Thickness characterization of refractory linings by low-frequency ultrasonic waves

摘要

Abstract: In this work we describe a method to measure the thickness of refractory lining of cigar shaped cars for the transportation of melted cast-iron, based on the pulse-echo technique at very low frequency. Following this approach two main problems arise related to the small dimensions of the transducers in respect to the US wavelength: a poor directivity of the bulk wave and the presence of a strong surface wave. An improvement of the S/N ratio at the receiver input is obtained by using two unimodal transducers, one transmitter and one receiver, while the time discrimination between the bulk and the surface waves is obtained by taking advantage of the different wave velocities and by properly choosing the distance between the two transducers. !6