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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Functionalized Carbon Reinforcement Structures with Optical Fibre Sensors for Carbon Concrete Composites
摘要： Here we present our latest efforts in the development of functionalized carbon reinforcement structures (FCSs). FCSs are textile based carbon structures that are functionalized with optical fibre sensors and are designed for the reinforcement as well as structural health monitoring (SHM) of concrete composites. A schematic of a FCS is shown in Fig. 1a. In this example, the FCS contains an optical glass fibre to measure distributed strain profile using the Optical Frequency Domain Reflectometry (OFDR) technique as well as two Fibre Bragg Grating (FBG) sensors to determine local strain and strain direction. The fabrication technique to manufacture FCS has been developed at the Saxon Textile Research Institute (STFI) in Chemnitz, Germany, and the fabrication of the FCS involve embroidering of the carbon fibre filaments and optical glass fibres simultaneously on a polyvinyl alcohol (PVA) nonwoven substrate [1]. PVA was chosen as an embroider substrate since it can be easily removed by dissolving it in hot water and the dissolved PVA further stabilizes the FCS. A manufactured FCS that is embedded in a custom-made concrete block in order to evaluate the sensor performance of the FCS is illustrated in Fig. 1b. After the concrete was set, the concrete blocks containing the FCS were installed in a three point bending test rig (Fig. 1c) and the load transfer from the concrete to the FCS was observed using the integrated optical fibre sensors. In Fig. 1d, the response of the FBG sensor inside the FCS in response to the applied load is illustrated for three consecutive load cycles. As can be seen, the FBG sensor is able to detect the load cycles with a sensitivity of 0.44 nm/% as well as a relatively low hysteresis of 0.011% [2]. Moreover, as indicated in Fig. 1e, four strain peaks were detected using the OFDR during the three point bending test. The four strain peaks results from the integration of the optical fibre in a meander shape (see Fig. 1a) and thus the same optical glass fibre experiences along its length the same load at four different positions. Furthermore, the different magnitudes of the four strain peaks at different time stamps corresponds to the increase in applied load when the concrete block was subjected to the three point bending test [2]. Therefore, the experiments verify that the developed FCS can be applied to monitor spatial strain profiles with a relatively high sensitivity and low hysteresis.
关键词： functionalized carbon reinforcement structures,OFDR,FBG,optical fibre sensors,structural health monitoring,carbon concrete composites
更新于2025-09-11 14:15:04
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Femtosecond Laser Inscribed Sapphire Fiber Bragg Grating for High Temperature and Strain Sensing
摘要： In this paper, a sapphire fiber Bragg grating (SFBG) is fabricated by femtosecond (fs) laser line-by-line scanning method. A third-order fiber Bragg grating is obtained in a single crystal sapphire fiber with a diameter of 60 μm. Compared to the SFBG written by point-by-point method, the SFBG written by the line-by-line method has a higher reflectivity and grating with about 15% reflectivity is achieved when the track length is about 40 μm. The temperature sensing characteristics of this SFBG from room temperature to 1600°C are studied, and the temperature sensitivity of SFBG is 34.96 pm/°C from 1000°C to 1600°C. The strain characteristics are also tested at the temperature of 26°C, 500°C, 1000°C and 1600°C, and the strain sensitivities are 1.42 pm/με, 1.42pm/με, 1.44 pm/με and 1.45 pm/με, respectively. These characteristics show that this SFBG has potential applications in harsh environment structural health monitoring.
关键词： structural health monitoring,femtosecond laser,line-by-line scanning,Sapphire fiber Bragg grating
更新于2025-09-11 14:15:04
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A nonlinear ultrasonic method for real-time bolt looseness monitoring using PZT transducer–enabled vibro-acoustic modulation
摘要： A real-time nonlinear ultrasonic method based on vibro-acoustic modulation is applied to monitor early bolt looseness quantitatively by using piezoceramic transducers. In addition to the ability to detect the early bolt looseness, a major contribution is that we replaced the shaker, which is commonly used in a vibro-acoustic modulation method, by a permanently installed and low-cost lead zirconate titanate patch. In vibro-acoustic modulation, when stimulating two input waves with distinctive frequencies, namely the high-frequency probing wave and the low-frequency pumping wave, the high-frequency probing wave will be modulated by the low-frequency pumping wave to generate sidebands in terms of bolt looseness. Thus, the influence of low-frequency voltage amplitudes on the modulation results, which is ambiguous in previous research, is also analyzed in this article. The results of experiment demonstrated that the lead zirconate titanate–enabled vibro-acoustic modulation method is reliable and easy to implement to identify the bolt looseness continuously and quantitatively. In addition, low-frequency amplitudes of actuating voltage should be selected in a reasonable range. Finally, we compared the vibro-acoustic modulation method with the time-reversal method based on the linear ultrasonic theory, and the result illustrates that vibro-acoustic modulation method has better performance in monitoring the early bolt looseness.
