Outer Wire Research Articles

Development of 10 kA high temperature superconducting power cable for railway systems

The superconducting Bi2Sr2Ca2Cu3Oy “Bi-2223” tapes made with a powder-in-tube process laminated with a copper alloy have been used to design and develop a 5 m long multilayer concentric cable to be applied in railway systems. The electrical performance of the conductor has been evaluated with DC transport current at an economical 77 K (liquid nitrogen temperature) in the self-field. The inner and outer sheet wires were able to sustain electric currents of 10 130 A and 10 910 A, respectively. These values are sufficient for several types of commercial applications. The current values are significantly higher than the earlier reported ones in Bi-2223 or YBa2Cu3Oy “Y-123” superconducting cables, indicating that the tape quality has considerably improved.

Numerical and experimental study on the interaction cable structure during the failure of a stay in a cable stayed bridge

Corrosion, abrasion and fretting fatigue may cause deterioration and, eventually, the failure of a post-tensioning tendon or a stay cable on a cable supported structure. In the present study, the stress acting during the rupture on the remaining portion of the stay which fails is derived, and the role of the rupture time on the response of the structure is discussed from a theoretical and a numerical point of view. In addition, the load–time curve during the rupture and the total time of the rupture of undamaged and damaged wires of seven-wire steel strands are investigated in an experimental program defined on the basis of the previous theoretical results. In the locally damaged specimens, a notch is machined into their outer wires. The specimens are tested under tension at three different strain rates in order to determine the influence of this parameter on the rupture time and on the load–time curve. The damaged specimens also allow us to determine the influence of a local reduction of the cross section on the stiffness and ultimate load of the specimen.

One-dimensional imaging diagnostics of imploding dynamics for planar wire array Z pinch

The primary experiment results of imploding dynamics for single and double planar wire arrays, acquired by optical streak camera, are presented and analyzed. The results show that the interaction of adjacent single wire plasma for single planar wire array is not dus entirely to inelastic collisions, while a part of plasma can move into the center and form precursor plasma across the plane of wire array; the current of outer wire is larger than that of the interior of wire, the time of ablation stage is ~65% of the total imploding time, and only a part of mass participates in the imploding stage.

Surface ionization on tungsten in a varying ambient atmosphere

Experiments show that under suitable conditions the introduction of oxygen can raise the surface ionization current emitted by a heated tungsten wire by several orders of magnitude. The ions in this case are alkali ions originating from alkali silicates normally present as additives in tungsten. From the simultaneous observation, in a varying ambient atmosphere, of both the positive ion current produced by surface ionization and of the electron current due to thermionic emission, it is concluded that the large observed increase in positive ion current is not primarily a consequence of an increase in the work function of tungsten, but is mainly due to a reduction in the residence time of the ions on the ionizing surface. This appears to be caused by alkali ions being preferentially replaced as an adsorbate on tungsten by the impinging oxygen molecules. The observations suggest that the increased ion production does not occur on the outer wire surface, but at inter-phase boundaries within the wire.

On the Problem of Wire Rope Model Generation with Axial Loading

Independent wire rope core (IWRC) is one of the fundamental components of complex wire ropes. It is a complex geometry and constructed by wrapping wire strands over a straight wire strand. The outer wires of the IWRC are double helical shaped feature which can be only modeled using special treatment. The aims of this paper are to introduce a new technique of modeling wire rope with IWRC and to compare numerical results obtained from this model with available results in the literature. Therefore the model generation for a simple straight strand is explained and accuracy of this model is validated. Furthermore this modeling procedure is adapted to whole wire rope structure considering double helical geometry concept. The proposed rope model gives remarkable results by means of wire by wire analysis scheme. This model is found easier and more effective. The results show good agreement with other available results but with a simpler and more practical approach.Independent wire rope core (IWRC) is one of the fundamental components of complex wire ropes. It is a complex geometry and constructed by wrapping wire strands over a straight wire strand. The outer wires of the IWRC are double helical shaped feature which can be only modeled using special treatment. The aims of this paper are to introduce a new technique of modeling wire rope with IWRC and to compare numerical results obtained from this model with available results in the literature. Therefore the model generation for a simple straight strand is explained and accuracy of this model is validated. Furthermore this modeling procedure is adapted to whole wire rope structure considering double helical geometry concept. The proposed rope model gives remarkable results by means of wire by wire analysis scheme. This model is found easier and more effective. The results show good agreement with other available results but with a simpler and more practical approach.

