Small Bending Research Articles

ҚАТТЫ ЦЕНТРІ БАР ДӨҢГЕЛЕК ОСЬТІК СИММЕТРИЯЛЫҚ МЕМБРАНАНЫҢ ФИЗИКАЛЫҚ ЖӘНЕ ГЕОМЕТРИЯЛЫҚ ПАРАМЕТРЛЕРІН ОҢТАЙЛАНДЫРУ

The mathematical model of an isotropic circular plate-membrane with a non-deformable fixed central disk loaded by a uniformly distributed static load is considered in a linear formulation. On this basis, the extreme problem of determining the rational physical and geometrical characteristics of an elastic element from the condition of the maximum of the target function of the thrust (permutation) force with two coupling equations in the form of the classical Huber-Genke-Mises strength hypothesis and a geometrical relation limiting the membrane thickness in accordance with the known fundamental Kirchhoff assumptions of the technical theory of small plate bending is solved. To illustrate the proposed algorithm and calculation procedure, a numerical example of the selection of optimum parameters of a manganese steel diaphragm with given dimensions of thickness and outer radius is presented. The results of the work can be used in the process of designing high-precision membrane-type pressure gauges, widely used in mechanical engineering, aviation, instrumentation, and construction in the design of pressure tanks with controlled excess pressure of gas or liquid.

Optimization of Ti-3Al-2.5V titanium tubes by differential heating push-bending based on a modified Johnson−Cook constitutive model

This study addresses the challenges associated with the difficult formation and low quality of formed Ti-3Al-2.5 V titanium alloy thin-walled tubes with small bending radii (r / D < 1.5, where r is the bending radius, D is the outer diameter of the tube) by proposing a differential heating push-bending (DHP-B) forming approach. Initially, the stress−strain curves of Ti-3Al-2.5 V at various strain rates and temperatures were obtained through high-temperature uniaxial tensile tests. Subsequently, a modified Johnson−Cook (JC) model for Ti-3Al-2.5 V within the temperature range of 25℃ to 800℃ was developed to enhance the accuracy of the finite element model. Based on the static implicit and dynamic explicit algorithms, a thermomechanically coupled finite element model for differential heating push-bending of titanium alloy thin-walled tubes has been established. Taking the heating temperature, friction coefficient, counterthrust force and rubber block thickness as the optimization parameters, the prediction model of the maximum wall thinning rate and thickening rate is obtained by using the response surface method, and the best parameter combination is obtained via the NSGA-II algorithm and the minimum distance selection method, which realizes the optimization of differential heating push-bending parameters, as verified by experiments in which the maximum wall-thinning rate is reduced to 9 %, and the maximum wall thickness thickening rate is reduced to 14.2 %, which improves the forming quality of the titanium tube.

Heavy electron doping in monolayer MoS2 on a freestanding N-face GaN substrate

Abstract This study explores how gallium nitride (GaN) surface polarity affects the optical properties and surface potential of MoS2. Using Raman spectroscopy, photoluminescence, and Kelvin force microscopy (KFM), significant electron doping (~1014 cm-2) was observed in MoS2 on N-face GaN compared to Ga-face. PL spectra and the small contact potential difference of ~30 mV measured by KFM provided evidence for polarity-dependent different doping levels. Additionally, KFM measurements also suggested a small band bending difference between Ga- and N-face GaN, likely due to interactions at the GaN/MoS2 interface. This heavy doping contributes to the improved valley polarization of N-face GaN.

High‐Performance Flexible Silicon Nanowire Field Effect Transistors on Plastic Substrates

AbstractInorganic semiconductor nanowires, known for their exceptional electronic properties and mechanical flexibility, are widely regarded as the ideal 1D channel materials for creating high‐performance flexible electronics. In this work, the integration of ordered arrays of silicon nanowire (SiNW) field effect transistors (FETs) directly onto flexible plastic substrates is showcased. The self‐aligned crystalline SiNW multi‐channels are first grown through an in‐plane solid–liquid–solid mechanism on rigid substrates, and then efficiently transferred in‐batch onto flexible polyethylene terephthalate (PET) plastics. The FETs constructed on these transferred SiNW channels exhibit outstanding performance, with a high on/off current ratio of &gt;105, a low subthreshold swing of 175 mV dec−1, and remarkable mechanical stability that can endure an extremely small bending radius of 0.5 mm for 1000 cycles. Furthermore, inverter logics are also successfully demonstrated on plastic substrates, highlighting a prominent routine for scalable integration of high‐quality SiNW channels in the development of low‐cost, high‐performance flexible displays and wearable electronics.

