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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.

This paper provides a preliminary study on tensile behavior and formability of some engineering magnesium and aluminum alloys, and steels at elevated temperatures (>0.6 Tm) and high strain rates (>0.1/s). A new elevated-temperature biaxial formability testing technique is developed to study strain path dependence as well as temperature and strain rate dependence. The formability test and in-die forming process are simulated with FEA method, and a concept of forming process diagram is established. The technical feasibility of elevated temperature gas forming for automotive components is discussed.

Aluminum alloy sheets of 2010-T4 of 0.831 mm and 2.590 mm thicknesses and 6111-T4 of 1.029 mm thickness were tested to determine the Forming Limit Diagrams (FLDs). The forming limit curves were obtained from both rolling and transverse samples. Due to the large scatter observed in the experimental data, exact identification of the forming limit based on incipient necking was not an easy task. Two alternate methods of determining the equivalent FLDs were explored and tested. The resulting forming limit curves based on the two methods are reasonably consistent with trends indicated by previous forming limit diagram determinations.

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.