Study Of Fautigue Strength And Experiment Of Engine Exhaust Manifold

With emission standards of cars in China improved step by step,related to the structure of automotive in the engine exhaust manifold is as much as possible to do optimization design.As everyone knows,the working conditions of the engine is very bad,while the gas manifold surface temperature and air temperature in the inner cavity of the difference,and in the long-term cyclic loading cycle,easily lead to fatigue failure phenomenon,and then make the engine exhaust emissions increase,power fluctuation,noise and even cause engine failure.The article uses the theoretical analysis,simulation analysis and engine bench test to verify the combination method,on the engine exhaust pipe of the thermal fatigue,vibration and fatigue strength were studied so as to find out the exhaust pipe of the engine life weak point and its structure optimization.The main contents of this paper are as follows:(1)According to the pre engineering test results,combined with the basic theory of fatigue strength,judge the failure mode and position of the engine exhaust pipe,according to the judgment of the focus and ignore has very little effect on the results of the analysis of secondary structure,established the exhaust pipe of the engine model used for analysis.(2)Using CATIA software to engine exhaust pipe of the establishment of the three-dimensional model,combined with HyperMesh software on the engine exhaust pipe model of mesh free modal analysis,according to the structure of the modal analysis and comparison of the results,excluding effects of resonance of the exhaust tube life,to identify the impact fatigue strength of the key factors.(3)Using ABAQUS software on the engine exhaust pipe finite element model of thermal stress analysis based on the stress analysis results,find out the engine exhaust pipe structure of stress concentration and the maximum stress size.To reduce the stress concentration phenomenon for the purpose of the model is modified and the modified again simulation analysis.(4)Using CATIA software,according to HyperMesh modal analysis results of ABAQUS and the thermal stress analysis results of exhaust pipe structure optimization and the establishment of optimized finite element model.The optimized model appliedboundary conditions and optimization of the same again modal analysis and thermal stress analysis.Eventually remove the exhaust pipe rupture caused by resonance,judged to be due to local stress concentration caused by the exhaust pipe rupture.Simulation results show that the structure optimization of exhaust pipe stress value than previously reduced 8.7%,the modified theoretical model on can meet the intensity requirement.Using the Ncode software to analyze the life of the model before and after the structure modification,the results of the two analysis were compared and found that the modified exhaust pipe was improved by 34% before the modified exhaust pipe,which can meet the test requirements.(5)According to the national standards GB/T18297-2001< automobile engine performance test method >,GB/T19005-2003< strength test method for Automobile Engine >,Group enterprise standard <LF479Q2-B engine performance test outline >,the engine LF-FD-CJ-01< test specification > and relevant technical requirements of building test bench and 400 hours of reliability test and the data were collected,and30000 kilometers of road test.Finally,the experimental results are analyzed.