Volume 3, No. 15 (2009)
Articles
A STUDY OF THE ITERATIONS IN THE DESIGN PROCESS, BASED ON MARKOV CHAIN MODEL
ANGHEL DANIEL-CONSTANTIN, BELU NADIA
This paper presents a methodology to analyze and to simulate the design iteration in the design process. The first research method used in this work relies on observation of the design process. The second research method is based on the DSM (Design Structure Matrix) representation of the tasks of the design process. In our work, a model based on Markov chain was used to simulate a group of design tasks. For this purpose a laboratory experiment was used. The results could be used to make recommendations for the designers to improve the performances of the design process.
A STUDY OF THE ITERATIONS IN THE DESIGN PROCESS, BASED ON MARKOV CHAIN MODEL
ANGHEL DANIEL-CONSTANTIN, BELU NADIA
This paper presents a methodology to analyze and to simulate the design iteration in the design process. The first research method used in this work relies on observation of the design process. The second research method is based on the DSM (Design Structure Matrix) representation of the tasks of the design process. In our work, a model based on Markov chain was used to simulate a group of design tasks. For this purpose a laboratory experiment was used. The results could be used to make recommendations for the designers to improve the performances of the design process.
ACOUSTIC CHARACTERISTICS EVALUATION OF THE INSULATION AND ABSORPTION SCREENS FOR THE NOISE FROM INDUSTRIAL AREAS AND URBAN TRAFFIC. METHOD AND MULTIFUNCTIONAL SYSTEM
BOHÂLŢEA CĂTĂLIN(1), DRĂGAN NICUŞOR(2)
This paper is focused on the measurement systems for obtaining the characteristics of the screens used in controlling industrial noise and urban traffic noise. There are two systems that could be used for a good determination of the acoustical parameters of the screens. The method and the system have tested "in situ" by the specialists of The Research Institute for Construction Equipment and Technology ICECON S.A. Bucharest and those from The Research Centre of Machines, Mechanic and Technological Equipment - MECMET.
NUMERICAL SIMULATION FOR A POSITIONING HYDRAULIC SYSTEM DRIVEN BY A SERVOVALVE
CĂLĂRAŞU DORU, CIOBANU BOGDAN
The paper presents the input-state-output mathematical model for a positioning hydraulic system driven by a servovalve. The state variable method permits the numerical simulation on a computer of the dynamic working conditions. The results obtained experimentally permits the validation of the proposed model. Numerical simulations for a positioning hydraulic system driven by a servovalve are made.
DYNAMIC ANALYSIS OF A SELF-ADJUSTING DRIVING SYSTEM FOR A SLIDING CAPACITY MOTOR
CĂLĂRAŞU DORU, CIOBANU BOGDAN
The paper presents the dynamic analysis of a self-adjusting driving system for a sliding capacity motor, in constant pressure conditions. The numerical simulation on computer permits the determination of the dynamical performances of a self-adjusting system in various working conditions by the help of computer studies. The experimental results permit the validation of the proposed model. Numerical simulation and experimental tests for a self-adjusting driving system of a sliding capacity motor are made.
REGARDING AN EVALUATION METHOD OF THE RESIDUAL LIFE DURATION OF TECHNOLOGICAL EQUIPMENT FROM PETROCHEMICAL INSTALATIONS IV. CASE STUDY
IATAN I. RADU, MARIN ALEXANDRU
The article makes an analyze of the tension state in some constructive elements of a steam over heater from a petrochemical technological line, regarding the evaluation of the residual life duration. In this respect there are taken into question the results of measurements made and the normal functioning and conservation period. Are deducted the tension states, southern, circumferential and equivalent stress developed in the cylindrical body of the over heater and in the cover with advanced damage.
