No. 6 ( 2000)

Articles

A PROTOTYPE OF A FARM MACHINERY DIAGNOSTIC EXPERT SYSTEM
VULEVA VALENTINA, STANEV IVAN, CHAVDAR VEZIROV

The paper presents HADES - Hypermedia Adaptive Diagnostic Expert System. It can be used for diagnosing various farm machinery. The requirements, overview and analysis of the existing state-of-the-art with respect to the diagnostic expert systems are presented. The general architecture of HADES is described, also the methods used for knowledge representation and knowledge acquisition. The choice of a combination of case-based, model-based, and rule-based reasoning methods is substantiated. A diagnostic problem solving strategy is suggested and realized as a prototype for diagnosing brake and fuel systems. The main features and advantages of the prototype are described in the paper.

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FATIGUE STRENGTH CALCULATION OF NON-LINEAR AND CRACKED MATERIALS
JINESCU VALERIU

A general expression is established for the overall participation to the damage in case of a non-linear material with cracks, fatigue loaded; it allows fatigue strength calculation, with respect to the critical state (fatigue breaking) or to the allowable state. Through particularisation there were obtained the well-known relations for fatigue strength of linear-elastic materials (Gough and Pollard, Buzdugan, Soderberg, Goodman, Gerber, Cioclov. Crawford and Benham), Miner's cumulative damage rule. Morozov's relation for a cracked material loaded in tension. Generally speaking, the theoretical results may be used for a better evaluation of the experimental results, as well as for a better understanding of the superposition problems with application in the field of fatigue.

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ABOUT A CORRELATION BETWEEN FUNCTIONAL AND GEOMETRICAL PARAMETERS OF CYLINDRICAL VERTICAL DRUMS FROM CENTRIFUGAL DEVICES FOR SEDIMENTATION
IATAN RADU, CIRSTOIU ADRIANA, DUMITRESCU VERONICA, BRAŞOVEANU MARICICA

This booklet studies die geometry of suspension inside a cylindrical vertical drum from a centrifugal device, being in rotation, and the pressure of charge. There will be done the proper correlations for drum's geometry taking into account the characteristic functional parameters. The illustration of theoretical results is done on a known centrifugal device, with known features.

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PROCESS PARAMETERS IMPROVEMENT IN POLYMER INJECTION MOULDING
ŞTEFANESCU MARIANA FLORENTINA, TACA CONSTANTIN DAN, PĂUNESCU MIHAELA

The paper presents optimisation strategy of the main process parameters: injection mould temperature and pressure. The obtained relations are applied for PS polymer and are compared with the results of C-MOLD Rapid Designer simulation program.

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COEFFICIENTS INFFLUENCE POROSITY AND MOBILITY ON SEDIMENT PRESSURE OF CENTRIFUGAL TAMBUR
IORDACHE GHEORGHE, ŞTEFANESCU MARIANA FLORENTINA

A calculation relation is suggested for the calculation of the deposit pressure on the head (cover) of the centrifuge drum, which takes into account the fraction of gaps among the deposit particles and the coefficient for the transmission of the pressure on a perpendicular direction, depending of the main direction of its action. The value of pressure, calculated by the suggested relation, is over 10% reduced then that obtained by the known relations. This fact allows the elimination, without risk, oversizing the head (cover) of the drum in the centrifuge.

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RESIDUAL STRESSES ANALYZE IN INJECTION MOLDED PRODUCTS
ŞTEFANESCU MARIANA FLORENTINA, TACA CONSTANTIN DAN, PĂUNESCU MIHAELA

The residual stress formation mechanisms are studied for injection mold process. A simple, but physically relevant, elastic solid model is assumed (viscous melt and purely elastic solid). Residual stresses found in the constrained quenching case are proportional to the maximum melt pressure and are tensile near the surfaces. A comparison between this model and Baaijens's model is made.

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FIT CORRECTION AS A PROFILAC TIC MEANS ADDRESSING THE ACCOMPANYING PERTURBANCE FACTORS
BAGIU LUCIAN

The nature of the adjustable tool-machines (points a1, a2, a3, a4 below), the specific functional temperature of each piece (point b he low) as well as the roughness over the pair pieces surface (point c)i can drastically distort (falsify) the relation between the contact values at their fit. In the present study, we discuss the accurate measurements by establishing the ideal values which come from statistical and methodological estimations (calculus).

