Evaluation of Thermal Barrier Coating in Fatigue Life for an Aluminum Alloy Piston with Considering Residual Stress

Nowadays, engine components are subjected to higher loads at elevated temperatures due to the increasing requirements regarding weight, performance, and exhaust gas emission. Thus, fatigue due to simultaneous thermal and mechanical loading became a determinant among the damage forms. The effect of a thermal barrier coating (TBC) on the thermal stress and fatigue life in a gasoline engine piston with considering stress gradient was studied. For this purpose, coupled thermo-mechanical analysis of a gasoline engine piston was performed. Then fatigue life of the component was predicted using a standard stress-life analysis and results were compared to the original piston. The results of finite element analysis (FEA) indicated that the stress and number of cycles to failure have the most critical values at the upper portion of piston pin and piston compression grooves. The obtained thermo-mechanical analysis results proved that the TBC system reduces the stress distribution in the piston by about 2.4 MPa and 8.5 MPa at engine speeds of 1000 rpm and 5000 rpm, respectively. The fatigue life results showed that the number of cycles of failure for the coated piston is approximately 12% and 31% higher than the original piston at engine speeds of 1000 rpm and 5000 rpm, respectively. To evaluate properly of results, stress analysis and fatigue life results is compared with experimental damaged piston and it has been shown that critical identified areas, match well with areas of failure in the experimental sample.