Modal Analysis And Verification Of Plastic Fuel Tank

With the improvement of automotive yield and the employment of lightweight materials,the occupancy of plastic fuel tanks in vehicles is increasing.Fuel tanks are connected with bodywork by accessories and are filled with liquid in their service condition.The fluid-structure interaction makes vibration problem of fuel tanks more complex.It is significant for understanding the dynamic characteristic to study the vibration of plastic fuel tanks with fluid-structure interaction in service condition.For the vibration problem of plastic fuel tank,finite element modal analysis of a plastic fuel tank assembly,the design of modal test platform as well as test modal analysis and verification of fuel tank test were carried out in this paper.The research results are of great significance to improve the overall design of fuel tank system.Firstly,the key technologies of finite element modeling of fuel tank assembly system were studied,including the processing methods of fuel tank body,rubber gasket,oil pump and steel belt model.The finite element model of fuel tank structure was established,based which the modal frequency and mode shape of the fuel tank system under free and installed state were analyzed.The modeling method of fluid in fuel tank was studied,and the fluid-solid coupling finite element model of fuel tank was built up.The fluid-solid coupling modal frequency and vibration mode of fuel tank in free state were analyzed using this model.Furthermore,the calculated modal analysis of fuel tank with different liquid filling amount under the installation state was carried out,and the influence of various liquid levels on the fluid-solid coupled modal frequency and vibration mode of fuel tank was analyzed.In order to simulate vehicle constraint condition of fuel tank in laboratory,topology optimization model of the test platform with frequency restraint was established.The design objective was to realize the maximum of the first nature frequency of the platform,with the volume fraction as the constraint.The RAMP interpolation method with variable density was applied to design the prototype of the fuel tank test platform.By summing up the design rules of the topological optimization results,the test platform manufactural scheme and real object that meet the modal test requirements and manufacturability standards are obtained.The experimental modal analysis of fuel tank under different boundary conditions and liquid level was carried out to understand the accurate modal characteristics of plastic fuel tank.In free state,the effects of surface holes on frequency response function and resonance frequency was studied.The test specification for fuel tank in free state was proposed then,to conduct modal tests of empty case and fluid-solid coupled case.The designed platform was used for modal analysis of fuel tank under installation.The modal parameters of fuel tank under different liquid level are identified.Finally,through the modal verification parameters such as MAC,MPC or MPD,the changes of tested modal mode of plastic fuel tank were analyzed,and the influence mechanism of internal liquid on fuel tank tested mode was discussed.To compare the effectiveness of fuel tank simulation model,the results of fuel tank modal simulation are compared with tested modal frequencies and modes.The design parameters of fuel tank are uncertain.The posterior probability density of the uncertain parameters was obtained by studying the distribution rules of the uncertain parameters.Finally,the effectiveness of the simulation model is verified by Bayes factor in each state.