Bending Diameter Research Articles

Multifunctional Hard Yet Flexible Coatings Fabricated Using a Universal Step-by-Step Strategy.

Hard yet flexible coatings with multi‐functionalities are useful for foldable displays and marine industries but rare. In this study, a highly cross‐linked multifunctional hybrid coating with ceramic‐like hardness and polymer‐like flexibility is reported. The coating is prepared via a step‐by‐step strategy, where two types of epoxy‐oligosiloxane nanoclusters are first synthesized by sol‐gel chemistry, and amine‐terminated curing agents are used to cross‐link them at room temperature. The coating is highly transparent (>92% transmittance), hard (6‐7H), and flexible (10 mm bending diameter) because of the unique combination of siloxane nanoclusters and polymer networks. Meanwhile, since the coating contains fouling‐resistant telomer and low‐surface‐tension liquid lubricant polydimethylsiloxane (PDMS), it exhibits excellent anti‐biofouling and self‐cleaning properties. The results indicate that the mechanical and antifouling properties of the coating can be easily tuned and prove that the step‐by‐step strategy is a promising and universal method. The novel coatings can meet the needs of applications in foldable displays, marine industries, and other fields.

Analisa Pengaruh Terhadap Kualitas Transfer Data pada Jaringan Computer Berbasis Kabel Serat Optic Menggunakan Metode Regresi Linear

Fiber optic cable is the fastest computer network transmission medium today. In addition to its ability to transfer data faster than other transmission media, fiber optic cable also has factors that can interfere with its performance, one of which is bending. Experiments were carried out on fiber optic cables that were given bending, then tested the data transfer speed for 60 seconds at different bending diameter variations. The results of the test with a maximum speed of 967.35 mbps at a bending diameter of 20 mm, then the speed decreases as the bending diameter is getting smaller, and the slowest speed is at a diameter of 6 mm with a speed of 4.15 mbps. The data was then tested using the validity test, normality test, linearity test and analyzed using simple regression analysis. From the results of the study it can be concluded that there is an effect of bending on the quality of data transfer by 41%.

Experimental study on ageing characteristics of electric locomotive ethylene propylene rubber cable under mechanical–thermal combined action

The train-mounted ethylene propylene rubber (EPR) cables of electric locomotive are partly restricted by the body structure and spatial layout and are in a combined environment of strong mechanical bending and thermal ageing. The degradation characteristics of the insulation layer have not yet received sufficient attention. In order to study the ageing characteristics of EPR cables of electric locomotive under the combined action of machine and thermal, this paper designs a bending–thermal combined ageing test platform for cables with a temperature of 135°C, bending diameter of 393.52 mm, 590.28 mm and unbending cables, and tests after ageing. The product has been tested by infrared spectroscopy, scanning electron microscopy, elongation at break and broadband dielectric spectroscopy. The research results show that the bending outer part of the train-mounted EPR cable is a pain point. Under the combined action of bending and thermal, whether it is microstructure or macro performance, the degradation rate and degree of the bending of outer insulation layer are greater than the value under a single thermal ageing condition. Mechanical bending has an accelerating effect on the ageing of the EPR insulation layer. The research results can provide a reference for the ageing characteristics of the train-mounted EPR cable under the bending–thermal synergy and the evaluation of operating state of the train-mounted EPR cable under bending–thermal operating conditions.

Preparation of semi-solid 6061 aluminum alloy slurry by serpentine channel pouring

The semi-solid 6061 aluminum alloy slurry was prepared by a serpentine channel pouring process. The effects of pouring temperature, bend number and bend diameter on the microstructures were investigated. Microstructural evolution mechanism of the semi-solid slurry during the pouring process was also analyzed. The results show that the grain is refined and the grain roundness is improved by controlling the pouring temperature close to the liquidus temperature, and the nucleation rate of primary α(Al) grains is effectively increased via increasing the bend number and decreasing the bend diameter. The primary grains are not only formed directly from the alloy melt via chilling nucleation and heterogeneous nucleation, but also evolved from the fractured dendrite fragments. Meanwhile, the heat exchange between the melt and the serpentine channel is increased by the “self-stirring” effect in the melt, which also promotes the refinement and spheroidization of primary α(Al) grains.

