Minimum Bending Radius Research Articles

Modeling and Analysis of Inter-Panel Slipping for the Design of Rolled Gossamer Arrays

Abstract Many deployable satellite systems benefit from having low mass and high surface area, which has led to the proliferation of gossamer structures in space-based applications. Gossamer structures are characterized by lightweight, low-stiffness membranes, which can flex and roll to compactly stow. An effect of rolling a gossamer structure is that there is a tangential separation along adjacent panels as they roll, resulting in relative motion between panels. To aid designers in predicting and accommodating this motion, a method for modeling the slippage between adjacent panels that occurs while rolling is presented. This analytical slippage model and algorithm is a function of (1) the number of panels, (2) the thickness of each panel, (3) the length of each panel, and (4) the minimum bend radius of the material. It is shown that the thickness and length have a positive correlation with increased slippage, whereas the number of panels and minimum bend radius have a negative correlation with increased slippage. This model allows designers to predict both the magnitude of slippage that occurs where panels meet, as well as the relative range of slippage that occurs within the whole pattern. With these predictions, an appropriate strategy can be selected for accommodating this motion.

Evaluation of the effect of forming strategy in newly introduced flexible roll forming process

In recent years, with the emergence of Industry 4.0 trends and the impact of the COVID-19 pandemic, the agile manufacturing paradigm has gained increasing significance. Substantial efforts have been directed towards introducing new methods, driven by the dual objectives of flexibility and agility. This paper presents an innovative machine that employs two rollers to apply localized deformation to sheet metal through repetitive movement along the length of the sheet. As with all incremental forming processes, the forming strategy is a critical parameter influencing both the forming force and the dimensional accuracy of the manufactured workpiece. In this research, two different forming strategies, internal and external, were implemented for manufacturing elongated 90 deg bends on 1 mm and 3 mm thick AISI 304 sheets. Both numerical and experimental analyses were performed to assess the effects of these different strategies. The results confirm that the forming force with the external strategy is 50 % and 47 % less for the 1 mm and 3 mm sheets, respectively. Moreover, the external forming strategy allows for better control of the obtained angle, but limits the minimum obtainable bending radius.

External Steering of Vine Robots via Magnetic Actuation.

This article explores the concept of external magnetic control for vine robots to enable their high curvature steering and navigation for use in endoluminal applications. Vine robots, inspired by natural growth and locomotion strategies, present unique shape adaptation capabilities that allow passive deformation around obstacles. However, without additional steering mechanisms, they lack the ability to actively select the desired direction of growth. The principles of magnetically steered growing robots are discussed, and experimental results showcase the effectiveness of the proposed magnetic actuation approach. We present a 25-mm-diameter vine robot with an integrated magnetic tip capsule, including 6 degrees of freedom (DOF) localization system and camera, and demonstrate a minimum bending radius of 3.85 cm with an internal pressure of 30 kPa. Furthermore, we evaluate the robot's ability to form tight curvature through complex navigation tasks, with magnetic actuation allowing for extended free-space navigation without buckling. The suspension of the magnetic tip was also validated using the 6 DOF localization system to ensure that the shear-free nature of vine robots was preserved. Additionally, by exploiting the magnetic wrench at the tip, we showcase preliminary results of vine retraction. The findings contribute to the development of controllable vine robots for endoluminal applications, providing high tip force and shear-free navigation.

Effect of texture on bending behavior of Mg alloy sheets

The effect of Li elements on the microstructure and texture evolution of AZ31 alloy sheets during room-temperature three-point bending was investigated. The results showed that the conventional c-axis//ND basal texture of the extruded AZ31 sheet could be modified to a TD-elongated fiber texture with a 5 wt% Li addition. As a result, the room-temperature bendability of the Mg–3Al–5Li sheet was improved effectively, and this sheet showed a minimum bending radius of only 2 mm. The superior bendability exhibited surpasses the room-temperature bending capabilities commonly observed in the majority of commercial Mg alloys. The improvement in bendability of the Mg–3Al–5Li sheet was attributed to the TD-elongated texture distribution. This type of texture distribution may offer more effective deformation modes to alleviate thickness strain during bending in comparison to the texture in extruded AZ31 sheets. This study could provide insights into developing Mg alloys with high room-temperature bendability by tailoring texture distribution rather than texture weakening.

