Study On Cutting Adiabatic Shear Behavior Based On Anisotropic Constitutive Model

Aluminium alloys are the most widely used in their category,with diverse industrial applications in the fields of aviation,aerospace,automobiles,and chemical manufacturing.This is mainly owing to their excellent properties,such as high specific strength,high specific stiffness,low density,high-temperature resistance and fatigue resistance.The aerospace monolithic structure has the characteristics of thin-walled large size,high material removal rate,weak rigidity and easy deformation.Its cutting quality is not only affected by cutting parameters,tool materials,structure parameters,but also deeply affected by its own properties.After the various rolling and preforming processes,in particular,the material texture characteristics render the anisotropy more obvious,which will affect its cutting performance in the high-speed machining process.It is of great significance to study the machining mechanism and mechanical properties of anisotropic materials for obtaining the optimal machining process.In this paper,the aerospace aluminum alloy 7050-T7451 pre-streched plate is used as the research material.Select the space angle γ which are 0o,30o,45o,60o,90o with TD-RD plane,using the Hopkinson compression bar experiment,the dynamic impact compression experiments under different loading conditions(strain rate,strain,temperature and forming angle)were carried out to analyze the change rule of mechanical properties.Based on the theory of elasticity and the transformation of the three-dimensional space coordinate system,combined with the projection relationship of the Cauchy stress tensor of an arbitrary section,the transformation relationship of the elastic modulus,shear modulus,and stress-strain between the orthogonal and load coordinate systems is obtained.The orthotropic Johnson-Cook(JC)constitutive model of AA7050-T7451 aluminum alloy is modified by fitting,and the constitutive relationship at any spatial angle is theoretically calculated by combining the obtained spatial coordinate transformation matrix.The generated spatial constitutive model is verified and modified through experiments and the impact compression finite element simulations by DEFORM software.The high-speed orthogonal cutting experiments with different cutting speed and feed speed were carried out on the anisotropic samples.Based on the Oxley orthogonal cutting theory,the change laws of cutting angle,cutting force,cutting temperature and chip shape under different cutting parameters and space angles are studied.The influence of cutting parameters and anisotropy on adiabatic shear and adiabatic shear sensitivity is analyzed by ultra depth of field microscope and metallographic microscope.Combining with high-speed cutting experimental data and material constitutive equation,the JC cutting constitutive equation for high-speed machining is constructed by cutting reverse method.Based on the modified JC cutting constitutive equation,the simulation model of high-speed orthogonal cutting under different conditions is simulated by using Advant Edge FEM finite element simulation software.The parameters of cutting force,cutting temperature,flow stress and chip shape in the deformation zone are analyzed.The accuracy of constitutive model and the influence of anisotropy on the cutting process are compared and verified.Based on the finite element analysis of the cutting mechanical parameters in the deformation area,the formation mechanism of serrated chips is studied in depth.Adiabatic shear sensitivity of the material is quantitatively characterized by the thermoplastic shear wave propagation theory,and the adiabatic shear critical judgment with anisotropic characteristics is obtained.The material cutting constitutive model is used to accurately predict the cutting performance and chip deformation behavior,so as to provide data and application support for better high-speed cutting of anisotropic materials.