P2I-4 Experimental Study of the Non Linearity from Ultrasonic Transducers

The quantitative evaluation of the non linearity from a material is a characterization method currently used in various applications such as NDE or medicine. Such a measurement must be performed using a set of devices exempted of non linearity themselves. The purpose of the present work is to investigate the non linear behavior of transducers. A measurement method is proposed to evaluate the second harmonic generation in an ultrasonic transducer submitted to a high electrical excitation. Displacement at the surface of the transducer is measured by a laser probe, while the real electrical excitation is acquired. The method is based on measurement of fundamental and harmonic quantities on the acoustical axis of the transducer for aluminum samples of various thicknesses. The experimental set up includes a high power filter to avoid second harmonic electrical excitation. However, the possibility to take into account the presence of component at twice the fundamental frequency is considered in the proposed method. Then the second harmonic generation due to the loaded transducer itself is compared to the generation in a solid sample