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Example 1 - Paint Chip
A 12"x 2"x 1/4" steel specimen coated with a rather reflective white paint was prepared with a rusted paint chip near a fatigue crack. The thermal images below show the emissivity gradient caused by the rust chip. The line plot across the paint chip could be mistaken for a structural flaw in a thermal image.
Heated from the Right
Heated from the Left
The three thermal images and corresponding line plots below demonstrate the ability of the normalized subtraction process to accentuate cracks and minimize false readings at anomalies like paint chips.
Heated From the Left
Heated From the Right
After Subtraction
Notice the difference in the maximum values between the first two line plots and the third. The emissivity gradient caused by the paint chip is almost completely eliminated from the final data by performing the subtraction of the right and left images. The crack, because it impedes the flow of heat from both directions, is accentuated by the subtraction process.
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