Strain Gauge Method for Evaluating a Three-Dimensional Residual Strain State in ${\rm Nb}_{3}{\rm Sn}$ Wires

Abstract-Concerning the strain effect of superconducting properties for Nb3Sn wires, it is necessary to investigate a three-dimensional strain state that Nb3Sn superconductors truly experience in the composite wire. However, it is very difficult for Nb3Sn wires to obtain the three-dimensional residual strain components experimentally. We adopted the strain gauge that is directly glued onto the 1 mm outer diameter Nb3Sn wire, in order to quantitatively measure the three-dimensional distortions. To evaluate axial and lateral distortions of the wire, strain gauges were set in both axial and lateral directions. This measurement system can obtain the distortion detail in fields up to 27 T at temperatures ranging from 4.2 to 20 K. We measured the upper critical field Bc2% in a three-dimensional strain state for Nb3Sn wires. It was found that the wire architecture changes each residual strain in axial and lateral directions of the wire. Moreover, the Bc2 strain sensitivity that is related to the Bc2 variation is also affected by its architecture. We found that the axial tensile strain variation 0.3% roughly corresponded to the lateral compressive strain variation 0.1% for Nb3Sn wires. This means that the ratio of the lateral strain and the axial one for Nb3Sn wires is 0.3. The ratio of both residual strains in the axial and lateral directions is very important to examine the strain effect of Nb3Sn wires in detail.

Nested multilayered X pinches for generators with mega-ampere current level

A symmetric X pinch configuration that is conducive to using large numbers of wires on ≥1 MA pulsed power generators has been tested at 1 MA. Using an initial configuration of wires before their twisting, similar to nested cylindrical wire arrays, enables a geometrically simple, compact, multilayer wire configuration at the X pinch crossing region. Multilayer X pinches with the same or different materials in the inner and outer wire layers were tested. Optimization resulted in X pinch radiation sources with peak power comparable to the most successful single layer X pinch, but with a compact, single bright X radiation source more reliably obtained using the nested configuration.

Comparison of a Newly Designed Niti-S D-Weave Combination Covered Stent and Niti-S D-Weave Uncovered Stent for Decompression of Obstructive Colorectal Cancer: A Randomized Prospective Controlled Multicenter Study

Background: Uncovered and covered stent have been used for the decompression of gastrointestinal obstruction by cancer with contrary merit and demerit each other. The reobstruction due to tumor ingrowth and migration is the most important problem in stent insertion. To overcome these problems, the Niti-S D-Weave uncovered stent and its double layered covered stent (Taewoong Medical Co., Seoul, Korea) have been developed. The Niti-S D-Weave uncovered stent was designed to have good conformability and less migration, and its double layered covered stent (Niti-S D-Weave combination covered) consists of an interposing PTFE (polytetrafluorethylene) membrane to prevent tumor ingrowth and an outer uncovered nitinol wire to allow the stent to embed itself in the colorectal cancer to prevent migration. Aim: To compare the effectiveness of Niti-S D-Weave combination covered stent and Niti-S D-Weave uncovered stent in the decompression of colon obstruction and the prevention of migration and tumor ingrowth in patients with obstructive colorectal cancer. METHOD: Between June 2004 and May 2005, sixty-seven patients from five medical centers were treated with stent insertion for preoperative decompression or palliative purpose. Patients were randomized to either Niti-S D-Weave combination covered or Niti-S D-Weave uncovered stent group. Results: In sixty-seven patients (40 males; mean age 65.7 ± 14.5 years), twenty nine patients were treated for bridge to surgery and 38 patients for palliation of incurable colorectal cancer. Technical and clinical success rates of both groups were not statistically different (92.9% vs. 100% and 96.4% vs. 97.4% respectively). In surgical finding of colorectal cancer with Niti-S D-Weave combination covered stent, PTFE membrane blocked the tumor ingrowth and the wire of outer layer of stent was embedded into tumor, being expected to prevent migration. As early complications within 7 days after stent insertion, early stent occlusion and migration were not different in both groups. In stent insertion for the palliative purpose, delayed stent occlusion by tumor ingrowth occurred in 5 of 22 patients (22.7%) with Niti-S D-Weave uncovered stent and 1 of 16 (6.3%) with Niti-S D-Weave combination covered stent. Delayed stent migration occurred in only 3 (18.8%) patients with Niti-S D-Weave combination covered stent. However, the rates of delayed stent occlusion and migration were not statistically different in both groups. Conclusion: Newly designed double-layered covered stent (Niti-S D-Weave combination covered stent) could be useful in preventing both the stent migration and the tumor ingrowth after stent insertion.

