疲劳裂纹残余应力与应力强度因子研究

EXPERIMENTAL RESEARCH ON RESIDUAL STRESS AND STRESS INTENSITY FACTOR FOR FATIGUE CRACK

聚碳酸酯紧凑拉伸试件的疲劳试验和光弹性试验表明，尽管是低应力疲劳问题，但随着裂纹的扩展在裂尖附近出现残余应力场。给出了与循环周次相对应的卸载残余应力场，从而揭示出闭合效应的存在并提出其度量准则。试验表明，闭合效应使得应力强度因子降低，因此原有应力强度因子理论计算式不再适用，对此提出了一种简便有效的修正方案。

Through the fatigue experiment on CT speciment made of polycarbonate and the photoelastic experiment conducted at the same time,the writers find that residual stress field is formed in the neighborhood of crack tip along with the growth of fatigue crack,through it is the problem of low stress fatigue.The unloading residual stress field is gave corresponding to the number of cycles in the neighborhood of crack tiP. Thus the existence of close effect is revealed and its measurement criterion is put forward.The result of the experiment shows that close effect will reduce the stress intensity factor.So the original theoretical calculating formula for stress intensity factor is no longer applicable. A simple and practical revised scheme is proposed.