Table of Contents

  • TECHNOLOGIES

    • OPTIMISING TECHNOLOGY FOR PRODUCTION OF HIGH FREQUENCY WELDED PIPES MADE OF X60 STEEL

      pg(s) 12-15

      In this research work the Welding technology that implements high frequency contact welding process (HFCW), is presented as a method for automatic steel pipes production. The pipes produced by the HFCW are meant to be used for natural gas transportation.
      X60M steel coils with thickness of 6.5 mm are used as a raw material. The outer pipe diameter is φ508 and the length is 12000 mm. The preliminary welding procedure is based on the personal experience, technical knowledge and the expert judgment. A special attention has been paid to the most important welding parameters such as: current frequency, voltage and welding speed. After the welding was finished, an additional heat treatment (normalization) of the welded pipes (joints) was performed at the temperature of 900oC.

      In order to justify the proposed welding technology a complex analysis is applied. The first analysis was the chemical analysis of base metal. The next was the nondestructive testing consisted of a visual inspection, and ultrasound testing of the pipes. The destructive testing was consisted of tensile testing, bend testing and the hardness measurement. Besides the analysis of the micro and macro structure of the welded joints, a metallographic analysis is performed as well. Moreover a hydrostatic test and a flattening test were performed as an integral part of the entire testing process. The test results confirmed that the pipes produced with the predicted welding parameters completely fulfilled standard requirements. The manufacturing process for the pipes for natural gas transportation is ready to begin.

    • ONTOLOGY-BASED DATA ACCESS AND MODEL TRANSFORMATIONS FOR ENTERPRISE INTEROPERABILITY

      pg(s) 16-19

      Enterprise interoperability is the ability of disparate and diverse information and control systems to work together efficiently towards mutually beneficial common goals. Some of the main tasks for achieving enterprise interoperability are connected with data and knowledge access and sharing and by use of model transformation. In this paper are presented and discussed several model transformations between different Technological Spaces: RDB, UML and OWL in order to enable ontology-based access to different models of enterprise data. At the core of the approach is the usage of reference models, based on the standard for enterprise integration ISO/IEC 62264.

    • A MAPREDUCE SOLUTION FOR HANDLING LARGE DATA EFFICIENTLY

      pg(s) 20-23

      Big data is large volume, heterogeneous, distributed data. Big data applications where data collection has grown continuously, it is expensive to manage, capture or extract and process data using existing software tools. With increasing size of data in data warehouse it is expensive to perform data analysis. In recent years, numbers of computation and data intensive scientific data analyses are established. To perform the large scale data mining analyses so as to meet the scalability and performance requirements of big data, several efficient parallel and concurrent algorithms got applied. For data processing, Big data processing framework relay on cluster computers and parallel execution framework provided by MapReduce. MapReduce is a parallel programming model and an associated implementation for processing and generating large data sets. In this paper, we are going to work around MapReduce, use a MapReduce solution for handling large data efficiently, its advantages, disadvantages and how it can be used in integration with other technology.

    • ADVANCED CREATING OF 3D DENTAL MODELS IN BLENDER SOFTWARE

      pg(s) 24-25

      The development of virtual 3D dental models evolves with great pace. This is a stage of construction, which is of great importance in future developments of real manipulation, prosthetics and other activities set for execution. Concept of modeling of 3D dental models is determined on the basis of concrete requirements, factors and opportunities. A good basis for creating virtual dental models provide Blender software combined with specialized applications which improve the process of modeling.

  • MACHINES

  • TECHNOLOGIES

    • LOCAL POST WELD HEAT TREATMENT OF WELDED STEEL PIPES

      pg(s) 30-33

      In this paper, local post weld heat treatment (LPWHT) effects on the metallurgical and mechanical properties of high frequency electric resistance welded (HFERW) steel pipes were investigated. Local post weld heat treatment (LPWHT) of the welded joint was carried out by an induction heating device which selectively heat only the weld area from the outside surface of the welded steel pipes. Optical microscopy, tensile testing, Charpy-V-notch testing, hardness testing and flattening testing were used to evaluate local post weld heat treatment (LPWHT) effects on the metallurgical and mechanical properties of high frequency electric resistance welded (HFERW) steel pipes.

