Science UPS PILOT ARM SRL

Dragomireşti, Romania

Science UPS PILOT ARM SRL

Dragomireşti, Romania
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Chereches T.,Science UPS PILOT ARM SRL | Lixandru P.,Science UPS PILOT ARM SRL | Dragnea D.,Science UPS PILOT ARM SRL | Chereches D.M.,Polytechnic University of Bucharest
IOP Conference Series: Materials Science and Engineering | Year: 2017

This paper is the result of the attempts of quantitative approach of some of the processes that are occurring in the selective fragmentation with high voltage pulses installation. It has been formulated a methodology which customizes the general methods for the issue of transient electric field in mixed environments. The electromagnetic processes inside the fragmentation installation, the initiation and formation of the discharge channels, the thermodynamic and mechanical effects in the process vessel are complex, transient and very quick. One of the underlying principles of the fragmentation process consists in the differentiated reaction of materials in an electric field. Generally in the process vessel there can be found together three types of materials: dielectrics, metal, electrolytes. The conductivity of dielectric materials is virtually zero. Metallic materials conduct very well through electronic conductivity. Electrolytes have a more modest conductivity since they conduct through electrochemical processes. The electrical current, in this case, is the movement of ions having sizes and the masses different from the electrons. Here, the electric current includes displacements of ions and molecules, collisions and chemical reactions. Part of the electrical field's energy is absorbed by the electrolyte in the form of mechanical and chemical energy. © Published under licence by IOP Publishing Ltd.


Chereches T.,Science UPS PILOT ARM SRL | Lixandru P.,Science UPS PILOT ARM SRL | Dragnea D.,Science UPS PILOT ARM SRL | Mazuru S.,UTM FIMCM
International Journal of Modern Manufacturing Technologies | Year: 2015

The authors present the results of the numerical simulations of the thermo mechanical processes taking place inside the coaxialplasmagun and at the interaction between high speed gas jet and the dust deposited on the surfaces of the space vehicles. The purpose of the study on the use of coaxialplasma gun to clean the dust from the surfaces space vehicles in spatial missions to Mars, was to elucidate some aspects of the system's energy efficiency, thermal and mechanical effects of high-speed jet upon intersecting bodies and efficiency of the dust cleaning operation on the surfaces of space vehicles under atmospheric conditions of Mars. Numerical simulation of mechanical and thermal processes at the forming of the jet in gun, the interaction of the jet with the rarefied atmosphere of Mars and during the dust cleaning operations was conducted on a 3D physical model with a symmetrical plan which schematize real processes. The most important schematization refers to the shape and position of the plasma layer and uniform distribution of Lorentz forces on the unloading layer. The analysis of the state and of the movement of gas launched by the coaxialplasma gun had in attention both, the status parameters p, q, T and ρ and the jet velocity v. The plasma gun launches very short pulse type jets, with the output speed of the order of thousands of meters per second at temperatures of about 10,000 K. The mechanical and thermal effects produced by the gas jet on the intersected surfaces, were analysed by numerical simulations. There were no observed negative effects, the stresses and the temperatures induced in the structure have very low values. In the case of an extended cleaning action it can be produced the erosion of the attacked areas due to the sand particles movement with high speed. Numerical simulations showed, besides satisfactory efficiency of the coaxialplasmagun in the operation of removing the dust on surfaces of the spatial vehicle in space mission to Mars, some disadvantages of using this system, in the head of the list being the complexity and very low energy efficiency. © International Journal of Modern Manufacturing Technologies.


Chereches T.,Science UPS PILOT ARM SRL | Lixandru P.,Science UPS PILOT ARM SRL | Mazuru S.,UTM FIMCM | Cosovschi P.,FABRICA de STICLA | Dragnea D.,Science UPS PILOT ARM SRL
Academic Journal of Manufacturing Engineering | Year: 2014

One of the various proceedings for material cold-work hardening is the smooth finishing by superficial plastic deformation with hard tools from metallic carbide or diamond. According to this procedure, the active workpiece faces are pressed with a tool, generally ball-shaped, which has a spatial compound movement. The contact between tool and workpiece, also in motion, is force/displacement controlled. This paper describes a numerical simulation for study of the such-like procedure, used for cast iron parts. An accurate physical model for technological process was stated. The attention was focused on the material elastic-plastic properties and on constitutive equations. The finite element discretization with more fine mesh in the superficial layers of the workpiece active faces was achieved. The LS-DYNA explicit dynamic code was used for solving and analyses. The numerical simulation was applied on workpieces of revolution, manufactured by contour turning. © 2014, Academic Association for Manufacturing Engineering. All rights reserved.


