【摘 要】
：
To improve the fatigue performance of metal materials which are applied in the aeroplane structure is a significant objective of new material research.In recent decades, it becomes a common view that
【出 处】
：
2012 Postdoctoral Symposium of China on Materials Science &
论文部分内容阅读
To improve the fatigue performance of metal materials which are applied in the aeroplane structure is a significant objective of new material research.In recent decades, it becomes a common view that compressive loading in the tension-compression fatigue spectrum can accelerate the fatigue crack growth rate of the aluminum alloy.It is dangerous in the fatigue crack growth life prediction as a result of neglect of the effect of compressive stress, as provided in the former fatigue test standards.In the actual crack growth fitting formulas of aircraft design company, which have taken "compressive stress acceleration effect" into consideration, generally, there are several materials parameters should be determinate by a large number of test.It has been found that for a tension-compression stress cycle the crack tip parameters are determined mainly by two loading parameters, the maximum stress intensity Kmax in the tension part of the stress cycle and the maximum compressive stress maxcom in the compression part of the stress cycle.Based on the crack propagation mechanism of elastic-plastic fracture mechanics, an elastic-plastic finite element analysis of the effect of compressive loading on fatigue crack tip stress field in LY 12M aluminum alloy is presented.By the validation of test data, the fitted curves generated by two actual engineering models and a new double-parameter crack growth model, which can be used in the case of negative stress ratio, have been analyzed.By means of the compare with the degrees of linear correlation, R2, of each fitting line, good results of new model showed that it is a better engineering method of fatigue crack growth life prediction under negative stress ratio of aluminum alloy, and it is also a useful method of fatigue research of new material.
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