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Recent 23

Vol. 9 (2008), No. 2 (23) July 2008

The 23rd issue of RECENT journal was edited and multiplied with support of:

  • Romanian Association for Nonconventional Technologies

  • Transilvania University of Brasov, Romania

  • Brasov County Council (by Scientific Activities, Education, Culture, Cults Committee)


CONTENTS


  • Ionel BATOG

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COMPUTER AIDED VIBRATION ISOLATION OF SPIRAL ELEVATORS

Abstract. Pre-dimensioning the isolation support system of spiral elevators aims at determining a range of isolators which can allow equipment to function as intended and reduce the vibration transmitted to the support structure. Elastomeric isolators are chosen for most isolation schemes. The selection of proper isolators is based on the maximum load that must be supported, the number of mounts supporting the load, the frequency of the vibration. This is an iterative, time consuming task that includes a set of calculations based on working conditions of the vibratory system and construction of isolators (material, shape, make). The calculation assumptions and relationships that allow the selection of isolators are presented in the paper. On this basis, a computer software was developed in order to facilitate the task and save valuable time.

Keywords: spiral elevators, vibration isolation, computer aided design


  • Ioan CIOBANU, Aurel CRIŞAN, Sorin Ion MUNTEANU

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THE SOLID FRACTION EVOLUTION AT STEEL CASTINGS SOLIDIFICATION

Abstract. To create software for casting solidification simulation it is necessary to know the variation of the solidified alloy fraction in function of temperature. In the paper there are presented the equations used by authors to mathematical model this dependence in the case of unalloyed steel castings solidification. These equations were used by authors to create software designated to simulate the steel castings solidification. The software realized is based on a finite differences mathematical model.

Keywords: solidification, steel, modelling, simulation


  • Tzanko GEORGIEV, Vladimir NIKOLOV, Nikola ATANASOV

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THE ESTIMATION OF MASS MOMENT OF INERTIA ON AN EQUIPMENT - MODELLING AND OPTIMISATION

Abstract. This article deals with an approach for estimation of a mass moment of inertia of existing mechanical working excavator equipment. The mechanically working equipment is a part of one mechanical system of an excavator with no documentation or incomplete documentation. An experiment was carried out with real life excavator working equipment. The experimental data present a period of variation of the excavator working equipment. The period of variation is obtained by preliminary data processing of the experimental data. Confidence intervals of the mass moment of inertia and some other parameters of the mechanical system are derived. The non-linear least squares optimisation routine by the use of Levenberg Marquartd method is applied for estimation of the value of mass moment of inertia for different positions of the excavator working equipment. All investigations are made in MATLAB environment.

Keywords: mass moment of inertia, modelling, optimisation, estimation


  • Sasho GUERGOV

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3D SIMULATION MODEL OF A RECONFIGURABLE MULTIFUNCTIONAL MACHINE TOOL WITH COMPLEX FUNCTIONS

Abstract. The paper presents an active 3D computer model of a reconfigurable multifunctional machine tool, developed in SolidWorks environment. The suggested machine model provides effective environment for simulation of the work of the Reconfigurable Multifunctional Machine Tool in conditions of frequent changes in the production demand. On the other hand, the model is also used for investigation the functionality and the technological possibilities of machines with reconfigurable structures during the process of complex machining of both rotation and prismatic parts on a single machine (individually or in combination). Moreover, the machine has high concentration of various technological operations, such as: turning, milling, drilling, grinding, etc.

Keywords: 3D model, simulation model, reconfigurable machine tool, multifunctional machine tool


  • Cristian IONESCU, Alexandru MUNTEANU, Daniel MUNTEANU, Filipe VAZ, Luis CUNHA, Camelia OLTEANU

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THE TRIBOLOGICAL BEHAVIOUR OF TI-SI-C COATINGS DEPOSITED AT LOW TEMPERATURES

Abstract. The deposition field of several coatings on different substrates and the research of the Ti-Si-C thin films have attracted an increasing interest in the science world, because of the extraordinary properties showed by these new materials, which combine in a favourable way the characteristics of the metallic and ceramics materials. The present paper presents some general data regarding Ti-Si-C system, and also some experimental results obtained as a result of the deposition of Ti-Si-C coatings on high-speed steel substrate, at low temperatures. There are presented the tribological characteristics (wear behaviour, friction coefficients) of the deposited films, data obtained with a "ball on disk" CSM type tribometer.

