The article discusses five year long measurements of strains of a concrete floor of a hangar. That hangar, originally meant for servicing light military aircraft, was rebuilt with a view to making it ...fit for servicing larger and heavier passenger planes. As part of that redevelopment, a new floor - reinforced concrete slab, capable of withstanding the weight of the planes - was constructed. In the areas of the floor where the greatest loads occur, ie. in the areas of the concrete slab on which the wheels of the three undercarriage legs rest, three strain rosettes were installed so that the slab strains could be measured. The rosettes were connected to two meters - dataloggers. The latter were programmed in such a way as to register the measured strains and additionally temperatures many times during every 24 hours. The monitoring process, conducted in such an automatic way, demonstrated the occurrence of strains resulting from service load, aging of the reinforced concrete, as well as changes in its temperature.
Soil frost deformation significantly influences engineering projects in cold regions. The anisotropic behavior of soil, involving surface and internal deformation in three dimensions (3D), introduces ...inaccuracies in evaluating freeze–thaw geological hazards. To explore the relationship between internal strain and surface displacement of soil in a 3D space during the freezing-thawing process, a platform for monitoring coupled surface-internal deformation in 3D were developed using binocular recognition technology and a novel 3D strain rosette. Subsequently, a freezing-thawing model test of soil in Dalian Offshore Airport filling is conducted using the platform. The results show that, the internal strain of soil is closely associated with the boundary conditions of the test unit. During freezing test, the vertical strain exhibits a more significant increase in comparison to the horizontal strain. Surface displacements in soil primarily occur during the initial freezing and thawing stages. The variation of surface horizontal displacement in each direction is minimal throughout the freezing-thawing process. A surface freezing boundary leads to an increment in internal strain, while the deep frozen stress relief causes the soil surface expand during thawing. This study provides a suggestion for the control of the cold source in cold region engineering.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A BWIM system is proposed using two FBG based sensors.•The strain experienced by the bridge girder due to the motion of a loaded vehicle has been recorded and analyzed.•Different parameters of the ...vehicle like load, velocity and separation of the front and rear wheels (approximate length of vehicle) are measured.•The experiment is repeated with different angular orientations of FBG (0°, 45°, and 90°) with reference to the line of motion.•The experiment is repeated with different angular orientations of FBG.•Considering the system as a simply supported beam with concentrated load at a point, simulation study is performed with MATLAB too..
A Weigh in Motion (WIM) system is proposed, employing two fiber Bragg grating (FBG) sensors to evaluate the strain at a point on a prototype bridge due to a moving vehicle. The FBG's are fixed at two different longitudinal girders of bridge along the line of motion at different orientations. The parameters of investigation include strain developed in the proximity of FBG’s and speed of the vehicle. The response has been studied by arranging system of FBG sensors in the form of a rosette. It can be deduced from results that the suggested WIM structure could efficiently monitor variations in the load and speed of advancing vehicles over the bridge. The ideal arrangement of FBG’s in the sensor is found to be that oriented along the bridge axis due to a high sensitivity of 0.36μɛ/gram and linearity with a good coefficient of correlation of about 0.99 than other orientations of FBG. The principal strains obtained from the FBG rosette are in close correlation with the values simulated using numerical tool MATLAB.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flexible electronic devices are attracting much attention on account of their great potential in artificial intelligence, electronic skin, and biomedicine. However, the poor stretchability, ...conductivity, and machinability of flexible materials limit the application of flexible electronic devices in practical environments. Herein, hydrogels with excellent mechanical, electrical, and processable properties are synthesized by introducing deep eutectic solvent (DES) and MXene into a polyvinyl alcohol (PVA) matrix, which shows more than 2700% tensile strain, and 1.21 S m−1 conductivity. Interestingly, hydrogels also exhibited 3D printable properties, enabling the fabrication of sensors with complex structures in a short period of time. Besides, the serpentine lines strain sensor is successfully prepared by digital light processing (DLP) 3D printing and assembled into a bidirectional strain rosette sensor and omnidirectional strain rosette sensor, which could recognize the direction and magnitude of stress. More importantly, the omnidirectional strain sensor can accurately distinguish the signal responses of different directions and sizes generated by ping‐pong players swinging the racket, showing excellent strain recognition ability. In brief, the hydrogels designed are expected to realize the manufacture of large‐scale and low‐cost flexible sensors through a simple preparation process, which provides a new idea for the manufacture of flexible electronic devices.
