Characterization of fatigue response using infrared thermography on a structural steel

Fatigue response was evaluated using an Infrared thermographic technique in a structural steel to study the elastic, elastic-plastic response of the material. Both elastic loading (typical of high cycle fatigue) and elastic-plastic loading (low cycle fatigue) was applied. The temperature profile of the specimen was found to be having three distinct regions - initial steep rise in temperature as a function of cycles (region 1), stable response (region 2), steep increase in temperature at about the failure cycles (region 3). Increased test frequency results in higher temperature for region 2. The slope of the region 1 was found to be similar in case of complete elastic loading; however, in case of elastic-plastic loading, the slope differs as a function of spent life of the specimen. Thus, thermographic technique can be used to characterize the extent of fatigue damage in a material for elastic-plastic loading conditions (typical of low cycle fatigue).