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Title: Effects of thickness and gain on the amplitude of airborne ultrasonics

Author
item Liu, Cheng Kung
item Latona, Nicholas - Nick

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2013
Publication Date: 3/1/2014
Publication URL: http://handle.nal.usda.gov/10113/60269
Citation: Liu, C., Latona, N.P. 2014. Effects of thickness and gain on the amplitude of airborne ultrasonics. Journal of American Leather Chemists Association. 109(3):70-74.

Interpretive Summary: At the present time, hides and leather are visually inspected and ranked for quality, usable area, and sale price. Visual inspection is not reliable for detecting defects, which are usually hidden inside the material or under the hair in fresh hides. This manual assessment is not uniform among operators, and often leads to disputes over fair price. Therefore, 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. We demonstrated the ability of AU to reveal defects in hides and leather that were difficult to be found during visual inspection. To perfect AU methods for hides and leather inspection, this 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 an AU color imagine. The research results showed the 100 KHz transducer worked well for leather inspection. This study also showed the AU test results were strongly affected by the sample thickness and AU instrument setting applied to the AU tests. The results will be very instrumental to finalize the development of AU technology for hides and leather inspection.

Technical Abstract: 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.