The Fatigue Reliability Of The Automobile Engine Exhaust Manifold Assembly Optimization Research

With the improvement of national emission standards, the exhaust system is more and more close to the exhaust manifold, catalytic carrier within eventually exhaust manifold and catalysts, become an organic whole called the exhaust manifold assembly. The poor working conditions of exhaust manifold assembly which not only outer surface gas and inner chamber temperature is difference, but also long-term under cyclic alternating temperature load, the phenomenon such as prone to fatigue failure, make the engine emissions increase, bigger noise, power fluctuations, and even the engine failure.Due to the engine performance is increasing day by day, the exhaust temperature is rising, so the requirements of fatigue reliability of the exhaust manifold assembly become more and more important. Used finite element simulation technology to analyze its fatigue reliability, optimize its structure, can effectively reduce the number of test prototype, shorten product development cycle, for a lower costs, bigger market competitiveness.This thesis use simulation analysis combined with experimental verification, for the vibration and thermal fatigue problems studied, it is purpose is to optimize the weak life place of exhaust manifold assembly.The main content of the thesis is as follows:(1) Established3D model for the exhaust manifold assembly, combined with ABAQUS software for modal analysis and thermal stress analysis, and then import to the FE-SEFE for thermal Fatigue analysis.(2) The optimization study on the exhaust manifold assembly, according to the simulation results of original mold optimized structure, and then simulation the structure again, The results indicate that each order natural frequency of the optimized exhaust manifold assembly is increase, that reducing the resonance risk maximum stress reduced7MPa and thermal fatigue performance meet the design requirements.(3) On the exhaust manifold assembly for fatigue reliability experiment, clear experiment and basic requirements of the relevant data collection, validation of the simulation results of the analysis.Experimental fatigue reliability of research results show that the300hours after the exhaust temperature and pressure, degradation rate less than5%, exhaust manifold assembly surface, no crack, comply with the design requirement; Platform vibration contrast test results show that the optimized vibration decrease obviously. Therefore, this study optimized exhaust manifold assembly simulation is reliable, anti-fatigue ability to comply with the design requirements.