Multistrand Cables Research Articles

Joints formation and bonding mechanism of ultrasonic welded multi-strand single core copper cables with copper terminals

• Metallurgical bonding of multi-strand single core copper cables with copper terminals was achieved by ultrasonic welding technology. • Formation of bonding interfaces involved plastic deformation, dynamic recrystallization, and dynamic recovery. • Fine equiaxed grains at the bonding interfaces were beneficial to increase the strength of the joints. The metallurgical bonding of multi-strand single core copper cables with copper terminals was achieved by ultrasonic welding technology. The joint forming process and bonding mechanism that involved plastic deformation, dynamic recrystallization and dynamic recovery were clarified. The necklace-like fine grains structures observed in the central areas of the bonding interfaces would significantly improve the T -peel strength of the joints.

Orthogonal experiments and bonding analysis of ultrasonic welded multi-strand single core copper cables

The join demand for multi-strand single core copper cables in battery packs is increasing vigorously for new energy vehicles. In this paper, the influences of ultrasonic welding parameters on the microstructure, gap fraction and T-peel strength of the copper cable joints were studied systematically by orthogonal experiments. Under the optimum combination of parameters (welding time = 0.8 s, pressure = 4 bar, amplitude = 62.4 μm), a contact joint with low gap fraction of 2.07% was obtained and the maximum T-peel force reached 432.9 N. The T-peel fracture characterized by dimples indicates that metallurgical bonding was formed between copper wires, rather than simple mechanical interlock. Furthermore, the electron backscattered diffraction (EBSD) technology was used to analyze grain boundary types and texture evolution during ultrasonic welding. After ultrasonic welding, continuous 〈111〉 texture and lots of large angle grain boundaries (LAGBs) that composed of high-density dislocations and substructure were found in bonding interfaces of copper wires, which indicates that serious plastic deformation has occurred in bonding region. When interfacial temperature of cables joints provides enough energy for dislocations motion and rearrangement, the dislocations and substructure nucleate and grow into equiaxed grains through the process of copper recrystallization under high interfacial temperature, which promotes the formation of new interfaces between the copper wires.

CRACKING OF STEEL GIRDER OF THE VAM CONG BRIDGE - THE INCIDENT CAN BE AVOIDED DURING THE CONSTRUCTION STAGE

Vam Cong cable-stayed Bridge which has a 450m main span length, is one of the Central Mekong Delta Region Connectivity Project and is located in Cuu Long Delta Region. It has a steel-concrete composite girder with four lanes, and the type of cable is a multi-strand cable. Cables support a cable-stayed bridge, and the negative reaction occurs by cables at the anchor pier. On November 14, 2017, during the construction of expansion joints at the P29 pillar, the contractor had discovered the CB6 cross beam to be cracked. The tear is more than 4 cm wide, extending about 2 m across the beam. In this article, the author will determine the exact location of the damage, analyze the factors and causes leading to the above damage. At the same time, it points out the errors in the construction process, especially in the monitoring process of the bridge during the construction phase. This can help to identify the phenomenon that has led to this severe damage early.

Surrogate model based approach to predict fatigue stress field in multi-stranded cables

The mechanical behavior at contact points in high-voltage electrical cable conductors is simulated to find where damage may occur. The presented approach is based on a numerical model that is referred to as the wire model. The critical zones are detected by simulating the mechanical behavior of a cable conductor section with a large number of contacts. For the wire model, a relevant regularized contact law that improves convergence of the contact algorithm compared to the standard contact law is implemented. This model is validated by making comparisons with experimental results available in the literature for various conductors. However, this approach employs a costly finite element method. In order to reduce the evaluation cost and allow sensitivity analysis of the input parameters, a surrogate model is proposed to replace the initial wire model. The surrogate model approximates the input–output relationship of the costly wire model. The choice of the sampling method that allows selection of the best fitting surrogate model for this application is discussed, but comparisons show little influence on the obtained scores. The robustness of the obtained result depends mostly on the chosen surrogate model, where the scores obtained with random forest and neural network are better than the scores obtained with linear and polynomial regression. The application is the French high-voltage network, but the work is relevant for any other network.

