活塞的热疲劳性能对柴油发动机的全寿命至关重要。由于能量有限和可控性差等缺点,现有实验系统均不能满意地进行活塞热负荷模拟实验。为此,提出并建立了一套激光诱发活塞热负荷的实验系统。该系统通过对激光束的空间整形,使之投射到活塞表面后诱发的温度场分布满足特定要求。基于PROFIBUS-DP现场总线技术实现了系统集成和实验过程的全反馈控制。针对活塞的典型热负荷条件,即高周热疲劳和热冲击分别进行实验,以模拟正常工作循环和“启动-停车”等热负荷或转速突变工况。通过设置加热-冷却周期或上限-下限温度,可以获得相应的热负荷模拟实验效果。研究结果表明,采用经光束整形的激光进行活塞热负荷模拟实验具有周期短、可控性好等优点。

Thermal fatigue behavior of the piston is vital to the overall life-span of diesel engines. Up to now, none of the experimental systems in use can simulate thermal loadings on the piston satisfactorily, mainly due to the limitation of energy capacity and system controllability. In this paper, a novel laser-induced thermal loading system is proposed and built up to perform experimental investigations on pistons. The laser beam was spatially shaped into concentric multi-circular beams and irradiated on the top surface of the piston to induce desired temperature field. System integration and information feedback were accomplished based on process fieldbus-decentralized periphery (PROFIBUS-DP) protocol. Typical thermal loading tests, i.e., high cycle thermal fatigue test and thermal shock test were carried out to simulate thermal loadings in the normal working condition and “start-stop” condition with a sudden change of loading and speed, respectively. By setting up the heating time and cooling time, or the maximum temperature and minimum temperature in one thermal cycle, the thermal loading conditions were conveniently simulated. The results showed that the spatially shaped laser system can perform efficiently thermal loading simulation tests on pistons in a relative short time-span and controlled manner.