Easy Bending Research Articles

TADs smart easy bending (T.S.E.B.) protocol for impacted canines treatment supported by temporary anchorage devices and aligners

TADs smart easy bending (T.S.E.B.) protocol for impacted canines treatment supported by temporary anchorage devices and aligners

Bending characteristics of a round strand made by stacked HTS tapes

Although the development of REBCO coated conductor has proved its superiority of critical current in high-field background, mechanical issues caused by electromagnetic forces are still big challenges. Large-scale magnets call for robust and high-Je cables for simplicity of the system. To meet the requirements, here we report a round cable comprised of a stack of 2 mm wide high-temperature superconducting (HTS) tapes inserted into a copper tube and all soldered with Sn63Pb37. The two prepared samples include five HTS tapes and four copper strips in untwisted manner. Self-field critical current at 77 K was analyzed both numerically and experimentally. The characteristics of in-plane (hard) and out-of-plane (easy) bending were analyzed by finite element method (FEM) and compared to experimental measurements. Good agreement was found between the analysis and experimental results on critical bending radius, which is about 200–215 mm. Our results indicate the robustness of the round strand and its potential for use in large-scale magnets.

A Novel Miniature Spring-Based Continuum Manipulator for Minimally Invasive Surgery: Design and Evaluation

Minimally invasive surgery is gaining wide-spread attention in the laboratory and the clinic due to its advantages of less trauma, less pain, and faster recovery. Miniature continuum instruments with a large central channel are needed for reducing damage to healthy tissue and delivering multiple surgical tools in microsurgery such as fetal surgery and maxillary sinus surgery. In this article, we proposed a novel miniature spring-based cable-driven continuum manipulator characterized by its offset neutral bending plane and its simple and clever structure. These features enable the manipulator to have several advantages such as easy miniaturization, bending stability and uniformity, a large central channel, smaller cable tension required, and low cost. A piecewise constant curvature model, with the offset neutral bending plane taken into account, is presented for the kinematic control of the proposed manipulator. To explore the relationship between the cable tension and manipulator bending angle, the statics model based on the equivalent model principle, is exhaustively discussed. The accuracy of kinematics and statics models, as well as the design superiority, was verified experimentally. Furthermore, teleoperation experiments of peg-transfer tasks and porcine tissue laser ablation are conducted to verify the feasibility and effectiveness of the proposed manipulator in different forms. Final, design variations are showcased to enrich manipulator design and functionality.

Study on the influence of bending curvature on the bending characteristics of unbonded flexible pipes

Unbonded flexible pipes are widely used in offshore oil and gas development as key equipment for offshore oil and gas transportation. Their biggest advantages are their flexibility and easy bending, making them more adaptable to the complex marine environment and the movement of offshore floating oil and gas platforms. These platforms also bring challenges to the structural design and analysis of flexible pipes. The mechanical response of each spiral strip layer used to construct the flexible pipe is the most complex response in the bending process. To analyze the bending performance of flexible pipes, this study focuses on the derivation of the explicit relationship between the bending curvature and the minimum critical curvature of a flexible pipe in the partial slip process of a spiral strip layer. An interlayer friction coefficient is introduced in the theoretical derivation, and complete expressions of the bending moment and bending stiffness for the non-slip, partial slip, and complete slip stages of the spiral strip layer are established. The expressions explain the hysteresis phenomenon of the bending characteristics of flexible pipes under a bending load. The results show that the hysteresis present when analyzing the bending moment-curvature relationship and the bending stiffness-curvature relationship of flexible pipes is mainly caused by the nonlinearity of the bending moment-curvature relationship of the tensile armor layer, while the bending moment-curvature relationship of all other layers is linear and the bending stiffness remains constant. The contribution of the carcass layer, pressure armor layer and anti-wear layer to the bending moment and bending stiffness is very small. The minimum critical curvature is the key variable affecting the slippage of the spiral strips of the tensile armor layer. The minimum critical curvature has a linear relationship with the interlayer friction coefficient and a nonlinear relationship with the helix angle.

