Advanced Materials Research Vol. 837

Abstract: Numerical Simulationis a Modern Method to Optimize Cold Plastic Deformation Processes in Order Toprovide Product Quality, Reduction of Time and Costs of Execution. One of Theimportant Problems of Numerical Simulation is the Mode of Characterizing Theplastic Behaviour of the Material which Undergoes Deformation. the Resultsobtained through Simulation are Closer to Real Ones as the Description Ofmaterial Behaviour of the Piece is Done as Accurately as Possible. Thesimulation Results Depend on the Stress-Strain Relationship which is Obtainedexperimentally by Compression Tests. the Paper Presents the Mode of Determiningthe Constitutive Equation Starting from the Results of the Compression Test.This Test was Used because it Allows Achieving High Strain and the Stressdistribution is Similar to other Corresponding Plastic Deformation Processes.

Abstract: In the paper a classical model of failures is considered in that successive failure-free times are supposed to have Gamma distributions and are followed by exponentially distributed times of repairs. It is assumed that parameters of these distributions, in general, change with time. Basing on information about the number of failures and failure-free times in a number of periods of the same duration in the past, three different methods of estimation unknown parameters of the model are proposed. Next, predictions of the most important reliability characteristics are found.

Abstract: This paper presents a method for determining the nature of the material (cool or sterile) running on high-capacity mining belt from basin of Oltenia. When an electromagnetic radiation that propagates in the air meets the separation surface with another environment suffers, among other things, the phenomenon of reflections (diffuse and specula). The intensity of reflected radiation depends on the optical surface properties of the encountered material. On this fact is based the possibility of identification of certain components of the mixture, if the optical properties are considerably different from other components. The method proposed in this paper is based on measuring the reflectance for different regions of the visible and near infrared spectra for samples of coal and sterile, dry and wet. The system for determining the nature of the excavated material mainly consists of an optical head (reflectance sensor) and an ultrasonic head (remote sensor). From experimental observations we see that the reflectance values of coal can be separated from those of sterile, which confirms the possibility of coal detection using the difference in reflectance. The limit of demarcation between reflectance of coal and different types of sterile is influenced by disturbing factors that occur at the plant operating detection under practical conditions such as: material humidity, the variability level of the material on the conveyor belt, the existence of a light background ambient. The method for determining the nature of material (coal or sterile) that circulates on high capacity belts creates real prerequisites of material excavated in conjunction with the possibility of taking quick and effective decisions in the distribution nodes from the coal careers. Key words: electromagnetic radiation, reflectance, coal, remote sensor, detection.

Abstract: The use of magnesium alloys in construction of different components of the mechanical systems (such: cars, aerospace vehicles, medical equipment etc.) is very efficient not only because it leads to reduction of the systems weight but also because it leads to reduction or elimination of the environment polluting and to reduction of the energy consumption. Generally, the main factors that influence the quality of the machined surfaces are as follows: cutting parameters, material properties, geometry of the tools, cooling liquids and lubricants, physical and mechanical properties of the subsurface layers etc. Among the above mentioned factors, cutting parameters are the factors that strongly influence the quality of the machined surfaces. The present paper analysis the results of the experimental investigation performed to determine the influence of cutting parameters (cutting speed, feed rate and cutting depth) on the surface quality machined by turning the AZ61 magnesium alloy. The main characteristics of the machined surface quality analyzed in experimental investigation were the surface roughness and hardness. The main conclusions resulted from the results analysis were as follows: the decrease of the feed rate led to surface roughness decrease and hardness increase; the increase of the cutting speed also led to an improved surface quality.

Abstract: In the machining of the magnesium and magnesium alloys, some difficulties are encountered during working process. Thus, in the case of turning operation, when phenomena like: splinter self-ignition and flank built-up occur during machining, special tools and coolants are required in order to diminish the effects of such phenomena. In the case of grinding operation of the magnesium and its alloys, other phenomena like: adhesion between the abrasive tools and processing materials can cause explosions and hence such operation must be conducted in special conditions. A solution that can be applied to avoid such phenomena and effects is represented by the utilization of the burnishing operation. In the present study, the influence of the burnishing process on the quality of the machined surfaces of parts made from AZ61 magnesium alloy was performed. The quality of the burnished surfaces was analyzed in terms of the roughness and hardness parameters, the parameters with the greatest influence on surfaces roughness and hardness being the burnishing feed, burnishing speed and burnishing pressure

