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A persistent problem with computer simulations of forming processes is a general lack of experimental verification. A project was undertaken to simulate the two-stage, aluminum tube hydroforming of a structural tee shape, and perform simultaneous experiments for comparison. The simulations, performed with the code LS-DYNA, were used to establish the initial process parameters and also to predict the shape and thickness profile of the final part. The simulations compared favorably to the experiments, and the results are presented.

An evolutionary state variable model is used to predict failure in sheet forming. The development of damage in aluminum sheet is characterized using Bammann's plasticity model. Simulations are carried out with the commercial code LS-Dyna3D. Using the limiting dome height test as an example, the prediction of failure in straining states of draw, plane strain, and stretch is made for AA 6111-T4 sheet. The location of failure and associated major/minor strains are contrasted with experimental forming limit curves. As a further example, the drawing of a square cup from a 5000 series alloy blank is simulated and compared with experimental data. The simulations accurately predict the location of failure and show limit strains which compare favorably with experiment. The damage variable provides a method for predicting the location and time of failure in a framework that accommodates general straining paths.