Taper Geometry Research Articles

A Custom Finite-Element Method Framework for Designing Superconducting Solenoidal Magnets and Coils With True HTS Tape Geometry

A Custom Finite-Element Method Framework for Designing Superconducting Solenoidal Magnets and Coils With True HTS Tape Geometry

Influence of the use of an adhesive connection on the joint strength of modular hip endoprostheses.

Modular hip implants enables a more precise adaptation of the prosthesis to the patient's anatomy. However, they also carry the risk of increased revision rates due to micromotion at the taper junction. In order to minimize this risk, one potential solution is to establish an adhesive bond between the metal taper junctions. Load-stable bonding techniques, already successfully employed in dentistry for connecting materials such as metals and ceramics or different alloys, offer a promising approach. Nevertheless, the bond strength of tapered adhesive bonds in modular hip implants has not been investigated to date. Twenty-eight tapered junctions, consisting of a taper (female taper) and a trunnion (male taper) were turned using TiAl6V4 ELI (n = 16) and CoCr28Mo6 (n = 12). The process parameters cutting speed (vc = 50 m/min or 100 m/min) and feed (f = 0.1 mm, 0.05 mm or 0.2 mm) were varied for the trunnions. For each set of process parameters, one trunnion and one taper were additionally subjected to sandblasting. To investigate the effect of geometry, angular mismatch in the samples were measured. The taper pairs were bonded with a biocompatible adhesive, and push-out tests were subsequently performed. The push-out forces generated from the taper connections where both tapers were sandblasted showed a mean push-out force of 5.70 kN. For the samples with only the trunnion sandblasted, the mean force was 0.58 kN, while for the samples with only taper sandblasted the mean push-out force was 1.32 kN. When neither of the tapers was sandblasted the mean push-out force was 0.91 kN. No significant effect of the process parameters on the push-out force was observed. Only the reduced valley depth Svk showed a slight correlation for the CoCr28Mo6 samples (R2 = 0.54). The taper pairs with taper mismatch (between trunnion and taper) greater than |0.1°| did not show lower push-out forces than the specimens with lower taper mismatch. Sandblasted and adhesive-bonded tapered connections represent a viable suitable alternative for modular hip implant connections. Slight differences in taper geometry do not result in reduced push-out forces and are compensated by the adhesive. In mechanically joined tapers these differences can lead to higher wear rates. Further investigation under realistic test conditions is necessary to assess long-term suitability.

Ballistic Limit Equation Derivation for Thin Tape Tethers

Electromagnetic tethers of hundreds or thousands of meters have been proposed for maneuvring spacecraft in Low Earth Orbit, and in particular, for post-mission disposals. The debate on tether survivability to debris impact is still influencing further advances in the implementation of such technology because of the large area they expose to the debris environment; thin tape geometries have been proposed instead of round ones to increase the survivability to hypervelocity impacts. In this context, this paper introduces a new Ballistic Limit Equation (BLE) for thin tape tethers, derived from experimental results, numerical simulations, and literature data. The resulting equation is non-monotonic with respect to impact angle, presenting a minimum depending on the debris velocity and size; for high obliquities, the debris fragmentation triggered by shock waves propagating into the material reduces the damage. This feature allows to set a minimum particle diameter for risk assessment, excluding a significant part of the debris flux. The proposed BLE confirms the performance of thin tape tethers, with respect to round wires, due to their better ballistic response as well as their reduced cross-section at high-obliquity impacts.

Convective heat transfer with Hall current using magnetized non-Newtonian Carreau fluid model on the cilia-attenuated flow

PurposeCilia serves numerous biological functions in the human body. Malfunctioning of nonmotile or motile cilia will have different kinds of consequences for human health. More specifically, the directed and rhythmic beat of motile cilia facilitates the unidirectional flow of fluids that are crucial in both homeostasis and the development of ciliated tissues. In cilia-dependent hydrodynamic flows, tapering geometries look a lot like the structure of biological pathways and vessels, like airways and lymphatic vessels. In this paper, the Carreau fluid model through the cilia-assisted tapered channel (asymmetric) under the influence of induced magnetic field and convective heat transfer is investigated.Design/methodology/approachLubrication theory is a key player in the mathematical formulation of momentum, magnetic field and energy equations. The formulated nonlinear and coupled differential equations are solved with the aid of the homotopy perturbation method (HPM). The graphical results are illustrated with the help of the computational software “Mathematica.”FindingsThe impact of diverse emerging physical parameters on velocity, induced magnetic field, pressure rise, current density and temperature profiles is presented graphically. It is observed that the cilia length parameter supported the velocity and current density profiles, while the Hartman number and Weissenberg number were opposed. A promising effect of emerging parameters on streamlines is also perceived.Originality/valueThe study provides novel aspects of cilia-driven induced magnetohydrodynamics flow of Carreau fluid under the influence of induced magnetic field and convective heat transfer through the asymmetric tapered channel.

