No. 3 ( 1997)
Articles
COMPUTER-AIDED DESIGN OF THE COMPLEX PARTS IN THE MACHINES BUILDING FIELD
BIRIŞ SORIN
Within the framework of this article, the concept of parts computer-aided parameterized design is presented. A methodology is developed of analytical description of the complex surfaces of the parts in the machines building industry. An original mathematical model is afterwards identified for the analytical description of the active surface of one of the most complex shape in mis field, the one of the plow moldboard. An AutoLISP program was developed for the design and display of any type of moldboard, using AutoCAD Release 12, the most wide-spread CAD program presently existing in Romania. The moldboard model thus generated can be easily converted and exported for the finite-element analysis in NASTRAN, ANSYS etc. with a special view on optimization.
UNFOLBED PROFILES OF THE MULTISPINDLE AUTOMATIC LATHE`S CYLINDRICAL CAMS
CATRINA DUMITRU, CROITORU SORIN MIHAI
Cylindrical cams of the multispindle automatic lathe drive the radial and axial slides of the lathe by means of lever mechanisms and are made of thick metal sheet segments, folded on cylindrical drums of the command shaft. Passing from high speed, of the slide to its low speed is made by means of connecting radiuses on the unfolded profile of the cam. As a result, an acceleration of the slide occurs. In the paper, the relationship between slide`s acceleration, connecting profile radius and drum`s radius is underlined.
CALCULUS ELEMENTS FOR RING NECK FLANGES
IATAN RADU, ALAMOREANU ELENA, IORDAN NICOLETA, CHIRIŢĂ RĂZVAN
The paper present a new method using short structural elements as plane ring plate type, for the evaluation of induced stresses in flange assembly. Are taken into consideration both the external loads (given by inside pressure, temperature, and other uniform axial forces) and simplifier hypotheses from revolution cover. The exemplifications of theoretical results are developed on a flange made in Germany and another made in Romania, using an adequate program.
THEORETICAL AND EXPERIMENTAL CONSIDERATIONS ON THE INFLUENCE OF THE AXIAL FORCE TO THE CRITICAL ROTATIONAL SPEED OF THE SHAFTS FOR MIXING DEVICES
BIBIRE LUMINIŢA
Theoretical computation of the own frequency doesn`t take into account the damping effect of the mixed liquids, the effect of the axial toad, the elasticity of the bearings, etc. So, the real own frequency will be obtained through the correction of the theoretical own frequency by the aid of some correctional coefficients which depend on the influences of the effects of the factors which were previously shown. The paper is presenting theoretical and experimental views about k,, which introduces in theoretical formula of real own rotational speed, the influence of axial force.
A METHOD CONCERNING OFTMISATION OF ESTABLISHING OF THE, SUPPORTS POSITION OF THE ROTATING SHAFTS FOR MIXING DEVICES, WITH A VIEW TO REDUCING THE FLEXION VIBRATIONS
BIBIRE LUMINIŢA
specification that it doesn`t exist a un the study of vibration behavior of the shafts for mixing devices has some deficiencies because the computation of the shafts of these apparatus takes partly into account the real stresses. It is necessary to make the specification that it doesn`t exit a unitary methodology for computation of this kind of shafts. Praising the influence of the bearings on theoretical own frequency, authors make an optimization compution of the length of the distance between the supports of the bearings. The obtained formula and the corresponding diagrams can be used by the mechanical engineers on design work, in the field of mixing devices.
OPTIMIZING THE PRE-LOADING FORCE OF BALL SCREW NUTS AND BEARINGS, USED ON NUMERICAL CONTROL MACHINE TOOLS
STAN GHEORGHE
The setting of the pre-loaded force of ball screw nuts and bearings as elements of the feed kinematic linkage of the numerical control machine tools, has been done on a mathematical basis that eliminates the optimal pre-loading rate be constructed in different ways. This is possible after determining the aspect of the force deformation curve and its approximation to a curve that can be expressed analytically.
THE STUDY OF THE SWELLING PHENOMENON IN THE CERAMIC PASTES WHEN THEY PASS THROUGH AN ANGULAR SECTION
IORDACHE GHEORGHE, PASAT GHEORGHE
The extrusion of the ceramic casting cores requites the knowing of the value of the discharge product swelling in order to correct adequately the form of the extrusion head for the compensation of this phenomenon. On basis of the experimental determinations of the swelling phenomenon through annular capillary tubes, the variation curves of the swelling coefficient have been plotted, depending on the shearing stress for two values of the humidities (w = 40% and w = 45%). The results obtained for the respective phenomenon, determined in another paper, for capillary tubes with full circular section, have been studied.
