Papers by Keyword: Electrical Discharge

Abstract: Compacts of iron powders were prepared by medium-frequency electrical resistance sintering (MF-ERS) and electrical discharge consolidation (EDC). Structural and mechanical characterization was carried out in order to study the effect of the main processing parameters (current intensity and sintering time in MF-ERS and voltage and capacity in EDC). The compact properties resulted to be quite sensitive to the consolidation method and parameters. Porosities around 8% and microhardness of about 120 HV were reached. It is concluded that the MF-ERS process can be a best option for the consolidation of cemented carbide composites with composition WC-6wt.%Co. MF-ERS compacts of this composite show a very low porosity and reasonable uniform microstructure, preserving the original ultrafine grain size and an adequate hardness with a very quick processing cycle of the order of one second.

Abstract: Aluminum alloy die casting products are used for automotive LED lamp installation parts. The high aspect ratio shape used for large-volume heat problems needs thin rib parts. In the present study, we obtained basic data for the development of long axis type end mill tools for electrical discharge machining carbon material processing. At the same time, to evaluate the prototype development work, a special tool that enables high aspect ratio thin rib geometry processing was used. Longitudinal direction traverse cutting was done with a small diameter ball end mill tool in the carbon material for electrical discharge machining mold. The transfer accuracy and pick feed shape in the finished surface, the cutting resistance force, and the cutting edge shapes were examined to clarify the relationship between the cutting conditions set. Prototype development of the small-diameter end mill tool with a high rigidity, long axis was done using FEM numerical analysis method. The results showed that the small-diameter ball end mill tool with a tapered length axis in the prototype development had transfer accuracy of the cutting edge shape, and it was possible to reduce the finished surface roughness. Factors such as differences in tool shape are considered to greatly affect the tool rigidity.

Abstract: The basic behavior during underwater electrical discharge up to 10 kJ stored energy is investigated through both numerical analysis and optical-observation experiments. Since the authors have been investigating the use of underwater exploding phenomena for food processing and other applications, it is necessary to know the whole process which may affect the quality of the samples recovered. In the present investigation, the propagation of underwater shock wave was measured using a high-speed camera and compared with the numerically simulated results using LS-DYNA. Also, the motion of gas bubble, which is induced quite after the propagation of the shock wave, was measured and compared with the numerical simulation using the same code. The pressure of the bubble is not such high as the shock wave, but it is known that the impulse is not possible to be ignored due to its relatively long duration of the pressurization. Through a series of optical-observation experiments, it is confirmed that the numerical simulation is potentially possible to predict the whole phenomena for processing foods and other materials.

Abstract: The aim of this research is to determine the corrosion resistance on superficial layers laid-down through electrical sparking on the steel carbon OLC 45 samples, the used electrode being made from corrosion resistant material (Aluminum, Copper and Chromium). The superficial treatment through impulse electrical discharges is a procedure through which the proprieties of the metallic materials can be improved. The proprieties of the superficial layers obtained through this procedure are the same as the electrodes material being used or very close to this one, the properties resulting from micro alloying and the diffusion of the electrode material in the sample of steel. The experiments were done, for the superficial treatment through impulse electrical discharges, using Al, Cu and Cr electrodes. The corrosion speed was determinate through electrochemical corrosion. The corrosion potential and marking the polarization curves (linear and cyclic) was determined with an advanced electrochemical system type VOLTALAB 32. The acquisition and processing of experimental data was made with the help of the specialized software VOLTMASTER 2. The corrosion potential was determined by tracing the curves of linear polarization, recorded in sea water, using the Evans coordinates: E = f (log I). The corrosion process analysis was made also based on the cyclic polarization curves. The fine determining of the topography surfaces exposed to the action of the corrosive environment was made using the atomic force microscope (AFM). The support but also the sparking probes, has present the same type of corrosion; a general corrosion, which in the initial moments is represented by the appearance of corrosion dots. The superficial layers laid through Cr, Al and Cu electrodes sparking proves a improved corrosion resistance to see water compared to the base steel. Aluminium has the highest corrosion tendency while copper has the best protection.

