Round Wire Research Articles

Guidelines for the choice of circumferential wrought wire and cast clasp arms for removable partial dentures

PurposeThe aim of this study was to establish guidelines for the selection of cast and wrought-wire clasps for removable partial dentures (RPDs) that would be appropriate for clinically encountered undercuts and facial curvatures. MethodsRandomly selected discarded casts were collected and 30 premolars and 30 molars were surveyed, sectioned to a line representing the clasp and scanned using a flatbed scanner. The average clasp curvature and length for each group was determined and a three-dimensional model printed, to which wrought wire clasps of 0.9- and 1.0-mm diameter were adapted. Standard wax clasp patterns were adapted and cast in a stellite alloy. Each clasp was deformed beyond its proportional limit; and the forces exerted at that limit and at deflections of 0.25 mm, 0.5 mm, and 0.75 mm were measured, and a safety limit was calculated that would ensure elastic deformation at the required undercuts. ResultsA table was produced with guidelines for those clasps that would provide the highest retentive force within the proposed safety limit. The highest forces were provided by cast clasps in a 0.25-mm undercut. Wrought round wire of 1-mm diameter provided the next highest retentive forces, in a 0.25-mm undercut for premolar clasps arms and 0.5-mm for molar clasps. ConclusionsThe results provide valid guidelines for the use of combinations of clasp material and undercut that would exert the maximum retentive force without deformation for both short (premolar) as well as long (molar) clasps, for wrought and cast clasps.

Influence of the Preformed Coil Design on the Thermal Behavior of Electric Traction Machines

Preformed coils are used in electrical machines to improve the copper slot fill factor. A higher utilization of the machine can be realized. The improvement is a result of both, low copper losses due to the increased slot fill factor and an improved heat transition out of the slot. In this study, the influence of these two aspects on the operational improvement of the machine is studied. Detailed simulation models allow a separation of the two effects. A preform wound winding in comparison to a round wire winding is studied. Full machine prototypes as well as motorettes of the two designs are built up. Thermal finite element models of the stator slot are developed and parameterized with the help of motorette microsections. The resulting thermal lumped parameter model is enlarged to represent the entire electric machine. Electromagnetic finite element models for loss calculation and the thermal lumped parameter models are parameterized using test bench measurements. The developed models show very good agreement in comparison to the test bench evaluation. The study indicates that both, the improvements in the heat transition path and the advantages of the reduced losses in the slot contribute to the improved operational range in dependency of the studied operational point.

Correlation of critical current density to quasi-biaxial texture and grain boundary cleanliness in fully dense Bi-2212 wires

The distinctive quasi-biaxial texture of Bi2Sr2CaCu2O x (Bi-2212) plays an important role in enabling high critical current density (J c) in Bi-2212 round wires (RWs). Here we studied three over pressure heat treated wires with J c varying by a factor of ∼10, all being fully dense. Using electron backscatter diffraction, we observed the differences in biaxial texture in these three wires. Transmission electron microscopy also revealed differences in grain boundary (GB) cleanliness and connectivity. These analyses showed that high J c is unambiguously correlated to the best biaxial texture, which is in turn correlated to slow cooling from the liquid melt into solid Bi-2212. However, at 4.2 K, there is a negligible difference in intragrain pinning in the three wires, suggesting that the J c variation by a factor of ∼10 is primarily due to variable filament and intergrain connectivity. The principal determinants of intergrain connectivity is the quasi-biaxial texture and GB cleanliness. Overall, J c optimization of the Bi-2212 RW is a complex multi-variable process, but this study shows that maximizing the biaxial texture quality is an important first step in such an optimization process.

