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Weight-optimized component design as well as a reliable estimation of the lifetime of metallic materials and components requires a comprehensive understanding of fatigue processes and a systematic investigation of the underlying fatigue behavior. Therefore, nondestructive testing methods, digitalization of measurement techniques as well as signal processing can be combined with a short-term procedure in order to acquire potentially more information about fatigue processes, while experimental effort and costs are reduced significantly. This leads not only to considerable advantages over conventional methods for determining S-N curves, but also over established short-term procedures, due to the possibility of applying this information from just a few specimens to attain fatigue life calculations. The StressLifetc approach is a new short-term calculation method which considers the nonlinear relation between the elastic, elastic-plastic and plastic portion of the material response in the deformation process. Within the scope of the present work, the change in temperature of SAE 1045 (C45E) specimens was measured during fatigue tests via an infrared camera in order to feed the thermal response back into the new StressLifetc approach for a reliable fatigue life calculation.
The service life of materials and components exposed to repeated mechanical loads is
limited, which is why the understanding of the damage evolution and estimating its fatigue life is of
high importance for its technical application. This paper shows how temperature and magnetic field
measurement methods can be used to describe the cyclic deformation behaviour of metallic materials
and to derive parameters from this, which are used in short-term methods to calculate the fatigue
life. Within the SteBLife (stepped-bar fatigue life) approach, only three to five fatigue tests with a
stepped fatigue specimen are required to determine a complete S–N or Woehler curve with scatter
bands for different failure probabilities. If only a trend S–N curve is required, the number of tests
can be reduced to a single fatigue test only. In the framework of this paper, these approaches will be
presented for normalised SAE 1045 (C45E) and quenched and tempered SAE 4140 (42CrMo4) steels.