Thermographic Analysis of Fatigue Dissipation Properties of Steel Sheets

Abstract

This paper presents several properties of heat source fields accompanying the highcycle fatigue of a dual-phase steel grade. Heat sources were derived from thermal data provided by an infrared focal plane array camera. An especially developed image processing estimates separately the thermoelastic coupling source amplitude and the mean dissipation per cycle. Our experiments underline that dissipation sources are heterogeneous and this forms the beginning of the fatigue test. They also point out a linear evolution of the mean dissipation per cycle as a function of the loading frequency for a given stress range and a given loading ratio. KEY WORDS: dissipation, fatigue, infrared thermography, steel NOTATION C Specific heat s 2D th Time constant that characterises the perpendicular heat exchanges between front and back specimen faces and the surroundings

Experimental and numerical study of the evolution of stored and dissipated energies in a medium carbon steel under cyclic loading

“…The evolution of the average dissipated energy per cycle W d (determined for the 1 000 th cycle) as a function of the stress amplitude Σ a is plotted in figure 4. As already observed by several authors (Berthel et al, 2007;Mareau et al, 2009;Poncelet et al, 2010), the amount of energy which is dissipated into heat during one loading cycle increases with the stress amplitude. showed that the dissipated energy augmentation is associated with an increase of the plastic activity that can be correlated with the formation of persistent slip bands.…”

Infrared thermography applied to the analysis of material behavior: a brief overview

“…Results of applications to steel and aluminum can be found in [33,34] and more recently in [32] where energy balance distributions were constructed using DIC and IRT techniques. To briefly illustrate the potential of IR image analysis, Figure 7 shows the mean dissipation pattern per cycle The contour plots in Figure 7 also show that areas where the dissipation is high (respectively low) remain approximately the same from one block to another, even though the dissipation naturally increases with the stress range.…”

Thermal method to determine crack nucleation conditions under fretting loading

“…We can assume that the high amplitude at f L is induced by thermoelastic effect then amplitude at 2 f L and the global warming are induced by several dissipative effects like plasticity and friction in the sliding zone of the contact. Among several possible methods, a local least-squares fitting of the thermal signal was considered in this work like in [16] and [20]. The temperature approximation functions account for the spectral properties underlying previously.…”

“…It was also shown that the persistent slip band number increases with the stress and appears to be a relevant fatigue indicator. During a fatigue test on thin flat steel specimen, in [16] it was observed a localisation of the plastic phenomenon on the dissipative field (obtained by an inverse method) until the beginning of the test and the area corresponding to the crack onset is also found to be an area where dissipation was high. This result shows that plasticity observed at a mesoscopic scale and crack nucleation are linked.…”