Volume 20, No. 1 (2014)
Articles
SIMULATING PASSIVE SUSPENSION ON AN UNEVEN TRACK SURFACE
FLORIN ANDRONIC(1), IOAN MIHAI(1), IOAN-COZMIN MANOLACHE-RUSU(1), LILIANA PĂTULEANU(1), IVAN RADION(1)
Automobile suspension systems have an important role in a vehicle's functioning, especially with regard to driving safety. In the present paper we exhibit the equations that characterize a passive suspension system. Considering that solving the equations is extremely cumbersome we developed a simulation scheme in MATLAB Simulink. The simulation allows for an analysis of the behavior of the passive suspension system on any uneven track surface whose configuration is ensured by stimulus signals. For the simulation we used the quarter car model. The suspension was chosen as having two degrees of freedom.
A STATISTICAL APPROACH TO CLASSIFY AGRICULTURAL SATELLITE IMAGES USING TEXTURAL FEATURES EXTRACTION
KEYVAN ASEFPOUR VAKILIAN(1), MOHAMMAD ABOUNAJMI(1), JAFAR MASSAH(1)
Increasing the resolution of recent satellite images has become one of the problems for image classification in scientific studies. One way to overcome this problem is to characterize the pixel being classified by parameters measuring the spatial organization of the pixels in its neighborhood. In this study, textural parameters of one-step and two-step encoded images were calculated in the formof a vector.These parameterswere subject to thesupport vector machine classifiertodecidewhich classimage is belonging to. Results showed that the encoding method is a proper way to compress an image without losing textural information. It reduces the size of data and thereby reducing the computation time characteristics.
THEORETICAL STUDIES ON LIQUID POLLUTANTS' TRANSPORT IN THE SOIL AND IN THE AQUIFER
MIHAI-COSMIN BELCIU(1), VALENTIN NEDEFF(1), ALEXANDRA-DANA CHIŢIMUŞ(1), CRISTIAN RADU(1)
The present paper describes some theoretical aspects concerning the transport of liquid pollutants in the soil and in the aquifer. The pollution of the geological environment represents the modification of the physical, chemical and biological properties of the soil, altering and restraining the soil's usage properties for its constituent elements (soil, geological formations, phreatic aquifers, deep aquifers). The pollution of the geological environment uses water as its main transport agent, in its entire global circuit: in the atmosphere (vapors and precipitation), at the level of the topographical surface (surface water flowing) and in deep levels of hydrostructures (subterraneous flowing).
FINITE ELEMENT MODELING OF CRASHING BEHAVIOR CONCERNING RECTANGULAR MULTI-LAYERED THIN-WALLED STRUCTURES
VLAD ANDREI CIUBOTARIU(1)
Tubular thin-walled structures with different shapes of the cross-sections are widely used in various transportation systems as energy absorbing components to dissipate the kinetic energy during violent collisions and crashes. The aims of this paper are to obtain numerical data on the crashing of thin-walled structures made by multiple layers of steel sheets. A series of finite element calculations was carried out on four different models crashed axially in dynamic conditions by using LS_Dyna V971. The effect of the generated fold depth on the peak load and the mean crashing load of these types of structures were also examined.
EXPERIMENTAL RESEARCH REGARDING THE INFLUENCE OF THE FRICTION FORCE FROM LINEAR ROLLING GUIDEWAYS ON THE POSITIONING PRECISION OF KINEMATIC FEED CHAINS USED ON CNC MACHINE TOOLS
MARIAN FUNARU(1), GHEORGHE STAN(1)
Friction represents one of the major sources of disturbing forces which affect the functioning of the kinematic feed chains from CNC machine tools. Its influence reflects on the positioning precision values, having a negative impact on the table movement and leading to stationary errors, stick-slip motion and trajectory errors. The present paper presents an experimental analysis regarding the influence of the friction forces which appear in the linear rolling guideways on the positioning precision of kinematic feed chains. The rolling guideways present the advantages of a good behavior in terms of axis stability at low speeds and also for achieving high positioning speeds. Concerning the friction coefficient values, rolling and hydrostatic guideways are most suitable for the construction of high speed and high precision kinematic feed chains; in these cases, the friction coefficient has small values, which maintain quasi-constant against the feed rate.
INFLUENCE OF BRAKING VALVE OPENING AND CLOSING ANGLES UPON TORQUE
IOAN-COZMINMANOLACHE-RUSU(1),CORNELSUCIU(1), LILIANA PĂTULEANU(1), FLORIN ANDRONIC(1)
Engine brake systems are based on the concept of spending a large amount of the vehicle’s kinetic energy by releasing pressure from the cylinder.Although an important part of the kinetic energy is used during compression, unless the spring effect of gases is suppressed, a good portion of it is returned to the wheel during the power stroke.This goal can be achieved by releasing of compression just before maximum cylinder pressure is reached.The present paper illustrates investigations upon the exhaust valve opening and closing angles that determine a braking event and their influence upon engine torque.
NEW APPROACH ON MATHEMATICAL MODELING OF JAKE BRAKE PROCESS FOR DIESEL ENGINES
IOAN-COZMIN MANOLACHE-RUSU(1), CORNEL SUCIU(1), FLORIN ANDRONIC(1), LILIANA PĂTULEANU(1), IVAN RADION(1)
Auxiliary braking systems, which include also the Jake brake system, have a decisive role in issues such as road safety and optimization of fuel consumption. These issues are raised especially for heavy vehicles such as trucks or buses. One of the most delicate problems encountered when designing such a braking mechanism is to accurately evaluate the thermal conditions present in the combustion chamber. Failure to know and control these conditions can lead to deteriorations of injection system components, such as the injectors, which are no longer cooled by fuel. The present paper aims to advance a simple and quite accurate mathematical model to describe the processes occurring in a Jake brake system. Such a model can be very interesting when high power diesel engines are designed.
