Analytical Modeling Of Hydroforming Pre-Bend Process: Without Inner Mandrel

The aim of this study is to develop an analytical solution to the deformation profile of hydroforming pre-bend process, which will be in turn fed into finite element simulation code for subsequent hydroforming simulation. The conventional approach of using FEM to simulate pre-bending is extremely time consuming in terms of both CAE work and computer running, and can not meet the cycle time required for product development and manufacturing. This is part of a series work for pre-bend modeling, with the focus here on the practice without the use of an inner mandrel, and the tube is free to ovalize during the process. Since only a portion of the tube is undergoing the bending operation, the ovalization magnitude of the tube cross-section is not longitudinally uniform due to the end constraints provided by the undeformed portion of the tube. A large deformation elastoplastic analysis is presented, with the anisotropic plastic behavior of the tube sheet accounted for through the constitutive model. Deformation modes associated with tube ovalization and beam bending are analyzed. The actual deformation is determined by minimizing the total work done during the bending process. Numerical examples are presented for a series of tube geometries and bending curvature to illustrate the proposed approach.