Ultrasonic apparatus and method for measuring wall thickness

Abstract

Disclosed is a method for determining the thickness of an object, including the steps of generating a higher order mode ultrasonic wave at a first location on the object, varying the frequency of the generated wave, and measuring, at a second location on the object, the minimum frequency at which the generated wave will propagate in the object. Where the ultrasonic wave generated is a horizontally polarized shear wave, the thickness t may be calculated from the relationship t=(n V.sub.s)/(2 f.sub.c), where: n is the wave mode number, V.sub.s is the shear wave velocity, and f.sub.c is the minimum propagation frequency. Alternatively, the steps may be repeated for the next consecutive frequency minimum and the thickness t calculated from the formula t=V.sub.s /(2 .DELTA.f.sub.c) where: .DELTA.f.sub.c is the difference between two consecutive frequency minima. An apparatus for performing the method includes a transmitting transducer for generating a higher order mode ultrasonic wave at a first location on the object, a signal generator for driving the transmitting transducer with a variable frequency, a receiving transducer for detecting the wave in the object, an amplifier receiving the signal output from the receiving transducer for boosting the signal, and an indicating instrument for receiving the output of the amplifier.

Dependencies are inferred from the claim text.