Bending Strain Sensitivity of Critical Current in REBCO Coated Conductor Winding for Coil Application at 77 K

High-temperature superconducting (RE)Ba₂Cu₃ O_7-x (REBCO)-coated conductor (CC) tapes are known for their capacity to tolerate high tensile stress under uniaxial tension, which is typically in the range of 600-700 MPa at 77 K. However, when used in a coil, there is a limit to the allowed strain before degradation of the critical current (<i>I</i>_c) occurs. This is attributed to the combined strain due to bending and axial tension which was caused during fabrication, cool down, and operation of coils and magnets and corresponds to the irreversible strain limit of <i>I</i>_c degradation. Applied strain along the CC tape&#x0027;s edgewise direction (hard bending strain) also affects the irreversible strain limits of <i>I</i>_c considerably. With such conditions, degradation of the REBCO coil performance can be expected. Therefore, the current study aims to systematically investigate the mechanism for such <i>I</i>_c degradation in REBCO coils. Linear superposition of strains induced in different modes of easy and hard bending were studied analytically and experimentally. The <i>I</i>_c degradation behaviors were examined in IBAD&#x002F;REBCO CC tapes in windings with different pitches on mandrels with different diameters. The investigation was done at 77 K and in self-field conditions using an apparatus designed for coil testing. The bend strain parameters in coils were analyzed, including the radius of curvature and pitch between CC tape turns. Through the linear superposition of strains induced in the REBCO coils, an appropriate approach is suggested to effectively handle the <i>I</i>_c degradation under winding including edgewise bending.

Tesla Valve-Based Flexible Microhybrid Chip with Unidirectional Flow Properties.

Flexible microfluidic chips have good application prospects in situations with easy bending and complex curvature. An important factor affecting the flexible microfluidic chip is its structural complexity. For example, the hybrid chip includes flow channels, mixing chambers, and one-way valves. How to achieve the same function with as few structures as possible has become an important research topic at present. In this paper, a Tesla valve micromixer with unidirectional flow characteristics is presented. A passive laminar flow Tesla valve micromixer is fabricated through 3D printing technology and limonene dissolution method. The main process is as follows: First of all, high impact polystyrene (HIPS) material was employed to make the Tesla valve channel mold. Second, the channel mold was dissolved in the limonene solvent. The mold of Tesla micromixer is made of HIPS material, the mixing experiment displace that the Tesla valve micromixer is characterized by unidirectional flow compared with the common T-shaped planar channel. At the same time, the 5-AAC Tesla valve micromixer can increase the mixing efficiency to 87%. By using four different groove structures and different flow rates of the mixing effect experiment, the conclusion is that the mixing efficiency of the 6-AAC Tesla valve micromixer is up to 0.89 when the flow rate is 2 mL/min. The results manifest that the Tesla valve structure can effectively improve the mixing efficiency.

Mini Implant Punch (MIP)

Implant placement has always been a difficult task to accomplish. Several designs and methods have been proposed for precise implant placement in order to gain absolute anchorage in orthodontics. Implant placement grids and templates have always been used for placing mini implants since 1980. The aim of this article is to provide a simple and efficient method to construct an orthodontic Mini Implant Punch (MIP) made up of Australian 0.018″ stainless steel wire with easy wire bending.

