No. 5 ( 1999)

FORMATION OF CARBON (CYANOPOLYNE) AND OF DIAMOND IN Fe-C ALLOYS

SAVULYAK V.I., ZHUKOV A.A.

New forms of carbon in Fe-C alloys that had been obtained experimentally or may be produced in the future are discussed. Carbyn, as the "linear" allotropic form of crystalline carbon, has not yet been obtained in them and allegations to the contrary are seemingly false. The electron diffraction patterns, published in Russia, pertain to austenite. Small diamond crystals in "diamond cast iron" have been produced experimentally, but assertions of their formation inside graphite nodules in SG-iron at atmospheric pressure seem to be erroneous. An international quest into these problems is probably necessary.

THE STRUCTURE OF THE CEMENTITE PHASE IN THE CONSTRUCTIONAL ALLOYS ON THE Fe-C BASE

ZHUKOV A.A., SAVULYAK V. I.

EXPERIMENTAL RESEARCH FOR THE INVESTIGATION OF THE ACOUSTIC PROPERTIES OF SOUND-ABSORBANT MATERIALS

FORIS ANCA

The purpose of the paper is to fundamental a method for the measurement of some acoustic properties. Based on Kundt`s method established in 1902 and by using performant equipment manufactured by Bruel & Kjaer, we have developed a modern method of investigation. The properties that can be described are: absorption and transmissibility. The investigation was applied to some representative Romanian materials manufactured by Chimaltex of Targoviste. The results of the experimental research can be applied to the acoustic insulation of machine-tools.

EXPERIMENTAL DETERMINATION OF THE ACOUSTIC PROPRIETIES FOR THE "SANDWICH" STRUCTURE CONSISTING OF TEXTILE OFFAL COVERED WITH BITUMEN AND PVC

FORIS ANCA

Based on Kundt`s method established in 1902 and by using performant equipment manufactured by Bruel & Kjaer, we have developed a modern method of investigation. The properties that can be described are: absorption and transmissibility and the investigated material is a "sandwich" structure consisting of compact textile offal fixed between bitumen carpet and PVC foil. The results and the conclusions of the experimental research arc used for machine-tool acoustic insulation.

THEORETICAL INVESTIGATION PRINCIPLES OF SOME ACOUSTIC PROPERTIES OF SOUND-ABSORBENT MATERIALS OF ROMANIAN MANUFACTURE

FORIS ANCA

The paper presents the development of a measurement method of some acoustic properties of materials. Based on Kundt`s method of 1902 and by using performant equipment manufactured by Bruel & Kjaer - Denmark, a modern investigation method could be established, allowing for the characterization of material properties as absorption and transmissibility. This investigation was applied to some representative Romanian materials, manufactured by Chimaltex of Targoviste. The results of the experimental research find application in the acoustic insulation of machine-tools.

FACTORS INFLUENCING THE POLYMER FRAGILE - DUCTILE BEHAVIOUR

STAN GHEORGHE

Within any technological process, ductility means a key-factor in successful manufacture of parts. Knowing the behaviour of the material in dependence on of a series of factors: temperature, deformation speed rate, flowing stress, break stress, means mastering the technological processes. Also, the analysis of the influence of the chemical and physical structure on ductility, allows the knowledge and, sometimes, anticipation of several technological processes.

POLLUTION PREVENTION IN PROCESS DEVELOPMENT AND DESIGN

RAVEICA IONEL

Process development describes the refinement of a process concept from early conceptual stages (articulation of process objectives, selection of process steps, determination of constraints) through preliminary engineering (development of preliminary economic analysis, piping and instrumentation diagrams, and process flow diagrams). Process development is also understood to include experimental studies at the laboratory, bench-scale, and pilot-plant level. These studies are focused on obtaining key process information required to guide the remainder of the design effort and often take place concurrently with the conceptual design. Process development efforts can be oriented around new products, improvement of existing products, or increased utilization of available capital equipment assets (i.e., retrofit design).

CURRENT PROBLEMS REGARDING ENVIRONMENTAL PROTECTION IN THE PRODUCTION UNITS WITHIN THE MACHINES ENGINNERING

MĂCĂRESCU BOGDAN

In this paper we present the principals consideration development sustainable of machines engineering. Anything problem on machines engineering must by landing and from the point of view of impact this will have about medium.

