Chapter 19. Thermal-Mechanical Stress Analysis of a PSZ Coated Piston Through Finite Element Technique

Summary

Application of thermal barrier coating on diesel engine pistons and its effect on the piston temperature, stress distribution, heat transfer and interfacial crack growth is investigated. A gas dynamic engine cycle simulation code was used to obtain the boundary conditions on the piston required for the thermal analysis. Using ANSYS, a 2-D axisymmetric Finite Element Analysis (FEA) was performed to evaluate the temperature, stress distributions and heat transfer rate in the piston as a function of coating thickness. In addition, fracture studies of an interfacial crack propagation using critical energy release rate criterion were carried out. Seven different coating thicknesses including 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, and 2.0 mm were investigated. The results indicate increased piston surface temperature with increasing coating thickness. The maximum stress on the coated piston surface was high while the substrate stress was less than the yield strength of the coating, for all coating thicknesses. Further, the analysis showed that the interfacial energy release rate for all coatings, is below the critical value and hence no separation of the coating is expected. Based on thermal stress analysis, the FEA results suggest an optimum coating thickness of 0.1 to 1.5 mm for diesel engine application to avoid unduly high stress in the ceramic. However, a fracture analysis study of the suggested coating range showed the optimum coating thickness to be 1.5 mm.