In this thesis the thermal behaviour under elastic plastic stress of the stainless steel X2CrNi19-11 and oxygen free copper with Lock-In thermography was examined. The focus was the acquisition of the thermoelastic effect and dissipative temperature changes as well as their separation with thermographic methods in particular the Lock-In thermography. Therefore, a Lock-In method based on a discrete Fourier analysis was developed and used for the analysis of the thermal behavior. Influences caused by specimen motion were eliminated by a software-based motion compensation technique. The thermal behavior under uniaxial elastic loading caused by the thermoelastic effect in single tensile and cyclic loading was found to be equivalent. The corresponding measured thermoelasitic constants were independent of the investigated stress ratio, maximum load and the loading frequency. Under elastic plastic loading a nearly independent superposition of thermoelastic temperature changes and dissipative temperature changes was visualized. Thermoelastic changes were eliminated by the thermoelastic basic equation with knowledge of the actual stress. The remaining dissipative temperature changes could be traced back to plastic deformation. A description of the temperature rise with stress and strain data was achieved for steel and copper. A separation of the superposed thermoelastic effect and the dissipative effects with modal filtering of the Lock-In method is not possible, because the E-Mode consists of thermoelastic and dissipative parts. A modified separation by splitting the E-Mode by a constant separation factor is only possible in a limited number of special cases. A determination of temperature-force-hystereses based on a frequency synthesis of the different modes of the Lock-In evaluation can be carried out on precracked specimen. The comparison with temperature-force-hystereses of an analytical evaluation showed very good accordance. The description of the hysteresis by using only the E- and D-Mode leads to an approximate match. An enhanced adaption can be achieved by using all significant higher Modes (D1, D2, etc.). The compensation of the thermoelastic effect with force proportional local stress changes uncovers the dissipative temperature behaviour at the crack. On basis of the determined local stress changes the stress distribution in front of the crack was determined, showing a good accordance with the theoretic values. A simple isolation of the stress change or rather the dissipative temperature changes out of the E-Mode and D-Mode is not generally possible. Crack opening and compressive loads cause thermoelastic temperature changes, which also affect unneglectable parts in higher Modes (all D-Modes).    «

In this thesis the thermal behaviour under elastic plastic stress of the stainless steel X2CrNi19-11 and oxygen free copper with Lock-In thermography was examined. The focus was the acquisition of the thermoelastic effect and dissipative temperature changes as well as their separation with thermographic methods in particular the Lock-In thermography. Therefore, a Lock-In method based on a discrete Fourier analysis was developed and used for the analysis of the thermal behavior. Influences caused...    »