Non Destructive Evaluation of Cracks in Porous Building Materials by Use of Crawling Spot Thermal Technique

The infrared (IR) thermography is one of possible tools for the thermal/infrared nondestructive testing (T/INDT). Commonly, it involves quasi-uniform heating of large specimen areas with the choice of heat pulse duration being influenced by specimen diffusivity α and expected defect depth l. The simple estimate of heat transit time τ* is given by the expression which became classical in the T/I NDT theory: τ∗=l2/α