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This issue of the RECENT® journal was edited with the support of: CONTENTS
Determining the Level of Logistics Automation Applicable in a Manufacturing Systems» Abstract This paper analyzes the economic conditions necessary for logistics automation of manufacturing systems to make effective and consistent with the company's financial strength. Based on the total purchase and operating costs of the logistics system, first thing to do is to determine the prerequisite that need to be fulfilled so automation would lead to lower costs than manual operation. To do this, define the degree of automation of the logistics system and write the formula between this and the total costs. By properly ordering the terms in this relationship, it will establish the necessary condition for introducing automation. If this condition is met, the level of automation will be directly correlated with the level of investment available for this.» Keywords automation, system manufacturing, logistics
A Comparative Study on Gravitational and Centrifugal Casting Solidification» Abstract It was studied the solidification of a part cast in both ways, centrifugal and gravitational. The study has been accomplished by computer simulation. Six casting variants were compared, three by centrifugal casting and three by gravity casting. The hot spot position, the solidification time, the solidification front movement, the temperature variation relative to time, the cooling and the solidification kinetics were analysed. The influence of the external cores and the mould coatings with protection layers it was studied too. » Keywords solidification, casting, centrifugal casting, solidification simulation, cast iron
Experimental Verification of a Software for Simulation of Centrifugal Casting Solidification» Abstract The software was developed to simulate the solidification of centrifugally castings with a rotationally symmetry. For the cast alloys that solidify in a temperature interval. The software uses a mathematical model with finite differences and cylindrical coordinates. It is shown an experimental verification of this software. The cooling curves obtained by simulation are compared with those obtained by experimental thermal analysis. The verification was carried out for the case of a cylindrical hollow part aluminium of cast alloy - silicon alloy. The experimental results are very close to those obtained by simulation. This confirms the validity of software. » Keywords solidification simulation, casting, thermal analysis, aluminium-silicon alloy
The Heat Treatment Parameters Analysis Using Two-Way ANOVA Method» Abstract Analysis of variance (ANOVA) is the method used to compare continuous measurements to determine if the measurements are sampled from the same or different distributions. It is an analytical tool used to determine the significance of factors on measurements by looking at the relationship between a quantitative "response variable" and a proposed explanatory "factor". This method is similar to the process of comparing the statistical difference between two samples, in that it invokes the concept of hypothesis testing. The two-way analysis of variance (Two-way ANOVA) is an extension to the one-way analysis of variance. The two-way ANOVA compares the mean differences between groups that have been split on two independent variables (called factors). A major importance represents the studies about the studies that analyze important technological parameters of heat treatment processes with Two-way ANOVA method. The paper presents an example of calculation for two-way analysis of variance repeated measures applied for the results of harness properties of an austempered ductile iron. The major objective of this research was to analyze (with Two-way ANOVA method) the influence of two independent variables on the dependent variable in the case of two alternatives of heat treatment. The independent variables are: the temperature at isothermal level, Tiz (in our case that has 2levels: Tiz= 300 and 400°C) and the maintained time at the isothermal level, tiz (that has four levels: tiz = 30; 60; 90 and 120 min). All calculations were made for two alternatives of austenizing temperatures of heat treatment: TA = 830 and 900 °C. By studying all the data presented in this paper following remarkable conclusions: that the austenizing temperature, TA= 900 °C is an important variable for our heat treatment while the austenizing temperature, TA=830 °C is not an important factor for the values of hardness properties of the studied ductile cast iron.» Keywords analysis of variance, two-way ANOVA, heat treatment, phase transformation, hardness
Functions of Heavy Bearing Cages (Part I)» Abstract In the context of global economy the development capacity and innovation of products is the key to modern society in order to ensure sustainable development. They are known and apply a significant number of research methods and design that are using both technical and economic criteria. They help to perpetuate and stimulate creative, so that in the design or development phase of existing products to ensure optimal correlation between quality and cost. Value engineering as a method of research and design is used herein to identify the functions of a bearing cage which is an important component in a bearing assembly. Identification of the cage functions lead to the identification of the optimization potential in terms of the production, costs and energy consumption involved in the entire life cycle of the cage (manufacturing, operation and post-operation). In the present paper the principal period of interest is the operating period because it has the most significant impact, if not the biggest regarding the energy consumption and costs. The analysis extends also to the period of manufacturing and post-use, periods with significant impact on consumption and costs. The study is part of a major ongoing research and it aims primarily to identify the right paths / directions of research in order to develop reliable and efficient new technological and constructive solution according to the concept of sustainable development and eco-design. » Keywords heavy bearing, cage, value engineering, functions, sustainable development, eco-design
Analysis of the Performance Criteria of Optoelectronic Systems» Abstract Analysing the results of the case study, I believe that the optimal choice optoelectronic systems is very important to determine and rank the performance criteria according to their contribution to fulfilling the mission and it is essential that these systems belong to the same category in terms of their performance. By synthesizing and presenting the fundamental concepts and processes that characterize the theme, we created an affordable material that facilitates the assimilation of the subject by students and others interested in this field. In a military environment constantly alert changing, it is desirable to be always one-step ahead of the enemy, is normal concern of specialists in all categories of weapons for knowledge, development and improvement of optoelectronic devices, so you can better use in battle. » Keywords performances, optoelectronic systems, engineering value method, weights
Study on Shrinkage Development inside an Al-Si Alloy Casting by Computer Solidification Simulation» Abstract We show that the position and shrinkage volume results given by software using casting solidification simulation doesn`t always correspond with the experimental results. This can be explained due to the simulation analysis the flow of liquid alloy inside casting (from casting-mould). For a better determination about position and shrinkage volume from casting, the numeric results and graphics given by software must be processed and interpreted by user at the end of simulation. In order to determine the position and shrinkage volume from casting one must analysed the time when feeding channel is interrupted, volume of liquid alloy from casting at that time and the position of the hot spot. We show this example to be verified as experimental in. In the end, we show the numeric results given by software and the steps to follow. » Keywords casting, shrinkage, casting solidification, solidification simulation, aluminium-silicon alloy
Comparison between Casting Solidification Simulation in Cylindrical Coordinates and in Cartesian Coordinates» Abstract Two software modules for solidification simulating of eutectic alloy castings were done at Transylvania University of Brasov. The first of them 3D-SIM EUT is based on finite difference mathematical model in Cartesian coordinates. The second SIM 2D-CIL-EUT, use a mathematical model in cylindrical coordinates. It is specialized for solidification simulation of casting with rotational symmetry. Simulation in cylindrical coordinates has the advantage that it allows the solidification simulation of spatial parts with rotational symmetry by 2D simulation, thus resulting a much shorter time of simulation. In addition, it allows the exact representation of the circular perimeter of parts with rotational symmetry, and a simpler division of system casting-mould in finite elements. After creating software in cylindrical coordinates, its operation and accuracy of the results were verified by several methods. In this paper, the verification was done by comparing to 3D-SIM EUT software in Cartesian coordinates that has been previously verified. The final conclusion of the study is that the software based on the mathematical model in cylindrical coordinates provides results consistent with previously conducted software in Cartesian coordinates. In exchange for the studied part, the simulation duration was 40 times smaller. » Keywords casting, solidification, simulation, cylindrical coordinates
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