No. 4 ( 1998)

PATH CONTROL AND MODELLING OF NON-HOLONOMIC WHEELED MOBILE ROBOT

NITULESCU MIRCEA

In previous work, a path tracking control system developed for autonomous differential mobile robot driven by wheels is described. In conventional approaches, the trajectory is usually planned by smooth curves with curvature-continuity and a path tracking controller is designed to compensate the path error occurring in the navigation. If large path error occurs, the algorithm often causes unpredictable tracking motion. This paper presents a bang-bang path tracking algorithm by which smooth and stable motion could be obtained even for the path given by simple combination of straight lines or circles. To investigate the performance of the control system, a series of experiments was conducted using a PC for the case of a differential mobile robot.

IMPLEMENTING QUALITY IMPROVEMENT PROGRAMMES

CRISTEA ION, APOSTOL MARIAN

Much has been written about Total Quality Control (TQC) and the need for companies to practice the simple, obvious, business logic of TQC. But for many years, far too many Western manufacturing organizations have adopted the traditional approach to quality control, i.e. inspecting the product after it was built and carrying out any necessary re-work before dispatch to the customer. This was in the hope of achieving quality by "inspecting the quality in," a grossly inefficient and wasteful strategy.

REZIDUAL STRESSES AND EQUIVALENT STRESSES ON BALL SCREWS

PUIU VASILE, CRETU S.

The calculation of the optimal residual and equivalent stresses within the rolling theory is an important issue. The determination of their rates leads to obtaining an increased durability of contact. These rates are also needed for durability experimental determinations. The problem can be applied particularly on ball screws.

RESEARCHES AND EXPERIMENTS ON THE USAGE OF MATERIALS FOR BALL HELICAL TRANSMISSION MANUFACTURE

PUIU VASILE

The rational usage of steel for manufacturing ball helical transmissions is an important issue in designing these complex assemblies, with relevant economical consequences. In particular, for the carrying elements (screw, nut, balls), the materials should be carefully chosen. This work justifies, based on experimental tests, the usage of the quality carbon steel, type OLC55X - STAS 880-80 for ball screws.

SIMULATION OF AN AUTOMATIC ELECTROHYDRAULIC SYSTEM

SOAITA DUMITRU

Actual tendency in study of automatic system's performances, tendency which is followed in present paper, is to use models with matricial-vectorial equations with state variables. These equations are a result of modelling with differential equations and are resolved using numerical methods and computer simulation. Further on it is presented theoretical research's methodology by computer simulation of dynamics of automatic positioning system. Response's simulation of automatic feed system assumed, in the beginning, to establish its mathematical model.

THE MODELING OF AN AUTOMATIC HYDRAULIC SYSTEM

SOAITA DUMITRU

Structural-functional model of automatic electrohydraulic systems was obtained from an ensemble of algebraic and differential equations, which describes output measure depending in time by input measure. When these equations were wrote it was analysed dynamic behavior of each system's clement. Also, was considered the direction of information’s circulation, so the output value for an element is the input value for following one. During the modelling it was used some acceptable simplifying assumptions, in order to simplify theoretical model, but avoiding losing the essence of the process. Mathematical model used to describe the dynamics of electrohydraulic feed servomechanism, unlike functional "input-output" models, is a richer in content and more realistic “structural- functional" representation.

ABOUT THE PRESSURE WAVE PROPAGATION IN A PIPE

TOPLICEANU LILIANA, VIZITIU GABRIELA

The study presents the damping of the pressure wave in a case of viscous fluid on a constant section line. We use a systematisation of Jukowski 's theories, elements of Reiman and G. Constantinescu studies for the pressure wave propagation. The fluid is considered barotrop and viscous. We use the equations of the continuity and move, the general equation of the fluid. In the case of unidimensional movement, we considered the influence of the viscosity beeing made by the friction between molecules. We use Bernoulli and Euler's method in specificated limits conditions and initials Cauchy's conditions and we present the damping of pressure wave.

