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

2021 ◽  
Author(s):  
Shuaifei Tian ◽  
Haibo Zhu ◽  
Ran An ◽  
Yiping Tang ◽  
yuan yonggui ◽  
...  
Keyword(s):  
Strain Distribution ◽  
Fiber Optic ◽  
Distribution Characteristics

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

2015 ◽  
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.

scholarly journals Numerical Simulation of the Volumetric Strain Distribution of a Protected Coal Seam

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Hengyi Jia
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Strain Distribution ◽  
Volumetric Strain ◽  
Distribution Characteristics ◽  
Permeability Enhancement ◽  
Working Face ◽  
Coal Pillars ◽  
Definition Of ◽  
Seam Mining

To investigate the deformation characteristics of protected coal seams, the numerical simulation of the mining of an upper protective coal seam was carried out in the present study. Based on the basic definition of strain, a method for the extraction of the strain data of the protected coal seam was proposed, and the strain distribution characteristics were obtained. It was found that the x -direction strain is mainly distributed near the coal pillars on both sides and inside the goaf, the y -direction strain is mainly distributed at the working face, the initial mining line, and inside the goaf, and the z -direction strain is mainly distributed at the working face, the initial mining line, the coal pillars on both sides, and inside the goaf. The distribution characteristics and the value of volumetric strain were found to be basically consistent with the z -direction strain. As the working face advances, the protected coal seam undergoes compression and damage expansion in turn. The turning point between compression and damage expansion is approximately 15 m in front of the working face. The variation law of gas drainage in the boreholes of the protected coal seam is closely related to the distribution characteristics of volumetric strain. The results of this research are of great significance for the comprehensive investigation of the effects of pressure relief and the permeability enhancement of protective coal seam mining.

scholarly journals Damage Evolution and Circumferential Strain Distribution Characteristics of the Bolt-Supported Cavern under Multiple Explosion Sources

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Taotao Wang ◽  
Ansheng Cao ◽  
Weiliang Gao ◽  
Guangyong Wang ◽  
Xiaowang Sun
Keyword(s):  
Tensile Stress ◽  
Stress Wave ◽  
Strain Distribution ◽  
Damage Evolution ◽  
Circumferential Strain ◽  
Circumferential Stress ◽  
Surrounding Rock ◽  
Distribution Characteristics ◽  
Finite Element Software ◽  
The Impact

The impact of multiple explosion sources on the safety of the underground cavern is enormous. Based on a similarity model test, the finite element software LS-DYNA3D was utilized to analyze the damage evolution and circumferential strain distribution characteristics of the bolt-supported cavern under the seven combinations of concentrated charge explosion sources in three places, including the side of the vault, side arch, and sidewall. The accuracy of the simulation results is verified by comparing them with test results. The research results indicate that the damage of the surrounding rock is mainly caused by the tensile stress wave reflected from the free surfaces and the superposition of the tensile stress wave. The damage of the surrounding rock in the cases of multiple explosion sources is not a simple superposition of that in the cases of a single explosion source. The peak circumferential stress and damage of the surrounding rock in the middle of two explosion sources are significantly greater than that of the cases of the corresponding single explosion source. In the seven cases, the peak circumferential strain of the cavern wall changes from tensile to compressive from the vault to the spandrel. When the explosion occurs on the sidewall, the peak circumferential strain of the floor is tensile.

scholarly journals Development and Application of Smart Geogrid Embedded with Fiber Bragg Grating Sensors

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Zheng-fang Wang ◽  
Jing Wang ◽  
Qing-mei Sui ◽  
Xun-mei Liang ◽  
Lei Jia ◽  
...  
Keyword(s):  
Fiber Bragg Grating ◽  
Strain Distribution ◽  
Fiber Optic ◽  
Strain Sensor ◽  
Bragg Grating ◽  
Tunnel Excavation ◽  
Strain Transfer ◽  
Geotechnical Structures ◽  
Higher Temperature ◽  
Geotechnical Model

