Numerical forming simulations and optimisation in advanced materials

With the introduction of new materials as high strength steels, metastable steels and fibre reinforced composites, the need for advanced physically valid constitutive models arises. In finite deformation problems constitutive relations are commonly formulated in terms the Cauchy stress as a function of the elastic Finger tensor and an objective rate of the Cauchy stress as a function of the rate of deformation tensor. For isotropic materials models this is rather straightforward, but for anisotropic material models, including elastic anisotropy as well as plastic anisotropy, this may lead to confusing formulations. It will be shown that it is more convenient to define the constitutive relations in terms of invariant tensors referred to the deformed metric. Experimental results are presented that show new combinations of strain rate and strain path sensitivity. An adaptive through- thickness integration scheme for plate elements is developed, which improves the accuracy of spring back prediction at minimal costs. A procedure is described to automatically compensate the CAD tool shape numerically to obtain the desired product shape. Forming processes need to be optimized for cost saving and product improvement. Until recently, a trial-and-error process in the factory primarily did this optimization. An optimisation strategy is proposed that assists an engineer to model an optimization problem that suits his needs, including an efficient algorithm for solving the problem.