PSI - Issue 53

Martin Stepanek et al. / Procedia Structural Integrity 53 (2024) 58–64 Author name / Structural Integrity Procedia 00 (2019) 000–000

62

5

3. Fatigue life calculation On the basis of selected (often used) multiaxial criteria, parametric calculations of fatigue life under multiaxial loading were performed and compared with experimentally determined values. Fatigue curves determined for uniaxial loading were used for calculations according to individual multiaxial criteria: ‐ for pull-push � � � , � 2 � � � � (1) ‐ for twisting � � � , � 2 � � � � (2) Several multiaxial criteria were assessed, mostly based on the critical plane approach. In Fig. 6 all used multiaxial criteria are described. These are the same criteria that Chmelko and Margetin (2020), verified on two standard (unprinted) steels with different elastic-plastic properties.

Fig. 6. Multiaxial criteria according to different authors, see References.

Fig. 7 schematically shows the approach to evaluating the applicability of individual multiaxial criteria for investigated materials and tested courses of combined (harmonic) loading. For each selected multiaxial criterion, the calculated and experimentally measured values were plotted in a comparative graph. a) The absolute agreement of calculation and experiment means that the plotted pod lies on the diagonal of the graph. b) A point above the diagonal means that the calculation predicts a higher fatigue life than the experiment. c) A point below the diagonal means the opposite, the calculation predicts a shorter fatigue life than the life achieved experimentally. In Fig. 8 is the summary quantitative evaluation.