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。