Failure Analysis of a Suspended Inter-Array Power Cable between Two Spar-Type Floating Wind Turbines: Evaluating the Influence of Buoy Element Failure on the Cable

The suspended configuration of inter-array power cables between floating offshore wind turbines necessitates using various ancillary equipment, such as buoy elements and bend stiffeners, to maintain the desired cable geometry. The failure analysis is an important step in the design of an inter-array dynamic power cable layout. This study investigates the impact of buoy element failures on the structural integrity and fatigue life of inter-array power cable configurations in offshore environments, focusing on four environmental conditions representative of the North Sea. Utilizing numerical simulations and fatigue analysis in OrcaFlex, static and dynamic analyses are conducted to assess maximum tension, minimum bend radius (MBR), and fatigue life under single and two failure scenarios of buoy elements. The results indicate that single buoy failures significantly increase maximum tension at hang-off points. At the same time, MBR is found to be the smallest at the failure position, aiding in failure point identification. In addition, for the two buoy element failure scenarios, the maximum tension increase poses risks to structural integrity, while MBR and fatigue life have high sensitivity to the applied environmental conditions.

A Novel Polynomial-Time Algorithm for Automatic Layout of Branching Cables in a Fixed Topology

Designing the layout for complex electromechanical products involves the challenging task of automatically laying out cables. This challenge is particularly pronounced in the case of branch cables, which are more intricate due to their multiple connection terminals and branches. This paper presents a polynomial-time wiring algorithm based on dynamic programming to determine branching point locations in the layout design of cables, given the electrical definition of the wire harness. The method considers various engineering constraints, including obstacle avoidance, wall adherence, minimum bend radius, and gray areas. To validate our method, we implemented a branch cable auto-layout system through secondary development based on the UG platform. The experimental results indicate the effectiveness of our approach, demonstrating promising performance in terms of time and high-quality layouts. This showcases its potential for practical application in cable layout design for complex electromechanical systems.

Reference dynamic power cable of floating offshore wind turbine for thermal and simple fatigue evaluation

With the increased interest in floating offshore wind turbines, there is an increased focus on evaluating the lifetime of the auxiliary systems, such as the mooring lines and the dynamic power cables, because these systems are in-mature compared to bottom-mounted offshore wind farms. This paper proposes a conceptual reference dynamic power cable suitable for the 15 MW NREL reference turbine mounted on the UMaine floater installed at 82 m water depth. This provides a basis for discussing the life evaluation of dynamic cables obtained from aeroelastic simulation of the floating offshore wind turbine platform exposed to the environmental conditions of the South Brittany site in France. An electromagnetic-thermal finite element simulation is used to determine the current capacity of the cable and aeroelastic simulations are used for a simple assessment of the main failure modes as maximum cable tension, minimum bending radius and fatigue damage accumulation.

Analysis of load carrying performance for glass fiber reinforced thermoplastic composite pipe under different in-service conditions

Fiber reinforced thermoplastic composite pipe (FRTP) has advantages over traditional metallic counterparts for oil and gas transportation. During in-service the pipe is subjected to different mechanical loads including internal pressure, torsion, and bending. In this work, a special type of continuous glass fiber reinforced thermoplastic composite pipe (DN150-6.4 MPa) is analyzed by finite element method (FEM) under various complex service-in conditions. Stress and strain are investigated for different layers of FRTP to determine the extreme load capacity. Experimental analysis is conducted to validate proposed method. Combining the results from FEM and test, it is concluded that the ultimate internal pressure (burst pressure) of FRTP is 61.7 MPa, the ultimate axial tensile displacement is 66.4 mm, the maximum torsion angle is 71.5°, and the minimum bending radius 978.9 mm. Under different working conditions, the mechanical properties of the FRTP are still surplus under the given load. For the good agreement with experimental data, the FEM modeling can be guide for practical application of FRTP.

