Study on Fatigue life priduction of microstructural short crack region

本研究的一个目的是建立一种算法来估算无起裂寿命的裂纹扩展曲线。微结构短裂纹区的疲劳寿命必须估算如下。当缺口较深时，必须使用静态条件下的屈服应力来评估疲劳寿命。当缺口较小时，需要考虑循环载荷的影响，必须用循环条件下的屈服应力来评估疲劳寿命。物理小裂纹区和长裂纹区的疲劳寿命必须用da/dN-DELTAK&lt；Rp&gt；的对数曲线计算。因此，对缺口根部的裂纹扩展曲线进行了计算。而不区分裂纹的萌生和扩展。这一结果可用于建立统一的疲劳寿命评估理论，以取代线性断裂力学中的S-N曲线和裂纹扩展曲线。

It is that a purpose of this study establishes algorithm to estimate crack growth curve without initiation life. Fatigue life of microstructural short crack region must estimate it as follows. When a notch is deep, fatigue life must be evaluated using yield stress under static condition. When a notch is slight, effect of cyclic loading needs to be considered and fatigue life must be evaluated using yield stress under cyclic condition. Fatigue life of physically small crack region and a long crack region must be calculated using the logarithmic curve of da/dN-DELTAK_<RP>. Therefore, Crack growth curves are calculated for a crack emanating from a notch root. without distinguishing between crack initiation and propagation. This result can be considered in establishing a unified fatigue life assessment theory to replace the combined S-Ncurve and crack propagation curve of linear fracture mechanics.