SOME ASPECTS CONCERNING THE FREQUENCY VARIATION AND FLOW TO HIGH-FLOW PUMP

FLORESCU IULIAN, FLORESCU DANIELA

The paper presents an analytical and graphical method which can be used to the determination of the frequency variation in the case of the High - Flow Pumps. The knowledge of these problem permits to establish the relationship between frequency and flow.

SOME ASPECTS CONCERNING THE LOCATION AND STANDARD GUIDLINES TO HIGH-FLOW PUMP

FLORESCU IULIAN, FLORESCU DANIELA

The new products are the motor of the industrial competition in Romania. It is ever more clear that the competition parameters like cost price and quality, the prelevant parameter remains the time and cost. The paper presents the standard guidelines which depends on the flow id location of HF Pump.

TEORETICAL STUDY ABOUT THE HIGH-FLOW PUMP

FLORESCU IULIAN, FLORESCU DANIELA

High-Flow Pump are the submersible propeller pumps that are monted horizontally within the liquid. This pumps are designed for pumping large volumes of contaminated water against low heads. The safe and efficient operation of the pump depends particularly on its proper its proper installation and on having a suitable pipe configuration. The study presents loss conculation values and general advice for the pump selection. The pump performance curve help the designer to select the correct pump and propeller

TURBULENT TRANSPORT TO A ROTATING CYLINDER FOR LARGE PRANDTL OR SCHMIDT NUMBERS

FLORESCU IULIAN, CĂLIMAN RADU

The heat or mass transport to a rotating cylinder is obtained by solving the conservation equations for large Prandtl or Schmidt numbers. A modified mixing length, which includes the effect of centrifugal forces in terms of the Richardson number, is used. Explicit relation are presented for the heat or mass transport and a comparison is made with the experimental data over a range of Prandtl and Schmidt numbers from 190 to 11.000.

THE OFFALS STRUCTURE AND THE VALORIFICATION TO A RESEARCH AND DEVELOP UNITY WITH AGROZOOTEHNICALY PROFILE

NEDEFF VALENTIN, RAVEICA IONEL, MOŞNEGUŢU EMILIAN

In this paper we present the offals structure and the possibilities to their utilization into a research and develop unity with agrozootehnicaly profile. The actual utilization realizes acceptable rudological and ecological balance sheet, but with a very low level for economical balances sheet. On can obtain profits with a superior utiliazation for all offals from respective unity.

THE INFLUENCE OF SOIL PROCESS ON SOME PHYSICAL AND PHYSICO-MECHANICAL PROPRIETIES OF THE SOIL

NEDEFF VALENTIN, RAVEICA IONEL, MOŞNEGUŢU EMILIAN

This paper present the immediate and remnant modifications that are produced in soil under this system of works influence. After the working process of soil effectuated in a five years period on three depths, the physical proprieties have an important influence.

CONSIDERATIONS ON PRIMARY PROCESSING OF BAKERY WHEAT

MOŞNEGUŢU EMILIAN, NEDEFF VALENTIN, RAVEICA IONEL

In this paper we present the bakery wheat primary processing possibilities. The technological process of primary processing can be selected in function of the quality indicators obtained for wheat, after harvesting and can influence the costs and finally quality of bakery wheat.

THE QUANTITY AND QUALITY OF POTATOES TUBER AND THE ENERGY CONSUMPTION ALLOTED IN CRAP TECHNOLOGY

MOŞNEGUŢU EMILIAN, NEDEFF VALENTIN, RAVEICA IONEL

In this paper we present the influence of energy consumption on the quality and quantity of potatoes tuber. The energy consumption represented by the energy values for all working process, winch is, effectuates in crop technology. On the base of presented correlation are the results from 30 crop technologies applied into a six years period.

PERIMENTAL RESEARCH OF OPEN WEARING OF SHAPED BARS

SAVCHINSKIY I. G.

