Improving High Cycle Fatigue Life in A Gasoline Engine Piston using Oil Gallery with Considering Stress Gradient

Fatigue due to thermo-mechanical stresses plays an effective role in causing damage and reducing piston fatigue life. The effect of oil gallery on the thermal stress and High Cycle Fatigue (HCF) life in a gasoline engine piston using oil gallery with considering stress gradient was investigated. For this purpose, coupled thermo-mechanical analysis of a gasoline engine piston was carried out. Then HCF 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. The obtained thermo-mechanical analysis results proved that the oil gallery reduces the stress distribution in the piston about 7MPa and 12MPa at engine speed 100orpm and 500orpm, respectively. The results of high cycle fatigue life showed that the number of cycles of failure for modified piston is approximately 33% and 37% higher than original piston at 100orpm and 500orpm, respectively. To evaluate properly of results, stress analysis and high cycle fatigue results is compared with real sample of damaged piston and it has been shown that critical identified areas, match well with areas of failure in the real sample.