Identification and correction of force transducer mass effects in modal testing

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