Effect of Stress Ratio on Fatigue Crack Growth Rate at Notched Hole in 7075-T6 Aluminum Alloy Under Biaxial Fatigue
Effect of Stress Ratio on Fatigue Crack Growth Rate at Notched Hole in 7075-T6 Aluminum Alloy Under Biaxial Fatigue
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双轴疲劳下应力比对7075-T6铝合金缺口孔疲劳裂纹扩展速率的影响
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发表时间：
2016
期刊：
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通讯作者：
Reja Alshahrani
中科院分区：
文献类型：
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作者：
Reja Alshahrani
摘要：本文研究了7075-T6铝合金板制成的十字形缺口试样在不同应力比下在实验室空气和盐水（3.5%NaCl）环境中的疲劳裂纹扩展速率行为。在双轴比为1、加载频率为10 Hz的条件下，研究了应力比为0.1、0.5、0.7的三种应力比下的面内双轴拉-拉疲劳裂纹扩展行为，并对三种应力比下的裂纹扩展行为进行了比较，研究了应力比对裂纹扩展速率的影响。有限元分析（FEA）被用来计算裂纹尖端的应力强度因子（Δ K）的循环变化。使用光学显微镜观察裂纹扩展速率。此外，试验产生更准确的定义的步行者方程参数，并导致更准确的预测疲劳裂纹扩展速率在不同的应力比。研究表明，应力比对裂纹路径方向没有影响。应力比的增加导致双轴加载试验下的疲劳裂纹扩展速率的增加。用步行者方程预测的有效疲劳裂纹扩展速率与实验室空气和盐水环境中试验产生的有效疲劳裂纹扩展速率非常接近。在盐水环境中，腐蚀加速裂纹扩展速率。
Abstract : This research investigates the behavior of fatigue crack growth rate in both laboratory air and saltwater (3.5% NaCl) environments for notched cruciform specimen made from 7075-T6 aluminum alloy sheet at different stress ratios. With biaxility ratio of 1, and frequency of applied load of 10 Hz, the crack growth behavior was investigated under in-plane biaxial tension-tension fatigue with 0.1, 0.5, 0.7 stress ratios and then compared them to study the effect of stress ratio on the crack growth rate. Finite Element Analysis (FEA) was used to calculate cyclic variation of stress intensity factors (delta K) at the crack tips. The crack growth rate was observed using optical microscopy. In addition, the test generates more accurate definition of the Walker equation parameters and leads to more accurate prediction of fatigue crack growth rate at different stress ratio. This study shows that there is no effect of the stress ratio on crack path direction. Increase in stress ratio leads to increase in the fatigue crack growth rate under the biaxial loading test. The effective fatigue crack growth rate predicted by Walker equation is very close to the effective fatigue crack growth rate generated by the test in laboratory air and saltwater environments. In the saltwater environment, the corrosion accelerates the crack growth rate.