Bending Diameter Research Articles

Facile fabricated transparent anti-smudge coating with high hardness and excellent flexibility from MTQ and branched silicone resins

The demand for high-transparent functional coatings with glass-like hardness, polymer-like flexibility, and anti-smudge properties has increased significantly, especially for foldable touchscreens. However, it is challenging to achieve all the required properties in a coating because the realization of these properties may conflict with each other. In this study, we present a facile method for preparing a special organic-inorganic hybrid coating by utilizing epoxy MTQ silicone resins and amine-terminated hyperbranched polysiloxane (HPSi). The chemical structure of the MTQ resin was fine-tuned to obtain the optimal M/T/Q ratio, and a novel HPSi with rich crosslinking sites and excellent flexibility was prepared as the curing agent. The resulting hybrid network imparted the coating with exceptional hardness (pencil hardness, 7–9H) and excellent flexibility (<2 mm bend diameter). In addition, by modifying the MTQ resin with fluorosilane, the surface energy of the coating was reduced to 14.8 ± 0.4 mJ/m2 and its anti-smudge and self-cleaning properties were improved without sacrificing the transparency of the coating (99.4 % at 550 nm). Notablely, even after 1000 cycles of steel wool abrasion, these coatings still maintain their outstanding performance. This study provides a promising strategy for the development of hard, flexible, and anti-smudge coatings suitable for foldable displays and other related fields.

Research on Structural Parameter Optimization and Springback Compensation Methods of a Steel Bar Hoop Bending Machine

After being processed into a certain shape by a stirrup bending machine, steel bars are used as the skeleton of reinforced concrete in construction. The accuracy of their bending directly affects the bearing capacity of reinforced concrete. In order to improve the accuracy of the springback angle of steel bars after bending, this paper focuses on optimizing the structural parameters of the steel bar bending machine and controlling the springback angle of steel bars. The influence of the support shaft diameter, bending crankshaft diameter, and bending crankshaft radius on the springback angle of steel bars is analyzed using ANSYS explicit dynamic simulation and experimental analysis. By combining orthogonal experimental methods, the bending structural parameters were optimized, including a support shaft diameter of 20 mm, a crankshaft bending diameter of 40 mm, and a crankshaft bending radius of 80 mm. This can effectively reduce the springback angle of the steel bars and improve the accuracy of the bending angle after bending. In addition, in order to improve the control accuracy of the steel bar springback angle, a cubic spline interpolation method was proposed, and the collected steel bar springback angle data were fitted using Matlab. At the same time, comparisons were made between the least squares method, polynomial interpolation method, and cubic spline interpolation method. The results show that the compensation formula obtained by using the cubic spline interpolation method can effectively improve the control accuracy of the steel bar bending springback angle.

Co-sputtered Cu–Ag-based ZnO–Cu(Ag)–ZnO film enabling efficient flexible CuZnSnS solar cells with desirable mechanical endurance

To further enhance the mechanical endurance of ZnO–Cu–ZnO (ZCZ) films and CuZnSnS (CZTS) solar cells with deposited ZCZ films (ZCZ CSCs), Ag elements were introduced into metallic layers of ZCZ films using magnetron sputtering Cu–Ag co-sputtering techniques. The Ag addition effectively reduced the stresses generated during the growth of the Cu film, resulting in the suppression of three-dimensional island growth and the formation of a more uniform metallic film. Specifically, ZnO–Cu/Ag(35 W)–ZnO (ZCA35Z) films exhibited an average transmittance (T-ave) of 89%, outperforming the ZCZ film with a T-ave of 80%, achieved by increasing the continuity of metallic layers. Moreover, ZCA35Z CSCs demonstrated a higher power conversion efficiency (PCE) value of 6.38% compared to ZCZ CSCs (6.01%) without bending. Additionally, the PCE value of ZCA35Z CSCs showed a 9% improvement over ZCZ CSCs at a bending diameter of 10 mm. Remarkably, even after 1000 bending cycles, the PCE value of ZCA35Z CSCs exhibited a substantial 15% enhancement compared to ZCZ CSCs, which can be attributed to the continuous Cu films enhancing carrier migration and reducing optical losses. This new method to enhance the mechanical endurance of ZCZ films and ZCZ CSCs by increasing Cu film continuity via Cu–Ag co-sputtering presents a promising approach to boost the performance of flexible electronics.

