轻量化车身的结构噪声快速预测模型及计算方法研究

Energy-saving and emission-reduction make cars’ weight lighter and lighter. This leads to the distinctness of car interior low-frequency noise and the growing pressure of noise reduction. However, the calculation and analysis methods now used to study the structure-borne sound of auto body are showing its shortcomings, such as labor intensity, content variety, time consuming, and to achieve the effective and feasible improvements, the modeling and calculation needed to be repeated dozens or even hundreds of times. As an alternative, a new calculation method which is based on the fundamental source of peak noise appears. It preliminary demonstrates the excellent performances and is a new research area of body structure-borne sound. .So, focus on this new research area, the experimental platform is built and the modes and interior noise of the car is tested in this research proposal. Using the testing results and the acoustics theory, vibration mechanics etc. the accuracy of the formula of car interior sound pressure is studied when used for non-rectangular coupling system. The accuracy of the numerical method of the parameters is also studied. The effect of a couple of key parameters to the accuracy of the formula of sound pressure is analyzed. The ways to improve the computing speed is discussed. Then a fast computation method and model of structure-borne sound is proposed. Referencing the testing results of a real car and the computation time of regular methods, the computation efficiency and accuracy of the new method when used to calculate the interior noise of a lightweight auto body are evaluated. Consequently, the fast computation method and model of structure-borne sound of lightweight auto body is achieved. It lays a theoretical and technical foundation for the rapid design of car interior environment for high acoustic comfort.

节能减排促使车身不断轻量化，导致车内低频噪声更加凸出，降噪压力日益增长。现有车身噪声的计算分析方法，工程师劳动强度大、计算内容多、耗时长；为获得有效可行的改进方案，需要几十次甚至上百次地重复建模和计算，劣势逐渐凸显。基于噪声峰值根本来源的车身低噪声计算方法，初步表现出优良性能，是车身噪声研究的一个新方向。鉴于此，本项目以此新方向为研究领域，搭建实验平台，测试模态和车内噪声，基于声学理论、振动力学等，研究计算非矩形耦合系统时车内声压计算公式的准确度，及各参数数值计算方法的精度，讨论几个关键参数对声压计算公式的精度影响，研究提高计算速度的途径，提出一种结构噪声的快速预测模型及计算方法。将新方法用于某轻量化的车身上，利用实车测试结果，以常规方法的计算耗时为参照，评价计算效率及计算精度，进而形成一种面向轻量化车身的结构噪声快速预测模型及计算方法。为快速设计高舒适性的车内声学环境奠定理论与技术基础。

保护环境、节能减排加速车身结构的轻量化，使车内噪声问题更加恶化，车内降噪压力日益增加。然而，现有研究车内低频噪声的计算方法，由于建模复杂、计算内容多、耗费时间长，迫切需要一种省时、省力的新计算方法，因此研究一种车身结构噪声的快速预测模型及计算方法。首先，基于一般腔体结构的腔内声压计算公式，提出其有限元离散化计算法，并搭建实验平台进行试验验证；然后，讨论影响有限元离散化法计算精度的离散量，讨论振型耦合系数、频率重叠系数的特点，分析9个参数对腔内声压的关键程度及影响规律；最后，基于有限元离散化计算法，提出一种结构噪声的快速预测控制模型及计算方法，并将其应用到某两厢车和三厢车的车内低频声压的预测及控制中。.主要研究结论有：（1）振型耦合系数的特征是随着结构、声腔各阶模态节线数的增加，随着结构和声腔模态在耦合面上对应边节线数之差的增加，非零振型耦合系数呈减小趋势。（2）频率重叠系数的特征是结构和声腔的固有频率与激励频率越接近时，频率重叠系数的幅值越大，反之越小。（3）腔内声压的关键参数是结构振型、结构板厚、激励点振型分量，建议按照控制结构振型、增加结构板厚、控制激励点振型分量的顺序逐次进行结构低噪声设计。（4）基于有限元离散化法提出的结构噪声快速计算方法，可将声压响应进行矩阵分解，通过声压分解矩阵的柱状图，一次性找出所有阶关键结构模态，进而快速提出结构改进措施；并且评价改进措施的有效性时，只需计算改进结构的固有频率和振型，即可进一步计算出腔内声压。（5）与传统方法相比，新方法的计算精度较高，进行结构噪声控制时，新方法的计算工作量小、锁定关键结构局部容易、获得满意的降噪效果耗费时间短，能够弥补传统方法存在的缺陷，从而为车内低频噪声的快速、有效控制提供一条切实可行的新思路。