PSI - Issue 52

Yingwu Li et al. / Procedia Structural Integrity 52 (2024) 709–718 Author name / Structural Integrity Procedia 00 (2023) 000–000

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• The strain-frequency shift coe ffi cient in di ff erent tests consistently measured around -6.4 µε/ GHz. However, the stability of this coe ffi cient was influenced by changes in ambient temperature, especially when the ambient temperature falls below − 20 ◦ C or exceeds 70 ◦ C. Despite the variation, the measurement of this coe ffi cient demonstrated high consistency across di ff erent test scenarios. • The value of the temperature-frequency shift coe ffi cient was a ff ected by factors such as the coating material of SMF sensors and their installation state. The coe ffi cients obtained from three groups of temperature experiments were -1.55 ◦ C / GHz (acrylate coating in a free state), -1.04 ◦ C / GHz (acrylate coating after surface mounting), and -1.28 ◦ C / GHz (polymer coating in a free state), respectively. The coe ffi cient showed higher stability when SMF sensors with polymer coating were used or when the SMF sensors were installed. Additionally, the mea surement of this coe ffi cient also exhibited high consistency across di ff erent test scenarios. • The standard uncertainty (type A) of frequency shift measurements in the fifty-six independent test scenarios was found to be less than 0.1 GHz (when 200 measurement points were used in the calculation). This indicates that the uncertainty degree of measurement remains stable when employing distributed fiber optic sensors to obtain strain or temperature data in composite structures.

Acknowledgements

The authors would like to express gratitude to the president scholarship at Imperial College London and the Great Britain China Educational Trust for funding Yingwu Li Ph.D. research.

References

Cortina, J.M., 1993. What is coe ffi cient alpha? an examination of theory and applications. Journal of applied psychology 78, 98. D´ıaz-Maroto, P.F., Ferna´ndez-Lo´pez, A., Garc´ıa-Alonso, J., Iglesias, M., Gu¨emes, A., 2018. Buckling detection of an omega-sti ff ened aircraft composite panel using distributed fibre optic sensors. Thin-Walled Structures 132, 375–384. Froggatt, M., Moore, J., 1998. High-spatial-resolution distributed strain measurement in optical fiber with rayleigh scatter. Applied optics 37, 1735–1740. Fu, Y., Zhu, J., Wang, S., Xi, Z., 2015. Reduced complexity snr estimation via kolmogorov-smirnov test. IEEE Communications Letters 19, 1568–1571. Giannakeas, I.N., Khodaei, Z.S., Aliabadi, M.F., 2022. Structural health monitoring cost estimation of a piezosensorized aircraft fuselage. Sensors 22, 1771. Goossens, S., Berghmans, F., Khodaei, Z.S., Lambinet, F., Karachalios, E., Saenz-Castillo, D., Geernaert, T., 2021. Practicalities of bvid detection on aerospace-grade cfrp materials with optical fibre sensors. Composite Structures 259, 113243. Ho, J., Tumkaya, T., Aryal, S., Choi, H., Claridge-Chang, A., 2019. Moving beyond p values: data analysis with estimation graphics. Nature methods 16, 565–566. Iele, A., Leone, M., Consales, M., Persiano, G., Brindisi, A., Ameduri, S., Concilio, A., Ciminello, M., Apicella, A., Bocchetto, F., et al., 2018. Load monitoring of aircraft landing gears using fiber optic sensors. Sensors and Actuators A: Physical 281, 31–41. Iso, I., OIML, B., 1995. Guide to the expression of uncertainty in measurement. Geneva, Switzerland 122, 16–17. Kuang, K., 2015. Distributed damage detection of o ff shore steel structures using plastic optical fibre sensors. Sensors and Actuators A: Physical 229, 59–67. Kwon, Y.s., Naeem, K., Jeon, M.Y., Kwon, I.B., 2019. Enhanced sensitivity of distributed-temperature sensor with al-coated fiber based on ofdr. Optical Fiber Technology 48, 229–234. Li, S., Lu, G., Lai, C., Huang, Y., En, Y., 2019. Optical-path di ff erence on-line measurement of multiplexing fiber-optic interferometric sensors using tdm and wdm by improved optical-frequency-domain reflectometry, in: AOPC 2019: Optical Fiber Sensors and Communication, SPIE. pp. 152–157. Malkewitz, C.P., Schwall, P., Meesters, C., Hardt, J., 2023. Estimating reliability: A comparison of cronbach’s α , mcdonald’s ω t and the greatest lower bound. Social Sciences & Humanities Open 7, 100368. Spiliotopoulou, G., 2009. Reliability reconsidered: Cronbach’s alpha and paediatric assessment in occupational therapy. Australian Occupational Therapy Journal 56, 150–155. Steinke, A., Kopp, B., Lange, F., 2021. The wisconsin card sorting test: Split-half reliability estimates for a self-administered computerized variant. Brain Sciences 11, 529. Xu, C., Sharif Khodaei, Z., 2020. Shape sensing with rayleigh backscattering fibre optic sensor. Sensors 20, 4040. Zhang, X., Chen, Y., Hu, J., 2018. Recent advances in the development of aerospace materials. Progress in Aerospace Sciences 97, 22–34. Zinbarg, R.E., Revelle, W., Yovel, I., Li, W., 2005. Cronbach’s α , revelle’s β , and mcdonald’s ω h: Their relations with each other and two alternative conceptualizations of reliability. psychometrika 70, 123–133.