低阻尼板结构模态密度测试方法

导纳实部平均值法是主要的模态密度测试方法，理论上导纳实部是在连续频率上进行平均的，实际测试中通常是在离散频率点上近似平均的，但低阻尼结构各模态半功率点带宽较窄，模态重叠因子不高，若测试分析仪谱线间隔过大，则无法测得完整的导纳曲线，因此这种近似精度也不高。就低阻尼板结构模态密度测量中，用离散频率点导纳平均实部代替连续频域平均和有限测量点的平均值代替连续空间平均的精度分别进行了探讨，着重分析了实验测量精度与导纳分析仪谱线分辨率和测量点数之间的关系，并应用导纳分析仪的频谱细化功能成功测得了一块低阻尼板的模态密度。

THE MODAL DENSITY TESTING METHOD OF A LOW DAMPING PLATE

Modal density testing by averaging the real part of mobility is the primary modal density testing method.There are problems when applying this theory to the measurement of the modal density of a low damping plate.In theory the averaging of the real part of the mobility is carried out in two continuous variable domains,one is frequency and the other is location.But in reality the averaging of the real part of mobility is carried out on discrete frequency points and testing positions.For a low dampig structure the half-power bandwidth is narrow and the modal ovelap factor is low,so the mobility curve can't be got completely when the spectral line interval is too broad.The averaging on discrete points is unbelievable too.The accuracy of replacing the averaging in continuous domain with the discrete domain is discussed in this paper,and the influence of the spectrum line interval and the number of testing point on the accuracy of testing result is studied.Base on those studies,the modal density of a low damping damping plate plate is accurately measured by the spectral zoom operation.