Feasibility Evaluation of Cu-Nb Microcomposite Joints Formed by Magnetic Field Pressing for Pulsed Power Applications

In this work we have evaluated the feasibility of the magnetic field pressing technology for formation of Cu-Nb joints for further pulsed power applications. The electrical and mechanical properties of joints have been investigated. The structure of Cu-Nb conductors joints was investigated using optical and scanning electron microscopy. The mechanical characteristics have been evaluated using tensile tests. It has been determined that the maximum tensile strength of 350 MPa could be achieved, which is 30,4 % of a Cu-Nb wire strength. The applied pressing technology allowed minimizing the defects in the microcomposite structure due to solid-state joining process, however the resultant decrease of conductivity by 10 % influenced an increase of the Joule heating. After a 2 min 200 A current flow the difference of 54,4 °C between the conductor and the joint area was observed. It was concluded that the Cu-Nb joints formed by magnetic field pressing are applicable for pulsed magnet setups where non-destructive joints are required

Laser Treatment for Strengthening of Thin Sheet Steel

This paper presents the results of computer simulations and experimental studies, aiming to increase the mechanical strength of sheet metal parts manufactured from high-quality structural carbon steel by means of local laser processing. The effects of laser processing on the strength of steel sheet plates and their ability to resist bend load after laser treatment were studied. The results of bending experiments and computer simulations of elastoplastic deformation establish that local laser processing with surface melting can be used to increase the mechanical strength of structural elements made from thin sheet steel C22E and to decrease its deflection under similar workload, as an alternative to the application of complex geometric shapes, additional strengthening elements, or heat treatment

Computer-based measurement kit for welding deformations / Suvirinimo deformacijų matavimo kompiuterizuotas kompleksas

Nowadays, complex and potentially dangerous structures are usually welded. Manufacturers need to measure welding deformations and residual stresses. Tensometric stations are widely used for control and monitoring of such deformations and stresses. The article discusses a low-cost computer-aided measurement system. Santrauka Sudėtingų ir potencialiai pavojingų pramoninių konstrukcijų gamyboje vienas iš svarbių technologinių procesų tapo suvirinimas. Todėl gamyboje atsirado poreikis matuoti šių konstrukcijų suvirinimo ir liekamąsias deformacijas. Deformacijų kontrolei ir monitoringui plačiai taikomi kontaktiniai ir bekontakčiai būdai. Vienas iš seniai žinomų patikimų matavimų metodų yra tenzomentrinis matavimas naudojant tenzojutiklius ir tenzomatavimo stoteles. Šio darbo tikslas – sukonstruoti nebrangią, kompiuterizuotą tenzometrinių matavimų sistemą ir pritaikyti ją metalinių konstrukcijų suvirinimo deformacijoms matuoti. Reikšminiai žodžiai: tenzojutiklis; tenzometrinis kompiuterinis kompleksas; suvirinimo deformacijos

Measurement of electrical conductivity and resistivity of Cu-Nb18% microcomposite conductor and its welded joint