CONCERNING ABOUT ENVIRONMENTAL PROTECTIONS

POPOVICI IRINA, POPOVICI RADU

The paper presents certain concerns about environmental protection on global scale and in our country

THERMIC BALANCE SHEET REAL SIMPLE AT DRIER FOR CEREALS

NEDEFF VALENTIN, MOŞNEGUŢU EMILIAN

In this paper we present dates necessary for elaboration thermic balance sheet real simple in a drier for cereals and measure or calculating measure or calculate elements who into in the these calculus of balance sheet. It exemplify big lost heat of a drier for cereals of his thermic output it is 0,28, of is not re-use hot air.

HUMIDITY INFLUENCE OF PARTICLES ON THERE SORT AFTER AERODYNAMICS PROPERTY

MOŞNEGUŢU EMILIAN, NEDEFF VALENTIN

in this paper we present humidity influence of cereals and leguminous plants particle for seed after specific hardness and floating speed critics on these six species and sort. Increase humidity of particle sends to increase values floating speed critics, respective process of separation to make worse after dynamics property of particles.

ASPECTS WITH ACTIVE LOOK AERATION AND DRYING CEREALS AND LEGUMINOUS PLANTS FOR GRAIN

NEDEFF VALENTIN, MOŞNEGUŢU EMILIAN

In this paper we present main want impose of drying cereals and leguminous plants for grain. Was analysed: dimension to chamber from drying and to the quantity with grain aeration in report with aeration productivity, degree of fill up to aeration chamber, the water volume from air atmosphere in report with real temperature and humidity, thermic working conditions and humidity extraction in function with product destination.

NECESSARY OF COLD CALCULUS FOR COLD DEPOT DESTINE APPEAL KEEPING

RUSU PETRICĂ, RAŢI IOAN, NECULAIASA VASILE

In this paper we present keeping condition of long time an appeal in depot foresee with cold cubicles. Was an element balance sheet present of cold power and cold necessary for end period (depot fill, cubicle respective) and for function in regime.

THEORETIC CONSIDERATION SIGHT FRUITS AND VEGETABLES PRESSURE IN SEEING NATURAL JUICE OBTAINES

RUSU PETRICĂ, RAŢI IOAN, MOŞNEGUŢU EMILIAN

In this paper we present the theoretic consideration sight natural juice out of fruits and vegetable press in seeing obtains. Was analyze of the base want impose press from obtain juice in fruits and vegetables and factory which influence pressure. In theoretic study operation of pressure is estimate with separation operation a heterogeneous mixture of the type solid-liquid.

DENSE FRUIT JUICES OBTAIN FROM BOX THORN FRUIT ON BREAK UP AND STRAIN MACHINE-TYPE PRESSING AND STRAIN DRUM

RUSU PETRICĂ, RAŢI IOAN, MOŞNEGUŢU EMILIAN

In this paper we present possibility to analyze of dense fruit juice separation on break up machine and type structure pressing and strain drum. Were presents theoretic and real outputs in case box thorn and raspberry remaking, into one or tow operation.

SUSTAINABLE DEVELOPMENT OF FOOD INDUSTRY IN CORRELATION WITH THE ENVIRONMENTAL PROTECTION

MĂCĂRESCU BOGDAN

In this paper we present the principals consideration development sustainable of food industry especially the equipment on food industry. Anything problem on food industry must by landing and from the point of view of impact this will have about medium.

THE POWER REQUIREMENTS OF THE AGITATOR

BIBIRE LUMINIŢA *, MARIN MARIUS **, MARIN CORINA ***

Pressure distribution through an agitated vessel cannot be applied directly to design, but one portion of the pressure distribution along the face of an impeller blade can be related to the power requirements of the agitator. This relationship comes form a description of the physical system.

THEORETICAL RESEARCH CONCERNING ON DIMENSIONAL ANALYSIS FOR FLUID AGITATION SYSTEM

MARIN MARCUS *, BIBIRE LUMINIŢA **, MARIN CORINA ***

Dimensional analysis converts a large number of geometrical, operational and physical variables into small number of significant groups that form the basis for design methods. The fundamental concepts of liquid motion and other transport phenomena establish a framework for agitator design. Although fluid agitation involves a large number of geometrical, operation physical variables, relatively small number of physically significant dimensionless groups can be established

BEHAVIOR OF FLUID VELOCITY IN AGITATED VESSEL

BIBIRE LUMINIŢA *, GURAMBA GHEORGHE **

Understanding the behavior of fluid velocity in an agitated vessel is as important as understanding power, since by definition agitation is the fluid motion produced by impeller rotation. This point is frequently misunderstood. The use of power, or power consumed per unit of volume, is often applied to characterize the degree agitation. In this article we explain why the same degree of fluid motion can be achieved with different power levels in the same vessel, and why less power unit volume is required for equivalent motion in large vessel as compared to small ones.

