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 study work is focused on the effect of temperature upon mechanical properties, creep, initiation and propagation of fatigue crack for the valve material.
着重温度对气门材料的力学性能、蠕变和疲劳裂纹形成与扩张的影响等问题进行分析和研究。
3
Based on the analysis of crack and residual stress, mechanical property of Laser Rapid Forming sample is studied.