• Influence of the rate of cooling on the formation of non-equilibrium eutectics in preeutectic alloys of the AL-SI system

    pg(s) 331-333

    Computer experiments were carried out with a simulation model of alloy crystallization in this work. The model was preliminarily calibrated for alloys of the Al-Si system. The presence of a non-equilibrium eutectic in pre-eutectic alloys with a silicon content of 1.0% – 1.6% has been detected. The minimum cooling rates at which the formation of an eutectic in these alloys is possible have been determined.

  • Morphological study of rubber granules used in artificial turf systems with SEM and DSC methods

    pg(s) 328-330

    Rubber is different from other polymeric materials because it needs to be crosslinked or vulcanised and mixed with several additives like fillers to achieve its state. The recycled rubber materials presented as granules are rapidly used as infill material for different fields. One of the most important issues, especially in Albania is proving that these materials are recycled. One of the most important issues, especially in Albania is proving that these materials are recycled. Through the images provided by SEM we could study the microstructure of our samples. Also, after conducting an EDX spectrum analysis, we observed additives in the recyclable materials. The DSC methods analyses that will provide info regarding the composition in rubber granules. Thermal analysis is an essential technique to measure the temperature or time dependent response of physical and chemical changes that occur in materials.

  • Operational characteristics of nanocomposite lubricants

    pg(s) 325-327

    The study of the structure and physicomechanical characteristics of carbon nanostructures, lubricants and cooling liquids was carried out by methods of scanning electron microscopy, atomic force microscopy, IR spectroscopy, physicomechanical and physicochemical analysis. Tribotechnical tests were carried out on a friction machine operating according to the “sphere – plane” scheme.The possibility of modifying various liquid media with nanosized carbon particles of various composition, structure, production technology, including those obtained by the method of self-propagating high-temperature synthesis, has been studied. The studies carried out made it possible to establish general trends in the implementation of the synergistic effect in liquid matrices differing in structure, polarity of macromolecules, and molecular weight.

  • Impact of chemical composition on tribological properties of AlxCoCrFeNi high-entropy alloys

    pg(s) 323-324

    High-entropy alloys were first extensively described in 2004 [1]. Despite the increasing scientific interest in these materials, there is still much to discover. The AlCoCrFeNi alloy is one of the most popular HEAs. Scientists often study the mechanical properties of this alloy and the effect of varying the different component contents on its properties [2,3]. There are also studies on the effects of alloying additives on structure and properties [4,5]. In this study, high-entropy alloys were obtained by induction melting. The influence of aluminium content and titanium addition on tribological properties of AlxCoCrFeNi alloy was tested. Furthermore, the alloys were characterised by X-ray diffraction (XRD), hardness, and microstructure examination. The occurring wear mechanisms and tribological properties of the tested high-entropy alloys were analysed and compared with the results obtained for C45 steel. The received results confirm the influence of Al content in AlxCoCrFeNi alloy and Ti addition on tribological properties

  • Decreasing pressure losses by applying drilling mud with nanoparticles

    pg(s) 319-322

    During mud circulation pressure losses occur in all sections of the wellbore: surface pipeline, inside drill string, drill bit and around drill string. The sum of the pressure losses calculated for each section is equal to the total pressure loss in the system, i.e. the pressure that is read on the manometer of the mud pump. The mud flow through annulus (between drill pipes/collars and open hole/casing) causes an increased pressure loss for the certain flow rate which increases the pressure exerted on the wellbore wall, so it is important to manage it. In this paper, the influence of SiO2 nanoparticles on the rheological properties of bentonite mud was examined. After tha t, for a typical wellbore construction and selected mud flow was calculated their influence on pressure losses in the area around drilling pipes and collars. The pressure losses were determined using the Bingham model which provides an easy way to obtain data of acceptable accuracy for the case of application in conventional vertical wells. The results indicate that the addition of SiO2 nanoparticles can reduce the pressure loss during mud circulation, in some cases by more than 50%.

  • Investigation of the coalescence of twin coplanar semi-elliptical fatigue cracks in structural steel elements under cyclic loading

    pg(s) 316-318

    The solution to the scientific task of identifying the fundamental laws of surface cracks development during their coalescence in the elements of steel structures under cyclic loading is presented in this article. A simulation model of coalescence of identical coplanar surface cracks has been developed. The model considers the solution to two problems: substantiation of the crack geometry during coalescence, and obtaining calculation formulas for estimating the stress intensity factors along a series of saddle-shaped contours. Based on the definition of stress intensity factors for contours modeling the gradual propagation of cracks in the coalescence zone using the finite elements method, the proposed model was tested to compare the calculated durability with experimental data.

