During the working process, it bears thermal and mechanical loads simultaneously, because of which it tends to crack and even break.
它在工作过程中，受到热负荷和机械负荷的共同作用，工况恶劣，容易产生裂纹而导致破坏。
2
The piston is the heart of diesel engine, because it interacts with the working fluid to perform the key step of converting thermal energy to mechanical energy.