热障涂层二向应力状态分析与危险点预测

Prediction of dangerous point of thermal barrier coating by biaxial stress state analysis

热障涂层剥落是航空发动机热端部件失效的主要形式,研究热冲击环境下涂层的失效机制对提升发动机使用寿命具有重要意义。基于二维轴对称有限元模型、二向应力状态分析方法、唯像学和累积损伤理论建立了热障涂层危险点位置预测方法,阐明了热障涂层在热冲击环境下的失效机制。研究表明随氧化层厚度增加,陶瓷层内部轴向应力与剪切应力的峰值点沿余弦曲线的波峰向波谷方向移动;与传统应力分析方法相比,二向应力状态分析法得到的轴向应力与剪切应力峰值位置更加接近,有利于危险位置预测;基于唯象学寿命预测模型与疲劳累积理论相结合的方法,进一步确定出危险点位置在陶瓷层波峰至波谷轴向距离的3/10处,与实际陶瓷层内开裂的位置基本吻合,验证了危险点预测方法的准确性。

The spallation life cycle of thermal barrier coat(TBC)is a key factor for failure in one operating period of the aircraft engine.Research on the thermal fatigue life(TFL)of TBC has great significance for prolonging the service life of engine.An effective failure analysis method for TBC is performed using biaxial stress state analysis,finite element method,phenomenology theory,and linear cumulative damage model.It is demonstrated that with the increase of thermally grown oxide layer thickness,the position of the maximum thermal stress moves from peak to valley along the cosine curve of the top coat.Comparing with the traditional stress analysis method,the biaxial stress state analysis method is more suitable to predict the accurate position of the risk point,because the position of the normal stress peak and shear stress peak calculated by biaxial stress state analysis method is closer to each other.Based on the phenomenology theory and linear cumulative damage model,the accurate position of the risk point is determined at 3/10 of the axial distance from the peak to valley of the top coat.The predicted position of risk point is basically consistent with the normal crack location inside the top layer of TBC,which can verify the accuracy of the failure analysis method proposed in this paper.