Analysis of the defect detection capabilities of pulse stimulated thermographic NDE techniques

The defect detection capabilities of both flash and long pulse excitation thermographic non-destructive evaluation (TNDE) techniques have been obtained using an analytical expression that involves defect size and depth, thermophysical properties and the inspection system excitation energy. The possibility of using long pulse excitation in place of traditional flash excitation is discussed and is considered quantitatively. It has been found that long pulse TNDE becomes an effective alternative where the defect image contrast peak obtained in the flash variant of TNDE occurs at a time that approaches or is greater than a second. Images of defects in aluminum alloy, mild steel, stainless steel and carbon fiber composite obtained by both TNDE techniques are presented.