Ultrasonic time domain techniaque for frequency dependent attenuation measurement for microstructural characterization of a titanium alloy

Abstract

The backwall echo in the ultrasonic pulse echo technique consists of more than one peak. The ratio of these peaks changes as the ultrasonic waves travel through the specimens with different attenuation. The ratio of the first two peaks in the first backwall echo (the time domain peak ratio) has been used as an ultrasonic parameter for microstructural characterization in Ti-4.5Al-3Mo-1V (VT14). The time domain peak ratio has been found to vary linearly with the ratio of the two peaks in the autopower spectrum (the amplitude of the lower frequency peak to that of the higher frequency peak), the spectral peak ratio. The time domain peak ratio is found to be independent of the coupling condition, thus enhancing the reliability of its usage. Further, it has also been shown, both mathematically and graphically, that the linear correlation between the time domain peak ratio and the spectral peak ratio is valid for any transducer exhibiting double peak behavior in the autopower spectrum.