Abstract: Physical phenomena in engineering are studied using several types of research instruments. In the class of the theoretical instruments may be considered the analytic and numeric models and the category of the practical approaches includes the experimental studies. However, complex phenomena require information resulted from several types of studies. The integration of the information may be done using original software applications which offer speed, accuracy and flexibility in the context of that certain project. If the research plan considers right from the beginning the integration of the results of different types of studies in a unique investigation methodology, the model of the phenomenon may be considered hybrid. The paper presents several research projects in engineering, the project dedicated to the strains and stresses in the cylinder block is the most complex one and it required several studies of different types, together with original software employed to integrate the data. It may be considered a relevant example of hybrid model. To conclude, the analysis of the phenomenon to be studied must lead to a certain high overview which offers the grounds of a holistic approach in the design of the research plan. Thus, there must be identified all the sources of experimental data, using various experimental techniques, even the redundant information being useful for cross-checking purposes.

Abstract: In this analysis, the variable configuration requires a variable distribution. This takes account of the areas offered by the valves and resistance gazodynamic coefficients. All at once the law of efficiency variation describes the variation of the power law. Cycle behavior was analyzed for the following values of the pressure drop coefficient on admission: 5%, 10%, 20% and 40%. For the calculations is necessary to determine the dimensionless heat developed by combustion. I used the following values: for the pressure drop coefficient on admission I use ψ_a=10 % and for the share of gazodynamic on the suction route conductance in total conductance I use .With this configuration imposed and with (dimensionless heat developed by combustion) resulted: (mean indicated pressure cycle) ; η_v = 0,876 (cylinder filling coefficient) ; α = 1,515 (excess air coefficient) and η_i = 0,499 (indicated cycle efficiency) ; (dimensionless indicated power ); (dimensionless heat taken combustion gas) ; (dimensionless heat taken environment). After numerical analysis result a maximum efficiency with relatively low dissipation.

Abstract: In recent years, due to the hard competitiveness through globalization most manufacturing companies have focused on manufacturing higher value added products with low production costs. So, it is inevitable to apply the advanced technology to carry out it in effective and efficient way. Monitoring and control of machining processes are becoming increasingly important for keeping a consistent quality of machined parts. The paper presents in-process sensing and control techniques with applying information science for the next generation of quality control that eliminates the need for expensive post-process inspection. In this research, a machining process of machine tool is considered in terms of a quality oriented control. The self-optimizing control is proposed for enabling intelligent process monitoring and control which can detect the cutting conditions and status of machining operations. To prove the proposed self-optimizing control system, self-monitoring and self-adjusting, the machining process related to the tool condition such as tool wear was considered in this paper. The most crucial and determining factor to successful maximization of the manufacturing processes in any typical metal cutting process is tool wear. The evolutionary algorithm was developed to diagnose the tool wear. If the amount of tool wear is out of the allowed limit, the new cutting parameters should be generated and adjusted autonomously according to affecting the quality of the machined part through the tool wear.

Abstract: The paper set the differential equations of free vibration for straight helical rods, in a general matrix form, with which determine the pulsation equation as an algebraic equation of n degree. The coefficients of this equation contain geometrical and elastic characteristics including natural degree of torsion bar and also the boundary conditions at the ends. These coefficients provide important information about the machine-tools from the mechanical industry under the action of vibrations, during execution the processing operations on the industrial products.

Abstract: Helicoidal surfaces correspond to a cathegory of widely spread surfacesin the technical field. From the point of view of the manufacturing of helicoidal surfaces through the moving of a profile around the helix, the two elements defining such a surface can be distinguished: the profile and the helix. The numerical determination of the profile of the disc type tool drawn on an analytical method with a large number of points [1- (the number reaches even 1500 in some cases) implies a great effort so that the technician can verify the correctness of results, even in the present case when there is the possibility of the numerical determination through the resolution of the inverse problem of the frontal profile of the complex helicoidal surface. In order to facilitate this work and to give the possibility of introducing some new profiles in the projection system, some methods of grapho-analytical determination have been conceived to process the profiles of the complex helicoidal surfaces, as well as the profiles of the helicoidal surfaces for a given tool profile. This paper presents the graphic-analytical determination of the disc tool profile designed to dress the complex helicoidal surfaces. The methods referred to by using the possibilities provided by the programming environment AutoCAD and its development languages allow to determin numerically the profile of the disc-cutter with a high precision, above the precision level required in practice.