Based on fiber sensor network rail transit IoT monitoring system

This paper considers the use of on-line structural health monitoring in advanced nuclear power systems such as IRIS. The motivation for the on-line health monitoring is to prevent routine maintenance from interrupting long-term continuous reactor operation. However, the outcome of the on-line monitoring implementation has a broader impact, and amounts to a paradigm shift in maintenance strategy from outage-based maintenance to continuous real-time monitoring of operational and structural integrity. Indeed, on-line health monitoring data will provide a foundation for diagnostics and prognostics (i.e., predictive) capabilities that will detect component degradation prior to failure, thus allowing for proactive rather than reactive maintenance strategies. Specifically, this paper briefly reports on our studies on (1) on-line monitoring strategy and its benefits, (2) candidate reactor components where on-line monitoring provides maximum benefits, (3) applicable on-line NDE sensor methodologies and conceptual sensor designs, and (4) model-based sensor performance estimations.

This paper demonstrates the reliability and accessibility functions of fiber Bragg grating(FBG) sensors in a radiation structural health monitoring and safety evaluationapplication. FBG sensors, dial gages and conventional resistance strain gages(RSGs) were attached to the temporary H-beam frame, and distributed belowthe path of the rail tracks for online safety measurements during the process ofmoving the structure of the research reactor. The results showed the high level ofperformance of the FBG sensors for an online structural health monitoring system. Themeasurement data from the FBG monitoring system were comparable to thetheoretical calculation results and the FEM simulations as the movement progressed.The result of this investigation also clearly demonstrates that FBG sensors canovercome the harsh environments of electric and magnetic interference, whileconventional RSG sensors are subject to serious fluctuations providing useless feedback.

To study the internal stress during the electroplating processes, the Fiber Bragg Grating (FBG) sensors were electroplated with Ni, Zn, Cu films, respectively. During the electroplating, the current density was set to be 24 mA/cm2. The changes of internal stress of the metal films can be calculated according to the shift of central wavelength of the FBG sensors, blue shift showing a compressive stress and red shift showing a tensile stress. Results show: (i) the central wavelength of the FBG sensor blue shifted 2.26 nm after electroplating Ni for 420 min, the associated compressive stress in FBG sensor was calculated to be 551 MPa; (ii) the central wavelength of the FBG sensor red shifted 0.29 nm after electroplating Zn for 420 min, the associated tensile stress in FBG sensor was calculated to be 69 MPa; (iii) the central wavelength of the FBG sensor red shifted 0.04 nm after electroplating Cu for 420 min, the associated tensile stress in FBG sensor was calculated to be 10 MPa; (iv) a model characterizing the relationship between the internal stress and the central wavelength shift of the FBG was proposed, the feasibility and associated conclusions are verified by the nanoindentation tests.

This paper aims at numerical modeling of laser solid freeform fabrication (LSFF) process utilized in embedding of fiber Bragg grating (FBG) sensors inside metallic structures. This model is used in characterization of the process. Fiber Bragg grating sensors have the capability of being embedded inside structures for monitoring temperature, strain and pressure. Due to the sensitivity of the FBG sensors to high temperatures and stresses, the embedding process using LSFF is a challenging task. In the present paper, a finite element model is developed to predict the stress and temperature fields adjacent to the fiber optic sensor inside the metallic structure and maps them to the spectral response of the sensor. Using this method, the stress-strain and temperature conditions of the sensor during the embedding process can be monitored and the modeling data can be used for process control and characterization to minimize the effects of high temperatures and residual stresses having negative effects on sensor coherence with the surrounding media. Finally, the proposed model is validated with an existing analytical model predicting temperature field and melt pool geometry.

