So the piston end design must be improved in order to avoid edge damage and damage of axis perpendicularity due to uneven plastic deformation of the piston end surface.

• 为了避免活塞因端面不均衡塑性变形而导致端部边缘破损、端面与轴线垂直度破坏等情况发生，需要对活塞端部结构进行改进。