Size determination of subsurface defect by active thermography – Simulation research

• We examine temperature on the surface of material with subsurface defect heated externally.
• The segmentation of the temperature profile enables the defect boundary accurately.
• The inflexion point of the temperature profile corresponds to the defect boundary.
• The temperature rise depends on the defect transverse size but not on its depth.

This paper presents the results of 3D numerical simulations of thermal phenomena in uniform material with subsurface defect located at some depth. The material is aimed to be tested by means of IR active thermography. The temperature field of the front surface of material tested is observed and analysed. The results of modelling are suitable for step heating as an external thermal stimulation – heat flux. The heating duration needed for accurately defect sizing is discussed. Also, an effect of two defects with different thermal properties and simultaneously occurring in the material tested is analysed.