Issue 38

M. Kepka et alii, Frattura ed Integrità Strutturale, 38 (2016) 82-91; DOI: 10.3221/IGF-ESIS.38.11 82 Focussed on Multiaxial Fatigue and Fracture Structure service life assessment under combined loading using probability approach Miloslav Kepka, Miloslav Kepka Jr. University of West Bohemia in Pilsen, Regional Technological Institute – Research Center of the Faculty of Mechanical Engineering, Univerzitni 8, 306 14 Pilsen, Czech Republic kepkam@rti.zcu.cz, http://www.rti.zcu.cz/00-420- 37763-8700 kepkami1@rti.zcu.cz, http://www.rti.zcu.cz/00-420- 37763-8736 Jan Chvojan, Jaroslav Václavík Research and Testing Institute Pilsen, Tylova 1581/46, 301 00 Pilsen, Czech Republic chvojan@vzuplzen.cz , http://www.vzuplzen.cz/00-420-37985-2193 vaclavik@vzuplzen.cz, http://www.vzuplzen.cz/00-420-37985-2162 A BSTRACT . This article presents a basic research approach for probabilistic assessment of vehicle structure fatigue endurance under multiaxial loading. One representative welded structural detail of the bottom joint plate of an articulated bus was selected for the case study. The character of the loading on the joint during a service test is analyzed and discussed. The methodology for estimation of the damage level in the joint builds on deterministic procedures for railway vehicle assessment based on shear, longitudinal and transverse stress components. This approach based on the equivalent stress and particular load capacity factors was expanded to include the probabilistic perspective. K EYWORDS . Service life; Combined loading; Damage; Vehicle; Probabilistic approach. Citation: Kepka, M.., Kepka, M. Jr., Chojan, J., Václavík, J., Structure service life assessment under combined loading using probability approach, Frattura ed Integrità Strutturale, 38 (2016) 82-91. Received: 16.05.2016 Accepted: 22.06.2016 Published: 01.10.2016 Copyright: © 2016 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 n-service loads acting on components and structural details in vehicles tend to be complex and, in most cases, multi- axial and time-variable. The stress response to such loads can (but need not) be multi-axial. Critical locations in vehicle structures are subjected to fatigue loading which can lead to initiation of fatigue cracks, fatigue crack propagation and, sometimes, to final failure. Even today, sizing and assessment of such critical locations often involves the deterministic approach. This means that both loading and strength are represented by their mean values for which adequate safety factors are sought. In the following, a description is given of fatigue lifetime assessment of a welded joint operating under relatively complex loading in an articulated bus. The engineering approach which is normally used in technical practice has been expanded I