The Study Of Material Constitutive Model For Cast Steel Considering The Effect Of Damage Accumulation

As for the theory of damage mechanism,the change of the material microstructure of the material would produce the damage such as microcrack and microvoid due to external load.The damage accumulation of the material will further lead to the deterioration of the mechanical behavior of the material.It is shown that the elastic modulus and yield strength will decrease and finally the material will fail.Therefore,it is very significant to investigate the influence of damage accumulation on the material behavior under cyclic loading.It is necessary to build a finer material constitutive model considering the damage accumulation effect when the analysis of the structure behavior is conducted.In order to study the influence of the effect of damage accumulation on the mechanical behavior of material under cyclic loading,a new damage model considering the influence of the equivalent plastic strain increment on the stiffness and strength of the material in the hardening stage is put forward.Then a material constitutive model considering the effect of damage accumulation is built in the paper.Based on ABAQUS software platform,a user subroutine VUMAT is compiled to define the mechanical constitutive behavior of the material.By calling the user subroutine the proposed material constitutive model can be used in the finite element analysis.Comparisons between the numerical results and experimental results are made to verify the correctness of the user subroutine and the suitability of the material constitutive model.Based on the OpenSEES software platform,fiber beam element and Hysteretic Material constitutive model are used to simulate the hysteretic test of steel under cyclic loading.And the suggested values of the damage factors due to ductility and energy in the Hysteretic Material constitutive model are given.Finally,through the cyclic test of cast steel,the damage coefficients are measured.The material constitutive model of cast steel considering the effect of damage accumulation is proposed.Based on the study of the theory and the experiment of steel and cast steel material,the implement method of the material constitutive model considering the effect of damage accumulation is proposed.The following conclusions would be drawn in this paper.1)A new damage model is proposed considering the influence of the equivalent plastic strain increment on the stiffness and strength of the material in the hardening stage.It's more accord with the reality of the damage accumulation.2)The material constitutive model considering the effect of damage accumulation is proposed when the improved damage variable D is introduced into the elastoplastic constitutive model to reduce the elastic modulus and the yield strength of the material in this paper.The suitability of the material constitutive model is well through verifying.The damage accumulation effect of the mechanical behaviors of material could be reflected by the user material subroutine.3)The cyclic test of cast steel is conducted.The hysteretic curves of the specimens are all plump which means the energy dissipation capacity of the cast steel material is well.The damage coefficients?,?₁ and?₂ of cast steel are 0.0051,0.1248 and 0.2562.The material constitutive model of cast steel considering the effect of damage accumulation is proposed,and the error of the ultimate tensile stress between numerical results from the proposed material constitutive model and the experimental results is less than 10%.