Chereches T.,Science UPS PILOT ARM SRL | Lixandru P.,Science UPS PILOT ARM SRL | Mazuru S.,UTM FIMCM | Cosovschi P.,FABRICA DE STICLA | Dragnea D.,Science UPS PILOT ARM SRL
Applied Mechanics and Materials | Year: 2014

One of the various proceedings for material cold-work hardening is the smooth finishing by superficial plastic deformation with hard tools from metallic carbide or diamond. According to this procedure, the active work-piece faces are pressed with a tool, generally ball-shaped, which has a spatial compound movement. The contact between tool and work-piece, also in motion, is force/displacement controlled. This paper describes a numerical simulation for study of the suchlike procedure, used in glass casting equipment manufacture. An accurate physical model for technological process was stated. The attention was focused on the material elastic-plastic properties and on constitutive equations. The accuracy of the material model formulation was proved, with acceptable results, and validated on the Brinell hardness test. Using the results of the same test, the material failure strain for stress state with the negative triaxiality was been increased. The finite element discretization with more fine mesh in the superficial layers of the work-piece active faces was achieved. The LS-DYNA explicit dynamic code was used for solving and analyses. The numerical simulation was applied on work-pieces of revolution, manufactured by contour turning. Some of the physical work-pieces were subjected to smooth finishing operation with a special device mounted on a turning machine at Polytechnic University of Bucharest. The results of the finite element simulation are presented in form of colored maps for stress and strain and timecurves. Finally, a critical interpretation on the performed numerical simulation and some conclusions are given. © (2014) Trans Tech Publications, Switzerland.


Dragnea D.,Science UPS PILOT ARM SRL | Lixandru P.,Science UPS PILOT ARM SRL | Chereches T.,Science UPS PILOT ARM SRL | Velicu S.,Polytechnic University of Bucharest
IOP Conference Series: Materials Science and Engineering | Year: 2016

In the process of severe plastic deformation in the ECAP dies, the frictional forces between the blank and the walls of the dies play a determinant role on forming technologies. Due to the great length of the workpiece subjected to forming (in die), high frictional forces are developing, which can lead to blocking the forming process or even to the cracking of the dies. Two sets of numerical simulations were carried out for two coefficients of friction = 0.08 and = 0.10. There were analysed the following elements comparatively: the structure of the deformed mesh of the finished piece; the effective plastic strain fields; the Von Misses effective stress fields; the actuation forces on the die punch. The results of the numerical simulations showed: uniform structure of slipped layers in central areas of the finished parts, obtained by the two processes; the effective plastic strain field is uniformly at the process with low friction Von Misses effective stresses were significantly lower at the numerical simulation for the process with low friction; the application forces occurring in the processes carried out in the ECAP die with low friction are significantly lower than those obtained in conventional ECAP die. © Published under licence by IOP Publishing Ltd.


Dragnea D.,Science UPS PILOT ARM SRL | Lixandru P.,Science UPS PILOT ARM SRL | Chereches T.,Science UPS PILOT ARM SRL | Velicu St.,Polytechnic University of Bucharest
IOP Conference Series: Materials Science and Engineering | Year: 2016

Interaction forces between the workpiece and the die appear during the cold forming process of metals in dies. Surface forces of high-intensity influence the mesh structure and internal structure of the finished piece by mechanical action. Frictional forces hinder the flow of the material in contact with the die walls, especially on surfaces of complex shape. Under certain conditions, the material can adhere to the wall of the die, leading to the blocking of the cold forming process. In order to highlight the influence of contact forces on cold forming processes in dies with complex surfaces there were used numerical simulation methods with finite elements. Numerical simulations of the process of axial cold forming in the die were carried out for analysis data acquisition necessary, in order to achieve HTD pulleys, for an ordinary range of friction coefficients. The analysis was directed to the gearing area of the HTD pulleys (head, flank and base of the tooth). The analysis highlighted the negative effects of friction forces on the shape and quality of the products and the need to use quality lubricants. Also, using the cold forming process they can be achieved substantial savings by redistribution of the material without removing it. © Published under licence by IOP Publishing Ltd.

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