PSI - Issue 54

ScienceDirect 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 Available online at www.sciencedirect.com

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 54 (2024) 218–224

© 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 scientific committee of the ICSI 2023 organizers Abstract The paper investigates the impact of strain gradient on the reflected spectrum of fiber Bragg gratings (FBGs) of varying lengths (5, 10, and 15 mm), inscribed using two techniques: phase mask method and point-by-point inscription with a femtosecond laser. A geometric configuration of the samples was proposed to create a sufficient strain gradient along the length of studied FBGs. In order to precisely locate FBGs on the surface of the sample an approach employing distributed fiber-optic sensors (FOSs) based on Rayleigh scattering is proposed. It was demonstrated that FBGs inscribed with a femtosecond laser, preserving the protective coating, withstand higher loads and exhibit symmetrical spectral changes under tension and compression. This research contributes to the understanding of FBG behavior under strain gradients, with implications for Structural Health Monitoring. © 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 scientific committee of the ICSI 2023 organizers Keywords: Fiber Bragg grating; Strain measurements; Strain gradient 1. Introduction Fiber-optic sensors (FOSs) are gaining widespread popularity for use in Structural Health Monitoring (SHM) systems of various structures due to their high measurement accuracy, ease of installation on the surface of a structure or integration into the structure of a material [1 – 3]. Among FOSs, point sensors based on fiber Bragg gratings (FBGs) are in demand for strain measurement in a variety of practical applications [4] due to the stability of readings, the availability of interrogation systems, and the relative ease of application. Abstract The paper investigates the impact of strain gradient on the reflected spectrum of fiber Bragg gratings (FBGs) of varying lengths (5, 10, and 15 mm), inscribed using two techniques: phase mask method and point-by-point inscription with a femtosecond laser. A geometric configuration of the samples was proposed to create a sufficient strain gradient along the length of studied FBGs. In order to precisely locate FBGs on the surface of the sample an approach employing distributed fiber-optic sensors (FOSs) based on Rayleigh scattering is proposed. It was demonstrated that FBGs inscribed with a femtosecond laser, preserving the protective coating, withstand higher loads and exhibit symmetrical spectral changes under tension and compression. This research contributes to the understanding of FBG behavior under strain gradients, with implications for Structural Health Monitoring. © 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 scientific committee of the ICSI 2023 organizers Keywords: Fiber Bragg grating; Strain measurements; Strain gradient 1. Introduction Fiber-optic sensors (FOSs) are gaining widespread popularity for use in Structural Health Monitoring (SHM) systems of various structures due to their high measurement accuracy, ease of installation on the surface of a structure or integration into the structure of a material [1 – 3]. Among FOSs, point sensors based on fiber Bragg gratings (FBGs) are in demand for strain measurement in a variety of practical applications [4] due to the stability of readings, the availability of interrogation systems, and the relative ease of application. International Conference on Structural Integrity 2023 (ICSI 2023) Investigation of fiber Bragg grating’s spectrum response to strain gradient International Conference on Structural Integrity 2023 (ICSI 2023) Investigation of fiber Bragg grating’s spectrum response to strain gradient Matveenko V.P. a , Serovaev G.S. a *, Kosheleva N.A. a , Galkina E.B. a a Institute of Continuous Media Mechanics UB RAS, 1, Akademika Koroleva Str.,Perm, 614068, Russia Matveenko V.P. a , Serovaev G.S. a *, Kosheleva N.A. a , Galkina E.B. a a Institute of Continuous Media Mechanics UB RAS, 1, Akademika Koroleva Str.,Perm, 614068, Russia

* Corresponding author. Tel.: +7(342)-237-83-08. E-mail address: serovaev@icmm.ru * Corresponding author. Tel.: +7(342)-237-83-08. E-mail address: serovaev@icmm.ru

2452-3216 © 2022 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 Pedro Miguel Guimaraes Pires Moreira 2452-3216 © 2022 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 Pedro Miguel Guimaraes Pires Moreira

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 scientific committee of the ICSI 2023 organizers 10.1016/j.prostr.2024.01.076