Analyses on the Short-Term Mechanical Properties of Plastic Pipe Reinforced by Cross Helically Wound Steel Wires

Plastic pipe reinforced by cross helically wound steel wires, namely PSP, is a new plastic-matrix steel composite pipe developed in China recently. In order to understand the mechanical properties of PSP under internal pressure, a four-layer analytical model, which considers the torsion caused by the differences between the winding angles of the inner and outer steel wire layers, has been proposed using structural mechanics. The model includes an inner high density polyethylene (HDPE) layer, an inner steel wire layer, an outer steel wire layer, and an outer HDPE layer. To investigate the mechanical properties in inner and outer steel wire layers, the elastic parameters of the composite monolayer plate were deduced from the rectangle outside and circle inside model. During the elastic response of PSP subjected to internal pressure, the stresses and strains in four layers and pressures between the interfaces were obtained. Good agreement between theoretical results and experimental data was observed, which shows that the presented model can be employed to predict stresses, strains, and torsions in PSP. The failure modes and torque values between PSPs manufactured by two different methods were compared, and the influence of the change in the winding angle on the strain in the exterior surface was also discussed.

Failure analysis of a cableway rope

This study is focused on the failure analysis of a cable way rope composed by different wires in which the magnetoscopic analysis has pointed out a significant and abnormal number of failure indications after a relatively short time of service. Such a phenomenon has taken place in one of the longest worldwide cableway plant and it is interesting that the performed microstructural analysis has clearly indicated that the applied steel seems featured by a good soundness of the very fine perlite micro-structure that has not been interested in any way by the decarburation phenomena. Moreover, the realized micro-hardness tests indicate a reliable homogeneity of the strength properties featuring the steel along the wire section. On the other hand, the fractographic analysis clearly indicates that the source of the failure mechanism is the initiation of the cracks in the surface of the z-shaped wire of the outer wire layer in contact with the wires of the inner layer. The coupling of the different results seems to indicate that the most probable cause of the failure mechanism has to be found in the excessive pressure applied on the rope and to the consequent sliding between the external wire layer and the inner adjacent one that produces debris and the nucleation of the crack.

Implosion dynamics and K-shell x-ray generation in large diameter stainless steel wire array Z pinches with various nesting configurations

Nested stainless steel wire array variations were investigated on the 20MA Z machine [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)]. In order to reach experimentally observed electron temperatures near 3.8keV and excite the K shell, these ∼6.7keV photon energy x-ray sources must be of large initial diameter (45–80mm) which poses a concern for magnetic Rayleigh–Taylor instability growth. We discuss the implosion dynamics in these large diameter wire arrays, including an analysis of the ablation phase indicating that the prefill material is snowplowed at large radius. Nested array configurations with various mass and radius ratios are compared for instability mitigation and K-shell scaling. Degradation of the K-shell x-ray power and yield was observed for shots that did not have simultaneous implosion of the outer and inner wire arrays. Shots that were designed per this constraint exhibited K-shell yield scaling consistent with the model of J. W. Thornhill et al. [IEEE Trans. Plasma Sci. 34, 2377 (2006)] which had been benchmarked to single array results. This lends confidence to K-shell yield predictions using this model for future shots on the refurbished Z machine. Initial results employing a triple nested wire array to stabilize the large diameter implosion are also reported.

Generation of shear flow in conical wire arrays with a center wire

At the Nevada Terawatt Facility we investigated the generation of a sheared plasma flow using conical wire arrays with an additional wire located on the axis of the pinch. The additional center wire generates axial current carrying plasma that serves as a target for the plasma accelerated from the outer wires, generating a sheared plasma flow which leads to the growth of the Kelvin-Helmholtz instability. These experiments were conducted on Zebra, a 2 TW pulse power device capable of delivering a 1 MA current in 100 ns. This paper will focus on the implosion dynamics that lead to shear flow and the development of the Kelvin Helmholtz instability.

Condylar guidance: Correlation between articular morphology and panoramic radiographic images in dry human skulls