High piezo–catalytic activity of ZnO/Al2O3 nanosheets utilizing ultrasonic energy for wastewater treatment

Abstract Designing and developing integrated energy conversion system that can effectively harvest and transform various type of energy shows great prospect. Here, we synthesize ultrathin ZnO/Al2O3 composite by calcination from its Zn–Al layered double hydroxide (Zn–Al LDH) precursor, whereas the ultrathin ZnO acts as active species that can directly utilize mechanical energy to drive chemical reaction. The thickness of the obtained ultrathin ZnO/Al2O3 composite is about 4.5 nm and its piezo–catalytic activity is assessed under ultrasonication. As−prepared ultrathin ZnO/Al2O3 composite exhibits higher piezo−catalytic reaction rate (k) over methyl orange dye (MO) degradation as compared to that of ZnO/Al2O3 with the thickness about 14 nm (k: 1.19 vs. 0.23 h−1). The experimental and simulated results indicate U–ZnO/Al2O3 exhibits easy bending deformation, which can result in higher piezoelectric potential (1.42 vs. 1.23 V at 105 Pa of balanced side pressure and unbalanced top pressure). Furthermore, with the ultrathining process, abundant surface oxygen vacancies (VO) appear. As a result, the content of surface free charges is enhanced due to the presence of VO, which can be driven by piezoelectric potential and then involved in the generation of radical species during the piezo–catalytic reactions. The generated hydroxyl radical (∙OH) is the active species and it mainly comes from transformation of superoxide radicals (·O2−). This work not only gives clear understanding of piezo–catalytic process but also sheds light a promising strategy for constructing piezo–catalytic materials with optimized geometric or electronic properties.

Out-of-plane bending characteristics of second generation high temperature superconducting tapes

REBCO tapes, known as second generation (2G) high temperature superconducting (HTS) tapes, are promising for their application in high field magnets and high current cables. However, in practical applications 2G HTS tapes always need to be bent, which causes the degradation of critical current. Therefore, it is necessary to study the bending characteristics of 2G HTS tapes. Studies have been carried out regarding easy bending and hard bending characteristics, but there has been no research into the characteristics of out-of-plane bending with different bending angles. This paper theoretically analyzes the out-of-plane bending with different bending angle characteristics of 2G HTS tapes and deduces the strain formula of different bending modes. Experiments on the bending characteristics of 2G HTS tapes were performed in liquid nitrogen. The experiments verified the theoretical calculation, and the results have significance for the applications of 2G HTS tapes.

Novel Design and Three-Dimensional Printing of Variable Stiffness Robotic Grippers

In this paper, a novel robotic gripper design with variable stiffness is proposed and fabricated using a modified additive manufacturing (hereafter called 3D printing) process. The gripper is composed of two identical robotic fingers and each finger has three rotational degrees-of-freedom as inspired by human fingers. The finger design is composed of two materials: acrylonitrile butadiene styrene (ABS) for the bone segments and shape-memory polymer (SMP) for the finger joints. When the SMP joints are exposed to thermal energy and heated to above their glass transition temperature (Tg), the finger joints exhibit very small stiffness, thus allow easy bending by an external force. When there is no bending force, the finger will restore to its original shape thanks to SMP's shape recovering stress. The finger design is actuated by a pneumatics soft actuator. Fabrication of the proposed robotic finger is made possible by a modified 3D printing process. An analytical model is developed to represent the relationship between the soft actuator's air pressure and the finger's deflection angle. Furthermore, analytical modeling of the finger stiffness modulation is presented. Several experiments are conducted to validate the analytical models.

Bio-Inspired Spring-Loaded Biopsy Harvester

Bio-Inspired Spring-Loaded Biopsy Harvester

Specific characteristics of mechanically and biologically compatible titanium alloy rods for use in spinal fixation applications

For implant rods as spinal fixation system, low Young's modulus, easy bending to an intended shape (low spring-back), and retaining initial bended shape during a long implantation (low aging-back) are essential properties. The rods were fabricated using a biomedical β-type titanium alloy, Ti–29Nb–13Ta–4.6Zr alloy (TNTZ), and their above-mentioned properties were evaluated in comparison with conventional biomaterials, commercially pure titanium, Ti–6Al–4V ELI, and SUS316L stainless steel. In the results of an animal experiment using implant rods made by TNTZ subjected to solution treatment with low Young's modulus, no negative effects are seen in the radiographs, and no inflammatory cells are observed in histological observation. In spite of low Young's modulus, the spring-back of TNTZ subjected to solution treatment is comparable to that of Ti–6Al–4V ELI. Further, its aging-back is quite small among the other materials.