In this paper the outcomes of an experimental research of open wearing of shaped bars arc represented. In an outcome of these researches is established, that by open wearing of shaped bars it is possible to receive trumpet and hollow shaped bars of a various degree of complexity for needs of a mechanical engineering.

INFLUENCE OF COOLING SPEEDS IN THE MARTENSITE MORFOLOGY FROM WELDED CRYOGENIC STEELS

SPOREA ION, BUDAU V.

The parameter that must to be taken into account at the estimation of the behavior at welding of the steel with 9% Ni is the cooling time t8/5 that has to be correlate with the linear.

TOWARDS INSTRUMENT-ORIENTED CALIBRATION OF CMMs

CRISTEA ION, GEAMAN VIRGIL

The calibration of CMMs has become a more and more important matter of investigation and discussion stimulated by the increasing demand of calibration in manufacturing. CMM errors are very complex to describe in simple terms suitable to be stated in a calibration certificate; even more complex is the evaluation of uncertainties of these errors and of their combination. This paper proposes methodology which enables a simple representation of CMM errors of scale factors, and of their uncertainties in terms of binomials, intended to meet the requirements of brevity and simplicity of a calibration certificate.

THE REACTIVE SINTERING PROCESS

GEAMĂN VIRGIL, CRISTEA ION

Reactive sintering has been utilized in this study to reduce open porosity and consequently improve corrosion properties of P/M stainless steel. Elemental Ni, Fe and Al powders have been added to standard 316L powder. Under carefully controlled conditions these powders react forming a transient liquid phase which fills pores. Microstructural analysis of the reactively sintered materials revealed no interconnected porosity with the pores which were still present being isolated and rounded. Differential thermal analysis shows that the reactive sintering process is initiated at the first Ni-Al eutectic which occurs at 640°C. Results indicate that reactive sintering is sensitive to process variables such as powder size, addition levels and mix homogeneity. This paper describes some of the mechanisms underlying the reactive sintering process.

THE EFFECTS OF DIFFERENT FACTORS ON THE FORMING LIMIT DIAGRAMS

BRABIE GHEORGHE, CHIRIŢĂ BOGDAN

The level and shape of the FLD depend on many and different factors. The experimental investigations point out that the prediction of die plastic instability depends on the sheet thickness, the strain path, the strain rate, the material properties and the used constitutive equation. This study is devoted to analyse the influence of the basic material properties and forming conditions on the level and shape of the FLD.

OPC – AN EMERGING STANDARD FOR MANUFACTURING DATA COLLECTION

GEAMĂN VIRGIL*, CRISTEA ION**

The paper presents some technical data for process control in automation. There are given details for manufacturing data collection in order to develop the implementation of new software in automation processes.

INFLUENCE OF THE MATERIAL PROPERTIES AND PARAMETERS ON THE FORMING LIMIT STRESS DIAGRAMS

BRABIE GHEORGHE, UNGUREANU VIOREL

The level and shape of the FLSD are dependent on many factors, which in principle should be the same with the factors that influence the FLD. These factors can be grouped as follows: • the material properties and parameters: work hardening coefficient, initial value of heterogeneity, initial anisotropy, a.s.o. • the experimental conditions: strain rate, strain paths, a.s.o. In this study, the influence of the material parameters and properties is analysed.

INFLUENCE OF THE EXPERIMENTAL CONDITIONS ON THE FORMING LIMIT STRESS DIAGRAMS

BRABIE GHEORGHE, PINTILIE GHEORGHE

The level and shape of the FLSD are dependent on many factors, which in principle should be the same with the factors that influence the FLD. These factors can be grouped as follows: • the material properties and parameters: work hardening coefficient, initial value of heterogeneity, initial anisotropy, a.s.o. • the experimental conditions: strain rate, strain paths, a.s.o. In this study, the influence of the experimental conditions and selected yield criterion are analysed.

