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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. Source


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. Source


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. Source

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