Spring Back and Secondary Yielding Analyses with Endochronic Constitutive Model
Huang Junping(1,2),Peng Xianghe(2),Qin Yi(3)
(1 Electromechanical Engineering, Chongqing Vocational College of Polytechnic, Chongqing 400037,China)
(2 Dept. Of Engineering Mechanics, Chongqing University, Chongqing 400030,China)
(3 DMEM, Strathclyde University, Glasgow, G1 1XJ, UK)

Abstract: A thermomechanically consistent constitutive model for finite elastopl astic deformation is established based on the simple mechanical model, and the material user subroutine, UMAT, is programmed for embedding in the commercial so ftware, ABAQUS, together with this new consistent 3-D constitutive model for la rge elastoplastic deformation and the corresponding numerical algorithm, where t he fundamental constraints of irreversible thermodynamics are satisfied and the energy stored in the residual microstress fields is taken into account. The spring back and secondary yielding of cylindrical billets in elastic tools during up setting and closed-die upsetting are analyzed. Comparison of the load-displace ment relationship between the computed and experimental measurement indicates that the experimental data are limited to 32% of the original height, three phases of plastic deformation in an upsetting phase when the load increases rapidly fill the onset of upsetting, then work-hardening occurs as plastic strain developed, and the third phase of load increases rapidly with increase of load-car rying area.
Keywords: finite deformation, elastoplasticity, constitutive model, upsetting, springback, secondary yield.