三轴应力约束下疲劳裂纹闭合分析

 在对D-B模型修正的基础上，考虑到用三轴应力约束的方法研究穿透裂纹厚度效应，对常幅载荷条件下疲劳裂纹闭合做了详细的分析，并建立了一个有效的分析模型。该模型与三维有限元结果、实验数据和其它模型作比较，结果显示出能很好地处理各种因素对疲劳裂纹闭合的影响；对常幅下裂纹扩展速率首次获得同种材料在不同厚度、应力比和载荷水平下的统一描述。

FATIGUE CRACK CLOSURE ANALYSIS UNDER TRIAXIAL STRESS CONSTRAINT

On the basis of the modified strip yield model for considering thickness effects and strain hardening, a fatigue crack closure analytical model is presented. The main objective is to study the influence of thickness on crack closure behavior. The tensile stresses on the plastic zone and the yield stress in compression are defined and found to be multiplied by a function in tension for considering the thickness and hardening effects and a factor in compression for considering material Bauschinger effect, respectively. A plastic constraint factor is correspondingly defined with the plastic zone length ratio in this model. Crack closure coefficients and crack opening stress ratios with different thicknesses and stress ratios are calculated and compared with some other results. It is noted that the relation between crack closure coefficients or crack opening stress ratios and plastic constraint factor α when stress ratio R is given can be determined by prescribed functions. Consequently, the crack growth rate under constant amplitude loading can be rewritten as a comprehensive equation with different thicknesses and stress ratios.