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Effects of thickness and gain on the amplitude of airborne ultrasonics

Cheng-Kung Liu, Nicholas P. Latona
Journal of the American Leather Chemists Association 2014 v.109 no.3 pp. 70-74
cluster analysis, leather, nondestructive methods, product quality, ultrasonics
Currently, hides and leather are visually inspected and ranked for quality, usable area, and sale price. However, visual inspection is not reliable for detecting defects, which are usually hidden inside the material. Development of a non-contact nondestructive method to accurately evaluate the quality of hides and leather is urgently needed. We previously reported the research results for airborne ultrasonic (AU) testing using non-contact transducers to evaluate the quality of hides and leather. The ability of AU testing was demonstrated for revealing defects in hides and leather that were difficult to be found during visual inspection. We also reported results on AU inspection using a statistical data/cluster analysis technique, in which leather and hide defects were depicted as color-coded amplitude maps, or “C-scans.” Recently new research was carried out to study the effects of transducer frequency, thickness of leather, and AU gain on the resultant AU amplitude received, that was shown in a C-scan imagine. Observation showed that a lower frequency of 100 KHz yielded better transmission of AU waves through samples and the AU gain should be less than -5dB. In addition the amplitude of the C-scan decreased with the thickness of the samples. This study has provided a significant guidance for successful AU testing.