ON-LINE MEASUREMENT OF HARDENING DEPTH USING ULTRASONIC BACKSCATTERING AND MAGNETIC BARKHAUSEN NOISE
PASAT GHEORGHE
The aim of this paper is to present the theoretical principles of two new technique propose by Fraunhofer Institute for Non-destructive Technique from Saarbrucken – Germany. The ultrasonic backscattering technique is a powerful tool for nondestructive determination of the hardening depth in introduction hardened components. It allows one to measure the depth of the heat affected zone because the welding procedure or the heat treatments. This technique can be applied to hardening depth in the range = 2 mm and the typical measuring accuracy is ± 0.4 mm. The advantages of this method is the on-line measurements and that is no special calibration required. The magnetic Barkhausen noise technique is based on the different microproperties of the structure of the ferromagnetic steel after a complete magnetisation. The signals are detected by a tape recorder heads or by small coils, which exhibit the voltage induced by the discrete change of the field orientation. If the interaction depth reaches deep enough, signals from different microstructure states hardened surfaces above, a tough ground material lead to a multipeak structure in M (H). Finally, the author presents some experimental results obtained during a shot practice stage at the Fraunhofer Institute for Non-destructive Technique.
STUDIES CONCERNING THE CHANGE OF THE INITIAL CONFIGURATION OF THE BARS IN THEIR AXIAL DIRECTION DURING TORSION
BRABIE GHEORGHE
One of the most important effects of torsion, which can be used in many technical applications is the modification of the initial configuration of bar. Relating to this effect, the theories of the Mechanics and Strength of Materials reffer, only, to the helical orientation, of the generatrixes of bars and the warping of the noncircular cross-sections. The present paper analyses the changes of the configuration of bar in its axial direction plastic torsion.
A FINITE ELEMENT STUDY OF PLAT ROLLING
CRISTEA ION
Using an Eulerian formulation a finite dement solution for the flat rolling problem is presented. Calculation are performed to establish the effect of roll deformation and of the variation of the coefficient of friction in the roll gap on the predictive capabilities of the model. Comparison to data of Ai-Satahi et al. (1973) and Shida and Awazuhara (1973) indicated that the differences between measurements and calculation decrease when the above - mentioned effects are accounted for.
A NEW MANUFACTURING TECHNOLOGY OF MOULDS FOR PLASTIC MASS INJECTLON
SPOREA ION, BOTIS MIHAELA, SPOREA OVIDIU
In this paper is presented a new technologies for using the dies (moulds) for plastic mass injection by casting by nonconventional procedures, which is more simple and economical than the processing by classical technologies.
TECHNOLOGY OF PRODUCING POLYTETRAFLUORETHYLENE ARMED FLAX FILTERS
SIMIONESCU GHEORGHE, BELLU L. A., BULULETE C., CAZAN A. M., DESPA L.
Porytetrafluoroethylene armed flax filter is used in chemical industry and medicine to filter the strong corrosive fluids having maximum temperature of 250°C and is made up of two metal rings completely coveres by a compact polytetrafluoroethylene coating, the rings being situated at the ends of the filter, containing in between a porous flax/tube made of grains oi polytetrafluoroethylene and a number of metal bars completely covered by a compact polytetrafluoroethylene coating.
CONTRIBUTIONS AT INTRODUCING THE EUCLID-LANGUAGE IN WORKING ON FIVE OPERATED AXES
BAILA NEAGOE AUGUSTIN
The industrial experience obtained in the working of models, moulds and big size patterns at working centres on three operated axes led to the conclusion that for complex surface pieces (3 D) it is economically and technologically important to pass to the working on five operated axes. This paperwork offers studies made by technologists in order to modify the programming language and the computed equipments depending on the new volume of geometrical and technological information, characteristic for the working on five operated axes. Finally, it is shown that the necessary investments are not very expensive and thus the new technology becomes profitable in all cases.
COMPUTER AIDED RESEARCH OF THE DYNAMIC BEHAVIOUR OF THE TRANSLATION MODULES OF INDUSTRIAL ROBOTS WITH CONTINUOUS CURRENT ACTUATOR
OLARU ADRIAN, NICULAE MIHAI, CHIRIŢOIU RADU
This paper la emphasising the way in which can be obtained and fitted the completely mathematical model of the servoelectrical continuous current actuator, for a translation ground module, using computer aided research with data acquisition. The experimental research is followed by the simulation and optimization of the dynamic behavior on the experimental validated model, introducing electronic option filters of delay, anticipation or first order of inertia.
THE CHOICE OF RIGHT TOOL CHANGER
GHENADI ADRIAN
When a machine needs new tools, there are many ways to replenish storage magazines- that is, add and subtract tools- while the machine is operating. Techniques include loading them manually to the storage magazine, using an automatic loader, and adding them using the spindle. To decide which style of tool changer is best of your jobs, the advice is to look at the economics and to choose the simplest mechanism that offers the necessary tool change time, tool storage, weight capacity and reliability.