Performance limits in REBCO tape for variation in winding parameters of CORC® cable and wire

The design and testing of high current superconducting cables made of ReBa2Cu3O7-z (REBCO) are still under development. It seems to have huge potential to overcome some of the difficulties associated Low Temperature Superconductors. One of the attractive features of CORC® cable compared to other cable types is that a former with a small diameter can be used. This allows a flexible and round wire shape of the cable showing symmetry in the radial direction. This paper aims at analyzing limitations of a simple superconducting CORC® cable design by varying parameters such as substrate thickness, copper stabilizer layer thickness, winding angle, and central former diameter. The CORC® cable modeling is started from the design to the production stage of the tape, then the winding of the tape over the central former is performed at room temperature. The winding is critical as in the process, compressive strain is induced in the tape. This paper also investigates the influence of different parameters on the performance and possible performance degradation of superconducting CORC® wire and cable. The result showed that Hastelloy thickness decreases from 0.05 to 0.02 mm, at 1 mm core diameter, the variation of maximum strain is 47 % and 52%, at 0.01 and 0.02 copper thickness respectively. The compressive strain is increased by 43 % when the core diameter decreases from 3 to 1 mm, at 0.02 mm Hastelloy thickness. Similarly, at 0.01 mm copper thickness, and 0.05 mm Hastelloy thickness, 50% increase of compressive strain is noted when the core diameter decreases from 3 to 1 mm.

Critical Current Distributions of Recent Bi-2212 Round Wires

Bi-2212 is the only high-field, high-temperature superconductor (HTS) capable of reaching a critical current density $J_{\text{c}}$(16 T, 4.2 K) of 6500 $\mathrm{A\cdot mm^{-2}}$ in the highly desirable round wire (RW) form. However, state-of-the-art Bi-2212 conductors still have a critical current density ($J_{\text{c}}$) to depairing current density ($J_{\text{d}}$) ratio around 20 to 30 times lower than that of state-of-the-art $\mathrm{Nb-Ti}$ or REBCO. Previously, we have shown that recent improvements in Bi-2212 RW $J_{\text{c}}$ are due to improved connectivity associated with optimization of the heat treatment process, and most recently due to a transition to a finer and more uniform powder manufactured by Engi-Mat. One quantitative measure of connectivity may be the critical current ($I_{\text{c}}$) distribution, since the local $I_{\text{c}}$ in a wire can vary along the length due to variable vortex-microstructure interactions and to factors such as filament shape variations, grain-to-grain connectivity variations and blocking secondary phase distributions. Here we compare $\sim$ 0.1 m length $I_{\text{c}}$ distributions of Bi-2212 RWs with recent state-of-the-art very high-$J_{\text{c}}$ Engi-Mat powder and lower $J_{\text{c}}$ and older Nexans granulate powder. We do find that the $I_{\text{c}}$ spread for Bi-2212 wires is about twice the relative standard of high-$J_{\text{c}}$ $\mathrm{Nb-Ti}$ well below $H_{\text{irr}}$. We do not yet see any obvious contribution of the Bi-2212 anisotropy to the $I_{\text{c}}$ distribution and are rather encouraged that these Bi-2212 round wires show relative $I_{\text{c}}$ distributions not too far from high-$J_{\text{c}}$ $\mathrm{Nb-Ti}$ wires.

Effects of Wire Diameter and Filament Size on the Processing Window of Bi-2212 Round Wire

High engineering critical current density (JE of 1300 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K and 15 T) in Bi-2212 round wire has been achieved through a partial melt, overpressure heat treatment process. JE varies strongly with processing conditions, particularly the maximum heat treatment temperature (Tmax). Increasing Tmax results in longer time in the melt (defined as the time between when Bi-2212 melts on heating and when Bi-2212 begins to form on cooling), more bridging between the filaments, lower JE, and higher ac losses. A wide processing window with a large range of Tmax that has a nearly constant JE is desired for processing large coils with large thermal mass and significant thermal time constants that may make precise control over the desired temperature - time profiles uncertain. Accordingly, we wanted to explore broadening the Tmax window by controlling the Bi-2212 powder melting or wire architecture design. Here we report on studies of the performance variation with Tmax for two production wires with a filling factor of about 20% and 85 × 18 filaments where filament size was varied by changing the wire diameter, a process which also shortens the distance between filaments. We found that wires with smaller filament diameter (9 to 11 μm) showed a peak JE at the low end of Tmax and also a JE that was more sensitive to Tmax. A JE - Tmax plot showed a plateau JE(4.2 K, 5 T) of ~1100 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> between Tmax of 886 and 894 °C for 1.0 and 1.2 mm wires, where JE is less sensitive to the wire diameter and Tmax. This JE plateau range is a preferred processing window for achieving high JE in coils.