关键词： structural health monitoring,time-reversal,lead zirconate titanate transducers,Bolt looseness,vibro-acoustic modulation,nonlinear ultrasonic
更新于2025-09-11 14:15:04
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On crack propagation monitoring by using reflection spectra of AFBG and UFBG sensors
摘要： Due to their light weight, small size and immunity to electromagnetic interference, Fiber Bragg Gratings (FBG) have shown great potential in structural health monitoring (SHM) area. Ordinarily, FBGs are used as the quasi-distributed sensors to detect structural damage by central wavelengths shifting, which has robust problem in real engineering application. It is found that the FBG reflection spectra can also be distorted with the non-uniform strain field caused by crack. Multiple indices can be extracted from the reflection spectra which can provides more information on the crack propagation. However, till now no researches have been investigated regarding the behaviors of different kinds of FBGs for crack propagation monitoring based on the FBG reflection spectra. In this paper, behaviors of the apodized FBG (AFBG) and the uniform FBG (UFBG) sensors for structural crack propagation monitoring are investigated. The reflective spectral behaviors of both UFBG and AFBG sensors under crack-generated non-uniform strain are illustrated by simulation and experiment. Three spectra indices, namely the central wavelength shift, the ratio of side lobe to main lobe and the information entropy, are proposed to indicate the propagation of the crack. The results show the UFBG sensors have better performance than the AFBG sensors which are more suitable for crack propagation monitoring.
关键词： crack propagation monitoring,uniform fiber Bragg gratings,apodized fiber Bragg gratings,structural health monitoring,spectral distortion
更新于2025-09-10 09:29:36
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The Eye as a Window to Health: Albeit Slow, Research is Progressing on Contact Lenses for Medical Diagnostics
摘要： The idea is a compelling one: a device that looks and feels like an ordinary contact lens but that can continuously monitor a variety of health indicators. For a diabetic, such a lens might update blood glucose levels and, using a built-in flashing LED indicator light, signal when a condition needs attention. Diabetic patients might be saved from the need for repeated finger prick tests and could be monitored for longer periods of time and for a greater variety of parameters at once.
关键词： contact lenses,health monitoring,glucose monitoring,diabetes,medical diagnostics
更新于2025-09-10 09:29:36
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Utilization of single-image normalized difference vegetation index (SI-NDVI) for early plant stress detection
摘要： An imaging system was refined to monitor the health of vegetation grown in controlled conditions using spectral reflectance patterns. To measure plant health, the single- image normalized difference vegetation index (SI- NDVI) compares leaf reflectance in visible and near- infrared light spectrums. The SI- NDVI imaging system was characterized to assess plant responses to stress before visual detection during controlled stress assays. Images were analyzed using Fiji image processing software and Microsoft Excel to create qualitative false color images and quantitative graphs to detect plant stress. Stress was detected in Arabidopsis thaliana seedlings within 15 min of salinity application using SI- NDVI analysis, before stress was visible. Stress was also observed during ammonium nitrate treatment of Eruca sativa plants before visual detection. Early detection of plant stress is possible using SI- NDVI imaging, which is both simpler to use and more cost efficient than traditional dual- image NDVI or hyper- spectral imaging.