ABOUT THE MODERN DES1GN OF THE CAMS FOR AUTOMATIC TOOL CHANGER
GHENADI ADRIAN
ATC is an important component of MC. ATC made up of interacting cams mechanism is a king of advanced device. In this device, several cams are installed on one main controlling axle. In changing tools, each cam drive mechanical hand performs some actions. Some actions may perform in same time. Suitable cam carves and interacting cams on one axle can make tools changing more quick and reliable. For this reason, many MC consider ting cams mechanical ATC in design. In this paper, we will discuss some problems about design ATC. Using computer to analyze and calculate in design % gain better results for improve the acting property of ATC.
MATHEMATICAL MODELLING AND COMPUTER OPTIMIZATION OF-THE CYLINDRICAL MULTILAYER SHRINK-FIT CONSTRUCTION FOR HIGH PRESSURE
CRISTESCU CORNELIU, ZAHARIA VALERIU, BĂLAN CIPRIAN
This paper is subject to mathematical modeling of the cylindrical multilayer shrink-fit construction for high pressure, which are needed for modern plastic deformation technologies conception. There are presented the graphical results obtained by a special computer program which optimizes the shrink-fit construction, in order to gel on uniform stress distribution and to use properly the material.
SOME RESEARCHES REGARDING THE INFLUENCE OF VARIOUS PARAMETERS ON THE STIFFNESS OF THE HYDROMECHANICAL POSITIONING SYSTEMS
TIŢA IRINA, ZETU DUMITRU
The accuracy of hydromechanical systems used for the positioning is of high interest. The stiffness of the system must be known, especially when there is a variable load. This paper describes the structure of the computing modules which is configured on the computer for the purpose of revealing the influence of various parameters on the system's stiffhess. The model was subjected to a programmed step load and the systems' answers are presented in this paper. On the basis of this answers one may say which the influence of each parameter is.
ABOUT OF THE PERMANENT AXIAL SYMMETRIC FLOW IN A CASE OF COMPRESSIBLE FLUIDS AND OF A VARIABLE SECTION
TOPLICEANU LILIANA, CAZACU MIRCEA-DIMITRIE
This study presents die flow of a compressible fluid in a case a variable section and use the equations of the continuity, move and the general equation of gas, in these particular case. Using numerical method for resolution of the set of equations which characterizes the flow we obtain the expressions of speed and static pressure.
MATHEMATICAL MODELLING AND COMPUTER SIMULATION OF THE WATER COOLING PROCESS FOR THE HARDENING OF THE SPHERICAL SHAPE PIECES
CRISTESCU CORNELIU, ZAHARIA VALERIU, BĂLAN CIPRIAN
This paper presents a simulation program of the water cooling process for spherical pieces, based on a mathematical modeling which uses known relations from references, the theoretical results being confirmed by experiments.
THEORETICAL CONSIDERATION ABOUT THE CHOOSING OF THE DRYING METHOD AND EQUIPMENT OF VEGETABLE'S RAW MATERIALS FOR DECREASING THE EXPENDITURE OF ENERGY
NEDEFF VALENTIN, RAVEICA IONEL
This paper including some theoretical aspects looking the drying proceeding, method and equipment choosing of vegetable's raw materials for the expenditure of energy decreasing, necessary for drying agent producing in concordance with destination of product and his humidity for equilibrium On have the possibility to important energetically economies through the drying proceeding's and operating equipment's optimization
THE INFLUENCE OR MAIZE GRAINS’ HUMIDITY ON THE QUALITATIVE VALUES AT CORN COBS THRESHER
NEDEFF VALENTIN, RAVEICA IONEL
In this paper the author presents the experimental results regarding the influence of maize grains' humidity on the qualitative values at corn cobs thresher. The optimal grains' humidity; has the current values enclosed in the interval 23-27 % for a beating working condition with lower energy consumption and for qualitative working values enclosed in admissible corresponding intervals.
METHOD FOR IMPROVING THE DURABILITY QF THE TOOLS USED TO CUT THE PAPER
POPOVICI RADU, CIUCESCU DORU, CHIRUTA RADU, SICOE EUSEBIE, BOCSANEANU NELA
There are many methods to improve the durability of metal products which usually refer to the modification of the structure, composition and properties of thin lagers by alloying the surface or by alloying and deposition of some special materials. The method of vibrating electrode metal (MVE) is considered as a improved variant of the method of depositing by voltaic arc. This paper presents the results obtained during the putting in practice of this method at Letea Co, Bacau,
TECHNOLOGY TO OBTAIN THE REINER DISCS
POPOVICI RADU, SIMIONESCU GHEORGHE, CIUCESCU DORU, HAGIU ILIE, CHIRUTA RADU, SICOE EUSEBIE, BOCSANEANU NELA
The refiner discs are very strong solicited at friction wear and sometimes, when the raw material is missing - to shocks. Before, these pieces were made completely from cast steel, though, the original Swedish pieces were manufactured from gravity die cast nodular iron. This paper presents the results obtained at LETEA Co. Bacau by a new technology which treats the gravity die cast nodular iron by nitriding,