Ultrasonic instrument to predict drawability of sheet metal

Abstract

An ultrasonic instrument has been designed and fabricated to predict drawability of sheet metal. Using S/sub 0/ mode Lamb waves generated and detected by EMATs (electromagnetic-acoustic transducers), the instrument automatically measures ultrasonic phase delay in three directions: 0 degrees , 45 degrees , and 90 degrees with respect to the rolling direction. The delay is measured by a Fourier transform phase-versus-frequency slope algorithm applied to flash AD recorded EMAT signals. From the delays, the computer-based instrument calculates velocities and the directional Young's modulus E(O) in the rolling plane. From the average E in the plane, a correlation curve is used to find the average plastic strain ratio, which is the drawability prediction parameter.<>