Research On Milling Force Modeling Of Hollow Thin-Walled Aluminum Alloy Structure

The hollow thin-walled aluminum alloy structure is an important part of the high-speed train body.In the process of its machining,the reinforcement plate is easily deformed under the action of milling force,which affects the machining accuracy and cutting stability,and even weakens the carrying capacity of the car body,endangering the safety of driving.Therefore,it is of great significance to study the milling force of hollow thin-walled aluminum alloy structure and to accurately predict it for deformation monitoring and improving product quality.In this paper,based on the constitutive model of workpiece material,the milling force prediction of hollow thin-walled aluminum alloy structure is carried out by analytical method,and the coupling analysis of milling force and machining deformation is carried out to modify the milling force model.The main research contents of this paper are as follows:(1)In order to describe the material flow characteristics of aluminum alloy 6005A at different strain rates,the parameters of Power Law(P-L)constitutive model were identified by parameter fitting method at medium and low strain rates.In the high strain rate stage,the P-L constitutive model parameters were identified by the combination of finite element technique,cutting test and genetic algorithm,and the identified P-L constitutive model parameters were verified by experiments.The results show that the P-L constitutive model identified by this method had high accuracy in predicting the milling force,chip shape and chip thickness.(2)Based on the principle of constant chip volume before and after plastic deformation,the instantaneous 3D geometry before and after chip deformation were characterized respectively,and the maximum chip thickness and instantaneous chip thickness after deformation were deduced.Then,the instantaneous shear angle model was established.The high strain rate P-L constitutive model and the unequal shear zone model were used to calculate the shear stress and shear force in the main shear zone.Based on the 3D bevel cutting theory,the milling force coefficient model of 6005A aluminum alloy was obtained.Based on the model,the milling force models of horizontal wall and left and right oblique walls were established and verified by experiments.The results show that the predicted results of the milling force model for horizontal wall and left-oblique wall were in good agreement with the experimental values,and the error is less than 10%.Due to the large elastic deformation of the right-oblique wall,the milling force error is between 20-30%.(3)In order to correct the milling force model of right-oblique wall,the direction of weak rigidity of hollow thin-walled aluminum alloy structure and the deformation position affecting the prediction accuracy of the milling force model were analyzed.The deformation prediction model based on finite element analysis was established to obtain the deformation data samples under different cutting conditions,and the FOA-CV-GRNN deformation prediction model was established by using deformation data samples.The prediction accuracy of machining deformation can reach R~2=0.9968.By analyzing the coupling process of milling force and machining deformation,an algorithm was proposed to solve the actual feed per tooth of right-oblique wall.Based on the calculation results of actual feed per tooth,the milling force model of right-oblique wall was modified and verified by experiments.The results show that the prediction error of the modified milling force model is less than 10%.