BLENDING AND BLEND TIME

GURAMBA GHEORGHE *, BIBIRE LUMINIŢA **

In a discussion of blending and blend time, a distinction must be made among the terms: blending, mixing and agitation. Blending refers to the intermingling, of miscible fluids to produce some degree of uniformity. Mixing involves the production uniformity between materials that may not be miscible (For miscible liquids, mixing and blending are synonymous). Agitation is the most general term, involving the production of fluid motion for blending, mixing, heat transfer, mass transfer etc.

A NUMERICAL STUDY OF UNSTEADY LAMINAR FORCED CONVECTION FROM A CIRCULAR CYLINDER

FLORESCU IULIAN, CĂLIMAN RADU

A numerical investigation of an unsteady laminar forced convection from a circular cylinder is presented. The Navier-Stokes equations and the energy equation for an unsteady incompressible fluid flow are solved by the finite difference method. The results are obtained at Reynolds numbers 100 and 200. The temperature field around the cylinder is obtained throughout the region of computation and is shown by isotherms at different times. The variations of the local Nusselt number around the cylinder at different times are computed and shown by graphs. The mean Nusselt number and the Strouhal number are also calculated. The computed results are compared with the other available experimental and theoretical results and are found to be in good agreement with them.

UNSTEADY MIXED CONVECTION HEAT TRANSFER FROM A HORIZONTAL CIRCULAR CYLINDER

FLORESCU IULIAN, CĂLIMAN RADU

A numerical investigation of an unsteady mixed convection from a horizontal circular cylinder is presented. The coupled basic equations of motion and energy are sohed for two cases: 1) Re = 100. Gr= 104 and 2) Re = 200, Gr= 5xl04. The velocity field and the temperature field around the cylinder are cxliibited by streamlines and isotherms at different times. The Strouhal number for the shedding of vortices in the wake of the cylinder is calculated. Figures have been drawn to show the variations of the local and the mean Nusselt numbers with time. The effects of the presence of free convection are discussed.

THE DISPLACEMENT OF THE EQUILIBRIUM STATE BETWEEN LIQUID AND VAPOUR PHASES OF ONE COMPONENT THERMODYNAMIC SYSTEM IN ELECTRIC FIELD

SAJIN TUDOR

Clapeyron-Clausius equation for two-phases one-component thermodynamic system in the case of its displacement from equilibrium state under the influence of the electric field is generalized. The displacement in the phase surface are caused by the essential non-homogenity of density and dielectric permitivity on the phase boundary.

THEORETICAL STUDY ABOUT THE SIMULTANEOUS IMPROVEMENT OF QUALITY AND PRODUCTIVITY IN LONGITUDINAL PAPER CUTTING - PART A

FLORESCU IULIAN, FLORESCU DANIELA

Cutting technology has developed rapidly over the last ten years. Today's technology allows faster cutting with better results, longer service life and shorter knife - related downtime.

THEORETICAL STUDY ABOUT THE VARIABLES IN THE SCREENING AND FRACTIONATING PROCESSES

FLORESCU IULIAN, FLORESCU DANIELA

Goal definition and plant analysis are necessary in order to decide whethrt to use the screening or fractionating process. This paper presented the effect of the proffile geometry on the screening and fractionating processes.

NUMERICAL METHOD OF CALCULUS OF THE PROPAGATION SPEED OF THE PRESSURE WAVE

TOPLICEANU LILIANA, PALOSANU GABI

The study present a numerical method of calculus of the propagation speed of the pressure wave on a constant section line. We use a systematisation of Jukowski's theories, elements of Riemann and G.Constantinescu studies for the pressure wave propagation. The fluid is considered barotrop. We use the equations of the continuity and move, the general equation of the fluid. In these case when the equation that define the movement have partials derivative still the second order, we use the finite-differences method for obtaining the algebraic relation associated and for the calculus of the speed, in specificated limits conditions and initials Cauchy's conditions

THE LABORATORY EQUIPMENT FOR DEEP DRAWING OF CIRCULAR, RECTANGULAR AND L-SHAPED PARTS

UNGUREANU VIOREL, BRABIE GHEORGHE, JUDELE ADRIAN

The computer simulation of deep drawing operations needs experimental data to validate the theoretical approach used to describe the material behavior during the plastic deformation of various sheet metals. This leads to the design of laboratory equipment for deep drawing of some representative's parts. For experimental determinations were chosen cylindrical, rectangular and L-shaped parts. The design of the equipment was cared out so that to allow the determination of as much parameters as possible independently of the press used.

