Calibration Techniques for Non-contacting Force Excitation Part 1: Frequency Domain Methods
Experimental characterization of the higher frequency modes of a structure presents challenges due to the frequency limitations of traditional excitation techniques. Non-contact excitation via low power ultrasonic transducer presents the possibility of exciting higher frequencies not currently possible with shakers or impact hammers. However, quantification of the actual force applied by the ultrasonic transducer requires that a relationship between the ultrasonic pressure field and the voltage driving the transducer be established.
In part 1 of this paper, calibration techniques shall be explored using spectral domain techniques with conventional instrumentation before extending the techniques to the ultrasonic transducer. Frequency response functions generated from uncalibrated excitation transducers shall be compared with those generated from calibrated equipment to determine an appropriate sensitivity for the uncalibrated transducers. Reciprocal measurements shall also be examined as a means of calibrating transducers. Time domain techniques for calibration shall be examined in part 2 of this paper.
KeywordsNon-contact excitation High frequency excitation Non-intrusive excitation Ultrasonic transducer Calibration methods
Some of the work presented herein was partially funded by NSF Civil, Mechanical and Manufacturing Innovation (CMMI) Grant No. 1266019 entitled “Collaborative Research: Enabling Non-contact Structural Dynamic Identification with Focused Ultrasound Radiation Force.” Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the particular funding agency. The authors are grateful for the support obtained.
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