numerical simulation of orthogonal cutting process and determination of built up layer thickness

the built up layer thickness in secondary deformation zone is one of the important parameters in metal cutting process. the built up layer (bul) is formed in second deformation zone near the tool-chip interface in the back of the chip. this parameter influences the tool life and machined surface quality. this bul should not be confused with the built up edge (bue). the deformation of the bul in the secondary shear zone is a stable and continues process; leading to an uniform thickness of the bul along the chip's back but the deformation of the bue is an unstable process in front of the tool edge. numerical simulation is a suitable method for determination of temperature, stress and strain distribution in metal cutting since it dose not suffer the analytical methods limitations and experimental methods cost. in this paper a new method is presented to calculate the built up layer thickness in secondary deformation zone using finite element simulation of orthogonal metal cutting process. there are two main concepts about chip separation mechanisms from work piece, i. e. crack propagation and pour deformation without crack. in the present work chip formation process is assumed as a pour plastic deformation, considering second chip separation mechanism. there is no separation criterion in the simulations based on pour deformation, but adaptive remeshing is performed during simulation to avoid the difficulties associated with deformation-induced element distortion. an updated lagrangian finite element model of two-dimensional orthogonal cutting process is developed. this model is meshed using 4-node plain strain elements. thermo-mechanical coupled analysis, with adaptive remeshing is performed by ls-dyna finite element code. johnson-cook material model is used for determination of the work piece material flow stress and the cutting tool is assumed as a rigid body. an updated coulomb friction law is used to describe friction condition in tool-chip interface. the temperature and equivalent strain distribution diagrams in cutting zone are shown at various cutting speeds. the built up layer thickness in various cutting speed are also calculated by equivalent strain gradient in second deformation zone. the numerical calculated tool average temperatures and the built up layer thicknesses in various cutting speeds are compared with the experimental data given in literature and good agreement is observed between them.