UPON CHARACTERISTICS AND EFFECTS OF DEBRIS CLOUD BY NUMERICAL SIMULATION OF THE HIGH VELOCITY IMPACT USING SPH METHOD
NĂSTĂSESCU VASILE
This paper presents some results of the researching work of the author regarding to the high velocity impact. Characteristics aspects were studied by Finite Element method (FEM) and by Smoothed Particle Hydrodynamics (SPH). The most fitted numerical method for studding of these aspects is SPH. This is a meshless Lagrangian numerical technique used to model the problems where large mesh distortions occur. Nowadays, the risk of collision between spacecraft and orbital debris is becoming more and more important, so such a study is a necessary one. The conclusions are useful for the aircraft specialists but, in the same time, the conclusions and the calculus model are useful for the users of this numerical method - SPH - which is more and more used in mechanical engineering. In this paper, the impact velocity was 5 km/s, the projectile was represented by a sphere, of aluminium, with a diameter of 6 mm and the target was a plane plate having a thickness of 1 mm. The effect of debris cloud was illustrated using one and two plate, both of aluminium, or the first plate of aluminium and the second plate of steel.
DETERMINATION OF THE STATIC AND DYNAMIC FRICTION COEFFICIENTS FOR THE MILLING PRODUCTS AND THEIR VARIATION WITH RESPECT TO SOME PARAMETERS
ORĂŞANU NICOLAIE, VOICU GHEORGHE, UNGUREANU NICOLETA
In this paper we present a method of determination of the static and dynamic friction coefficients values for the milling products and we study how these depend of the kinematic parameters of the sieve motion. The determination of the static friction coefficient was made using the inclined plane method, while the dynamic friction coefficient is based on the determination of the resistant mechanical work consumed to overcome the frictions. The determined friction coefficients have general aspect, due to the fact that the materials motion on the working surface is very complex: slipping, rolling, sliding etc.
FLANGED JOINT TIGHTNESS AND FLANGE'S RIGIDITY INFLUENCE
PĂUNESCU MIHAELA, TACĂ CONSTANTIN
This paper presents the results of an experimental research about the tightness of flanged joint, equipped with gaskets from marsit. As a consequence of the experimental data processing, the calculation relations of the tightening of the gaskets, depending on the inner pressure and on the gasket dimensions are established. As well, was quantified the influence of circumferential deformation of flanges about the specific pressure on the gasket.
RESIDUAL STRESSES AND DEFORMATIONS AT RING - SHAPED DISKS IN THERMAL FIELD (PLASTICITY CRITERIA). PART I
RADU GHEORGHE NICOLAE(*), COMĂNESCU IOANA SONIA M.(**)
The present paper presents the theoretical method for determination of the deformations and the loss of stability of the disk stressed by an axial - symmetric thermal field, variable according to disk radius and thickness, superposed with a field of membrane tensions given by the rotational motion. The experimental results confirm the theoretical hypothesis. This paper also presents the tension and deformation state of the disks being in a non - stationary field of temperature. The study is done until the plastic deformations occur.
THEORETICAL CONSIDERATIONS, SIMULATIONS AND EXPERIMENTAL TESTS ABOUT DISKS REZIDUAS STRESSES CAUSED BY TEMPERATURE FIELD. PART II
RADU GHEORGHE NICOLAE(*), COMĂNESCU IOANA SONIA M.(**)
The present paper presents the theoretical method for determination of the deformations and the loss of stability of the disk stressed by an axial - symmetric thermal field, variable according to disk radius and thickness, superposed with a field of membrane tensions given by the rotational motion. The experimental results confirm the theoretical hypothesis. This paper also presents the tension and deformation state of the disks being in a non - stationary field of temperature. The study is done until the plastic deformations occur.
COMPUTATION PHYSICAL PATTERNS FOR FOLDED CONSTRUCTION OF THE EQUIPMENTS
SÂRBU LAURENŢIU
This article deals with the dynamic behavior of a folded structure for building equipments during the transportation taking into account the construction elasticity as well as its excitation through the speed of the road. For this, a computation physical pattern was designed for the behavior in dynamic operation of the folded structure transported on the tired wheels followed by the auto lifting on site. The folded structure consists of 3 hours linked together and altogether on the support through joints and springs that represent the cylinder rigidity on bending of the hydraulic cylinders used to handle it. Equation system was calculated and the result is a biquadrate differential equation depending on the structure rotation against the support followed by graphically designing the obtained function and speed function respectively.
