Residual stress and springback analysis for 304 stainless steel tubes in flexible-bending process

Flexible-bending is an innovative processing technique for profiles and tubes, which adjusts the curved shape of the forming part through numerical control. In this article, the flexible-bending forming precision of 304 stainless steel tubes was studied. The flexible-bending process of the tubes was simulated through finite element method in comparison with that of experiments. After the investigations of forming springback and residual stress, we conclude that regardless of changes in wall thickness or outer diameter, the residual stress decreases first and then increases following the increase of the ratio between outer diameter and wall thickness. Neither the wall thickening rate nor thinning rate is affected by wall thickness changes. The thrust of the pusher maintains stable during the bending process. The changes of both wall thickness and outer diameter affect the springback to some extents. When the radius of the target is constant, the springback can be optimized by adjusting the offset of the bending die and the distance between the guide and the die. The experiments agree well with the numerical simulations.