Characterization of Metal Smear in Consideration of Pre-Penetrant

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Characterization of Metal Smear in Consideration of Pre-Penetrant Powered By Docstoc
					Number:     384

Title:      Characterization of Metal Smear in Consideration of Pre-Penetrant Etch
            Requirements
Authors:    Julie Henkener and Charles Salkowski
Citation:   Nondestructive Evaluation of Aging Aircraft, Airports, Aerospace
            Hardware, and Materials, Proceedings of SPIE Vol. 2455, pp 431-438, 6-8
            June 1995
Keywords:   Etching, Cracks, Corrosion

Abstract:   A controversy exists within the aerospace community as to whether etching of
            components before dye penetrant testing to remove metal smear is always
            necessary. A test program was initiated to detect the degree of metal smear
            present in aluminum alloy 2024- T851 after machining by various techniques. Use
            of the scanning electron microscope confirmed the presence of metal smear. In
            addition, dye penetrant tests were performed before and after a chemical etching
            process that removed approximately 0.0005 in. It was determined that etching
            always improves flaw detectability, even for cracks that have not been smeared.

Pro/Cons:   Most interesting was the fact that etching improved penetrant indications even
            when compared to unmachined baseline crack indications. Future efforts can be
            focused on the statistical probability of detection for unetched flaws compared to
            etched flaws.

				
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