Risk Prediction Of Rattle On Automobile Console

Automobile NVH and S&R are the main aspects that affect automobile product comfort,and are one of the most direct reflection of automobile quality.With the improvement and development of automobile noise control technology,the vehicle noise has been well controlled,but S&R of the car body which was previously covered has become more obvious.At present,there are mainly "discovery and repair" method with high cost and long cycle,modal analysis and relative displacement analysis without considering the nonlinearity of S&R,which can improve the performance of S&R,but the effect is limited.In order to overcome the above shortcomings,considering the nonlinearity of rattle,this paper studies the equivalent collision model of rattle of car body and the feedback algorithm based on the equivalent collision model to solve the structural vibration response,and proposes a fast prediction method of rattle of automobile console.Based on the Hertz contact force model,the collision force pulse was assumed to be a semi-sine wave and the contact stiffness and the impulse response function of the origin of the collision point were combined to deduce the collision force equivalent model theory of a single elastic body impacting the rigid block and two elastic bodies impacting each other.Secondly,a feedback combinatorial method for solving the structural impact vibration response by treating the nonlinear impact force as the external secondary excitation of the linear system is discussed.This method avoids solving the time-consuming nonlinear differential equations and considers the coupling effect of the impact force and the structural vibration response at every moment.In order to verify the equivalent collision model,a cantilever beam impingement rigid block under 24 working conditions with two material pairs,four excitation frequencies and three clearances was carried out.Statistically,it was found that the peak value of experimental impact force was positively correlated with the initial impact velocity under the same material pairs,and the duration of impact force was negatively correlated with the initial impact velocity.The experimental collision force is compared with the equivalent model under different working conditions,and the waveform of the two is basically consistent.In steady-state phase,the power spectral density curve has high coincidence degree and the energy concentration frequency band is consistent.The peak value and impulse of the predicted impact force are highly consistent with the experimental statistics and are positively correlated with the initial impact velocity,and the relative errors are less than 10%.When verifying the feedback algorithm,the relative error between the vibration response of the impact point of the cantilever beam and the measured response signal is basically less than 10% by the simulation calculation of the cantilever beam system with different material pairs and different clearances.In this paper,the vibration response of the structure is solved by using the feedback algorithm based on the equivalent collision model combined with finite element modeling and modal reduction.ANVL(average normal vibration velocity level of surface nodes)is proposed to characterize the rattle.The simulation results show that there is an obvious linear correlation between the total sound pressure level of space observation points and the characteristic quantity ANVL of structural vibration response,and the correlation coefficient is 0.987.Accordingly,the ANVL based rattle risk evaluation standard of the console of the vehicle is established.According to the evaluation condition,the rattle risk of the product is assessed as slight.Deputy for the automobile console built finite element model of free degree is 2468822,potential rattle nodes to 1030 vice,road spectrum is obtained by using the ordinary microcomputer excitation collision vibration response of structure under the time histories of 19005 s,the rattle prediction of 27309 s,shows that this forecasting method can meet the needs of practical engineering calculation efficiency.