The designed 3D printable hydrogel with excellent mechanical and electrical properties is expected to realize the manufacture of large‐scale and low‐cost flexible sensors through a simple preparation process, which provides a new idea for the manufacture of flexible electronic devices.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The results of strain measuring experiments, with the help of rosettes consisting of fiber Bragg grating sensors (FBG) embedded at the manufacturing stage in a polymer composite material are ...considered in this paper. The samples were made by the direct pressing method from fiberglass prepregs. A cross-shaped sample was tested under loading conditions corresponding to a complex stress state. A variant of strain calculations based on experimental data is discussed. The calculations were performed under the assumption of a uniaxial stress state in an optical fiber embedded in the material. The obtained results provide a reasonable explanation of the absence in the conducted experiment of two peaks in the reflected optical spectrum, the presence of which follows from the known theoretical principles. The experimental result with two peaks in the reflected optical spectrum was obtained for the same sample under a different loading scheme. The proposed variant of the numerical model of the experiment and the results of numerical simulation made for FBG rosettes embedded in the material allowed to estimate error in the strain values calculated on the assumption of the uniaxial stress state in the optical fiber and in the presence of two peaks in the reflected optical spectrum.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The full-field multiaxial strain measurement is highly desired for application of structural monitoring but still challenging, especially when the manufacturing and assembling for large-area sensing ...devices is quite difficult. Compared with the traditional procedure of gluing commercial strain gauges on the structure surfaces for strain monitoring, the recently developed Direct-Ink-Writing (DIW) technology provides a feasible way to directly print sensors on the structure. However, there are still crucial issues in the design and printing strategies to be probed and improved. Therefore, in this work, we propose an integrated strategy from layered circuit scheme to rapid manufacturing of strain rosette sensor array based on the DIW technology. Benefit from the innovative design with simplified circuit layout and the advantages of DIW for printing multilayer structures, here we achieve optimization design principle for strain rosette sensor array with scalable circuit layout, which enable a hierarchical printing strategy for multiaxial strain monitoring in large scale or multiple domains. The strategy is highly expected to adapt for the emerging requirement in various applications such as integrated soft electronics, nondestructive testing and small-batch medical devices.
In the 2017 Jiuzhaigou earthquake sequence, the distribution of aftershocks in the north of the main earthquake was scattered, while the distribution of aftershocks in the south of the main ...earthquake was linear and concentrated. The objective of this inquiry is to analyze the dynamic causes underlying such divergent patterns, relying on the horizontal strain rosette, areal strain (As), and the coefficient of accommodation (Ca) based on the regional strain rate. The following two conclusions are obtained: (1) approximately one-third of the aftershocks with focal mechanisms in the north of the main shock are thrust-type earthquakes. Because the direction of regional tectonic principal compressional strain is perpendicular to the fault trend north of the main shock, generating thrust-type earthquakes on low dip-angle faults is indeed easy. Simultaneously, the overall thrust-type focal mechanism north of the main shock and the poor consistency between plate tectonic movement and fault movement caused by the seismic sequence lead to substantial scattered aftershocks in the north of the main shock. (2) One of the aftershocks with focal mechanisms in the south of the main shock is a reverse strikeslip type, while the other 30 are strike-slip type earthquakes. Moreover, the angle between the regional tectonic principal compressional strain direction and the fault trend in the south of the main shock is large, which makes it easier for faults in the south of the main shock to produce strike-slip-type earthquakes. Simultaneously, the overall strike-slip focal mechanism in the south of the main shock, the good consistency between fault movements caused by the seismic sequence, and plate tectonic movements lead to more linear and concentrated aftershocks in the south of the main shock. The findings are significant for investigations into the seismogenic properties and activity of the Huya Fault located on the northeastern margin of Bayan Har Block.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ships sail in complicated marine environment, affected by winds, waves, impact and other loads. On the base of hull structure stress and strain monitoring, this paper put forward two types of fiber ...Bragg grating (FBG) strain rosettes to measure the complex stress and strain of hull plane. Several main factors affecting the strain transfer ratio were analyzed to optimize the type and size of strain rosettes through the finite element analysis. Finally, experimental research on the optimizing FBG strain sensor was conducted through the tensile machine, and compared with the results of electric resistance strain. It is concluded that the designed strain rosette structure has a good sensitivity, resilience, and long-term stability, which is fully applicable to hull structure health monitoring under the environment of corrosion and fatigue loading.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Thin gold films on silicone display large reversible change in electrical resistance upon stretching. Eutectic liquid metal conductors maintain bulk metal conductivity, even upon extensive ...elongation. When integrated together, the soft metals enable multidirectional, large strain sensor skin. Their fabrication process combines thermal evaporation of thin gold film patterns through stencil mask with microplotting of eutectic gallium indium microwires, and packaging in silicone rubber. Using three-element rectangular rosettes, we demonstrate a sensor skin that can reliably and locally quantify the plane strain vector in surfaces subject to stretch (up to 50% strain) and indentation. This hybrid technology will find applications in soft robotics, prosthetics and wearable health monitoring systems.
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