Simulation And Research On Frequency Acoustics Mode Of Heavy Duty Commercial Vehicle Cab

With the development of automobile and the increasing awareness of the energy conservation and environmental protection, the automobile industry starts to develop in the direction of high speed and light design. Light design has become the main reason of increasing structure vibration and the vehicle internal noise, therefore reduces the vibration and the noise, especially, have the vital significance to enhance ride comfortableness of the vehicles. for the exploder of new vehicle, to avoid the process of Vehicle Design- Experimental Test-Vehicle Revision, and consume massive manpower,financial resource and increase design cycle, the FEA method can be applied to the NVH study on calculate and analysis of inner vehicle.By the precise vehicle structure and cavity model, one side, it can optimize interior acoustics design by the vehicle acoustics modal analysis, and avoid acoustics resonance; On the other hand, it is accurately simulate interaction between vehicle structure and interior acoustics fluid by the modal analysis with coupling FE model, Identifying the couple system's resonate frequency and pressure distribution, understanding dynamic characteristics and acoustics response of coupled system and forecasting the interior noise response at design stage, to achieve the new automobile optimizing design.This paper is based on the body-in-white FEM of some heavy commercial vehicle, applying software MSC.NASTRAN/PATRAN and HyeperMesh, established a close structure finite element model-Str_C. Based on the modal analysis results of Str_C, adjusted and established the simplified structure model-Str_S. By the two structure model, here established the acoustic model-Cav_C_Noseat,Cav_S_Noseat (not consider the seat) and Cav_C_seat,Cav_S_seat (consider the seat), with their modal analysis results, indicating the effects of compartment cavity acoustics model with seat.This paper compares the computed results of Cav_C_seat,Cav_S_seat with the compartment cavity acoustics test modal analysis results, the error rate between the two modal analysis results with test result is within 10% and 6%, which prove that the two value basically is consistent in each other, at the same time, it indicates that the simplified cavity model Cav_S_Noseat is available in coupled system. Last, it identifies the modal frequency and mode shapes by the computed results of the coupled system, which is established with Str_S and Cav_S_Noseat.The effective of the cavity simplified finite element model illuminates that it can pilot research the acoustics characteristic on the cavity simplified model which established by the size of the cavity cab in the early development of the new vehicle; Otherwise, it can also use the simplified and effective model to substitute the detailed model for the coupling simplified model for frequency response analysis, to analysis the cab noise levels and guide the structural optimization and design of the cab.This paper in order to find out the influence of the loudhailer volume in the test, from the modal analysis results after deleting the cavity element just as the loudhailer space, the modal frequency reducing 1-2Hz, but the mode shapes are not changed. This indicates that it can be without regard to consider the influence of the loudhailer size in the modal analysis of the acoustic cavity model as the qualitative analysis phase or before new product exploiting.Finally this article conducts the exploratory research to the coupled system because of time restricted, which suggests to establish a coupled system with all trimmed material, such as damp and sound absorber.