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IMPROVEMENT OF STABILITY OF A RELAY CONTROL SYSTEMS USING ON - OFF ELEMENT WITH SINGLE POLARITY CHARACTERISTICS
PORTEANU MIRCEA

In this paper is presented the improvement of the stability of a relay control system whose nonlinear part contains an on-off element with generalized characteristic which may generates all types of single polarity characteristics including those with and without hysteresis. It is shown that for some of these characteristics no self-oscillations exist and therefore the relay control system is stable.

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THE POSSIBILITY TO RECONDITION THE SILVER ELECTROPLATED COPPER OF LIVE PARTS OF SWITCH EQUIPMENTS BY VIBRATING ELECTRODE METHOD
CIUCESCU DORU, PUIU-BERIZINŢIU MIHAI, GHEORGHIU IOAN

Materials used for electrical contacts in switches and relays must have a good combination of electrical conductivity and wear resistance. Electrical contacts are widely made by particulate composites like tungsten reinforced silver, because the silver efficiently conducts current while the hard tungsten provides wear resistance. Even such contacts erode in time causing poor contact and arcing. Another material used for electrical contacts is silver electroplated copper. To recondition these contacts is widely used silver electroplating, which is very expensive. In tlus paper arc done the experimental data of searching to recondition electrical contacts made from silver electroplated copper by vibrating electrode method.

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QUALITE ISO 9001 EN ECOLE D’INGENIEUR "MISE EN PLACE D'UN SISTEM D'ASSURANCE QUALITE SELON REFERENTIEL ISO 9001 DANS UN LABORATOIRE D'ENSEIGNEMENT ET DE RECHERCHE"
CRISTEA ION*, GEAMĂN VIRGIL**, CIUCESCU DORU*

La mise en place de syslemes bases sur les normes internationales ISO 9000, est aujourd'hui le passage oblige de la competitivite des entreprises face a la concurence. Ce soucis de qualite initie par l'industrie dans le monde, amene les domaines de la recherche et de I'ensseignement a se pencher sur la qualite des prestations qu’ils dispenset apres des entreprises. Conscient que la qualite des produils fail l'objet d’une forte attention des industriels, le Laboratoire de l'Inginene de la Qualite de I'Universite de Bacau s'est angaje dans une demarche voloniaire de certification de ses activiles

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ON THE STEADY-STATE TEMPERATURE DISTRIBUTION IN A ROTATING CYLINDER SUBJECT TO HEATING AND COOLING OVER ITS SURFACE
CĂLIMAN RADU, FLORESCU DANIELA

A series solution for the two dimensional, steady-state temperature distribution in a rotating cylinder, subject to surface heating flux conditions that are at most linear functions of the surface temperature, is applied to strip rolling. An examination of the influence of heat input over the heating region (roll gap) on the peak cylinder (roll) temperature is made.

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NATURAL CONVECTION FROM A HORIZONTAL CYLINDER -TURBULENT REGIME
CĂLIMAN RADU, FLORESCU DANIELA

a two-equation model has been adopted in obtaining numerical solution of turbulent natural from an isothermal horizontal circular cylinder The k-e model employed in this study characterizes turbulence through the kinetic energy and its volumetric rate of dissipation The transport equations for these two variables, along those for time - averaged stream function, vorticity, and temperature, form a closed set of five coupled partial differential equations These equations are solved for the entire flow domain, without boundary layer approximations.

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STEADY STATE TEMPERATURE DISTRIBUTION IN A SOLID CYLINDER MOVING IN THE DIRECTION OF ITS AXIS THROUGH A CROSS-FLOW OF HOT GAS
CĂLIMAN RADU, FLORESCU DANIELA

a range of boundary value problems is solved that describe the steady slate temperature distribution in a solid circular cylinder of infinite length, moving in the direction of its axis. The cylinder is heated by a hoi gas flowing perpendicularly to the cylinder. The problems differ in complexity depending on whether or not the cylinder is radially isothermal and the gas temperature uniform. Dimensionless charts arc presented. This work pertains to the "moving wire techniques" for studying polymer flammability and measuring heat transfer from gases.

