The Analysis Of Vibration And Noise In Vehicle Interior Sound Field Based On Node Integral And Statistical Energy Method

With the rapid development of automobile industry,consumers have more and more attention on the vibration and noise of automobiles.In the process of product development,CAE technology plays an indispensable role which can effective control the vibration and noise level and reduce the upfront costs.This technology is usually based on different numerical methods while dealing with different frequency region problems.Between high-frequency and low-frequency region,there is a mid-frequency region which is difficult to predict precisely the frequency response due to the complex form.The traditional methods are no longer appropriate to the mid-frequency structural-acoustic analysis.Due to the limitations of the above numerical methods,this paper proposed a series of improved coupling methods by introducing the stable node-based smoothed finite element method(SNS-FEM).The dissertation includes:(1)For the structural-acoustic analysis,a coupled node-based smoothed finite element method(C-NS-FEM)for mid-frequency is proposed.In the structure domain,the formulation is based on the classical Kirchhoff hypothesis and the problem domain is discretized using three-node triangular meshes.The integration domains are further formed based on the nodes of element,and the generalized gradient smoothing technique is introduced to construct the strain filed.In the fluid domain,four-node tetrahedral elements are utilized to discretize the acoustic cavity.The gradient smoothing operation and the numerical integration are applied over the further formed node-based integration domains.To verify the effectiveness of the present methodology,both benchmark and practical engineering problems are studied.The excellent results demonstrate that the proposed method performs very well in mid-frequency structural-acoustic simulations.(2)For the vibro-acoustic coupling problems,a novel hybrid stable node-based smoothed finite element method/statistical energy analysis(SNS/SEA)method is proposed.The whole vibro-acoustic system is divided into a combination of a structural subsystem with statistical characteristic and an acoustic subsystem with deterministic feature.The recently developed SNS-FEM is employed here to simulate the deterministic subsystem,and the well-known SEA is utilized to deal with the statistical subsystem.Numerical examples,including both benchmark cases and practical engineering problems,have been conducted to demonstrate the effectiveness and accuracy of the hybrid SNS/SEA for mid-frequency vibro-acoustic problems.(3)For the transmission loss predictions of the vibro-acoustic system,the theoretical framework of three subsystems is constructed based on SNS-SEA.The SNS-FEM can provides an ideal stiffness to the coupled system in the transmission loss problems.Besides,the the vibro-acoustic system with three subsystems can fully consider the impact of statistical properties based on SEA.This framework can effectively consider the interaction between the direct field and reverberation field in each subsystem and establish the the power balance equations between each subsystem through the ‘diffuse field reciprocity relation’.A standard numerical example and car windshield model are constructed to analysis the transmission loss and coupling loss factor of the vibro-acoustic problems.The excellent results demonstrate that the proposed method performs very well in mid-frequency structural-acoustic simulations.