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RESEARCH PAPERS

Enhancement Techniques for Ultrasonic Nondestructive Evaluation of Composite Materials

[+] Author and Article Information
S. C. Wooh, I. M. Daniel

Technological Institute, Northwestern University, Evanston, Ill. 60201

J. Eng. Mater. Technol 112(2), 175-182 (Apr 01, 1990) (8 pages) doi:10.1115/1.2903304 History: Received June 09, 1988; Revised January 25, 1989; Online April 29, 2008

Abstract

Conventional ultrasonic C-scanning sometimes produces distorted and degraded images due to a variety of reasons, including surface roughness, beam dispersion, extraneous noise and imperfect fidelity of the total acquisition system. Enhancement techniques, using computer data acquisition and processing, can be used to enhance and restore the image. Enhancement techniques described include contrast stretching and median filtering, histogram equalization, thresholding, dynamic thresholding, thresholding depending on boundary characteristics, one-dimensional segmentation and intensity scans with hidden line removal. These enhancement techniques were applied and illustrated for five different types of damage in graphite/epoxy composite materials: (1) Embedded film patch in quasi-isotropic laminate; (2) impact damage in quasi-isotropic laminate; (3) matrix cracking due to static loading of crossply laminate; (4) fatigue damage in crossply laminate; and (5) thermally induced cracks in a thick crossply laminate. There is no single technique that is optimum in all cases. A suitable combination of techniques must be selected for optimum image quality.

Copyright © 1990 by The American Society of Mechanical Engineers
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