| Summary: | The technique of rapid evaluation of fatigue limit using infrared camera is beneficial because it not only allows the fatigue limit to be obtained in a short time and at low cost, but also it makes possible to detect the location of fatigue damage in real structures. In this technique, the fatigue limit is determined based on the temperature evolution with the load amplitude. Several data processing methods have been proposed so far to determine the fatigue limit, but no definitive method has been established yet. In this study, three data processing methods are proposed, namely, a method of selecting pixel to evaluate the temperature evolution, a method of excluding inappropriate data using adjusted R-square, and an approximation function to represent the relationship between the temperature evolution and the load amplitude. As a result, these methods are applied to experimental data and proved to be accurate and reliable enough compared to the existing methods. Experimental data were obtained for double edge notched specimens of type 304 stainless steel. The second harmonic amplitude of temperature was adopted as the characteristic value of temperature evolution for estimating the fatigue limit.
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