Incident during construction of an underwater passage by directional drilling

Relevance. This paper considers the issue of construction of underwater passages of trunk pipelines by the directional drilling method using concrete weight coated pipes. This issue is relevant, since at the present moment there is no standards and technical documentation regulating the calculation procedure of the minimum allowable elastic bend radius of a pipeline with concrete coating in a well. There are situations when design institutes made incorrect design decisions as a result, the pipe string got stuck during works. Those incidents led to unnecessary economic expenditures and a delay in the work implementation plan. Aim. To study the issues which related with the sticking of the pipe string during the construction of the underwater passage of the main pipeline by the method of directional drilling; calculate the minimum allowable elastic bend radius of a pipeline with concrete coating and the actual parameters of the pilot drillhole. Objects. An underwater passage of a trunk pipeline constructed by the method of directional drilling. Methods. Study of standards and technical documents on the construction of underwater crossings of main pipelines and an analysis of the incident in which a pipeline with concrete weight coating got stuck. Results. The authors substantiate the calculation of the minimum allowable elastic bend radius of a pipeline with a concrete coating based on the requirements of domestic standards and technical documentation. The authors have calculated this value by an analytical method, based on studies of the bending stiffness of concrete structures by foreign scientists, as well as actual parameters of the pilot drillhole. The obtained results of the studied values were analyzed and a conclusion was given about the causes of the incident associated with the sticking of the pipe string.

Preparation of C/Si3N4 flexible conductive composite films by coating method

Carbon-based materials are widely used in electrical heaters, resistors, battery electrodes, and other applications. Membranous electronic components, with light weight, small volume, extraordinary mechanical flexibility, can be used in microelectronic devices and flexible electronic devices. The C/Si3N4 composite film was prepared by circulating 16% sucrose solution on the coating machine for 4 times and heat treating with nitrogen at 850 °C for 60min. The composite film has excellent electrical conductivity, and the resistivity is 15 mΩ cm at normal temperature (20 °C), and the minimum resistivity can be less than 1 mΩ cm at high temperature. In addition, the composite film maintains the inherent flexibility of silicon nitride fiber paper, and the minimum bending radius is as low as 3 mm. Compared with polymer flexible membranes, C/Si3N4 composite membranes show excellent long-term stability at high temperatures, and the preparation process is green, low cost, easy to operate, and suitable for large-scale production.

ВСТАНОВЛЕННЯ ВПЛИВУ ПАРАМЕТРІВ ПРЕСУВАННЯ НА ПРОЦЕС ГНУТТЯ БУКОВИХ МЕБЛЕВИХ ЗАГОТОВОК

It is substantiated that the technology of cold bending of pre-pressed blanks has a perspective. It was established that the minimum bending radius depends on the direction of pressing and the degree of pressing. It was determined that pressing in the radial and tangential directions does not give the desired effect during bending, which is evidenced by a large number of defects (respectively 47-67% and 34-61%) associated with the specific structure of the wood. In particular, during pressing, the wood cells are deformed along the pressing line, and during subsequent bending, the elongation of the wood in the peripheral part passes across the pressing line and is only partially compensated by the pressed cell walls. It was experimentally established that the results are significantly different when the workpieces are axially pressed. When the degree of pressing is increased from 15 to 25%, the number of high-quality blanks increases and amounts to 83-97%, respectively. This can be explained by the fact that during axial pressing, wood cells are deformed along the line of pressing. During subsequent bending, the elongation of the wood in the peripheral part also takes place along the line of pressing and is compensated to a much greater extent by the pressed cell walls. It was found that when the workpieces are pressed along the axis, uneven pressing along the length occurs, that is, only approximately half of the length of the workpiece is pressed. This is probably the main reason for the defect. Additional research and possibly new technological solutions are needed to solve the problem of uneven pressing during axial pressing. Prospective directions of research into bending processes of beech furniture blanks have been formed, in particular from the development of new bending technologies; optimization of pressing parameters; modeling of bending processes; study of the influence of humidity and temperature; study of the strength and durability of bent blanks.

Optimization of bend stiffeners of a suspended inter-array power cable between two floating offshore wind turbines

The concept of a suspended inter-array power cable assumes that the cable floats within the water column instead of being laid on the seabed. This setup requires additional equipment, such as buoyancy modules or buoys, to achieve the desired cable configuration. The implementation of buoyancy modules introduces abrupt changes in stiffness between the cable sections with clamped-on buoyancy modules and bare cable sections. Large stiffness variations can negatively impact cable bending, causing excessive curvature and fatigue damage. In order to form a smooth transition in stiffness between the buoyancy sections and the bare cable, bend stiffeners can be equipped. The study aims to optimize the bend stiffener design for a representative suspended power cable between two floating offshore wind turbines (FOWTs). The inter-array power cable system is simulated in OrcaFlex. Two parameters, including the outer diameter and the length of the bend stiffener, are adjusted to generate different cases. Eight environmental conditions are applied to the dynamic analysis of the cases. The fitness factor approach is used as a criterion to assess the overall performance of different bend stiffener designs. Adjusting the outer diameter of bend stiffeners clearly influences the maximum effective tension and the minimum bending radius by changing the stiffness profile of the bend stiffener and its submerged weight. In the investigated range of parameters, increasing the overall length of bend stiffeners is found to be less effective than adjusting the outer diameter of the bend stiffener.

