| High speed cutting (HSC) of titanium alloys is always one of the very complicated and urgent problems in aircraft, spacecraft and other related industries. This dissertation focuses on finite element simulation during hish-speed cutting Ti6Al4V alloy material. Theoretical analysis, numerical simulation and experimental verification are applied in this research. The major research works are included as follows:( 1 ) Commonly used thermal visco-plastic constitutive model are introuduced and analyed.According to their advantages and disadvantages and the characteristics of high speed cutting, the Johnson-Cook constitutive model are selected as the constitutive model of finite element simulation during high speed cutting .The Johnson-Cook constitutive model has two major problems by analysing existing literature and research results(2)Orthogonal cutting experiments and the finite element iterative method are used to modify the Johson-Cook constitutive model material constants under the conditions of large strains, high strain rate,which solve the problem that Johson-Cook material constants are not accurate caused by the limitations of the SHPB experiment(3)New Johson-Cook constitutive model is researched ,which inclucde the flow softening at high strain .Three modified material constitutive models are investigated as follows:modified material model with non-temperature-dependent parameters (MJC-1),modified material model with temperature-dependant parameters (MJC-2),modified material model with temperature-dependent parameters and strain softening (MJC-3). The results show MJC-3 are the best than others in their accuracy in predicting the flow stress.Finally, single factor method is used to determine the parameters of MJC-3 constitutive model.(4)To simulate high speed orthogonal cutting of Ti6Al4V, a commercial finite element software (ABAQUS/Explicit) has been used .This FEM adopt Johnson-Cook model and the MJC-3 constitutive model and Johnson-Cook fracture criterion.(5)Finally, orthogonal cutting experiments of Ti6Al4V are carried out, cutting force, cutting temperature and Chip strain the simulation are compared with the experimental data and were found to be in close agreement. |
