Simulation Of Aluminum Alloy Under Taylor Impact By Crystal Plastic Finite Element Method

The traditional macroscopic phenomenological constitutive model can only give empirical formulas by fitting the experimental data,which is difficult to explain the mechanism of internal structure change during material deformation.To study the relationship between microstructure and macroscopic deformation during material deformation,the constitutive model based on physical mechanism has attracted more and more researchers’ attention.Crystal plasticity theory is based on continuum mechanics.By decomposing the deformation gradient tensor,the slip and dislocation of the crystal in the material are related to its macro deformation.The physical mechanisms such as twins and phase transformation can be introduced to explain the physical essence of the deformation behavior of the material at the micro-scale.In recent years,with the development of the aviation industry,national defense technology,and other fields,the research demand for dynamic properties of materials is also increasing.Therefore,a cross-scale crystal plastic finite element method based on dislocation density is developed in this paper.The finite element numerical analysis of7075-T6 aluminum alloy under dynamic compression and Taylor impact is carried out respectively.The accuracy of the model is verified by comparing it with the experimental results,and the macro mechanical behavior and microstructure evolution during material deformation are analyzed.The main work of this paper is as follows:(1)This paper introduces the theory of the Taylor impact experiment and explains the relationship between the bullet profile after impact and the macro mechanical behavior during impact.The crystal plasticity theory based on dislocation density is deduced in detail,and the hardening model with dislocation density as the intermediate variable is established.The process of numerical solution through a user-defined subroutine in ABAQUS is introduced.(2)The effects of friction coefficient,dislocation multiplication,and annihilation coefficient on dynamic compression simulation results in crystal plastic finite element model are studied by controlling variable,the result shows that the influence of friction coefficient on the macro-mechanical properties in the simulation results can be ignored,and it only has a slight influence on the final cloud image display and the transverse displacement of the contact surface.The dislocation proliferation and annihilation coefficient will affect the hardening behavior and ultimate strength of the material.(3)The dynamic compression experiment of the 7075-T6 aluminum alloy cylinder sample was carried out.The microstructure of the samples before and after the experiment was characterized by EBSD,and the relevant parameters of 7075-T6 aluminum alloy in the crystal plasticity model were calibrated by comparing with the experimental results.The numerical results were compared with experimental,it shows that the crystal plasticity model used in this paper can accurately predict the mechanical behavior and microstructure changes of the 7075-T6 aluminum alloy during dynamic compression.Both of them show that more Brass {110}<112> texture and Goss {110}<001> texture are generated,but the prediction of texture volume fraction by simulation results is different from that by experiment.(4)Taylor impact tests at different speeds were carried out on 7075-T6 aluminum alloy cylinder buttles,and the corresponding crystal plastic finite element simulation was carried out.The result shows that the numerical calculation can accurately predict the contour of the sample after the Taylor impact.Through comparison,it can be seen that the prediction error of the simulation results for the diameter of impact face and the final length of the bullet after impact is less than 4%.With the impact velocity increasing,the volume fraction of Goss{110}<001> texture,S {123} <634> texture and R-cube {012}<100> texture increases gradually,while the volume fraction of F {111} <112> texture and E {111}<110> texture decreases gradually due to the preferred rotation of crystal orientation in the material.