Diamine-modified bismaleimide for toughening of UV-cured epoxy acrylate coating

With the rapid development of the electronics industry, higher requirements are being placed on the quality and reliability of flexible copper clad laminate (FCCL). To protect FCCL, there have been studies on using UV curable coatings for surface protection. However, traditional UV curable coatings based on epoxy acrylate (EA) resins tend to be rigid, and although methods for toughening them exist, they often compromise their heat resistance. Therefore, there is ongoing research on how to improve the toughness of UV-curable coatings while maintaining the heat resistance of the EA resin. In this study, a high-heat-resistant bismaleimide (BMI) with excellent properties was used as a toughener by modifying it with 4,4′-Oxydianiline (ODA) and polyetheramine (PEA). The modified BMI was then introduced into the EA resin to prepare a UV-curable protective coating with high heat resistance, toughness, and good insulation and dielectric properties. The research results showed that after the addition of modified BMI, the heat stability was not reduced and even showed improvement, and under conditions of nearly unchanged hardness, the best adhesion was rated as 5B, with a minimum bending radius of 1 mm. At an ODA:PEA ratio of 3:7, the coating attains a maximum tensile strength of 36.84 MPa, showcasing a notable 76.65 % enhancement in elongation at break when contrasted with coatings composed solely of pure EA. When the ratio of ODA to PEA was 4:6, the coating exhibited a minimum dielectric constant of 3.05, a breakdown field strength of up to 77.37 kV/mm, and a volume resistivity of 3.52 × 1014 Ω m, indicating excellent dielectric and insulation performance. This study provides a novel method for the preparation of UV curable coatings with outstanding performance, offering new insights and directions for future research on UV curable coatings for FCCL. Moreover, the research results have important implications for industrial applications.

Global formability and bendability of ultra-high strength steels: Effect of mechanical properties on the strain distribution and behaviour in air-bending

Bendability is a key property for ultra-high strength steels, that affects their usability in many industrial applications. Previous research and efforts on improving the bendability of high-strength steels have focused mostly on the minimum bend radius. However, as the minimum bend radius has been deemed insufficient as a measure of bendability, a new approach may be necessary for further advancements in bendability research. In this paper, bendability of nine materials is investigated from a global formability perspective, through bending tests and tensile tests. Digital image correlation is used for strain measurement in both the bending and tensile tests. Linear regression is used for determining the relationships between the obtained tensile test results and bending strain distributions. The findings of this paper show that applying a “local/global formability” approach to bendability could be beneficial for future research, as better description of the bending behaviour can be obtained and the factors affecting certain bending behaviours can be thoroughly investigated.

Room-temperature fabrication of flexible oxide TFTs by co-sputtering of IGZO and ITO

Amorphous oxide semiconductors, especially indium gallium zinc oxide (IGZO), have been widely studied and obtained significant progress in flexible thin-film transistors (TFTs) due to the high carrier mobility and low deposition temperature. However, a further annealing step is generally required to activate electrical properties and improve the device performance, which limited their applications in flexible electronics. In this study, we achieved flexible TFTs and arrays using co-sputtered IGZO and indium tin oxide (ITO) as channels deposited at room temperature without post-annealing. It was found that better transistor switching properties could be effectively achieved by regulating the sputtering power of ITO in the co-sputtered deposition. The device performance is comparable to that of the conventional oxide TFTs with high annealing temperatures (⩾300 °C), exhibiting a high saturation mobility (μ sat) of 15.3 cm2 V−1s−1, a small subthreshold swing (SS) of 0.21 V dec−1, and a very high on–off ratio (I on/off) of 1011. In addition, a 12 × 12 flexible TFT array was achieved with uniform performance owing to the low-temperature processing advantage of this technique. The flexible TFTs exhibited robust mechanical flexibility with a minimum bending radius of 5 mm and bending cycles up to 1000. Furthermore, an inverter based on co-sputtered IGZO and ITO was demonstrated with the maximum gain of 22. All these achievements based on the proposed TFTs without post-annealing process are expected to promote the applications in advanced flexible displays and large-area integrated circuits.