    • FRACTOGRAPHIC ANALYSIS OF WELDED JOINT SURFACES

      pg(s) 34-37

      In this paper are presented some macrofractographic and microfractographic analysis of welded joint fracture surfaces, respectively welded seam (W), heat affected zone (HAZ) and base metal (BM), of spiral and longitudinal steel welded pipes after conducting the laboratory destructive testing. Destructive testing are conducted to assess the quality of the steel welded pipes and besides the numerical results, the fracture surface of the tested samples offers additional information, very important for assessing the quality of steel welded pipes. Given this, in the paper are treated the macrofractographic and microfractographic analysis (LOM-Light Optical Microscopy and Scanning Microscopy-SEM) of the fracture surfaces of samples which are fractured after destructive testing. The morphology of the fracture surfaces is compared with the numerical results and it concludes that there is a direct correlation between the obtained results and deformation that causes fracture, providing thus additional information for assessing the quality of the welded pipes.

  • MATERIALS

    • COMPARATIVE ANALYSIS OF STATIC AND DYNAMIC ELASTIC MODULUS OF POLYMER CONCRETE COMPOSITES

      pg(s) 38-41

      The article presents a comparative analysis of the quantitative values obtained from the experimental tests, of the static and dynamic modules of elasticity (Young’s modulus) of gamma polymer-concrete composites. The same will be used as constructive material for parts and body elements. Standard test methods are applied. The values of the elastic parameters of the tested polymer-concrete composites are necessary as input data for the various engineering analysis softwares.

    • A COMPARISON OF FRICTION CHARACTERISTICS OF VARIOUS SURFACE TREATED HOT WORK TOOL STEEL

      pg(s) 45-47

      Wear, is one of the most important failure type which reduces the service lifetime and increases the maintenance cost of machines. In addition, wear is directly related with surface properties and friction characteristics. So, researchers focus on various surface treatments to reduce the wear and its cost. Plasma nitriding is one of surface treatment which forms a few hundred micron diffusion zone and a surface inter-metallic phases with moderate surface hardness. PVD coating is another method which ensures ultra-hard and a few micron surface layers. In the present study, AISI H13 hot work tool steel substrate was surface treated with various methods, such as plasma nitriding, PVD coating and duplex treatment. Effects of the treatments on the surface roughness, hardness were investigated. Additionally, microstructural analysis was performed to present the effect of treatments on the surface microstructures. Furthermore, friction characteristics were investigated using ball on disk testing machine and wear tracks were discussed using optical microscopy.

    • NEW IRON OXIDES/HYDROXIDES BIOMATERIALS FOR APPLICATION IN ELECTRONICS AND MEDICINE

      pg(s) 48-51

      Biotechnologies could supply inexpensive, environment friendly and effective materials for new nonstandard and concurrent solutions. The present work’s focus was on acquiring new physical data for application in electronics and medicine of biogenic materials obtained due to the metabolism in laboratory conditions of iron-oxidizing bacteria from the genus Leptothrix. Powders and coatings on glass samples were under investigation. XRD and Raman Spectroscopy analysis of the data collected show that the Fe2+-depending from the growth media could transformed into Fe3+ or Fe2.5+ in the form of two types of oxides/hydroxides such as magnetite (Fe3O4) and lepidocrocite (ɣ-FeOOH), all with nanostructured morphology. Biotechnology for obtaining one biogenic iron phosphate hydroxide (ferrian giniite) – (Fe5(PO4)4(OH)3.2H2O) was also developed. The ferrian magnetic material is dispersed in the walls of biogenic tubular structures.
      The average particle’s size and crystalline structures of bio-products were investigated. Results based on PPMS measurements on the magnetic properties were reported. The new biogenic materials showed superparamagnetic behaviour and high sensitivity to electromagnetic radiation and have real potential for application in electronic and information technologies.

    • EFFECT OF METAL PHASE COMPOSITION ON MECHANICAL AND TRIBOLOGICAL PROPERTIES OF Fe-GLASS COMPOSITES

      pg(s) 52-57

      The effect of metal phase composition in the Fe-based + (2 % glass) powdered composites on the basic mechanical and tribological properties of the composites, made by means of sintering and hot forging, have been investigated. As a basis for the metallic phase of the composite the mixtures of iron powders with additives of graphite, B4C, BN and Cu at different ratio were used. It was shown that at sintering of metal-glass material the reaction of glass phase with oxides on the surface of iron powder particles takes place, resulting in a change of glass phase chemical composition. The results of materials mechanical properties investigations had shown that the highest strength properties and hardness have the composites with the content of the initial powder mixture of 5% Cu and 2% B4C, while the best tribological properties have the composites with 2% B4C, 5% Cu and 1% BN.