NUMERICAL STRAIN MEASURING PROCEDURE TO DRAW THE FORMING LIMIT DIAGRAM AT NECKING FOR ALUMINUM SHEE

UNGUREANU VIOREL, PANOSCHI CRISTIAN, VACHER PIERRE, AHMED HADDAD

The paper deals with the application of a new method of necking detection and strain measurement based on digital image analysis used for the determination of forming limit diagrams at the necking of thin aluminum sheets. The two analyzed images usually correspond to the initial, unstressed specimen, and the image just before the necking. For pure a luminum sheets was established two situations regarding the onset of necking: one in the area where the planar state of deformation, and other where the biaxial extension is predominant. It is assumed that a transition's point characterized by the parameter s2 / s1 exists.

THE EXPERIMENTALLY DETERMINATED FORMING LIMIT DIAGRAM FOR ALUMINUM

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.

THE APPLICATION OF NONCUADRATIC HILL'S CRITERIA TO THE FORMING LIMIT STRESS DIAGRAMS USING FORMING LIMIT DIAGRAMS DETERMINATED EXPERIMENTALLY

PINTILIE GHEORGHE, ISAC SORIN

The manufacturing of sheet metal using cold deformation has been developed quickly and has an huge rate of growth especially in aeronautics and automotive industry because the possibility to manufacturing complex forms of products. In this sense in last decade the scientists are focused on the more exactly describing and phenomena approximation of sheet metals cold deformation capacity and the implementing of technical processes. For this goal the design of Forming Limit Stress Diagram play an essential role. The design of F.L.S.D. depends on strains and has importance because eliminate the deformation path. In the papers are presented as samples the data gathered for aluminum sheet metals.

A MANUFACTURING PROCESS FOR THE INCREASE OF THE DEFORMATION CAPACITY OF THICKNESS SHEET-METAL

PINTILIE GHEORGHE, ISAC SORIN

Present paper presents an unconventional process for the increase of the deformation capacity of the sheet metals. Knows that by rolling the mechanical characteristics and the elasticity of sheet metals are changed according with the angle directions of plasticity deformation, the anisotropy coefficient having various values. Using this process the unarranged crystalline structures become arranged ones which assure a good uniformization of the crystalline structure and constant anisotropic coefficient. Using this process we gain a growth of the deformability capacity of the sheet metals.

DESCRIPTION OF THE CONTACT BETWEEN A DETERMINISTIC ANISOTROPIC TOOL SURFACE AND A WORKPIECE SUBJECTED TO PLASTIC DEFORMATION

RAVEICA IONEL, SCHNAKOVSZKY CAROL

The finite element method offers an opportunity to obtain important information by simulating metal-forming processes. The description of the tool-workpiece interaction still remains a critical issue. The aim of this paper is to describe the contact between a deterministic anisotropic tool surface (grooved) and a workpiece. This is done by means of an existing contact processor and a friction law that has been conceived to describe sliding friction. This compromise solution of describing a contact state near to sticking by means of a law created for sliding friction is investigated. The results obtained using a macrogeometric model of the grooved surface are compared to those achieved by an idealized smooth surface and different friction coefficients. Next, an anisotropic model is introduced and calibrated using the inverse method based on the ring upsetting test for a hot-worked steel.

THEORETICAL AND EXPERIMENTAL RESULTS OF THE ELASTIC-PLASTIC RESPONSE OF A CIRCULAR ROD SUBJECTED TO NON-PROPORTIONAL COMBINED TORQUE AND TENSION LOADINGS

RAVEICA IONEL, SCHNAKOVSZKY CAROL

Experimental and theoretical results concerning the elastoplastic response of a circular steel rod subjected to non-proportional biaxial loadings are reported. The following loading paths were studied: elastoplastic torsion followed by tension, keeping the initial angle of twist constant, and elastoplastic tension followed by torsion, holding the initial axial displacement constant. Experimental results show that when the rod is initially subjected to a torque and then, keeping the corresponding angle of twist constant, to a gradually increasing axial load, the rod behaves as if its torque-carrying ability has been drastically reduced without in any way affecting its axial load-carrying ability. Similarly, when the rod is initially subjected to an axial load and then, keeping the corresponding axial displacement constant, to a gradually increasing torque, the rod behaves as if its load- carrying ability has been considerably reduced without in any way affecting its torque- carrying ability. The mechanisms of such reduction are discussed in relation to the theoretical predictions based on Gaydon's [1] analytical model. Numerical solution has also been obtained along the tines of the above-mentioned model. The findings of this work have a direct bearing on the relaxation of tightening torques or axial loads as experienced by critical engineering components, such as couplings, bolted joints and rotating shafts, that are subjected to similar types of biaxial loading.