Property Variations in Modern REBCO Coated Conductors from Multiple Manufacturers

The complex, multilayer structure of REBCO Coated Conductor (CC) poses significant challenges in the fabrication of high magnetic field devices where large stresses may initiate various forms of damage. Our goal is to peer below the cartoon representations of CC so that, amongst other things, we might better understand whether a CC from one manufacturer is interchangeable with that from another. This involves knowledge of a broad range of electromagnetic, geometric, microstructural, and Jc (θ,B,T) properties, and their variations that collectively pose challenges for the fault tolerance of REBCO CC devices. Accordingly, comparative measurements of Jc , visualization of flux penetration with Magneto-Optical Imaging (MOI), tape geometry from Scanning Electron Microscopy (SEM) of polished cross-sections, and extensive optical microscopy was performed on recently purchased samples from multiple manufacturers. Our analyses reveal many deviations from or characteristics absent from manufacturers’ specifications, while a comparison of different manufacturers’ mechanically and laser slit tapes shows a diverse array of slitting characteristics amongst the manufacturers and variation in properties those made to the same specification. Laser slit tapes from several manufacturers reveal ablated edges with damaged regions extending up to 50 μm, comparable to the damaged region found in the mechanically slit CC of this study. Overall, the aim of this study is to flesh out appropriate ways to understand the real conductor below the manufacturers’ cartoons to avoid surprises in our REBCO CC coil development program. The goal of this work was to perform a broad array of characterizations of the type needed for validation of purpose for making high field magnets: to our surprise we found a wide range of properties which greatly impact the mechanical strength and electromagnetic performance of solenoids composed of these conductors and reinforced the need for a broad characterization program for each conductor prior to its implementation.

Folding mechanics of a bistable composite tape-spring for flexible mechanical hinge

A bistable composite tape-spring (CTS) structure is stable in both extended and coiled configurations, which can be fully coiled or folded. Its bistable coiling feature has been employed in a Roll-Out Solar Array and successfully deployed in space; its foldable characteristics is analogous to a flexible mechanical hinge, showing great potential to be applied in an aircraft landing gear. Both the structural coiling and folding mechanics are dependent on tape geometry; whilst the correlated scale effect has not been investigated, which significantly constrains its foldable mechanical hinge designs and smart driving analysis in order to further reduce weight and complexity for conventional mechanical hinges. Here, we studied the folding stability mechanics of the CTS structure towards its full tape-length range, where novel stress and shape transitional mechanisms are revealed. This is achieved by investigating the quasi-static folding process of the CTS, where new stable shape features in terms of critical transitional length and stable folded angle are observed and identified through experimental observations, finite element model, as well as theoretical analysis. Theoretical criteria were then determined from the strain energy analysis in comparison to the predefined folded tape shape features. The folding stability mechanisms towards its full tape-length range were proposed in order to facilitate customized flexible hinge design and in-situ smart driving analysis in order to replace conventional mechanical hinges.

Alternative analytical models for HTS tapes considering their AC hysteretic and resistive losses

This work proposes two alternative analytical models to evaluate the ac losses of high-temperature superconducting (HTS) tapes during their hysteretic and resistive modes. These models intend to extend the application range of state-of-the-art analytical models for current values higher than the critical one, i.e. for the resistive state, and to correctly predict the ac losses during the transition between the hysteretic and resistive modes. Two analytical models are proposed, one considering an extension of the Norris model for the HTS tape’s resistive mode and the other based on a sigmoid function to characterize the hysteretic losses and their smooth transition to the resistive mode. Analytical models capable of estimating ac losses of superconducting (SC) tapes are an important tool for the design of complex SC systems, such as SC fault current limiters, SC electrical machines and SC cables. The proposed models are validated experimentally, for a 1st generation BSCCO tape and a 2nd generation REBCO tape. Finite element simulation is also carried out to verify the accuracy of the proposed models. Results show that the proposed extended-Norris model presents some deviation at the transition between the hysteretic and resistive modes, while the sigmoid model presents very accurate results for the whole spectrum of applied current. Also, the parameters of the sigmoid models are independent of the tape geometry.

