PSI - Issue 48

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000–000

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Procedia Structural Integrity 48 (2023) 142–148

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IRAS 2023 organizers 10.1016/j.prostr.2023.07.140 UIC parabolic leaf springs are made of chromium-vanadium alloyed steel. These springs are quenched and tempered, giving them high mechanical strength and hence a higher fatigue strength (Gomes et.al., 2022). Figure 1 illustrates the parabolic leaf spring geometry normalized by UIC for application in two-axle freight wagons. This type of leaf spring is constituted by 5 leaf springs, 4 of which constituted the main leaf spring. The fifth leaf spring is called an auxiliary spring and serves to increase suspension stiffness for high loads. As can be seen in Figure 1, the leaf spring is constituted by leaves of constant width, but with varying curvature and thickness. © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IRAS 2023 organizers Abstract Parabolic leaf springs applied in freight wagons are standardized by the International Union of Railways, UIC. According to the UIC, parabolic leaf springs must be stress peened after quenching and tempering in order to produce a compressive stress state on the surface to improve the fatigue strength. After heat and mechanical treatments, spring leaves are assembled. Due to distinct curvature radius of spring leaves, they are pre-stressed, introducing another type of initial stress state in the spring leaves. In order to quantify the initial stress state in UIC parabolic leaf springs, two types of experiments are performed. The stress relief method and the X-ray diffraction method are performed to analyze the assembling stresses and residual stresses by stress shot peening respectively. The superposition method is considered to estimate a corrected fatigue limit encompassing the material fatigue limit and the effect of the initial stress state. The results revealed that increases in the fatigue limit above 50% can be achieved. © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IRAS 2023 organizers Keywords: Residual Stress; Assembling Stress; Stress shot peening; Parabolic Leaf Sprins; Railway 1. Introduction Leaf springs have been used for several decades in suspension systems, for example, in the suspension of goods transportation vehicles. Distinct geometries of leaf springs may be found in different vehicles, however, in the freight railway sector, this element has been standardized by the International Union of Railways, UIC (UIC, 2017). Parabolic leaf springs are been preferred instead of conventional geometries due to their good intrinsic features that provide better vehicle drivability and greater safety (Petrovic et. al. 2012). 2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IRAS 2023 organizers Second International Symposium on Risk Analysis and Safety of Complex Structures and Components (IRAS 2023) Experiments for the Quantification of the Initial Stress State in UIC Parabolic Leaf Springs V.M.G. Gomes a,b, *, M.J. Marques a,c , M. Figueiredo a , J.A.F.O. Correia a,b , A.C. Batista c , R. Calçada a , A.M.P. de Jesus a,b a FEUP, Faculty of Engineering of the University of Porto, Porto, Portugal b INEGI, Institute of Science and Innovation in Mechanical and Industrial Engineering, Porto, Portugal c Univ Coimbra, CFisUC, Department of Physics, Portugal Abstract Parabolic leaf springs applied in freight wagons are standardized by the International Union of Railways, UIC. According to the UIC, parabolic leaf springs must be stress peened after quenching and tempering in order to produce a compressive stress state on the surface to improve the fatigue strength. After heat and mechanical treatments, spring leaves are assembled. Due to distinct curvature radius of spring leaves, they are pre-stressed, introducing another type of initial stress state in the spring leaves. In order to quantify the initial stress state in UIC parabolic leaf springs, two types of experiments are performed. The stress relief method and the X-ray diffraction method are performed to analyze the assembling stresses and residual stresses by stress shot peening respectively. The superposition method is considered to estimate a corrected fatigue limit encompassing the material fatigue limit and the effect of the initial stress state. The results revealed that increases in the fatigue limit above 50% can be achieved. © 2023 The Authors. Published by ELSEVIER B.V. Keywords: Residual Stress; Assembling Stress; Stress shot peening; Parabolic Leaf Sprins; Railway 1. Introduction Leaf springs have been used for several decades in suspension systems, for example, in the suspension of goods transportation vehicles. Distinct geometries of leaf springs may be found in different vehicles, however, in the freight railway sector, this element has been standardized by the International Union of Railways, UIC (UIC, 2017). Parabolic leaf springs are been preferred instead of conventional geometries due to their good intrinsic features that provide better vehicle drivability and greater safety (Petrovic et. al. 2012). 2 Gomes et al/ Structural Integrity Procedia 00 (2023) 000–000 2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IRAS 2023 organizers Second International Symposium on Risk Analysis and Safety of Complex Structures and Components (IRAS 2023) Experiments for the Quantification of the Initial Stress State in UIC Parabolic Leaf Springs V.M.G. Gomes a,b, *, M.J. Marques a,c , M. Figueiredo a , J.A.F.O. Correia a,b , A.C. Batista c , R. Calçada a , A.M.P. de Jesus a,b a FEUP, Faculty of Engineering of the University of Porto, Porto, Portugal b INEGI, Institute of Science and Innovation in Mechanical and Industrial Engineering, Porto, Portugal c Univ Coimbra, CFisUC, Department of Physics, Portugal * Corresponding author. E-mail address: vgomes@inegi.up.pt 1.1. UIC Parabolic Leaf Springs