elbow piece的用法和样例：
例句
- Reattach the relief valve hose to the elbow in the bottom flange cover.
重新将安全阀软管接到底部法兰盖内的弯头上。 - In the previous works only the uniform wall-thickness elbows were studied.However, the elbow thickness is varied with the bending radius and ellipticity on the cross section.
以往对弯头的研究只考虑壁厚均匀不变的情况，但是实际上弯头的壁厚是沿着弯曲半径变化的，并且弯头的截面也具有一定的椭圆度。
