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Recent 43

Vol. 15 (2014), No. 3 (43), November 2014

 

This issue of the RECENT® journal was edited and multiplied with support of:


CONTENTS



  • Daniel BĂNCILĂ, Constantin BUZATU

Minimizing Makespan in a Flow Shop Scheduling Problem

» Abstract

Abstract. This paper studies the problem of flow shop scheduling in order to minimize the maximum time of completion of all jobs. Taking into consideration all the aspects involved in scheduling this specific case of problem is one of the most important because of its applicability on the engineering field, many solutions being proposed for its solving. By combining priority rules with genetic algorithms, this paper offers a hybrid solution for solving this problem.

» Keywords

flow shop scheduling, genetic, algorithm, optimization, priority

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  • Sorin Adrian BARABAȘ, Adriana FLORESCU

Influence of Geometry of Hollow Rollers on the Contact Stress to the Large Bearings

» Abstract

The research answers to problems appeared in exploitation of large bearings, namely, uneven wear on the rollers and the raceways, as a result of high centrifugal forces. Currently, this problem is solved by execution of a geometric logarithmic profile of rollers which prevents the effects of dangerous contact stresses witch occur at the ends of their, profile which requires precision operation with high costs. This paper proposes the use of innovative design of hollow rollers whose profile remains cylindrical and optimization of cavity by finite element analysis performed with Nastran software. The research prove that hollow rollers with different cavities, tested in simulation, reduce inertial masses and have behaviour as good in deformations and much better in contact stress. The geometry of hollow rollers achieved by optimizing the hollow ratio of rollers influences the distribution of contact stress to the ends of roller and provides to the large bearings an increased durability by reducing uneven wear.

» Keywords

hollow rollers, elastic contact, ends stress

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  • Horațiu BULEA

Dimensional Variation of Polyurethane Foam Panel on Circular Cutting with Abrasive Water Jet Technology

» Abstract

The abrasive water jet method can offer a suitable solution for manufacturing of polyurethane foam panel that are usually difficult to do. This paper presents the results of some experiments on abrasive water jet cutting of circular holes into polyurethane foam panel. The main problem which occurs is the tapered shape of the hole, due to the mechanics of the process and the control of the surface produced by the abrasive water jet. The experiments considered several values of the main process parameters like the feed rate and nozzle diameter which have a direct influence on the part cutting process. After measuring the parts, there were analyzed the main dimensional parameters of precision to reveal the proper solution for obtaining the required quality of the process.

» Keywords

circular cutting in abrasive water jet, dimensional variation of cut diameters

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  • Nicolae Tudor CÂNDEA, Virgil Nicolae CÂNDEA

Research on Metallic Lance Thermal Cutting of Building Materials

» Abstract

It was designed and executed a plant for thermal cutting of building materials (concrete), which uses besides oxygen and metal lance with beam wire, iron powder flow and bulk chemicals, which pass with oxygen inside the metal lance to increase productivity process of thermal metal lance cutting to a higher temperature in the cutting area, increasing the fluidity of slag (oxides) and depth of practice cut to be less limited by the ability of the operator.

» Keywords

materials, equipment, thermal cutting

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  • Catrina CHIVU

Pneumatic Driving in Material Handling Systems

» Abstract

Pneumatics is one of the most used systems in these days. Today equipment and system use this type of actuating because it is a very safe, economic and ease to implement. Another advantage that recommends this type of actuating is the reduced loss of heat during the actuating process. Material handling systems are characterised by repetitive movements, speed and displacement control and precision, requirements that recommend pneumatics driving. The present paper is focused on pneumatics used in material handling system, underling the limitation or the specific application of concrete actuators.

» Keywords

material handling, Matlab, pneumatics, simulation

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  • Cătălin-Iulian CHIVU

Simulation of Double Acting Pneumatic Cylinder Control

» Abstract

Implementing optimal control in a pneumatic driven system is not a very cheap or easy process. The control subsystem of a pneumatic driven system has to distinctive direction: the control from pneumatic point of view and the control from automatic point of view. The present papers offer a cheaper solution to choose an optimal control and command system from both perspectives. The solution offered is to simulate such a system using Matlab-Simulink toolbox.

» Keywords

command, control, pneumatics, cylinder, Matlab-Simscape

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  • Adrian DĂNILĂ, Ioana Mădălina PETRE

A Nonlinear, Inertial-Type Approximation of the Pneumatic Artificial Muscle Model. Experimental Determination of the Equivalent Frequency Transfer Function

» Abstract

At present the pneumatic artificial muscle is largely used in powerful robot-arms and machine-to-human interfaces. This paper focuses on the modelling of the pneumatic artificial muscle. The first theoretical part of the paper, presents the main models of the pneumatic artificial muscle discussed in literature. The second theoretical part of the paper addresses the equivalence between the non-inertial hysteresis model of the muscle and an inertial equivalent elliptical hysteresis model. In the experimental part of the paper, the experimental setup and the computational methods are presented. The numerical results and the conclusions are presented in the final part of the paper.