CONSIDERATIONS ON RHEOLOGICAL ISSUES AT PHENOMENA WITHIN THE PROCESS OF ELASTOMER INJECTION

STAN GHEORGHE, GAVRILIUC OVIDIU

Despite the difficult problems it raises, the technology of elastomer injection goes on expanding, in terms of usage and, improvement is intended, in the following three main directions: • improvement of the positions • optimization of the technological parameters • development of new technological variants Among the technological variants the injection is critical just on exploiting the rcological behavior of the elastomer compositions.

SPECIFIC ISSUES OF THE CAPSULATED MIXING RHEOLOGY

STAN GHEORGHE, GAVRILIUC OVIDIU

It is know that the reological characteristics of the elastomers determine their processing capacity, also under the form of composition, in unitary basic processes, such as: rolling, mixing, injection, which are distinguished, in rheology terms, by flow phenomena and behavior at variuos stress, of whom prominent is the shear stress.

NEW CLASSES OF CASTING MATERIALS - WEAR RESISTANT

CHIRA ION

Ferrite (Fea - alpha irons with cubic body-centrred lattice) is either a free metaliographical or a bound one as a main component of manifold casting materials. The ferrite hardening by alloying and strengthening processes ieads to the so-called "Consolidation Process" which is important in the filed of usage hardness casting alloys, especially. The paper reported here refers to different sort of materials to which the ferrite consolidation took place by nitrogen microalloying and by boron - titanium modification, as follows: • Grey cast iron for machine tools (working machines); • High chromium white cast iron both for balls and armours of crushing ball mills; • Hypereutectoid steels (ADAMFT type) for rollers.

STUDIES CONCERNING THE IMPROVEMENTS OF CONSTRUCTION AND FUNCTIONING PARAMETERS OF ALUMINUM ALLOYS HEAT TREATMENT FURNACES

MINEA ALINA-ADRIANA

This paper presents a constructive solution for a heating furnace used at heat treatment of aluminum alloys. Therefore, i choosed a typical charge of parts for studieing the heating equipment. The studies that I have done can reveal the advantage of using the ceramics for furnace insulation. In this paper I propose a modified form of the work chamber and some new solutions for some parts of the furnace, in order to provide a higher temperature uniformity (±2°C) in the furnace.

MODERN SYSTEM FOR HEAT TREATMENT ASSISTED BY COMPUTER

VIZUREANU PETRICĂ

The using of the adequate systems for adjustment of the electric furnace parameters with resistors is a task with economical and technical implications. One of the most important economic implication is: a leading system for electric furnace with resistors, assisted by computer is the best way today in Romania to save more energy.

STUDIES ABOUT SOME WROUGHT ALUMINUM ALLOYS

MINEA OVIDIU

This paper presents some studies about a few wrought aluminum alloy in order to improve the heat treatment technology. Therefore, I presented some experimental results of microhardness, structure and microstructure of two wrought aluminum alloys. Also, I made the theoretical curves of final heat treatment at these alloys.

NEW TECHNOLOGY OF HEAT PIPE HEAT RECOVERY SYSTEMS CONTROL

BADARAU GHEORGHE, DIMA ADRIAN, SIMIONESCU AURELIAN, NĂNESCU VALERIU

This paper presents some aspects concerning a new, unconventional technology of control of heat pipes heat exchangers. Some details are being given about the temperature profiles of these thermal devices. Details are being given about the obtaining and about the use of temperature profiles in the technology of control of heat exchangers.

TECHNOLOGY FOR DISTILLER'S DISKS REALISATION

POPOVICI RADU, SIMIONESCU GHEORGHE

The distiller's disks work in pair, by twos, for wood fibres destruction in the goal process in optimal conditions the paste used in quality paper getting. The rapid wear of the kind of pieces is owed as well to components friction in the fibres destruction proce; corrosive medium, as well as dynamic shocks in case when in wood fibres absence, they a in direct contact. In this paper we present a new technology to distiller's disks realizatic which after the experimental results we obtain extremely good results.

INTERNATIONAL STEEL DATA A MODERN AND EFFICIENT TOOL

DOBRESCU RADU-NICOLAE, DOBRESCU SORIN