Keywords: thin films, deposition, Ti-Si-C, wear, sputtering


  • Aurel LUNGULEASA

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TEN REASONS AND CONDITIONS FOR WOODEN BIOMASS USE AT RENEWABLE COMBUSTION

Abstract. The paper presents main ten reasons and other ten conditions of wooden biomass use as renewable fuel. After the advantages of this kind of renewable fuel (woody biomass) is presented, it is passed to the presentation of the main ten condition for efficiently using of wooden biomass as fuel, including the impact upon the environment.

Keywords: wooden biomass, renewable fuel, environment impact


  • Ionel MARTINESCU

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The Qualitative and Quantitative Evaluation of the Elements of Systems with Complex Structure

Abstract. The paper presents the qualitative and quantitative evaluation of the elements of systems with complex structure, demonstrated on a system with nine elements, taking into account the cases of reliability parameters specification time dependent. The evaluations are realized through calculus relations, tables and diagrams.

Keywords: system, reliability, complex structure


  • Georgi NIKOLOV, Boyanka NIKOLOVA

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VIRTUAL TECHNIQUES FOR LIQUID LEVEL MONITORING USING DIFFERENTIAL PRESSURE SENSORS

Abstract. The purpose of presented paper is to demonstrate an innovative approach for low cost continuous liquid level monitoring based on virtual instrumentation. Most of the traditional measuring systems were designed and implemented by complicated hardware circuitry. It made the product expensive, with low functionality and with limited precision. With virtual measurement technology, more of the instrument can be substituted by software. Using this approach the cheaper and more versatile measurement system can be developed. As introduction in order to select an appropriate method for liquid level monitoring the comparative analysis of more popular technologies is done. The method for obtaining both liquid density and liquid level with two differential pressure sensors is suggested and considered. Some basic considerations about the modern integrated pressure sensors and some aspects concerning their capability for liquid level measurement are done. Finally, a prototype of a liquid level monitoring system based on integrated differential pressure sensors, multifunction data acquisition board and LabVIEW environment is developed for measuring liquid level accurately at distances up to 10 metres. In order to illustrate flexibility of the designed system the front panel of the developed virtual instrument is presented. Measurements carried out in laboratory show that the accuracy of some millimetres could be achieved.

Keywords: virtual instrumentation, level measurement, monolithic pressure sensors, data acquisition, LabVIEW


  • Ina NIKOLOVA-JAHN

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ASPECTS OF TOTAL QUALITY MANAGEMENT IMPLEMENTATION

Abstract. Total Quality Management is a concept by which management and employees can become involved in the continuous improvement of the production of goods and services. Elements, philosophies, and famous practical models of Total Quality Management (TQM) in this paper are studied.

Keywords: quality, TQM, TQM awards, TQM implementation


  • Vesko PANOV, Rosen MITREV

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THEORETIC-EXPERIMENTAL APPROACH TO COMPUTATION OF DIGGING FORCE

Abstract. A theoretic-experimental approach to computation of digging force in arbitrary chosen points from implemented tool trajectories of earthmoving machines is proposed. The approach allows automatic collection of statistical information for digging forces and digging processes in real operating conditions. It is based on the developed original algorithms for position and static force analysis of corresponding operating equipment as well as on the obtained experimental data for pressure (force) and working stroke of chosen driving hydrocylinders. An interactive MathCAD program is developed for computation of digging force parameters in backhoe operating equipment of hydraulic excavator. The necessary forces and strokes of bucket and stick hydrocylinders for real operated hydraulic excavator BEN 195 are measured and digging force parameters are calculated.

Keywords: digging force, hydraulic excavator, position and static force analysis


  • Dimitar RALEV

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A ROTARY CUTTER FOR CUTTING OF GLUCOSE TEST STRIPES

Abstract. This paper presents the design and characteristics of a rotary cutter for cutting of glucose test stripes. It comprises all needed recommendations for cutting head geometry parameters and the selection of proper bearings. Factors affecting the accuracy and working capacity of the device have been analyzed as well.

Keywords: rotary cutter, test strips, angle of cutting, accuracy of assembly


  • Dragomir VRAZHILSKI

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SPATIAL DYNAMICAL MODELING OF MULTI POSITIONAL VIBRATION SEPARATOR

Abstract. Main purpose of this work is to evaluate the spatial dynamical behaviour of vibration separator. In this order is created and examined dynamical model representing the separator as one rigid body with six degrees of freedom, accounted are mass, geometrical, elastic and damping properties. Based on obtained differential equations of motion, are performed numerical experiments of free and forced spatial vibrations. The results represented in time and frequency domain are aimed to evaluate the dynamical behaviour of separator, the character of oscillations of points from sifting surface, the relations between generalized coordinates, also to determine the natural frequencies of the system.

Keywords: spatial oscillations, dynamical modeling, vibration separator, FFT


 

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