First demonstration of high current canted-cosine-theta coils with Bi-2212 Rutherford cables

Future high energy physics colliders could benefit from accelerator magnets based on high-temperature superconductors, which may reach magnetic fields of up to 45 T at 4.2 K, twice the field limit of the two Nb-based superconductors. Bi2Sr2CaCu2O8-x (Bi-2212) is the only high-T c cuprate material available as a twisted, multifilamentary and isotropic round wire. However, it has been hitherto unclear how an accelerator magnet can be fabricated from Bi-2212 round wires and whether high field quality can be achieved. This paper reports on the first demonstration of high current Bi-2212 coils using Rutherford cable based on a canted-cosine-theta (CCT) design and an overpressure processing heat treatment. Two Bi-2212 CCT coils, BIN5a and BIN5b, were made from a nine-strand Rutherford cable. Their electromagnetic design is identical, but they were fabricated differently: both coils underwent heat treatment in their aluminum–bronze mandrels, but unlike BIN5a that was impregnated with epoxy in its reaction mandrel, the conductor of BIN5b was transferred to a 3D printed Accura Bluestone mandrel after the heat treatment, a process attempted here for the first time, and was not impregnated. BIN5a reached a peak current of 4.1 kA with a self-field of 1.34 T in the bore. This corresponds to a wire engineering current density (J e) of 912 A mm−2, which is two times that of BIN2-IL, a previous Bi-2212 CCT coil fabricated at LBNL, which used a six-around-one cable processed with the conventional 1 bar pressure melt processing. On the other hand, BIN5b reached 3.1 kA. The coils exhibited no quench training. All the quenches were thermal runaways that occurred at the same location. In addition, we report on the field quality and ramp-dependent hysteresis measurements taken during the test of BIN5a at 4.2 K. Overall, our results demonstrate that the CCT technology is a route that should be further investigated for making high field, potentially quench training free dipole magnets with Bi-2212 cables.

Impacts of Voids and Bridges in Bi2212 Multifilamentary Superconducting Wires on its Electrical Behavior

Multifilamentary Bi2Sr2CaCu2Ox (Bi2212) composite wires are the only high-temperature superconducting round wires (RWs) with sufficient critical current density (Jc) for superconducting magnets generating magnetic fields greater than 25 T. Previous works indicated that various voids in Bi2212 filaments and bridges between the adjacent Bi2212 filaments in Bi2212 RWs were generated after heat treatment. Such complicated microstructural structure will inevitably affect its electrical behavior. Previous studies only focus on single microstructural feature, voids or bridges. Hence, we developed a numerical model containing both voids and bridges to explore the comprehensive influence of these two microstructural features. Due to the preliminary results, it shows that the E-J relationships of the models with bridges and with infinity bridges are similar in the case of numerous bridges between filaments. It indicated that we can build a simplified geometry structural model by removing all the bridges and bonding the adjacent filaments directly. And then the parametric study of the voids was carried out and the results explained that the height (diameter) of void is the key factor to dominant its electrical behavior.

