High-selectivity imaging of closed cracks using elastic waves with thermal stress induced by global preheating and local cooling

The authors developed a practical method based on the thermal stress dependence of cracks for the accurate imaging of closed cracks with high selectivity. A tightly closed fatigue crack was visualized in linear phased array (PA) images by opening the crack with the tensile thermal stress induced by global preheating and local cooling (GPLC), although the conventional method of using only local cooling could not fully open the crack. Furthermore, by the subtraction of the PA images before and after GPLC, only the closed crack was extracted with high selectivity while canceling the other linear scatterers. (C) 2013 AIP Publishing LLC.