Strand element analysis method for interaction between cable and saddle in suspension bridges

A stable cable-saddle connection relying on the frictional resistance is essential for the safety of suspension bridges. However, the frictional resistance cannot be adequately quantified due to the unclear contact forces, giving rise to a thorny anti-slip problem that particularly troubles the design of multi-tower suspension bridges. In this paper, the cable-saddle interactions are therefore studied by means of theoretical modeling and experimental verification. First, the feasibility and strategy of analyzing the PPWS (prefabricated parallel-wire strand) cable from the perspective of strand are demonstrated. The geometric and mechanical models of 37-, 61-, 91- and 127-wire strands are created, and a strand element analysis (SEA) method with recursive algorithm is then developed. Large-scale model tests are further conducted to investigate the cable-saddle frictional mechanism and to verify the SEA method. Finally, a typical multi-tower suspension bridge is taken as an example for an extended case study. The results show that the proposed SEA method can offer reliable predictions for the contact behavior of multi-strand cables in the saddle. The strand tensions at the critical slip state are unevenly distributed, while slight changes are present on the average tensions of the strand on both sides of the saddle. The use of two vertical plates can improve the frictional resistance by about 30%, and adopting a fewer-wire strand specification and arranging the strands in a higher pattern is also beneficial to improve the cable-saddle frictional resistance.

Optimization of Spatial Configuration of Multistrand Cable Lines

Skin and proximity effects have a considerable impact on current distribution in multistrand cable lines. Under unfavorable heat exchange conditions, some strands may be subject to excessive overheating, which may lead to serious malfunctions or even fires of the installation. The paper proposes a new criterion for a quick choice of spatial configurations, for which the effect might be minimized. A comprehensive analysis of literature cases is provided, including the recommendations of the U.S. National Code and the Canadian standard.

Ultrasonic weld strength and weld microstructure characteristics in multi-strand aluminum cables (EN AW-1370) – Effect of process parameters

Abstract Analysis of the joint strength between multiple thin aluminum strands in multi-strand single core cables after ultrasonic welding was carried out by performing T-peel tests. Herewith, the effect of two process parameters, namely the sonotrode pressure and the amplitude of sonotrode vibrations on the joint strength was studied. It was found that a larger applied pressure resulted in a larger maximum T-peel force, while large magnitudes of pressure and amplitude at the same time decreased the fracture energy of the weld and resulted in a weak joint. Furthermore, 3D reconstruction of the images captured by computer tomography of the joint revealed that for a high pressure value and a low value of vibration amplitude, the structure of the weld under the sonotrode was much more compact compared to a high value of vibration amplitude and a low value of pressure. To this end, volume fraction of the gaps between the aluminum strands inside the microstructure of the weldment was quantified and compared between specimens with different process parameters. Finally, a correlation between the joint strength and the microstructure porosity (voids) of the weldment has been presented and discussed.

The complex multicellular morphology of the food spoilage bacteria Brochothrix thermosphacta strains isolated from ground chicken.

Herein we describe a highly structured, filamentous growth phenotype displayed by an isolate of the food spoilage microorganism Brochothrix thermosphacta. The growth morphology of this B. thermosphacta strain (strain BII) was dependent on environmental factors such as the growth media, incubation temperatures, and the inoculum concentration. Inoculation of cultures in highly dilute suspensions resulted in the formation of isolated, tight aggregates resembling fungal growth in liquid media. This same strain also formed stable, mesh-like structures in 6-well tissue culture plates under specific growth conditions. The complex growth phenotype does not appear to be unique to strain BII but was common among B. thermosphacta strains isolated from chicken. Light and electron micrographs showed that the filaments of multiple BII cells can organize into complex, tertiary structures resembling multistranded cables. Time-lapse microscopy was employed to monitor the development of such aggregates over 18 h and revealed growth originating from short filaments into compact ball-like clusters that appeared fuzzy due to protruding filaments or cables. This report is the first to document this complex filamentous growth phenotype in a wild-type bacterial isolate of B. thermosphacta.

