PSI - Issue 68

J.A. Ziman et al. / Procedia Structural Integrity 68 (2025) 1159–1165 J.A. Ziman et al. / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 2. (a) Experimental setup for fatigue tests with (1) Fatigue specimen; (2) Electricity feed by clamping tools; (3) Kelvin clamps to measure voltage drop; (4) IR-camera; (b) X-ray diffractometer with two fatigue specimens installed in tangential direction; (c) specimen geometry with measurement directions. A slightly modified test setup was used to observe the temperature-dependence of the electrical resistance according to Figure 3. Therefore, an unloaded specimen was heated up to 200 °C with a heating device and the resulting change in electrical resistance R total was recorded synchronously with the temperature increase. An open measurement window ( d = 7.8 mm) in the heating device at the position of the gauge length centre enables temperature measurement on the surface of the specimen with the IR-camera setup. The heating process of the specimen up to 200 °C was followed by a cooling cycle to room temperature. Based on the monitored data, a regression function (second-degree quadratic approximation) according to Harriehausen and Schwarzenau (2019) was used to fit the development of the electrical resistance depending on the change in temperature.

Fig. 3. Experimental setup for the calculation of the electrical resistance-temperature-hysteresis: (1) Fatigue specimen; (2) Electrodes for electricity feed; (3) Stranded wires to measure the voltage drop; (4) Heating device with an adaption for the geometry of the fatigue specimen; (5) IR-camera; (6) Electrical resistance-temperature hysteresis including the fitting curve. This regression function enables a calculation of the temperature-dependent electrical resistance R hys according to equation (7), with ΔT representing the change in temperature in the gauge length centre, α the linear fit parameter, β