The analytical model of crimping springback for large-diameter longitudinal welded pipe

Abstract The crimping technique is widely used in the manufacturing process of large-diameter longitudinal welded pipe. In the bending process, the springback is the critical problem affecting the shape, which is the key index of forming quality. So, crimping faces more challenges in accurate springback prediction for difficult-to-form metals such as pipeline steels and non-circular nature of the punch. This paper has established an analytical model of crimping springback for the longitudinal welded pipe. Firstly, the crimping process mathematical model which considered the impact of elastic modulus attenuation on springback calculation during plastic deformation is established, and the cross-section bending moment is calculated based on Hill’s bending theory. Secondly, a semi-analytical and semi-numerical method for calculating the crimping shape is presented. Finally, the comparison of the crimping shape of the real product shows that the calculation accuracy and efficiency of this method can meet the requirements of engineering applications. The relative error of the springback angle calculated by the analytical model is −5.84%, and the absolute error is 0.3°. This method can accurately predict the springback of longitudinal welded pipe after crimping and provide a reference for crimping process optimization.