Sensing characteristics of contact-type transducer for flexural waves

For the purpose of understanding and improving the stress wave factor technique and the travelling wave control method, the sensing characteristics of contact-type transducers for flexural waves are investigated in this paper. Two kinds of frequency response functions (FRF) are presented to characterize the transducer sensing results: one is for any harmonic plane wave, and the other for any point source disturbance. The two FRF are both expressed in the form of explicit physical interpretations which distinguish the influences from the transducer itself and from the tested structure. Based on this, three characteristic lines about the FRF are presented: one is a scattering line which means the FRF is dominated by the nature of wave scattering or wave reflection, the other two are transducer's mass and spring lines which imply the transducers properties dominate the FRF. Using these three lines, the difference between general ultrasonic transducers and general vibration transducers can be clearly identified. Finally using the fast Fourier transform (FFT) technique, some typical time domain numerical results of the transducer output are also presented to show some important sensing characteristics.