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RESEARCHES REGARDING THE UTILISATION OF LIGNOPHENOLIC RESIN FROM SODIUM LIGNOSULPHONATES OF THE SPENT SULPHITE PULPINE LIQUQRS TO THE MOULDING TECHNOLOGY
CIOBANU DOMNICA, TUDOR LIVIA

The lignophenolic resin was utilised as a component of the moulding mixtures. Its influence over the quality of the mixtures was studied. The comparison to novolac was made in order to replace the last one with lignophenolic resin. According to the obtained results, there was estimated the possibility to use the lignophenohc resin as a great efficacious component of same sorts of moulding mixtures.

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RESEARCHES CONCERNING CAPITALIZATION OF WASTED PLASMA IN FOOD TECHNOLOGIES FOR GETTING SOME MEAT PRODUCTS - I. RESEARCHES CONCERNING PLASMA BEHAVIOR UNDER THE INFLUENCE OF SOME PREVAILING CONDITIONS
CIOBANU DOMNICA, TANTOS LIVIA, TANTOS IULIAN-MIHAI, BOCĂNEALĂ VASILE

The conditions of blood plasma treatment in concentrating and drying processes are very important both theoretically and practically. That's why we initiate this study to find some optimum values for the conditions that influence the speed and the efficiency of these operations. The results should get an idea of how the fresh plasma should be treated to get the maximum output both qualitative and quantitative.

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ANALYSIS OF HETEROGENEOUS POLYDISPERSE SYSTEMS
NEDEFF VALENTIN, MOŞNEGUŢU EMILIAN, PANAINTE MIRELA

The heterogeneous system has been formed from many phases (parts), which has physical propriety different, right determine which determined the separation of system in components phases. In analysis of heterogeneous polydisperse system to take into account the form and dimension of particles, which formed phases of system.

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GRADING ANALYSIS OF PARTICLES AN POLYDISPERSE SYSTEM
MOŞNEGUŢU EMILIAN, NEDEFF VALENTIN, PANAINTE MIRELA

the paper presents the principle of grading analysis which to lie at the basis choose separation method and the number of fraction can be separated on the polydisperse system. Grading analysis to rely on so much on analysis of medium dimension the particles just like on analysis of distribution on particles size.

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AN APPROACH TO AIR, WATER AND LAND QUALITY CONSIDERING AGRICULTURE LIKE A SUPPLIER OF POLLUTION AND DEPOLLUTION
EŞANU GHEORGHE, CIUCESCU DORU

Pollutants commonly are classified to the part of environment affected by them: air, water and land. Subgroupings depends on characteristics of the pollutants themselves: chemical, physical, thermal and others. The environment quality norms establish admissible content of pollutants in air, water and land. It is clear that the agriculture, which produces pollutants, but also vegetable materials and. consequently, oxygen, is in a different position with industry. This paper makes a presentation of pollutants existing in air, water and land, taken into consideration the influence of agriculture.

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A RUDOLOGICAL STUDY OF METALLURGICAL PLANT "ROBINETE INDUSTRIALE" FROM BACAU
CIUCESCU DORU, EŞANU GHEORGHE

The control of pollution has provided many of the most difficult economic, legislative and administrative questions of the 20th century. In all cases the society is paying the costs of trash removal, nutrional deficiency and so on. The best way to begin to tackle the issue is through case studies. This paper makes a critical presentation of material inputs and wastes of plant "Robinete Industriale" from Bacau in order to draw the appropriate conclusions to keep as high as possible the standards of safety, especially to explore how to make use of by-products generated during materials processing.

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IMPROVEMENT OF THE MACHINES FOR THE MECHANIZATION OF THE SEEDLINGS TRANSPLANTING
CRĂCIUN VASILE, BUMACOV VASILE

In this paper the authors present a new machine for transplanting vegetable seedlings, grown into nourishing pots. The appropriate development to increase the labor capacity and to facilitate the plant growth, without retardation because the transplanting process, is to grow seedlings in nourishing pots and to use semiautomatic transplanting machines for such seedlings.

