Prediction of Fatigue Strength of Motorcycle Exhaust System Considering Vibrating and Thermal Stresses 2015-32-0739

A method applicable in the design stage to predict fatigue strength of a motorcycle exhaust system was developed. In this prediction method, a vibrating stress, thermal stresses, stresses resulting from the assembling of the exhaust system components and a deterioration of fatigue strength of materials originated from high temperature were simultaneously taken into account. For the prediction of the vibrating stress, flexible multibody dynamics was applied to get modeling accuracy for vibration characteristics of the entire motorcycle and the exciting force delivered from engine vibrations. The thermal conduction analysis and the thermal deformation analysis based on finite element method (FEM) were applied for the prediction of thermal stresses in the exhaust system components. The temperature distribution on the surfaces of the exhaust system components is required for calculations of the thermal stresses. The heat transfer analysis, which was composed by combing a one-dimensional (1D) engine cycle simulation and an air flow simulation around the vehicle by 3D-CFD, was used for the estimation of temperature distributions. To validate the developed method, the correlations between the simulations and the actual measurements were analyzed for the vibrating stress, the temperature distribution, the thermal stresses and the fatigue safety factor. High correlations were yielded between them proving the validity of the new method.