Effect of perimeter fins in low cycle fatigue for exhaust manifold

The effect of perimeter fins on the thermal stress and low cycle fatigue life (LCF) of exhaust manifolds was investigated. For doing this, Solidworks software was used to model the exhaust manifolds. Three Perimeter fins with 4 mm thickness was attached to the modified exhaust manifolds outlet section. Then ANSYS Workbench software was used to determine stress and fatigue life based on Morrow and Smith-Watson-Topper (SWT) approaches. Finally, the improvement of the low cycle fatigue life was studied. The temperature-dependent of material parameters was considered in order to increase the accuracy of LCF life results. The results of finite element analysis (FEA) uncovered the fact that perimeter fins reduce the temperature distribution in the exhaust manifolds about 32.54°C. As a result, the exhaust manifolds tolerates lower temperature and fatigue life will increase. The results of thermo-mechanical analysis indicated that the stress in the modified exhaust manifolds decreased approximately 22MPa for the sake of depletion of temperature gradient which can lead to higher fatigue lifetime. The results of LCF showed that the number of cycles of failure for modified exhaust manifold is approximately 55% higher than the results obtained from the original exhaust manifolds.