Fabrication of biaxial polarization-maintaining optical fiber with ultra-low bending-dependent polarization extinction ratio deterioration

Different applications, including interferometers, gyroscopes, and frequency combs, require a single polarized light transmission by maintaining this property against the environmental perturbation. As a new type of polarization-maintaining (PM) fiber, a biaxial PM fiber was fabricated over 30 dB of high polarization extinction ratio (PER) values among two orthogonal axes over a fiber length of 110 m. The PM fiber was manufactured with a combination of an elliptical core and Panda-type geometries. The PER values were demonstrated to be preserved at harsh temperature conditions from −55 °C to +85 °C. The bending loss measurements indicate the biaxial PM fiber has ultra-low bending dependent PER deterioration (<0.5 %) at various bending diameters from 12 mm to 5 mm. The biaxial PM property was also confirmed by the group beat length measurements and found to be less than 1.5 mm at 1550 nm. The optical time-domain reflectometer (OTDR) measurements show that the optical loss of the biaxial PM fiber was below 1.5 dB/km over 3kmlength. The mode-field diameter (MFD) and the numerical aperture (NA) values were also reported along two polarized axes. This novel PM fiber offers a single solution for the elliptical and Panda-type PM fibers utilized for integrated fiber-based sensors and instruments.

Sensing performance of U-shaped fiber in chaotic correlation fiber loop ring down system

We experimentally demonstrated a high sensitivity chaotic correlation fiber loop ring down sensing based on U-shaped fiber optical sensor. The U-shaped fiber optical sensors with different bending diameters were spliced into fiber loops with different cavity lengths to study the influence of cavity length and bending diameter on detection sensitivity. The relationship between cavity length and sensitivity was investigated theoretically and experimentally. The limit of sensitivity was analyzed theoretically and the highest sensitivity of 2253.390 μs−1RIU−1 in the refractive index range of 1.3347–1.3721 was realized experimentally. A handheld probe measuring device was obtained by combining short cavity fiber loop ring down and U-shaped fiber optical sensor, and the probe device can achieve the detection of hemoglobin level with the high sensitivity.

Penetration Failure Mechanism of Multi-Diameter Tungsten Fiber Reinforced Zr-Based Bulk Metallic Glasses Matrix Composite Rod

In order to increase the penetration ability of tungsten fiber-reinforced Zr-based bulk metallic glasses matrix composite rod, two multi-diameter tungsten fiber-reinforced Zr-based bulk metallic glasses matrix composites (MD-WF/Zr-MG) are designed. In MD-WF/Zr-MG-I, the diameters of tungsten fiber (WF) increase gradually from the inside to outside, which is the opposite in MD-WF/Zr-MG-II. Penetration experiment of two kinds of MD-WF/Zr-MG rods into rolled homogeneous armor (RHA) steel target from 1470 m/s to 1630 m/s is conducted. The average penetration depth of the MD-WF/Zr-MG-II rod is higher than that of the MD-WF/Zr-MG-I rod. Penetration failure modes of MD-WF/Zr-MG-I and MD-WF/Zr-MG-II rods are bending, backflow of WFs and shear failure respectively. The failure mode of MD-WF/Zr-MG is affected by the bend spaces and the ultimate bending diameters of WFs. If the bend spaces of all WFs are equal or larger than their ultimate bending diameters, the penetration failure mode is the bending and backflow of WFs, oppositely the penetration failure mode is the shear failure. The MD-WF/Zr-MG rod with shear failure exhibits high penetration ability because of low penetration resistance and little residual material in the crater. When designing MD-WF/Zr-MG, bend spaces of a part of WFs should be smaller than their ultimate bending diameter to cause shear failure.

