Theoretical Analysis on Strain Transfer Error of FBG Sensors Attached on Steel Structures Subjected to Fatigue Load

Abstract

Fibre Bragg grating (FBG) sensors have been increasingly adopted to detect the dynamic strain of structures. When the sensor is attached on the surface, adhesive material is employed to assist the installation, which leads to indirect contact of sensing fibre and the monitored structure. To correct the strain transfer error induced by the shear lag effect and improve the measurement accuracy of FBG sensors under dynamic response, strain transfer mechanism of a three-layered testing model constituted of sensing fibre, adhesive layer and host material has been studied in this paper. Laboratory test on steel beam attached with FBG sensor under fatigue load has been projected to investigate the feasibility of the derived strain transfer formula, and numerical simulation by MATLAB has been used as a supporting tool to offer the reference dynamic strain. Based on the analysis, sensitive parameters that affect the strain transfer coefficient have been discussed to instruct the application design of FBG sensors. Results indicate that strain transfer coefficient under dynamic response is much lower than that in static state, and error modification is particularly significant; in the dynamic testing model, bonded length, shear modulus and thickness of adhesive layer are more sensitive, which should be precisely selected in practical engineering to guarantee the effective strain measurement.

Selection of the Optimal FBG Length for Use in Stress-Strain State Diagnostic Systems

“…This article discusses FBGs of two manufacturers made using the same technology of recording with a phase mask [9][10][11], in standard germanosilicate fibers of the SMF-28 type, except for fibers with increased mode retention due to a reduced core and a complex refractive index profile. The relevance of this study is due to the large number of publications related to the description of systems for diagnosing the stress-strain state of various parts and assemblies (structures, machines, movable equipment) based on FBG [12,13].…”

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“…Rujun, et al [15] analyze the transfer mechanism of FBG strain sensor in detail and propose the shear stress distribution of polynomial form. All these research works establish the strain transfer theoretical foundation of FBG strain sensor [16,17].…”

Dynamic Performance Detection of CFRP Composite Pipes based on Quasi-Distributed Optical Fiber Sensing Techniques

“…However, it is based on electrical input, which may lead to the blast or fire of pipelines for oil and gas transportation. Due to the advantages of absolute measurement, anti-electromagnetic interference, high precision, multiplexing, and integration of sensing network over other sensors (Ansari, 2007;Wang et al, 2014;Wang et al, 2016;Wang et al, 2018a, Wang et al, 2018bWang et al, 2019a;, optical fiber based sensors have thus been adopted to monitor the health condition and structural performance of pipe structures. For the excellent characteristics of low weight, corrosion resistance, and high strength (Dai et al, 2013;Gao et al, 2015;Wang et al, 2019b), carbon fiber-reinforced polymer (CFRP) composite pipes have been considered, and the exploration on the replacement of steel pipes still requires further investigation.…”