Systems generating strong magnetic fields are widely used in modern fundamental and applied research as well as in the most innovative industrial processes. These devices generate magnetic fields that reach 5–100 T and the conductors are subjected to a huge Lorentz force, so the conductor material must be extremely strong (UTS ≥ 700 MPa) and have a good specific electrical conductivity (IACS ≥ 60%). Since traditional conductors such as copper, aluminum, gold, and silver cannot withstand such loads, microcomposite materials have been developed that are characterized by such high strength and good specific electrical conductivity. This paper reviews the specific electrical conductivity and specific electrical resistance characteristics of conductor and factors affecting them, methods of measuring these electrical characteristics as well as properties of Cu-Nb18% microcomposite conductor. This paper also describes the methodology for measuring the specific electrical conductivity and specific electrical resistance of the Cu-Nb18% microcomposite conductor solid and with welded joint (welded by using butt welding). The comparison of application possibilities of used methodologies and obtained characteristics was carried out. Article in Lithuanian. Cu-Nb 18 % mikrokompozitinio laidininko ir jo virintinių jungčių elektrinio laidumo ir savitosios elektrinės varžos matavimo ypatumai Santrauka Šiuolaikiniuose fundamentiniuose, taikomuosiuose tyrimuose bei inovatyviausiuose industriniuose procesuose yra plačiai taikomi stiprių magnetinių laukų sistemos. Šie įrenginiai generuoja magnetinius laukus, kurie siekia 5–100 T, o laidininkai yra veikiami didžiulės Lorentzo jėgos, todėl laidininkų medžiaga turi būti itin tvirta (UTS ≥ 700 MPa) ir turėti gerą savitąjį elektrinį laidumą (IACS ≥ 60 %). Kadangi tradiciniai laidininkai tokie kaip varis, aliuminis, auksas, sidabras negali atlaikyti tokių apkrovų, buvo sukurtos mikrokompozitinės medžiagos, kurios pasižymi dideliu stipriu ir turi gerą savitąjį elektrinį laidumą. Šiame darbe apžvelgiamos laidininkų savitojo elektrinio laidumo bei savitosios elektrinės varžos charakteristikos, jiems įtaką darantys veiksniai, šių elektrinių charakteristikų matavimo metodikos, Cu-Nb 18 % mikrokompozitinio laidininko savybės. Taip pat šiame darbe yra aprašomos Cu-Nb 18 % mikrokompozitinio laidininko su virintine jungtimi (pagaminta taikant sandūrinį kontaktinį suvirinimą) ir vientiso Cu-Nb 18 % laidininko savitojo elektrinio laidumo ir savitosios elektrinės varžos matavimo metodikos, atliktas metodikų taikymo galimybių ir gautų charakteristikų palyginimas. Reikšminiai žodžiai: elektrinis laidumas, savitoji elektrinė varža, Cu-Nb mikrokompozitiniai laidininkai, virintinės jungtys, matavimai

Nikelio-aliuminio dangos ant aliuminio-magnio lydinio atsparumo dilimui ir korozijai tyrimas

The article examines the plasma sprayed 80Ni-20Al coatings on aluminum-magnesium (Mg ≈ 2.6‒3.6 %) alloy substrate, which before plasma spraying was cleaned using blasting with Al2O3 particles. The wear resistance and corrosion tests of sprayed coating and aluminum-magnesium alloy were performed. The volume loss, average central part of the cross-sectional area of wear track, wear rapidity, wear rate, wear resistance and corrosion current of coating and Al-Mg substrate were evaluated. The wear resistance and corrosion of nickel-aluminum coating and aluminum-magnesium substrate were compared at the work. Furthermore the wear tracks analysis of sprayed coating and substrate surface was carried out. Santrauka  Straipsnyje nagrinėjamos plazminiu būdu purkštos 80Ni-20Al dangos ant aliuminio-magnio (Mg ≈ 2,6‒3,6 %) lydinio substrato, kuris prieš padengiant buvo nuvalytas srautinant Al2O3 dalelėmis. Buvo atlikti purkštos dangos, aliuminio-magnio lydinio dilimo ir korozijos tyrimai. Nustatyti dangos ir Al-Mg substrato tūrio nuostoliai, vidutinis išdilusio takelio centrinės dalies skerspjūvio plotas, dilimo sparta, dilimo greitis, atsparumas dilimui ir korozijos srovė. Darbe buvo palygintas nikelio-aliuminio dangos ir aliuminio-magnio substrato atsparumas dilimui ir korozijai. Taip pat buvo atlikta užpurkštos dangos ir substrato dilimo takelių paviršiaus analizė. Reikšminiai žodžiai: plazminis purškimas, nikelio-aliuminio dangos, aliuminio-magnio lydinys, dilimas, elektrocheminė korozija

Simplified numerical simulation of pulsed magnets with a finite element method

The numerical simulation of magnetic field and mechanical deformation in pulsed magnets is described. ANSYS software was applied for numerical simulation. Due to construction symmetry the 3-D structure is simplified to 2-D structure and the numerical model of pulsed magnet was realized using the finite element method. The numerical model was done for two variants of multilayer reinforced pulsed magnet construction. The first one was wound with copper-niobium micro-composite wire, another - with traditional copper wire. Both magnets had similar pulsed magnetic field distribution and maximal value of magnetic flux density. Analyzing magnetic forces distribution and wire displacement it was found, that in spite of twice higher mechanical overloads took place in copper-niobium winding this magnet had the evidently better mechanical stability. Therefore numerical simulation results should be taken into account in further magnet optimization steps. 111.4, bibl. 11 (in English; summaries in English, Russian and Lithuanian)

