Simulating Rotary Draw Bending and Tube Hydroforming

Tube hydroforming is currently an active area of development in the automotive industry on account of the advantages it offers in comparison to other manufacturing processes presently under use to produce similar components. The majority of hydroformed tubes must be pre-bent using some bending process. Rotary draw bending is one of the most commonly used tube bending processes, incorporating the use of a universal flexing mandrel and wiper die in case of thin tubes. Simulation of the rotary draw bending and subsequent tube hydroforming is an active area of development. These simulations help establish the feasibility of the hydroforming process for specific components and have the potential to reduce the number of forming trials required to standardize the process for production of a high quality hydroformed component. In addition, they provide a more accurate representation of the hydroformed component during analysis carried out for validating the component design when subject to in-service loads. In this paper, a method is developed for the simulation of rotary draw bending and subsequent tube hydroforming using ANSYS/LS-DYNA. This method employs two finite element models. The first of these is a parametric finite element model with more than 50 parameters used to simulate the rotary draw bending process. This model is created directly as an LS-Dyna input deck, using MATLAB. The second model, which includes the tube with the residual strains, stresses and thickness at the end of the rotary draw bending process, is used to model the tube hydroforming process. Numerical results are obtained for different tubes and can be used to predict feasibility of hydroforming of a specific tube to a given cross section, as well as to examine the residual tube strains and thicknesses at the end of the composite process.

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