A Technic for Ground Anchor Force Determination from Distributied Strain Using Fiber Optic OFDR Sensor with the Rejection of a Temperature Effect

Anchor systems are widely used to stabilize soil slope and suppress slope failure. Thus, monitoring conditions of an anchor system is important to prevent disasters due to slope failure. The slope condition can be indirectly monitored by sensing the tensile force applied to the anchor because the slope deformation directly affects the anchor force. Previously, we propose a way to monitor the tensile force of the anchor by measuring the strain field on a bearing plate using a distributed fiber optic sensor (OFDR) and experimentally demonstrate that the anchor force has a large correlation with the strain distribution on the bearing plate. However, it was found that a spatial variation of the strain and thermal strain due to temperature change makes it difficult to get a reliable correlation coefficient. In this study, we newly propose a way to get a reliable correlation coefficient between the anchor force and the strain field on the bearing plate. We install a distributed optical fiber sensor in two concentric circles on the bearing plate and measure circumferential strain distribution. We take average values of the strain field in each circle as representative strain values minimizing the spatial variation and takes a difference of the two strains to exclude the temperature effect. We experimentally demonstrate that the proposed method gives a reliable correlation coefficient between the anchor force and the strain field on the bearing plate. This technique can be applied to various anchor systems to monitor the anchor force and manage the anchor systems safely.

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Strain Measurement Distributed on a Ground Anchor Bearing Plate by Fiber Optic OFDR Sensor

Applied Sciences ◽

10.3390/app8112051 ◽

2018 ◽

Vol 8 (11) ◽

pp. 2051 ◽

Cited By ~ 7

Author(s):

Yong-Seok Kwon ◽

Dae-Cheol Seo ◽

Bo-Hun Choi ◽

Min Jeon ◽

Il-Bum Kwon

Keyword(s):

Fiber Optic ◽

Tensile Force ◽

Tunable Laser ◽

Laser Source ◽

Bearing Plate ◽

Ground Anchors ◽

Optical Frequency Domain Reflectometry ◽

Frequency Domain Reflectometry ◽

The Difference ◽

Ground Anchor

The safety of soil slopes reinforced by ground anchors can be evaluated by monitoring the tensile force of the anchors. The tensile force of ground anchors can be determined by measuring the strain of the bearing plate that transfers the tensile force of the anchor to the ground. Therefore, in order to investigate the relation between the strain of the bearing plate and the tensile force of a ground anchor, the strain distributed on the bearing plate was measured by a fiber optic OFDR (optical frequency domain reflectometry) sensor, which was fabricated by a tunable laser source, auxiliary interferometer, and main interferometer. This OFDR sensor was operated through a sweep range of 500 GHz with a spatial resolution of 0.2 mm, and a strain accuracy of approximately 4 με, considering the system noise when operating in 5-cm segments. The sensing fiber was circularly bonded onto the bearing plate using epoxy, and the distributed strain was measured on the bearing plate while increasing the load up to 10 tons. From the experimental results, the difference between the strain near the anchor head and the strain at the far site is significant in the region where compression strain is dominant. However, such a tendency did not appear in areas where bending strain dominates. Therefore, in order to monitor an anchor tensile force, it is necessary to carefully study the calibration factor between the anchor tensile force and the strain of the bearing plate.

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Strain field determination in III–V heteroepitaxy coupling finite elements with experimental and theoretical techniques at the nanoscale

Journal of the Mechanical Behavior of Materials ◽

10.1515/jmbm-2017-0009 ◽

2017 ◽

Vol 26 (1-2) ◽

pp. 1-8

Author(s):

Nikoletta Florini ◽

George P. Dimitrakopulos ◽

Joseph Kioseoglou ◽

Nikos T. Pelekanos ◽

Thomas Kehagias

Keyword(s):

