Study On Dynamic Plastic Constitutive Relationship Suitable For High Speed Cutting Process

Finite element simulation has become one of the main methods to study the metal cutting with the development of computer technology and finite element method.However,the effectiveness and reliability of the finite element model depend on whether the constitutive model can accurately reflect the deformation behavior of materials in metal cutting.Metal cutting has the characteristics of "three high",namely large strain,high strain rate,and high temperature compared with other deformation processes.An accurate constitutive model that can be used in the finite element simulation of metal cutting is difficult to obtain because of the limitation of the strain rate ranges depends on experimental equipment.Moreover,the existing constitutive models can not simulate the serrated chips well.Therefore,the constitutive models suitable for high speed cutting need to be established.Therefore,the dynamic plastic constitutive relationships of materials for high speed cutting process are studied by taking AISI1045 steel and Ti6Al4 V titanium alloy as examples in this paper.The research contents are as follows:(1)The orthogonal cutting experiments are carried out,and initial Johnson-Cook constitutive model parameters which used to reverse process are selected.The orthogonal cutting experiments of AISI1045 and Ti6Al4 V titanium alloy are carried out.The finite element model of metal cutting based on existing constitutive models are established by ABAQUS.The initial constitutive parameters of AISI1045 and Ti6Al4 V titanium alloy are selected by considering the strain rate ranges and the accuracy of simulation results of continuous chips.(2)The constitutive model parameters suitable for the cutting process are reversed.A method to analysis the influence constitutive model parameters based on grey correlation analysis is proposed.It is used to determine the parameters of the constitutive model that need to be reversed.Through the secondary development of the ABAQUS scripts based on Python,the finite element model for the two-dimensional cutting simulation is established to realize automatic iteration of the constitutive model parameters.The constitutive model parameters suitable for the cutting process of AISI1045 and Ti6Al4 V titanium alloy are obtained by the reverse method based on the initial constitutive model parameters.(3)A constitutive model considering damage is proposed and implemented by finite element method.The constitutive models based on strain energy damage are established and realized by the VUMAT subroutine.The finite element models of cutting simulation of AISI1045 steel and Ti6Al4 titanium alloy are established to verify the effectiveness of the subroutine built.(4)The simulations of serrated chips in high speed cutting are carried out.The serrated chips in high speed cutting were simulated by the finite element model based on strain energy damage.The effectiveness of the strain energy damage constitutive model in the simulation of serrated chips in high speed cutting is verified by comparing with experimental results.The finite element model of cutting simulation based on Johnson-Cook damage are also established.The superiority of the simulation model based on strain energy is analyzed by comparing the simulation results of serrated chips.