Table of Contents

  • MACHINES

    • TRUCK MOUNTED CRANES DURING LOAD LIFTING – DYNAMIC ANALYSIS AND REGULATION USING MODELLING AND SIMULATIONS

      pg(s) 12-15

      Truck Mounted Cranes are used for load lifting and lowering, mainly in construction industry for materials handling. These cranes have complex structure with many parts and mechanisms with bars, linkages, actuators, cables, outriggers, etc. Using modeling and simulations with software we will analyze dynamics and oscillations in crane while lifting the maximal load, and methods of control of these oscillations in order to optimize the work process of truck crane. Dynamic parameters analyzed are: velocity, acceleration, angular velocity, forces and torques that act in main parts of crane, including load swinging. The study will be accomplished with design of block diagrams that represents crane model and motion, and gain results in form of diagrams containing main kinematic and dynamic parameters. Results of the tested system will be used to get conclusions about dynamic behavior of crane, and look for optimal motion control. Analysis will be done using modeling and simulations with software MapleSim, based on truck crane from standard manufacturer.

  • TECHNOLOGIES

    • SMART URBAN TRANSPORT FOR THE CITY OF THE FUTURE

      pg(s) 16-19

      For urban transport to be competitive and sustainable, it has to be smart. Cities worldwide use smart technologies to integrate transport systems, minimize costs and improve user experience. The concept of smart transport is a hot topic between city leaders looking to find a wave of innovation to more sustainable and prosperous cities [1]. The city of Skopje is on a good path towards the development of smart urban transport. Hence, the purpose of the paper is to present progress made in the city of Skopje implementing smart measures in urban transport. More important, the analysis recommends additional smart measures and directions with a potential to support and strengthen sustainable urban mobility features.

    • PROGRAMMING MODULE DESIGN FOR SETTING TECHNOLOGICAL PARAMETERS FOR WORKPIECES

      pg(s) 20-22

      This paper presents an option of formalizing input data in automated design processes for machining. A tabular data model required by the technology technician is designed to develop products for the machining process, namely a workpiece. A script-based approach of human-computer dialogue in the setup of structural and technology parameters of a workpiece is adopted as well as particular algorithms to be submitted into the system.

    • COLDDRAWINGOFPUREMAGNESIUMWIRE

      pg(s) 26-29

      Pure magnesium is a material with very high functionality, however, the cold drawing of this material is very difficult, because it has a hexagonal crystal structure and until this day there is no optimal cold wire drawing conditions. In this research, the goal is to create the optimal cold drawing conditions for pure magnesium wires. The first step is the investigation of the annealing temperatures by using tensile testing of the annealed wires, which will allow is to optimize the manufacturing of magnesium. Following the results listed below, the most suitable annealing temperature was 250°C for a reduction of 10% per pass. After the reaching the drawing limit and examining the drawn wires, cracks in the center of the wires, that is why suppressing their occurrence by applying a middle annealing to the process is needed. Consequently, it is possible to produce a cold fine drawn pure magnesium wire, without cracks or defects on the surface or hindering its medical properties.

  • MACHINES

    • EFFECT OF FRICTION ON A RECEDING CONTACT BETWEEN CYLINDRICAL INDENTER, LAYER AND SUBSTRATE

      pg(s) 3-6

      This paper presents the results of a finite element analysis of a receding frictional contact between a cylindrical indenter, layer and substrate. The elasticity of all three bodies is taken into account, and the bodies are considered as isotropic. The problem is analysed within the frame of linear theory of elasticity and under the assumption of plane strain conditions. It is a well known fact that the presence of friction modifies the resulting contact pressure distributions, and the results obtained for the case of elasticity of all three bodies presents a novelty in this field of study. Furthermore, the results are analysed for several different geometries, which gives an insight into the influence of the ratio between the indenter radius and layer thickness.

  • MATERIALS

    • CoO/Al2O3, CuO/Al2O3 AND NiO/Al2O3 CATALYSTS FOR PHOTODEGRADATION OF MALACHITE GREEN DYE UNDER UV-IRRADIATION

      pg(s) 30-33

      CoO, CuO or NiO supported on Al2O3 photocatalysts were prepared by impregnation and then calcination at 400oC for 3 hours. The obtained samples were physico-chemically studied by Powder X-ray diffraction analysis, X-ray photoelectron spectroscopy and Scanning electron microscopy. The photocatalytic oxidative degradation of aqueous solution of Malachite Green (MG) dye as pollutant using CoO, CuO or NiO supported on Al2O3 under UV irradiation was tested. The results determined that the highest degree of degradation of MG dye after 120 minutes was achieved using NiO/ Al2O3 photocatalyst (82%) than that the other materials CuO/Al2O3 (64%), CoO/Al2O3 (59%) and Al2O3 (50%). The calculated apparent rate constants increasing in the order: Al2O3 (2.7×10-3 min-1)<CoO/Al2O3 (3.9×10-3 min-1)<CuO/Al2O3 (4.1×10-3 min-1)<NiO/Al2O3 (8.4×10-3 min-1).