Modelling the non-steady peeling of viscoelastic tapes

We present a model to study the non-steady V-shaped peeling of a viscoelastic thin tape adhering to a rigid flat substrate. Geometry evolution and viscoelastic creep in the tape are the main features involved in the process, which allows to derive specific governing equations in the framework of energy balance. Finally, these are numerically integrated following an iterative scheme to calculate the process evolution assuming different controlling conditions (peeling front velocity, peeling force, tape tip velocity). Results show that the peeling behavior is strongly affected by viscoelasticity. Specifically, for a given applied force, the peeling can either be prevented, start and stop after some while, or endlessly propagate, depending on the original undeformed tape geometry. Viscoelasticity also entails that the interface toughness strongly increases when the tape tip is fast pulled, which agrees to recent experimental observations on tougher adhesion of natural systems under impact loads, such as see waves and wind gusts.

Performance prediction and optimization of annular thermoelectric generators based on a comprehensive surrogate model

A traditional system-level thermoelectric model requires enormous computing power and time for simulation analysis, especially when multiple optimization algorithms are combined. This paper initially proposed a comprehensive surrogate mode for the accurate modeling, field analysis, and fast optimization of thermoelectric generators. The surrogate model is made up of an artificial neural network (ANN) and a conditional generative adversarial network (cGAN), which can achieve a prediction accuracy of 97 % and a structural similarity (SSIM) of 0.954. Using a twisted tape annular thermoelectric generator (TT-ATEG) as an example, the generalization capability of the comprehensive surrogate model is demonstrated by studying the change of the twisted tape geometry parameters on the output performance and field distribution of the annular thermoelectric generator. The combination of the surrogate model and NSGA-II achieves fast optimization of key parameters under different working conditions, and the computational efficiency is improved by 99.97 %. Meanwhile, the cGAN part can predict the pressure and heat flow fields within 5s to provide intuitive visual feedback. The trained surrogate model requires less computer arithmetic power compared to the traditional multi-physics field simulation software. The successful application of the comprehensive surrogate model in this work provides a new solution idea and an optimization method for system-level TEG.

Tailoring the Mechanical Properties of High‐Fidelity, Beetle‐Inspired, 3D‐Printed Wings Improves Their Aerodynamic Performance

Miniature flapping drones can potentially operate in small spaces, using lightweight membranous wings. Designing these flexible wings appropriately is crucial for effective flight performance. 3D printing allows not only to fabricate high‐fidelity, insect‐inspired wings but also to further improve their design and shorten the development period for miniature flapping drones. Herein, a bioinspired approach is used to develop 3D‐printed wings based on the rose chafer beetle wings. By modulating the wing structure, 12 different wing models are designed that differ in the shape of the veins’ cross‐section, tapering geometry, and membrane thickness. The mechanical and aerodynamic properties of these models are compared, to establish guidelines linking wing form to function. It is shown that 1) the geometry of the veins’ cross‐section offers a powerful tool for engineering in‐plane and out‐of‐plane deformations; 2) tapering veins improve the wings’ mechanical stability, and 2) the membrane merges the mechanics of the individual veins into an integrated aerodynamically favorable structure. These result in 16% higher lift and 27% improvement in lift production efficiency (N/Watts) in a revolving wing setup. Designing light, flexible, robust, and aerodynamically efficient wings presents a formidable engineering challenge that insects have solved. Reverse engineering these intricate structures is empirically described herein.

