A new method to accurately obtain wrinkling limit diagram in NC bending process of thin-walled tube with large diameter under different loading paths

To obtain the wrinkling limit of thin-walled tube by the NC bending process analytically, a new method has been proposed. Firstly, an FE model using ABAQUS/Explicit is employed to simulate the complex forming process. Thus, the plastic deforming behavior and wrinkling mechanism for thin-walled tube with large diameter under different loading paths (with or without boosting device) has been investigated and the reasonable assumptions for analytical analysis have been obtained. Secondly, according to the above simulation, an analytical wrinkling prediction model based on an energy criterion is established to calculate the wrinkling limit. Thirdly, an exponential function has been used to compensate for the effects of boundary conditions on onset of wrinkling by comparing the analytical results with corresponding numerical results to make the final results closer to reality. Thus the winkling limit diagrams with band distribution features are calculated. The method proposed is more suitable to the evaluation of formability for complex sheet forming process concerning wrinkling.