Issue 41

M. Kurek et alii, Frattura ed Integrità Strutturale, 41 (2017) 24-30; DOI: 10.3221/IGF-ESIS.41.04 24 Focused on Multiaxial Fatigue Determination of the critical plane orientation depending on the fatigue curves for bending and torsion Marta Kurek, Tadeusz Łagoda University of Technology - Opole, Poland ma.kurek@po.opole.pl , t.lagoda@po.opole.pl A BSTRACT . This paper contains a proposition setting out a new way of determining an orientation angle of the critical plane. The applied method involves an analysis of fatigue life results’ scatter of several selected materials on the basis of a new criterion of multiaxial fatigue. The expression for the equivalent stress was derived on the basis of pure bending and pure torsion. The paper also contains a verification of the effectiveness of the proposed model by analyzing scatter bands and the value of the ratio of normal to shear stresses. K EYWORDS . Critical plane; Fatigue life; Equivalent stress; Scatter analysys. Citation: Kurek, M., Łagoda, T., Determination of the critical plane orientation depending on the fatigue curves for bending and torsion Frattura ed Integrità Strutturale, 41 (2017) 24-30. Received: 28.02.2017 Accepted: 15.04.2017 Published: 01.07.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he literature contains a number of propositions including models for fatigue life assessment [1-4]. The work aimed at finding an algorithm for predicting fatigue life accompanying random loads was undertaken by Macha in 1979 [5], who applied the notion of stress for this purpose. Over the successive years, the propositions were improved and modified, and each of them accounted for one or a few aspects of the fatigue life. With the time passing, the strain model was established [6], followed by the one based on energy [7], which applied the parameter of strain energy density parameter acting on the critical plane. Despite the large number of propositions, there is still a need to modify the existing models. The justification for the adopted foundations is based on the scatter of the gained calculation results of the fatigue [8]. They form an important factor used for verifying the effectiveness of the proposed way of assessing fatigue strength. The objective of this paper is to present a new model applicable for assessment of fatigue life on the basis of a concept of the critical plane accompanied by the analysis of the scatter of the results. T