Experimental study on anchorage performance and mechanism of hooked bars with a pre-yield anchorage failure

In RC exterior beam-column joints, reliable anchorage of beam bars using hooked bars is a common approach to ensure sufficient joint rotation capability. The anchorage failure criterion and the influence of axial load and side cover on anchorage strength are unclear with the limitings of the existing test setup and test approach. Twenty-two simulated beam-column joint tests with hooked bars anchorage were therefore conducted. A specially designed test setup was proposed to ensure the simultaneous failure of hooked bars within a specimen, while a novel approach was employed to separate the anchorage force of the hook portion into bearing and bond forces based on stress distribution measurement. The experimental results show that the anchorage strength of hooked bars and hook portion bearing strength increase as side cover thickness and axial load increase, which may potentially alleviate joint congestion. Additionally, the study identifies that the hook portion bearing strength dominates the anchorage failure mechanism of hooked bars, prompting the proposal of an anchorage failure criterion. Based on this criterion, models for anchorage strength and anchorage force-slip relationship were proposed, which are applicable to hooked bars with varying inner bend diameters in actual structures. To examine the safety and validity of the proposed equation for anchorage strength, it was compared against a hooked bar test database with 363 anchorage specimens, as well as several existing models. The database analysis showed potential safety risks with the GB50010-2010 model. Notably, the proposed model demonstrated the highest accuracy in predicting the anchorage strength of hooked bars.

The Critical Current of REBCO Coated Conductors Subjected to a Mechanical Loading at Varying Angles

High-temperature superconducting REBCO coated conductors and cables made from them are required in the building of fusion reactors, high-field magnets, and other high-current and high magnetic field devices. In the construction phase, the coated conductors undergo mechanical loading throughout the coated conductor production, cable manufacturing and when the resulting device is put in operation. Therefore, a simple method for investigating the loss of critical current after bending at different diameters and angles would be helpful. Here, we present a setup designed with simplicity in mind, allowing easy replication of testing conditions. As an example, the behaviour of two conductors has been characterized. We found differences in critical bending diameter when CC tapes were bent at 30 degrees angle and 45 degrees angle. The measurements were complemented by numerical and analytical calculations. The analytical calculations are an idealized 2D model serving as a first approach method for a fast prediction of loading severity. 3D numerical modelling of the measurement setup was performed in finite element software ANSYS, allowing us in-depth investigation of the strain/stress distribution in the multilayer structure of REBCO coated conductors. Scanning electron microscope study of the surface of the superconducting layer on one of the samples helped explain the measurement results.

Flow characteristics of moist-mixed materials for shotcrete: From experiment to CFD-DEM simulation

Moist-mixed materials for shotcrete is an effective way to solve the volume control of shotcrete equipment in small and medium cross-section tunnels. The material of moist-mixed materials for shotcrete is characterized by cross-scale particle composition, and the problems of difficult dust control and short conveying distance remain unsolved. The pneumatic conveying simulation of the moist-mixed materials for shotcrete is studied using the CFD-DEM method. At the same time, a pipeline test system is designed, and the effectiveness of the CFD-DEM coupling model is verified by comparing the pressure drop and flow pattern with the field experiment. The model is used to study the pressure drop characteristics under different tilt angles, lifting angles, bend diameter ratio, and bend angle, involving three aspects: pressure drop in acceleration section (PDAS), unit pressure drop in stable section (PDSS), and energy loss caused by the elbow (ELE). The pressure drop model of pneumatic conveying of moist-mixed materials for shotcrete is established, and the relationship between the PDAS, PDSS, and ELE is obtained. The relationship between the Froude number and solid-gas ratio is clarified, and the calculation formula of maximum feed rate or minimum air flow rate is deduced. The velocity and spatial position distribution of particles at different tilt and lifting angles are revealed, and the elbow's main wear areas and wear rates at different bend angles and bend diameter ratios are obtained. The fundamental research has realized the unification of experiments and numerical simulation. The pressure drop law brought can guide further research on long-distance pneumatic conveying of moist-mixed materials for shotcrete.

