Photothermal Length Measurement of Vickers Cracks in SI3N4

The Use of Optical Beam Deflection (OBD) Technique in the Thermal Diffusivity Characterization of Polymer Foils

“…4 shows that the lower the frequencies used, the narrower the variance curves are and thus the better sensitivity can be obtained. This is in agreement with the computer simulation result presented in our previous paper [10].…”

“…The use of a fluid whose thennal diffusivity is as low as possible as the measurement medium increases the thermal diffusivity detennination sensitivity for low diffusivity materials, as was pointed out in our previous theoretical simulation paper [10]. Therefore, C02 was selected for the fluid, and to decrease the gas diffusivity still, its pressure was increased to 2 atm.…”

“…qLis the complex square root of (k 2 -iO)/ul) with the positive real part, u j being the thermal diffusivity of gas surrounding the sample and 0) being the angular frequency of the heating mooulation. A general description for the computation of g(k) for a layer-structured sample is given in one of our previous papers [10].…”

“…This is because either no zero-crossing exists or the signal level at the zero-crossing point is so small that noise makes its accurate determination impossible [9]. Therefore, the thermal diffusivity of the sample has to be calculated from the entire mirage measurement data, which contains information of the thermal properties of both the sample and the gas, and the measurement parameters [10]. A suitable data analyzing method is multi-parameter least-squares regression fitting developed by Kuo et al that has already been successfully applied to the thermal diffusivity determination of diamonds [4].…”