Laser diode directly backward pumped high-beam-quality 10-kW fiber laser

Fiber lasers have been widely used in the industrial and scientific fields due to their advantages of high conversion efficiency, simple thermal management, and consistent stability. High brightness and high-power fiber lasers are affected by stimulated Raman scattering and transverse mode instability, which limits the power scaling of fiber lasers. Therefore, there are only a few researches achieving a 10 kW-level fiber laser system by laser diode direct pumping or tandem pumping. In this work, we demonstrate an all-fiber laser amplifier based on home-made low numerical aperture (NA) fiber pumped by 976 nm laser diodes. When the signal light is input to the gain fiber with a minimum bending diameter of 12 cm, the beam quality factor &lt;i&gt;M&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt; is about 1.72. The onset of transverse mode instability (TMI) is observed at 2467 W output power, accompanied by beam quality degradation. In order to suppress the onset of TMI, the minimum bending diameter of the gain fiber is changed from 12 cm to 20 cm. And the signal light is input into the gain fiber with a bending diameter of 28 cm. Benefiting from this operation, the fiber laser amplifier achieves maximum output power of 10.53 kW with an optical-to-optical efficiency of 74.04%, and there is no TMI onset observed. However, increasing bending diameter inevitably leads the beam quality to degrade. At the maximum output power, the beam quality factor &lt;i&gt;M&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt; is 2.88. To the best of our knowledge, this is the highest optical-to-optical efficiency and the best beam quality in 10 kW-level laser diodes pumping fiber lasers. Generally, it is believed that reducing bending diameter can suppress TMI by increasing high-order mode loss. However, this rule is not applicable to few-mode fiber lasers. A larger bending diameter leads more high-order modes to be contained in the signal light instead of leaking into the cladding area. Thus, a higher output and poor beam quality are obtained. Also, it is believed that tightly coiled fiber can make mode coupling easier and trigger off TMI, which results in a positive correlation between the TMI threshold and bending diameter. Low NA fibers are very sensitive to bending, and reducing the bend diameter to control the beam quality will result in lower efficiency and a lower TMI threshold. Therefore, although producing a 10 kW-level fiber laser is simple, maintaining good beam quality in the power scaling process is still a challenge. The results of this study will be a valuable reference for high power fiber laser design.

Evaluation of electrical fatigue limits in REBCO coated conductor tapes through static fatigue testing at 77 K

Significant development has been made toward guaranteeing the performance of high-temperature superconducting (RE)Ba2Cu3O7−x coated conductor (CC) tapes in superconducting devices such as high-field magnets and coils. To understand the superconducting behaviors of CC tapes used in such devices under various mechanical- and thermal-induced loads, their mechanical and electromechanical properties should be evaluated in consideration of their application environments. Under static or cyclic fatigue loads, critical current (I c) can degrade as a result of damage to the superconducting layer, even under loads that do not exceed the irreversible stress limits for I c degradation (σ irr). Therefore, prediction of the stress level that can degrade I c under various conditions, such as the endurance limit (stress), is significant for actual coil or magnet applications of CC tapes. A static fatigue tester for CC tapes at 77 K was used in this study to apply a static fatigue load to a 12 mm wide GdBa2Cu3O7−x CC tape specimen under simultaneous axial tension and bending stresses in a U-shaped configuration. Bending mandrels were used to superimpose various bending strains onto the applied static axial tensile strain, and I c across various voltage tap separations was measured over time, up to 100 h. The electrical static fatigue strength and endurance limit for I c degradation were determined based on the 95% I c retention criterion and 100 h of elapsed time, respectively. Results show that bending strain, dependent on mandrel diameter, can greatly influence I c degradation behaviors and that I c can drop considerably in the bent sections compared to the straight sections over time. Analyses of the combined strains in the bent sections allowed the prediction of diameter-dependent electrical static endurance limits under subcritical crack growth. The CC tape’s electrical static endurance limit was greatly affected at smaller bending diameters. When CC coils with diameters smaller than or equal to 50 mm are made using 12 mm wide CC tapes, the electrical static endurance limit is low, roughly ⩽0.63σ irr.