Mitigation of TMI in an 8 kW tandem pumped fiber amplifier enabled by inter-mode gain competition mechanism through bending control.

In this work, the impact of fiber bending and mode content on transverse mode instability (TMI) is investigated. Based on a modified stimulated thermal Rayleigh scattering (STRS) model considering the gain competition between transverse modes, we theoretically detailed the TMI threshold under various mode content and bending conditions in few-mode fibers. Our theoretical calculations demonstrate that larger bending diameters increase the high order mode (HOM) components in the amplifier, which in turn reduces the frequency-shifted Stokes LP11o mode due to the inter-mode gain competition mechanism, thus improving the TMI threshold of few-mode amplifiers. The experimental results agree with the simulation. Finally, by optimizing the bending, an 8.38 kW output tandem pumped fiber amplifier is obtained with a beam quality M2 of 1.8. Both TMI and stimulated Raman scattering (SRS) are well suppressed at the maximum power. This work provides a comprehensive analysis of the TMI in few-mode amplifiers and offers a practical method to realize high-power high-brightness fiber lasers.

Influence of bending and heat treatment under high isostatic pressure on synthesis reaction and transport critical current density in isotopic IMD Mg11B2 'wind and react' coils

We show for the first time the results for small coils, which were wound with unreacted magnesium diboride (MgB2) wires with nano-amorphous isotopic boron (11B) by using combined internal magnesium (Mg) diffusion (IMD) and hot isostatic pressing (HIP) techniques. The small coils with a diameter of 20 mm or 10 mm were annealed under low (0.1 MPa) and high (1.1 GPa) isostatic pressure. The 10 mm coils annealed under high isostatic pressure of 1.1 GPa had significantly increased critical temperature (Tc), irreversible magnetic field (Birr) and transport critical current density (Jtc), with significantly accelerated Mg diffusion and improved homogeneity of the Mg11B2 material. Moreover, our findings show for the first time that the bending of the unreacted IMD Mg11B2 wires significantly affects the synthesis reaction under the low and high isostatic pressure. Our findings also show for the first time that diffusion of Mg during heat treatment under high isostatic pressure is completely different than during heating under low isostatic pressure. Mg diffusion under low isostatic pressure annealing is mainly dependent on the heat treatment temperature, bending diameter and 11B layer density. This Mg diffusion is related to the simultaneous formation of the superconducting phase. However, the diffusion of Mg under high isostatic pressure heat treatment is mainly dependent on the isostatic pressure, 11B layer density and Mg state (liquid or solid). Our results indicate that liquid Mg is first pushed into the 11B layer by high isostatic pressure and then a superconducting phase is formed.

Research on temperature-insensitive blood glucose concentration sensor with U-shaped SMF

In this manuscript, a temperature-insensitive U-shaped single-mode fiber (SMF) blood glucose concentration sensor is proposed. A balloon-shaped SMF is first burned by a flame to form a spindle shape, and then a U-shaped SMF is formed by the second burning. The U-shaped SMF sensor produced by this process is not sensitive to temperature. The bent fiber causes part of the energy to couple into the cladding modes, which results in modal interference. In the experiment, U-shaped SMF sensors with different bending diameters are made to study the sensitivities of blood glucose concentration and temperature. Experimental results show that the blood glucose concentration sensitivity of the sensors is up to −0.564 nm/(mmol/l) in the range of 1.1 mmol/l ∼ 34.1 mmol/l. The sensors are insensitive in the temperature range of 5 ℃ ∼ 45 ℃. In addition, the sensors have the advantages of small size, low cost and simple process.