THE "BACKDRAFT" THE FIREMEN'S NIGHTMARE
SUSAN OLEG(1), PANAITESCU VALERIU(2), ŢULEANU CONSTANTIN(3)
Through the present article, using the fire simulation program "FDS", the authors present different intervention tactics for the fire scenarios in witch they can achieve the backdraft, proposing intervention methods for the reduction or even the avoidance of this phenomenon. This information as well as the recommended methods in the article can be successfully used in developing the fire security engineering and also during the training management of the firefighting.
SOME ASPECTS ON SAVING AND RECOVERING ENERGY IN HYDRAULIC SYSTEMS
TIŢA IRINA, CĂLĂRAŞU DORU, MARDARE IRINA
Reducing energy consumption is an important trend in development of fluid power systems. Improving the characteristics of fluid power systems must not entail rendering fluid power more complicated, more expensive, or more maintenance intensive. Among the important solutions for saving energy in hydraulic systems is included load-sensing and secondary control. Using secondary control hydraulic systems in impressed pressure circuits one can obtain a substantial growth of efficiency. Tasks for the future can be seen in the recognition of possible new applications that could not be identified so far. It will result important energy saving.
RESEARCHES ON THE GRINDINGS CHARACTERISTICS IN THE TECHNOLOGICAL BREAKAGE PHASE AT A FLOURING MILL WITH CAPACITY OF 220 t / 24 h
VOICU GHEORGHE, DAVID MIHAELA-FLORENTINA, TUDOSIE MĂDĂLINAAND GHEORGHE CONSTANTIN
In this paper is presented a technological scheme of the breakage phase for a wheat mill with capacity of 200 t / 24 h and the research of the experimental results related to the grindings features before and after passing through the roller mills. Researches have been made at SC Spicul SA, equipped with modern B?hler equipment. Ground material and grind products were analyzed using a classifier with sieves, in order to determine the degree of grind. Determinations were made on specific mass and materials density, to establish the increase of the area in the grinding process. Graphs are presented regarding the separation on the classifiers sieves for five roller mills, for the breakage phase results by regression analysis of experimental data obtain with Rosin-Rammler relationship and coefficients determined by this analysis. In the paper are presented correlation coefficients of R2, which have values in R2 ? 0.980. The results presented in the paper are important to specialists in the milling industry.
COMPARATIVE EXPERIMENTAL RESEARCHES ON MIXING BEHAVIOUR OF WHEAT FLOURS
VOICU GHEORGHE, TUDOSIE MĂDĂLINA, DAVID MIHAELA-FLORENTINA PARASCHIV GIGEL, GHEORGHE CONSTANTIN
In this paper are presented comparative experimental research results regarding the rheological mixing behaviour of wheat flours with the Brabender Farinograph. Three wheat flour types were tested, produced by SC Spicul SA Rosiori in 2008: FA-480, FA-650 and FN-graham. Also, was tested the mixing behaviour of FA-650 wheat flour with 0,4% to 2% salt addition, in comparison to usual flour. The paper presents the results of experiments and graphic characteristics of flour and the obtained farinograph curves, aiming to highlight the influence of kitchen salt on rheological behaviour of flours. The experimental results are important for the specialists conducting the technological processes of the bakery.
ANCHORAGE-SHIP-BERTH LINK AS QUEUEING SYSTEM WITH PRIORITY SERVICING IN PORTS
ZORAN RADMILOVIĆ(1), BRANISLAV DRAGOVIĆ(2), DONG-KEUN RYOO(3)
Ship arrivals and loading/unloading operations at ports are frequently considered to be a stochastic nature and are convenient to be modeled with queueing theory. In this paper we considered an anchorage-ship-berth link (ASB link) in which ship arrivals are assumed to follow the Poisson distribution and their servicing to have deterministic and exponential service rates. In addition to this, we assumed that the ships are served on a "first come - first served" basis with preemptive and non-preemptive priorities and that the anchorage area is limited and unlimited. As usually in the real-life port situations, some classes of ships of liner service are given the first class priority and the other classes of ships are given the second class priority. The whole multi-purpose terminal (in sea and river ports) is designed as an M/D/c/N queueing system in first case with limited anchorage and in second case the multi-purpose port terminal is designed as an M/M/c queueing system with unlimited anchorage area in Kendall's notation. Obtained analytical results are meant to be helpful to the port planning to the process in the best possible time saving way.