Method and apparatus for characterizing surface flaws utilizing ultrasonic surface waves

摘要

Disclosed is a method for determining the length of a surface flaw in an object, including the steps of generating a directional beam of ultrasonic waves on the surface of the object toward the flaw and at an angle &thgr; with respect to the normal to the direction of the flaw, measuring the intensity of the waves reflected from the flaw, at an angle &thgr;' with respect to the normal, as a function of frequency, and calculating the length 1 of the flaw according to the formula 1=n V.sub.R /[f.sub.n (Sin&thgr;+Sin&thgr;')] where n is a integral number defining the order of the frequency minimu, V.sub.R is the speed of the surface waves in the object, and f.sub.n is the frequency at which a minimum of intensity occurs. Also disclosed is an apparatus for evaluating a surfacae flaw in an object including a transducer for inducing ultrasonic surface waves, a signal generator driving the transducer, a deteactor for responding to reflected waves, an amplifier to boost the detector response, a spectrum analyzer to measure the intensity of the reflected waves as a function of frequency, and a gating device to apply the output of the amplifier to the spectrum analyzer durng a predetermined time interval.