A sonic Infra Red technique uses a short pulse of high power sound of 15- 40 kHz to excite an object [1,3,5,9,10]. With the help of infra red cameras this technique detects the change in surface temperature during excitation [1,3,5], which highlights the cracks in the sample under observation. In this study a finite element method has been developed for different crack scenario simulating the SIR technique. The parameters and setting are modeled according to the experimental set up to maintain consistency. The study was carried out on a titanium alloy and modeled as a simple geometry. The objective of this study was to understand the behavior of different cracks classified under two categories of surface and edge (open and closed) cracks. These cracks were further divided into four different crack lengths, to develop a correlation with crack lengths. The evaluation and investigation was carried out by determining the waveform of the motion at crack along the three principle axes and by studying the frequency spectrums. These data's were supported by thermal analysis to determine the temperature change along the crack. Focus was laid on three parameters as the driving factors for surface heating near the crack.
After a detail evaluation of these parameters for different crack geometries, a correlation between the crack geometry and relative velocity, force and frequency spectrum was developed. It was found that the edge cracks experienced higher surface temperature change than surface cracks because of the high out-of-plane relative motion and force between the crack faces. Also considering the different crack lengths, it was found that longer cracks experienced higher frictional heating between the surfaces that small lengths.
