Dorin Luca - Academia.edu (original) (raw)

Papers by Dorin Luca

Simulation by FEM of sheet metal electromagnetic forming processes

Proceedings of SPIE, Jan 5, 2009

The electromagnetic forming is a process to manufacture a part from sheet metal. The final shape ... more The electromagnetic forming is a process to manufacture a part from sheet metal. The final shape of the part depends on the geometry of the dies, the material behaviour of the workpiece and the process parameters. This paper describes magnetic field transient analysis into electromagnetic forming devices using the finite element method (FEM). The electromagnetic force which causes plastic deformation

MATEC web of conferences, 2018

Extrusion is the plastic deformation process that allows for the highest degree of complexity pro... more Extrusion is the plastic deformation process that allows for the highest degree of complexity profiles to be obtained. This paper presents the simulation of a cold forward extrusion process using the finite element method. The results obtained show the stresses, strains and temperatures during the plastic deformation of the material, as well as the stresses and strains in the punch and die. The analysis of the results obtained for different geometric dimensions of the working tools allowed the optimization of the studied extrusion process. In order to validate the finite element model, experiments were carried out with the data acquisition from the real process, which allowed the appreciation that numerical and experimental data are found in a good agreement.

Journal of Manufacturing and Materials Processing

Electromagnetic forming is applied to form metal sheet parts from both non-ferrous and ferrous ma... more Electromagnetic forming is applied to form metal sheet parts from both non-ferrous and ferrous materials. In this paper, the electromagnetic forming behavior of aluminum alloy, copper and steel sheets was investigated through experiments. The disk-shaped specimens were electromagnetically free bulged with increasing deformation energies and parts with different deformation depths were obtained. The deformation was done with and without clamping the movement of the specimens’ edges. The specimens were printed with a mesh of diametrical lines and concentric circles with a predetermined pitch. The mesh served to determine the displacements in the mesh nodes after the deformation of the specimens, with which the axial, radial and circumferential strains were then calculated. The experimental data obtained was subjected to statistical correlation and regression analyses, and the mathematical models for the three main strains in each material were established. The strains of AlMn0.5Mg0.5 ...

IOP conference series, Nov 29, 2018

Everyday, biomaterials are becoming more widespread in the medical field and also in the metallur... more Everyday, biomaterials are becoming more widespread in the medical field and also in the metallurgical, aerospace, and even automotive industries. Mg-based biodegradable biomaterials are increasingly being studied and improved for their use in the medical field, even if Mg has a low corrosion resistance and not only can be alloyed to increase its strength and biocompatibility. The most commonly used and known elements with which Mg can be: Ca, Zn, Zr, Gd, Y, Si, Mn, etc. The purpose of this paper is to investigate the properties of Mg-2Ca-5Y alloy in order if it is suitable to use for use in medical applications. Surface morphology was characterized by electronic scanning microscopy (SEM) with EDAX, optical microscopy and X-ray diffraction (XRD). Following the XRD analysis, it was observed that certain specific compounds were formed: Mg 2 Ca, MgY, Mg 24 Y 5 having the main structural hexagonal phase. Micro-indentation and scratch tests were also performed on the casted alloy. As a final conclusion it is shown that the Mg-2Ca-5Y is recommended for medical applications.

MATEC web of conferences, 2017

One of the manufacturing processes that can be permanent improved is plastic deformation of metal... more One of the manufacturing processes that can be permanent improved is plastic deformation of metallic materials, as incorporating reserves on the manufacture of products with reduced material and energy consumptions. This paper presents finite element analysis for a closed die forging process, showing the stresses, strains and temperature into deformed part and stresses in the working tools. The analysis of obtained results for different flash dimensions of the working tools has enabled optimization of the forging process studied. To be able to validate the numerical results obtained, experimental tests were conducted. The compared data series show a good agreement between the numerical and experimental data.

A numerical modelling: Opened perspectives to increase the performance of the electromagnetic forming processes

International Journal of Numerical Modelling-electronic Networks Devices and Fields, Feb 9, 2011

SUMMARYElectromagnetic forming is achieved by a system consisting of an equipment, a tool (coil) ... more SUMMARYElectromagnetic forming is achieved by a system consisting of an equipment, a tool (coil) and a workpiece. The success of the deformation process depends on the equipment's parameters, the tool characteristics and the properties of the workpiece material. Finite element software FLUX2D was used for electromagnetic parameter simulation in the case of a device with flat spiral coil, used for the following operations: deep drawing, embossing, piercing, blanking etc. The simulations were made with a model previously validated by comparison with values experimentally measured for the discharge current and magnetic induction parameters. Copyright © 2011 John Wiley & Sons, Ltd.

