PSI - Issue 39

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Procedia Structural Integrity 39 (2022) 700–710

7th International Conference on Crack Paths Fatigue crack growth rate dependency on cold expansion degree in railway steel 7th International Conference on Crack Paths Fatigue crack growth rate dependency on cold expansion degree in railway steel

Giovanni Pio Pucillo 1, *, Giovanniluca De Vita 2 , Eugenio Fedeli 3 1 Department of Industrial Engineering - University of Naples Federico II, P. le V. Tecchio 80, 80125 Naples, Italy 2 R&D Department, Rete Ferroviaria Italiana S.p.A., via Curzio Malaparte 8, 50145 Florence, Italy 3 R&D Department, Rete Ferroviaria Italiana S.p.A., Piazza della Croce Rossa 1, 00161 Rome, Italy Giovanni Pio Pucillo 1, *, Giovanniluca De Vita 2 , Eugenio Fedeli 3 1 Department of Industrial Engine ing - University of Naples Fede ic II, P. le V. Tecchio 80, 80125 N ples, Italy 2 t t, t i i t li . . ., v Curzio Malaparte 8, 50145 Florenc , t l 3 R&D Department, Rete Ferroviaria Italiana S.p.A., Piazza della Croce Rossa 1, 00161 Rome, Italy

© 2021 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 CP 2021 – Guest Editors © 2021 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 CP 2021 – Guest Editors Keywords: Finite Element Analisys; Cold Expension; Residual Stresses; Strain Gauge; Fatigue life; Fatigue Crack Growth; Experimental Analisys Abstract The increase of railw y t ack occupancy e to high speed trains introduction in he morning and cross-border tr nsportation of hazardous and on-hazardous materials during late ours, require particular ttention for the fatigue d sign as well s the main en nce pl nning of railway superstructures. For this purpose, strategies final zed to increase the fatigu strength of railway structural parts assu e g interest for railway engin ers. Cold expansion technique, for example, is less xpens ve than o her mechanical and thermal treatments, but in the li erature there are no data conce ning its use in the railway field, being almost a l availabl studies f cused on luminum arts. In this paper, fatigue crack growth response of drill d sp cimens extracted from rails submitted or not to cold expan ion are pres nted. Two degree of cold-expansio , 2% and 4%, are investigated in terms of f tigue crack growth rate, nd the results compared to those obtained with not-expand d specimens. It is found that cold expansion ostpones fatigue cr ck initiation and that this ffect is mor pronounc d for increasing degre of cold expans on. A prelimin ry predictive model was dev lop d, based on the sum of the Stress Inte sity Factors calculat d with the weight functions and concerning the residual stress field induced by cold expansion, and the one generated by the external loads. © 2021 The Authors. Published by ELSEVIER B.V. This is an ope acces article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) P er-review under responsibility of CP 2021 – Guest Editor Keywords: Finite Element Analisys; Cold Expension; Residual Stresses; Strain Gauge; Fatigue life; Fatigue Crack Growth; Experimental Analisys Abstract The increase of railway track occupancy due to high speed trains introduction in the morning and cross-border transportation of hazardous and non-hazardous materials during late hours, require particular attention for the fatigue design as well as the maintenance planning of railway superstructures. For this purpose, strategies finalized to increase the fatigue strength of railway structural parts assume great interest for railway engineers. Cold expansion technique, for example, is less expensive than other mechanical and thermal treatments, but in the literature there are no data concerning its use in the railway field, being almost all available studies focused on aluminum parts. In this paper, fatigue crack growth response of drilled specimens extracted from rails submitted or not to cold expansion are presented. Two degree of cold-expansion, 2% and 4%, are investigated in terms of fatigue crack growth rate, and the results compared to those obtained with not-expanded specimens. It is found that cold expansion postpones fatigue crack initiation, and that this effect is more pronounced for increasing degree of cold expansion. A preliminary predictive model was developed, based on the sum of the Stress Intensity Factors calculated with the weight functions and concerning the residual stress field induced by cold expansion, and the one generated by the external loads.

* Corresponding author. Tel.: +39-081-7682378. E-mail address: gpucillo@unina.it * Correspon ing author. Tel.: +39-081-7682378. E-mail address: gpucillo@unina.it

2452-3216 © 2021 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 CP 2021 – Guest Editors 2452-3216 © 2021 The Authors. Published by ELSEVIER B.V. This is an ope acces article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2021 – Guest Editors

2452-3216 © 2021 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 CP 2021 – Guest Editors 10.1016/j.prostr.2022.03.143