Sonic black hole duct

The sonic black hole is a type of acoustic black hole that attenuates sound propagation via the acoustic black hole effect. This phenomenon is when an incident acoustic wave propagates through a power-law tapering geometry causing the wavelength to compress, the wave speed to decrease, and the time for the wave packet to reach the exit to extend infinitely. As a result, the wave never reaches the exit, so it cannot be reflected or transmitted. However, this outcome relies on the taper approaching exactly zero, which is impossible to manufacture. Therefore, the taper must be truncated leading to imperfect sound absorption. One method to increase the sound absorption is by applying perforations to the rings. This study explores the effect that varying the perforations on the sonic black hole’s rings has on the absorption coefficient from 1 to 5 kHz.

Method of heat transfer magnification by utilization of perverted tape with working substance water

Heat exchanger is a fundamental component of intensity and refrigeration cycles. These cycles encourage the exchange of vitality from a specific way to other depending on the righteousness of temperature contrast. Within a heat exchanger, there is change in the temperature of the liquid that flows through the exchanger, which results in the fluctuation of the divider’s temperature owing to the flow of liquid through the exchanger. Heat exchanger is capable of shifting the heat from the hotter to the cooler fluid, thereby managing the heat present within the framework. Therefore, the proposal is to quickly change the ideal measure of warmth vitality. The inventers of heat exchanger quickly formulated a productive and smaller heat exchanger at a nominal expense. For enhancing warmth movement, two strategies have been designed; one is a functioning strategy that needs an outside power source; and the other is an aloof technique with no need for outer power source. The change of heat transfer has been observed for numurous kinds of perverted tape geometries with the twist ratios of 2.5, 3 and 3.5 by changing the Re in the span of 4000 to 15000.

Trunnions and Modularity in Total Hip Arthroplasty: A Historical Review With Current Clinical Implications.

Trunnion in total hip arthroplasty refers to the interface between the neck of a femoral stem and the femoral head. Clinical complications arising from damage to this junction, whether it be due to mechanical wear, corrosion, or a combination, are referred to as mechanically assisted crevice corrosion (MACC), also commonly known as trunnionosis. With the use of modular hip prostheses, which help customize offset and leg length to an individual patient's anatomy, the incidence of MACC and revision due to MACC has increased in recent years. Although the cause of MACC is multifactorial, with patient factors and technique factors contributing to this condition, taper design and geometry, metallurgical properties of implants, and size mismatch of the bearing couple are some of the implant factors that have also been implicated in this clinical phenomenon. Understanding the history of taper design and geometry, the track record of older implants, and the rationale behind the development of current prostheses can help surgeons choose the right implants for their patients and accurately assess the pros and cons of new implants being introduced to the market each year.

Sonic black hole perforation study

A powerful and under-explored method to target unwanted reflection and transmission of sound is the sonic black hole. It is the application of the acoustic black hole effect to acoustic waves. The interaction between the propagating acoustic wave and the power-law tapering geometry of the sonic black hole effectively reduces the wave speed, so that it never reaches the termination and, as a result, cannot be reflected or transmitted. One method to improve the overall attenuation created by the ideal phenomenon of the acoustic black hole effect is by adding perforations to the sonic black hole. This study explores the effect that varying the perforation size will have on the sonic black hole’s transmission loss and reflection coefficient across a frequency range of 0 to 5 kHz. Approved for Public Release Distribution Statement A.

What Patient and Implant Factors Affect Trunnionosis Severity? An Implant Retrieval Analysis of 664 Femoral Stems

BackgroundCorrosion at the modular head-neck taper interface of total and hemiarthroplasty hip implants (trunnionosis) is a cause of implant failure and thus a clinical concern. Patient and device factors contributing to the occurrence of trunnionosis have been investigated in prior implant retrieval studies but generally with limited sample sizes and a narrow range of models. The purpose of the present investigation was to determine which patient and device factors were associated with corrosion damage on the femoral stem taper across a large collection of different implant models retrieved following revision hip arthroplasty. MethodsA retrieval study of 664 hip arthroplasty modular stem components was performed. Patient and device information was collected. Trunnions were imaged under digital microscopy and scored for corrosion damage using a scaling system. Damage was related to patient and device factors using regression analyses. ResultsGreater duration of implantation (P = .005) and larger head size (P < .001) were associated with an elevated corrosion class. Older age at index surgery (P = .035), stainless steel stem material (P = .022), indication for revision as bone or periprosthetic fracture (P = .017), and infection (P = .018) and certain larger taper geometries were associated with a decreased corrosion class. ConclusionFactors identified as contributing to a higher or lower risk of more severe corrosion are consistent with most prior smaller retrieval studies. Surgeons should be aware of these risk factors when selecting implants for their patients and when diagnosing trunnionosis in symptomatic hip arthroplasty patients.