Microstructural, magnetic and transport properties of manganites

Journal of Alloys and Compounds, Apr 1, 2014

ABSTRACT The most interesting and studied materials for practical applications of colossal magnet... more ABSTRACT The most interesting and studied materials for practical applications of colossal magnetorsistance effect are rare earth manganites with general formula RMnO3RMnO3 (where R is a rare/alkaline earth element). The coexisting of competing phases in manganites, such as metallic ferromagnetic, charge ordered, antiferromagnetic insulating and ferromagnetic insulating phases, determines an important change of magnetic and transport properties with the microstructure. In this paper, we report on the correlations between microstructural, magnetic and transport properties at temperatures ranging from 263 to 343 K of La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites synthesized by ceramic technology. The microstructure is studied using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) at Sr concentrations x=0.00,0.05,0.15x=0.00,0.05,0.15 and 0.20. SAXS and SANS data show the formation of magnetic nanodomains in the mosaic blocks, at temperatures higher than Curie temperature TCTC. SANS data reveal the shape and concentration of magnetic nanodomains, and their dependency on temperature. The La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites crystallize as cubic structure Pm3¯m (x=0.00x=0.00 and x=0.05x=0.05) or as rhombohedral structure R3¯c (x=0.15x=0.15 and x=0.20x=0.20). We found that transport phenomena at temperatures higher than TCTC are greatly influenced by nanodomains concentration and their shape. We show that about room temperature manganites with x=0.05x=0.05 and x=0.15x=0.15 have large intrinsic resistance maxima, generating an important magnetoresistance effect.

Journal of Engineering Sciences and Innovation

Proposed and accomplished finite element simulations in this paper started from the idea that mat... more Proposed and accomplished finite element simulations in this paper started from the idea that materials which are plastically deformed and those from which electromagnetic deformation devices are built can influence the development of transitory magnetic phenomenon during the working process. Workpieces from paramagnetic, diamagnetic and ferromagnetic materials and devices that contain metallic and non-metallic materials were taken into study. FLUX2D modelling and simulating software was used to achieve numerical values and graphical images for the main process parameters: magnetic induction and magnetic pressure (of deformation). A finite element model, previously validated through experiment, was used to perform the simulations in order to assure a high degree of accuracy for the presented results.

Numerical analysis of the manufacturing process of an extruded product

Journal of Applied Mechanical Engineering, Jan 4, 2018

Nanomaterials

The dimensional effect of electric charge storage with a density of up to 270 μF/g by the hydrate... more The dimensional effect of electric charge storage with a density of up to 270 μF/g by the hydrated ZrO2-nanoparticles system was determined. It was found that the place of localization of different charge carriers is the generalized heterophase boundary-nanoparticles surface. The supposed mechanism of the effect was investigated using the theory of dispersed systems, the band theory, and the theory of contact phenomena in semiconductors, which consists of the formation of localized electronic states in the nanoparticle material due to donor–acceptor interaction with the adsorption ionic atmosphere. The effect is relevant for modern nanoelectronics, microsystem technology, and printed electronics because it allows overcoming the basic physical restrictions on the size, temperature, and operation frequency of the device, caused by leakage currents.

The dimensional effect of the accumulation of an electric charge with a density of up to 270 μF/g... more The dimensional effect of the accumulation of an electric charge with a density of up to 270 μF/g by the system of compacted zirconium dioxide nanoparticles during exposure in an electric field (5000 V/m) under normal physical conditions is determined. Based on a qualitative complex analysis of the forms of appearance of the effect, it is shown that the place of localization of different charge carriers is the surface of nanoparticles. The supposed mechanism of this effect is considered using the theory of dispersed systems, the band theory, and the theory of contact phenomena in semiconductors. It was concluded that this mechanism is due to the phenomenon of localization of electron-type charge nanoparticles in the near-surface zone of the material in contact with the adsorption ion atmosphere. This effect is relevant for modern nanoelectronics, microsystem technology, and printed electronics.

