Study On The Equivalent Model Of Rattle Noise Pair Of Automobile Body

The NVH performance of a car is a key factor in determining the quality of the car.Years of research have greatly reduced the overall noise level of the car.The Squeak &Rattle(S&R)produced by the car body is more prominent.The traditional "find-repair" method to solve the S&R problem has limited optimization effect and high cost.The use of CAE technology to analyze nonlinear problems also has problems in meshing and solving.Therefore,a convenient and fast and accurate method for predicting S&R problems of car body is needed.This paper studies the equivalent model of the impact force of the car bodys rattle noise problems prediction,and proposes a rapid prediction method for the car bodys rattle.The focus of this paper is to study the method of predicting the rattle noise problems of car body.In order to directly measure the collision force,the experimental scheme of the cantilever beam collision with a fixed hammer is used.According to the experimental collision force signal,the peak collision force and initial collision velocity of each collision are extracted.The results show that the peak value of collision force increases with the increase of collision velocity,and changes linearly.In order to quickly predict the collision force,an equivalent model of single elastomer colliding a fixed stop and two elastomers colliding with each other is proposed.In the equivalent model,the collision force is assumed to be half sine wave,and the calculation formula of collision force is deduced based on Hertz contact theory and transfer function method.The results show that the relative error between the mean square value of the collision force of all material pairs and the experimental results is less than 20% under most working conditions with excitation frequencies of 8Hz,11 hz and 13 Hz.It is verified that the model can quickly and accurately predict the collision force of metal-metal and metal-nonmetal materials,which makes it have a broad application prospect in the field of automobile NVH control,especially in the prediction of car body rattle.In order to quickly predict the collision response,the local nonlinearity of the nonlinear system is treated as the feedback of the linear system,combined with the advantages of the transfer function method to calculate the linear vibration response speed,a serial calculation method for the rapid prediction of the collision response of complex structures is proposed.In this method,the system is divided into the linear part of the original excitation and the nonlinear part of the local nonlinear calculation replaced by an external excitation source.The experimental results show that the collision response of complex structures can be equivalent to the superposition of the system responses subjected to multiple excitations.Using the collision force calculated by the equivalent model in Chapter 3 as input,the calculated collision response error is below 10%,which verifies the correctness of the proposed collision force equivalent model.The maximum error of the collision response predicted by using the serial calculation method is 38%,and the maximum difference between the collision noise SPL and the measured results is2.5927 d B,which verifies the accuracy of the method for predicting the collision noise.In a word,the collision force prediction equivalent model and the collision response fast prediction method proposed in this paper both have the advantages of high accuracy and fast calculation speed.For the vehicle body and interior structure that has many rattle noise areas that need to be evaluated,more accurate evaluation results can be quickly obtained.