Living hinges for resilient and recyclable paper-based flexible printed electronics

Abstract The ability to fabricate electronics by printing has enabled an array of technologies that can create intelligent or smart packaging; however, this can come at the cost of recyclability. Selection of materials compatible with recycling streams is possible, such as paperboard and carbon inks, but there is a trade-off in terms of performance, flexibility and reliability. A major challenge for the use of paperboard is delamination and deformation when subject to small bend radii. The substrate has a tendency to crease when bent beyond a critical radius, which can fracture the surface and any traces printed onto it, causing device failure. We have demonstrated that the use of kerf cuts to form a living hinge, similar to that used in woodworking, can increase the flexibility of paperboard and allow reliable bending of conductive traces. We have identified the key design parameters of such a living hinge and evaluated their effect on the flexibility of a typical paperboard used in packaging. We then demonstrated that conductive traces of silver or carbon can withstand repeated bending with 100% reliability, compared to a worst case of 16% of control sample traces surviving the same test. Additionally, we demonstrated that the hinges improve the consistency of the trace resistance when subject to repeat bending. The behaviour of the resistance change as a function of bending was seen to be dependent upon the ink material, likely due to differing morphologies. We demonstrate the applicability of this technique in a smart device for medication adherence packaging.

Failure analysis of erosion wear of the pipeline after 30° elbow by adsorbent particles

An adsorbent transport pipeline after a 30° elbow experienced premature perforation and leakage during service. The failure analysis was performed by means of morphology observation, damaged surface analysis and computational fluid dynamics (CFD) simulation. The results revealed that thickness thinning occurred only on the upper wall, and the severely thinned region exhibited a special striated groove morphology. The main cause of pipeline failure was attributed to erosive wear caused by adsorbent impacts on the wall. Due to the particle redistribution process under the action of multiple force fields in the small bending angle elbow, the straight pipeline after the elbow had a very complex inlet boundary condition, so that the particle concentration at the upper wall was substantially increased. Besides, the sliding motion of the particles on the wall surface was greatly intensified. Cutting deformation became the main form of erosion damage, which induced an alteration in the erosional morphology of the failed pipeline and the backwardness of the leakage site.

Performance evaluation of surface treatment waste glass as aggregate in asphalt mixture

Surface modification is a crucial strategy for enhancing the pavement performance of waste glass hot mix asphalt (HMA) mixtures. This study conducts a comparative analysis of various surface modification techniques to pinpoint the key factors that influence the interfacial interaction between waste glass and asphalt. To assess the performance of asphalt mixtures containing surface-treated waste glass, the study employed methods such as Energy Dispersive X-ray Spectroscopy (EDS), boiling water tests, and contact angle measurements, which helped to quantify surface morphology and the effectiveness of different treatments. The evaluation also included assessments of water stability, dynamic stability, small beam bending, and anti-skid properties. Findings revealed that applying a silane coupling agent to the waste glass significantly enhanced adhesion with asphalt, resulting in markedly improved pavement performance. The study identified that incorporating surface-treated waste glass at an optimal proportion of 6 % within the asphalt mixture led to a 42.3 % increase in dynamic stability and a 38.6 % enhancement in anti-skid performance compared to standard mixtures. This research offers a comprehensive evaluation framework for surface modification techniques of waste glass, underscoring its potential to considerably improve road performance.

Modeling Study of Si3N4 Waveguides on a Sapphire Platform for Photonic Integration Applications.

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III-V materials. In parallel with developing active devices for photonics integration applications, in this work, silicon nitride optical waveguides on a sapphire substrate were analyzed using the commercial software Comsol Multiphysics in a spectral window of 800~2400 nm, covering the operating wavelengths of III-V lasers, which could be monolithically or hybridly integrated on the same substrate. A high confinement factor of ~90% near the single-mode limit was obtained, and a low bending loss of ~0.01 dB was effectively achieved with the bending radius reaching 90 μm, 70 μm, and 40 μm for wavelengths of 2000 nm, 1550 nm, and 850 nm, respectively. Furthermore, the use of a pedestal structure or a SiO2 bottom cladding layer has shown potential to further reduce bending losses. The introduction of a SiO2 bottom cladding layer effectively eliminates the influence of the substrate's larger refractive index, resulting in further improvement in waveguide performance. The platform enables tightly built waveguides and small bending radii with high field confinement and low propagation losses, showcasing silicon nitride waveguides on sapphire as promising passive components for the development of high-performance and cost-effective PICs.

Piezoelectric Gauge of Small Dynamic Bending Strains

Piezoelectric Gauge of Small Dynamic Bending Strains

Application of advances in the development and production of optical fiber in the development and design of fiber optic devices.

