Determination of dissipated Energy in Fatigue Crack Propagation Experiments with Lock-In Thermography and Heat Flow Measurements

摘要

Lock-in thermography and heat flow measurements with a new developed peltier sensor have been performed during fatigue crack propagation experiments. Lock-in thermography allows space-resolved measurements. Moreover elastic stress fields (E-Amplitude) as well as dissipated energies (D-Amplitude) can be determined. In case of thermographic measurements the specimens have to be painted to enhance the emissivity, but the thickness of the coating influences the results and therefore quantitative measurements are problematic. The heat flow measurements are easy to perform and provide quantitative results, but only integral values in an area given by the size of the peltier element can be achieved. In order to get comparable results the evaluation of the thermographic measurements were performed in the same area as the peltier measurements. In case of the mean temperature measured by thermography and the heat flow determined with the peltier sensor a good agreement was found. The measurement of elastic stresses with the peltier sensor is restricted to low loading frequencies due to the response characteristic of the sensor. For the measurement of dissipated energies the cooling of the specimen by heat conduction into the clamps and heat radiation has to be taken into account.