» Keywords

hysteresis, modelling, nonlinear systems, pneumatic artificial muscle

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  • Georgi DINEV, Petar ANGELOV

Computer Aided Design and Production Analysis of Vane Pump

» Abstract

This article represents an approach for CAD/CAM-based development of technological, constructional documentation of a rotational pump regarding its assembling. An approach for computer-based designing and assembling of the pump has been invented on the basis of pre-created 3D geometrical models of the compound details and the assembled unit as well as on a basis of a virtual, technological analysis of the pump. A constructor can demonstrate his/her skills and knowledge in the process of development of the compound details by using the already generated, summary drawing of the pump. In order to provide full exchangeability of the main, compound details, an analysis has been made as it concerns manufacturability of the dimensioning and assembling of the details on the basis of computer-made simulations. All of the results that have been obtained are required for the purpose of Computer Aided Manufacturing that is to be performed by the technologists. They are also useful for the purpose of training of students and specialists that have to acquire knowledge and skills through the work with contemporary CAD/CAM software products.

» Keywords

CAD, geometrical models, vane pump, documentation, technologic manufacturing, analysis, assembling

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  • Valentin DIȚU

The Wear and the Radial/Axial Beat at the Conic Countersink Reamers and Countersink Reamers with Guide Pilot

» Abstract

This paper presents a method that helps to establish correctly the axial and radial beat for conic countersink reamers and for countersink reamers with guide pilot using as criteria the wear of the edges on the back edge. This paper is important because the establishment of the axial and radial beat recommended in the specialty literature, in normative or Romanian standards, does not depend on the wear of the cutting edges, fact that leads to a significant shortening of the cutting tool’s life.

» Keywords

conic countersink reamers, countersink reamers with guide pilot, cutting, wear

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  • Adriana FLORESCU, Sorin Adrian BARABAȘ

Techniques Regarding the Performance Evaluation of Logistic Systems

» Abstract

Logistics through its activities is vital in creating such an advantage, it can positively influence market share and profitability of the enterprise and it is viewed as a strategic resource, not just a simple activity. This paper aims at presenting the logistics and supply chain contribution to competitiveness and customer satisfaction, operational principles of industrial management and logistics of modern techniques and strategies flow management and functional integration within enterprises and between enterprises. It is important to identify which performance measurement tools are correlated most with the success of a performance measurement system. The aim is to develop a model for evaluating and analysing the logistics performance in the supply chain to manufacturing and service firms of the business field. It follows thus, performance evaluation of logistics systems through the introduction of "key indicators" of performance, efficiency, with minimal costs.

» Keywords

production systems, supply chain management

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  • Valerii KYRYLOVYCH, Petro MELNYCHUK, Lubomir DIMITROV, Roman MORGUNOV, Aleksandr PIDTYCHENKO

Automated Research of Trajectory Problems in Industrial Robotics by the Criterion of Power Consumption

» Abstract

The modeling of the movements of industrial robots' grippers between two random points of its (industrial robots) working area with generation of appropriate trajectories is presented. The values of power consumption for each trajectory are determined. Examples of trajectories based on the criterion of minimum power consumption for each generated trajectories are presented. For modeling was used developed by authors special program.

» Keywords

industrial robot, trajectory, modeling, power, automation

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  • Zoltan MARKOS

Study of the Mechanism of Diffusion in Siliconized Brass

» Abstract

The siliconizing thermochemical treatment has been done in a powdery medium with paste, in sealed boxes. After the micro-structural investigations with scanning electronic microscope (SEM) and EDAX analysis, it has established the Si, Zn and Cu atoms diffusion mechanism in the siliconized superficial zone. At different temperatures of treatment are obtained diffusion zones with different hardness. The siliconized brass presents high mechanical characteristics and corrosion resistance.

» Keywords

brass siliconizing, diffusion mechanism, microstructure of diffusion layer

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  • Simona MATEI, Aurel CRIȘAN

Thermal Resistant Composite Materials in Use Today - A Review

» Abstract

This paper presents a brief bibliographic summary of the thermal resistant composite materials. The attention focuses on the structure and properties of the thermal resistant composite materials. In the composite materials structure are described characteristics of ceramic matrix and reinforcing elements. As reinforcing elements were studied the continuous fibers (fibers of silicon carbide, alumina, fiber glass and quartz) the discontinuous fibers and the particles. As the thermal resistant composite materials properties were studied mechanical properties: mechanical strength, fatigue strength, abrasion strength, modules of elasticity, thermal properties: thermal conductivity and thermal contraction, chemical properties: oxidation resistance.

