18 G. Corvec et al. 0 100 200 300 400 0 100 D(250,240) C(280,200) A(246,7) B(251,166) 200 300 400 3 S(°C/s) 2 1 0 –1 –2 –3 x (pixels) y (pixels) x x x x Fig. 3.4 Heat source field at a given time Fig. 3.5 Heat source variation (a) at points A and D (b) at points B and C 3.5 Conclusions Thermomechanical characterization of a brittle material has been performed in the case of thermal signals of low amplitude and stress concentrations due to geometrical singularities. A disc of glass containing three elliptical holes has been submitted to a cyclic compressive load to investigate stress and strain concentration. Full thermal field measurement has been performed by using infrared thermography during cyclic loading. The temperature variation images stored during the test were denoised by using a methodology that permits to keep the spatial resolution equal to 1. The framework of the TSA was applied to map the stress field at the surface of the specimen. Experimental results were quantitatively compared with numerical simulation issued from a finite element analysis, which serves as validation of the experimental methodology to process stresses from temperature measurements. Finally, the calorific response of the material has been determined from the heat diffusion equation and the temperature variation field. Its spatial resolution was also equal to 1 pixel. This method should permit to identify mechanical dissipation in case of complex loading conditions, i.e. for which no prediction is possible, as those encountered when the temperature is increased close to the glass transition temperature and the mechanical field is heterogeneous.
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