Influences of tensile direction and plastic strain on ultrasonic parameters measured with rolled brass plates

Abstract

Cu-40 wt% Zn alloy plates were pulled parallel or perpendicular to the rolling direction and ultrasonic measurements were carried out with a probe generating shear wave of 4 MHz in frequency polarizing parallel or perpendicular to the tensile direction to examine the relationship between ultrasonic parameters, tensile direction and plastic strain. Ultrasonic echoes reflected from the bottom of specimens were Fourier transformed and an inverse transfer function was obtained as a ratio of the Fourier spectra of the first two echoes. The inverse transfer function changed complicatedly with plastic strain, and was analyzed with the subspace method to obtain a major parameter called the primary component. The primary component changed with the plastic strain, and was dependent on combination of the polarization direction of the shear wave, the rolling direction and the tensile direction. Specimens with curved sides were pulled and the primary component was obtained by the ultrasonic measurement to estimate the plastic strain distribution in specimens with the ultrasonic parameter. The estimated plastic strain was in good agreement with the measured plastic strain.