Effect of laser welding on mechanical properties of round-rectangular nickel-titanium (NiTi) orthodontic wires

ABSTRACT Objectives. To investigate the welding parameters on preparation of nickel-titanium (NiTi) orthodontic arch wires that can simultaneously level and retract anterior teeth by combining round wire to provide high flexibility with rectangular wire to provide high rigidity. The effects of voltage and number of welding points on tensile strength, transition temperature range (TTR), and penetration of laser beam were investigated. Materials and Methods. 15 mm segments of 0.018 in. round wire and 15 mm of 0.019 × 0.025 in. rectangular wire were laser welded under argon shielding. The laser voltage was varied between 170 and 210 V for one-point and two-point welding. Results. Incomplete welding was found only in one-point welding at low voltage while all others were joined completely. Mean maximum tensile force at fracture was increased with increasing voltage. One-point welding at 210 V gave rise to the highest force at fracture. Differential scanning calorimetry (DSC) of the welded joints showed a lack of the original TTR curve, indicating the loss of superelastic properties. Significance. Laser welding of NiTi orthodontic arch wires with different geometries provided acceptable strength for use in orthodontic treatment.

A Comparative Analysis of Force Deflection Property of Nickel-Titanium Wires of Four Manufacturers using Five Point Bending Test: An In-vitro Study

Introduction: Over the last century, material science has made rapid progress. In orthodontics, not only the materials improved, but also the philosophies have changed. Orthodontic wires, which generate biomechanical forces through brackets for tooth movement, are central to the practice of this profession. Aim: To measure the force deflection properties of Nickel-Titanium (NiTi) wires of four manufacturers, used during orthodontic treatment. Materials and Methods: In this in-vitro study, 480 NiTi wires from four different manufacturers [American Orthodontics (AO), 3M-Unitek (3M), Rabbit Force Orthodontics (RO) and Modern Orthodontics (MO)], of various cross-sections was obtained. Samples of each wire were obtained by cutting the straightest distal portion of an arch wire, thus an approximate length of 5.5 cms was recovered. These wires were subjected to a five point bending test. Five lower anterior stainless steel brackets of tooth number 31, 32, 41, 42 (MBT 0.022” Libral traders Centrino brackets) were fixed with the face of the bracket facing upwards on the acrylic block. Each NiTi wire was placed in the slots of orthodontic brackets and secured with stainless steel ligature wires. These wires were subjected to artificial saliva (Wet Mouth) for 30 days at 37°C. This temperature was regulated by using an incubator. The main assessment criterion was the force deflection property of the wire material. Force deflection was measured using a graph paper where initially the wire was placed and plotted on the graph paper. After the deflection of the wire, it was again placed on the same graph paper such that wire ends coincided and the force deflection at the highest point was measured in millimetres using a digital Vernier Caliper (Mitutoyu). The Design of Experiments (DOE) model was used for analysis and a three-way Analysis of Variance (ANOVA) with wire shape as covariate was used for analysing the variability. Results: A 0.014” NiTi wire showed more mean deflection when compared to 0.016” NiTi wire. When a comparison between 0.016”×0.022” and 0.017”×0.025” NiTi wires was done, mean deflection was almost the same. When round and rectangular wires were compared it showed more mean deflection in round wires. When AO was compared with other three manufacturers. A significant difference (p-value &lt;0.0001) was seen in the mean deflection values of MO and RO. When 3M was compared with the other three manufacturers a significant difference (p-value &lt;0.0001) was seen in the mean deflection values of MO and RO. Three-way ANOVA test with wire shape as co-variate showed a significant amount of difference (p&lt;0.0001) for AO, 3M wires with their counterparts. Conclusion: Round NiTi wires showed more force deflection as compared to rectangular NiTi wires. AO and 3M wires were superior as compared to RO and MO wires. Superelastic wires showed more deflection as compared to conventional and heat- activated NiTi. This can be attributed to the property of the wire. Stiffer the wire, less deflection was seen. Cost of the wire also played a role. Cheaper wires were not able to match the quality and standards of their counterparts.

