Identification and correction of force transducer mass effects in modal testing

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Journal of Vibration and Shock ›› 2014, Vol. 33 ›› Issue (14) : 108-112.

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Identification and correction of force transducer mass effects in modal testing

REN Jun，BI Shu-sheng

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Abstract

The measured Frequency Response Functions (FRFs) are usually inaccurate due to the force transducer mass loading effects in shaker modal testing. And the quality of the extra mass (of the transducer) contributing to the test is generally unknown to us all. A method for the identification and correction of extra mass of the transducer based on the measured FRFs is investigated. Firstly, the changes of the structure’s FRFs due to the additional mass are analyzed and a general formula for expressing the additional mass using the measured FRFs is derived. Then, the method is verified with case studies using simulated experimental data. Finally, modal testing of a simple supported beam is conducted using shaker and Laser Doppler vibrometer. And the additional mass of force transducer is identified using two point FRFs and two transfer FRFs of the beam. It should be noted that the exactness of identification is largely depended on the accuracy of the measured FRFs while the FRFs in some frequency bands are often heavily contaminated by the noise in a practical testing. However, a significant advantage of this method is that the calculation does not rely on the full-band data. Therefore, in practice certain frequency bands in which all four FRFs have a high quality can be selected for the calculation and the accuracy of identification will be improved.

Key words

modal testing / force transducer / additional mass effects / frequency response functions (FRFs) / laser doppler vibrometer

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REN Jun;BI Shu-sheng. Identification and correction of force transducer mass effects in modal testing[J]. Journal of Vibration and Shock, 2014, 33(14): 108-112