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Airborne ultrasonic inspection for hides and leather

Liu, Cheng-Kung, Latona, Nicholas P.
Journal of the American Leather Chemists Association 2011 v.106 no.11 pp. 326
leather, nondestructive methods, prices, ultrasonics
Currently, hides and leather are visually inspected and ranked for quality, sale price and usable area. Visual inspection is not reliable for detecting defects, which are usually hidden inside the material. This manual assessment is non-uniform among operators, and often leads to disputes over fair price. Development of a nondestructive method to accurately evaluate the quality of hides and leather is needed. We have investigated airborne ultrasonic (AU) testing using non-contact transducers for the nondestructive evaluation of hides and leather. The AU test system is designed for automated and moving process applications, thereby providing an ideal inspection method for large hides or leather. This research examined the ability of AU to reveal defects in hides and leather that are difficult to be found during visual inspection. The AU transducers were mounted on a computer-controlled X-Y scanner that allows the transducer array to be moved over the entire surface of the hide. The AU testing involves pulsing ultrasonic waves and measuring the amplitude of those waves transmitted through the material. The key for success in AU testing is to use AU transducers with low resonant frequencies, which leads an effective transmission of ultrasound waves through the leather or hides. The variations in the amplitude were colored coded into C-scan images to reveal the location and shape of the defects or some other physical discontinuity that could affect the hides or leather quality. Using AU C-scan images could advance the industry in how it assesses and grades raw hides, wet blue, wet white and finished leather.