Nondestructive Evaluation (NDE) Exploratory Development for Air Force Systems. Delivery Order 0006: Paint Stripping Effects on Fluorescent Penetrant Inspection

摘要

Paint removal is required before conducting fluorescent penetrant inspection (FPI). The effects of various pre-inspection paint-removal processes on FPI indications of fatigue cracks were evaluated using 2024-T3 and 7075-T6 aluminum specimens. Comparative data was obtained by conducting FPI of the specimens before painting and after paint removal. Nearly all the FPI indications were adversely affected by plastic media blasting. Over 70 percent of the FPI indications of cracks in specimens cleaned with chemical stripper were also adversely affected. Atmospheric plasma was the media least detrimental to the production FPI indications, but additional evaluation of this method is required. Pre-paint and post-strip corollary measurements of eddy current responses from the cracks and of bulk and superficial hardness of stripped surfaces were made. Eddy current signals maintained sufficient amplitudes for reliable crack detection. Minor changes in hardness occurred.