Within the scope of this research, a new short-time procedure designated as $StressLif{e}_{HCF}$ was developed. Through a combination of classic fatigue testing and non-destructive monitoring of the material response due to cyclic loading, a process-oriented fatigue life determination can be carried out. A total of two load increases and two constant amplitude tests are required for this procedure. By using data from non-destructive measurements, the parameters of the elastic approach according to Basquin and the plastic approach according to Manson–Coffin were determined and combined within the $StressLif{e}_{HCF}$ calculation. Furthermore, two additional variations of the $StressLif{e}_{HCF}$ method were developed in order to be able to accurately describe the S-N curve over a wider range. The main focus of this research was 20MnMoNi5-5 steel, which is a ferritic-bainitic steel (1.6310). This steel is widely used for spraylines in German nuclear power plants. In order to validate the findings, tests were also performed on an SAE 1045 steel (1.1191).

Understanding the fatigue behaviour of metallic materials is highly important when it comes to a reliable assessment of material degradation as a result of dynamic loading. Because the provision of such data is associated with great testing effort leading to increased time and cost requirements in terms of conventional methods, accelerated lifetime prediction methods are becoming increasingly important. However, the reduced number of fatigue specimens and tests complicates statistical validations of the obtained results. In this contribution, combinatorial approaches are used to estimate both lifetime prediction bands and virtually-determined S-N curves with a reduced number of specimens, displaying the material-related scatter due to microstructural inhomogeneities. In addition, a variable energy dissipation factor based on cyclic deformation curves is presented, which enables evaluation of materials that exhibit more pronounced scatter, for instance cast materials. An in situ evaluation of the cyclic deformation curves is provided via integration of non-destructive testing methods into the testing rig. Unalloyed SAE 1045 steel, low-alloyed 20MnMoNi5-5 steel, and the cast material EN-GJS-1050-6 are investigated in this research, as these materials posses gradually increasing complexity regarding their respective microstructures.

This research provides a method for a reliable fatigue life estimation at high testing frequencies. The investigations are based on the lifetime prediction method StressLife_HCF considering test frequencies of 80 and 260 Hz for normalized SAE 1045 (C45E, 1.1191) steel. Therefore, load increase tests and constant amplitude tests were carried out using a resonant testing rig. To ensure a mechanism-oriented lifetime prediction, the material response to dynamic loading is monitored via temperature and electrical resistance measurements. Due to the higher energy input per time unit, when the test frequency is increased, the heat dissipation also increases. For this reason, a precise differentiation between frequency- and temperature-related effects for adequate fatigue assessment is challenging. To evaluate the temperature’s influence on electrical resistance, an electrical resistance-temperature hysteresis is measured, and the frequency influence is analyzed by considering cyclic deformation curves. In addition to an extension of the fatigue life due to an increased test frequency, the lifetime prediction method was validated for high frequencies. The generated S-N curves show a reliable agreement with the data points from conventional constant amplitude tests. In this context, the temperature correction of the electrical resistance proved to be an important input variable for a reliable lifetime prediction.

A reliable design of dynamically loaded components requires a thorough understanding of the fatigue properties of metallic materials. This article focuses on extending conventional methods to include non-destructive testing (NDT)-based methods, which enable a process-oriented evaluation of fatigue behaviour instead of a lifetime driven approach. The use of NDT-generated data to describe cyclic deformation curves not only enables a significant increase in information, but also a generation of virtual S-N curves with a significantly reduced number of specimens. Therefore, synergies between the two disciplines of NDT-based and conventional destructive materials testing are used to enable a better understanding of ongoing processes. The main focus lies on the development of thermographic evaluation approaches, whereby further methods such as resistance measurements are used additionally. The test materials are two unalloyed steels of grade SAE 1020 and SAE 1045, as well as the low-alloyed 20MnMoNi5-5 steel.

The reliable evaluation of the fatigue behaviour in metallic materials is essential for ensuring structural integrity and resource-efficient design. Unlike conventional methods, non-destructive-based approaches enable early-stage damage detection and continuous monitoring. This study presents an advanced methodology for multiparametric fatigue characterisation based on hysteresis measurements of mechanical, thermal, and electrical signals. In addition to stress–strain hysteresis, temperature and electrical resistance hysteresis provide sensitive indicators of microstructural evolution and material degradation processes under cyclic loading. Experimental investigations using load increase tests demonstrate the capability of these methods to detect early damage mechanisms and estimate fatigue strength efficiently. The combined analysis of multiple NDT-based signals significantly enhances the robustness and accuracy of an individualised fatigue assessment. The results highlight the strong potential of hysteresis-based approaches for accelerated lifetime prediction and their applicability in both research and industrial environments.