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Description
In this research, a previously developed hot rolling simulation system, based on novel meshless computing technology, is upgraded from the pure plastic to a more realistic elasto-plastic material model that allows to cope with damage mechanics. This enables a more detailed virtual testing of different rolling schedules. Helmholtz free energy is used to structure damage coupled constitutive equations and stiffness matrix on the basis of irreversible thermodynamics. Both the elastic and the plastic parts contribute to the free energy. For the elastic part, initial elastic stiffness tensor changes into damaged elastic stiffness tensor and the plastic part of the free energy is added due to the strain hardening. Effective stress tensor is redefined with the inclusion of the damage tensor. Damage variables are initialized through the density of the micro voids inside the steel billet. Instead of fracture mechanics, a continuum damage mechanics is considered here to analyze the mechanical behavior of the rolled steel before the occurrence of any crack. Therefore, a damage tensor is calculated during the hot rolling simulation, which is obtained based on the current deformation state. A two dimensional slice model is considered in the simulations. These slices are aligned parallel to each other and perpendicular to the rolling direction. Therefore, the components of the damage tensor towards the rolling direction are neglected. The main improvement of the upgraded simulation system represents a more realistic material model that considers the initial processing history of the steel and reveals the damage effects throughout the simulation. This provides a good virtual estimation where and when to expect failure.