Investigation of the characteristics of the low frequency broadband contact transducers

Abstract

In this paper experimental investigation of the characteristics of low frequency ultrasonic broadband contact type transducers is presented. The low frequency transducers are widely used for non-destructive testing and material characterisation, ultrasonic testing and in acoustic emission applications. One of the most important requirements to the low frequency transducers is that their characteristics during long-term contact scanning should not change. In order to measure the beam pattern of the low frequency transducers the special experimental set-up was created. The experimental set-up enables to carry out the measurements of the beam pattern of the contact type transducers which is impossible to perform by other (air-coupled, immersion) methods. The characteristics of the beam pattern of investigated different diameter transducers are presented. In the case of using contact type transducers possessing diameter of the contact surface 0.1 mm, the angle of the beam pattern divergence is about 116°. It shows possibility to excite the shear and the Lamb waves in the layered structures. It was determined experimentally, that the most noticeable differences between the beam patterns of the different diameter transducers are at small angles.