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A STUDY TO CURB NOISE EXPOSURE IN A FETTLING WORKSHOP FOR GRAY IRON CASTINGS
SIMIONESCU GHEORGHE, CIUCESCU DORU, SAVIN CARMEN

In industrial society there is the problem of noise pollution. Exposure to excessive noise may produce a variety of traumas, starting with an unpleasant feeling and ending with a permanent hearing loss. Environmental acoustics deals with noise control, trying to produce quieter machines or to insulate better the buildings. In workshops for finishing gray iron castings the noise power level is very high causing many ill absences. This paper presents the noise problem in a fettling workshops for gray iron castings of S.C. "Robinete Industriale" from Bacau and the ways to prevent the effects of noise exposure.

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CHEMICAL TREATMENT OF COOLING WATER: A WAY TO REDUCE WATER CONSUMPTION AND ENVIRONMENTAL POLLUTION
GAVRILĂ LUCIAN*, GAVRILĂ DANIELA**

In an open recirculating cooling system, the cooling water is permanently exposed to the atmosphere, saturating with oxygen and absorbing gaseous contaminants (sulfur compounds, nitrogen oxides, ammonia) that exist in the atmosphere of the process plants. The absorbed contaminants, together with the dissolved solids from the make-up water increase the aggressive character of the cooling water. The corrosion, scaling and fouling are emphasized and fastened, finally leading to the worsening of the heat transfer rate and to a premature failure of heat exchangers and pipes network. A proper chemical treatment of the cooling water leads to corrosion mitigation, descaling of pipes and equipment, prevents fouling, subsequently leading to an improved heat transfer and reduced fresh water consumption. The paper presents the advantages of chemical water treatment in industrial cooling circuits.

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STUDY OF THERMODYNAMIC PERFORMANCE OF AN INTEGRATED GASIFICATION COMBINED CYCLE POWER PLANT
RAVEICA IONEL, CIUCESCU DORU

Computational Analysis is performed to investigate the effects of the pressure ratio of the gas cycle (Rp) and the temperature ratio across the combustion chamber (R) on the thermodynamic performance of an integrated gasification combined cycle (IUCC) The total exergy loss of the cycle is found to decrease with either of these two ratios while the other is held constant.

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ECONOMICAL ASPECTS OF INFLUENCING FACTORS ASSURING NECESSARY PRESSURE DIFFERENCE OF A SEED PNEUMATIC DISTRIBUTING DEVICE WITH A DRUM
EŞANU GHEORGHE*, CIUCESCU DORU*, MOŞNEGUŢU EMILIAN*, BONTAŞ OVIDIU**

An ideal seed distributing device must realise a dosage seed by seed, without empty spaces. Usually, a good distribution device works between admissible limits. In a seed pneumatic distributing device the catching force to keep seeds on distributing orifices depends directly of pressure difference. This paper presents a relation to establish the necessary pressure difference for an optimal seed distribution process of a pneumatic device according with constructive and functional parameters and seed characteristics.

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THE MODELLING PROCESS OF EXTRACTION OF COPPER FROM SPENT CATALYSTS Cu-Mg-Al2O3 - II. TEMPERATURE INFLUENCE
ISTRATI LĂCRĂMIOARA *, IVANICIUC MARIA **, NISTOR DENISA *

In the paper is presented the researches about establishing the macrokinetics mechanisms and the mathematical of the copper extraction from spent catalyst Cu-Mg-Al2O3 process. The influence of temperature on the global speed of the process researches and the experimental results arc presented. The experimental results lead to the conclusion that the global speed of the process is getting higher along with the temperature rising as long as the stability of the copper-ammonia complex it isn`t affected.

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MODELLING AND SIMULATION OF CARBON DIOXIDE ABSORPTION INTO ACTIVATED POTASSIUM CARBONATE AQUEOUS SOLUTION
IVANICIUC MARIA*, ISTRATI LĂCRĂMIOARA**

The aim of this study was to investigate the absorption of carbon dioxide into activated solution. The process may be utilization for purification of gases resulted from combustion of combustible. The accuracy of the mathematical model of the carbon dioxide absorption into potassium carbonate aqueous solution has been evaluated by comparison of the measured and computed values of CO2 molar fraction in the treated gas. Mathematical model used for simulation was a system of six equations, which described variation of composition for liquid and gas phases. The deviations were not greater than 0.76% for H2 O and 4.0% for CO2 molar fraction in the purified gas. The model experimentally tested has been applied for the simulation of the column equipped with the Pall metallic rings packing. The results show superior performances in the same operating conditions.

