【作者】 王超；

【导师】 于德介； 孔朝阳；

【作者基本信息】 湖南大学 ， 车辆工程， 2014， 硕士

【摘要】 汽车NVH性能是影响汽车舒适性的一个重要因素,现已成为评价汽车设计及制造质量的重要指标之一。由于商用车行驶工况非常恶劣,工作环境复杂多变。在受到各种激励的作用时驾驶室板件结构会产生振动并向车室内辐射噪声,降低了整车的乘坐舒适性,容易造成驾驶员身体感觉不适,严重时甚至会引起交通事故。降低驾驶室内噪声水平是改善整车乘坐舒适性的重要手段之一,它不仅可以提高汽车的市场竞争力,还能够产生重要的经济和社会效益。本文在长沙市科技计划重大专项“汽车轻量化关键技术研究及其产业化(项目编号：K1306007-11-1)”资助下,以一款商用车驾驶室为研究对象,利用有限元方法和声学CAE技术对该驾驶室结构振动特性以及驾驶室内噪声水平进行分析。通过计算得出前悬置激励点至驾驶室内参考点(驾驶员右耳旁)的噪声传递函数；对包围声腔的主要板件进行声学贡献量分析,得出对驾驶室内结构噪声贡献较大的板件；将这些板件的厚度值作为优化设计中的变量,建立驾驶室内参考点声压级最大值极小化的车身结构优化响应面近似模型,使用遗传算法对该近似模型进行优化,在满足约束条件的前提下,通过优化车身板件结构实现了降低驾驶室内结构噪声的目的。本文主要研究内容如下(1)利用UG软件抽取驾驶室各板件中面,将中面模型导入Hypermesh软件后划分有限元网格,建立驾驶室有限元模型；用Virtual.lab软件建立驾驶室声腔有限元模型；联合两个模型得到驾驶室结构-声腔耦合系统有限元模型；运用Nastran软件对驾驶室结构和声腔进行模态分析,获得结构和声腔的固有频率以及驾驶室内声压分布情况。(2)在驾驶室左右前悬置点施加激励,通过Nastran软件计算得到驾驶室内参考点(驾驶员右耳旁)的声压响应,确定了峰值声压及其频率,得到了驾驶室内结构噪声响应情况,为后续对驾驶室结构噪声优化提供指导。(3)对包围驾驶室声腔的主要板件进行声学贡献分析,得到对驾驶室内结构噪声影响较大的板件,将这些板件的厚度值作为后续优化设计中的变量,通过优化板件结构达到降低驾驶室内结构噪声的目的。(4)为降低驾驶室内结构噪声,以驾驶室内参考点(驾驶员右耳旁)声压级最大值极小为优化目标,以声学贡献量较大板件的厚度值为设计变量,以优化后整车质量比优化前不增加为约束条件,基于响应面方法构建了该优化问题的二阶多项式近似模型,使用遗传算法对该近似模型优化,通过优化找到一组板件厚度值,使得驾驶员右耳旁声压级最大值极小。为了更直观的掌握优化后的驾驶室内结构噪声水平,将优化前后驾驶员右耳旁的声压级响应进行对比分析,结果表明：用基于响应面方法构建的近似优化模型进行优化后,在整个激励频率范围内驾驶室内结构噪声明显降低,达到了控制驾驶室内结构噪声、提高整车NVH性能的目的。本文在驾驶室白车身结构模态分析、声腔模态分析、噪声传递函数分析、板件声学贡献量分析的基础上,基于响应面法建立了一套驾驶室结构噪声优化设计流程,该流程以降低驾驶室内结构噪声响应为设计目的,以车身板件厚度为设计变量,可有效降低驾驶室内结构噪声,具有较大的工程应用参考价值。更多还原

【Abstract】 NVH performance is an important factor of vehicles comfort and an important specification to measure the quality of automobile design and manufacturing. Commercial vehicles always run on poor road with complex and changing condition. Therefore the cab structure will produce strong vibration and noise, which can seriously affect the acoustic comfort of the driver, and can easily lead to fatigue and malaise. Furthermore, the strong vibration and noise in the cab structure may also result in errors of judgment and even cause accidents. Reducing the cab interior noise is an effective way to improve the interior acoustic environment and riding comfort, it also has important economic and social benefits.This thesis, funded by the project "The Key Technology of Vehicle Lightweight and Its Industrialization"(Project’s Serial Number:K1306007-11-1), chose a commercial vehicle as the research object. The FEM and acoustic CAE technology are used to analyze the structure dynamic performance and interior noise response characteristics of the cab of this commercial vehicle. The cab noise transfer function from the suspending point to the measured point (driver’s right ear) has been calculated. Through the panel contribution analysis, the body panels which have greater influence on the cab interior noise are identified. The thickness of those plates is set as the design variable in the follow-up optimization design. A structural optimization approximation model based on the RSM (Response Surface Method) with the objective of minimizing the maximum of SPL (Sound Pressure Level) at measure point was built up in this thesis. Then, the optimization model was optimized by the genetic algorithm and the cab interior noise was decreased by modifying the structural parameters of body panels.The main contents of this thesis are as follows(1) The middle faces of component parts in the cab were extracted from the UG models and imported into the Hypermesh software to generate the finite element mesh. The finite element model of the cab and interior acoustic cavity were established; the modals of these models were analyzed by the software Nastran. The natural frequencies of the cab and interior acoustic cavity as well as the distribution of interior sound levels were obtained from those analyses.(2) The white noise excitation was added to the cab body and the SPL at the measuring point (Driver’s right ear) was calculated. Based on those results, the cab interior structure noise was predicted and the peak sound pressures and resonance frequencies were determined, which can provide the guidance for noise control.(3) Through the panel contribution analysis, the cab panels which have greater influence on the cab interior noise are identified. The thickness of those plates is chosen as the design variables in the follow-up optimization design. The cab interior noise can be reduced by changing the body structure.(4) In order to reduce the cab interior noise and control the radiated noise caused by panel vibration, the minimizing of the maximum of SPL (Sound Pressure Level) at the measuring point was taken as the optimization objective, the weight of the cab body was taken as the constraint condition, the thickness of plates were taken as the design variables. The approximation model based on the response surface method was built up and optimized by the genetic algorithm. At last, a new set of thickness of the cab panels after the optimization was got. The SPL results at the driver’s right ear before and after optimization were compared, which show that the peak sound level is decreased by the optimization, and the goal of interior structure noise reduction is achieved.This thesis investigates the problem of modal analysis, interior structure noise predicting and panel contribution analysis of a commercial vehicle cab. Based on the RSM approximation model, a method to reduce the sound pressure level at the driver’s right ear by modifying the structural parameters of cab panels was proposed in this thesis. The numerical analysis results of a commercial vehicle cab show that the proposed method is feasible and effective.更多还原