Experimental research and computational modeling of deformation processing

The numerical modeling of bulk forming is investigated. The modeling process is evaluated and improved using experimental data from simple axisymmetric and three-dimensional upset forming applications. A range of aspect ratios and reductions under medium and near sticking friction conditions is investigated.;The first portion of the research focuses measuring and predicting the internal plastic strains in bulk forming. The less computationally demanding application of axisymmetric upsetting is examined initially. Second-order elements are used to model the deforming material as well as the interface. Quasi-static, rate-sensitive, hybrid linear pressure, and coupled temperature-displacement constitutive models result in nearly identical strain predictions for the conditions investigated. Numerical modeling of the applications investigated is found to be very sensitive to the discretization. Guidelines are given for designing the initial mesh to improve the numerical model in terms of the quality of the result, the computational cost, and robustness. Very good agreement between the experimentally measured strains and the numerically predicted strains is observed. The tools developed for axisymmetric forming are extended to three-dimensional forming. Limitations in the current three-dimensional interface formulations require the use of linear elements. Reasonable results are obtained, but at much greater computational expense.;The second portion of the research is a detailed investigation into the modeling of the contact mechanics at the interface between a deforming aluminum billet and a hard steel platen. A sticking zone or region is observed at the center of this interface. The size of the zone is found to increase with the amount of friction and is proportional to the relative height of the billet. Similar behavior is observed in the numerical simulation, although the model underestimates the size of the sticking region in some cases. The influence of the slip limit on the sliding predicted by the model is investigated.