Experimental investigation of an ultrasonic spectral method of determining the nature of defects

An ultrasonic spectroscope designed for determining the nature of defects is described. The spectroscope is operational in the 1-10 MHz range. The design includes a synchronizer; probing, modulating, sweep, and delayed-pulse generators; a broadband preamplifier; a calibrated attenuator; high-frequency, broadband, and video amplifiers; a cathode-ray tube; a series-connected detector; and an integrator. Criteria are defined for estimating the nature of both volume and planar defects. On the basis of these criteria 77 natural defects are classified from the spectrograms obtained. Experimental results and theoretical calculations are compared for defects from 2 to 10 mm and good agreement is found.