Springback Analysis of Thin-Walled Stainless Steel Bellow in Hydroforming

Springback has an important influence on the forming quality of thin-walled stainless bellows hydroforming. By developing a FE model, the stress distribution is investigated and springback characteristics of two specification bellows are addressed. The results show that: (1) For tube Φ26×0.5, the maximum circumferential tensile/compressive stresses decrease by 32% and 29.1% after springback, respectively. The maximum longitudinal tensile/compressive stresses decrease by 51.8% and 39.6%, respectively. (2) Three indices are proposed to describe the bellow profile change after springback, namely, radial displacement of crown point; axial displacement of inner point; maximum convolution width. (3) For tube Φ26×0.1, after springback, the inward shrinkage of crown point increases by 0.7%, the bellow axial elongation is 0.76mm, the maximum convolution width increases by 30.3%.