应力腐蚀损伤裂纹起始寿命计算模型

DAMAGE MECHANICS MODEL FOR THE INITIATION LIFE OF STRESS CORROSION CRACKING

应力腐蚀破裂的三个阶段中 (裂纹孕育期、裂纹扩展期、快断期 )孕育期的裂纹起始寿命约占总寿命的 90 % ,其分析估算的准确性对应力腐蚀总寿命的估算有决定性的意义。文中应用应力腐蚀损伤累积的概念 ,建立裂纹起始寿命计算的损伤模型 ,该模型考虑到应力与损伤的关系及应力腐蚀破裂的门槛值。以文献中光滑试件恒定应力应变腐蚀试验为算例 ,对不同初载荷作用下的应力腐蚀裂纹起始寿命进行计算 ,与试验结果对比有很好的一致性 。

The problem of stress corrosion cracking initiation has been studied on the base of continuum damage mechanics. The attack of load together with environment will weaken the materials, and the degree of the weakening can be described well by the damage variable used in damage mechanics. Just as the use of the damage mechanics in predicting the initiation life for creep and fatigue cracks, a stress-corrosion damage evolvement model, which has considered the roles of the threshold stress, effective stress and the existed damage, is established. And the effects of the environment corrosion are presented with the parameters in the evolvement model. Then a stress-corrosion crack initiation life model is deduced from the damage evolvement model with the concept of the damage accumulation. The initiation lives of the stress corrosion cracking have been predicted for two kinds of materials at different stress levels. The predicted results show a good agreement with the testing results.