Analytical-Numerical Approach to the Skin and Proximity Effect in Lines with Round Parallel Wires

Power and communication lines with round wires are often used in electrical engineering. The skin and proximity effects affect the current density distribution and increase resistances and energy losses. Many approaches were proposed to calculate the effects and related quantities. One of the simplest approximate closed solutions neglects the dimensions of neighboring wires. In this paper, a solution to this problem is proposed based on the method of successive reactions. In this context, the solution with substitutive filaments is considered as the first approximation of the true solution. Several typical arrangements of wires in single-phase communication lines or three-phase bus ducts are considered to detect the limits of applicability of the first approximation. The error of the first approximation grows with wire radius to skin depth ratio and wire radius to wire spacing ratio. When the wire radius to skin depth ratio is up to 1, and the gap between the wires is above the wire radius, the error is at a level of 1%. However, lowering the distance and/or skin depth leads to a much larger error in the first approximation.

Nano-sized amorphous/semi-crystalline boron ratio and external Mg effects on transport and structural properties in MgB2 IMD wires

In the present study, Mg diffusion process has been investigated by transport measurements and surface morphology analysis in round MgB2 wires made with internal Mg diffusion (IMD) method. These wires were produced using semi-amorphous boron, nano-sized amorphous boron or mixtures of them via cold drawing process. In addition to the conventional IMD wire production technique, a thin layer of magnesium was initially coated on the interior of the iron sheath and diffused into the boron powder during sintering. It has been found that Mg coating is effective on improving the engineering current density of IMD wires having relatively thick MgB2 cores. Surprisingly, Mg coating is also effective in non-stoichiometric hybrid IMD wires containing highly excessive amount of Mg.

Design and modelling of an anti-buckling compliant universal joint with a compact configuration

This paper presents a new compliant universal joint using four identical generic sheet flexures (short sheets) and a long wire beam. The compliant joint is compact and in mirror symmetry, and is robust to axial buckling in bi-direction. The compliance matrix of the generic sheet, including a straight sheet and an elliptical-arc-fillet (EAF) sheet, is improved at first. Then a normalization-based analytical model of the universal joint is derived, followed by mobility identification of the joint. The relationships between the straight-sheet joint's compliance and the length, width and thickness of the sheet are analysed quickly using the analytical model. The linear finite element analysis (FEA) is further applied to verify the analytical model for different joints. Given different geometrical parameters of the EAF sheet, their effects on the parasitic motion and the maximum deformation of the joint are elaborated. Nonlinear FEA is used to analyse nonlinearities of the joint consisting of straight sheets and a round wire beam, including the large deformation, load-dependent effect, and axial anti-buckling. Experimental results verify the accuracy of the derived analytical models and confirm the successful design of the proposed universal joint.

Prevalence and Characterization of Interaction of Retrievable Inferior Vena Cava Filters with the Spine in Patients Undergoing Complex Filter Removal

PurposeTo examine spinal interaction types and prevalence of inferior vena cava (IVC) filters in patients presenting for complex filter removal. Materials and MethodsThe records of 447 patients presenting for complex removal of IVC filters were reviewed, including patient demographics, IVC filter dwell time, filter fracture status, and computed tomography (CT) evidence of filter interaction with the spine. Spinal interaction was defined as a filter strut touching or penetrating into the vertebral body or disc. Patients with evidence of filter penetration and spinal interaction had abdominal CT that preceded filter removal assessed by 2 interventional radiologists to categorize the type of spinal interaction, including bony reaction and osteophyte formation. ResultsCT evidence of spinal interaction by the filter was found in 18% of patients (80/447). Interaction with the spine was more common in single point of fixation filters than filters with rails (P = .007) and was more likely in filters with round wires than flat wires (P = .0007). Patients with interaction had longer dwell times (mean [SD] 5.7 [4.46] y) compared with patients without interaction (mean [SD] 3.2 [3.85] y); this relationship was significant (P < .0001). Women were more likely than men to experience filter/spine interaction (P = .04). Filters with spinal interaction were more likely to be fractured (P = .001). Filter interaction was found in 38% (30/78) of patients with symptoms, including chest and back pain, compared with 14% (50/369) of patients without symptoms (P < .0001, odds ratio 3.99). ConclusionsRetrievable IVC filters may interact with the spine. These interactions are associated with longer filter dwell times, female sex, and round wire filter construction.