The objective of this paper is to discuss the possibility of using electromagnetic tools to manuf... more The objective of this paper is to discuss the possibility of using electromagnetic tools to manufacture of religious objects from metal by plastic deformation. The paper analyzes a very agile manufacturing method based on only one tool (a die) that gives shape to the desired part and on the action of electromagnetic force that can be applied to manufactured metal objects such as open boxes, frames, religious objects, etc. that may have surfaces with embossed details. Electromagnetic forming is a method that allows a pressure impulse to be directed to a part of metal sheet in a highly controlled and reproducible manner. The electromagnetic tool (a coil) configuration controls the spatial distribution of the deforming pressure and the energy stored in a capacitor bank controls the impulse size transmitted to the material that will be deformed.

MATEC Web of Conferences, 2019

Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that th... more Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that the tool carrying the deformation force does not touch the workpiece. This paper presents research regarding the electromagnetic forming of Al 99.0 (EN AW-1200) sheet with coils, having different configurations. The purpose of the research was to find the flat spiral coil configuration that ensures maximum deformation of the workpiece. Flat spiral coils with different gaps between the coil and the workpiece, and coils with different number of windings were tested. The influence of these parameters was monitored on the maximum strain of the free bulged parts. The analysis of the results obtained for different configurations of the flat spiral coils allowed the selection of the significant parameters that influenced the electromagnetic forming process of the Al 99.0 flat workpiece, which aimed to elaborate the mathematical model and to optimize the investigated process.

IOP Conference Series: Materials Science and Engineering, 2018

Everyday, biomaterials are becoming more widespread in the medical field and also in the metallur... more Everyday, biomaterials are becoming more widespread in the medical field and also in the metallurgical, aerospace, and even automotive industries. Mg-based biodegradable biomaterials are increasingly being studied and improved for their use in the medical field, even if Mg has a low corrosion resistance and not only can be alloyed to increase its strength and biocompatibility. The most commonly used and known elements with which Mg can be: Ca, Zn, Zr, Gd, Y, Si, Mn, etc. The purpose of this paper is to investigate the properties of Mg-2Ca-5Y alloy in order if it is suitable to use for use in medical applications. Surface morphology was characterized by electronic scanning microscopy (SEM) with EDAX, optical microscopy and X-ray diffraction (XRD). Following the XRD analysis, it was observed that certain specific compounds were formed: Mg 2 Ca, MgY, Mg 24 Y 5 having the main structural hexagonal phase. Micro-indentation and scratch tests were also performed on the casted alloy. As a final conclusion it is shown that the Mg-2Ca-5Y is recommended for medical applications.

Environmental Engineering and Management Journal, 2016

Zirconia (ZrO2) as a ceramic biomaterial facilitates the osteoconductivity in new bone formation ... more Zirconia (ZrO2) as a ceramic biomaterial facilitates the osteoconductivity in new bone formation around implant. Surface characterization before and after electrochemical testing was performed used scanning electron microscopy (SEM). The electrochemical properties of the yttrium oxide stabilized zirconium oxide (YSZ) coated and uncoated MgCa sample with the open circuit potential at different immersion time in Ringer's solution were studied by electrochemical impedance spectroscopy (EIS). Equivalent circuits (ECs) were used to modeling EIS data, in order to characterize YSZ-coated and uncoated MgCa surface. The polarization resistance of the YSZ coated and uncoated MgCa decreases with the immersion time. However, after 2days immersion in Ringer's solution the corrosion resistance presenteded bigger value for the uncoated (360 Ω cm 2) than YSZ coated (140 Ω cm 2) MgCa alloy. The present study, showed that electrochemical determinations can be a usefull tool to characterize such alloys. Knowledge of in vitro corrosion behaviour of these alloys may lead to a better undersanding of any biologically adverse effects in vivo.

MATEC Web of Conferences, 2017

One of the manufacturing processes that can be permanent improved is plastic deformation of metal... more One of the manufacturing processes that can be permanent improved is plastic deformation of metallic materials, as incorporating reserves on the manufacture of products with reduced material and energy consumptions. This paper presents finite element analysis for a closed die forging process, showing the stresses, strains and temperature into deformed part and stresses in the working tools. The analysis of obtained results for different flash dimensions of the working tools has enabled optimization of the forging process studied. To be able to validate the numerical results obtained, experimental tests were conducted. The compared data series show a good agreement between the numerical and experimental data.

