摘要
该文研究了A357铸造铝合金在T5/T6两种热处理条件、应力比为0.05和0.7时的疲劳裂纹扩展行为,并用裂纹偏折模型对裂纹扩展速率曲线进行修正。研究结果表明,裂纹沿着树状晶边界扩展导致显著的裂纹偏折。在T5/T6两种热处理条件下,应力比r=0.05时的裂纹扩展速率均远小于应力比为0.7时的裂纹扩展速率,热处理方式对裂纹扩展速率没有影响。应力比r=0.7时,偏折裂纹模型修正后的裂纹扩展速率没有明显变化;而应力比r=0.05时,偏折裂纹模型修正后的裂纹扩展速率较修正前有显著增加。裂纹发生偏折时,采用同时考虑I型和II型裂纹的裂纹尖端有效应力强度因子描述裂纹扩展速率更合理也更准确。
The fatigue crack propagation behavior of A357 casting aluminum alloys at stress ratios of 0.05 and 0.7 under T5 and T6 heat treatments were studied and crack propagation curves were modified by a crack deflection model. The research results show that the fatigue crack grows along the boundary of dendrite cells to cause a remarkable crack deflection. The fatigue crack propagation rate at r=0.05 is smaller than that at r=0.7 for both T5 and T6 heat treatments. The effect of heat treatment on the fatigue crack propagation rates cannot be seen. The fatigue crack propagation rates modified by the crack deflection model predict no change at r=0.7, while a remarkable increase of the fatigue crack propagation rates can be seen at r=0.05. It is more reasonable and accurate to use the effective stress intensity factors for Mode Ⅰand Ⅱ to describe the fatigue crack propagation rates when a crack deflection occurs.
出处
《工程力学》
EI
CSCD
北大核心
2011年第10期197-201,242,共6页
Engineering Mechanics
基金
辽宁教育科学基金项目(20060659)
关键词
A357铸造铝合金
疲劳裂纹扩展
裂纹偏折
断口
热处理
A357 casting aluminum alloy
fatigue crack propagation
crack deflection
fracture surface
heat treatment
