Modeling of machining of EB-PVD ceramic coatings using smoothed particle hydrodynamics method

In this work, an improved Smoothed Particle Hydrodynamics (SPH) based model for simulating the machining process of the thermal barrier coatings is presented. The columnar grain microstructure in the electron-beam physical vapor deposition (EB-PVD) coating is constructed. The Johnson-Holmquist 2 (JH-2) material model coupled with the Johnson-Holmquist plasticity damage model is used for the ceramic coating. The model validation is conducted by the comparison between the SPH model and qualitative agreement with experimental observation, and a quantitative agreement with the one-dimensional stress wave analytical model. In the SPH model, the cutting processing parameters, such as cutting depth, cutting speed, cutting tool's edge radius, rake angle on the cutting force, and temperature change are studied. The results show that the fracture of the columnar grains during the cutting process is done through deflection and fracture of the grains, followed by pushing against neighboring grains. Both the cutting force and temperature of the coating increase with cutting depth due to increased cutting work which is transferred to heat. The cutting forces from the SPH model at the stable stage are in excellent agreement with the fracture mechanics analytical solution. The cutting force and temperature increase are higher for a larger edge radius, due to increased friction between the cutting tool and coating. The SPH model result follows the same trend as the main cutting force calculated by the analytical expression. The SPH cutting model developed in this work can be used as a design tool to optimize the coating machining process.