应用幂变换法构造低周疲劳寿命预测的幂指函数模型

Power-exponent Function Model of Low-cycle Fatigue Life Prediction Based on Power Transformation Methods

以GH4049合金低周疲劳数据分析为例,以数据残差检验为基础,说明应用Manson-Coffin方程时普遍存在的问题。从塑性应变幅与疲劳失效反向数在双对数坐标系下的二次曲线特征及残差稳定化角度考虑,基于幂变换方法构造了低周疲劳寿命预测的幂指函数模型,来改善残差图性态及模型预测精度。给出了13种材料的幂变换指数p值及模型寿命预测能力对比结果。分析表明:幂指函数模型对低周疲劳寿命预测结果分散带均在2倍因子以内,具有良好的精度。Manson-Coffin方程实际是幂指函数模型在双对数坐标系下的一阶线性近似,这是幂指函数模型寿命预测精度较高的原因。

The paper explains the general problems in the use of Manson-Coffin equation according to residual tests of low-cycle fatigue （LCF） data of GH4049 superalloy. The analysis takes two points into account, namely conic characters of plastic strain amplitude vs. reversals to failure in log-log scale coordinates system and the residual stabilization. Based on power transformation methods, it advances a power-exponent function model for LCF life prediction with a better residual plot and life prediction precision. The investigation gives power transformation exponents p and model performances contrast results of some materials. The power-exponent function model presents better performances and precisions for LCF life prediction. In fact, Manson Coffin equation is the first order Taylor expansion approximation of powe-exponent function model in log-log scale coordinates system. It＇s the reason for a better precision of power-exponent function model in LCF life prediction.