Non-destructive evaluation of smart materials by using extrinsic Fabry–Perot interferometric and fiber Bragg grating sensors

This study presents the design, calibration, and performance evaluation of Fiber Bragg Grating (FBG) sensors embedded in phenolic resin-based glass fiber composites for simultaneous temperature and strain monitoring up to 600 °C. A custom high-temperature tensile testing system was developed to perform (i) static tensile tests at room temperature (RT) and after carbonization at 200 °C, 400 °C, and 600 °C, and (ii) dynamic thermal strain tests under controlled heating–cooling cycles. The results demonstrated that the FBG sensors can effectively measure the internal strain within the temperature range of 27 °C to 600 °C. Prior to carbonization of the composite, the elastic modulus at room temperature was approximately 17.5 GPa. After carbonization, the elastic modulus at 600 °C, 400 °C, and 200 °C was 4.1 GPa, 3.5 GPa, and 3.4 GPa, respectively, aligning well with independent high-temperature modulus measurements. The dynamic tests showed that the FBG sensors were able to accurately detect transient strain changes induced by load variations at different temperatures, which was consistent with thermal expansion data. This study provides crucial empirical evidence for the design and optimization of the thermal protection of composite materials, confirming the effectiveness of embedded FBG sensors for monitoring mechanical behavior in high-temperature environments.

n ABSTRACT Accur ate and real-time online monitoring of substation equipments is of vital importance to the reliability of intelligent substations. Optical fiber Bragg grating (FBG) sensors and Internet of Things (loT) are key enablers to achieve accurate , real-time and intelligent online monitoring. In this paper we present a highly reliable and extensible online monitoring system built upon FBG sensors and loT technologies. Future research work is also presented.

A novel low-cost gas sensor for CO2 detection using polymer-coated fiber Bragg grating

Measurement of blade strain with sensors directly installed on the blade has one critical issue, how to send the sensor signal to the ground. Strain-gauges have been dominantly used to directly measure stress of a blade and either a slip ring or a telemetry system has to be used to send measured signal to the ground. However, both systems have many inherent problems and sometimes very severe limitations to be practically used. In this paper, new on-line strain monitoring method using. FBG(Fiber Bragg Grating) sensors and a beam coupler is introduced. Measurement of rotor stress using FBG sensors is nothing new, but unlike other system which installs all necessary instruments on the rotor and use telemetry system to send data to the ground, this system makes use of light's unique characteristic - light travels through space. In this new approach, single optical fiber with many FBG sensors is installed on the blade and all other necessary instruments can be installed at ground thereby giving tremendous advantages over slip ring or telemetry system. A reference sensor is also introduced to compensate the beam coupler's transmission loss change due to rotation. The suggested system's good performance is demonstrated with experiments.

Rotating compressor blades experience complex alternating loads during service, altering their stress–strain distributions and peak stress positions over time. Accurate measurement of these strains is crucial for identifying the areas of stress concentration. This paper presents a structural health monitoring system using fiber Bragg grating (FBG) sensors to record dynamic strains on laboratory-scale rotating blades, and a tailored full-field strain reconstruction methodology, which successfully identifies the magnitude of the strains and the areas of stress concentration of the blades at different rotational speeds. First, dynamic strain at selected blade points was monitored using FBG sensors, with raw signal data enhanced by the empirical wavelet transform method to reduce noise and clarify signals. An analytical framework was developed to relate blade rotational velocity to signal period, enabling precise speed calculation and accurate strain analysis. The improved-Kriging interpolation technique was then used to reconstruct comprehensive strain profiles. A comparative analysis showed an average strain relative error of 7.4% between predicted and actual values, demonstrating the methodology’s robustness and precision.

A method based on FBG sensor array to monitoring large structure's security state is described. A configuration combing a fiber Fabry-Perot tunable filter and a fiber Fabry-Perot interferometer is used to interrogate FBG sensors. The strain signal and acceleration signal can be obtained from the some one FBG sensor, and the number of DFB sensors is reduced to half. The fiber Fabry-Perot tunable filter-based system has the capability to interrogate large number of DFB sensors, whilst obtaining absolute Bragg wavelength with pm resolution. A demonstration system with 4 DFB sensors is presented, which obtains DFB sensor's direct strain value and achieves sub-microstrain resolution at 300Hz interrogating rate. With fast interrogate rate, wide band acceleration signal can also be achieved.