The dimensions of devices based on optical fiber are limited by the sensitivity of the optical fiber to macrobending, which leads to an increase in optical losses at small bending radii. New types of fibers with low macrobending losses make it possible to significantly tighten the dimensions. However, there may be a risk of fiber failure at bending points during the life of the product due to mechanical fatigue. In the article, based on the use of a static fatigue model of silica glass, a simple expression is obtained to estimate the probability of fiber failure under long-term bending stress depending on the length of the bent section, bend radius and humidity, taking into account the result of a proof-test carried out by the fiber manufacturer. The possibility of increasing the mechanical reliability of silica fiber by applying a hermetical carbon coating is discussed. The use of the obtained expressions in design makes it possible to reduce the dimensions of fiber optic products without the risk of reducing their reliability.

Integrated 3D printing of reconfigurable soft machines with magnetically actuated crease-assisted pixelated structures

Reconfigurable magnetic soft machines have a wide range of applications in soft robotics, aerospace, medical devices and flexible electronics. However, the high-precision reconfiguration of magnetically actuated soft machines is hindered by the absence of rational structural design and integrated manufacturing techniques. Here, we report an innovative design and manufacturing approach to realize magnetically actuated high-precision reconfigurability. We present a crease-assisted pixelated design using a mixture of magnetic particles and phase-change medium as the pixel points, with an elastomer as the crease to connect the pixel points, simulating origami. The design of elastomer creases improves pixel stiffness without loss of reconfigurable accuracy, thereby significantly improves the magnetic particle concentration in the pixel. An effective multi-material 3D printing technique is used to achieve the integrated printing of the designed structure. The resulting magnetically actuated soft machines exhibit remarkable capabilities, achieving small curvature bending and precise reconfiguration with weaker actuating magnetic fields (100mT). The superior performance of this design has been confirmed through demonstrations of crawling and rolling machines, magnetically controlled switches, and logic circuits. The work enhances the reconfiguration accuracy of magnetically actuated soft machines, increasing their potential for soft robotics and flexible electronics applications.

Design of hollow-core anti-resonant optical fiber based on bragg elements with low-loss and wide bandwidth

A type of anti-resonant hollow-core optical fiber consisting of Bragg elements is proposed. The confinement and bending losses are numerically simulated using the finite element method. It is found that the introduction of concentric rings to form anti-resonant structure can reduce the mode transmission loss by 2 ∼ 4 orders of magnitude compared with the anti-resonant element composed of only one dielectric layer, therefore it can achieve ultra-low loss optical transmission. The influence of the structural parameters on the confinement loss was investigated. Furthermore, it is demonstrated that each dielectric layer independently contributes to the confinement of the core modes. It is also found that the Bragg reflection structure can effectively suppress the coupling between core and cladding modes, and achieve broadband low-loss optical transmission under small bending radius. In particular, it can achieve a low transmission loss of less than 0.1 dB km−1 over a wide wavelength range of 600 nm at the bending radius of 3 cm.

A Quasi-Static Model Accounting for Friction-Induced Hysteresis in Tendon-Actuated Superelastic Notched Tube Instruments

Superelastic notched tube instruments are being increasingly employed in surgical robotics. Due to their superelastic material properties, they can achieve small bending radii even for large bending angles, which makes them very interesting for minimally invasive interventions, typically dealing with confined spaces. Several works have aimed to model the behavior of such tubes in regard to the actuation force. The most extensive considers the superelastic material properties as well as the friction between the instrument and the tendon. However, no model is able to capture both the hysteresis behavior of the superelastic material as well as the hysteresis behavior induced by the friction. This text proposed a quasi-static method for modeling the behavior of nitinol notched tube instruments accounting for both material- and friction-induced hysteresis. The model is validated on four samples and compared to state of the art models. Results show an average notch position root mean square error of 1.06 mm (5.5%) and 0.46 mm (2.4%) for the method with measured parameters and optimized parameters, respectively.

Study of the large bending behavior of CNTs using LDTM and nonlocal elasticity theory

The general expressions for vertical deflection, horizontal displacement, and strain energy in a bent cantilevered carbon nanotube (CNT) are derived herein under a uniformly distributed load. This derivation employs nonlocal elasticity theory, crucial for understanding nanoscale mechanics due to size effects, and accounts for the nonlinear relationship between bending curvature and deflection under large bending conditions, a novel contribution. In the limiting cases, our expressions for large bending give the corresponding expressions reported in the literature for small bending. Additionally, we introduce the Laplace-Differential Transformation Method (LDTM) for the first time, providing efficient solutions to explore the influence of parameters like aspect ratio and small-scale factors on CNT bending behavior. Comparison with the analytical method validates the accuracy and efficacy of LDTM, offering a rapid solution for nonlinear equations. Our findings reveal that strain energy deviates more prominently from quadratic behavior in CNTs with high aspect ratios, while small-scale parameters have a pronounced effect on CNTs with smaller aspect ratios. These results will be relevant to designing and applying the nanoscale-sized cantilevered CNTs used in MEMs/NEMs.