NIKELIO-ALIUMINIO DANGOS ANT ALIUMINIO-MAGNIO LYDINIO ATSPARUMO DILIMUI IR KOROZIJAI TYRIMAS

The article examines the plasma sprayed 80Ni-20Al coatings on aluminum-magnesium (Mg ≈ 2.6‒3.6 %) alloy substrate, which before plasma spraying was cleaned using blasting with Al2O3 particles. The wear resistance and corrosion tests of sprayed coating and aluminum-magnesium alloy were performed. The volume loss, average central part of the cross-sectional area of wear track, wear rapidity, wear rate, wear resistance and corrosion current of coating and Al-Mg substrate were evaluated. The wear resistance and corrosion of nickel-aluminum coating and aluminum-magnesium substrate were compared at the work. Furthermore the wear tracks analysis of sprayed coating and substrate surface was carried out. Santrauka  Straipsnyje nagrinėjamos plazminiu būdu purkštos 80Ni-20Al dangos ant aliuminio-magnio (Mg ≈ 2,6‒3,6 %) lydinio substrato, kuris prieš padengiant buvo nuvalytas srautinant Al2O3 dalelėmis. Buvo atlikti purkštos dangos, aliuminio-magnio lydinio dilimo ir korozijos tyrimai. Nustatyti dangos ir Al-Mg substrato tūrio nuostoliai, vidutinis išdilusio takelio centrinės dalies skerspjūvio plotas, dilimo sparta, dilimo greitis, atsparumas dilimui ir korozijos srovė. Darbe buvo palygintas nikelio-aliuminio dangos ir aliuminio-magnio substrato atsparumas dilimui ir korozijai. Taip pat buvo atlikta užpurkštos dangos ir substrato dilimo takelių paviršiaus analizė. Reikšminiai žodžiai: plazminis purškimas, nikelio-aliuminio dangos, aliuminio-magnio lydinys, dilimas, elektrocheminė korozija

Geometry optimization of pulsed inductors

The optimization of pulsed power inductors' geometry is a difficult multi-dimensional task. On the one hand, an inductor could be destroyed because of the Joule overheating, on the other hand, it might be damaged by the Lorentz forces acting in its windings. The magnetic field pulse up to 50 T is the target while fields of this magnitude are the interest in many scientific applications. All factors mentioned are directly dependent on inductor's geometry, i.e. on the number of winding layers and windings per layer. Therefore, a detailed analysis of thermodynamic, electromagnetic and mechanical processes is inevitable and was carried out for different geometrical inductor configurations to reach the goal: a non-destructive inductor that can meet required magnetic field parameters. Direct calculation methods were used to create universal algorithms in MATLAB environment. The zone of inductor geometries, where stresses do not exceed the yield strength of materials, inductor is not overheated and generated magnetic field magnitude is in acceptable range, is given as a result which enables to manufacture new prototypes saving additional costs and time

Quality analysis of welded and soldered joints of Cu-Nb microcomposite wires

Quality analysis of welded and soldered joints of Cu-Nb microcomposite wires has been performed. Quality and mechanical characteristics of joints as ultimate tensile stress limit and elongation at break were measured with an universal testing machine and controlled visually using an optical microscope. Two wires joints were soldered with silver and copper solders and put into steel and copper sleeve respectively. Another two wires joints were soldered with silver solder and welded without any reinforcement. Joints soldered with the silver solder and steel sleeve have demonstrated the best mechanical characteristics: ultimate tensile stress limit of 650 MPa and elongation at break of 0.85 %. Joints soldered with the copper sleeve have no advantages comparing with the soldered butt joint. Ultimate tensile stress limit and elongation at break were in 300 MPa – 350 MPa and in 0.35 % – 0.45 % ranges respectively. Two welded joints had ultimate tensile stress limit of 470 MPa and elongation at break of 0.71 %. In all joints the microstructure of Nb filaments was destroyed and mechanical properties have been specified by mechanical strength of copper and sleeve materials only

Flash Welding of Microcomposite Wires for Pulsed Power Applications

This paper presents the experimental results of Cu-Nb wire joining upon applying flash welding technology. The present research is aimed at investigating the structure, electrical and mechanical properties of butt welding joints of Cu-Nb conductors, usable for coils of pulsed magnetic systems. The butt joint structure was found to be free of welding defects. The structure of the butt welded joint provides an insignificant increase in electrical resistance and sufficient ultimate strength and plasticity of the joint. The tensile strength of the welded sample reaches 630 MPa