Finite Elements ◽

Strain Field ◽

Strain Distribution ◽

Elastic Strain ◽

Growth Direction ◽

Current Status ◽

Interface Plane ◽

Fe Method ◽

Semiconductor Nanostructure

AbstractWe are briefly reviewing the current status of elastic strain field determination in III–V heteroepitaxial nanostructures, linking finite elements (FE) calculations with quantitative nanoscale imaging and atomistic calculation techniques. III–V semiconductor nanostructure systems of various dimensions are evaluated in terms of their importance in photonic and microelectronic devices. As elastic strain distribution inside nano-heterostructures has a significant impact on the alloy composition, and thus their electronic properties, it is important to accurately map its components both at the interface plane and along the growth direction. Therefore, we focus on the determination of the stress-strain fields in III–V heteroepitaxial nanostructures by experimental and theoretical methods with emphasis on the numerical FE method by means of anisotropic continuum elasticity (CE) approximation. Subsequently, we present our contribution to the field by coupling FE simulations on InAs quantum dots (QDs) grown on (211)B GaAs substrate, either uncapped or buried, and GaAs/AlGaAs core-shell nanowires (NWs) grown on (111) Si, with quantitative high-resolution transmission electron microscopy (HRTEM) methods and atomistic molecular dynamics (MD) calculations. Full determination of the elastic strain distribution can be exploited for band gap tailoring of the heterostructures by controlling the content of the active elements, and thus influence the emitted radiation.

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Strain distribution characteristics of sensing fiber andinfluence on sensitivity of fiber-optic discaccelerometer

Applied Optics ◽

10.1364/ao.439162 ◽

2021 ◽

Author(s):

Shuaifei Tian ◽

Haibo Zhu ◽

Ran An ◽

Yiping Tang ◽

yuan yonggui ◽

...

Keyword(s):

Strain Distribution ◽

Fiber Optic ◽

Distribution Characteristics

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Strain Field Identification of an Aluminum Plate by using Distributed Fiber-Optic Sensors

Structural Health Monitoring 2017 ◽

10.12783/shm2017/14028 ◽

2017 ◽

Author(s):

HIDEHARU OGINO ◽

HIDEAKI MURAYAMA ◽

FUMIYA FUJIMORI ◽

KAZURO KAGEYAMA ◽

DAICHI WADA ◽

...

Keyword(s):

Strain Field ◽

Fiber Optic ◽

Fiber Optic Sensors ◽

Aluminum Plate ◽

Field Identification

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Multidimensional strain field measurements using fiber optic grating sensors

10.1117/12.388113 ◽

2000 ◽

Cited By ~ 24

Author(s):

Eric Udd ◽

Whitten L. Schulz ◽

John M. Seim ◽

Eric D. Haugse ◽

Angela Trego ◽

...

Keyword(s):

Strain Field ◽

Fiber Optic ◽

Field Measurements

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Quantum-Dot Molecules for Potential Applications in Terahertz Devices

MRS Proceedings ◽

10.1557/proc-829-b1.3 ◽

2004 ◽

Vol 829 ◽

Cited By ~ 1

Author(s):

Valeria Gabriela Stoleru ◽

Elias Towe ◽

Chaoying Ni ◽

Debdas Pal

Keyword(s):

Optical Properties ◽

Quantum Dot ◽

Strain Field ◽

Strain Distribution ◽

Major Step ◽

Cross Sectional ◽

Electronic And Optical Properties ◽

Quantum Dot Molecules ◽

Transmission Electron ◽

Potential Applications

ABSTRACTThe experimental and theoretical results of the electronic and optical properties of quantum dot artificial molecules (AMs), formed by pairs of electronically coupled quantum dots (QDs), are presented here in order to identify the necessary conditions for the development of new types of terahertz (THz) injection lasers based on intraband carrier transitions. We have performed analytical calculations to obtain the spatial strain distribution in vertically aligned (In, Ga)As QDs grown on (001) GaAs substrates by molecular beam epitaxy. Electronic coupling of the dots, mainly governed by the thickness of the separating barrier between the dot layers, is allowed due to the strain field-assisted self-organization of the dots. The calculated strain field reproduces our cross sectional high-resolution transmission electron microscopy observations very well. We further take into account the microscopic effects of the spatial strain distribution on carrier confinement potentials, and compute the electronic structure of the AM. Our calculations of the peak luminescence energies are in good agreement with our experimental results and those of others. The growth of quantum dot molecules represents a major step in tailoring the electronic and optical properties of the nanostructures.