Increasing Wear Resistance of Power Steering Pump Cam Using Ni-Cr-Fe and Ni-Cr-Fe-B Coatings

Materials Science Forum, 2017

Thermal depositions are very wide spread in the industry of coating techniques. The materials use... more Thermal depositions are very wide spread in the industry of coating techniques. The materials used as coatings for several applications must have the ability to produce a stable, slow-growing surface coating, in order to provide good service behavior. This paper presents a method to increase the wear resistance of steering pump cam, strongly stressed having premature wear effects. The method that the authors use is atmospheric plasma deposition with Ni-Cr-Fe and Ni-Cr-B-Fe powders on steel substrate. It was investigated the morphology and physico-mechanical properties (scratch and micro-indentation analysis). Results showed a comparison between those two coatings with the metallic substrate. It has been found that the deposited coatings have an adherent, dense and uniform layer with a typically molten morphology. By increasing the coefficient of friction we can obtain higher wear resistance and recommend the optimum solution for further researches.

The International Journal of Advanced Manufacturing Technology, 2015

This paper summarizes the research work aimed to elaborate a new plating method for axisymmetric ... more This paper summarizes the research work aimed to elaborate a new plating method for axisymmetric metallic parts by precision cold forming on rotary swaging principle and, on this basis, to develop an environmentally friendly technology for net-shape plating. The new technology is intended to create parts with the basic structure made from cheap materials with high fatigue strength, on which, in areas where they require different characteristics (low friction coefficients, greater hardness, greater corrosion resistance, etc.), a layer of more expensive materials that provide these features is applied. At first, the new method of plating through rotary swaging was developed and the net-shape plating technology was preliminarily designed. Then, the experimental technology was analyzed and optimized employing process simulation by finite element method (FEM). A nonlinear finite element analysis (FEA) package, MSC.Marc/Mentat, was used. The full 3D FEM model established in this study eliminates some of the limitations encountered in the previous works using the real movement curve for dies and accurate boundary conditions. The model running tests indicate that the relative positioning between base workpiece and coating tube is of crucial importance in this application. Finally, practical experiments were carried out, the results been used for validation of the 3D simulation model, for physical-mechanical characterization of the joining between base part and coating layer and for technology design finalization. A good agreement between experiments and simulation was found. Also, the experiments indicate that the joint is more tightened when the inside workpiece has a yield strength greater than the outer workpiece.

Neural networks for parameters prediction of an electromagnetic forming process of FeP04 steel sheets

The International Journal of Advanced Manufacturing Technology, 2015

An electromagnetic forming process of FeP04 steel sheets is studied over a wide range of variatio... more An electromagnetic forming process of FeP04 steel sheets is studied over a wide range of variation of technological parameters aiming at finding optimal values providing maximum deformation of the part. The process parameters considered in this paper are deformed part diameter (d), thickness of specimen (t), distance coil–specimen (D), number of coil turns (N), capacitance of capacitor bank (C), and the charging voltage (V). Each specimen was freely deformed on a die of ring type through a unique combination of input parameters included in the study, and the maximum depth of the deformed parts center (h) was considered output parameter. Radial basis function neural networks are used for modeling the functional dependence between technological parameters and the resulting deformation of the material. Modeling results indicate an average mean square error around 4 % and a correlation between experimental data and neural model output exceeding 0.99. Sensitivity analysis reveals significant input parameters that decisively influence the output of the model. Simulation results are in good agreement with the experimental data, suggesting that neural networks can be considered a viable modeling alternative to existing approaches.

Finite element modeling and experiment for behavior estimation of AlMn0.5Mg0.5 sheet during electromagnetic forming

Transactions of Nonferrous Metals Society of China, 2015

Abstract The electromagnetic forming is a procedure of high-speed processing, which favors the in... more Abstract The electromagnetic forming is a procedure of high-speed processing, which favors the increase of the formability of some plastically deformed metals. In order to evaluate the capacity of some light metals, such as aluminum and its alloys, to be deformed through this procedure, it is useful to know the stress and strain state that occurs in the material during forming. In this work, the modeling of stresses and strains in electromagnetically deformed AlMn0.5Mg0.5 sheet was made. The modeling was achieved using the finite element method and it was verified through experimental tests. To determine the residual stresses, the X-ray diffraction method was used. The strains were established by measuring the displacements of the nodes in the network inscribed on the specimen by means of three coordinates measuring machine. A good agreement between the modeling results and experimental data was found.