Determination of winding diameter based on bending strain analysis for REBCO coated conductor tapes

In order to recognize the allowable bending diameter in coils, the strain as function of diameters is evaluated. The irreversible strain limits of <TEX>$I_c$</TEX> in the easy and hard bending modes were measured. Strains were calculated at the coating film in the easy bending and at outer edge or inner edge in the hard bending of the CC tape, respectively. The tape geometry subjected to bending procedures is considered from the current industrial spool winding operation. Through the linear superposition of strain induced in different bending modes regarding the expressions, the appropriate design for critical bending diameter is suggested. Results proved that the existence of buckling resulting from bending in hard direction when applied strain exceeded 0.6% is possible. The depicted results showed that the strain limit as a viable parameter should be considered for future purposes.

Self-Connected and Habitually Tilted Piezoelectric Nanorod Array

We fabricated a self-connected and habitually tilted ZnO nanorod (NR) array, which is free of any patterning process for the connection of the NRs and is easily bent by a normal force. The vertically well-aligned ZnO NRs were grown by a strain relaxation process on MgO-buffered C-plane sapphire, and the remaining epitaxial ZnO wetting layer acted as a self-connecting layer of NRs. The epitaxial ZnO film on the step-terrace structured substrate caused the tilting angle from the surface normal direction (~0.2°) to match the step between the ZnO film and MgO-buffered C-plane sapphire, resulting in easy bending of the ZnO NRs by normal force. The unsymmetrical strain between the tensile and compressive stressed region in the habitually tilted ZnO NRs caused a gradient in the piezoelectric potential, resulting in an electrical field along the lateral direction of NR growth, resulting in the control of the current direction and level to be about 0.1 μA/cm(2) at 2 kgf normal force.

Comparison of the Bending Strain Effect on Transport Property in Lap- and Butt-Jointed Coated Conductor Tapes

Although long-length superconducting wires are now being developed and manufactured, there is still a need for jointing in coil manufacturing and power cables for power distribution which requires miles in length. Therefore, it is important to develop an easy and practical jointing that has an acceptable electrical and mechanical integrity. Depending upon the applications, jointed coated conductor (CC) tapes will experience different stresses and strains during manufacturing and operation that could affect its transport property. Bending strain characterization is necessary since CC tapes are being wound into coils for magnet applications and other electrical devices. In this study, two joint types soldered by mechanical controlled jointing with uniform pressure application have been adopted. Critical currents of the jointed tapes have been measured at 77 K and self field. In the case of easy bending test, a new test procedure has been adopted considering the non-uniform flexural stiffness between jointed and unjointed parts of the sample. Relationship between the critical current and bending strain in easy bending mode has been investigated.

Bending Strain Characteristics of the Transport Property in Lap-Jointed Coated Conductor Tapes

The electro-mechanical properties of lap-jointed ReBCO coated conductor (CC) tapes have been investigated. Different contact configurations considering its geometry were adopted in this study. The configuration where the YBCO layer is in close proximity showed much less joint resistance. In all joint configurations, the electrical resistance decreased as the joint length increased. For HTS tapes, the joint resistance-joint length behavior could be explained by parallel circuit analysis. In easy and hard bending modes, the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> degradation behaviors in lap-jointed HTS tapes were examined. The critical radius for 95% I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> retention in each bending mode were determined.

