Identification Of Cutting Simulation Parameters Of 300M Steel And Research On Its Surface Quality In Turning

As a typical difficult-to-machine material, 300 M ultra high strength steel is widely used in production of aircraft landing gear, the problems in its cutting processes such as big cutting forces, high cutting temperature, and poor surface quality will bring risks to the safety performance of planes. In recent years, people have focused on the force and thermal characteristics in milling of 300 M steel, but paid little attention to the machinability and machined surface quality in turning 300 M steel. On the other hand, lack of core simulation parameters such as constitutive equation parameters and tool-chip friction coefficient limits the application of finite element method(FEM) in the cutting simulation of 300 M steel. Therefore, in this paper, the constitutive equation and friction coefficients of 300 M steel are obtained from cutting experiments, and the cutting forces, roughness and residual stress in cutting 300 M steel are studied with the method combining the experiments and FEM.First, through the combination of the moving heat source temperature model and the unequal primary shear zone(PSZ) model, the solution model of material Johnson-Cook(J-C) constitutive equation parameters was established. The J-C parameters of 300 M were obtained based on the cutting tests data and genetic algorithm, and the simulated cutting forces by the obtained material model turn out to be in great better agreement with experimental data than those by the model in FEM software.And, based on the cutting tests and FEM simulation data, the empirical relationship between the tool-chip friction coefficient and cutting parameters was established, so that the friction coefficient could be directly obtained by the given cutting parameters, which not only extended the model's applicable scope but also further improved the accuracy of simulated forces.Then, the influences of cutting parameters on three-dimensional cutting forces and surface roughness were investigated by the single factor experiments. Based on the multiple linear regression analysis of the orthogonal experiments, the empirical models of cutting forces and surface roughness associated with cutting parameters were established, and the significant tests and experimental verification of these models were carried out.At last, the principle stress was selected as the indicators of residual stress, and the influences of cutting parameters on residual principle stresses in turning 300 M steel were studied, and their empirical relationship was established. Then, the three-dimensional FEM model of cutting 300 M steel was established by using the obtained simulation parameters, and its effectiveness was proved by experiments data. Then the influences of cutting parameters on the residual stresses distribution along the depth in the workpiece surface layer were investigated, and the cutting parameters for getting the reasonable residual stress distribution were determined.The above researches obtain the constitutive equation parameters and tool-chip friction coefficients which are necessary for finite element simulations of cutting 300 M steels, and provide experiment and simulation basis for improving the machined surface quality of landing gear by optimization of cutting parameters.