Influence of FeCl3 and H2O2 in corrosion testing of modular taper connections in total hip arthroplasty: An in vitro study

Corrosion at the modular taper junctions in total hip arthroplasty is clinically relevant because wear particles and ions generated at this interface can lead to adverse local tissue reactions or even implant failure. In vitro tribo-corrosion tests are usually accomplished in saline solutions or calf serum (CS), but the addition of H2O2 and FeCl3 have been suggested to mimic inflammatory conditions in the joint. Inflammatory conditions may aggravate corrosive processes and, therefore, should lead in vitro to a more severe and realistic tribo-corrosive material attack. Corrosion testing at 12/14 tapers comprising a CoCrMo head taper and a Ti6Al4V trunnion was accomplished in five electrolytes (Ringer's solution (RS), RS with 30 mM H2O2 and/or 0.7 mM FeCl3 and CS) under dynamical loading for five million cycles. Resulting material loss was determined gravimetrically and by ion analysis. The tribo-corrosive material degradation was investigated by light and electron microscopy. FeCl3 enhanced the material loss from taper connections while H2O2 did not lead to a significant alteration of total material loss. In comparison to pure RS, corrosion testing in CS decreased material loss at the head taper while it increased material loss at the trunnion. The combination of FeCl3 and H2O2 led to an enhanced occurrence of micro cracks at the trunnion surface. Adding FeCl3 and optionally also H2O2 aggravates material loss in in vitro corrosion testing of taper junctions and leads to harsher and probably more realistic testing conditions. Statement of significanceTribo-corrosive processes at taper connections in hip implants are complex and can lead to major clinical implications. Joint inflammation is assumed to aggravate taper corrosion in vivo, why FeCl3 and H2O2 have been proposed as additives to electrolytes to simulate inflammatory conditions in vitro. Often used fretting test setups, however, do not involve real taper geometries. Besides, testing is often accomplished in saline solutions or calf serum, which do not induce a clinically significant amount of corrosive material degradation. This study presents an approach to increase tribo-corrosive processes at realistic taper connections by adding FeCl3 and/or H2O2. Unlike H2O2, FeCl3 increased material loss from taper connections. The combination of both additives enhanced micro crack formation at the trunnion surfaces.

A three-dimensional numerical study of the effects of various twisted tapes on heat transfer characteristics and flow field in a tube: Experimental validation and multi-objective optimization via response surface methodology

The main aims of the current three-dimensional numerical study are scrutinizing the effects of various twisted tapes on hydraulic-thermal performance and optimizing the geometrical parameters of a twisted tape geometry via response surface methodology. This study is carried out in three various phases. In the 1st phase, heat transfer characteristics of testing fluid through a tube which have a simple twisted tape is investigated. In this phase, numerical, experimental, and theoretical results are compared to each other. Then, the effects of different inserts on three key parameters, i.e., Nusselt (Nu) number, friction fraction (f), and thermal performance factor are investigated. After determining the superior twisted tape from the thermal performance factor aspect, in the final phase, an optimization study via response surface methodology is performed based on different objectives. According to the results, amidst the different inserts, the clockwise-counterclockwise and alternate axis twisted tapes ranked first from the highest thermal performance factor (1.46) and Nu number (34.27) standpoints, respectively. The lower friction fraction belonged to clockwise-counterclockwise type (f = 0.4068). The optimum value for twisted ratio, connection angle, and number of clockwise-counterclockwise strips, in order, is 3.02, 44.55°, and 1. Compared to tubes with and without simple insert, the Nu number increased by 46.2% and 221%, respectively, utilizing optimized clockwise-counterclockwise insert.

Self-Limited Formation of Bowl-Shaped Nanopores for Directional DNA Translocation.

