Comparison of thermal impedance and wavelets analysis for non-destructive testing

This paper presents a comparison of two methods used for non-destructive testing: thermal impedance (Zth) and wavelet transform (WT). The transient heating process of a textolite plate with defects was measured using a thermographic camera. Based on the measurement results, a qualitative and quantitative assessment of material structure was performed. The measured parameters describing the geometry of the tested material were temperature, time constant, angular frequency and phase. The presented results of thermographic measurements and their analysis indicate the possibility of detection of subsurface defects using both presented methods. The convergence and the correlation between results obtained using thermal impedance and wavelet methods are presented.