Applied Mechanics and Materials Vols. 809-810

Abstract: Metal matrix composite layers were fabricated on AISI 304L substrate by diode laser surface alloying with direct injection of chromium carbide Cr₃C₂ powder into the molten-pool. The influence of laser alloying parameters on the quality of the alloyed layers were investigated. The alloyed layers were examined by optical metallography and scanning electron microscopy. Comparative erosion tests between the AISI 304L substrate and the alloyed layers have been performed following the ASTM G 76 standard test method. The uniform laser beam intensity profile of the laser used ensures to produce fully dense alloying layers with homogenous distribution of Cr₃C₂ particle throughout the matrix alloy. Distribution and dissolution of Cr₃C₂ particles are strongly dependent on the laser power level. The alloyed layers exhited noticeable increased erosion resistance in comparison to AISI 304L substrate for both 30° and 90° impact angles.

Abstract: Nowadays Additive Manufacturing, and in particular Selective Laser Melting (SLM ), is being used more and more. The SLM manufacturing process has been subjects to a lot of studies in order to improve the manufacturing parameters. In this paper are presented some researches on the internal structure of the manufactured parts with two layer thickness: 30[μm] and 50[μm]. The internal structure of parts manufactured on SLM machine is obtained as images with a microscope. On the images each grain of the internal structures is painted in a different color and grouped according to its shape. All data about grains are analyzed by the means of statistical methods. The two manufacturing strategies, 30[μm] and 50[μm] layer thickness, generate parts that have slightly different internal structures. Thus, from the point of views of internal structure and manufacturing time, the strategy with 50[μm] layer thickness can be used because it generates a lowering in manufacturing costs and increases the overall productivity.

Abstract: The FDM technology is an easy solution when someone need freedom of design but with a high precision of manufacturing and so, one can built conceptual models or molds, engineering models, manufacturing tools, and functional testing prototypes. The problem addressed in this paper is to identify and investigate the possibility of design and the achieving sustainability of a temporary hand prosthesis used for supporting and immobilizing a broken bone. The research tries to highlight some common and distinct aspects specific to FDM printing technology. One of the objectives of this paper is to use the FDM technology in order to achieve a modern version of the classics splints or of the orthopedic cast. The prototype models proposed can be made vertically on a 3D printer with small motherboard and are easy to wear, attractive to children through its colors and can be made with a manufacturing low price.

Abstract: The paper deals with the investigations of influence parameters of electro discharge machining (EDM) on the shape accuracy of external cylindrical surfaces machined by EDM process. A Sodick AD3L CNC electrode discharge machine was used to perform the EDM tests. In order to obtain the external cylindrical surfaces by RAM EDM copper cylindrical electrodes were used. Different machining setups and dielectric immersion modes were considered. In order to investigate the influence of the machining parameters on the investigated factors a factorial plan of experiments was considered. The preliminary experimental results highlighted the possibilities to obtain small diameter external surfaces of revolution on a ram electrical discharge machine.

Abstract: The electrochemical machining method ensures conditions for machining workpieces made of electroconductive materials, when the classical machining methods could not be applied or when their use is not able to offer a high efficiency of the machining process. The large diversity of the electrochemical machining procedures needs information about the specific work conditions and adequate establishing of the parameters which characterize the machining process and the factors able to exert influence on the parameters of technological interest. In order to design and materialize some electrochemical machining procedures, an analysis of the conditions specific to the work zone and of distinct subsystems specific to electrochemical equipment was developed. Taking into consideration the results of analysis, equipment for electrochemical machining was designed and materialized. One considered also some possibilities to develop subsequently scientific researches concerning aspects specific to the electrochemical machining process. Preliminary tests proved the possibilities of using the equipment and of its improving in the future.

Abstract: Wire electrical discharge machining is nowadays applied by using adequate specialized machine tools. A research problem could refer to a device for wire electrical discharge machining, adaptable on the current computer numerical controlled ram electrical discharge machines. The device could be able to be used in order to develop cutting processes in plate type workpieces. The wire electrical discharge machining process was examined and premises for developing a device for wire electrical discharge machining were formulated. These premises are used in order to develop an ideas diagram able to offer suggestions for the structure of the device. Distinct components necessary in the device structure were identified and taken into consideration, and three distinct versions of the device were defined.

Abstract: The paper presents the results of experimental research on the possibilities of micro-geometry modification of conductible and semiconductor surfaces, that gives them new functional properties. It emphasizes that surface micro-geometry modification occurs in practically all cases of the action by concentrated sources of energy, but a prescribed geometry can be reached only under strict conditions. The process of this geometry formation is a function of the physical and mechanical properties and the chemical composition of the processed material, the gradient of applied energy, the intensity of electric field applied in the interstice between the workpiece and the tool-electrode, the connection mode of the workpiece (as anode or as cathode) in the discharge circuit of the current impulse generator, etc. It highlights the fact that on the processed surface can be formed spherical shaped craters, round asperities or Taylor cone shaped asperities. Depending on the shape and the size of asperities, the active surface area, and, respectfully, the emission and absorption properties of elementary particles and light radiation are modified.

Abstract: Multi-objective optimization of laser cutting for simultaneous improvement of performance characteristics is of great practical importance. In this study a range of value (ROV)-based Taguchi methodology is proposed for multi-objective optimization of laser cutting, i.e. surface roughness, kerf width and burr height in CO₂ laser cutting of AISI 304 stainless steel. Laser cutting experiment was conducted based on Taguchi’s L₂₇ experimental design by varying the laser power, cutting speed, assist gas pressure and focus position at three levels. In the proposed methodology based on the experimental data signal to noise ratios as per Taguchi’s method were calculated for each experimental trial upon which decision matrix was defined. Subsequently, multi-criteria decision making problem was solved by the ROV method. The proposed ROV-based Taguchi methodology has relatively simple computational procedure and can be easily applied by engineers for solving different multi-objective optimization problems that occur in real manufacturing environment.

Abstract: In order to obtain small diameter external surfaces by ram electrical discharge machining from plate workpieces, tubular tool electrodes could be used. In such a case, one can appreciate that the obtained surface is a simple concatenation of cavities appeared as a consequence of electrical discharges developed between the asperities existing initially on the active surface of the tool electrode and surface to be machined of the workpiece. The analysis of the surface generation as a consequence of the electrical discharge machining process showed that due to the surface tensions, a leveling phenomenon could be taken into consideration. An experimental study of influence exerted by some input factors on the surface roughness parameter Ra was designed and achieved. One noticed that the increase of the pulse on time, pulse off time and peak current intensity determines an increase of the surface roughness parameter Ra. By mathematical processing of the experimental results, an empirical model type power function was determined. The examination of the machined surface by means of an optical microscope showed the existence of microcavities generated by the electrical discharge, while the material melted and re-solidified was placed as a bordure of the microcavities.

Abstract: In this paper were analyzed Tungsten electrode depositions using electro-spark deposition method, on stainless steel, used for hydraulic turbine vanes and blades of mixing blades for chemical industry, in order to achieve an improved wear resistance. This deposition method was chosen due to its relatively low cost, easy to achieve, and leads to obtaining thin layers with good adherence to the substrate, and with different thicknesses, depending on the number of deposited layers. The chosen electrode is an alpha character element and generates an increase of the mechanical properties at low and high temperatures for austenitic stainless steels. Tungsten does not modify the corrosion resistance for the stainless steels. The samples were analyzed on scanning electrons microscope (SEM) and also the chemical analysis (EDX) for distinguish the layer-support structure and the elements repartition on the surface and in line.