Simulation by FEM of sheet metal electromagnetic forming processes

Proceedings of SPIE, Jan 5, 2009

The electromagnetic forming is a process to manufacture a part from sheet metal. The final shape ... more The electromagnetic forming is a process to manufacture a part from sheet metal. The final shape of the part depends on the geometry of the dies, the material behaviour of the workpiece and the process parameters. This paper describes magnetic field transient analysis into electromagnetic forming devices using the finite element method (FEM). The electromagnetic force which causes plastic deformation

MATEC web of conferences, 2018

Extrusion is the plastic deformation process that allows for the highest degree of complexity pro... more Extrusion is the plastic deformation process that allows for the highest degree of complexity profiles to be obtained. This paper presents the simulation of a cold forward extrusion process using the finite element method. The results obtained show the stresses, strains and temperatures during the plastic deformation of the material, as well as the stresses and strains in the punch and die. The analysis of the results obtained for different geometric dimensions of the working tools allowed the optimization of the studied extrusion process. In order to validate the finite element model, experiments were carried out with the data acquisition from the real process, which allowed the appreciation that numerical and experimental data are found in a good agreement.

Journal of Manufacturing and Materials Processing

Electromagnetic forming is applied to form metal sheet parts from both non-ferrous and ferrous ma... more Electromagnetic forming is applied to form metal sheet parts from both non-ferrous and ferrous materials. In this paper, the electromagnetic forming behavior of aluminum alloy, copper and steel sheets was investigated through experiments. The disk-shaped specimens were electromagnetically free bulged with increasing deformation energies and parts with different deformation depths were obtained. The deformation was done with and without clamping the movement of the specimens’ edges. The specimens were printed with a mesh of diametrical lines and concentric circles with a predetermined pitch. The mesh served to determine the displacements in the mesh nodes after the deformation of the specimens, with which the axial, radial and circumferential strains were then calculated. The experimental data obtained was subjected to statistical correlation and regression analyses, and the mathematical models for the three main strains in each material were established. The strains of AlMn0.5Mg0.5 ...

IOP conference series, Nov 29, 2018

Everyday, biomaterials are becoming more widespread in the medical field and also in the metallur... more Everyday, biomaterials are becoming more widespread in the medical field and also in the metallurgical, aerospace, and even automotive industries. Mg-based biodegradable biomaterials are increasingly being studied and improved for their use in the medical field, even if Mg has a low corrosion resistance and not only can be alloyed to increase its strength and biocompatibility. The most commonly used and known elements with which Mg can be: Ca, Zn, Zr, Gd, Y, Si, Mn, etc. The purpose of this paper is to investigate the properties of Mg-2Ca-5Y alloy in order if it is suitable to use for use in medical applications. Surface morphology was characterized by electronic scanning microscopy (SEM) with EDAX, optical microscopy and X-ray diffraction (XRD). Following the XRD analysis, it was observed that certain specific compounds were formed: Mg 2 Ca, MgY, Mg 24 Y 5 having the main structural hexagonal phase. Micro-indentation and scratch tests were also performed on the casted alloy. As a final conclusion it is shown that the Mg-2Ca-5Y is recommended for medical applications.

MATEC web of conferences, 2017

One of the manufacturing processes that can be permanent improved is plastic deformation of metal... more One of the manufacturing processes that can be permanent improved is plastic deformation of metallic materials, as incorporating reserves on the manufacture of products with reduced material and energy consumptions. This paper presents finite element analysis for a closed die forging process, showing the stresses, strains and temperature into deformed part and stresses in the working tools. The analysis of obtained results for different flash dimensions of the working tools has enabled optimization of the forging process studied. To be able to validate the numerical results obtained, experimental tests were conducted. The compared data series show a good agreement between the numerical and experimental data.

A numerical modelling: Opened perspectives to increase the performance of the electromagnetic forming processes

International Journal of Numerical Modelling-electronic Networks Devices and Fields, Feb 9, 2011

SUMMARYElectromagnetic forming is achieved by a system consisting of an equipment, a tool (coil) ... more SUMMARYElectromagnetic forming is achieved by a system consisting of an equipment, a tool (coil) and a workpiece. The success of the deformation process depends on the equipment's parameters, the tool characteristics and the properties of the workpiece material. Finite element software FLUX2D was used for electromagnetic parameter simulation in the case of a device with flat spiral coil, used for the following operations: deep drawing, embossing, piercing, blanking etc. The simulations were made with a model previously validated by comparison with values experimentally measured for the discharge current and magnetic induction parameters. Copyright © 2011 John Wiley & Sons, Ltd.