Several studies have shown the unreliability of recording and reproducing the condylar guidance in semiadjustable articulators. The purpose of this study was to determine the correlation between the anatomic shape of the articular eminence and the corresponding panoramic radiographic image in dry skulls. Two metal wires were adapted and fixed to the inner and outer surfaces of the articular eminences in 25 human skulls. The inner (thicker) wire was fixed to the middle of the most concave aspect of the articular eminence in an anterior-posterior direction. The outer (thinner) wire was attached to the inferior aspect of the zygomatic arch adjacent to the articular eminence. Panoramic radiographic images were recorded by the same operator at the same time and with the same panoramic radiographic unit (Orthoralix SD). Impressions were made of the condylar fossae in 25 human dry skulls. Tracings of the incline of the articular eminence on the panoramic radiographs and the impression sections were compared. Each measurement was repeated twice by 2 operators. The results were subjected to the Pearson correlation statistical analysis (alpha=.05). The outline of the articular eminence in a panoramic radiographic image was identified as a thinner superior radio-opaque line above a thicker radio-opaque outline of the inferior-lateral aspect of the zygomatic arch. A significant correlation was found between the sagittal inclination of the anatomic articular eminence outline and the corresponding panoramic radiographic image for both right (R=0.802; P=.001) and left (R=0.561; P=.004) sides. A significant correlation was found between articular eminences on left and right sides in the same skull (P=.025). The panoramic radiographic image of the sagittal inclination of the articular eminence consistently replicated the eminence inclinations in the 25 human skulls evaluated.

Determining Broken Wires in Unbonded Seven-Wire Strands Using Penetration Tests

Unbonded seven-wire prestressing strands provide the primary reinforcement in post-tensioned concrete slabs. Strand corrosion can result in broken wires, which require expensive inspections and strand replacements. During these inspections, strands that are suspected of being corroded are exposed and inspected visually and a screwdriver penetration test is performed. Penetration of the screwdriver between any two adjacent wires is an indication that one of the wires may be broken or that the strand is unstressed or de-stressed. In this study, penetration tests were conducted on corroded strands with broken wires. The purpose of the study was twofold: to determine the distance from an inspection location where a wire break may be detected using penetration tests and to determine how corrosion products between the wires of a strand affect the accuracy of the penetration tests. During testing, corroded strands were stressed to typical service-load levels and the load and boundary conditions of an unbonded, post-tensioned concrete slab were simulated. Two outer wires were cut in succession, and penetration tests were performed along the strand. It was observed that penetration can be achieved between a broken and an unbroken wire within a region where the strain in the broken wire is less than about 200*e.

Coaxial Waveguide Based Left-Handed Transmission Line

In this letter, a new realization of left-handed transmission line (LHTL) is presented; the proposed structure is realized by periodically loading the coaxial waveguide with gaps in the inner conductor and wires between the inner and outer conductors, the gaps and wires act as series capacitors and shunt inductors. The dispersion characteristic of this new LHTL is analyzed by means of high frequency structure simulator (HFSS) eigenmode simulation and microwave network theory, which exhibits LH behavior over a 60% bandwidth. A backward wave behavior is unambiguously demonstrated from HFSS driven modal simulation. The phase front is observed to be in the opposite direction with respect to the energy one for a finite nine-unit cell prototype.

Demonstrated transparent mode in nested wire arrays used for dynamic hohlraum Z pinches

The mass of the outer and inner wire array used to drive the baseline dynamic hohlraum (DH) with pedestal target [Sanford et al., Phys. Plasmas 13, 012701 (2006)] is reversed in order to determine if the nested wire array is operating in a hydrodynamic, or transparent-like mode [J. Davis et al., Appl. Phys. Lett. 70, 170 (1997)], when the outer array arrives at the radius of the inner array. In contrast to the baseline, mass reversal allows the modes to be distinguished by the difference in the timing of characteristic features of the x-ray radiation pulses in the two modes. For the reversed-mass DH, all parameters such as wire number, array radii, and target remained the same, except the diameters of the individual wires were adjusted to reverse the array masses. Measurements show unambiguously that the reversed-mass DH operates in a transparent-like mode, the outer array passing through the inner array with limited collisional interaction. Numerical simulations in the r-θ plane suggest that the underlying physics of the outer array collision with the inner between the two DHs (baseline and reversed-mass), remains similar, implying that the baseline also operates with transparency. Inflection in the rate of change of the current is measured 4–7ns after the radiation signal and is associated with the outer-inner array interaction, indicating that the rear portion of the resulting plasma shell of the outer array carries the current prior to the collision. Numerical simulations together with analytic theory describe probable dynamics of the current switching from the outer to inner array.

