基于广义积分规则的汽车NVH中频问题计算方法研究

The mid-frequency problems are the important contents in the process of vehicle NVH development. The discrete methods, such as the finite element (FE) and boundary element (BE), are the most widely used NVH computing methods in vehicle development. When the mid-frequency problem is calculated, there are some weaknesses in these methods, such as the low accuracy and high quality requirement of the model. In order to deal with this problem, this project firstly intends to introduce the generalized integral rule (GIR) into finite element method for the acoustic field problems of damp vehicle, and reconstruct the system matrix by utilizing the flexibility of GIR. On the basis of FE-meshfree method and perfectly matched layer method, this project intends to presents the FE method and FE-meshfree method for the interior and exterior mid-frequency acoustic field of the damp vehicle based on GIR, and thoroughly investigate and evaluate these methods. Then, aiming at the structural-born mid-frequency noise problems of vehicle, the boundary element system matrix will be reconstructed by the GIR, and the FEM/BEM based on GIR for mid-frequency structural-acoustic coupled of vehicle is proposed on the basis of structural-acoustic coupled theoretic, and the precision and effectiveness of these methods are studied at the same time. At last, the effectiveness of these proposed methods are evaluated by through some experiments, and these methods are used to compute the acoustic modal and structural-born noise transfer function (TPA) of vehicle. The research of this project will propose a class of novel computing methods for vehicle mid-frequency NVH problem, and these methods provide high precision results and improved the engineering applicability.

中频(200-500Hz)问题是汽车NVH开发的一项重要内容，目前应用最广的汽车NVH中频计算方法是有限元、边界元等离散法，存在精度低、模型质量要求高等缺点。为解决此问题，本项目首先拟将广义积分规则引入有限元法中，针对考虑阻尼的汽车中频声场问题，利用广义积分的灵活性重构系统矩阵，在有限元-无网格法、完美匹配层法的基础上拟提出基于广义积分规则的有阻尼汽车内、外中频声场有限元法与有限元-无网格法，并对其数值色散进行研究、评价。接着，本项目针对汽车中频结构噪声问题，利用广义积分重构边界元系统矩阵，在结构-声场耦合理论基础上拟提出基于广义积分规则的汽车中频结构-声场耦合有限元-边界元法，并深入研究其计算精度与效果。最后，本项目拟通过实验对该方法的有效性进行评估，并将该方法应用至车内声腔模态以及概念车身结构噪声传递函数的计算中。本项目拟为汽车NVH中频问题提供一种精度较高、工程适用性较强的计算方法。

目前汽车NVH中频问题预测方法中有限元、边界元等离散方法的数值色散明显、对模型质量要求较高，且现有广义积分规则的研究工作未考虑阻尼对数值色散的影响，如何研究一种新型数值计算方法具有十分迫切的现实意义。本项目主要研究：1）研究基于广义积分规则的有阻尼内、外中频声场有限元法，研究基于广义积分规则的有阻尼车内声腔中频有限元法，同时利用完美匹配层法，研究基于广义积分规则的汽车外声场中频有限元法。2）结合广义积分规则，对基于广义积分规则的有阻尼车内、外中频声场有限元-无网格法进行研究，包括基于广义积分规则的有阻尼车内中频声场有限元-径向点插值法(FE-RPIM)和基于广义积分规则的有阻尼车外中频声场有限元-径向点插值法。3）将广义积分应用至汽车结构-声场耦合计算中，研究包括基于广义积分规则的汽车中频声场边界元法和基于广义积分规则的汽车中频结构-声场耦合FEM/BEM。4) 为评价上述算法的有效性，针对声固耦合系统不确定计算、车内声场问题以及声子晶体带隙计算问题进行验证，研究结果验证提出理论的可行性和正确性。 通过项目研究得出以下主要结果与关键数据：1) 找到了基于广义积分规则的有阻尼系统的声场有限元方法的积分点位置(积分点坐标为0.81344)，该积分点位置是通过遗传算法寻找到最小色散误差的位置，具有计算精度高、获取方式简单的特点；此外还找到了基于广义积分规则的有阻尼系统的声场有限元—最小二乘点插值方法的最佳积分点位置(积分点坐标为0.57497)；同时在声子晶体带隙计算中验证了有效性；2) 提出的外声场问题计算的基于广义积分规则的有限元--无网格法/完美匹配层法，通过数值试验验证了该方法在中频外声场计算具有比传统有限元法的计算精度更高。3) 提出的基于广义积分规则的有限元-无网格法/边界元法在结构-声场耦合问题的计算中效果比传统方法更好。