Violation of magnetic flux conservation by superconducting nanorings

The behavior of magnetic flux in the ring-shaped finite-gap superconductors is explored from the view-point of the flux-conservation theorem which states that under the variation of external magnetic field "the magnetic flux through the ring remains constant" (see, e.g., [L.D. Landau and E.M. Lifshitz, Electrodynamics of Continuos Media, vol. 8 (New York, Pergamon Press, 1960), Section 42]). Our results, based on the time-dependent Ginzburg-Landau equations and COMSOL modeling, made it clear that in the general case, this theorem is incorrect. While for rings of macroscopic sizes the corrections are small, for micro and nanorings they become rather substantial. The physical reasons behind the effect are discussed. The dependence of flux deviation on ring sizes, bias temperature, and the speed of external flux evolution are explored. The detailed structure of flux distribution inside of the ring opening, as well as the electric field distribution inside the ring's wire cross section are revealed. Our results and the developed finite element modeling approach can assist in elucidating various fundamental topics in superconducting nanophysics and in the advancement of nanosize superconducting circuits prior to time-consuming and costly experiments.

Experimental Investigation to Study the Feasibility of Fabricating Ultra-Conductive Copper Using a Hybrid Method

Ultra-conductive copper (UCC) has an enormous potential to disrupt the existing electrical and electronic systems. Recent studies on carbon nanotubes (CNTs), a new class of materials, showed the ballistic conductance of electricity. Researchers around the world are able to demonstrate ultra-conductivity in micro- and millimeter-length sections using various processing techniques by embedding CNTs in the copper matrix. Although multiple methods promise the possibility of producing copper-based nanocomposites with gains in electrical conductivity, thus far, scaling up these results has been quite a challenge. We investigated a hybrid method of both hot-pressing followed by rolling in order to produce UCC wire. Cu/CNT billets of 1/10%, 1/15%, and 1/20% were hot-pressed and the conductivity results were compared to a hot-pressed pure copper billet. Our results indicated that this method is not a viable approach, as the gains in electrical conductivity are neutralized, followed by attenuation of the wire cross-section.

Guidelines for 3D printed springs using material extrusion

Purpose Springs are an integral part of mechanisms and can benefit from additive manufacturing’s (AM) increased design freedom. Given the limited literature on the subject, the purpose of this paper is to develop guidelines for fabricating helical springs using three-dimensional (3D) printing. Design/methodology/approach Polylactic acid (PLA) is the main material investigated, with ULTEM™ 9085 used as a comparison. The experimental procedure is to vary the spring parameters, print the springs and test them in tension or compression using constant velocity. Plots of the force and displacement are used to measure the linear and post-deformation spring constants. Loading of the springs is done both to breakage and cyclically. Cyclic loading is also used to observe the plastic behaviour of the springs. Parameters that are varied include wire and coil diameters, pitch, wire cross-section, in-fill and layer height. Findings A square wire cross-section is used, instead of a circle because it produces more consistent coils. In-fills make no significant difference in the elastic stiffness of the springs but the mono in-fill breaks at a greater extension, so it is recommended. Tension and compression springs are confirmed to behave the same when in the elastic regime. ULTEM™ 9085 produces consistently weaker springs compared to PLA. Variation of layer height shows that thinner layers increase the stiffness of the springs. Originality/value This study investigates the behaviour of 3D printed helical springs in tension and compression. Three guidelines are created: square wire cross-section, mono-directional in-fill and thin layers are recommended.

Modelling the stiffness of plastic springs manufactured via additive manufacturing

The helical spring is one of the most used components in mechanisms but there is little research on the application of 3D printing, also called Additive Manufacturing, to springs. Therefore, the objective of this paper is to derive a model for the stiffness of 3D printed springs. The equation assumes that springs are made of orthotropic material and with a rectangular wire cross-section, that is, die springs. A second version of the equation has also been postulated that accounts for the misalignment of the deposited tracks with respect to the direction of the coils due to the coil pitch. The two models are compared to various springs printed with PLA and ULTEM 9085 and are found to accurately predict the stiffness of real, 3D printed springs. These equations allow the design and manufacturing of helical die springs for applications with few load cycles and that require chemical and radiation resistance, such as in space. The equations are also the first step in the development of models for new kinds of springs, such as linear conical springs or hollow wire die springs.

3D-printing pen from valorization of pine cone residues as reinforcement in acrylonitrile butadiene styrene (ABS): Microstructure and thermal properties

This study presents an alternative to reducing solid waste, improving the concept of green composites. So, the use of fibers from pine cone as reinforcement in acrylonitrile butadiene styrene (ABS) composites filaments as a potential for 3D pen was evaluated. The effect of the treatment chemical (alkaline and bleaching) was studied. A thermokinetic mixer processed the ABS/pine cone fibers (2 and 5% wt.) composites. After, the filaments were prepared by mini extruder and printing 3D pen. Filaments were characterized by Scanning Electron Microscopy (SEM), Thermogravimetry (TGA), and Infrared Spectroscopy (FTIR). Filaments revealed homogeneous diameters. The addition of 2 and 5% wt. fiber not significantly influenced the filament’s diameter and density. On the other hand, thermal stability and morphological analysis influenced the type of fiber (raw, treated, and bleached). The addition of bleached fibers to ABS increased composites’ thermal stability compared to other fibers (treated and raw). Also, inserting bleached fibers was perceptible a uniformly distributed and embedded throughout the wire cross-section compared to treated and raw fiber added to ABS due to good interfacial bonding. Results indicated that fibers were hydrogen-bonded to ABS chains and increased the filament’s density. So, it is possible to affirm that the addition of fibers from pine cone to ABS thermally improved and can be a low-cost feedstock for printing 3D pen applications. Despite the low concentration of natural fiber on the composites investigated in this work, the successful obtainment of ABS reinforced with biodegradable natural fiber, compromising neither its thermal properties nor its processability and printability, opens the possibility for future work investigation into a composite with larger fiber content.

An Indirect Method of Micromagnetic Structure Estimation in Microwires

The tunable magnetic properties of amorphous ferromagnetic glass-coated microwires make them suitable for a wide range of applications. Accurate knowledge of the micromagnetic structure is highly desirable since it affects almost all magnetic properties. To select an appropriate wire-sample for a specific application, a deeper understanding of the magnetization reversal process is required, because it determines the measurable response (such as induced voltage waveform and its spectrum). However, the experimental observation of micromagnetic structure of micro-scale amorphous objects has strict size limitations. In this work we proposed a novel experimental technique for evaluating the microstructural characteristics of glass-coated microwires. The cross-sectional permeability distribution in the sample was obtained from impedance measurements at different frequencies. This distribution enables estimation of the prevailing anisotropy in the local region of the wire cross-section. The results obtained were compared with the findings of magnetostatic measurements and remanent state analysis. The advantages and limitations of the methods were discussed.

Formation features of structure of wire made of austenitic-martensitic trip-steel VNS9-Sh during drawing

Structural-phase transformations in various sections of austenitic wire rod made of martensitic trip-steel VNS9-Sh (23Kh15N6AM3-Sh) at various stages of cold drawing are discussed. It was found that the structure of the near-surface layers of the wire with a diameter of 0.36 mm is completely austenitic. Based on the results of computer simulation of the stress distribution in the wire cross section, an assumption was made about the nature of the formation of such a structure.