involute flank

例句：

1. 1. The car's involute flank is designed to absorb impact.
   这辆车的内凹侧面设计用来吸收冲击。
2. 2.The engineer used a special tool to remove the involute flank.
   工程师使用一种特殊的工具来去除内凹侧面。
3. 3.The involute flank of the machine is crucial for its operation.
   机器的内凹侧面对其运行至关重要。