Microstructural influences on the growth of small cracks in Ti-6Al-4 V |
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Authors: | Ohchang Jin Richard W. Hamm W. Steven Johnson |
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Affiliation: | Former graduate student, currently Research Scientist, Air Force Institute of Technology, WPAFB, OH;Former graduate student, currently Product Engineer, Proctor &Gamble, Cincinnati, OH;Professor, School of Materials Science and Engineering and G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332–0245 |
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Abstract: | ABSTRACT The effects of microstructure on the growth of small cracks in Ti-6Al-4 V under fatigue loading are presented. The small crack growth is compared with large crack growth. Two large crack tests were performed at a stress ratio of 0.4 and a frequency of 15 Hz. For small crack growth tests, double edge notch specimens were loaded under constant amplitude at four maximum stresses with a stress ratio of 0.4 and a frequency of 15 Hz. A plastic replication technique was used to monitor the small fatigue crack growth rate. The microstructure consists of bands of α and β phases. The present study indicates that the crack growth direction and shape are dependent upon the grain size and grain orientations, and that the crack growth rate seems to be affected by the spacing of α-rich and β-rich bands. Small cracks are propagated at stress intensity factors well below the large crack threshold stress intensity factor. |
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Keywords: | constant amplitude loading double edge notch specimen large cracks microstructures small fatigue cracks titanium alloy |
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