在发动机实际运行过程中，曲轴所承受的载荷主要是弯曲/扭转复合载荷，弯曲疲劳破坏是曲轴失效的最常见形式。而在发动机输出功率较大、曲轴承受扭矩较大的情况下，扭转疲劳破坏则成为主要失效形式。因此无论是在产品开发阶段还是在生产检验阶段 ，都要求对曲轴的疲劳性能进行检验。
In the actual operation of the engine, the load on the crankshaft is mainly the bending / torsion composite load, bending fatigue failure is the most common form of crankshaft failure. However, when the engine output power is large and the crankshaft bears large torque, torsional fatigue failure becomes the main failure mode. Therefore, whether in the product development stage or in the production inspection stage, it is required to test the fatigue performance of crankshaft.