Microstructural, magnetic and transport properties of manganites

Journal of Alloys and Compounds, Apr 1, 2014

ABSTRACT The most interesting and studied materials for practical applications of colossal magnet... more ABSTRACT The most interesting and studied materials for practical applications of colossal magnetorsistance effect are rare earth manganites with general formula RMnO3RMnO3 (where R is a rare/alkaline earth element). The coexisting of competing phases in manganites, such as metallic ferromagnetic, charge ordered, antiferromagnetic insulating and ferromagnetic insulating phases, determines an important change of magnetic and transport properties with the microstructure. In this paper, we report on the correlations between microstructural, magnetic and transport properties at temperatures ranging from 263 to 343 K of La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites synthesized by ceramic technology. The microstructure is studied using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) at Sr concentrations x=0.00,0.05,0.15x=0.00,0.05,0.15 and 0.20. SAXS and SANS data show the formation of magnetic nanodomains in the mosaic blocks, at temperatures higher than Curie temperature TCTC. SANS data reveal the shape and concentration of magnetic nanodomains, and their dependency on temperature. The La0.5Pr0.2Pb0.3-xSrxMnO3La0.5Pr0.2Pb0.3-xSrxMnO3 manganites crystallize as cubic structure Pm3¯m (x=0.00x=0.00 and x=0.05x=0.05) or as rhombohedral structure R3¯c (x=0.15x=0.15 and x=0.20x=0.20). We found that transport phenomena at temperatures higher than TCTC are greatly influenced by nanodomains concentration and their shape. We show that about room temperature manganites with x=0.05x=0.05 and x=0.15x=0.15 have large intrinsic resistance maxima, generating an important magnetoresistance effect.

Journal of Engineering Sciences and Innovation

Proposed and accomplished finite element simulations in this paper started from the idea that mat... more Proposed and accomplished finite element simulations in this paper started from the idea that materials which are plastically deformed and those from which electromagnetic deformation devices are built can influence the development of transitory magnetic phenomenon during the working process. Workpieces from paramagnetic, diamagnetic and ferromagnetic materials and devices that contain metallic and non-metallic materials were taken into study. FLUX2D modelling and simulating software was used to achieve numerical values and graphical images for the main process parameters: magnetic induction and magnetic pressure (of deformation). A finite element model, previously validated through experiment, was used to perform the simulations in order to assure a high degree of accuracy for the presented results.

Numerical analysis of the manufacturing process of an extruded product

Journal of Applied Mechanical Engineering, Jan 4, 2018

Nanomaterials

The dimensional effect of electric charge storage with a density of up to 270 μF/g by the hydrate... more The dimensional effect of electric charge storage with a density of up to 270 μF/g by the hydrated ZrO2-nanoparticles system was determined. It was found that the place of localization of different charge carriers is the generalized heterophase boundary-nanoparticles surface. The supposed mechanism of the effect was investigated using the theory of dispersed systems, the band theory, and the theory of contact phenomena in semiconductors, which consists of the formation of localized electronic states in the nanoparticle material due to donor–acceptor interaction with the adsorption ionic atmosphere. The effect is relevant for modern nanoelectronics, microsystem technology, and printed electronics because it allows overcoming the basic physical restrictions on the size, temperature, and operation frequency of the device, caused by leakage currents.

The dimensional effect of the accumulation of an electric charge with a density of up to 270 μF/g... more The dimensional effect of the accumulation of an electric charge with a density of up to 270 μF/g by the system of compacted zirconium dioxide nanoparticles during exposure in an electric field (5000 V/m) under normal physical conditions is determined. Based on a qualitative complex analysis of the forms of appearance of the effect, it is shown that the place of localization of different charge carriers is the surface of nanoparticles. The supposed mechanism of this effect is considered using the theory of dispersed systems, the band theory, and the theory of contact phenomena in semiconductors. It was concluded that this mechanism is due to the phenomenon of localization of electron-type charge nanoparticles in the near-surface zone of the material in contact with the adsorption ion atmosphere. This effect is relevant for modern nanoelectronics, microsystem technology, and printed electronics.

