Taper Geometry Research Articles

Optimized single-crystal diamond scanning probes for high sensitivity magnetometry

The negatively-charged nitrogen-vacancy center (NV) in diamond forms a versatile system for quantum sensing applications. Combining the advantageous properties of this atomic-sized defect with scanning probe techniques such as atomic force microscopy (AFM) enables nanoscale imaging of e.g. magnetic fields. To form a scanning probe device, we place single NVs shallowly (i.e. < 20 nm) below the top facet of a diamond nanopillar, which is located on a thin diamond platform of typically below 1 μm thickness. This device can be attached to an AFM head, forming an excellent scanning probe tip. Furthermore, it simultaneously influences the collectible photoluminescence (PL) rate of the NV located inside. Especially sensing protocols using continuous optically-detected magnetic resonance benefit from an enhanced collectible PL rate, improving the achievable sensitivity. This work presents a comprehensive set of simulations to quantify the influence of the device geometry on the collectible PL rate for individual NVs. Besides geometric parameters (e.g. pillar length, diameter and platform thickness), we also focus on fabrication uncertainties such as the exact position of the NV or the taper geometry of the pillar introduced by imperfect etching. As a last step, we use these individual results to optimize our current device geometry, yielding a realistic gain in collectible PL rate by a factor of 13 compared to bulk diamond and 1.8 compared to our unoptimized devices.

How Common Is Revision for Adverse Reaction to Metal Debris After Total Hip Replacement with a Metal-on-Polyethylene Bearing Surface?: Commentary on an article by Anders Persson, MD, et al.: "Revision for Symptomatic Pseudotumor Following Primary Total Hip Arthroplasty with a Standard Femoral Stem".

Commentary Adverse reaction to metal debris (ARMD) has resulted in a high short-term rate of failure of metal-on-metal (MoM) total hip arthroplasties (THAs)1. ARMD has also been observed after non-MoM THAs. Matharu et al. reported on a retrospective observational study of data from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. All 3,340 patients who underwent revision because of ARMD were included. The authors found that 95% of patients who underwent revision due to ARMD had an MoM THA, whereas 7.5% (249 patients) underwent revision of a THA with non-MoM bearing surfaces. The risk of revision due to ARMD was compared among different commonly implanted femoral head sizes and bearing surfaces. The relative risk of revision due to ARMD was 2.80 times (95% confidence interval [CI] = 1.74 to 4.36 times) higher for 36-mm metal-on-polyethylene (MoP) bearings compared with 28-mm and 32-mm MoP bearings (0.058% versus 0.021%; p < 0.001) and 2.35 times (95% CI = 1.76 to 3.11 times) higher for ceramic-on-ceramic bearings compared with hard-on-soft bearings (0.055% versus 0.024%; p < 0.001)1. Persson et al. evaluated 2,102 patients who underwent a total of 2,446 THAs, predominantly for osteoarthritis, from 1999 to 2016 in one center. In this observational cohort study, all patients underwent THA with the same uncemented Bi-Metric femoral stem and MoP (or, in a small number of cases, ceramic-on-polyethylene) articulation. The Bi-Metric femoral stem is a collarless, 3° tapered stem consisting of titanium alloy with its proximal 30% porous-coated (pore size, 100 to 200 μm) and plasma-sprayed with hydroxyapatite. The Morse-type taper consists of titanium alloy (Ti-6Al-4V) with a 4° taper angle, a distal diameter of 12.4 mm, and a contact length of 12.4 mm. The femoral heads were predominantly cobalt-chromium and 28 or 32 mm in diameter. The authors point out that the survival rate of these stems has been reported to be excellent in the literature2. The prevalence of revision for symptomatic ARMD was 0.5% (13 cases) after a mean follow-up of 7 years. The incidence rate was 0.9 case per 1,000 person-years. The strengths of this study include the evaluation of a large cohort of patients in which one well-performing cementless femoral stem was utilized. The data collection was carried out using the Swedish personal identity number and linked to the Swedish Hip Arthroplasty Register. This minimized the risk of the investigators missing additional revisions for ARMD that were carried out in other centers. It provides the incidence of revision for ARMD in one center, in a homogeneous population treated with a well-performing cementless stem with a 28-mm or 32-mm MoP articulation. The authors demonstrated that the rate of revision for symptomatic ARMD is low (0.5%) under these circumstances. They are to be congratulated for their contribution to the literature. The limitation of this study is the extent to which the data can be generalized to all THAs. The incidence of ARMD due to corrosion at the head-neck junction is multifactorial and includes implant factors, surgical factors, and patient factors. Implant factors that influence ARMD include head size, taper geometry, taper tolerances, taper surface finish, flexural rigidity of the neck, and material composition3. The findings in this study should not be applied to cohorts with different femoral head sizes or different tapers. Surgical factors that may impact the occurrence of ARMD include the surgical approach and its effect on the ability to maintain a dry, clean environment for the taper during impaction. In vitro studies have shown the cleanliness of the interface and the assembly forces to be correlated with the performance of the head-neck junction4. The findings presented by Persson et al. may not apply to centers using different surgical approaches or techniques for assembling the head-neck junction, particularly minimally invasive or anterior approaches. Finally, it is accepted that there is a large variation in an individual’s response to wear and corrosion debris generated from THAs. There is little correlation between the amount of wear and corrosion debris and the response to the debris in an individual patient. An individual patient may have substantial debris and exhibit little reaction to it while another may have a modest amount of debris but exhibit a substantial biologic response to it. This variation may be due to genetic polymorphisms, which can vary among different patient cohorts5. In conclusion, this study demonstrated a 0.5% prevalence of revision for ARMD at a mean of 7 years after MoP THAs performed in one center using 28-mm and 32-mm metal heads, a cementless femoral stem with a good long-term survival rate, and a single Morse taper. This finding should not be generalized to other patient cohorts using different femoral stems, femoral head sizes, or tapers implanted using different surgical techniques in different patient populations.

