Influence of Low Load Truncation Level on Crack Growth for Al 2324-T39 and Al 7050-T7451 |
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| Authors: | Tian Hailing Bao Zhang Jianyu Zheng Xiaoling Fei Binjun |
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| Institution: | aStrength Department, Shanghai Aircraft Research Institute, Shanghai 200232, China;bInstitute of Solid Mechanics, Beijing University of Aeronautics and Astronautics, Beijing 100191, China |
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| Abstract: | Tests with middle-crack tension (M(T)) specimens made of Al 2324-T39 and Al 7050-T7451 are conducted to investigate the influence of low load truncation level on fatigue crack growth. The six different truncated spectra are obtained by removing the small cycles of which amplitudes are less than the specified percentages of the maximum amplitude in the basic flight-by-flight loading spectrum and the remainder of the spectrum is untouched. The tests indicate that the mean level of fatigue crack growth life (FCGL) increases as the load truncation level is enhanced. Considering both the time saving and the influence on FCGL, there is an applicable choice (i.e. spectrum S2 or spectrum S3 in this investigation) for full scale fatigue test. The scatter of FCGL becomes much larger than that under the basic spectrum when the load truncation level is increased to a specified high level, mainly due to the occurrence of crack slanting and branching under the high level truncated loading spectra. |
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| Keywords: | fatigue crack growth aluminum alloys low load truncation flight-by-flight spectrum |
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