A VCCT APPROACH OF CRACK PROPAGATION IN RAILWAY WHEELS Tamás Máté Péter T. Zwierczyk Department of Machine and Product Design Budapest University of Technology and Economics 0ĦHJ\HWHP UNS. 3., H-1111, Budapest, Hungary E-mail: mate.tamas@gt3.bme.hu KEYWORDS Railway wheel, RCF - Rolling Contact Fatigue, Crack propagation, Thermal cracks, FEM - Finite Element Method, Ansys, VCCT – Virtual Crack Closure Technique ABSTRACT In this paper, Rolling Contact Fatigue (RCF) crack propagation in the case of a railway wheel was studied in the presence of significant thermal loading. The complexity of the phenomena and the several assumptions and boundaries of the existing crack propagation modeling methods induce particular difficulties in the creation of this specific kind of contact problem. The primary purpose of the investigation was to reveal the relevancy of the Virtual Crack Closure Technique (VCCT) to see the further implementation opportunities and capabilities of the technique in solving railway RCF based problems. INTRODUCTION During the operation of railway vehicles, several reasons can cause wheel and rail failures, which can have a significant effect on passenger comfort and, in a worse case, on the safe operation. Consequently, continuous monitoring is required to be performed to reveal the potential source of failures. Many principles of maintenance rules are in daily use, but none of them are proved scientifically. These, rather practically defined norms, can result in inaccurate timing and also in the unnecessary scale of the maintenance, which significantly increases the costs. Furthermore, latency also can occur in the required maintenance, which can result in more severe damages that influence the operation and cause delays so indirectly affect the costs. This investigation is a part of my research which goal is to develop a finite element crack propagation model that is able to model specific failure forms in well- defined circumstances to provide more accurate information in order to specify maintenance instructions. In this investigation, the Virtual Crack Closure Technique (VCCT) (Krueger et al., 2013; Pirondi et al., 2015) is scoped and studied to reveal the relevancy in modeling such a complex phenomenon as the contact problem between the rail and the wheel. The study supposed an intensive braking situation when the stick-slip phenomenon could occur, which causes undesirable high thermal loads on the wheel tread. In the case of those vehicles that are equipped with the Wheel Slide Protection system (WSP), more severe temperatures can arise in some specific hot- spots. This thermal load makes to expand the wheel surface and the thin inner volume under the surface as well (Zwierczyk and Váradi, 2014). The heat expansion and the following rapid cooling make destructive residual stresses in the material, which raises the complexity of the stress situation and the understanding of the crack propagation. VIRTUAL CRACK CLOSURE TECHNIQUE The VCCT is based on the assumption that the energy needed to separate a surface is the same as the energy needed to close the same surface. It was initially developed to calculate the energy release rate of a cracked body. Since then, it is widely used in case of investigating interfacial crack-growth or delamination. This method uses interface elements to simulate the fracture by separating the interface elements along a predefined path according to one or more user-specified fracture criteria, for example, the critical energy release rate. (“VCCT-Based Crack- Growth - ANSYS,” Ansys - Help) Advantages: x Several fracture criteria are available, including a user-defined option. x Multiple cracks can be defined in an analysis. x The crack can be located in the material or along with the interface of the two materials. Assumptions: x Crack growth occurs along a predefined crack path. x The path is defined via interface elements. Communications of the ECMS, Volume 34, Issue 1, Proceedings, ©ECMS Mike Steglich, Christian Mueller, Gaby Neumann, Mathias Walther (Editors) ISBN: 978-3-937436-68-5/978-3-937436-69-2(CD) ISSN 2522-2414