陶瓷基复合材料疲劳寿命预测方法

Fatigue Life Prediction Method for Ceramic Matrix Composites

为了建立CMC疲劳寿命预测方法,推广CMC在航空发动机中的应用,根据BHE剪滞模型理论,分析了随着疲劳峰值应力的大小不同,CMC可能出现的4种疲劳迟滞行为,推导了每种迟滞行为下的循环应力-应变公式,模拟了给定应力条件下的疲劳迟滞回线,通过与试验数据对比,证明了迟滞回线模拟的准确性,进一步分析了界面剪应力随疲劳循环数的退化关系。结合界面剪应力退化模型与纤维强度退化模型,设计了纤维应力计算和疲劳寿命计算流程。针对2维编织CMC,根据单胞有限元计算结果提取了纤维束应力,并对CMC进行了疲劳寿命计算,推导了CMC疲劳寿命S-N曲线,其结果与试验数据基本吻合。针对2维编织CMC的疲劳寿命预测方法,可用于编织结构的CMC涡轮导叶疲劳寿命分析。

In order to establish fatigue life prediction method for Ceramic Matrix Composites and expand its application in aemengine, this work investigates that the CMC may appear four different kinds of fatigue hysteresis behavior under different peak fatigue stresses on the basis of the BHE shear lag model. The stress and strain formulas of cyclic curves under each kind of hysteretic behavior were deduced. By comparing with the experimental data, the accuracy of the hysteresis loop simulation was proved, and the degradation of the interfacial shear stress with the cyclic number was obtained. The failure criterion of the cyclic process was determined by combining the shear stress degradation model and the fiber strength degradation model, and a numerical method for calculating the stress and fatigue life of the fiber was designed. According to the results of finite element analysis of a 2D woven CMC, the stress of the fiber was extracted and the fatigue life of CMC was calculated. The S-N curve of fatigue life of CMC was deduced and the result was in agreement with the experimental data. The fatigue life prediction method for 2D woven CMC can be employed to fatigue life prediction of the woven CMC turbine vanes.