锤击法与激振器法选择对振动特性测试的影响

Effects of Impact and Exciter Testing Methods on the Measurement of Vibration Transmission Characteristics

为了提高测试准确性,本文采用锤击法和激振器法对基座振动传递特性进行测量,并将二者测试结果进行对比,确立了两种方法在实际测试时的选择标准。结果表明,锤击法(较硬锤头)和激振器法下,振动传递函数在100~1000 Hz较高频段的均方根差值通常在3 dB以内,而在10-40 Hz较低频段的差值可达数十分贝,因此,采用激振器法可在10~1000 Hz的全频段内均得到较为准确的振动传递特性;若只需保证100 Hz以上高频传递特性准确度,则可使用较硬锤头进行锤击法测试以使测量简便高效;激励点位置的结构不稳定性会增大锤击法和激振器法测量结果的差异,而测点位置的结构不稳定性则无明显影响。

In order to improve the accuracy of the test,taking a floating raft as researched platform,the vibration transmission characteristics of its foundation bed are measured by employing both impact and exciter testing,respectively,and then comparative analyses are carried out to establish the criteria to testing method selection.Results show that transfer functions obtained from the two methods(a hard hammerhead is used for impact testing)present nearly negligible discrepancies(<3dB)in the frequency range of 100~1000Hz,while a large difference of tens of dB can be found in the low frequency range of 10~40 Hz.Therefore,exciter testing can be adopted to get precise vibration transmission results in the whole frequency range,while impact testing(with a hard hammerhead)can be used only when vibration transmission accuracy is needed at high frequency(>100 Hz).The structural instability of the excitation points may considerably increase the difference between the results obtained from the two methods,yet that of measuring points shows insignificant influence.