Temperature-corrected electrical resistance in fatigue life prediction methods for higher testing frequencies

For the adequate characterisation of the fatigue behaviour regarding higher testing frequencies, an accurate differentiation between frequency- and temperature-related influences on the fatigue life is of great importance. To enable such a distinction, the temperature dependence of the electrical resistance was quantified using electrical resistance-temperature hysteresis measurements. The obtained parameter served as input for the evaluations regarding the fatigue behaviour. Based on these insights, a temperature-dependent electrical resistance value can be obtained, which enables the determination of a temperature-corrected electrical resistance. Since this value is characterized by a high sensitivity regarding microstructural changes, it is well suited to be integrated into the lifetime prediction method StressLife. As a result, the applicability of the accelerated lifetime prediction for increased testing frequencies could be shown for the first time. A further major objective of this work was to quantify the frequency effect on fatigue properties of the investigated ferritic-pearlitic steel SAE 1045 (C45E, 1.1191). The estimated temperature-corrected electrical resistance was used as a microstructure-dependent parameter for the assessment of fatigue behaviour. In addition, the residual stress state was quantified by X-ray diffraction investigations and correlated with the results of cyclic deformation curves.