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INVESTIGATIONS IN THE SYNTHESIS OF ORGANIC EXTRACTING AGENTS FROM CELLULOSE PROCESSING WASTES - I. REVERSE OSMOSIS
NISTOR DENISA, CIOBANU DOMNICA, ISTRATI LĂCRĂMIOARA, URSU ALINA

Reverse osmosis technology has a great potentional in the field of wastewater reclamation. A reverse osmosis plant includes the following processes: (1) feed water microfiltration and chemical conditioning, (2) membrane treatment, (3) permeate aeration, neutralization and (4) concentrate (liquid residue) treatment and disposal.

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INVESTIGATIONS IN THE SYNTHESIS OF ORGANIC EXTRACTING AGENTS FROM CELLULOSE PROCESSING WASTES - II. REVERSE OSMOSIS TECHNOLOGY FOR WASTEWATER REUSE
NISTOR DENISA, CIOBANU DOMNICA, ISTRATI LĂCRĂMIOARA, URSU ALINA

The performance of reverse osmosis membranes depends on operating conditions and water quality parameters. Permeate productivity and contaminant removals increase with applied hydraulic pressure.Water quality parameters such as concentration, composition and pH also affect contaminant removal efficiencies. For example, the treatment of a simulated wastewater containing 10 mg/L of nitrate with a commercial polyamide-type reverse osmosis membrane resulted in membrane permeates containing approximately 0.05 mg/L of nitrate (or 99.5 percent removal) when sodium chloride was the major dissolved solid present in the feed water, and 1 mg/L (or 90 percent removal) when sodium sulfate was the predominant component. The removals of weak electrolyte contaminants are affected by feed water pH. For example, the removals of boron by a cellulose acetate-type membrane was reported to be greater than 99 percent at a pH of approximately 11, and less than 30 percent at a pH of 7. The practice of pre-treatment processes such as microfiltration and chemical conditioning can minimize performance deterioration resulting from membrane fouling by inorganic precipitates, organic macromolecules and microorganisms (biofouling).

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THEORETICAL RESEARCH CONCERNING ON WHIRL DYNAMICS OF A ROTOR PARTIALLY FILLED WITH LIQUID
BIBIRE LUMINIŢA

A spinning rotor, mounted on a elastic shaft and containing a symmetrically located cylindrical chamber partially filled with liquid is assumed to undergo a small whirling motion. In the analysis, rotor unbalance, gravity and gyroscopic terms are considered negligible and the liquid motion is taken as being axially uniform. The added liquid produces a lowering of the usual synchronous critical speed. In addition, waves in the liquid layer couple with rotor whirl motion to produce a range of self-excited asynchronous whirl speeds above the critical, similar to those observed for nonsymmetrical solid rotors.

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DESIGNING VIBRATING BEAMS AND ROTATING SHAFTS FOR MAXIMUM DIFFERENCE BETWEEN ADJACENT NATURAL FREQUENCES
BIBIRE LUMINIŢA

Using the cross-sectional area function as the design variable, we determine the optimal design of a transversally vibrating, thin, elastic beam or rotating shaft that maximizes the difference.n -.n-1 between two adjacent natural frequencies or critical whirling speeds wn and.n-1 of given order. The beams have geometrically similar cross- sections while the shafts are restricted to be circular, and a minimum constraint is prescribed for the cross-sectional area. The volume, length and boundary conditions are assumed to be given, and the beams or shafts may be equipped with given, non-structural masses or disks.

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EXPERIMENTAL RESEARCH CONCERNING OF A WHIRL DYNAMICS OF A ROTOR PARTIALLY FILLED WITH LIQUID
BIBIRE LUMINIŢA

Within present work, the whirl dynamics are reconsidered by allowing for the possibility of asynchronous whirl frequencies. The system is an asymmetric cylindrical of symmetry which is fixed in space. The equilibrium motion liquid may be superimposed on this equilibrium motion. Due to the Coriolis force, there are two frequencies for each nodal pattern. For our system, the angular speed vector of the container traces a circular path in a plane perpendicular to the axis of rotation. Thus our interest is in force rather than free vibrations of the liquid. Within present work the liquid is taken as being inviscid, and no assumptions arc made a priori about the nature of the radial and tangential velocities in the body of the liquid. Experiments completely corroborate the analytical results.

