ULTRASONIC MEASUREMENT OF TEXTURE IN A THIN ALUMINUM SHEET USING SH AND LAMB WAVES SIMULTANEOUSLY

摘要

This paper combines the measurements of SH and Lamb wave velocities to determine the orientation distribution function (ODF) of a thin aluminum plate, and hence to plot the corresponding ultrasonic pole figure. The relations between the ODF of crystallities and the macroscopic elastic constants of a metal sheet are first briefly introduced. Secondly, the dispersion relations of horizontal polarized shear waves and Lamb waves in a slightly anisotropic thin plate are presented to relate the corresponding velocities with the macroscopic elastic constants. Noncontact electromagnetic acoustic transducers (EMAT) are utilized to measure the angular dependences of the horizontal polarized shear wave velocity and Lamb wave velocity of a thin metal plate. With the ultrasonic wave velocities measured, the elastic constants of a slightly anisotropic thin aluminum plate are determined inversely using a numerical algorithm. The coefficients of the ODF of the aluminum sheet can therefore be calculated, and hence, the ultrasonic pole figures of aluminum thin plate.