1.对模态试验应用,什么是正确的激振力大小?

模态激励的普遍问题

The excitation levels for modal testing are usually reasonably low. There is no need to provide large force levels for conducting a modal test especially if appropriate response transducers (accelerometers) are selected with good sensitivity and resolution, as well as high quality, high resolution (24 bit technology standard in todays commercial offerings) data acquisition systems. The level only needs be sufficient enough to make good measurements. In fact, larger force levels tend to overdrive the structure, exciting nonlinear characteristics of the structure and providing poorer overall measurements than with lower level force tests. For this reason on larger structures, it is often desired to use multiple shakers at lower force levels to more evenly distribute force than a single shaker at a high level.

模态激励的激励幅度通常是相当小的。进行模态试验,没有必要提供很大的激振力水平,特别是如果选择了合适的、具有良好灵敏度和分辨率的响应传感器(加速度计)以及高质量、高分辨率的数据采集系统(24位技术,在今天商业报价中已成标准)。幅值大小只需要足以测得良好的结果就够了。实际上,大的激振力水平比小的激振力试验更容易造成结构过载,激起结构的非线性,得到更糟的总体测量结果。在大型结构上由于这个原因,经常要求使用多个小激振力的激振器以更均匀地分配激振力,而不是用一个大激振力的激振器。