关键词： vegetation index,early stress detection,plant health monitoring,imaging
更新于2025-09-10 09:29:36
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Bolted joint integrity monitoring with second harmonic generated by guided waves
摘要： In this study, the second harmonic generation due to the contact nonlinearity caused by bolt loosening is studied experimentally and numerically using three-dimensional explicit finite element simulations. In particular, it is demonstrated that the magnitude of the second harmonic generation normally increases with the loosening of the bolted joint, and there is a reasonable agreement between the numerical simulations and experimental results. The finite element model, which was validated against the experimentally measured data, is further utilized to investigate an important practical situation when a loosened bolt is weakened by fatigue cracks located at the edge of the hole. The numerical case studies show that the contact nonlinearity and the change of the behaviour of the second harmonic generation with the tightening level are very different to the corresponding results with the fatigue cracks. This identified difference in the second harmonic generation behaviour can serve as an indicator of the bolted joint integrity and thus provide early warning for engineers to make decision on the necessity of carrying out further safety inspections. Overall, the findings of this study provide improved physical insights into second harmonic generation for bolt loosening, which can be used to further advance damage detection techniques using nonlinear guided waves.
关键词： Bolt loosening,bolted joint,second harmonic generation,fatigue crack,contact nonlinearity,torque loss,structural health monitoring,guided waves
更新于2025-09-10 09:29:36
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Interfacial nanocomposite sensors (sQRS) for the core monitoring of polymer composites’ fatigue and damage analysis
摘要： The quick development of the smart factory and prognostic and health management (PHM), in the fields of aeronautic, automotive and green energies, is evidencing a need for sensors able to monitor the behavior of composite materials all along their life at the closest of the matter. In situ fabricated conductive polymer nanocomposite (CPC) sensors are bringing an interesting solution to this prospect as they can be integrated homogeneously in the core of composites to probe their deformations and damage. In particular fatigue which is one important mode of failure of polymer composites can be monitored from early signs of damage until the final breakage by analyzing the piezo-resistive response of quantum resistive strain sensors (sQRS) made of carbon nanotubes. We have developed all these aspects in the paper taking the example of a classical glass fibers/epoxy composite instrumented in its core with two sQRS to monitor its short and long term fatigue behavior.
关键词： damage detection,fatigue,structural health monitoring,Piezo-resistive strain sensors,conductive polymer nanocomposites,carbon nanotubes,polymer composites
更新于2025-09-10 09:29:36
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Reconstructed Dynamics of the Imaging Photoplethysmogram
摘要： Human photoplethysmogram (PPG) is one of the signals widely applied for health monitoring. Development of the new techniques made possible evolution of traditional contact PPG which was measured at red and near-infrared light (NIR) to the contactless, imaging PPG (iPPG) that can be recorded at various light wavelengths, including ambient visible light. However, despite the numerous advantages of iPPG its applications demonstrated so far are quite limited. The NIR PPG was previously found to be useful for various applications in the area of physiological and mental health monitoring by utilizing advanced methods of nonlinear time-series analysis applied on its reconstructed dynamics. The main purpose of this study is to demonstrate data-driven approach with time-delay-reconstructed attractor obtained from the iPPG. The results of this study demonstrated that the iPPG dynamics can be reconstructed with fine data resolution, and its time-delay-reconstructed trajectory is almost deterministic, though contains noise. The obtained results might be useful for further applied studies on the iPPG.
关键词： imaging PPG,iPPG,health monitoring,PPG,nonlinear time-series analysis,photoplethysmogram,NTSA
更新于2025-09-10 09:29:36
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Optimisation of optical fibre using micro-braiding for structural health monitoring
摘要： Structural health monitoring is a fast growing area used to assess the state of various structures such as aircraft, building, bridge, wind turbine, pipe, automobile through appropriate data processing and interpretation. This article presents a novel technique of optimising the conventional optical fibres used for structural health monitoring, in order to improve their mechanical properties, and handling during the manufacturing process by micro-braiding the optical fibres. This study investigates and compares the tensile properties of the both micro-braided optical fibre and conventional optical fibres through uniaxial tensile tests. Experimental results show 85% improvement in strain at failure for the micro-braided optical fibre when compared to the optical fibres. Moreover, interfacial shear strength comparison, of the braiding yarn, between optical fibres and micro-braided optical fibre (carried out through micro-bond test) has also been conducted. In addition, the effect of embedding both micro-braided and conventional optical fibre in composite was also investigated by three-point bend test. Overall, the mechanical performance of the composite was not affected by the presence of micro-braided optical fibre. This article will also discuss the process and the advantage of micro-braided optical fibre for structural health monitoring.
关键词： braid angle,micro-braided optical fibre,Structural health monitoring,composites,conventional optical fibre
更新于2025-09-10 09:29:36