Investigation on the wall thickness variation of an eccentric tube in the rotary draw bending process

PurposeWhen bending a large diameter thin-walled tube, the thickn ess of outer side wall will reduce greatly, which leads to a decrease of structural strength of the tube. To solve this problem, this paper investigated the deformation principles of an eccentric tube in the rotary draw bending process, trying to find a way to reduce the wall thickness difference between inner and outer diameters.Design/methodology/approachAn finite element model is established for analyzing the deformation of an eccentric tube in rotary draw bending process. The wall thickness distribution of the formed pipe was analyzed along the axis and diameter, respectively.FindingsIt is found that there exists an optimal eccentricity between the inner and outer circle center of the tube cross-section. If the eccentricity of the tube is chosen properly, it is possible to get a bent tube with equal thickness of inner and outer side walls. In addition, it is also found the optimal eccentricity on the cross-section can be influenced by bending radius, wall thickness, diameter and bending angle. The optimal eccentricity increases greatly with the decreasing of bending radius, the increase of outer diameter and the increase of wall thickness. The influence of bending angle on the optimal eccentricity can be divided into two situations. When the bending angle is small, the optimal eccentricity increases with the increase of bending angle. When the bending angle exceeds a certain value, the pipe enters a stable forming state. The optimal eccentricity of the stable forming region does not change with the bending angle.Originality/valueSuch a research is beneficial for reducing the thickness difference between inner and outer side walls in the rotary draw bending process.

Experimental study of buoyancy and centrifugal effects on supercritical heat transfer in U-bend and contiguous straight tubes

The buoyancy-induced thermal non-uniformity in heat transfer of supercritical fluids is a major issue that must be addressed in transcritical systems like organic Rankine cycle. In cases where U-bends are involved in heat exchangers, the introduction of centrifugal effect and its decaying nature makes the heat transfer process even more complex. In this work the buoyancy and centrifugal effects on local heat transfer to supercritical R410A were experimentally studied in a U-bend and its contiguous horizontal straight tubes (tube diameter d = 4.35 mm, bend diameter D = 43.5 mm). Measurements were performed at four circumferential positions along the heated length. Results show that bend-induced enhancement reached the maximum at the bend center, where heat transfer coefficients at the outside, top, bottom, and inside increase by 88%, 49%, 28% and 19% respectively. U-bend also caused a significant enhancement on contiguous horizontal straight tubes. In the upstream straight section, the affected distance can reach 11.5d, and the downstream affected range is more than 23d. The enhancement and the affected distance generally increased with heat flux, mass flux, and inlet temperature, but barely affected by pressure. Further analysis indicates that the centrifugal force dominated heat transfer in the bend section. Moving away from the bend, it gradually decayed, buoyancy force recovered and eventually played the major role. Existing dimensionless numbers failed to represent this transition, and a new parameter ψ* was proposed to evaluate the competition between the buoyancy effect and the decaying centrifugal effect. With a threshold value of 1, ψ* can quantitatively characterize the local heat transfer.

Experimental investigation of heat transfer to supercritical pressure R410a in a U-tube

To properly guide the design of vapor generators in transcritical organic Rankine cycles, heat transfer characteristics of supercritical pressure R410a in a horizontal U-tube was experimentally investigated. The pipe diameter d and bend diameter D of the U-tube are 4.35 mm and 43.5 mm, respectively. Measurements were performed at mass flux of 300–1600 kg/(m2s), heat flux of 25–80 kW/m2, inlet temperature of 283–343 K, and pressure of 5–5.88 MPa. In all cases, local enhancement of heat transfer was observed within the bend. The extent of bend-induced enhancement is related to Reynolds numbers and property variations of fluid. Up to 25 % increase in the enhancement was observed in the case of dramatic property changes when compared to case with little property change. The bend-affecting upstream length is within 5.75d, and the bend effect diminishes at 11.5d downstream of the bend and further. Moreover, it was shown that a few existing correlations perform reasonably well in the straight sections, but not in the bending section. A new correlation was developed by introducing an enhancement factor to account for the bend-induced centrifugal effect. The newly proposed equation correlates 85 % of the experimental data with an absolute error less than 10 %.