Multiple designs with broad applicability for enhancing birefringence in low-loss terahertz HC-ARF

The use of hollow-core anti-resonant fiber (HC-ARF) as a transmission medium for the terahertz (THz) frequency range is attracting increasing attention from researchers. This paper introduces a low-loss, high birefringence anti-resonant fiber. The proposed structure achieves a maximum birefringence of 2.72 × 10−3 around 1 THz and maintains a birefringence above the 10−3 level over a wide frequency band (0.7∼1.12 THz). It has a minimum loss of 0.2 dB/m and a minimum bend radius of 0.3 m, and the paper validates that this structure has good manufacturing error tolerance. Furthermore, three methods for introducing high birefringence into low-loss ARFs are proposed and three structures are selected for verification. These findings contribute to the development of more efficient and reliable THz transmission systems.

Design of single-mode single-circularly polarized chiral anti-resonant fiber for the communication band

We propose a design of anti-resonant fiber (ARF) involving the introduction of chiral material into the inner regions of six germanium-doped silica glass cladding tubes, which can support the operation of single-mode single left-handed circular polarization in the communication band from 1.540 to 1.605 µm. In particular, the loss reaches a minimum value of 0.009 dB m−1 at 1.550 µm. The sign of the chiral parameter can control the handedness of polarization in the operation of single-mode single-circular polarization. In addition, the ARF possesses a good bending resistance performance. The minimum bending radius of the ARF is 10 to maintain the single-mode single left-handed circular polarization for 1.550 µm. We believe the novel ARF can find applications in optical communication, polarization imaging and chiral sensing.

Fusion splicing of plastic optical fibers using a mid-IR fiber laser

This work demonstrated the fusion splicing of plastic optical fibers (POFs) using a 2.8 μm continuous-wave fiber laser. This mid-IR laser-based fusion splicing technique does not require the use of adhesives or any other treatments. The performance of the proposed method was investigated by assessing the optical transmission, tensile strength and bending strength values of POF specimens after fusion bonding while employing various splicing conditions. An optical transmission of 0.76 was obtained by splicing under appropriate conditions. A minimum bending radius and tensile strength of the POF samples were found to be 1.5 mm and 13.5 N, respectively.

Weak optical modes for high-density and low-loss photonic circuits

Dielectric optical waveguides constitute the main building blocks of photonic integrated circuits (PICs). Channels with high refractive index contrast can provide very compact PIC components, whereas structures with lower index exhibit less propagation loss. A hybrid concept that can combine the best of high- and low-index materials is highly required. Here, we devise a new approach to realize compact and low-loss hybrid optical waveguides based on the interaction of weak optical modes. This is a rather universal approach that can be applied to a wide range of optical materials. To prove the principle, the hybrid waveguide structure is formed by combining a low-index polymer and a thin layer of silicon nitride. For this material combination, a minimum bending radius of 90 µm (for a bending loss of 0.005 dB/90°) and a propagation loss of 0.7 dB/cm are achieved. The viability of this platform is demonstrated through a series of high-performance novel PIC components. This hybrid waveguide platform enabled by a powerful and simple design concept holds great promise for high-density and low-loss PICs.

Effect of Li addition on bending behavior of extruded Mg–2Zn alloy sheet

The effect of Li element on microstructure and texture evolutions of Mg–2Zn alloy sheet during three-point bending at room temperature were investigated. The results showed that the conventional c-axis//ND basal texture of the extruded Mg–2Zn sheet could be modified to a TD-elongated fiber texture with 3 wt.% Li addition. As a result, the room-temperature bendability of the Mg–2Zn–3Li sheet was improved effectively and this sheet showed a minimum bending radius of only 1.75 mm. Such an excellent bendability exceeds the room-temperature bending capacity of most commercial magnesium alloys. The improvement in bendability of the Mg–2Zn–3Li sheet was attributed to the TD-elongated texture distribution. This type of texture distribution could provide more efficient deformation modes to release the thickness strain during bending compared to the extruded Mg–2Zn sheet. This study could provide insights into developing Mg alloys with high room-temperature bendability by tailoring texture distribution rather than texture weakening.