Solid-state nanopores of on-demand dimensions and shape can facilitate desired sensor functions. However, reproducible fabrication of arrayed nanopores of predefined dimensions remains challenging despite numerous techniques explored. Here, bowl-shaped nanopores combining properties of ultrathin membrane and tapering geometry are manufactured using a self-limiting process developed on the basis of standard silicon technology. The upper opening of the bowl-nanopores is 60–120 nm in diameter, and the bottom orifice reaches sub-5 nm. Current–voltage characteristics of the fabricated bowl-nanopores display insignificant rectification indicating weak ionic selectivity, in accordance to numerical simulations showing minor differences in electric field and ionic velocity upon the reversal of bias voltages. Simulations reveal, concomitantly, high-momentum electroosmotic flow downward along the concave nanopore sidewall. Collisions between the left and right tributaries over the bottom orifice drive the electroosmotic flow both up into the nanopore and down out of the nanopore through the orifice. The resultant asymmetry in electrophoretic–electroosmotic force is considered the cause responsible for the experimentally observed strong directionality in λ-DNA translocation with larger amplitude, longer duration, and higher frequencies for the downward movements from the upper opening than the upward ones from the orifice. Thus, the resourceful silicon nanofabrication technology is shown to enable nanopore designs toward enriching sensor applications.

К ВОПРОСУ О ПРОЧНОСТИ КОМПОЗИТНОГО ШАРОБАЛЛОНА

In modern launch vehicles, combined composite structures in the form of thin-walled spherical shells are used as pressure accumulators and tanks. Such balloons consist of an inner metal body (liner), which ensures tightness, and an outer reinforcing composite shell, which ensures the operability of the structure.The paper presents a methodology for the design calculation of a combined composite balloon by using zonal winding on a liner. An analysis of publications on this topic showed that the requirements for the strength and continuity of the tape covering the entire surface of the balloon depend on the tape geometry, its width, thickness, the ultimate strength of the bundle along the fibers, the number of zones and the angular coordinates of the beginning of the zones. The even distribution of the location of the beginning of each zone, accepted by the authors in publications, leads to the need to use an excess number of winding turns to fulfill the strength conditions than is necessary for a continuous coverage of the zone surface.A rational design of the reinforcing composite shell will be in the case when the strength conditions and the conditions of the coating continuity are met in each zone with the same number of required tape turns. The algorithm is based on a sequential calculation of zone parameters. According to the known coordinate of the beginning of the first zone, the required number of turns of the tape is determined, which is necessary to fulfill the condition of the continuity of the coverage of the zone. The strength conditions in the first zone determine the angular coordinate of the beginning of the second zone. The calculation of the parameters of each zone is made taking into account the influence of the value of the width and thickness of the wound tape. Each subsequent zone is determined in the same way, taking into account all the previous zones.The paper compares the results obtained by the proposed method with the results known in the press. The performed numerical experiments showed that the proposed engineering technique allows to reduce the weight of the composite tape by 30%, and the designed spherical shell in this case will be thinner and has a more uniform distribution of the shell thickness along the meridian.

Characterization of edge damage induced on REBCO superconducting tape by mechanical slitting

Rare-earth barium-copper-oxide (REBCO) superconductors are high-field superconductors fabricated in a tape geometry that can be utilized in magnet applications well in excess of 20 T. Due to the multilayer architecture of the tape, delamination is one cause of mechanical failure in REBCO tapes. During a mechanical slitting step in the manufacturing process, edge cracks can be introduced into the tape. These cracks are thought to be potential initiation sites for crack propagation in the tapes when subjected to stresses in the fabrication and operation of magnet systems. We sought to understand which layers were the mechanically weakest by locating the crack initiation layer and identifying the geometrical conditions of the slitter that promoted or suppressed crack formation. The described cracking was investigated by selectively etching and characterizing each layer with scanning electron microscopy, laser confocal microscopy, and digital image analysis. Our analysis showed that the average crack lengths in the REBCO, LaMnO3 (LMO) and Al2O3 layers were 34 μm, 28 μm, and 15 μm, respectively. The total number of cracks measured in 30 mm of wire length was between 3000 and 5700 depending on the layer and their crack densities were 102 cracks mm−1 for REBCO, 108 cracks mm−1 for LMO, and 183 cracks mm−1 for Al2O3. These results indicated that there are separate crack initiation mechanisms for the REBCO and the LMO layers, as detailed in the paper. With a better understanding of the crack growth behavior exhibited by REBCO tapes, the fabrication process can be improved to provide a more mechanically stable and cost-effective superconductor.