Issue 33

M.Kurek et alii, Frattura ed Integrità Strutturale, 33 (2015) 302-308; DOI: 10.3221/IGF-ESIS.33.34 302 Focussed on multiaxial fatigue Estimation of fatigue life of selected construction materials under cyclic loading M. Kurek, T. Łagoda Opole University of Technology, Poland ma.kurek@po.opole.pl, t.lagoda@po.opole.pl S. Vantadori University of Parma, Italy sabrina.vantadori@unipr.it A BSTRACT . In the literature, there are many criteria of multiaxial fatigue. They are based on various assumptions and parameters describing the process of fatigue. Among them, there is a special group of criteria based on the concept of critical plane. Some of them in their equations take into account the ratio of normal and shear stresses. Macha has formulated the criterion of maximum normal and shear stress in fracture plane which can be generalised for the scope of random loading of numerous criteria. In the present study authors estimated the fatigue life of several construction materials. For the purposes of the analysis, the authors proposed modified Carpinteri et al. method to find orientation of critical plane, which is used in multiaxial fatigue criterion defined in critical plane. This plane is turned through the angle of β in relation to the plane defined by maximum normal stresses. In this study authors analyzed the variability calculation of fatigue life, depending on the angle β. Simulation studies were conducted in which it was assumed that β  <0°, 45°>. For each of the 46 angles, we calculated parameters B and K appearing in the formula defining equivalent stress. Then we calculated fatigue life according to the proposed model for each of the obtained angles β. Fatigue life analysis was carried out in order to verify which angle β gives the most similar results. K EYWORDS . Fatigue life; Multiaxial criteria. I NTRODUCTION he phenomenon of fatigue of materials and structures is a significant issue of the day. Fatigue occurs in various fields of industry, i.e. aerospace, machinery, mining or transport. The main objective of the bulk of research on predicting the fatigue strength is to identify a method of estimating the fatigue strength already on the stage of design and construction of components of machines and devices. The fatigue criterion in multiaxial loading is based on establishing such equivalent value that would enable comparison of multiaxial load with uniaxial loading. Literature of the subject provides a number of multiaxial fatigue criteria [6]. Such criteria are based on various assumptions and parameters of the fatigue process. A separate group of criteria among them are based on the critical plane concept [4]. Some of the criteria include the ratio of bending fatigue to torsional fatigue. The paper discusses estimation of fatigue strength depending on the changing orientation of the critical plane of proportional torsional bending for specific construction T