Nondestructive Examination of Inside Surfaces of Small Holes in a Steel Structure Using a Laser Scan Technique
Technical Report,01 Jan 2015,31 Mar 2016
Army Armament Research, Development and Engineering Center Munitions Engineering Technology Center Picatinny Arsenal United States
Pagination or Media Count:
This paper describes the application of a commercial off-the-shelf laser-based inspection system to nondestructively examine the internal surfaces of small holes 6 mm in diameter and 19 mm in length embedded in a tubular section made of high strength steel. Methods are developed to analyze the data after correcting for laser probe wander while scanning and applying signal processing techniques to extract the Abbott-Firestone curves of the surface features. The tubular sections were subjected to a safety and reliability test simulating storage conditions to withstand exposure to repeated cycles of extreme temperatures and humidity. The temperature extremes were 71 and -54C, and a relative humidity of 95 was used at 71C. Under these conditions, corrosion was induced in the steel and the formation of pits was suggested by the increase in the surface heights with the number of days of treatment. Further analysis of the pit distributions showed that 1 the pit density decreases monotonically with increasing pit depth, 2 the maximum pit depth beyond which the pit density is negligible increases with the number of treatment days, and 3 for a given pit depth below the maximum, the pit density increases with the number of treatment days. No surface defects such as cracks were observed in any of the sections even after the maximum number of 84 days of treatment.
- Test Facilities, Equipment and Methods
- Lasers and Masers
- Metallurgy and Metallography