Void Fraction of Air-Water Two-Phase Flows in a Vertically Placed Horizontal U-Bend

Experiments on air-water two-phase flows in a horizontal U-bend placed in the vertical plane were carried out to investigate effects of pipe bending on the void fraction. The inner diameter and the bend radius of curvature were 8 and 24.3 mm, respectively, so that the dimensionless bend diameter was 6. The flow patterns dealt with were plug, slug and annular flows. The void fractions in the bend and the straight section were measured by using quick-closing valves and the void fraction distribution was evaluated with an image processing method. The applicability of available correlations for the void fraction in the straight pipe was also discussed. For the straight pipe, the void fractions of the plug and slug flows can be accurately evaluated using the Smith correlation, whereas in the annular flow regime the Cioncolini and Thome correlation and the Mauro et al. liquid film thickness model give better agreement with the data. The bend void fractions in the downward and upward flows agree well with those for the pipe diameter of 26 mm given in literature, implying that the diameter effect on the void fraction is weak. The Usui et al. void fraction correlation gives reasonable evaluation for downward flows.

Wetting, infiltration, and interaction behavior of calcium-magnesium-alumino-silicate towards Gd/Yb-modified SrZrO3 coatings deposited by solution precursor plasma spray

Wetting of thermal barrier coatings (TBCs) with calcium-magnesium- alumino-silicate (CMAS) leads to sintering and phase transition, which are major issues in the aerospace industry. We prepared Sr(Zr1−2xYbxGdx)O3−x (x = 0, 0.05, 0.1, and 0.15) coatings using solution precursor plasma spraying with inter-pass boundaries (IPBs) and vertical cracks, and analyzed the CMAS wettability at 1350 °C using the sessile-drop method. The wetting and diffusion dynamics of the CMAS melt on the surface of the coating were studied using a CCD camera, revealing that the Sr(Zr0.7Yb0.15Gd0.15)O2.85 coating had the lowest spreading speed (2.60 × 10−4 mm/s, spreading balance process). Furthermore, a greater extent of crack bending and smaller crack diameter can prevent the coatings from penetration of the CMAS melt.

Investigation on highly flexible CZTS solar cells using transparent conductive ZnO/Cu/ZnO films

Transparent conductivity oxide (TCO) films played an essential part in flexible CZTS solar cells (CSCs), which required excellent transparent conductivity and flexibility of TCO films. The inferior flexibility of ITO films, a commonly used material in TCO films, limited the development of flexible CSCs. In this paper, the ZnO/Cu/ZnO (ZCZ) TCO film with high transmittance and flexibility was prepared by radio frequency magnetron sputtering and applied as a transparent conductive layer for flexible CSCs to improve the flexibility of CSCs. The CSCs with ZnO/Cu(9 nm)/ZnO (ZC9Z) film exhibited a power conversion efficiency (PCE) of 6.01% without bending, higher than that of CSCs with ITO film. The PCE ratio of CSCs with ZC9Z film to that of CSCs with ITO film was 5.83 and 9.09 after a bending diameter of 8 mm and 1000 cyclic bending, showing that CSCs with ZC9Z film were of excellent flexibility.

Hybrid structure of u bent optical fiber local surface plasmon resonance sensor based on graphene

&lt;p&gt;In this paper, a fiber optic sensor was designed and implemented to detect the change in refractive index of sodium chloride salt solution based on the local surface plasmon resonance (LSPR) phenomenon. This sensor was manufactured using a plastic optical fiber (POF), this optical fiber was bent in a U-shape with 0.5cm bending diameter, and then the cladding and part from core of the fiber were removed by polishing at the sensor head to become as a D-shape in cross section. The sensor was coated with 30 nm thickness of gold nano particles (GNPs) by DC plasms coating technology and it was tested with sodium chloride solution, the detection sensitivity was 466.66 nm/RIU. To enhancement the sensitivity, the latest sensor was coated with 20nm thickness of graphene nano material and retested with same samples of sodium chloride solutions. It was found that graphene improved the sensitivity by an excellent amount, where shift in wavelength was 20nm and highest sensitivity obtained was 666.666 nm/RIU.&lt;/p&gt;

Non-isocyanate Polyurethane Coating with High Hardness, Superior Flexibility, and Strong Substrate Adhesion.

