基于改进SWT模型的FGH96合金低周疲劳寿命预测

针对SWT（Smith-Watson-Topper）模型未考虑材料对平均应力影响的灵敏度以及忽略平均应力对材料塑性变形影响的问题，利用材料的屈服强度和抗拉强度，对Walker指数γ的计算公式进行了改进，并将其引入到SWT模型中对损伤控制参数进行了修正。同时结合M-H（Manson-Halford）模型塑性部分平均应力修正方法对SWT模型中的塑性变形参数进行了修正，从而提出了一种基于改进SWT模型的FGH96粉末高温合金低周疲劳寿命预测方法。利用不同材料的γ试验计算值对改进的Walker指数计算方法进行了验证，计算平均相对误差为10.25%。并利用FGH96合金和其他航空发动机材料的低周疲劳试验数据，对改进SWT模型的寿命预测精度及适用范围进行了评估，并与M-H、SWT和Lv模型进行了对比。结果表明，改进SWT模型对不同材料的预测结果基本位于±2倍分散带之内，其寿命预测能力要高于其他3种模型。

Low cycle fatigue life prediction of FGH96 alloy based on modified SWT model

To solve the problems that Smith-Watson-Topper (SWT) model does not consider the sensitivity of material to the mean stress and ignores the effect of the mean stress on plastic deformation, we improved the computing method of the Walker exponent γ based on the yield strength and tensile strength, and modified the damage control parameter of the SWT model using the improved Walker exponent. Meanwhile, based on the Manson-Halford (M-H) model, the plastic deformation parameter of the SWT model was modified with the mean stress. Then an Low Cycle Fatigue (LCF) life prediction method for the FGH96 powder metallurgy superalloy was proposed based on the improved SWT model. The improved computing method of the Walker exponent was verified using the experimental calculation values of different materials, and the average relative error of calculation is 10.25%. The experimental data of the FGH96 alloy and other aero-engine materials show that the improved SWT model can provide better prediction than the M-H, SWT and Lv models, with nearly all the predicted results within ±2 times the scatter band.