基于PolyMAX的声固耦合模态试验研究

白车身的结构模态频率和模态振型反映了汽车车身结构的固有特性，对车内噪声有重要影响。车内空腔跟车身结构一样，同样拥有模态频率和模态振型。采用LMS数据采集系统对某国产SUV进行车内空腔声学模态试验。首先基于传声器阵列的方法获取响应点的信号，然后利用PolyMAX方法提取声学模态频率及振型。将声学模态频率与白车身结构模态频率进行对比分析，结果表明：车内空腔的第一、二阶声学模态分别跟白车身的第四、十阶结构模态有很强的耦合。最后通过实车测试验证了声固耦合共振时低频轰鸣的存在。可以在关键部件增加板厚、顶盖和地板附加阻尼层、顶盖加加强筋等方式改变车身结构的局部模态来破坏车身结构模态和声腔模态的强耦合状态，降低车内的低频轰鸣声

Acoustic-structure coupled modal test based on PolyMAX

Modal frequencies and modal shapes of the BIW (body-in-white) reflect the inherent characteristics of the automotive body. It has an important influence on the interior noise. The car cavity also has modal frequencies and modal shapes. Acoustic modal experiment of the car cavity on a domestic SUV is carried out by LMS data acquisition system. Firstly, response points’ signals are gained by microphone array, and then acoustic modal frequencies and modal shapes are extracted by PolyMAX method. The compare between the acoustic modal frequencies and the experimental modal frequencies of the BIW implies that the first and the second acoustic modal of the car cavity strongly coupled with the fourth and the tenth structure modal of the BIW. Finally, acoustic resonance is verified through the test during the vehicle running. There are several ways to change the local modal of the automotive structure, such as increasing the thickness of the key components, adding damping layer in the roof and floor, and strengthening the roof with ribs and so on. That these actions can destroy the strong coupling between the modal of the BIW and the acoustic modal of the car cavity, decrease the low frequency boom in the automotive.