METHODS AND TEHNICAL SOLUTIONS APPLIED TO IMPROVE THE PROTECTION OF THE MACHINE-TOOL OPERATORS

BRABIE GHEORGHE, CHIRIŢĂ BOGDAN

A machine tool of quality, must recomplish certain social requirements concerning the production of the environment or of the machine operator. The paper presents the main methods and technical solutions, which can be applied by the machine designer, manufacturers or users in order to improve the operator protection.

METHODS FOR INCREASING THE PRECISION AT HIGH PRODUCTIVITY MACHINE TOOLS

GHENADI ADRIAN

In general, many processes arc required to produce precision dies and molds, including cutting electrical discharge machining, grinding and polishing. In particular, since cutting with small-diameter tools on current machines is difficult for extra-small precision dies and molds, productivity and precision are extremely low. This research project involved the creation of new machining technology for use of small-diameter tools, and the development of machine tools capable of streamlining the machining processes while maintaining consistent quality, with the ultimate, with the ultimate goal production efficiency of between two to five times for actual machining applications, with efficiency being boosted over tenfold on application most suited to the new technique.

METHODS AND TECHNICAL SOLUTIONS APPLIED TO IMPROVE THE ECONOMICAL FEATURES OF UTILIZATION OF THE MACHINE-TOOLS

BRABIE GHEORGHE

In the operating stage, the machine tool must achieve an adequate production in the conditions of a low cost. By this point of view, in all the phases of the machine achievement and service must be adopted the best technical solutions in order to obtain optimal economical features of its utilization. The paper presents the main methods and technical solutions which can be applied in order to improve the machine tool productivity, coefficient of utilization and maintenance.

MODELING OF ELASTICIY MOUNTED VERTICAL SPINDLE

GHENADI ADRIAN

The evaluation of the dynamic behavior of a rotating system on a machine tool is possible by means the modal parameters. A mixed and experimental approach is used to identify the modal parameters of a specially-designed test rig The modal identification os done both for nonrotating as well as rotating systems. These modal parameters are used to validate a developed Finite Element. It is the aim of this paper to identify the modal parameters of the rig in several stages if its mounting on the test stand. In the case, the modal parameters provide us the necessary information to adjust gradually the mathemathical model.

THE INFLUENCE OF THE TOOL CLAMPING MECHANISM TO THE PRECISION OF MACHINE TOOLS

GHENADI ADRIAN

To implement new concepts about reliability and precision, a new machine had to be developed. It is necessary to provide this machine with feed axes, and a spindle with an absolute minimum of vibration. The features of this machine are described below.

SOME ASPECTS CONCERNING THE UTILIZATION OF THE NONCONVENTIONAL MATERIALS FOR THE STRUCTURAL ELEMENTS OF THE MACHINE TOOLS

CHIRIŢĂ BOGDAN

The traditional materials used under different forms in machine construction, the cast iron and the steel, have been studied along the time, so that nowadays their characteristics are well known. Technological problems that cannot be properly solved using these materials, as long as other problems, have determined researchers from the machine construction field to seek for new materials that should replace the classic ones.

COMPACTAREA LA RECE A PULBERILOR METALICE NANOGRANULARE

GEAMĂN VIRGIL*, GEAMĂN LUCICA**

In this paper is presented a new cold consolidation technique that can produce high density, high hardness compacts from ball-milled powders. Cold compaction of bcc- Fe and fcc-Fe alloys was accomplished statically and dynamically by cold isostatic pressure, CIP, and cold dynamic compaction, CDC, respectively. The paper presents some experimental data obtained during these techniques are also presented.

NOI ASPECTE PRIVIND FINISAREA ELECTROEROZIVA A MATRITELOR

GEAMĂN LUCICA

The paper deals with the influence of the chemical compounds of the material to be machined upon the electrode wear at electrodischarge machining. It is presented the process of carbon precipitation on the electrode surface because of the catalytic action of the chemical elements from tlie steel. Some experimental results are also presented concerning the electrode wear at machining of steels with different compositions.

NOI ASPECTE PRIVIND OBTENEREA PALETELOR PENTRU ROTORII TURBINELOR HIDRAULICE

GEAMĂN LUCICA

The present work deals with production of turbine rotor blades for hydro-electric plants, made from T8NiCrMoSil30 steel trade mark. Different methods of heat treatments have been tested on samples and it was proved that the mechanical properties have complied with the requirements.