High Efficiency PMSM With High Slot Fill Factor Coil for Heavy-Duty EV Traction Considering AC Resistance

Electric vehicle (EV) systems require a high energy-efficiency traction motor so that the motors for EV traction should achieve high efficiency and power density. Hence, a permanent magnet synchronous motor (PMSM) for EV traction using a maximum slot occupation (MSO) coil has been investigated in this study. By applying the MSO coil, high torque density was achieved, but an additional loss, which decreases the efficiency, was incurred through alternating current (AC) resistance. To reduce the AC resistance of the MSO coil, the following process was performed: First, by investigation using the analytical method, pole/slot numbers, current density and number of parallel circuits affecting the frequency, the shape and number of conductors were chosen as important variables. Resistances of the MSO coil with a stator core were analyzed according to the chosen variables above. From the results, MSO coil applied PMSM with proper pole/slot numbers, current density, and parallel circuits was determined to improve the efficiencies at the base and maximum speeds. To accurately estimate the efficiency of the determined model, loss evaluation methods were explained. Subsequently, the determined MSO coil applied model was compared with the conventional model having round wires, and the improvements were verified by load testing.

Effect of ultrasonic-vibration drawing process on Bi-2212 round wires

Bi2Sr2CaCu2O8+δ (Bi-2212)/Ag round wires were fabricated by imposing ultrasonic-vibration drawing (UVD) technique during both the single-filament and multi-filament cold-drawing processes. The frequency of ultrasonic-vibration was set fixed at 20 kHz and different output power density levels had been altered by varied amplitudes. The influence of ultrasonic-vibration on the deformation process of Ag metal sheath, filament density, Ag/superconductor ratio, wire dimension, drawing force reduction, and the superconducting properties of final wires has been systematically studied. Softening effect of ultrasonic-vibration on the Ag metal can be deduced with the decreasing drawing flow stress and drawing force under certain amplitude. It was found that powder densification could be promoted and higher filament volume fraction as well as high wire diameter uniformity had been reached with the introduction of UVD process, leading to the enhancement of Jc and JE after proper heat treatment. Such technique could be considered in fabrication of Bi-2212 long wires as well as other superconducting materials.

Evaluation of irradiation effects on the microstructure and properties of Ag-sheathed Bi-2212 superconducting round wire for future application in CFETR

The Chinese Fusion Engineering Test Reactor (CFETR) is designed to build a fusion engineering Tokamak reactor generating fusion power of 200–1500 MW, and to test the breeding tritium during fusion reaction. This may require a maximum magnetic field up to 15 T in the central solenoid and toroidal field coils. New superconducting materials should be developed for satisfying the next-generation fusion reactors with critical requirements. Recently, Bi2Sr2CaCu2Ox (denoted as Bi-2212) is considered as one of the most promising potential superconductors to be used as the magnets in CFETR, however, they will be subjected to harsh irradiation under operating conditions. The irradiation effects of the high-energy helium ions on the Ag-sheathed Bi-2212 superconducting round wire have been explored for the first time in this work. The microstructure and the critical current at 4.2 K of the superconducting wire before and after irradiation have been carefully investigated. Room-temperature x-ray diffraction (XRD) profiles showed that all the peaks shifted rightward significantly with a broadened (111)Ag peak, indicating that the high-energy He+ irradiation resulted in appreciable defects and strain in the superconducting wire. Meanwhile, the in-situ high-temperature XRD tests showed that the lattice constant and the thermal expansion coefficient were deduced in the irradiated sample to be due to the presence of the generated defects. After irradiation, the grain size of the Ag sheath was refined, and the lattice of Bi-2212 superconductor was distorted obviously, as confirmed by transmission electronic microscopy. The critical current IC at 4.2 K of the superconducting wires in the field of 0–12T determined by the four-probe technique, decreased substantially after irradiation because of the lattice distortion and the consequently induced strain in the Bi-2212 superconductor. This work provides a solid basis for evaluating and understanding the irradiation effects upon the Ag-sheathed Bi-2212 superconducting wire, more promising for future application in CFETR.

