Multiaxial fatigue analysis of exhaust manifold with considering viscosity stress
Subject Areas : Journal of New Applied and Computational Findings in Mechanical Systems
1 - Department of Mechanical Engineering, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran
Keywords: exhaust manifold, finite element analysis, multiaxial fatigue and viscosity stress,
Abstract :
Due to the complex geometry and loading conditions, exhaust manifolds are the most challenging components among all parts of engines. They must withstand severe cyclic thermo-mechanical stresses throughout their lifetime. Thus, simulation and analysis of fatigue cracks is essential. In this paper, low cycle fatigue (LCF) life analysis of the exhaust manifold is performed by using the finite element method and ABAQUS software to predict the temperature and stresses and then LCF life by using Brown-Miller theory and MSC-FATIGUE software. The combination of the Chibcha nonlinear isotropic-kinematic hardening model with viscous stress law is used to consider the effect of viscosity stress. The results of finite element analysis showed that the maximum temperature and stress values in the exhaust manifold are 757.7°C and 395.2MPa and the position is at the confluence region. Therefore, the confluence area of the engine exhaust manifold is a critical area and there is a possibility of possible cracks in it. The fatigue life of the exhaust manifold without and considering the effect of viscosity stress was calculated as 9310 and 8850 cycles. In other words, neglecting the viscosity effect caused an estimation of 460 cycles or about 5.2% higher than the limit. Therefore, it is necessary to consider the viscosity effect in the analysis of the low cycle fatigue life of the exhaust manifold.
