Zur Bestimmung der Einflußbereiche bei Beeinflussungsuntersuchungen

This paper deals with the global basis of evaluation in different cases of electrical interference due to Austrian standards. Conditions are explained to harmonize standards in case of inductive interference, electrostatic influence and resistive interference in connection to probability factors. Relevant notions as zone of exposure, area of protection and restricted area are explained to create optimal strategies of planning.     

High‐performance Cu/Al laminated composites fabricated by horizontal twin‐roll casting

Horizontal twin‐roll casting technology was successfully introduced to produce high‐performance copper/aluminum (Cu/Al) laminated composites. The interface morphology, electrical properties and peeling strength after different annealing and cold rolling processes were investigated and contrasted with Cu/Al clad plates fabricated by conventional methods. The results show that sound metallurgical bonding between the copper and aluminum matrix can be attained after the horizontal twin‐roll casting processes and Al₂Cu is the only intermetallics at the interfacial region, the thickness of interfacial interlayer is about 0.7 μm. The peeling strength is 31.4 N/mm and can be further increased to 37.1 N/mm after annealing at 250 °C. However, higher temperature like 400 °C will cause the excessive growth of intermetallics so that peeling strength sharply decreases to 9.2 N/mm. Electrical conductivity of the clad plate is 51 MS/m. At the same electrical current intensity, the temperature‐rise of the composite plate is between the pure copper plate and the aluminum plate, and closer to the copper plate. All of the properties are outstanding than that of Cu/Al clad plate fabricated by conventional methods.     

Optimization of Dielectric Properties of Suspension Plasma Sprayed Hydroxyapatite Coatings

Conventional plasma torch was adapted to spray very fine Ca₅ (PO₄)₃OH (hydroxyapatite, HA) precursors having sizes ranging from a few hundreds of nanometers to a few micrometers. The powders were put in suspension with distilled water and antidispersive agent. A home made suspension feeder, including two peristaltic pumps, delivered the suspension into atomizer and therefrom injected into plasma jet. The suspension flow rate was electronically controlled. The resulting coatings had the thickness of a few tenths of μm. The electrical properties of the coatings including breakdown voltage and loss factor of suspension sprayed hydroxyapatite coatings sprayed onto aluminium substrates were also tested. The influence of such experimental factors as power input to plasma, pressure of atomizing gas, spray distance and suspension feed rate on the responses being the electrical properties was investigated using a 2⁴ design of experiments (DOE). The mathematical models relating the responses with the factors were created and the significant factors were selected.     

Charakterisierung des Ermüdungsverhaltens hochbeanspruchter Eisenbahnvollräder für den Hochgeschwindigkeitspersonenverkehr bei betriebsrelevanten Temperaturen

Fatigue assessment of highly loaded railway monobloc‐wheels for application in high‐speed passenger‐traffic trains under thermal service conditions Railway wheel steels rank among the most loaded components of railway vehicles. Whereas increasing driving speeds increase in particular the cyclic mechanical loading, increasing acceleration and braking torques lead to enormous thermal loads. Hence, a detailed knowledge about the microstructure‐related characterisation of the fatigue behaviour of railway wheel steels under thermal service conditions is the fundamental precondition for a save and economic operation of railway systems. Current investigations concentrate on the fatigue behaviour of actual UIC‐conform high‐speed passenger‐traffic railway wheel steels, which were provided in industrial relevant heat treatment conditions. Microstructural gradients are a consequence of the industrial heat treatment and the size of the component. Specimens were machined from defined depth positions of the wheel rim from original monobloc wheels. Plastic strain amplitude, change in temperature and change in electrical resistance measurement techniques were used to characterise the fatigue behaviour in detail. The specimen position and therefore the local microstructure influence the fatigue behaviour in a characteristic manner.     

Effect of thickness and chemical composition on thermal resistance of steel dilatometric specimens under heating-cooling cycles by Joule heating

The effect of thickness and chemical composition on the electrical power and thermal resistance of dilatometric specimens heated by Joule heating are analyzed in different steels, using stepped tests of constant temperature and electrical current. In the stepped constant temperature tests, the electric current necessary to maintain the target temperature in a specific time is measured, while in the electric current tests the electrical current is maintained until the maximum temperature stabilizes. The results show that the electrical power behaves linearly with the thickness associated with the transfer area, while the thermal resistance behaves potentially; both values depend on the chemical composition due to electrical resistivity. The steels with a higher concentration of alloying elements have a better response to Joule heating. However, thickness is the parameter that most influences electrical power due to changes in transfer area and electrical current density, as well as in the mass of the specimen to be heated. Finally, based on the results obtained, predictions are realized for the design of thicker specimens, maintaining the observed behavior; i. e., as the thickness of the specimen increases, the increase in electrical power and thermal resistance is maintained.     

Deposition of biomimetic biocompatible oxides on metallic glass surface by electro-discharge coating process

Bulk metallic glass demonstrates superior mechanical properties and excellent bio-mechanical stability compared to routinely used biomaterials like titanium, cobalt-chromium, stainless steel, et cetera. However, the metallic glass surface do not easily adhere to the leaving tissues due to native bio-inert oxide layer, which have poor wear resistance and low hardness. In this current study an innovative method for surface coating of bulk metallic glass by mixing hydroxyapatite powder during electro-discharge machining has been employed. A biomimetic nano-porous bio-ceramic layer of oxides and carbides was deposited on metallic glass surface. The modified surface integrity and composition were investigated by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction characterization techniques. The characterization results confirmed the formation of a natural bone-like nano-porous surface topography on the metallic glass surface using a novel hydroxyapatite-mixed electro-discharge coating process. In addition, a favourable surface chemistry in the form of bioceramic carbides (zirconium carbide, titanium carbide) and zirconium oxide layers, was achieved.     

Laser welding of copper‐niobium microcomposite wires for pulsed power applications

The laser welding of copper‐niobium microcomposite wires was investigated. It was determined that the joint structure does not have welding defects, while microscopic examination of the joint cross‐section showed that the microstructure of the autogenous weld consists mainly of a copper‐based solid solution strengthened by niobium‐rich precipitations. The weld obtained with use of filler material consists of two distinct zones, which are formed due to melting of filler wire and microcomposite wire. This structure of the joint provides an insignificant increase in electrical resistance and sufficient ultimate strength and plasticity of the joint. The tensile strength of the sample welded without filler material reaches 335 MPa, but such welded joints are very brittle due to very low ductility. However, an autogenous laser welding joint has about 1.6 times better ductility, and the tensile strength of the joint depends on the applied filler material and is equal to the tensile strength of this material.     

Neural Method Alloys Identification by the Microplasma Oxidation Process in the Electrolyte Solutions

A new method for the aluminium and magnesium alloys identification is described in the paper. The distinctive feature of the method is based on the measure of parameter current by the microplasma oxidation process of the alloys using neural network for its identification. Examples of alloy identification and estimation of recognition accuracy are given.