Grain boundaries are not the source of Urbach tails in Cu(In,Ga)Se2 absorbers

The presence of Urbach tails in Cu(In,Ga)Se2 (CIGSe) absorbers has been identified as a limiting factor for the performance of the CIGSe solar cells. The tail states contribute to both radiative and non-radiative recombination processes, ultimately leading to a reduction in the open-circuit voltage and, consequently, decreasing the overall efficiency of CIGSe devices. Urbach tails result from structural and thermal disorders. The Urbach tails can be characterized by the Urbach energy, which is associated with the magnitude of the tail states. Within polycrystalline CIGSe absorbers, grain boundaries can be considered as structural disorder and, therefore, can potentially contribute to the Urbach tails. In fact, it has been proposed that the band bending at grain boundaries contribute significantly to the tail states. This study focuses on examining the correlation between Urbach tails and the band bending at the grain boundaries. The Urbach energies of the CIGSe samples are extracted from photoluminescence (PL) measurements, which reveal that the introduction of Sodium (Na) into the material can lead to a reduction in the Urbach energy, and an even further decrease can be achieved through the RbF post-deposition treatment. The band bending at the grain boundaries is investigated by Kelvin probe force microscopy measurements. A thorough statistical analysis of more than 340 grain boundaries does not show any correlation between Urbach tails and grain boundaries. We measure small band bending values at the grain boundaries, in the range of the thermal energy (26 meV at room temperature). Furthermore, our intensity dependent PL measurements indicate that Urbach tails are, at least in part, a result of electrostatic potential fluctuations. This supports the model that the introduction of alkali elements mainly decreases the magnitude of electrostatic potential fluctuations, resulting in a subsequent reduction in the Urbach energy.

Impacts of mandrel parameters on forming quality of tube bending with small bending radius

Impacts of mandrel parameters on forming quality of tube bending with small bending radius

Process parameters optimization of differential heating push-bending for small bending radius tube based on orthogonal experiments

Process parameters optimization of differential heating push-bending for small bending radius tube based on orthogonal experiments

스프레이 프린팅된 1 V 이하의 유연한 전해질 게이트 인버터

We demonstrate all-printed, low-voltage, and flexible electrolyte-gated transistors and inverters prepared through a facile spray-printing process. All active components of the electronic circuits, including source/drain electrodes, semiconductor, gate dielectric, gate electrode, and load resistor, were directly deposited via spray printing. The sprayed transistors show a high on/off ratio of ∼104. The printed devices also show excellent operational stability under successive bending stresses, maintaining 88% of their performance after 5,000 bending cycles at a small bending radius of 2 mm. Furthermore, the resistor-loaded flexible inverters exhibit appropriate rail-to-rail voltage inverting characteristics with a high voltage gain of ~9 at a low supply voltage of −1 V. These results demonstrate that the high-throughput strategy is promising for generating low-voltage, flexible, and all-spray-printed electronic circuits.

Review of the Development of an Unbonded Flexible Riser: New Material, Types of Layers, and Cross-Sectional Mechanical Properties.

Unbonded flexible risers consist of several helical and cylindrical layers, which can undergo large bending deformation and can be installed in different configurations to adapt to harsh marine environments; thus, they can be applied to transport oil and gas resources from ultra-deep waters (UDW). Due to their special geometric characteristics, they can ensure sufficient axial tensile stiffness while having small bending stiffness, which can undergo large deflection bending deformation. In recent years, the development of unbonded flexible risers has been moving in an intelligent, integrated direction. This paper presents a review of unbonded flexible risers. Firstly, the form and properties of each interlayer of an unbonded flexible riser are introduced, as well as the corresponding performance and configuration characteristics. In recent years, the development of unbonded flexible risers has been evolving, and the development of machine learning on unbonded flexible risers is discussed. Finally, with emphasis on exploring the design characteristics and working principles, three new types of unbonded flexible risers, an integrated production bundle, an unbonded flexible riser with an anti-H2S layer, and an unbonded flexible riser with a composite armor layer, are presented. The research results show that: (1) the analytical methods of cross-sectional properties of unbonded flexible risers are solved based on ideal assumptions, and the computational accuracy needs to be improved. (2) Numerical methods have evolved from equivalent simplified models to models that account for detailed geometric properties. (3) Compared with ordinary steel risers, the unbonded flexible riser is more suitable for deep-sea resource development, and the structure of each layer can be designed according to the requirements of the actual environment.

Bending forming method for tubes with small bending radius based on push-spin integration

Bending forming method for tubes with small bending radius based on push-spin integration