Taper’s angle influence on the structural integrity of single-lap bonded joints

The effect of conventional inside and outside tapers was addressed considering angles of 30°, 45° and 60°. The strain state of the joints was analyzed with an optical technique and an electrical gauge. Parametric studies were performed using the numerical method to investigate the role of taper geometries and taper angles on the stress distributions of adhesive joints. The statistical analysis of the numerical stresses reported within this paper allowed to get conclusions about which of the taper geometries conducted to higher adhesive compression levels. Experimental results showed that the reduction of the angles of taper increases the joint strength for all types of tapers and this was in agreement with the numerical results obtained from finite element analysis. The joints with outside tapers have higher tensile/shear strength than the joints with reverse or normal adhesive tapers. Local and global strains of the joints with the normal adhesive tapers showed different values, especially for the taper angle of 60°. The mid-line of the adhesive layer of the inside and adhesive tapers showed similar average shear-peel load levels, but because the inside taper geometry induces more compression of the adhesive and the position of the peaks of shear and peel stresses is not coincident, the inside tapering showed to be preferable.

Experimental investigation of heat transfer and friction coefficient of the water/graphene oxide nanofluid in a pipe containing twisted tape inserts under air cross-flow

ABSTRACTThe water/graphene oxide nanofluid effect in a pipe equipped by twisted tape inserts under air cross-flow is investigated and the optimal tape geometry is determined. The range of internal and external Reynolds numbers are: 3800<Reo<21500 and 550<Rei<2000. Heat transfer and pressure drop increase by increasing Re and inserts width and heat transfer performance coefficient increased up to 1.4, indicating enhanced heat transfer compared to undesirable pressure drop. On the other hand, the heat transfer coefficient is 26% higher when compared with water in a plain tube. According to the results, this method is a good alternative in heat exchangers.

The onset of fretting at the head-stem connection in hip arthroplasty is affected by head material and trunnion design under simulated corrosion conditions.