Balloon-like angle and micro-displacement sensor based on bent single-mode fiber

In this paper, a simple balloon-like fiber sensing system based on a Mach-Zehnder modal interferometer by bending single-mode fiber (SMF) into a balloon-like structure is proposed, and the experiment proves that the system can be used for angle and micro-displacement measurement. The sensor system is only composed of SMF. Firstly, the transmission spectrum curves under different sensitive lengths and bending diameters are analyzed. It is found that the maximum extinction ratio of 24 dB can be achieved when the bending diameter of SMF is 8 mm. Then, by comparing the angle and micro-displacement sensitivity under different sensitivity lengths, it is found that the angle and micro-displacement sensitivity of balloon-like structures increase with the increase of sensitivity lengths. The angle measurement sensitivity is 253.1 pm/°, the detection range is −90° ∼ 90°, and the micro-displacement measurement sensitivity is 327.4 pm/μm. This sensor system has a great potential in the field of angle and micro-displacement measurement, and provides a new idea for angle and micro-displacement measurement.

Numerical simulation of flow characteristics in vertical elbows of pneumatic conveying

In this paper, the numerical simulation method of computational fluid dynamics (CFD) is used to establish the flow field model of elbow, including the determination of the applicable gas-solid two-phase flow model and the establishment of the actual basic fluid dynamics equations. After meshing the elbow with ICEM software, the effects of air velocity, bend diameter ratio and other factors on the flow characteristics of the elbow pneumatic conveying are simulated based on FLUENT software. The results show that in the pneumatic conveying with vertical elbows, the flow characteristics of gas-solid two-phase flow have obvious differences with the changes of many factors.

Highly fluorine and ytterbium doped polarization maintaining large mode area photonic crystal fiber via the sol-gel process

Highly Yb-doped silica glass with low refractive index for fabrication of Yb-doped large-mode-area photonic crystal fiber (LMA PCF) is in favor of decreasing fiber length and thus increasing the threshold of nonlinear effects in pulse laser amplification. Accordingly, fluorine incorporation in highly Yb-doped silica glass is vitally important to compensate the sharp increase in refractive index caused by ytterbium and aluminum ions. In this work, the fluorine doping concentration in Yb/Al/P/F co-doped silica glass was significantly improved by a modified sol-gel method combined with high temperature sintering. The effects of fluorine doping on glass structure have been investigated in details by Raman spectra, nuclear magnetic resonance (NMR) and advanced pulse electron paramagnetic resonance (EPR) measurements. The incorporation of fluorine yields Si-F bonds and Yb-F bonds formation and leads to the mild change in spectroscopic properties. An optimized silica core glass rod with high Yb (0.77 wt.%) and fluorine (0.8 wt.%) doping concentration, low refractive index and acceptable optical quality was prepared. Based on the highly fluorine and ytterbium doped silica core glass, a polarization maintaining (PM) photonic crystal fiber with 40 µm core was prepared and the pump absorption coefficient at 976 nm was ∼6.5 dB/m. An average amplified power of 103 W was achieved from a 2-m-long PCF with the bend diameter of 23 cm. The slope efficiency (with respect to pump power) was 52% with laser beam quality factor M2 of 1.46.

2.7 kW co-pumped fiber amplifier based on constant-cladding tapered-core fiber

A constant-cladding tapered-core (CCTC) fiber with the core size varying monotonously along the length was fabricated. The core/cladding diameters of narrow end and wide end are 24/400 μm and 31/400 μm, respectively. A forward-pumping master oscillator power amplifier (MOPA) was constructed to investigate the laser performance of this fiber under two bending schemes (8–14 cm and 12–16 cm). The maximum output power is scaled up to 2704 W with a slope efficiency of 82.1% in the case of bending diameter ranges from 12 cm to 16 cm, the M2 factor at 2548 W output power is 2.16, and no signs of transverse modal instability (TMI) and stimulated Raman scattering (SRS) were observed in whole experiment. The above result verifies the potential of power scalability of CCTC fiber, and the laser performance can be further enhanced by fiber design optimization and other TMI suppression methods.