Smart geogrids embedded with fiber Bragg grating (FBG) for reinforcement as well as measurement of geotechnical structures have been developed. After the fabricating process of the geogrids is detailed, finite element (FE) simulations are conducted to analyze the strain distribution of geogrids and the strain transfer characteristics from geogrids to fiber optic. Results indicate that FBG should be deployed in the middle of the geogrids rib to make sure that uniform strain distribution along the FBG. Also, PVC protective sleeves, which are used to protect fiber optic when integrated with geogrids, have smaller strain transfer loss than nylon sleeves. Tensile experiments are conducted to test strain measurement performance of proposed geogrids, and the results demonstrate that proposed smart geogrids have good linearity and consistency. Temperature experiments show that FBG embedded in geogrids has higher temperature sensitivity, and the temperature induced error can be compensated by an extra FBG strain-independent sensor. Furthermore, designed smart geogrids are used in a geotechnical model test to monitor strain during tunnel excavation. The strain tendency measured by smart geogrids and traditional strain sensor agree very well. The results indicate that smart geogrids embedded with FBGs can be an effective method to measure strains for geological engineering related applications.

Study on 3D Strain Distribution Characteristics Using Etched Grid Method in Tube Bending

2012 ◽  
Vol 184-185 ◽  
pp. 505-509
Author(s):  
Heng Li ◽  
He Yang ◽  
Kai Peng Shi
Keyword(s):  
Strain Distribution ◽  
Three Dimensional ◽  
Grid Method ◽  
Thickness Variation ◽  
Distribution Characteristics ◽  
Tube Bending ◽  
Thickness Strain ◽  
Bending Angle ◽  
Maximum Value ◽  
Wall Thickness Variation

Strain distribution is crucial for understanding tube bending and preventing defects. In this paper, taking 321 stainless steel as the objective, via etched grid method, the strain distribution characteristics during tube bending are studied, the effects of the bending velocity and the bending angle on the strain distribution are analyzed, and the consistency of thickness strain with wall thickness variation is verified. The results show that: (1) three-dimensional (3D) strain is symmetrically distributed about bending plane and reaches the maximum value at wall extrados and intrados; (2) absolute value of the 3D strain increases at first, then decreases in tube bending; (3) compared with bending angle, bending velocity has greater effect on spatial strain, and compared with tangent strain, thickness strain is more sensitive to bending velocity; (4) thickness strain distribution characteristics are generally consistent with distribution characteristics of wall thinning degree.

scholarly journals Distributed Fiber Optic Sensors for the Monitoring of a Tunnel Crossing a Landslide

2018 ◽  
Vol 10 (8) ◽  
pp. 1291 ◽  
Author(s):  
Aldo Minardo ◽  
Ester Catalano ◽  
Agnese Coscetta ◽  
Giovanni Zeni ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Strain Distribution ◽  
Fiber Optic ◽  
Temporal Evolution ◽  
Strain Sensor ◽  
Fiber Optic Sensors ◽  
Railway Tunnel ◽  
Long Term Monitoring ◽  
Term Monitoring

This work reports on the application of a distributed fiber-optic strain sensor for long-term monitoring of a railway tunnel affected by an active earthflow. The sensor has been applied to detect the strain distribution along an optical fiber attached along the two walls of the tunnel. The experimental results, relative to a two-year monitoring campaign, demonstrate that the sensor is able to detect localized strains, identify their location along the tunnel walls, and follow their temporal evolution.

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

2020 ◽  
Vol 10 (23) ◽  
pp. 8437
Author(s):  
Il-Bum Kwon ◽  
Yong-Seok Kwon ◽  
Dae-Cheol Seo ◽  
Dong-Jin Yoon ◽  
Eunho Kim
Keyword(s):  
Correlation Coefficient ◽  
Strain Field ◽  
Strain Distribution ◽  
Slope Failure ◽  
Fiber Optic ◽  
Tensile Force ◽  
Bearing Plate ◽  
Anchor Systems ◽  
Reliable Correlation ◽  
Anchor Force

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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