Study On Friction Modeling Of Tool-chip Interface During High Speed Cutting

With the advanced computational technology, Finite Element Modeling(FEM) is being used to optimize metal cutting processes and to investigate the state of stresses, strains, temperatures and cutting forces in the cutting zone. A better understanding of friction modeling and the effect of different cutting parameters is required in order to produce better FEM models to support the goals of longer tool life and better surface quality in machined products.The finite element software ABAQUS was used to establish the two-dimension orthogonal friction model with no separation line. The technology of the two-dimension model size, element mesh type and boundary condition constraint are discussed briefly. The material constitutive behavior is represented by Johnson-Cook constitutive model. Shear failure criterion is adopted as the separation criterion of material. In order to define the frictional condition in the tool-chip interface precisely, the user subroutine interface VFRIC is used to do the second development for tool-chip frictional interface, based on the build-in Coulomb friction model, establish the sticking-sliding friction model and the friction model of variable friction coefficient in sliding region.Meanwhile, this thesis obtained the chip root specimen of AISI1045through high-speed cutting experiment, to study the variation of chip morphology with the change of cutting speed and tool rake angle, and describe the morphology of adiabatic shear band in serrated chip and the slip line of grains in chip root briefly.Comparing the variation of cutting forces with the changing cutting parameters obtained from experiment and the three friction models, the results show the three friction models all can accurately simulate the varying tendency of cutting forces with the cutting parameters, which is the cutting forces reduce as the cutting speeds and the rake angle increase. But during the results, the friction model of variable friction coefficient in sliding region is better than the other friction models.The similar comparison is also made for the tool-chip contact length and shear angle of the experiment and three friction models. The tool-chip contact length decreases with the increase of cutting speed and rake angle, contrary to the law of shear angle. The analysis consequences also indicate the friction model of variable friction coefficient in sliding region can describe the frictional condition of tool-chip interface during high speed cutting more accurately. And we describe the distribution of strains within the cutting region and chip and stresses on tool-chip interface. The research finds the changing law of normal stress on tool-chip interface with the cutting speed and rake angle is same with that of tool-chip contact length, the equivalent plastic strain in chip is direct proportion to the cutting speed. And the equivalent plastic strain in shear band reduces from the maximum gradually.