IMPROVED MODELING OF METAL FORMING: BAUSCHINGER EFFECTS IN PLASTIC FLOW

THIS RESEARCH AND DEVELOPMENT CLOSES THE GAP IN AN IMPORTANT AREA OF SIMULATING MATERIAL BEHAVIOR. IN PARTICULAR, ANISOTROPIC MODELS OF THE BAUSCHINGER EFFECT HAVE BEEN NEGLECTED IN THE DEVELOPMENT OF CODES FOR SIMULATION OF VISCOPLASTIC BEHAVIOR IN SPITE OF ITS IMPORTANCE TO FORMING PHENOMENA. THE BAUSCHINGER EFFECT IS FUNDAMENTAL TO PROPER SIMULATION AND DESIGN OF MANY METAL FORMING OPERATIONS. THE WORK DEMONSTRATES THE FEASIBILITY OF IMPLEMENTING A NEW MODEL OF THE BAUSCHINGER EFFECT. THE NEW VISCOPLASTIC CONSTITUTIVE MODEL IS BASED ON WELL-ESTABLISHED INTERNAL VARIABLE REPRESENTATIONS OF NONLINEAR KINEMATIC HARDENING WHICH PROPERLY ACCOUNT FOR THE RATE AND TEMPERATURE DEPENDENCE, LARGE STRAIN KINEMATICS, AND SUITABLE CO-ROTATIONAL STRESS RATE. THE MODEL IS BEING IMPLEMENTED USING AN EXISTING LAGRANGIAN FINITE ELEMENT PACKAGE AND VERIFIED BY COMPARING SIMULATION PREDICTIONS WITH EXPERIMENTAL RESULTS FOR SEVERAL COMMON EXPERIMENTAL AND MANUFACTURING CONFIGURATIONS.