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CONTRIBUTIONS REGARDING THE ESTABLISHMENT OF THE TECHNICAL AND ECOLOGICAL IMPACT OF THE UTILISATION OF THE FIBROUS WASTE IN THE PAPER INDUSTRY - II. EXPECTATIONS REGARDING THE UTILIZATION OF WASTE PAPER FROM THE PAPER INDUSTRY
CIOBANU DOMNICA, BULEU ILEANA

the waste paper from the paper industry represents a major pollutant of the environment. In order to reduce the pollution level, there were accomplish researches regarding the utilization of it, by recycling in the paper industry - process that can lead to the replacement of about 30% of the fibrous matter consumption, needed for the paper products.

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A TOOL WORN-OUT AND BREAKAGE DETECTION SYSTEM USING THE VIBRATION MONITORING
ZICHIL VALENTIN

An on-line and in-process based monitoring system lo detect tool breakage via an acccelerometer was developed and successfully evaluated in an end milling operation. Prior to testing and evaluation of the tool breakage condition, a simulation model was developed. Transfer of the on-line vibration signal to the frequency domain employed the fast Fourier transfer function, and set thresholds were used lo determine the tool condition after various experimental tests.

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THE DESIGN OF PRESTRESSED MULTI-RING HIGH-PRESSURE CONTAINERS MADE FROM MATERIALS WITH IDENTICAL ELASTIC CONSTANTS
UNGUREANU VIOREL, PINTILIE GHEORGHE, STAN GHEORGHE

The locus of this paper is the formulation of an optimization technique for the design of prestressed multi-ring containers taking in account the mechanical characteristics of materials and a maximum internal pressure. For a cylinder with the same elastic constants as the shrinking rings, the dimensions of a prestressed container arc determined as a function of the allowable stresses of the liner and internal pressure. In this papa the design objective is to keep all the stresses within the elastic limit under operating conditions.

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AN NOVEL TECHNIQUE FOR UNIAXIAL COMPRESSION TEST OF SHEET METAL SPECIMENS AND SOME EXPERIMENTAL RESULTS
UNGUREANU VIOREL

A novel technique for uniaxial compression lest of sheet metal has ben developed which allows the directly measure stress-strain relationship and eliminates the experimental problems of large strain gradients and friction inherent in some usual testing methods. The compression work-hardening curve have been determinated for aluminium, aluminium alloy, stool and titanium alloy and compared to those obtained at the same strain rate in uniaxial tension The validity of proposed method is examined at different strain levels and is concluded that the method is quite reliable and can be used in the study of forming behavior of sheet metals.

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THE EQUIPMENT FOR EXPERIMENTAL DETERMINATION OF FLDs AND FLSDs
UNGUREANU VIOREL, BRABIE GHEORGHE, JUDELE ADRIAN

A modified Marciniak testing method is proposed so that is no need of further utilisation of the spacer used in a classical lest. Combined with the utilization of CCD camera for image capture of the tested specimen and the image analysing program, the forming limit diagrams and forming limit stress diagram may be obtained.

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THE SIMULATION OF THE STRESS STATE FOR DEEP DRAWING OF CYLINDRICAL PARTS BY DIFFERENT WORKING CONDITIONS
UNGUREANU VIOREL

A numerical model is developed to estimate the variation of thickness, stress and strain distribution in the flange of partially drawn cylindrical parts taking into the consideration both nonlinear strain-hardening and frictional force between blank and tooling surfaces. The stress and strain distribution simulation allows the proper choice of working parameters such as retaining pressure and friction coefficient. The reduction of friction coefficient reduces the stretching effect and thinning of the wall of the cup. conversely a high value of the friction coefficient and high strain-hardening enhances the stretching effect and thickness reduction.

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THE EXPERIMENTALLY DETERMINATED FORMING LIMIT DIAGRAM FOR ALUMINUM AND SOME ALUMINUM ALLOY
UNGUREANU VIOREL, PANOSCHI CRISTIAN

This paper deals with the experimental determinated forming limit diagrams at the necking of thin aluminum sheets obtained by the application of a new method of necking detection and strain measurement based on digital image analysis. The two analyzed images usually correspond to the initial, unstressed specimen and the image just before the necking. The forming limit diagrams were obtained using direct strain path and complex strain paths. The result obtained indicates that the forming limit diagram strongly depends from strain path and state of stress applied

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