  • The methodology of functional modifiers choice for nanocomposites based on industrial thermoplastics

    pg(s) 311-315

    The methodological principles for the implementation of the concept of multilevel modification of polymer matrices by components with given energy parameters to obtain nanocomposites with a synergistic com-bination of performance characteristics have been developed.
    These principles based on:
    – established crystal-chemical prerequisites for the natural and synthetic carbon-, metal- and silicon-containing semi-finished products choice for the directed formation of active nanosized particles with given structural, morphological and energy parameters under optimal technological impact (mechanical and chemical, thermal, laser);
    – implementation of the conditions for the energetic compliance of nanomodifiers to the prevailing mechanism for the formation of the optimal structure of polymer, oligomer and blend matrices at various levels of organization – molecular, supramolecular and interphase;
    – creating the conditions for the reveal of the prevailing mechanisms of interphase physical and chemical interactions of components with the formation of boundary layers of the optimal structure, which deter-mine the mechanisms of destruction of products from nanocomposites under various operational factors impact;
    – achieving the conditions for the synergistic effect of structuring by using a complex of modifiers with a certain combination of parameters of dimensional, geometric and energy characteristics.

  • Utrafine-grained structure and thermal stability of the two-phase titanium alloy VT8M-1

    pg(s) 309-310

    In this work, the method of backscattered electron diffraction (EBSD) and transmission electron microscopy (TEM) was used for microstructural analysis of the improved VT8M-1 alloy (Ti-5.7 Al-3.8 Mo-1.2 Zr-1.3 Sn) subjected to equal-channel angular pressing (ECAP) and rotary forging (RF). It was found that the process of globularization induced during deformation processing is regulated by the conventional boundary-splitting mechanism. It was shown that an orientation relation is established between the spheroidized a – and bphases. This result is achieved due to the high activity of dislocation sliding at the boundary of the a-and b-phases. The thermal stability of the VT8M-1 alloy with an ultrafine-grained (UFG) structure is s -term (up to 500 hours) annealing the UFG structure is thermally stable. The mechanical properties and the effect of annealing on the microstructure are discussed. It is shown that particles of the Ti-Zr-Si system are isolated at the interphase boundaries.

  • Recent applications of nanoparticles in wood-based panels

    pg(s) 287-290

    Nanocellulose applications in the wood-based panels have gained a great deal in the scientific researches and industrial applications. Utilization of natural and synthetic nanoparticles as reinforcement in the wood-based panels has considerably increased in the last two decades due to their unique properties. The main property of the nanocellulose is its very high surface area. Hereby, the very small use of nanoparticles suh as %1-2 wt% in the composites is enough at a relatively low-cost. Nanoparticles are presently considered to be high-potential reinforcing fillers for the enhancement of the physical, mechanical, electrical/electronic properties, thermal resistivity, fire, durability properties of wood-based panels such as particleboard, fibreboard, oriendted strandboard, and plywood. The nanoparticles are applied to wood based panels dur ing the manufacture and after production. The raw materials such as wood or resin can be treated with nanoparticles or the finished panels can be treated with nanoparticles. In this study, the recent developments in the nano particles, their applications in the wood based panels, and their effects on the panel properties were reviewed

  • Investigation of the causes of corrosion of galvanized steel pipes used for hot water supply

    pg(s) 283-286

    The object of the study is the part of the galvanized steel pipe (about 1-meter-long) supplied by the customers, which was used to supply hot water inside the residential building and which has corroded during exploitation of 5 years. To clarify the situation, quality of surface coating and microstructure of the obtained galvanized steel pipe was analysed. Electrical stray currents of the pipeline installed in the building were measured. The sample of the hot water was taken and analysed at the certificated laboratory.
    The aim of the investigation was to determine the possible causes of the hot water supply pipe corrosion during sufficiently short time of exploitation.

  • State and prospects of application of plastically deformed nanostructured metals, alloys, and sprayed coatings

    pg(s) 279-282

    It is shown that thermal stabilization of the polygonization substructure up to 60 min is provided by a combination of uniaxial compressive deformations, namely dynamic by 30% and static by 30%, followed by pre-recrystallization heat treatment (PHT) at the initial recrystallization temperature. This ensures subgrain size of 80… 187 nm, while strength characteristics increase by 10… 30% with sufficient ductility.
    It is shown that PHT provides the formation of nanoscale elements in electric arc coatings with Sv-08G2S (Св-08Г2С), and additional deformation of the coating allows to increase the thermal stability of the polygonization substructure up to 40… 50 min. It is found that the combined deformation and subsequent PHT of steels provides an increase in the calculated number of nanoscale subgrains from 15 to 65%.

  • The nanostate factor in the technology of polymer nanocomposites

    pg(s) 275-278

    Methodological approaches to the implementation of the nanostate phenomenon in the formation of the optimal structure of composite materials and metal-polymer systems at different levels of organization have been developed. The concept of energy and technological compliance of functional composite materials and systems components, which determines the optimal parameters of stressstrain, adhesion and tribological properties under technological influences on the components in the process of obtaining composite and its processing, is proposed.