New Design Stents for the Palliation of Dysphagia in Patients with Irresectable Esophageal Or Gastric Cardia Carcinoma: A Randomized Study

Background: Stents are commonly used for the palliation of obstruction due to irresectable esophageal or gastric cardia cancer. One of the drawbacks of the presently used stents is the high percentage of recurrent dysphagia due to stent migration and tissue growth. New stents have been designed to overcome this unwanted sequel of stent placement. Aim: To compare the partially-covered Ultraflex stent (Boston Scientific, Natick, USA), with the newly designed fully covered Polyflex stent made of silicone with an encapsulated monofilament braid of polyester (Boston Scientific), and the Niti-S stent consisting of an inner polyurethane layer over its complete length and an outer uncovered nitinol wire (Taewoong Medical, Seoul, Korea) in patients with inoperable carcinoma in the esophagus or gastric cardia. Methods: Between June 2004 and May 2006, 125 patients were randomized to treatment with an Ultraflex stent (n = 42), Polyflex stent (n = 41) or Niti-S stent (n = 42). Patients were followed by scheduled telephone calls at 14 days after treatment, and then monthly for six months or until death. Recurrence of dysphagia, technical and functional outcome, and complications were analyzed with Kaplan-Meier curves and log rank testing. Health-related quality of life was assessed by EORTC C30 and EORTC OES18 questionnaires. Results: Technical problems occurred in 9 (7%) patients, mainly with a Polyflex stent (n = 7). Dysphagia improved from a median score of 3 (liquids only) to 1 (ability to eat some solid food) in all 3 stent groups. Recurrent dysphagia occurred more frequently with Ultraflex stents (p = 0.03), and was caused by tissue growth (Ultraflex stent 13/42 (31%) vs. Polyflex stent 4/41 (10%) vs. Niti-S stent 10/42 (24%)), stent migration (Ultraflex stent 7/42 (17%) vs. Polyflex stent 12/41 (29%) vs. Niti-S stent 5/42 (12%)), and food bolus impaction (Ultraflex stent 10/42 (24%) vs. Polyflex stent 2/41 (5%) vs. Niti-S stent 1/42 (2%)). There were no differences in complications between the three stent types, however two perforations occurred with Polyflex stents. No differences were found in general and disease-specific quality of life scores between the three stent types. Conclusions: All three stents are safe and offer the same degree of palliation from malignant dysphagia. The new fully covered stents have the advantage that re-interventions are less frequently needed, as the Polyflex particularly reduces tissue growth and the Niti-S stent migration rates. It may well be that recurrent dysphagia could be even more reduced by designing a stent that combines the non-metal material used for the Polyflex stent with the anti-migration wire of the Niti-S stent.

Investigation of ablation and implosion dynamics in linear wire arrays

Ablation and implosion dynamics were investigated by optical probing in linear wire arrays of different geometry. Formation of ablation jets begins on the outermost wires. In the beginning of implosion plasma bubbles arise in breaks on the outer wires. Implosion bubbles move to the next wire in the array and hit the plasma column with the speed >250km∕s. Imploding plasma moves to the center of the array cascading from wire to wire. Configuration of magnetic fields in the linear array can be changed by variation of wire spacing. The regimes of ablation and implosion in the wire arrays are found to differ with different wire spacing.

Estimating the Fatigue Life of Wire Rope with a Stochastic Approach

A method for estimating the fatigue life of wire ropes for elevators was developed. It is based on the assumption that the fatigue life of a wire rope is determined by the fretting-fatigue life of the wires from which the rope was made. Estimates done on a sample wire rope with this method are consistent with experimental measurements. The method of estimation involves four steps. First, a finite-element analysis is conducted to estimate the pressure between the wires. To take into account the behavior of the whole wire rope and each wire in the stress analysis, a zooming analysis is conducted. Second, a fretting-fatigue test on the wires is conducted to construct a fretting-fatigue database for them. Third, the fatigue life of each wire is estimated from the pressures between the wires and data from the fretting fatigue database. Finally, the fatigue life of the wire rope is estimated from the fretting-fatigue life of the individual wires. The rope's fatigue life estimated with this new method revealed some important findings: (1) the inner wires break earlier than the outer wires, and (2) the residual strength of the wire rope decreases rapidly after decreasing to 80% of the initial residual strength.

Mechanical Model for Unbonded Seven-Wire Tendon with Single Broken Wire

This paper presents the derivation and experimental validation of a mechanical model for unbonded seven-wire prestressing tendons with a single broken outer wire. The model has practical significance because corrosion of these tendons typically causes a single outer wire to fail first. The tendency for the tendon to deflect toward the broken wire causes strains in the unbroken wires to be unequal at any cross section. As a result, the strains in the two wires adjacent to the broken wire increase significantly due to the wire break. Equations are presented for: (1) the strains along the lengths of the broken and unbroken wires; (2) the affected length, where the broken wire can be detected because its strain is less than the strains in the unbroken wires; and (3) the prestress force remaining after the break occurs. Experimental data obtained from tests of seven-wire tendons performed on an 18.3 m (60 ft) long strongback beam validate the model.