Detection of terminal oscillation pattern in ultrasonic metal welding

Oscillation pattern of the mating parts during the ultrasonic welding process can provide reliable information about the fixation of the parts in the machine and possibly the bond quality. The present work is a very first attempt to in situ capture the oscillation pattern of the terminal. Terminals, made of a brass alloy, are the mating substrate in the process of ultrasonic welding of multi-strand single core aluminum cables in the automotive industry.In this research work, the time signal of the terminal oscillations is captured through piezoelectric transducers. Frequency spectrum of the time signal shows an excitation frequency of 20.3 kHz, which represents the operating frequency of the welding sonotrode. This spectrum also illustrates the novel discovery of the presence of higher-order harmonics at multiples of 2, 3, 4, and 5, i.e. 40.6, 60.9, 81.2 and 101.5 kHz, respectively.Moderate modifications of the geometry of the conventional terminal as well as changes of the terminal fixation in the ultrasonic welding machine are carried out in order to investigate the effect of these two important phenomena on the oscillation pattern of the terminal during welding.Observation of the frequency spectrum of the oscillations shows that terminal fixations during the ultrasonic welding process can strongly affect its vibration pattern, whereas the moderate geometry modifications do not show significant influences on the terminal oscillations.Results of the present study provide new insights into the fundamental understanding of the substrate vibration pattern and the possibilities to affect this pattern for the benefit of manufactured products using ultrasonic welding.

Investigation of long time constants of magnetic fields generated by the JT-60SA CS1 module

In a cold test of the JT-60SA CS1 module, which is composed of six octa-pancake coils and one quad-pancake coil wound with Nb3Sn CIC conductors, the measurement of self-magnetic fields generated by the CS1 module was conducted. As a result, the decay of the self-magnetic field was observed after the CS1 module was degaussed. The time constant of the decay was from 90 s to 269 s. The measurement results indicate that loop currents with long time constants occurred in the CS1 module due to coil energization. The loop currents with long time constants, which are also called ‘supercurrents’, are irregular coupling currents that are an unexpected phenomenon from the conductor design.Loop currents with long time constants in CIC conductors have only been observed in large superconducting coils so far. To verify an occurrence of loop currents with long time constants in a CIC conductor without coil winding configuration, self-magnetic fields were measured using a short straight CIC conductor where a multi-strand cable was connected electrically at the conductor ends. As a result, loop currents with long time constants ranging from 57 s to 105 s occurred in the short straight CIC conductor, the length of which is approximately 1 m. The measurement results indicate that the conductor length is not always related to loop currents with long time constants. The occurrence of loop currents with long time constants in the CIC conductor depends on the presence of current paths at the conductor ends.

Effect of process parameters on the interface temperature in ultrasonic aluminum wire bonding

In the present work, a very first attempt has been made to investigate the effect of two process parameters, namely the applied sonotrode pressure and the amplitude of the ultrasonic oscillations on the temperature rise at the interfaces of thin aluminum strands during ultrasonic welding (USW) of multi-strand single core cables. By measuring the temperature inside the wire bundle through thermocouples, it is found that increasing the amplitude of vibrations in the USW process of multi-strand cables is more effective in interface temperature rise than increasing the applied pressure.During USW of a strand bundle, the sonotrode pressure defines the potential positions for the weld points, whereas the amplitude of vibrations defines the degree of bonding at those points due to the effective heat generation as a result of sliding friction. A finite element model of the strand bundle displays the same trend for the effect of pressure as well as amplitude of vibrations on the interfacial temperature rise. Furthermore the applied pressure on the mating parts enhances the efficiency of the ultrasonic welding process, whereas an extended sonotrode pressure results in a lower temperature rise, as it prevents the strands from effectively sliding against each other. Microsections of the welded samples, which show the formation of different interfacial bonds under different sonotrode pressures, reveal that with an extended sonotrode pressure, strands undergo strong plastic deformations but a better bondability is not achieved. Observation of aluminum softening at some bonding parts within the wire bundle is an indication of a high local temperature rise at strand interfaces.

