Elastoplastic Mechanical Properties Of Nanoporous Materials With Interface Effect

For many years,the research and development,preparation and properties of nanocomposites have attracted the attention of scholars at home and abroad.The interface effect at nanometer scale has an important influence on the macro mechanical properties of nanocomposites.In this paper,the micromechanics and finite element numerical simulation are used to study the macro and micro elastic-plastic behavior of nanoporous materials with interface effect,and the influence of interface residual stress,pore size and porosity on the elastic-plastic mechanical properties of nanoporous materials is analyzed.The work done is as follows:(1)In this paper,the second-order micromechanical model of stress moment is given by using Hill theorem and field disturbance theory combined with Mori-Tanaka method.The elastic-plastic mechanical properties of nanoporous materials with interface effect are studied.In view of the interface effect of nanospherical pores,the influence of interface residual stress,porosity and pore size of nanospherical pores on the effective elastic parameters of materials is analyzed by micromechanical model.The results show that the interface residual stress,porosity and pore size have an obvious effect on the elastic modulus and yield strength of the nanoporous materials,and the smaller the characteristic size of the nanoporous materials is,the more obvious the effect is,and it is the first time to find that the interfacial elasticity will soften the nanoporous materials.(2)Based on the constitutive relation of nanoporous interface effect,the mathematical interface without thickness is replaced by the interface phase model with thickness.The UMAT subroutine was developed.The finite element method was used to calculate the elastic-plastic stress-strain curves of the nanoporous materials with a single hole by using the subroutine and ABAQUS software.When the size of the nano-size void is smaller,the interface effect is more obvious,and the residual stress,porosity and pore size of the interface are more important to the nanoporous materials The greater the influence of elastic modulus and yield strength of porous materials,the more accurate and effective the theoretical model is.(3)In view of the closed cell porous aluminum,the developed model is used to analyze the nanoporous aluminum considering the interface effect.Through the micromechanical method,the elastic-plastic mechanical properties of the closed cell nanoporous materials with different spherical holes are studied.The effects of the interface residual stress,porosity and pore size on the macro elastic-plastic mechanical behavior of the nanoporous materials are mainly considered.It is found that the influence of interface residual stress,porosity and pore size on the elastic modulus and yield strength of the nanoporous materials is similar to that of the nanoporous materials with only one pore when the size ratio of different spherical pores is kept constant.When the size ratio of different spherical pores is different,the influence of interface residual stress,porosity and pore size on the elastic modulus and yield of the nanoporous materials is similar.The effect of clothing strength is different from that with only one hole.The results provide theoretical basis and reference for understanding the influence mechanism of interface residual stress and pore microstructure on the macro and micro elastic-plastic mechanical behavior of nanoporous materials and for the structural design and performance evaluation of the materials.