The objective of this paper is to discuss the possibility of using electromagnetic tools to manuf... more The objective of this paper is to discuss the possibility of using electromagnetic tools to manufacture of religious objects from metal by plastic deformation. The paper analyzes a very agile manufacturing method based on only one tool (a die) that gives shape to the desired part and on the action of electromagnetic force that can be applied to manufactured metal objects such as open boxes, frames, religious objects, etc. that may have surfaces with embossed details. Electromagnetic forming is a method that allows a pressure impulse to be directed to a part of metal sheet in a highly controlled and reproducible manner. The electromagnetic tool (a coil) configuration controls the spatial distribution of the deforming pressure and the energy stored in a capacitor bank controls the impulse size transmitted to the material that will be deformed.

MATEC Web of Conferences, 2019

Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that th... more Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that the tool carrying the deformation force does not touch the workpiece. This paper presents research regarding the electromagnetic forming of Al 99.0 (EN AW-1200) sheet with coils, having different configurations. The purpose of the research was to find the flat spiral coil configuration that ensures maximum deformation of the workpiece. Flat spiral coils with different gaps between the coil and the workpiece, and coils with different number of windings were tested. The influence of these parameters was monitored on the maximum strain of the free bulged parts. The analysis of the results obtained for different configurations of the flat spiral coils allowed the selection of the significant parameters that influenced the electromagnetic forming process of the Al 99.0 flat workpiece, which aimed to elaborate the mathematical model and to optimize the investigated process.

IOP Conference Series: Materials Science and Engineering, 2018

Everyday, biomaterials are becoming more widespread in the medical field and also in the metallur... more Everyday, biomaterials are becoming more widespread in the medical field and also in the metallurgical, aerospace, and even automotive industries. Mg-based biodegradable biomaterials are increasingly being studied and improved for their use in the medical field, even if Mg has a low corrosion resistance and not only can be alloyed to increase its strength and biocompatibility. The most commonly used and known elements with which Mg can be: Ca, Zn, Zr, Gd, Y, Si, Mn, etc. The purpose of this paper is to investigate the properties of Mg-2Ca-5Y alloy in order if it is suitable to use for use in medical applications. Surface morphology was characterized by electronic scanning microscopy (SEM) with EDAX, optical microscopy and X-ray diffraction (XRD). Following the XRD analysis, it was observed that certain specific compounds were formed: Mg 2 Ca, MgY, Mg 24 Y 5 having the main structural hexagonal phase. Micro-indentation and scratch tests were also performed on the casted alloy. As a final conclusion it is shown that the Mg-2Ca-5Y is recommended for medical applications.

Environmental Engineering and Management Journal, 2016

Zirconia (ZrO2) as a ceramic biomaterial facilitates the osteoconductivity in new bone formation ... more Zirconia (ZrO2) as a ceramic biomaterial facilitates the osteoconductivity in new bone formation around implant. Surface characterization before and after electrochemical testing was performed used scanning electron microscopy (SEM). The electrochemical properties of the yttrium oxide stabilized zirconium oxide (YSZ) coated and uncoated MgCa sample with the open circuit potential at different immersion time in Ringer's solution were studied by electrochemical impedance spectroscopy (EIS). Equivalent circuits (ECs) were used to modeling EIS data, in order to characterize YSZ-coated and uncoated MgCa surface. The polarization resistance of the YSZ coated and uncoated MgCa decreases with the immersion time. However, after 2days immersion in Ringer's solution the corrosion resistance presenteded bigger value for the uncoated (360 Ω cm 2) than YSZ coated (140 Ω cm 2) MgCa alloy. The present study, showed that electrochemical determinations can be a usefull tool to characterize such alloys. Knowledge of in vitro corrosion behaviour of these alloys may lead to a better undersanding of any biologically adverse effects in vivo.

MATEC Web of Conferences, 2017

One of the manufacturing processes that can be permanent improved is plastic deformation of metal... more One of the manufacturing processes that can be permanent improved is plastic deformation of metallic materials, as incorporating reserves on the manufacture of products with reduced material and energy consumptions. This paper presents finite element analysis for a closed die forging process, showing the stresses, strains and temperature into deformed part and stresses in the working tools. The analysis of obtained results for different flash dimensions of the working tools has enabled optimization of the forging process studied. To be able to validate the numerical results obtained, experimental tests were conducted. The compared data series show a good agreement between the numerical and experimental data.

