt is made to isolate the effect of microstructure on flow localization from the effect of work hardening. |
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| Effects of Segregation and Environment on Fatigue Crack Growth at Elevated Temperatures, |
1986 |
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| Authors:
P. Bowen; J. F. Knott; CAMBRIDGE UNIV (ENGLAND) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| A533B specimens were austenitized for one hour at 1250 C and oil quenched prior to fatigue testing in vacuum and air at 290 C at R-ratios of 0.1 and 0.5. There were marked decreases in da/dN, marked increases in threshold stress intensity and marked differences in the crack growth mechanism in the vacuum environment versus the tests in air. |
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| MICROSTRUCTURAL EFFECTS ON FLOW LOCALIZATION IN 7000 SERIES ALUMINUM ALLOYS ( ALUMINUM-ZINC-MAGNESIUM-COPPER ). |
1986 |
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| Authors:
J. J. Lewandowski; J. F. Knott; CAMBRIDGE UNIV (UNITED KINGDOM) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| The Influence of Microstructure and Temperature on Near-Threshold Fatigue Growth in Air and Vacuum, |
1984 |
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| Authors:
J. M. Kendall; J. F. Knott; CAMBRIDGE UNIV (ENGLAND) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| BS4360-43A specimens 10 and 20 mm thick were given various heat treatments to vary the grain size. Fatigue crack growth rate was measured in air and vacuum at room temperature, a frequency of 65 Hz and an R ratio of 0.5 to study the grain size effect which averaged 12, 42 and 53 microns in the specimens. The 12 micron specimens were also tested in air at 20 and 150 ... |
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| CRYSTALLOGRAPHIC FATIGUE CRACK GROWTH IN ALUMINIUM ALLOYS, |
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| Authors:
G. G. Garrett; J. F. Knott
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