The purpose of this presentation is to provide an understanding of the current state-of-the-art in fiber Bragg grating (FBG) sensors and instrumentation for dynamic and vibration testing. Innovation in the optoelectronics and fiber-optic communication industries has significantly reduced optical component prices and improved quality. By leveraging these economies of scale, fiber-optic sensors and instruments have moved from experimental research applications in the lab to broad usage and applicability in field applications such as structural health monitoring. The main sensing parameters for these tests have been strain and/or temperature and now accelerometers with FBG sensors as the measurement medium. The discussion includes a brief overview of FBG sensors, the functionality of FBG sensors as accelerometers, aspects of commercially available instrumentation for monitoring the accelerometers, and applications where they are being used. Specific applications include the use of optical fiber based sensors in the S Blade wind turbine structural health monitoring project where FBG sensor arrays, along with several other sensing technologies for direct comparison, were surface-mounted and embedded in the composite structure of a wind turbine blade and a structural health monitoring system for restoration work on the historic Duomo di Milano.

Multipoint stress/strain measurement in a simple single layered Niobium Titanium wire wounded superconducting sample coil (SSC) was carried out using fiber Bragg grating sensors (FBGs) at low temperature (4.2 K) and at high background magnetic field (8 T) excited by power supply. Ten gratings with different spatial period were fabricated at various positions along a single mode fibre (SMF). The grating location in the SMF sensing array was then mounted at the measuring points on the SSC using stycast 2850 FT. The change in the strain in the SSC. This induced strain, changes the Bragg wavelength of the mounted FBG sensor, which was then recorded using a FS5100 Bragg meter. Experimental results showed that the FBG sensor array was highly reproducible with error of ±0.8 μm/m for high external magnetic field and high current. Also the Young's modulus of the SSC at 900 A, 8 T, and 4.2 K was calculated to be ~ 117 GPa, which is below to the average Young's modulus of the NbTi/Cu superconducting composite wire, which is in the range of 130 GPa at 4.2 K. The loading and unloading characteristic curves of the SSC exhibit reversible behavior without any hysteresis in the operated range. This ensures that the SSC operates linearly within the elastic limit for the applied current and magnetic field. In this paper, we report the behavior of each single turn of the single layered SSC and its corresponding strain due to Lorentz force. The FBG sensing principle is validated by executing various modes of SSC excitation.

Combining fiber Bragg grating (FBG) sensors and finite element simulation analysis, an online monitoring method for non-invasive distributed flow velocity in pipelines has been proposed. A placement strategy has been proposed for the deployment of these FBG sensors to ensure effective sensing of strain. The cross-sensitivity problem of FBG sensors can be solved by differential FBG measurements. The principle of online monitoring of flow velocity based on the flow velocity function and finite element analysis is described and derived. Finite element analysis results show the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {\varepsilon }_{1}- \boldsymbol {\varepsilon }_{2}$ </tex-math></inline-formula> at 45° of the elbow of the bend is quadratically proportional to the flow velocity. Meanwhile, the feasibility of the method is verified by experiments. The calibration results show a fitted correlation coefficient R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.9982 in the velocity range of 4.25-10.62m/s, fitted by least squares to the wavelength data. The repeatability error of the flow measurement of the proposed sensor is no more than 5.06%FS. Compared with the existing literature, the method proposed in this paper has a wider range of flow velocity measurement and applications, especially suitable for applications with strong electromagnetic interference capability and harsher environment, showing great potential for engineering applications, especially in the distributed detection of long-distance pipeline networks.

We report in this paper on the design and development of a novel on-line structural health monitoring and fire detection system based on an array of optical fiber Bragg grating (FBG) sensors and interrogation system installed on a new, precommercial compact aircraft. A combined total of 17 FBG sensors - strain, temperature and high-temperature - were installed at critical locations in an around the wings, fuselage and engine compartment of a prototype, Comp Air CA 12 all-composite, ten-passenger personal airplane powered by a 1,650 hp turbine engine. The sensors are interrogated online and in real time by a swept laser FBG interrogator (Micron Optics sm125-700) mounted on board the plane. Sensors readings are then combined with the plane's avionics system and displayed on the pilot's aviation control panel. This system represents the first of its kind in commercial, small frame, airplanes and a first for optical fiber sensors.