StressLife: A Short-Time Approach for the Determination of a Trend S-N Curve in and beyond the HCF Regime for the Steels 20MnMoNi5-5 and SAE 1045

Abstract

Within the scope of this research, a new short-time procedure designated as StressLifeHCF 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 StressLifeHCF calculation. Furthermore, two additional variations of the StressLifeHCF 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).

Assessing and Forecasting Fatigue Strength of Metals and Alloys under Cyclic Loads

“…These data represent the fatigue experiment results obtained by different authors, who carried them out in order to determine the physical fatigue limit position in the high-cycle part of fatigue curve (Figure 21 [9]). The resulting generalized dependence of normalized (recalculated) fatigue parameters can be used as part of a method for the accelerated construction of fatigue curves, which solves the same problems as methods for accelerated construction of fatigue curves discussed in [1, 7,8,[32][33][34][35][36][37]. By choosing relatively high stress levels and performing fatigue tests on several samples, it is possible to determine the angle of inclination of the tangent of the fatigue curve's left branch to the axis of the number of stress cycles.…”