Crystal Plasticity Constitutive Model With Damage And Size Effect And Finite Element Implementation

Metal is commonly used in construction materials,and the mechanics performance prediction of metal material is an important subject.A large number of experiments have shown that the material mechanical performance is closely related with micro-meso structure.Compared with the traditional constitutive model,the crystal plasticity constitutive based on dislocation slip theory can better reflect the grain orientation sensitivity of plastic deformation and material damage fracture mechanics behavior and also can reflect the material mechanics performance caused by the change of grain size.Based on the framework of classical crystal plasticity constitutive,the coupling effect of damage and grain size is introduced.The mechanical property of face-centered cubic AL-0.63%Cu alloy and the rationality of the proposed mechanical constitutive are verified by comparing the results of crystal plasticity finite element simulation and mechanics experiment.The main research contents are as follows:1.Based on the crystal plasticity theory and the framework of FCC crystal constitutive model proposed by Abdul-Latif A,an improved crystal plasticity constitutive model with coupling effect of damage and grain size is introduced.The micro-damage,grain size effect,isotropic hardening,kinematic hardening caused by back stress,and the change caused by micro structure are considered in this FCC metal constitutive model.The feasibility of the proposed constitutive model is confirmed by the comparing between Simulation results and corresponding experimental results.2.The kinematics formula,incremental formula,integral algorithm and Jacobi matrix of the proposed constitutive model are deduced,which providing theoretical basis for finite element implementation.3.Based on the theory of Voronoi diagram,polycrystalline finite element model is established by the use of Python language and the mixed programming method of MATLAB and ABAQUS.Grain orientation is given by miller index method;post-processing is implemented by writing scripts.Every Unit core coordinates is calculated according to the characteristics of the unit number arrangement,simplifying the extraction process of unit information.4.User material subroutine UMAT of proposed crystal plasticity constitutive to ABAQUS is established by the use of Fortran language.And the material parameter is determined by comparing the experimental results.5.The mechanical properties of AL-0.63%Cu alloy,including the inhomogeneity of stress distribution,the effect of grain size and damage evolution are discussed.The results show that:The obvious inhomogeneity appears when material attains inelastic phase,because of the random distribution of the grain oriented.With the increase of strain,inhomogeneity has a decreasing trend after increase first.The cause of this phenomenon attribute to high stress unit has larger damage degradation effect.On the other hand,grain rotation reduce the differences of grain orientation when material deform.With the decrease of the grain size,the yield stress and fatigue life of material is increased.