EXPERIMENTAL APPLICATIONS ON THE INFLUENCE OF INTERNAL OPERATION CLEARANCE OF THE FAULTY ROLLING BEARINGS UPON THEIR REMAINING LIFETIME
DUMITRU-CRISTINEL NADABAICA(1), VALENTIN NEDEFF(1), LUMINITA BIBIRE(1),NARCIS BÂRSAN(1)
In the calculation of the rolling bearings lifetime are taking in to consideration the distribution of the work load on each rolling elements, obliquity, internal operation clearance and pre-stressing. In the case of a rolling bearing with a defect, the internal operation clearance have an influence upon the evolution of its deterioration and remaining lifetime by: internal manufacturing clearance; the expansion of the inner ring when the rolling bearing is mounted on a adapter sleeve; the contraction of the outer ring when the rolling bearing is mounted in the housing; and the temperature difference between rolling bearing rings during operation. This paper presents an experimental study regarding to the influence of the internal operation clearance of the ZKL 1205K rolling bearing upon the remaining lifetime in same operating conditions.
ASTUDY ON DRAWING BIMETALLIC BRAZED SHEET PARTS
IONEL OLARU(1)
This paper presents the study of the process of assembling metal sheets by using brazing of joints through cold welding. The processing technology is a normal drawing procedure. This paper explains schematically the drawing process. Aluminium and copper zinc alloys were used in order to observe the increase of the age-hardening response in brazed alloys. Of great importance is the filler material and especially the way in which it diffuses in the base materials. In this study, the material used was correctly selected, the bimetallic sheets were brazed properly and the behavior of the assembled sheets was according to standards.
HEAT TRANSFER THROUGH MINI AND MICRO CIRCULAR CHANNELS OF CPU’S COOLING SYSTEMS
LILIANA PĂTULEANU(1), IOAN-COZMIN MANOLACHE-RUSU(1), FLORIN ANDRONIC(1), IVAN RADION(1)
The cooling systems of the CPU have in their competence mini and micro-channels whose performances at intensifying the thermal transfer have been discovered and proved. It is justified the interest in studying the shape of these components, their possibilities of manufacture, the phenomenathat occur in channels of small dimensions and processes of heat transfer.The current article aims to realize a brief presentation of mini and micro-channels situated inside the cooling system of the CPU, while in the second part is proposed a calculation model for heat transfer in circular mini and micro-channels. In the case of the analyzed channel, it is realized the modeling of the process of heat exchange in micro-channels. The used model is validated by comparison with numeric results obtained by authors in specialized literature.
EXPERIMENTAL STUDY REGARDING MECHANICAL PROPERTIES OF FeP-05-MB SHEET STEELS SUBMITED TO COROSIVE MEDIUMS
ANA-MARIA ROŞU(1), NICOLETA PLATON(1), VASILICA ALISA ARUŞ(1), NECULAI DORU MIRON(1), ILEANA DENISA NISTOR(1), GHEORGHE BRABIE(2)
Corrosive mediumis a little known phenomenon and it is necessary to emphasize that corrosion is a secondary epiphenomenon in the development of bacteria and their metabolism, or that the occurrence and development of bacteria are accidents at the surface of the corroded parts. The purpose of this research is to determine the mechanical properties of a sheet steel (type FeP-05-MB) submitted to corrosive mediums. These mediums are: ambient, saline and microbiological. After the action of these mediums, the metallic samples were analyzed in order to observe the resistance at corrosion after their corrosion by different mediums.
THERMO - MECHANICAL LOADING IN BEVELLED AREA BETWEEN TWO CYLINDRICAL SHELLS WITH DIFFERENT THICKNESSES. THEORETICAL STUDY - CONNECTION LOADS
VALENTIN ZICHIL(1), RADU I. IATAN(2), LUMINITA BIBIRE(1), PARASCHIVA BUSUIOCEANU (GRIGORIE)(3), LAURENŢIU ŞERBAN(4)
This paper addresses the problem of stress concentration in the transition area, between two cylindrical shells with different thicknesses. To reduce the intensity of the stresses and strains developed under the action of external mechanical and /or thermal loads, an original method is proposed, using method of short structural elements for shells, respectively bending moments theory and deformations continuity (displacements and rotations). In this sense, the transition between shell rings is considered linear variable in four constructive variants (with the same inner or outer surface, respectively the same median surface, or different median surfaces). Based on the evaluated intensity of the stress, it can be concluded which is the preferred variant the design stage, or deduction of the same sizes, in case of technological deviations (cutting errors, so as to result the same inner or outer surface, as in case of the same median surface). Article content refers in this configuration the setting mode related of connection loads that will be taken into account in tensions expressions.
NUMERICAL SIMULATION OF LAMINAR FORCED CONVECTION AIR FLOW IN A RECTANGULAR VENTURI CHANNEL
IGO SERGE WENDSIDA(1), KOKOU N’WUITCHA(2), ISSAKA OUEDRAOGO(3), DIEUDONNE JOSEPH BATHIEBO(4), BELKACEM ZEGHMATI(5)
In this work, a laminar forced convection air flow in a rectangular vertical venturi has been numerically simulated. Mathematical transformation has been used to transform the irregular profile of the venturi wall into straight line. Transfers equations are solved using finite volume method, Gauss and Thomas algorithms. A computing algorithm has been generated for the problem simulation. Hydrodynamics and thermals effects are investigated in detail. Results are presented as velocity and streamlines patterns, and temperature profiles.