Aging Assessment of XLPE/CSPE LV Nuclear Power Cables Under Simultaneous Radiation–Mechanical Stresses

The preliminary results of an ongoing laboratory cable aging program are reported in this article. This work deals with the effect of simultaneous radiation–mechanical​ aging on the electrical and mechanical properties of XLPE/CSPE low-voltage unshielded nuclear power cables. The dielectric response, particularly the complex permittivity and the polarization/depolarization current (PDC), were investigated. At the same time, the Shore D hardness measurement was conducted as a mechanical property test. Cable samples were coincidingly aged under a bending diameter of 15 cm and a total dose of 240 kGy γ-irradiation at a 0.5 kGy/h dose rate. The real and imaginary parts of permittivity were investigated over a frequency range from 200 μHz to 1 Hz. The electrical parameters presented a monotonic increase with aging. Besides, the cable hardness has increased with increasing the radiation dose. Furthermore, the insulation conductivity has risen with aging, which strongly correlates with the imaginary permittivity at 1 mHz. The obtained results showed an excessive degradation of the cable samples under the combined radiation–mechanical aging as the insulation electrical and mechanical properties showed a good agreement.

Experimental Study On the Critical Current of CORC Cable Under Cyclic Bending-straightening

To develop the application potential of conductor on round core (CORC) cables in the next generation of fusion magnets and accelerator magnets, fully automatic mechanized winding technology is required for the long CORC cables manufacturing. Meanwhile, the manufacturing and usage of the CORC cable are both limited by the strain sensitivity of the wound ReBCO tape on the CORC cable, because the processes may cause the superconducting layer of the ReBCO tape damaged when the strain limit is exceeded. The strains can arise from the manufacturing, bending, cooling, and operation of the cable and magnet, especially for the needed cyclic bending-straightening procedure for a long and multilayer cable winding layer by layer. Thus in this manuscript, a 1-m-long 12-layer CORC cable was manufactured to study the influence of cyclic bending on the critical current carrying performance of the CORC cable. It is consisted of 28 ReBCO tapes from Fujikura with 4 mm width and 0.05mm substrate thickness. The central core has an outer diameter of 3.85 mm. The cyclic bending-straightening experiment was conducted with a bending diameter of 900 mm and 700 mm, the Ic was tested at 77 K and self-field. After the cyclic bending test, the sample was bended to a diameter of 95 mm, which is planned to be used for the following insert solenoid coil, and has been verified no influence on the critical current carrying performance if bended without cyclic bending-straightening treatment. The results show that the required diameter for the reel experiencing cyclic bending-straightening procedure for ReBCO cable winding is suggested to be larger than 700 mm, especially for the equipment used for multilayer cables winding.

Large-area 280 nm LED flexible sterilization light source with improved thermal performance

This study focuses on the LED flexible sterilization light source at 280 nm wavelength, and the adjustment of the thickness and area dimensions of the heat dissipation substrate to explore the thermal behavior. The empirical results indicated the priority order for factors affecting the heat dissipation of the substrate to be k > A > t. At the same time, a large-area, flexible, deep-ultraviolet light-emitting diode (DUV LED) was successfully obtained with an area of 5 × 5 cm2 and a 3 cm bending diameter. This sterilization light source was used to carry out the sterilization inactivation test with Escherichia coli. The sterilization rate reached 95% in 60 s. The good sterilization rate and flexibility of the sterilization light source will improve the sterilization performance of the applied product.

Sensitivity-Enhanced Moisture Sensor Based on θ-Shape Bending Fiber Coated With Copper-Polyvinyl Alcohol Thin Film