Flexible hard coatings with strong adhesion are critical requirements for several foldable devices and marine applications; however, only a few such coatings have been reported. Herein, we report a non-isocyanate polyurethane (NIPU) coating prepared by the epoxy-oligosiloxane nanocluster-amine curing reaction and cyclic carbonate-amine polyaddition, where the former provides the coating with ceramic-like hardness and polymer-like flexibility while the latter polymerization results in NIPU with strong substrate adhesion. The coating is transparent (>92% transmittance), hard (5-7 H), and flexible (2 mm bending diameter). It has strong adhesion to various substrates including aluminum alloy, titanium, steel, glass, ceramic, epoxy, and polyethylene terephthalate (2-8 MPa), which can be attributed to the high density of polar groups in NIPU. Moreover, we can facilely endow the coating with anti-icing, self-cleaning, and anti-smudge capabilities by incorporating amine-terminated low-surface-tension polydimethylsiloxane (PDMS) to replace a part of the amine curing agent. Particularly, the mechanical properties of NIPU coatings are only slightly affected by the introduction of low-content PDMS since it intends to enrich on the surface. The novel coating has promising future for use in fields of foldable devices and marine applications.

Highly sensitive measurement of finger joint angle based on a double-U tapered POF embedded in PDMS film

Finger joint angle measurements are important for the fields such as treatment of joint diseases, health monitoring, wearable devices, etc. As an effective detecting device, the joint angle monitoring sensor should have wide measurement angle range, and high sensitivity. In addition, the sensor should have good skin affinity, so as to enhance the degree of comfort for the user. In this paper, high-sensitivity bending angle sensing based on tapered plastic optical fiber (POF) configuration is proposed. The sensing performance is enhanced by tapering the POF and bending the POF taper to form a double U-shaped configuration then encapsulated with Polydimethylsiloxane (PDMS) film, therefore, the POF taper will be bent at three positions simultaneously, so that the bend induced loss will increase. The experimental preparation process of tapered POF and PDMS film package are presented in detail. The influence of taper waist diameter, and bending diameter on the bending loss has been investigated and optimized to enhance the angle sensitivity of the double U-shaped configuration. The results show that the sensitivity can reach 0.070 dB/° with a linearity of 0.995 in a wide bending angle range of 0-105°. The POF sensor is then applied for the joint bending detection. The experimental results show that the sensor can quickly respond to small pressures, and the variation of bending angles can be distinguished in the detection of joint bending. The proposed POF bending sensor shows the advantages of wide measurement angle range, high sensitivity, low cost and good portability, and shows important potential applications in the fields such as human joint movement detection.

Temperature insensitive salinity sensor with U-shaped structure based on few-mode fiber

A novel U-shaped few-mode fiber (FMF) salinity sensor is proposed, which is insensitive to temperature. It consists of a section of FMF fused between two sections of single-mode fiber (SMF). The flame heating method is used to form the FMF into a U-shaped optical fiber sensor. Because the bending makes the light energy of the core leak into the cladding, higher-order cladding modes are excited and the sensor becomes more sensitive to the external environment. In the experiments, the sensors with different bending diameters are fabricated and studied for salinity and temperature. The results demonstrate that the sensitivity reaches up to 1.847 nm/% in the salinity range of 0 % to 10 %. In the temperature range of 5 °C to 30 °C, it shows temperature insensitive characteristics. Compared with the traditional optical fiber sensor, the sensor can avoid the effect of temperature on measurement results, and can be easily fabricated. It has a good application prospect in the field of seawater temperature and salinity measurement.

Design and Analysis of flexible patch antenna on transparent PVC material substrate

Flexible substrates play a vital role in the design of wearable antennas. Analysis and fabrication of rectangular microstrip patch antenna have been demonstrated in this paper on a least explored flexible PVC-based transparent sheet. The substrate’s dielectric constant and loss tangent have been calculated by conducting a standard ring resonator test. The effect of bending on an antenna with different bending diameters along the x-axis and y-axis has been observed on Vector Network Analyzer (VNA) to verify the flexibility of substrate material for wearable applications.