Research On Uncertainties And Acoustic Vibration Problem Of Low Speed Truck With High Precision Numerical Method

Research and analysis on acoustic vibration problem as well as uncertainty of low speed truck have great engineering application value and research significance.To predict and control noise of coupled cavity is an important way for solving acoustic vibration problem.Due to the strong coupling between the cavity and structure,making this process particularly difficult.In addition,the impact of production,assembly,measurement and external environment on the product will lead to uncertainty of its attributes.Because of the widespread existence and increasing accumulation of uncertainty,it may accumulate a huge impact on the sound pressure response of acoustic vibration system.However,with continuously improvement and optimization of numerical calculation methods as well as CAE software,making it more convenient for manufacturers to test acoustic characteristics of products in design stage with commercial software.It is beneficial that offering noise optimization schemes,proposed by manufacturers,to reduce product development cycle,production cost and improve product competitiveness.At present,numerical methods such as finite element method(FEM),meshfree method and boundary element method(BEM)are the core algorithms of commercial CAE software,and play an important role in noise prediction.In this context,the numerical method has become key technology to solve acoustic vibration problem and uncertainty.Main work and achievements of this paper are as follows:(1)Acoustic and vibration problem of plate structures with closed cavities are studied.The finite element least square point interpolation method / boundary element method is proposed.FE-LSPIM shape function is applied to dynamic analysis of a plate structure at first.And the discrete equation of plate structure is obtained.Then,boundary element method is applied to three-dimensional sound field.The boundary conditions are established according to the acoustic Helmholtz wave equation,and acoustic Helmholtz boundary integral equation is used to obtain the sound field discrete equation.Finally,a FE-LSPIM / BEM coupling matrix equation is proposed to analyze the acoustic vibration problem of plate structure under the condition of continuous coupling interface displacement and pressure.The expression is extended to a hexahedral model with elastic plate,and frequency response function of acoustic pressure is obtained.The results show that FE-LSPIM / BEM has good calculation accuracy.(2)In order to research and study uncertainty of acoustic vibration problem,a stochastic model is introduced into the acoustic vibration system of plate structure.The stochastic perturbation finite element least square point interpolation / boundary element method(SP-FE-LSPIM / BEM)is derived by combining variable transformation technique method,and is used to solve uncertain acoustic vibration problem.Linear expressions of random variables and responses are given as well.The probability density function distribution of sound pressure and response is analyzed by numerical examples.Effectiveness of stochastic perturbation finite element least square interpolation method /boundary element method is verified.(3)Based on the research results of acoustic vibration problem and uncertainty of plate structure,the stochastic perturbation finite element least square point interpolation/ boundary element method is extended to the study of acoustic vibration problem and uncertainty of low speed truck.Firstly,a simplified model of low speed truck is established,and dynamic analysis is carried out by using plane shell element and coordinate transformation method.Stiffness matrix and mass matrix are derived,the FE-LSPIM /BEM coupling matrix expression of the simplified model is obtained.Then,frequency response function curve,probability density function distribution of sound pressure and response are obtained by numerical calculation.Finally,modal test results verify the reliability and applicability of this method in acoustic vibration problem of low speed truck.The author has done research on acoustic vibration problem and uncertainty numerical calculation methods to a certain extent,and focusing on the improvement of calculation accuracy of FE-LSPIM / BEM for acoustic vibration problem and the reliability of the SP-FE-LSPIM / BEM for uncertainty analysis.From the results of modal test and sound pressure response,those methods can be well applied to study acoustic vibration problem and uncertainty of low speed truck,which lays a solid foundation for further engineering application.