Mechanically assisted crevice corrosion (MACC) is a mechanism for trunnion damage in total hip arthroplasties (THAs). Retrieval studies have shown reduced MACC-related damage for ceramic heads compared with cobalt-chromium (CoCr) heads. We propose that ceramic heads demonstrate fretting at higher cyclic compressive loads than CoCr heads on titanium alloy trunnions in a simulated corrosion model. A closed electrochemical chamber was used to measure fretting current onset loads for two modern titanium alloy trunnions (Zimmer 12/14 and Stryker V-40) in which trunnion failure has been reported. Ceramic and CoCr alloy 36 + 0 mm heads were impacted on each trunnion and cyclically loaded at 3 Hz with increasing magnitude from 100 to 3,400 N for 540 cycles. Onset load was the cyclic compressive load at which the slope of the average fretting current increased significantly. A CoCr head with V40 trunnion demonstrated the lowest onset load (1,400 N), while the V40 trunnion with a ceramic head showed the highest onset load (2,200 N). Significant differences occurred in average fretting current between head materials for V40 trunnions (p < 0.001) at loads over 2,000 N. CoCr-12/14 and ceramic-12/14 couples demonstrated similar onset loads (2,000 N). All head-trunnion combinations showed cyclical fretting response to loading at 100 N. Head material composition was observed to increase fretting at the taper junction but the effect was taper geometry dependent. Using ceramic heads may reduce the phenomena of trunnion fretting and corrosion but the effect of both trunnion geometry and metallurgy warrants further investigation. Statement of clinical significance: Trunnion corrosion may occur with titanium alloy stems regardless of the head material used. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1630-1636, 2018.

Effect of Abrasive Waterjet Machining Parameters on Hybrid AA6061-B4C- CNT Composites

In general, Metal Matrix Composites (MMC)are very hard to machine using conventional machining due to complexity towards elevated temperature and tool wear issues. Abrasive water jet machining is a very efficient machining process which overcomes tool wear issues and cutting temperature issues. In this research study,AA6061-B4C- CNT was machined using Abrasive Waterjet Machining under different process parameters such as mesh size, abrasive flow rate, pressure and traverse speed. Boron carbide was used as reinforcement and Carbon Nanotube (CNT) was used as a solid lubricant. Two different composition of boron carbide (5, 15 vol%) and CNT (5, 15vol%) with residual volume percentage of aluminium as a core material were fabricated using stir casting method. The Machining approach is based on the Taguchi L9 orthogonal array design to enhance the Abrasive waterjet process parameters effectively. Then the multiple responses were investigated such as kerf taper geometries (θ), surface roughness (Ra) and material removal rate (MRR). The features of different machined surface regions were studied using Scanning electron microscopy (SEM). The investigational results indicate that increasing reinforcement improves the kerf taper angle under the significant parameter of traverse speed and decreasing the reinforcement leads to the lower surface roughness under significant parameter of pressure and traverse speed. It was observed that increasing reinforcement increasing the Material Removal Rate under the significant contribution of reducing mesh size of abrasive particles and inclined velocity.

Experimental Investigations on Multiple Responses in Abrasive Waterjet Machining of Ti-6Al-4V Alloy

In general, Ti-6Al-4V alloys are one of the challenging materials to machine using conventional machining process. Due to its high strength to weight ratio, good thermal stable property and exceptional corrosion resistance, Ti-6Al-4V became an attention-grabbing material to propose a proper modeling and machining for various types of applications. In this research study, Ti-6Al-4V was machined using Abrasive Waterjet Machining under different process parameters such as mesh size, abrasive flow rate, pressure and traverse speed. The Machining approach is based on the Box Behnken method to enhance the Abrasive waterjet machining process parameter for effective machining of Ti-6Al-4V. Then multiple responses were carried out such as kerf taper geometries (θ), surface roughness (Ra) and material removal rate (MRR). The structures of various machining surface regions were examined using Scanning electron microscopy (SEM). The experimental results specify that high pressure, low traverse speed, low abrasive mesh size and high abrasive flow rate were resulted in lower surface roughness in Ti-6Al-4V. And it was found that high pressure, high mesh size leads to minimum kerf taper ratio and whereas high traverse speed produce a maximum kerf taper. It was also evident that high abrasive flow rate, standard traverse speed and low pressure provide high MRR in selected conditions.

Optimization of WEDM Process Parameters on Multiple Responses in Cutting of Ti-6Al-4V

Ti-6Al-4V alloys are one of the toughest materials to machine using conventional machining process due to its high too wear ratio and high elevating cutting temperature. Owing to its fatigue resistance, excellent corrosion resistance, high strength to weight ratio and good thermal behavior, Ti-6Al-4V became a most important material to propose a proper modeling and machining for different types of applications. In this research study, Ti-6Al-4V was machined using Wire Electrical Discharge Machining under various process parameters like pulse on time TON, pulse off time TOFF, Wire feed, Servo Gap voltage and cutting speed. The approach is based on the Box Behnken method to optimize the WEDM process parameter for efficient machining. After the machining, multiple responses were examined such as kerf taper geometries (θ) and material removal rate (MRR). The topographies of different cutting surface regions were analyzed using SEM (Scanning electron microscopy investigation). The experimental results indicate that pulse on time, wire feed and servo gap voltage increases to increase the kerf taper ratio in Ti-6Al-4V machining. It was also observed that MRR increase with high pulse on time TON, low pulse off time TOFF and low servo voltage in the selected environmental conditions. By those multiple responses, it was evident that quality of cutting surface of Ti-6Al-4V at optimum condition obviously depends on different process parameter significantly.

