Analysis Of Truck Cab Noise Based On Finite Element Method

With the development of the automotive industry, the demand of the car's traveling comfort, especially the vehicle's vibration and noise characteristics is convincingly strengthened. The state has also established vehicle noise regulations. In the past only the problems of the car's vibration and noise were paid attention to, but with the improvement of people's living, trucks gradually become a hot research focus because of poor performance of noise and driving comfortable. Low-frequency noise direct impact driving comfortable, so it also becomes the focus of the study.It would cause serious losses if the noise vibration is discovered after the automobiles produced, and it would pay a high price to improve the automobiles noise performance. So vibration and noise control and optimization should become important content and a key tache in the car's design phase. But the traditional noise test technology can only base on the real model, so it is required to use digital model simulation in the design stage.The research of this paper is to analyze and forecast the cab vibration and noise characteristics in the design stage of the automobile using finite element method. To build the three-dimensional cab(beams and plate ) and the fluid model, then analyze and figure out the cab modal of different thickness of wall respectively in Block Lanczos and Unsymmetric algorithm, and then draw the influence of different plate thickness on the cab dynamic characteristics; to calculate the Cavity modal in the case of having seats and no seats, to draw the influence of the seat in the cab on the vacuum acoustic characteristics; using the APDL command of ANSYS, we build acoustic-structure coupling model considering the air and structure interaction, and comparing the dynamic characteristics of acoustic-structure coupling model with the structure and cavity modal after calculation, we summarize a law: the influence of air acting on the plate's dynamic characteristics is along with the frequency.In the end using Full harmonic analysis on the coupled model of the cab, the result of harmonic force can be gained. Under the guide of the result of harmonic analysis and the result of the cab structure modal analysis, acoustic cavity modal analysis and the acoustic-structure model analysis, ameliorating the structure of the cab in order to reduce noise, we could find the noise is lower than before. So it is feasible to analyze the cab under the guide of the dynamic characteristics by finite element method, and ameliorate the cab to reduce noise. This research involves the theory of finite element method, modal analysis, and harmonic acoustic analysis. Many pivotal issues have been discussed in-depth, such as the modeling technology, modal analysis and acoustic-structure coupling analysis. This thesis has a relatively complete system of research on the analysis of the acoustic field inside cab, so it can be used as a reference for low-frequency noise design of vehicles.