Computer Modeling of Property-controlled Forging Process for Heavy Forgings

Abstract

A numerical simulation method is presented to evaluate the controlling issues of property for heavy forgings such as the evolvement of void defect and the evolution of microstructure. In order to reveal the multi-scale effect of macroscopic plastic deformation as well as the stress state on the volumetric evolvement of tiny voids stochastically distributed in the forgings,a model calculating the void volumetric change through macroscopic stress and strain field is investigated by using a representative volume element model. By integrating the model with finite element method,with the void fraction is assumed,the void volume evolvement at each element can be evaluated simultaneously with the simulation of forging process. So it can be used to assess the degree of void closure for the forging materials with shrinkage cavity and porosity. For the simulation of microstructure evolution,a cellular automata modeling is investigated and applied to a rotor steel. According to the micro-and macroscopic relationship among "strain,dislocation density,dynamic recrystallization and flow stress",the dynamic recrystallization process is simulated and the R-grain size and kinetics percentage are obtained. By combining these property-related models with thermo-mechanical finite element method,the numerical technique is established to simulate the forging process and predict the deformed shape and evolution of void defect and grain size. Besides that,according to the features of incremental forming typically used for heavy forgings,a fast finite element method is developed by using rigid degree of freedom condensation technique. This method is an effective tool for simulating and optimizing the forming process.