The Effect of Metal Thickness on Si Wire to Plasmonic Slot Waveguide Mode Conversion

We investigate mode converters for Si wire to plasmonic slot waveguides at 1550 nm telecom wavelength. The structures are based on a taper geometry. We provide optimal dimensions with more than 90% power transmission for a range of metal (Au) thicknesses between 30-250 nm. We provide details on how to differentiate between the total power and the power in the main mode of the plasmonic slot waveguide. Our analysis is based on the orthogonality of modes of the slot waveguide subject to a suitable inner product definition. Our results are relevant for lowering the insertion loss and the bit error rate of plasmonic modulators.

Design of laterally restrained web-tapered steel structures through a stiffness reduction method

A stiffness reduction method for the design of laterally restrained web-tapered steel structures fabricated through the welding of individual steel plates is presented in this paper. Stiffness reduction functions for welded members, accounting fully for the deleterious influence of the spread of plasticity and imperfections on the structural resistance, are developed. The method is implemented through (i) dividing tapered members into prismatic segments along their lengths, (ii) reducing the flexural stiffness of each segment by means of the developed stiffness reduction functions considering the first-order forces and cross-section properties of each segment, (iii) performing Geometrically Nonlinear Analysis and (iv) making cross-section strength checks. Essentially, it is proposed to replace the current typical approach to structural design of conducting a simple elastic (with nominal stiffness) structural analysis followed by elaborate member checks with an integrated process utilising more sophisticated second-order analysis (with stiffness reduction) but very simple design checks. The distribution of internal forces within the structure is captured more accurately due to the allowance for imperfections, residual stresses and plasticity through stiffness reduction and the allowance for frame and member instability effects through the use of second-order analysis. The need for determining effective lengths and for conducting member buckling checks is also eliminated. Verification of the proposed approach against the results obtained from nonlinear shell finite element modelling is presented for various tapering geometries, slenderness values and loading conditions. Assessment of the proposed method against the European and North American steel design codes for tapered steel structures is also provided.

Quality Controlled UD Tape Production for the Individualised Production of Load Optimised Thermoplastic Composite Parts

A flexible and individual component manufacturing process for thermoplastic composites (TPC) has been developed at the Institut fuer Kunststoffverarbeitung in Industrie und Handwerk an der RWTH Aachen (Institute of Plastics Processing (IKV) at RWTH Aachen University). The process consists of a quality controlled tape production and a combined forming and joining process with additive manufactured functional structures. This paper describes the requirements for the unidirectional (UD) tape properties and the quality controlled tape production line in order to allow for a flexible and individual component manufacturing of load optimised thermoplastic composite parts. Besides the UD tape geometry and fibre impregnation quality an even fibre distribution over the width of the UD tape is an important characteristic. Results of investigations regarding the online measured quality data (fibre distribution) and offline measured UD tape properties (local fibre weight content) are presented and discussed.

Computational Investigation of the Thermal-Hydraulic Performance for Twisted Tape Enabled High Heat Flux Components

High heat flux thermal management is an important challenge for upcoming nuclear fusion and plasma physics experiments. The plasma facing components (PFCs) in devices such as ITER or Wendelstein 7-X (W7-X) will be subjected to extreme heat loads on the order of 10–20 MW/m2 in the divertor region. The heat dissipation issue will become critical in this next generation of experiments, and active cooling will be necessary. The current state-of-the-art water cooled technologies can accommodate extreme heat fluxes and often utilize passive heat transfer enhancement techniques, such as swirl flow, to decrease the thermal loading on PFCs. Swirling flow is commonly induced with a twisted tape that is inserted into a circular tube. Twisted tape devices are planned for use in both W7-X and ITER. Computational modeling was performed to investigate the thermal-hydraulic performance for single-phase, turbulent flow of water through a twisted tape device. This study exploited the advantage of computational simulations by analyzing local flow information. It was shown that points of low wall shear stress corresponded to locations of low heat transfer coefficient and high surface temperatures. Thus, decreased wall shear stress could be an indicator for early burnout in twisted tape geometries. This analysis was the first step towards informing the design of twisted tape devices utilized in PFCs.

