温度/机械载荷作用下裂纹扩展的随机化分析

Randomization analysis of the thermal-mechanical crack growth

为描述温度/机械载荷共同作用下裂纹扩展速率,基于疲劳和蠕变裂纹扩展的线性叠加模型,给出了结合试验的修正方法.该方法根据试验结果提取新的材料参数,解决了原模型中由于交变载荷对蠕变裂纹扩展的影响所导致的材料参数不独立的问题.在此修正模型基础上,引入对数正态随机过程,建立了温度/机械载荷共同作用下的裂纹扩展随机模型,并采用泰勒级数展开法获得了指定裂纹长度下寿命分布和指定寿命下裂纹长度分布的表达式.通过算例比较随机模型和试验结果获得的寿命分布,证实了该随机化处理方法的可靠性.

In order to describe the crack growth law under thermal-mechanical loading, the linear superposition model of fatigue and creep crack growth was amended based on the experimental results. New material parameters in the model were determined, as the original ones may not be independent of the stress ratio, temperature and dwell time due to the influence of alternating load to the creep crack propagation. Then, a random crack growth model was obtained by introducing lognormal random process to the amended model. With the Taylor series expansion, the distribution of the crack size at any service time and the distribution of the service time to reach any crack size were attained. An example was given to validate the reliability of the proposed randomization method by comparing the life distribution obtained from the model with the experiment.