一种改进的Walker裂纹扩展方程

A Modified Walker′s Equation in Fatigue Crack Growth

线弹性断裂力学应用于疲劳裂纹扩展分析中,裂纹扩展速率一般可分成3个阶段,其中稳定扩展的第2阶段可以用Paris规律描述。目前提出的许多反映应力比影响的裂纹扩展方程基本上可以归结为Paris规律的形式,也就是把Paris公式参数C视为应力比R的函数,很少考虑参数n随应力比变化的情况。文中提出了一种改进的Walker裂纹扩展方程及其分析方法,建立了C、n和应力比R之间的关系,很好地描述了一种有机玻璃板材和一种低碳钢板材的疲劳裂纹扩展规律。

The form of Paris law,da/dN=C（△K）＇, is adopted by the majority of the fatigue crack growth （FCG） equations where n is considered constant and C varies with the load ratio R. However, there do exist the situations where n is dependent on the load ratio. In this investigation, a modified Walker＇s equation was developed in which C and n are both the functions of R and all the four parameters can be derived conveniently from the C and n values for three different load ratios including 0. The traditional Walker＇s equation is just a special case of the new equation. The effectiveness of the new equation has been validated, when using it in dealing with the FCG data of the YB-MD-3 Polymethylmethacrylate （PMMA） presented by us in Reference and those of the ASTM A516 Gr. 70 carbon low alloy steel given in Reference . As is the case for the traditional Walker＇s equation, the recommended equation may be applied separately to the positive and negative load ratios.