Numerical Investigation of Thermal Performance Factor for different Twisted Tape Configurations

In this article an attempt has been made to study the heat transfer variations for different twisted tape geometry. Twisted tapes of different pitch and split ratios arranged in alternate clock and counter clockwise for fully developed laminar flow were used to study heat enhancement. The numerical analysis was carried out in different Reynolds number ranging between 400-1000 for a different pitch ratio (y = p/w, 3.2, 6.5 and 13) and split ratio (S=L/n, n=2, 3, 4), every split arranged in a counter clockwise with preceding one. The investigation revealed that decrement in pitch ratio and increment in split ratio enhances the heat transfer rate. Thermal Performance factor (TPF) is also calculated for different tape configurations and its variation is also notified in the work.

Geometry and evolution of fold-thrust structures at the boundaries between frictional and ductile detachments

Fold-thrust belts formed above a ductile detachment typically contain detachment folds, whereas those formed above frictional detachments contain fault-related fold complexes, such as imbricate thrust systems. Analog models, using silica sand to represent sediments and silicone gel to represent salt were conducted to study the fold geometry, fold-fault relations, and sequential development of structures formed in each setting and at the boundaries between the two settings. The results showed a relatively thinner wedge above a ductile detachment, so that the deformation front propagated farther forward than that above a frictional detachment. The thrust front connects across the two settings with a significant change in position and a resulting change in orientation. The geometry of the deformation front is strongly controlled by that of the detachment boundary, so that an oblique detachment boundary results in an oblique thrust front in the transition zone. Modifications in the taper geometry also result from the presence of a frictional belt behind a ductile belt, the width of the ductile detachment which limits the location of the deformation front, and the lateral propagation of thrust faults between the two regimes. The experimental models can be used to explain observed geometries in natural examples of fold-thrust belts marked by transitions between frictional and ductile detachments.

Improved Near-Field Transducer Design for Heat-Assisted Magnetic Recording

Heat-assisted magnetic recording (HAMR) is the next-generation data storage technology that can address the challenge of increasing data storage capacity. The key to the design of an HAMR system is the near-field transducer (NFT) that focuses light to a very small scale in the range of tens of nanometers with a very high intensity. This is also associated with unwanted self-heating of the NFT, which is detrimental to the functionality of the NFT, and hence there is a need to improve NFT designs. We investigate a third dimension in the typical planer NFT design by introducing a taper in the model of an E antenna NFT design and study its effect on the optical and thermal performances of the NFT. We find that the proper optimization of the taper geometry gives rise to improved operation of the NFT. In addition, in terms of thermal figures of merit, its performance is also significantly superior.

Novel double step approach for optical sensing via microsphere WGM resonance.

The use of resonant whispering gallery modes (WGMs) for sensing exhibits various drawbacks and critical points related to the microsphere and tapered optical fiber fabrication tolerance. The uncertainty on the fiber taper and microsphere geometry or the gap between the microsphere and the fiber taper can complicate or limit the actual use of these devices for sensing, requiring peculiar calibration of the WGM based sensing set-up. An alternative double-step approach is proposed in this paper. In particular, the geometrical parameters of the set-up are recovered preliminarily and then the rare earth parameters are recovered via simple transmittance/gain measurements. The method is based on a refined electromagnetic model of the device suitably integrated with a particle swarm optimization (PSO) approach. The percent errors made on the up-conversion coefficients Cup and C3 are extremely low, being 0.75%, 0.05%, respectively. The procedure is very robust. It can be applied more in general, allowing the sensing of other physical parameters via simple transmittance measurements instead of wavelength shift ones, in both microsphere and microbubble based set-up.

