考虑应力梯度的缺口疲劳分散性研究

Investigation of notch fatigue dispersion considering stress gradient

针对缺口部位的微观结构及尺寸导致的疲劳分散差异较大的问题,为准确预测缺口件的疲劳分散性,以矩形截面缺口件为例,采用宏观Chaboche循环塑性本构模型与细观晶体循环塑性本构模型相结合的有限元子模型方法,并考虑缺口效应,提出了以应力梯度影响因子、等效应力与纵向应变为变量的统计标准差作为疲劳指示因子FIP_(notch)。在不同位移载荷、位移载荷比和缺口直径大小情况下将疲劳指示因子FIP_(notch)与经典的Fatemi-Socie疲劳指示因子FIP FS进行疲劳分散性的比较与分析。结果表明:疲劳指示因子FIP_(notch)均能很好地预测不同位移载荷、位移载荷比和缺口直径下的缺口疲劳分散性,且比经典的FIP FS方法有更高的精度与适用性。

Aiming at the problem that the microstructure and size of notch parts lead to large differences in fatigue dispersion,to accurately predict the fatigue dispersion of notch parts,taking notch parts with rectangular section as an example,the finite element submodel method combining macroscopic Chaboche cyclic plastic constitutive model and microscopic crystal cyclic plastic constitutive model was adopted,and considering the notch effect,the statistical standard deviation of stress gradient influence factor,equivalent stress and longitudinal strain as variables was proposed as the fatigue indicator parameter FIP_(notch).The fatigue dispersion of fatigue indicator paramter FIP_(notch) was compared and analyzed with the classical Fatemi-Socie fatigue indicator parameters FIP FS with different displacement loads,displacement load ratios and notch diameters.The results show that the notch fatigue dispersion can be well predicted by fatigue indicator parameter FIP_(notch) with different displacement load amplitudes,displacement load ratios and notch diameters and the accuracy and applicability are higher than that of the classical FIP FS method.