A geometry-dependent model for void closure in hot metal forming

Abstract

During production of large metal workpieces, an internal presence of voids is usually observed. Such internal defects are generally closed up using hot metal forming processes, such as hot forging or hot rolling. Prediction models for void closure, associated with process simulation, are extremely powerful tools and might significantly support process design. However, there is at present a lack of accurate models being able to predict void closure according to industrial conditions, particularly in terms of void geometries. In this paper, an original model for void closure is presented, accounting for the void׳s geometry and orientation, as well as the mechanical state during deformation. The model is build and calibrated based on a wide campaign of finite element simulations at the scale of a representative volume element. Various void geometries are defined and several mechanical states are prescribed on a range that is representative of industrial loadings. The model׳s accuracy is verified using industrial data and was compared to several models from literature. Great advantages are obtained for non-spherical voids in terms of void volume evolution.