Design and Demonstration of a Double-pancake Coil for SMES using MgB2 Multi-strand cable

MgB2 round wires are now commercially available with applicable critical current density in magnetic fields up to 5 T. One of the promising applications using MgB2 is a superconducting magnetic energy storage (SMES) coil. In our project, multi-strand cables with 600 A nominal current are designed for double-pancake (DP) coils with 400 mm inner diameter. The coil production processes in our project are wind-and-react (W&R) and react-and-wind (R&W) methods, in which a Rutherford-type cable consisting of eight (W&R) or ten wires (R&W) with specific twist pitch is reacted and then used to wind the DP coils, to investigate the suitable manufacturing process for MgB2 coils. The final goal is to fabricate five-stacked DP coils, made up of four DP coils by the R&W method and one DP by the W&R method with a total number of 512 turns, forming a 30 kJ SMES coil and to demonstrate compensation of voltage fluctuation on the BUS line of 48 V DC in a micro grid consisting of renewable energy source and liquid hydrogen supply system in our project. The first DP coils made by the two manufacturing processes are constructed and tested with regard to their properties such as critical current density in liquid helium to keep uniform temperature distribution throughout the coils.

Quench Level of the HL-LHC Nb3Sn IR Quadrupoles

The scope of the Large Hadron Collider Hi-Lumi Project at CERN includes the installation of several superconducting magnets wound with Nb 3 Sn Rutherford cables. The quench level of these magnets (i.e. the maximum energy that a cable can tolerate without quenching) is a key value required to set magnet protection from beam losses, and is expected to be significantly different from the computed and measured levels of the LHC NbTi magnets. In this work, we applied a one-dimensional numerical model of multi-strand Rutherford cables to simulate the electro-thermal instabilities caused by the heat released by the particle beam losses. Two models have been applied, one based on the analysis of the single strand, and the other accounting for all the strands in the multi-strand cable. The results of these two models are compared to analyze the effects of heat and current redistribution during quench. A comparison between the quench energy values obtained for the Nb 3 Sn conductor in the working conditions of the LHC Hi-Lumi inner triplet low-β quadrupole (MQXF) and those of the NbTi Rutherford cable of the LHC main quadrupole magnet (MQ) is presented.

Measurement of contact resistance for copper and aluminium conductors

During manufacturing of multi-strand cables the conductors are subjected to twisting and pressing which result in a creation of contact regions between individual wires. The resistivity of such contact regions differs from the resistivity of copper or aluminium. In this paper the resistivity is established by comparing measurements of resistivity with simulations using a finite element method. The non-homogeneity of the contact imprint has been accounted for and the presented results show the dependence of the contact resistance on several parameters, including compression force, imprint depth, intersecting angle and stranding pitch.

Analysis and Optimization of the Efficiency of Induction Heating Applications With Litz-Wire Planar and Solenoidal Coils

Optimization of the efficiency of an induction heating application is essential in order to improve both reliability and performance. For this purpose, multistranded cables with litz structure are often used in induction heating applications. This paper presents an analysis and optimization of the efficiency of induction heating systems focusing on the optimal copper volume of the winding with respect to different constraints. The analysis is based on the concept of a one-strand one-turn coil, which captures the dissipative effects of an induction heating system and reduces the number of variables of the analysis. An expression for the efficiency of the induction heating system is derived. It is found that, with the geometry and the other parameters of the system fixed, efficiency depends on the copper volume of the windings. In order to use this result to optimize the efficiency of an application, volume restrictions, the packing factor and the window utilization factor are also considered. The optimum frequency for an induction heating system is also studied in this study. An experimental verification for both planar and solenoidal cases is also presented.