Fretting and Corrosion at the Backside of Modular Cobalt Chromium Acetabular Inserts: A Retrieval Analysis

BackgroundAdverse local tissue reaction formation has been suggested to occur with the Modular Dual Mobility (MDM) acetabular design. Few reports in the literature have evaluated fretting and corrosion damage between the acetabular shell and modular metal inserts in this modular system. We evaluated a series of 18 retrieved cobalt chromium MDM inserts for evidence of fretting and corrosion. MethodsWe assessed the backsides of 18 MDM components for evidence of fretting and corrosion in polar and taper regions based on previously established methods. We collected and assessed 30 similarly designed modular inserts retrieved from metal-on-metal (MoM) total hip arthroplasties as a control. ResultsNo specific pattern of fretting or corrosion was identified on the MDM inserts. Both fretting and corrosion were significantly greater in the MoM cohort than the MDM cohort, driven by higher fretting and corrosion scores in the engaged taper region of the MoM inserts. ConclusionMoM components demonstrated more fretting and corrosion than MDM designs, specifically at the taper region, likely driven by differences in the taper engagement mechanism and geometry among the insert designs. The lack of significant fretting and corrosion observed in the MDM inserts are inconsistent with recent claims that this interface may produce clinically significant metallosis and adverse local tissue reactions.

One-Way Polarization Rotation by Indirect Interband Transitions

We report a theoretical demonstration of asymmetric polarized signal conversion by a sinusoidal-modulated taper polarization rotator. Based on indirect interband transition theory, periodical modulated taper introduces unidirectional conversion between quasi-TM/TE modes in a linear silicon-on-isolator system. The dependence on the sinusoidal perturbation parameters and the contribution of taper geometry are analyzed separately. The method and result presented here are expected to be valuable for the implication of on-chip isolation and optical signal processing.

Fabrication of Low Noise Borosilicate Glass Nanopores for Single Molecule Sensing.

We show low-cost fabrication and characterization of borosilicate glass nanopores for single molecule sensing. Nanopores with diameters of ~100 nm were fabricated in borosilicate glass capillaries using laser assisted glass puller. We further achieve controlled reduction and nanometer-size control in pore diameter by sculpting them under constant electron beam exposure. We successfully fabricate pore diameters down to 6 nm. We next show electrical characterization and low-noise behavior of these borosilicate nanopores and compare their taper geometries. We show, for the first time, a comprehensive characterization of glass nanopore conductance across six-orders of magnitude (1M-1μM) of salt conditions, highlighting the role of buffer conditions. Finally, we demonstrate single molecule sensing capabilities of these devices with real-time translocation experiments of individual λ-DNA molecules. We observe distinct current blockage signatures of linear as well as folded DNA molecules as they undergo voltage-driven translocation through the glass nanopores. We find increased signal to noise for single molecule detection for higher trans-nanopore driving voltages. We propose these nanopores will expand the realm of applications for nanopore platform.

A Size-Constrained 3-T REBCO Insert Coil for a 21-T LTS Magnet: Mechanical Investigations, Conductor Selection, Coil Design, and First Coil Tests

Recent progress in second-generation (2G) rare-earth-Ba2Cu3O7-x (REBCO) coated conductors (CCs) has paved the way for the development of all-superconducting magnets generating fields well above 23.5 T, i.e., beyond the limits of the present technology based on Nb3Sn. However, the design of REBCO coils still poses several fundamental and engineering challenges. In particular, the tape geometry and the highly anisotropic electromechanical properties require new approaches for coils. In REBCO magnets, the inner windings' layer changes (passing from the nth layer to the (n + 1)th layer) are particularly critical from the electromechanical point of view as in-plane bending of the tapes results in additional strain that adds up to the bending strain and adds to the out-of-plane winding strain and the strain induced by the Lorentz forces. With the goal of building an all-superconducting 24-T magnet consisting of a 3-T REBCO insert coil in a 21-T magnet, we have determined the mechanical and electromechanical application limits of various industrial 2-G high-temperature superconductor tapes. In a first step, we have investigated the influence of longitudinal mechanical strain on the electrical transport properties of industrial REBCO CCs at the insert's operating conditions. In a second step, we have investigated for these CCs the impact of in-plane bending in different layer-change configurations (layer change in one turn and in two turns). These experiments are accompanied by bending strain calculations linking layer-change configurations and in-plane bending with the tapes' longitudinal strain dependence of their critical current. We present the superconductor characterization, the material selection, the design, and the first tests of this size-constrained 3-T REBCO insert coil for a 21-T LTS magnet.