Bending strain characteristics of critical current in REBCO CC tapes in different modes

The influences of bending strain on the critical current, I c in stabilized YBa 2Cu 3O 7− δ (YBCO) and SmBCO coated conductor (CC) tapes in different modes of easy and hard bending were investigated at 77 K and self-field. Under easy bending, the influences of the compressive and tensile bending strains on the I c in REBCO (rare earth element, Barium and Copper oxide) CC tapes were investigated. Under tensile bending strain, when the I c was plotted against the strain on the YBCO film layer, the 95% I c retention strain limit under bending was comparable to the value obtained in the axial-tension test. Under the hard bending of YBCO CC tape, I c started to degrade when the bending strain exceeded 0.6% and the recovery of I c did not occur when the bending strain applied was released. This might be a result of the generation of a new type of damage such as local buckling during hard bending which is different from the damage type experienced in Bi-2223 tapes. The n-value behavior showed a good agreement with the I c degradation behavior. On the other hand, the SmBCO CC tape showed a superior strain tolerance under hard bending resulted from its flexibility to in-plane deformation due to thin geometry compared to other copper stabilized YBCO CC tapes.

A new generation of plastic optical fibers and its functional exploiting

A major problem of plastic optical fibers (POFs) is large transmission loss in comparison with silica fibers. After adopting a new optical fiber structure, hollow-core Bragg fiber with cobweb-structured cladding, which can suppress the absorption losses of constituent materials by a factor of about 104–106, the problem of POFs with large losses is solved ultimately. With the advantage of flexibility and easy bending, the POFs with this structure can guide light with low transmission loss for information and energy in the wavelength range of visible light to terahertz (THz) wave (0.4–1000 μm). This new generation of POFs will find many applications.

Dynamic scattering of semirigid macromolecules

The polarized (VV) and depolarized (VH) dynamic light scattering functions of dilute solutions of semirigid macromolecules are calculated assuming that the scattering wave vector [under q] is high compared to the chain Kuhn segment l : ql>>1. The terminal relaxation rate is Gamma proportional to q8/3. Dynamics of both uniaxial and biaxial wormlike macromolecules (filaments) are considered. Biaxial macromolecules are characterized by two persistence lengths proportional to elastic constants for bending in two perpendicular directions (easy and hard bending). We showed that biaxiality may result in a significant broadening of the relaxation spectrum. A nonmonotonous q dependence of the depolarized scattering intensity is predicted. Analyzing the short-time behavior of the dynamic structure factor for t<<1/Gamma, we show that it is characterized by two additional characteristic times: t perpendicular proportional to q(-4) and t parallel proportional to q(-8) reflecting the transverse and the longitudinal dynamics of polymer chains. The longitudinal motions (along the chain contour) increase the initial relaxation rate of the structure factor by a factor of 2. The longitudinal contribution to the dynamic structure factor is significant even for t>>t parallel.

Comparison of bending strain effect on the critical current degradation of Bi-2223 tapes through different measurement techniques

Unlike in the tests under tension, transverse compression and torsion, the bending test of HTS tapes requires lots of time and effort since the sample should be bent or mounted successively onto sample holders having different bending radius at room temperature, and then cooled down to measure the critical current, Ic, up to 77K at each step. In this process, the effect of repeated thermal cycle on the Ic degradation can not be ignored. The establishment of a practical and effective measurement method of the critical current as a function of bending strain for HTS tapes should be considered. A ρ-shaped sample holder which provides a series of bending strains to HTS tapes was newly devised. In this case, the connection of Bi-2223 tapes to current terminal blocks was done mechanically. Using this sample holder, the bending strain effect on the Ic degradation behavior in Bi-2223 tapes in the easy bending mode was investigated, and discussed them comparing with other data obtained by different testing methods, namely, the conventional bending method using FRP sample holders and the Goldacker-type continuous bending test rig. Commercially available Bi-2223 tapes which have different reinforcing structures were supplied for this study. By using the newly devised ρ-shaped sample holder, it was possible to obtain a bending strain characteristic of Ic in Bi-2223 tapes at one time cooling which lessened the testing time significantly when compared with other testing methods and supply good reproducible data. The Ic degradation behavior in Bi-2223 tapes was similar to the cases using FRP sample holders although it showed slightly higher Ic values.