循环塑性与疲劳裂纹扩展门槛值

基于材料的循环塑性预测了疲劳裂纹扩展的门槛值.所提出的模型强调材料的循环塑性对疲劳裂纹扩展的影响.结合无位错区理论和内聚区理论计算循环载荷下裂纹吸附区的J积分值,并以J积分作为断裂参数建立裂纹扩展的标准.由此计算的疲劳裂纹扩展速率符合通常的模式,预测的门槛值与实验拟合较好.当前模型的主要特点是近门槛疲劳主要由材料的循环变形行为确定,进而由标准循环加载的实验确定,这对于工程实际有重要意义.

Cyclic plasticity and fatigue crack growth threshold

Fatigue crack growth threshold is predicted based on material's cyclic plasticity. The model proposed emphasizes the influence of material's cyclic plasticity on fatigue crack growth. The value of J-integral within cohesive zone under cyclic loading is determined based on dislocation-free zone (DFZ) and cohesive zone theory. Then, the value of J-integral is regarded as fracture parameter and a criterion of crack growth is set up. The calculated curve of fatigue crack growth rate is in agreement with the general propagation pattern and the predicted threshold accords with the experiment threshold well. A prominent character of the present model is that the near threshold characteristics are most determined by the cyclic deformation behavior of the material, and are theoretically determinable from the standard cyclic loading test. This study should be of practical importance in engineering design.