Abstract
A nondestructive detection technique and a high-speed inspection system for a narrow crack appearing at random on a ferrite surface have been developed. When a specimen is sprayed with ethanol, the ethanol on the surface evaporates quickly but the ethanol that has penetrated into a crack evaporates slowly. A crack is recognized by detecting the evaporated ethanol using FID (Flame Ionization Detector). In this system, 66 probes, each with a small area, are settled on to the specimen with narrow gaps between them. The gas on the surface is simultaneously held in 66 containers, each with a small capacity of 1× 10-6 m3. The gas in these containers is led to the FID and the ethanol in the gas is detected. The minimum detectable mass flow rate of ethanol is 5.7×10-10 g/s and the detection time for one container is 0.2s. The experimental results using this system show that the minimum detectable crack width is 3μm, and the expected detection time is 2.2s.
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