This paper presents a compact and easy fabrication of a moisture sensing probe based on macro-bending loss induces in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> -shaped Mach-Zehnder interferometer (MZI) for the first time. The interferometer configuration was simply fabricated by bending a segment of single-mode fiber (SMF) into two elliptical loops divided by a fiber bridge to form a shape of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> symbol without any splicing. The sensing mechanism is reliant on the optical path difference among the core and cladding modes in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> -shaped configuration induces by appropriately adjusting the SMF bending diameters, which causes the resonance wavelength to shift towards relative humidity (RH) variation. Two sensing probes based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> -shaped bend structure with an optimized bending diameter of 1.5 cm were fabricated to investigate the effect of Copper-Polyvinyl Alcohol (Cu/PVA) coatings, which served as a moisture-sensitive layer on the sensor sensitivity. The coated macro-bend structure exhibits an excellent sensitivity of −1.469 nm/RH% with a polynomial fitting coefficient of 99.645% in the 55%-97% relative humidity (RH) range, which is 1.4 times higher than that of an uncoated structure. This result presents a feasible and practical method to construct excellent sensitive optical fiber moisture sensors based-bending loss and Cu/PVA nanostructured coatings.

Single-mode Optical Fiber: An Investigation for the Bending Loss at Wavelength 650 nm

Abstract: In modern time, the optical fiber communication has revolutionized the data transmission process and contributed vitally to the development of qualitative and speedy telecommunication systems. The arteries of this system are optical fibers which carry information as light signals and as fast as speed of light. But these light signals suffer energy losses during their propagation through the optical fibers. For the effective functioning of an optical fiber communication, it is necessary to know and prevent the prevailing energy losses (especially external bending losses) of the optical fibers. In this paper, the external bending loss of optical power while propagating through a single-mode optical fiber has been investigated. Further, the effects of wrapping turns (1 to 6 turns) and bending diameters (2 cm ≤ D ≤ 12 cm) on the power loss of laser at a wavelength of 650 nm have been studied. Keywords: Single-mode optical fiber, Bending loss, Attenuation coefficient, Wrapping turns, Bending diameter. PACs: 42.81.-I, 78.67.Pt, 42.25.Bs.

Experimental study on internal precast beam–column ultra-high-performance concrete connection and shear capacity of its joint

Precast reinforced concrete structures are increasingly being studied and adopted for their potential advantages. In this study, we tested five precast beam–column connections whose regular shape beams and columns were connected with lap-spliced steel bars in ultra-high-performance concrete (UHPC). A monolithic beam–column connection as a control specimen was also tested under reverse cyclic loading. The results showed that the application of lap-spliced steel bars in UHPC is feasible for connecting the beam and column in the joint. It is recommended that the minimum straight bar lap length in UHPC can be determined as 15db (db is the bar diameter), and the minimum hooked bar lap length was determined as 11db (with a straight extension length of 8db, inside bend diameter of 4db, and tail extension length of 5db). UHPC significantly enhanced the shear capacity of the joint owing to its high shear strength. The increases in the fiber volume fraction and stirrup volume ratio enhanced the damage-resistance property of the joint, which is beneficial for the development of beam-end plastic hinges. Therefore, the ductility of the beam–column connection can be further increased. The increase in axial load enhanced the shear capacity. To design a “strong joint,” a theoretical strut-and-tie model was proposed based on Mohr–Coulomb theory applied to the joint core to accurately calculate the UHPC joint shear capacity.

Design against splitting failures in reinforced concrete due to concentrated forces and minimum bend diameter of reinforcement

Plastic bending of reinforcement bars against mandrels is the usual procedure to provide bends and hooks for steel reinforcement bars. Minimum mandrel diameters are usually given in to codes of practice, depending on the type of detail and diameter of the bar. These recommendations for the bend diameter ensure a safe transfer of forces, avoiding splitting failures that may potentially limit the resistance of the detail. In most cases, these recommendations are largely based on a number of experimental works performed several decades ago. At that time, these investigations were performed on reinforcement and concrete with lower strengths than currently used. This paper presents the results of a comprehensive research programme on bend detailing and required mandrel diameter to avoid local concrete failures leading to spalling of the concrete cover. The results of an experimental programme are presented, showing the influence of different parameters such as the mandrel diameter, the bending angle and the concrete cover. The tests were instrumented with advanced measurement techniques (fibre-optic measurements and digital image correlation), showing that consistent modelling of the transfer of forces can be performed on the basis of the geometrical and mechanical parameters of the details.