Analysis of Beam-Induced Quenches of the LHC Cables With a Multi-Strand Model

In this paper we discuss results of a one-dimensional numerical model to simulate electrical and thermal transients in the superconducting cables for the LHC machine, with specific reference to the analysis of quench due to the heat released by beam losses. Two models have been developed, one based on the analysis of the behavior of a single strand, whereas the other accounts for all the strands in the multi-strand cable. As a first step the stability margin is computed considering the single strand subjected to a variable magnetic field and heat deposit along its length. The impact of the field non-uniformity is assessed by comparison with computations performed assuming a uniform field in the cable cross section. The results of this model are compared to those obtained with the multi-strand model. The numerical results are discussed in terms of current and heat redistribution between strands, and stability margin of the cable.

Accelerator-Quality HTS Dipole Magnet Demonstrator Designs for the EuCARD-2 5-T 40-mm Clear Aperture Magnet

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The Enhanced European Coordination for Accelerator Research and Development (EuCARD-2) Work Package 10 is a collaborative push to take high-temperature superconductor (HTS) materials into an accelerator-quality demonstrator magnet. The demonstrator will produce 5 T stand alone and between 17 and 20 T when inserted into the 100-mm aperture of a Fresca-2 high-field outsert magnet. The HTS magnet will demonstrate the field strength and the field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using a multistrand Roebel cable that develops a stand-alone field of 5 T in a 40-mm clear aperture and discusses the challenges associated with a good field quality using this type of material. A selection of magnet designs is presented as the result of the first phase of development.

Retraction Note to: Evaluation of coracoclavicular stabilization of acute acromioclavicular joint dislocation with multistrand titanium cables.

Purpose The aim of this study was to evaluate the outcome of surgical treatment of acute acromioclavicular (AC) joint dislocation with multistrand titanium cables for coracoclavicular (CC) stabilization.

Bakeout Effects on Dynamic Response of Spaceflight Cables

Spaceflight cables are investigated to determine the effect of bakeout on their dynamic response, including resonant frequencies and damping ratios. The addition of cable harnesses to spacecraft structures can affect the dynamic response of the entire structure, especially for lightweight structures with high cable mass ratios. Bakeout, a heat and vacuum treatment that spaceflight components must undergo, may change the dynamic stiffness of flight cables and thus the dynamics of the cabled host structure. Bakeout effects are examined by experimentally identifying natural frequencies and damping values for spaceflight cables before and after the bakeout process. After bakeout, the first natural frequency decreases by an average of 14% for all single-strand cables and by 24% for multistrand cables. The second natural frequency decreases by 8 to 17% for all cables. Bakeout also increases the damping percentage for single and multistrand cables. These results show that bakeout affects the dynamic response of spaceflight cables significantly and should be taken into account when using cable data for design purposes.

진동법을 이용한 사장교의 시공 중 장력 평가

When a cable-stayed bridge is under construction, the cable tension that changes according to the construction phase is the index indicating the proper construction management. In this study, the vibration method using the least-square estimation has been implemented to monitor changing tensions of two multi-strand cables of a cable-stayed bridge under construction. The test bridge is Hwamyung Bridge in Korea with a prestressed concrete box girder. The field tests are executed during the second tensioning stage just after the installation of the key segment. The tensions of two cables are measured before and after the tensioning and 5 days later (i.e., after finishing the tensioning of all cables). The accuracy of the estimated tensions by the vibration method has been improved by employing proper effective lengths of the cables. The measured tensions are compared with the result of the lift-off tests and design tensions. The vibration method shows very good performance in monitoring the changing tensions according to the construction phase with minimal error.