Increasing Wear Resistance of Power Steering Pump Cam Using Ni-Cr-Fe and Ni-Cr-Fe-B Coatings

Materials Science Forum, 2017

Thermal depositions are very wide spread in the industry of coating techniques. The materials use... more Thermal depositions are very wide spread in the industry of coating techniques. The materials used as coatings for several applications must have the ability to produce a stable, slow-growing surface coating, in order to provide good service behavior. This paper presents a method to increase the wear resistance of steering pump cam, strongly stressed having premature wear effects. The method that the authors use is atmospheric plasma deposition with Ni-Cr-Fe and Ni-Cr-B-Fe powders on steel substrate. It was investigated the morphology and physico-mechanical properties (scratch and micro-indentation analysis). Results showed a comparison between those two coatings with the metallic substrate. It has been found that the deposited coatings have an adherent, dense and uniform layer with a typically molten morphology. By increasing the coefficient of friction we can obtain higher wear resistance and recommend the optimum solution for further researches.

The International Journal of Advanced Manufacturing Technology, 2015

This paper summarizes the research work aimed to elaborate a new plating method for axisymmetric ... more This paper summarizes the research work aimed to elaborate a new plating method for axisymmetric metallic parts by precision cold forming on rotary swaging principle and, on this basis, to develop an environmentally friendly technology for net-shape plating. The new technology is intended to create parts with the basic structure made from cheap materials with high fatigue strength, on which, in areas where they require different characteristics (low friction coefficients, greater hardness, greater corrosion resistance, etc.), a layer of more expensive materials that provide these features is applied. At first, the new method of plating through rotary swaging was developed and the net-shape plating technology was preliminarily designed. Then, the experimental technology was analyzed and optimized employing process simulation by finite element method (FEM). A nonlinear finite element analysis (FEA) package, MSC.Marc/Mentat, was used. The full 3D FEM model established in this study eliminates some of the limitations encountered in the previous works using the real movement curve for dies and accurate boundary conditions. The model running tests indicate that the relative positioning between base workpiece and coating tube is of crucial importance in this application. Finally, practical experiments were carried out, the results been used for validation of the 3D simulation model, for physical-mechanical characterization of the joining between base part and coating layer and for technology design finalization. A good agreement between experiments and simulation was found. Also, the experiments indicate that the joint is more tightened when the inside workpiece has a yield strength greater than the outer workpiece.

Neural networks for parameters prediction of an electromagnetic forming process of FeP04 steel sheets

The International Journal of Advanced Manufacturing Technology, 2015

An electromagnetic forming process of FeP04 steel sheets is studied over a wide range of variatio... more An electromagnetic forming process of FeP04 steel sheets is studied over a wide range of variation of technological parameters aiming at finding optimal values providing maximum deformation of the part. The process parameters considered in this paper are deformed part diameter (d), thickness of specimen (t), distance coil–specimen (D), number of coil turns (N), capacitance of capacitor bank (C), and the charging voltage (V). Each specimen was freely deformed on a die of ring type through a unique combination of input parameters included in the study, and the maximum depth of the deformed parts center (h) was considered output parameter. Radial basis function neural networks are used for modeling the functional dependence between technological parameters and the resulting deformation of the material. Modeling results indicate an average mean square error around 4 % and a correlation between experimental data and neural model output exceeding 0.99. Sensitivity analysis reveals significant input parameters that decisively influence the output of the model. Simulation results are in good agreement with the experimental data, suggesting that neural networks can be considered a viable modeling alternative to existing approaches.

Finite element modeling and experiment for behavior estimation of AlMn0.5Mg0.5 sheet during electromagnetic forming

Transactions of Nonferrous Metals Society of China, 2015

Abstract The electromagnetic forming is a procedure of high-speed processing, which favors the in... more Abstract The electromagnetic forming is a procedure of high-speed processing, which favors the increase of the formability of some plastically deformed metals. In order to evaluate the capacity of some light metals, such as aluminum and its alloys, to be deformed through this procedure, it is useful to know the stress and strain state that occurs in the material during forming. In this work, the modeling of stresses and strains in electromagnetically deformed AlMn0.5Mg0.5 sheet was made. The modeling was achieved using the finite element method and it was verified through experimental tests. To determine the residual stresses, the X-ray diffraction method was used. The strains were established by measuring the displacements of the nodes in the network inscribed on the specimen by means of three coordinates measuring machine. A good agreement between the modeling results and experimental data was found.