Cyclic Plasticity Constitutive Model Of TRIP Duplex Stainless Steel Based On Mechanical Prop-erties Of Microscopic Different Phases

Finite element numerical simulation is a key method for analyzing material forming problems.Using constitutive models that accurately reflect material mechanical properties in finite element calculation models is an important factor to achieve accurate simulation of the forming process.For TRIP(Transformation induced plasticity)duplex stainless steel,deformation induced martensitic transformation has an important impact on material mechanical properties.Therefore,it is necessary to include the effect of martensitic transformation in constitutive models to achieve accurate simulation and prediction of the forming process.A cyclic plasticity constitutive model for TRIP duplex stainless steel considering deformation induced martensitic transformation was established from the perspective of mechanical properties of microscopic different phases.And the preliminary application of the cyclic plasticity constitutive model was studied.The load-displacement curves of microscopic different phases in TRIP duplex stainless steel were obtained through the nanoindentation experiment.Through the theoretical derivation,the stress-strain expressions of microscopic different phases were obtained,and the mixed hardening constitutive models of microscopic different phases under uniaxial tension and cyclic loading were established by using the mixed hardening criterion.Using a combination of Fisher FMP30 ferrite content detector and INSTRON 8801 hydraulic servo fatigue testing machine,the martensitic transformation content of uniaxial tensile and various strain amplitudes under cyclic steady state was measured.And the kinetics models of martensitic transformation under uniaxial tensile and cyclic steady state based on the O-C model were established,respectively.The constitutive models of TRIP duplex stainless steel under uniaxial tensile and cyclic loading were established by using the rule of mixture,introducing the mixed hardening constitutive models of microscopic different phases,strain partition model,and the kinetic model of martensitic transformation.Based on the UMAT interface principle and programming rules of ABAQUS finite element analysis software,as well as the theoretical foundations of discretization of constitutive models,plastic multipliers,and Jacobi matrices,UMAT subroutines for the constitutive models of experimental steel under uniaxial tension and cyclic loading were designed and programmed,respectively.The finite element analysis model for deep drawing experiment was established by using the UMAT subroutines of cyclic plasticity constitutive model,and the deep drawing experiment of TRIP duplex stainless steel sheet was designed.Through the finite element simulation and experimental measurement,the horizontal distance of the representative points and the sheet thickness data at key positions were compared with the experimental results.The comparison shows that the simulation results exist good accuracy,and the established cyclic plasticity constitutive model based on the mechanical properties of microscopic different phases was verified.Based on the established constitutive model in this study,the accurate prediction of the forming process of TRIP duplex stainless steel can be achieved.The established constitutive model can be applied to industrial production,as well as providing technical support and theoretical basis for solving practical production forming problems.