Abstract: The experimental research aim was to analyze the corrosion resistance of superficial layers obtained by electrical sparking on the steel carbon samples. The electrodes used in these processes being made from corrosive resistance materials (coper and nickel). Processing by electric sparking occurs through electrode material erosion (anode) with a transfer by erosion products on the superficial workpiece. Processing of the treated surface begins with approximation of electrode by sample and at critical interval, it triggers electrical discharge through impulses. It is often continuous and ends at the electrodes contact. At the contact surface of the electrodes appear areas strongly heated causing electrical erosion of the electrodes (sample and electrode). The predominant transfer of anode material (electrode) to the cathode (the sample) ensures the formation superficial layer. After it the discharge was complete, at very small time interval, start removal of the Anode by cathode, action which ends with the interruption of electric circuit due to the transfer of material and the thermal changes from discharge area, in the superficial processing of metallic materials with electric sparks, the superficial layer of cathode it changes its structure and chemical composition. The samples being immersed 285 days in static sea water at the environments temperature. Corrosion resistance in seawater of superficial layers obtained with copper and nickel electrodes was determined by gravimetrical method. The samples covered with thin layers immersed in the corrosive agent (sea water) were analyzed through optical microscopy using QX3 Intel Play microscope and through atomic force microscopy. Experimental results were compared for both the surface of the initial sample material (OL 37) and the surface of the samples covered with Cu and Ni layers. One of the conclusions is: the superficial layer obtained by electrical sparking using cooper and nickel electrodes proves a improved corrosion resistance to see water compared to the base steel, specially for long term tries, when the corrosion speed is stabilizing remaining almost constant. The second main conclusion is: the investigations through atomic force microscopy made on the samples tested for long term corrosion, accentuate the compact and homogenous surfaces areas, which had not permitted the corrosive agent to interact with the base material.also, the wave-mode images present the discontinuities of the superficial laid layers, which represent a possible access way in for the corrosive agent to the samples material.

Abstract: The underwater shock wave has been studied in the various fields. The application of this method can be used for a molding machining, a welding and an embossing in the metal processing [. Moreover, this processing method can be used for a pulverizing, a softening, and a sterilization in the food processing. The aim of this research is to make the rice powder using by the underwater shock wave without generating of heat [. Although the underwater shock wave is generated using an explosive, the handling of the explosive is extremely accompanied by danger. Therefore, we developed the electric discharging device made to generate the underwater shock wave. It is easier to carry on the experiment using this device than the experiment of an explosive. We developed a pressure vessel for generating the underwater shock wave in various fields. The developed pressure vessel has been improved by our research group. The pressure vessel made to generate the shock wave is manufactured from a new concept, and the coaxial cable is used for wiring of the device.

Abstract: The article analyzed electrical discharge path in the air. The model was simplified and the path was approximated by line segments. Discharge path was calculated in iteration method. Single trunk and multiple branches were simulated separately. Experiment result presented high similarity with the shape of real electrical spark. Dynamic computation would take some load to processer, several important parameters were provided for realization.

Abstract: Preparation of superabrasive grinding wheels presents severe challenges due to the high hardness of abrasive grain. In this paper, electrical discharge dressing (EDD) technology with misted emulsion is applied to dressing bronze-bonded diamond wheels. Dressing experiments were carried out. The wheel profiles before and after dressing were measured using a Dektak 6M profilometer. The diamond wheel surface topographies before and after dressing were observed by three-dimension digital microscope. In addition, the performance of EDD’ed wheel was evaluated in practical grinding. It is shown that favorable surface topography can be obtained under suitable processing parameters and EDD misted emulsion with is feasible for metal-bonded diamond grinding wheel.

Abstract: Capacitor bushings are one of the key components in power transformers. Although their price is a negligible part of the total price of the power transformer, their quality has a significant effect on performance and reliability of power transformers. In high voltage capacitor bushings, the intensity of voltage and electric field on bushing abacus is very high. This high intensity is also observed in flange parts. The amount of multi layer insulator among the electrodes or floating plates in capacitor bushing make equi-potential surfaces and reduction of electric field in these areas can greatly improve the capacitor bushing performance. In this paper, we investigate the reduction of field intensity and electrical tension and also improvement in voltage control by displacing floating plates which are in the form of aluminum foils stick to impregnated paper. To calculate the field intensity, we used the MAXWELL software using FEM (Finite element method). Using this new method of placing capacitor core its effect on voltage profile reduction and field electrical tension is shown. Over voltage and pollution effects are also investigate on power transformer bushings.

Abstract: The generation of plasmas and the initiation of electrical breakdown are realized by the phenomenon of electrical discharge which is provoked when we apply a sufficient electric field in a gas. Consequently the free charges are accelerated, new charged particles are created and others are destructed. This can be ranged in four phenomena: elastic collision (recombination), attachment, excitation and ionization. The aim of this paper is to study the basic phenomena in an electrical discharge in the case of Oxygen O₂. Monte Carlo Simulation is used to follow the random trajectory of free charges determining in each path many parameters of the discharge. To determinate electrical and physical parameters, we have used the sampling laws. The spatial distributions of space charges (electrons, positive and negative ions) are also obtained. The determination of electrical field depends on distributions of charged particles obtained by solving the Maxwell equations.