» Keywords

thermal resistant composites, ceramic matrix, fiber, mechanical properties

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  • Ioan MILOŞAN

Study to Determine the Gaseous Emissions from the Combustion Gases

» Abstract

The paper presents some aspects about measurement of the pollutants emissions from a heat treatment plant. Responsibility belongs emissions monitoring equipment operators, environmental authorities and organizations involved (authorized organizations- companies, laboratories, operators are empowered to make measurements of emissions of air pollutants from large combustion plants). In this paper, the practical examinations were made in collaboration between author and the Monitoring Department from the Environmental Protection Agency of Brasov, conducted in a company’s "Metrom Industrial Park", the source of pollution was a tempering furnace fuelled by natural gas for heat treatment. Sampling points were: before and after the filter basket mounted on the exhaust gas inside the oven. It was used a gas analyzers TESTO 350 XL - a performance equipment to determine gaseous emissions from the combustion gases. All the determinations were done in special cells, following chemical reaction type Peltier. Analyzed gases are: SO2, CO, CmHn, O2, NO and NO2. Following the experimental determinations, it can be concluded that they exceeding the emission limit values for the indicator of carbon monoxide (CO), both before and after the filter, gives a hot-performing incomplete combustion.

» Keywords

monitoring, gaseous emission, combustion gases, heat treatment process

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  • Cristian PISARCIUC

A Review of Unconventional Procedures for Manufacturing Tool Electrodes Used in EDM

» Abstract

Electrical discharge machining (EDM) is an unconventional process for machining electrically conductive materials that are difficult to process by other known means. EDM requires that the tool, at least in the die sinking technology, to be the negative of the cavity to be processed. Therefore, processing of tool electrodes is a necessary step but also is the cause for substantial costs associated with machining and the time needed to complete it. Technologies based on the principle of additive manufacturing could be a viable alternative to produce these electrodes. This paper intends to provide a review of possibilities of additive manufacturing - AM to be used as a process to produce tool electrodes to be used in die-sinking EDM.

» Keywords

EDM, EDM electrodes, additive manufacturing

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  • Luciana Cristiana STAN

Efficient Management in Enterprises by Sustainable Development of Competences

» Abstract

The topic addresses the need to implement the concept of sustainable development businesses in Romania, Austria, and Germany. The article examines the adaptation and customization of software created by the author assessment of general skills, entrepreneurial, professional and employee cross on green technology related to modern firms that have adopted the promotion of sustainable development. The software allows customization of questionnaires by employees, by type of firm, and its size. To this end, it identifies, promotes and develops according to the needs of employers, relevant new occupations sustainable growth in Europe, reinforcing creativity and innovation, increase quality, equity and efficiency of training systems and the ability of employees to use knowledge and technology in the occupation carried out in order sustainable development. Efficient management of such enterprises is ensured by identifying employment opportunities in promoting sustainable development.

» Keywords

management, enterprises, sustainable development, competences

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  • Maria STOICĂNESCU

Studies Concerning the Possibility of Hardening through Thermic Isothermal Treatment of the Casting Alloys of Aluminium

» Abstract

The studies undertaken have the objective of proving the property of a hardening aluminum alloys through warm oil-quenching. Maintaining in the stair of the temperature intermediary between one of heating and one environment he had the same influence with the one the ageing realized after accustomed hardening. In this kind there are coupled two distinct operations of thermal treatment in only one.

» Keywords

heat treatment, aluminium alloys

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  • Ana-Maria Adina ȘUTEU (BĂNCILĂ), Constantin BUZATU

Participatory Design Methods in the Development of Products and Environments for Elderly Users with Physical Impairments

» Abstract

It has been observed that the incidence of impairment increases significantly with age, resulting in a large social group that stands the need for specially designed systems intended to improve their quality of life. Increasing age is often associated with a rise in other diseases such as osteoarthritis, reduced hearing and vision, memory loss, physical impairments and general frailty that lead to mobility problems. Thus results one of the major challenges that is keeping the older adults independently mobile, most commonly solved by the employment of assistive technologies. On the other hand, research has identified a multitude of factors that hinder the acceptance of assistive technology, people often holding a negative view towards such technologies and being reluctant to adopt them. Consequently, it raises the need to consider user-inclusive requirements which address psychological and socio-emotional needs of users. Taking into consideration these factors, the paper presents the application of participatory design methods in the development of products and environments intended to improve the activity and overall live quality of the elderly. Furthermore, a case study is conducted in order to establish the best solution for the design of a new mobility aid that would increase mobility and ease of movement and, at the same time, is socially accepted by the group of older adults.

» Keywords

participatory design, elderly users, user-centred design

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