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 More
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 1000rpm and 5000rpm, 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 1000rpm and 5000rpm, 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.
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The effect of perimeter fins on the thermal stress and High Cycle Fatigue (HCF) life in an exhaust manifold with considering stress gradient was investigated. For this purpose, coupled thermo-mechanical analysis of an exhaust manifold was carried out. Then HCF life of t More
The effect of perimeter fins on the thermal stress and High Cycle Fatigue (HCF) life in an exhaust manifold with considering stress gradient was investigated. For this purpose, coupled thermo-mechanical analysis of an exhaust manifold was carried out. Then HCF life of the component was predicted using a standard stress-life analysis and results were compared to the original exhaust manifold. Mechanical properties of exhaust manifold material were obtained by tensile tests at different temperature. The results of the thermo-mechanical analysis proved that the maximum temperature and stress are visible in the confluence region. The obtained Finite Element Analysis (FEA) proved the fact that perimeter fins reduce the temperature distribution in the exhaust manifolds about 31°C. As a result, the exhaust manifolds tolerate lower temperature and fatigue life will increase. The results of FEA indicated that the stress in the modified exhaust manifolds decreased approximately 19MPa for the sake of depletion of temperature gradient, which can lead to higher fatigue lifetime. The results of HCF showed that the number of cycles of failure for modified exhaust manifold is approximately 63% higher than the results obtained from the original exhaust manifolds. The results of the FEA analysis are compared with the real sample of the cracked exhaust manifold to properly evaluate the results, and it has been shown that critical identified areas correspond to the failure areas of the real sample.
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