Thermo-Viscoplastic Modeling of Machining Process Using a Mixed Finite Element Method

This paper considers a thermo-viscoplastic model of the steady state orthogonal machining process by using a three-field mixed finite element method based on the Hu-Washizu variational principle. Assuming a trial chip geometry, work and tool material properties, and cutting conditions (cutting speed, feed rate and rake angle), detailed information on the state of the stresses, deformation, and temperature distributions in the workpiece and tool are obtained. This approach is shown to satisfy the nontrivial stress boundary condition better than the machining model that is based on the compatible displacement finite element method. The heat generated due to the plastic deformation, to the friction, and the heat conducted into the tool are calculated. The effects of the heat conduction and friction on the temperature field are studied. The isothermal machining case is also considered to study the thermal effect on the machining process. Numerical results are given for the aluminum 6061 alloy and pure titanium under several cutting conditions.