Study On Texture Effect To Dynamic Behavior Of Material Based On Crystal Plasticity Theory

Dynamic response performance of materials is one of the key issues in combat and structural protection design.Not only that,the dynamic mechanical property of materials is also increasingly concerned by the protection of space debris and transportation safety.It has more and more extensive research needs in the aerospace,energy and other fields.Results show that the dynamic response of materials under impact loading and complex deformation conditions is significantly different from that of low pressure and low strain rate loading.Based on the macroscopic constitutive model proposed by the mathematical induction,it cannot describe the dynamic behavior of the material under the impact loading,nor can it meet the ability of the engineering design to study the change of the mechanical properties caused by the microstructure change.New research methods are needed to develop.Molecular dynamics(MD)plays an important role in understanding the microscopic mechanisms and mechanisms that influence the dynamic strength of the material.However,since the calculated size and strain rate range are far from the true sample state,the calculated results of dynamic strength are different to the experiment.The dislocation dynamics method(DD)is still difficult to simulate the complex dislocation evolution in the material impact loading process.Due to the obvious gap between the macro-research requirements and the micro-simulation capability,it is urgent to develop a dynamic response description method between the micro and macro scales.On the basis of extensive research on various methods,this paper is used to simulate quasi-static the crystal plasticity theory of mechanical properties is a typical imperative research method between macro and micro,and has great potential for development.Because there is a clear gap between the macro and micro-simulation study of demand ability,the dynamic between the urgent need of the development of between micro and macro scale response description method,based on the extensive research on various methods,that is used to simulate polycrystalline materials quasi-static mechanical properties of crystal plasticity theory is an important research method of typical between macro with the micro,has great potential for development.Therefore,in this paper,the microcosmic deformation in the crystal plasticity theory is described more rationally for the shortcomings of classical crystal plasticity theory.The thermoelastic viscoplastic crystal plasticity theory,calculation method and corresponding program module are developed for the metal materials(FCC,BCC and HCP)under dynamic loading.The typical dynamic response of Al,Ta and Be materials was studied.The main research work and achievements include:1)Aiming at the deficiency of the classical crystal plasticity theory,the microscopic deformation characteristics of the material under dynamic loading are considered.The dislocation dynamic,strain hardening,crystal elastic deformation and twinning growth mode are described more reasonably.The plasticity theory,calculation method and corresponding program module of thermoelasticviscoplastic crystal with twinning under the dynamic loading of(FCC,BCC and HCP)metal materials are established.2)This model is used to simulate the change of the strength of Al,Be and Ta materials versus pressure under dynamic loading.The calculated results are in good agreement with the experimental results,especially under high pressure loading;the obtained strength is closer to the experimental results than the SG model.The texture evolution of Al,Be and Ta materials under different loading pressure was studied.It is found that even if only one direction can be deformed,the texture of the material in the early stage of impact loading will change obviously,that is,the preferred orientation phenomenon.3)The effects of twinning on the strength and texture evolution of Ta and Be were compared.It is noted that the effect of twinning on the mechanical strength of Ta and Be is not the same under high strain rate loading.Twinning is more sensitive to the strength and texture evolution of the Be material.Twinning is an important physical mechanism of plastic deformation of Be under impact loading.4)In addition to using the crystal plasticity theory to study the mechanism of dynamic strength of materials,this paper also studies the quasi-elastic unloading problem which often appears in the impact dynamics but has not been well explained.The quasi-elastic process of Al,Ta and Be materials in shock-releasing is reproduced accurately by the crystal plastic theory combined with the finite element program.It is considered that the change of shear wave velocity with shear strain(Bauschinger effect)is the important reason for the quasi-elastic unloading of the material.