Force‐deflection behavior of NiTi archwire at different configurations of bracket system

AbstractNiTi shape memory alloy archwire is widely used in orthodontic treatment, replacing stainless steel for the flat and low deactivation force it can offer. However, the presence of friction at the contact region of wire and bracket may cause the low deactivation force to be ineffective to induce tooth movement. This work evaluated the bending deformation behavior of NiTi archwire in application using conventional orthodontic stainless steel bracket in levelling treatment. Experimental test rig was developed to perform three‐brackets bending test at room temperatures (27 °C). The bracket used was 0.022‐in stainless steel and the archwire was 0.016‐in NiTi round wire. Fabricated polytetrafluoroethylene (Teflon) bracket was used as a control experiment to represent frictionless condition of deformation on three‐bracket bending. Additionally, elastomeric ligature was also used to evaluate the effect of friction produced by the elastomer. Bending tests were done at 3 different deflection magnitudes of 2 mm, 3 mm and 4 mm. The results show that bending deformation behavior of the wire on frictionless Teflon bracket produced a flat force plateau on both activation and deactivation. On the other hand, when stainless steel brackets were used, the force plateau exhibited positive gradient on the activation and negative gradient on the deactivation.

Evaluation of the Biomechanical Properties of Austenitic Stainless Steel Fixed Retainers

The insertion of the fixed retention is an important stage of the orthodontic treatment after fixed appliances. The fixed retainers used in orthodontic treatments must be passive towards teeth, without developing any stress. This characteristic is challenging to achieve due to the mechanical properties (bending properties, stiffness) of the materials the retainers are manufactured from. Residual stress might be generated because of their flexibility and because the chemical composition of the stainless steel wires.This study aims to determine the mechanical properties of different austenitic stainlees steel wires used in retention. Also, we have compared the mechanical properties of wires with different sizes, as well as wires with the same size, new and intra-orally used. The results confirm that the mechanical parameters of the two types of wires used in fixed retention (3 braided round wires and 6 braided Flat wires) present statistically insignificant differences. The study also reflects that the mechanical properties of the intra-orally used wires showed decreased values of the parameters.

Estimations of Stress Concentration Factors (Cw/Kts) For Helical Circular/Square Cross Sectional Tension-Compression Springs And Artificial Neural Network Modelling

Springs are used for various purposes in machine design as they can store energy under load, due to their elastic deformation characteristics. There are many types and profiles of springs. For a round wire helical compression or tension spring of small pitch angle, the Wahl factor, a correction factor (Cw) taking into account curvature and direct shear stress, is generally used in the design. The corresponding stress concentration factors, which may be useful for mechanics of materials problems, are obtained by taking the nominal shear stress τnom as the sum of the torsional stress (τ) and the direct shear stress (τ) for round wire. In the case of the wire of square cross-section, τnom is the sum of the torsional stress and the direct shear stress. For design calculations it is recommended that the simpler Wahl factor be used. The same value of max will be obtained whether one uses Cw or Kts. This study contains the determination of stress concentration factor and Wahl factor. For this aim, stress concentration factor charts were converted numerical values for round and square wires. These values were collected in an excel file. ANN (Artificial Neural Networks) model was developed using the data. It is an easy and convenient method, ANN model, was presented for the determination of stress concentration and Wahl factor for spring design.