2 有限元分析理论与车内噪声产生机理 ................................................................. 7
2.1 有限元法概述 ........................................................................................................................... 7 2.1.1 有限元法的发展及基本思想 ............................................................................................ 7 2.1.2 有限元法的基本步骤 ......................................................................................................... 7 2.1.3 有限元法在汽车工程中的应用 ........................................................................................ 9 2.2 声学有限元法 ......................................................................................................................... 10 2.3 车内噪声产生机理 ................................................................................................................. 10 2.3.1 结构噪声 .......................................................................................................................... 10 2.3.2 空气噪声 .......................................................................................................................... 11 2.3.3 声腔共鸣 .......................................................................................................................... 11 2.4 Hyperworks 简介 .................................................................................................................... 12 2.4.1 Hypermesh 介绍 ................................................................................................................ 12 2.4.2 Optistruct 介绍 .................................................................................................................. 13 2.4.3 Hyperstudy 介绍................................................................................................................ 13 2.5 本章小结 ................................................................................................................................. 13
A Thesis Submitted to Chongqing University in Partial Fulfillment of the Requirement for Professional Degree
By Hui Fei
Supervised by Prof. Zheng Ling Pluralistic Supervised by senior Engineer Suyu Specialty: ME （Automobile Engineering Field）
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重庆大学硕士学位论文
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英文摘要Βιβλιοθήκη ABSTRACTWith the improvement of requirement for vehicle comfort, improving NVH characteristics of vehicle is the principal means to upgrade the vehicle and improve the competitiveness. Based on a SUV, the finite element model of car body ,acoustic cavity and acoustical-structure interaction has been built. The characteristic of NVH has been analyzed, including BIW (body-in-white modal), vehicle modal, acoustic cavity modal, the torsion and bedding stiffness of BIW, acoustical-structure interaction NTF, acoustical-structure interaction VTF and acoustical-structure interaction IPI. Using the volume and one order torsion and bend frequency as the objective function and constraints, the optimization of improving the body frequency has been done by using response surface method and optistruct. The results as follow： ①The finite element models of car body, car and acoustic cavity have been built, the modal of car body, car and acoustic cavity has been analyzed. With the analysis one order torsion and bend frequency are get as 33.4Hz and 44.3Hz, which is the basis of the optimization of car body. ②Based on the actual driving situation of car boy, the torsion and bedding stiffness have been analyzed. Compared to the car boy stiffness of the car, the result is reasonable. The curves of torsion stiffness and bedding stiffness have been gotten. Which indicates the stiffness of car body is uniformly distributed. ③The finite element model of acoustical-structure interaction has been built by DIFF. the characteristic of NTF、VTF and IPI have been analyzed, with different stimulations the peaks of sound pressure, vibration and dynamic stiffness have been get, which indicate the characteristic of NVH is reasonable. ④The experimental matrix has been get by Latin hypercube design, and the response surface models of car volume, one order torsion stiffness and one order bedding stiffness have been built by using response surface method. The optimization of genetic algorithm is used to optimize the thickness of plate, the result shows the quality has decrease 22.8kg, the torsion stiffness has increased2Hz and the bedding stiffness has increased1.5Hz. Key words: NVH, modal, response surface method, structure optimization