Measurement of distributed strain and load identification using 1500 mm gauge length FBG and optical frequency domain reflectometry

Igawa, Hirotaka; Murayama, Hideaki; Nakamura, Toshiya; Yamaguchi, Isao; Kageyama, Kazuro; Uzawa, Kiyoshi; Wada, Daichi; Ohsawa, Isamu; Kanai, Motomu; Omichi, Koji

doi:10.1117/12.834236

Cited by 9 publications

(6 citation statements)

References 5 publications

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“…In our sensing system, we employ long-length FBGs whose length is about 100 mm and its length have been expanded up to 1500 mm so far. 35 The optical reflection characteristic is obtained at an arbitrary position within the long-length FBGs and strain distributions can be determined along the FBGs. Principles of the sensing system are described below.…”

Section: Fbg Sensormentioning

confidence: 99%

Strain monitoring of a single-lap joint with embedded fiber-optic distributed sensors

Murayama

Kageyama

Uzawa

et al. 2011

Structural Health Monitoring

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We have developed a fiber-optic distributed sensor which can measure strain distributions along fiber Bragg grating (FBG) with the high spatial resolution. This sensing system is based on optical frequency domain reflectometry and a long-length FBG whose length is about 100 mm can be used. We can identify the longitudinal strain at an arbitrary position along the FBG using signal processing technology. In this study, long-length FBGs were embedded into the adhesive layers of the two single-lap joints and we could successfully measure the strain distributions inside the adhesives. In one single-lap joint, the adherends were carbon fiber reinforced plastics and in another one, they were aluminum. The adhesive was epoxy in both cases. The measured results were compared with the calculated ones by nonlinear finite element (FE) analysis in which the large displacement and the elasto-plastic response of the adherend or adhesive material were account for. We found that in most of the applied loads, the agreement between the measured results and the calculated ones obtained from an intact FE model is excellent. While the measured strain distributions inside the adhesive layer of the aluminum single-lap joint were varied at the end of the overlap in the higher applied loads and they were much different from those of the intact model, an FE model with debonding was made and it could represent such variations. We could also monitor the strain distributions inside the adhesive during the manufacturing process and we observed the perturbation in residual strain distributions after curing. Consequently, we can say that the fiber-optic distributed sensor with the high spatial resolution is very useful not only to assess the structural integrity of adhesive joints but also to improve numerical analysis techniques and manufacturing processes for them.

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Section: Fbg Sensormentioning

confidence: 99%

Strain monitoring of a single-lap joint with embedded fiber-optic distributed sensors

Murayama

Kageyama

Uzawa

et al. 2011

Structural Health Monitoring

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“…The authors have developed the prediction technique of the distributed loads on a structure based on strain distributions measured by fiber-optic sensors [2,17,36]. In this paper, load identification of a simply supported aluminum beam with FBGs is shown.…”

Section: Load Identificationmentioning

confidence: 99%

Structural health monitoring by using fiber-optic distributed strain sensors with high spatial resolution

2013

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In this paper, we review our researches on the topics of the structural health monitoring (SHM) with the fiber-optic distributed strain sensor. Highly-dense information on strains in a structure can be useful to identify some kind of existing damages or applied loads in implementation of SHM. The fiber-optic distributed sensors developed by the authors have been applied to the damage detection of a single-lap joint and load identification of a beam simply supported. We confirmed that the applicability of the distributed sensor to SHM could be improved as making the spatial resolution higher. In addition, we showed that the simulation technique considering both structural and optical effects seamlessly in strain measurement could be powerful tools to evaluate the performance of a sensing system and design it for SHM. Finally, the technique for simultaneous distributed strain and temperature measurement using the PANDA-fiber Bragg grating (FBG) is shown in this paper, because problems caused by the cross-sensitivity toward strain and temperature would be always inevitable in strain measurement for SHM.

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“…In this context, many researchers have researched the identification of loads on critical vehicle structures to ensure the operational safety of vehicles [6][7][8][9][10]. In the time-frequency domain, the strain can be used not only to invert loads [11][12][13][14][15] but also to monitor fatigue and cracking of structures by strain [16]. Therefore the reconstruction of the strain field of the critical structure is crucial, however, the number of sensors that can be arranged on the structure is limited due to various conditions, so it is necessary to use certain algorithms to inverse perform the strain field of the whole structure by the strain values measured by a small number of sensors, which provides an important basis for the safety assessment of the structure and structural health monitoring.…”

Section: Introductionmentioning

confidence: 99%

Strain field reconstruction of crossbeam structure based on load–strain linear superposition method

Cheng¹,

Li²,

Wang³

et al. 2021

Smart Mater. Struct.

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To address the problem that sensors cannot be affixed at certain critical locations of the crossbeam structure and the full-field strain distribution cannot be obtained in real-time. In this paper, a strain field reconstruction algorithm based on the load-strain linear superposition method is proposed to reconstruct the strain field distribution of the structure under arbitrary static load in three dimensions using the strain data at a limited number of discrete locations. Especially when the load is unknown, the reconstruction of the strain field is very meaningful. In the elastic range, the strain under multiple loads is the linear superposition of the strain under a single load. By establishing the finite element model, the strain field reconstruction effect of the crossbeam under double loads and three loads is analyzed. The average relative error is 2.8%, 1.6%, 2.2%, and 2.1%, which verifies the accuracy of the algorithm. On this basis, the feasibility of strain field reconstruction is verified in detail by a static load test. The experimental results show that there is a good consistency between them, indicating the effectiveness of the method. Even in the case of a single load, the strain field distribution of the crossbeam structure can be reconstructed in real-time by comparing the measured strain with the simulated strain.

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Measurement of distributed strain and load identification using 1500 mm gauge length FBG and optical frequency domain reflectometry

Cited by 9 publications

References 5 publications

Strain monitoring of a single-lap joint with embedded fiber-optic distributed sensors

Strain monitoring of a single-lap joint with embedded fiber-optic distributed sensors

Structural health monitoring by using fiber-optic distributed strain sensors with high spatial resolution

Strain field reconstruction of crossbeam structure based on load–strain linear superposition method

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