    • COMPARATIVE STUDY OF TRIBOCORROSION PROPERTIES OF SOME BIOBASED MATERIALS IN SIMULATED ARTIFICIAL SALIVA

      pg(s) 58-60

      In this study, the tribocorrosion behavior of the materials utilized in manufacturing of biomedical implants (Ti-6Al-4V and Co-Cr alloys) was studied in a laboratory simulated artificial saliva (SAS) solution by using a linear reciprocating ball-on-plate tribometer with an integrated electrochemical cell. The open circuit potential (OCP) and the friction coefficient were monitored during the reciprocating ball- on-plate test. During the OCP tribocorrosion tests, the generated wear debris was transferred into the SAS and increased its optical density of the solution along with large scatters in the OCP potential and friction coefficient. In accordance with its poor tribocorrosion performance, Ti-6Al-4V alloy provided a large amount of wear debris transfer into the SAS along with the heavy metal attachment to the contact surface of the alumina ball and heavy fluctuations in the OCP potential and friction coefficient values during the sliding. This suggests that the Co-Cr alloy has a higher load bearing capacity than the Ti-6Al-4V alloy.

    • TRIBO-CORROSION BEHAVIOR OF CAST AND SELECTIVE LASER MELTED Co-Cr ALLOY FOR DENTAL APPLICATIONS

      pg(s) 61-64

      Cobalt-chromium based alloys are widely used in dental applications due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. Although they are generally fabricated by casting for dental restorations, recently selective laser melting (SLM) has become an attractive production method since it allows complex geometries. Recent studies revealed that Co-Cr alloys formed by SLM, provided better corrosion resistance as well.

      In this study, tribo-corrosion behavior of a Co-Cr-Mo alloy produced by casting (Biosil-Degudent) was compared with the one (Co212-f ASTM F75) produced by SLM. The wear properties were investigated by tribo-corrosion tests in a Fusayama-Meyer artificial saliva solution using a “ball-on-disc” type tribometer. Polished surfaces were tested against zirconia balls at the same sliding speed, distance and load. Friction coefficient values were determined and the worn surfaces were evaluated using microscopes to compare the wear and tribo- corrosion resistance through wear tracks. SLM proved to be a promising manufacturing method for dental applications.

    • OBTAINING OF GAS-TIGHT GLASS-CERAMIC JOINTS OF MULLITE ARTICLES THROUGH THE NANOCRYSTALLIZATION OF Y2O3-Al2O3-SiO2 GLASS

      pg(s) 65-67

      Obtaining gas-tight joints between mullite articles was made by crystallization of yttrium alumosilicate glass. The glass joint layer softens at joining temperature (1450-1470oC) to bond the mullite samples without additional pressure and then crystallized during cooling. The good adhesion of crystallized glass to mullite surfaces ensue the gas-tight joints with permittivity 2.5*10-4 sccm/cm. The eutectic like crystallization of initial yttrium aluminosilicate glass into yttrium silicate and mullite lead to formation the nanocomposite structure which ensure the 4 point bending strength value near 105 MPa.

  • MACHINES

    • THEORY OF PRECISION MECHANIC PANEL SCREWS

      pg(s) 8-11

      Constructions belonging to precision mechanics need to be suitable for the functional conditions. The product has to perform the task reliably in its perfection in the prescribed limit of error. At the same time this aim must be reached not at any price but economically, well manufactured and in easily marketable realization. A new construction usually becomes out of date in three-four years morally deteriorates even though if it is useful in the aspect of working. This is the explanation of the fact that the standardization and the normalization in precision mechanics play a great role. During the latest decades the polymer pieces have been appearing in the different areas of the industry. Nowadays polymer and composite materials are used not only as covering but as the material of concrete mechanical elements as they have a wide workable and usability spectrum. The pieces made of polymer materials in the telecommunication industry take an honoured place. It is because they are good insulators they are light and cheaper than the metal materials. In the European Union it is a regulation that the most of the pieces must be recyclable. It means not only the reuse of the raw material but the recycle of the pieces. So the new and economical types of connection in the polymer pieces have appeared, and their examination have become important, too. The self- tapping screwed joint is suitable, too, the economical point of view and for the recycle, as it does not need any more operations after the removal of the screw.