3.对模态试验,如何用冲击力锤来确定激振器的恰当位置和对中?

模态激励的普遍问题

The proper locations for shakers are heavily dependent on the frequencies and mode shapes to be extracted. Their location should be at points of adequate displacement in each of the modes of interest. It is common to perform pretest analysis using an impact hammer, like the PCB model 086 series, and an accelerometer to determine suitable active locations at each of the modes of interest. Impact hammers are very convenient because they provide hand-held freedom and flexibility to rove around the structure to test a large number of trial points to get an idea of the structural response. Then shakers can be set up at the necessary locations to adequately observe all of the modes simultaneously.

激振器的恰当位置很大程度上取决于要提取的频率和模态振型。它们的位置应该处在感兴趣的每阶模态都有足够大的位移的点上。利用一把冲击力锤,如PCB 086系列,和一个加速度计进行预试验,来确定感兴趣的每阶模态上的合适的“活动”位置,这种做法非常普遍。冲击力锤非常方便,因为它们提供了手持的自由度和灵活性,在结构上四处漫游,测试非常多的“候选点”以得到理想的结构响应。接下来,可以设置激振器到需要的位置来充分地同时观察所有的模态。

The location of the shaker is called the reference location for a modal test. If an inappropriate location is selected, then some of the modes may not be adequately excited and measured. This is another reason why multiple input shaker tests are conducted. But even with a MIMO test arrangement, much consideration needs to be given to the appropriate shaker reference locations. Suffice it to say that all of the modes need to be adequately excited by the reference location selected.

激振器的位置被称为模态试验的参考点位置。如果选择了不合适的位置,那么有可能不能充分地激起和测量某些模态。这是为什么进行多输入激振器测试的另一个原因。但是,即使是在MIMO试验布置的条件下,也更需要考虑合适的激振器参考点位置。只要说所选的参考点位置充分地激起了所有的模态就够了。