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Fiber optic distributed temperature sensing for the determination of air temperature

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-6287-2014 ◽

2014 ◽

Vol 7 (6) ◽

pp. 6287-6298

Author(s):

S. A. P. de Jong ◽

J. D. Slingerland ◽

N. C. van de Giesen

Keyword(s):

Solar Radiation ◽

Correlation Coefficient ◽

Air Temperature ◽

Fiber Optic ◽

Solar Heating ◽

Temperature Sensing ◽

Distributed Temperature Sensing ◽

Air Temperatures ◽

Different Diameters

Abstract. This paper describes a method to correct for the effect of solar radiation in atmospheric Distributed Temperature Sensing (DTS) applications. By using two cables with different diameters, one can determine what temperature a zero diameter cable would have. Such virtual cable would not be affected by solar heating and would take on the temperature of the surrounding air. The results for a pair of black cables and a pair of white cables were very good. The correlations between standard air temperature measurements and air temperatures derived from both colors had a high correlation coefficient (r2 = 0.99). A thin white cable measured temperatures that were close to air temperature. The temperatures were measured along horizontal cables but the results are especially interesting for vertical atmospheric profiling.

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Local high edge observation for the bonding line monitoring of a complex composite beam

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220932194 ◽

2020 ◽

pp. 095440622093219

Author(s):

Monica Ciminello ◽

Bernardino Galasso ◽

Gianvito Apuleo ◽

Shay Shoam ◽

Antonio Concilio

Keyword(s):

Strain Field ◽

Composite Beam ◽

Composite Structures ◽

Longitudinal Strain ◽

Fiber Optic ◽

Signal To Noise Ratio ◽

Fiber Optic Sensors ◽

Signal To Noise ◽

Mechanical Loads ◽

Spatial Domains

The most part of defects in composite structures carrying attached subelements is the disbond at the interface, as the skin/stringer sections. This is sometimes due to a nonoptimal manufacturing process or sometimes due to accidental object impacts during service. It has been verified that structural discontinuities within an elastic medium under mechanical loads can cause analogous discontinuities within the strain field. Starting from this analysis, the present work investigates the effect of artificially induced kissing bond areas just at the in the skin–stiffener interface of an aeronautical complex composite beam. This research uses longitudinal strain values, acquired at the locations where distributed fiber optic sensors are installed. The applied methodology uses different strain-based features providing local high edge observation both in time and spatial domains. Their autocorrelations are, in the end, computed to improve signal-to-noise ratio. The local high edge observation algorithm is proposed that proves its capability to monitor disbond being at the same time load and baseline independent.

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Kilometer-Long Optical Fiber Sensor for Real-Time Railroad Infrastructure Monitoring to Ensure Safe Train Operation

2015 Joint Rail Conference ◽

10.1115/jrc2015-5653 ◽

2015 ◽

Cited By ~ 3

Author(s):

Yi Bao ◽

Genda Chen ◽

Weina Meng ◽

Fujian Tang ◽

Yizheng Chen

Keyword(s):

Real Time ◽

Spatial Resolution ◽

Strain Distribution ◽

Fiber Optic ◽

Gage Length ◽

Fiber Optic Sensor ◽

Sensor Deployment ◽

Small Scale ◽

Distributed Sensors ◽

Optic Sensor

This study is aimed to develop a real-time safety monitoring of kilometer-long joint rails using a distributed fiber optic sensor. The sensor measures the distribution of Brillouin frequency shift along its length with pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). The measurement distance and spatial resolution can be up to 25 km and 2 cm, respectively. The fiber optic sensor was first characterized and calibrated for distributed strain and temperature measurement, and then instrumented on a small-scale joint rail-like specimen in laboratory. The specimen was loaded at room temperature, and its strain distribution along the sensor was measured using a Neubrescope with high accuracy and spatial resolution. Given a gage length, the joint open change was determined and visibly identified from the measured strain distribution. Finally, an implementation plan of distributed sensors on a railway is introduced, including sensor deployment, sensor repair when broken, and cost analysis. The gage length at a crack is an important parameter in sensor deployment and investigated using finite element analysis. The results indicate that the distributed sensor can be used successfully to monitor the strain and temperature distributions in joint rails.

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