    • ELECTRIC DISCHARGE SYNTHESIS OF TITANIUM CARBIDE

      pg(s) 34-37

      Peculiarities of titanium carbide obtainment by high voltage electric discharge synthesis (HVED) are considered in present paper. Mathematical and physical modelling of processes that occur during HVED impact on “Ti powder – hydrocarbon liquid” disperse system is performed. HVED creates thermodynamic conditions for pyrolysis of hydrocarbon liquid with formation of solid-phase carbon and gaseous hydrogen and for synthesis of titanium carbide during reaction of carbidization between titanium and carbon particles. Regularities of connection between HVED parameters and changes of dispersity and intensity of titanium carbide formation.

    • POLYMER COMPOSITES WITH FIBER REINFORCEMENT

      pg(s) 38-40

      Polymers are used in every walk of life now-a-days. They are not even hundred years old but playing significant role in every sector of life such as sports, defense, medical, automobile, electrical, agricultural etc. In the beginning, polymers were considered as excellent insulators but conductive polymers are available now. Polymers have good water resistance but some polymers are good absorber of water. The present article deals with monitoring the changes in the mechanical properties of composites with polymer matrix. The composite was formed from the PA matrix and glass fibers. The mechanical properties, impact strength (Charpy) and micro-hardness (Vickers) were evaluated on samples of the composite before and after UV radiation on the sample.

    • POLYESTER/SILICATE COMPOSITES

      pg(s) 41-44

      This work is a continuation of the HUPER development, as in this study hydrophilization was performed by different types of cement (grey cement and medical cement). It was established that alkaline hydroxides in the cement “milk” composition traditionally perform the preselected role of a hydrophilizer. Water was used as a second dispersing component, which can not only homogenize the composition of the prepared composite material. A third component was introduced (water glass), which was studied due to its dispersing role towards the resin/cement/water system. Mechanical strength characteristics (mostly impact characteristics) characterizing the shape, dimensions and integrity of the operational product were studied based on the obtained composition in various proportions of components.

    • EFFECT OF PLASTIC DEFORMATION ON THE MICROSTRUCTURE AND PLASTICITY OF HIGH FREQUENCY ELECTRIC RESISTANCE WELDING

      pg(s) 45-48

      High frequency electric resistance welding is one of the most extensively used methods for production of longitudinally welded carbon steel pipes suitable for line pipe, casing and tubing. In this pipe production process, the hot rolled steel strip goes into the continuous cold forming process and its edges are continuously joined by a combination of localized high-frequency electric resistance heating and plastic deformation. The heated edges up to the welding temperature squeezed together at the “Vee” apex by the forge pressure rolls, plastically deformed and a forge type weld is formed. The plastic deformation which is realized under the action of the squeezing rolls caused changes of the microstructure constituents in the bond line and in the heat affected zone and plays principal role on the quality of the welded joint. In this paper microstructure and plasticity of the welded joint were investigated by light microscopy and flattening testing.

      The obtained results shows that plastic deformation plays principal role on the microstructure and plasticity of the welded joint.

  • MACHINES

    • THE STRAIN OF CLAMPS ON CARRYING STRUCTURE

      pg(s) 7-8

      As a result of the conducted theoretical and experimental researches of the local state of strains at the most loaded intersection of the clamps on the working wheel’s carrying structure in a concrete rotating excavator, an array of results has been attained. This paper represents systematically by means of diagrams the results of such researches under normal and specific working regimes of the excavator.

      The specific working regimes during the entire exploitation life of the excavator account for about 1 %, with the excavator working in specific cases while digging under unpredictable working conditions. The experimental magnitudes of the strains are obtained with conducted experimental measurement in compliance with the established methodology for this purpose. The theoretical magnitudes of the strains are derived using the established mathematical model of clamps and applied computer FEM analysis.

    • NEW TYPE OF INNOVATIVE LIFTERS

      pg(s) 9-11

      In this article the new shape of lifters for Semi-Autogenous Grinding (SAG) and autogenous mills has been investigated. Lifters are designed for lifting, separating the grinding bodies (at SAG mill) and the grinding material to the required height of separation, crushing and grinding of the material in order to achieve the required output particle size. The main purpose of these mills is material grinding and crushing. Lifters are most used in the mining industry. Hence, attention is paid to analysis of different working regimes of mills with new lifter shape.