As one of the most critical components in the combustion chamber of diesel engines, pistons operate under high temperature and pressure conditions for extended periods, which increases the likelihood of failures such as thermal fatigue. This paper first utilizes finite element simulation to obtain the temperature and stress field distribution of an Al-Si alloy piston under actual engine conditions. The results indicate that the throat area of the piston is the most susceptible to fatigue failure. Based on this, accelerated thermal fatigue tests were conducted to study the influence of various experimental factors on piston life, as well as to analyze the weight of each factor. Results from macroscopic and microscopic analyses of cracks using a scanning electron microscope show that fatigue cracks originate at the interface between the aluminum matrix and the detached hard particles. The cracking at the piston throat exhibits clear characteristics of ductile fracture, which is the result of cumulative fatigue damage. Therefore, from the perspective of continuum damage mechanics, it is considered to characterize the equivalent stress using the average loading rate during the loading phase and the maximum axial temperature gradient, establishing an experimental life prediction model for Al-Si alloy pistons.

中文翻译：

---

怠停循环下Al-Si合金活塞加速热疲劳试验及寿命预测研究


活塞作为柴油机燃烧室中最关键的部件之一，在高温高压条件下长时间运行，这增加了热疲劳等故障的可能性。本文首先利用有限元仿真获得了 Al-Si 合金活塞在实际发动机条件下的温度和应力场分布。结果表明，活塞的喉部区域最容易受到疲劳破坏的影响。基于此，进行了加速热疲劳试验，以研究各种实验因素对活塞寿命的影响，并分析每个因素的重量。使用扫描电子显微镜对裂纹进行宏观和微观分析的结果表明，疲劳裂纹起源于铝基体和分离的硬颗粒之间的界面。活塞喉部的开裂表现出明显的韧性断裂特征，这是累积疲劳损伤的结果。因此，从连续损伤力学的角度出发，认为利用加载阶段的平均加载速率和最大轴向温度梯度来表征等效应力，建立了Al-Si合金活塞的实验寿命预测模型。