• Comparison of corrosion resistance of traditional and modern alternative pipeline steel

    pg(s) 172-176

    The paper presents results of research aimed at comparing selected properties of two types of pipe steels, conventional 17G1S-U steel and alternative S960QL steel. The steels were compared in terms of their chemical composition, microstructure, hardness and corrosion resistance. Static electrochemical corrosion tests were performed on the materials, namely electrochemical impedance spectroscopy (PEIS) and linear polarization (LP) in two electrolytes. The results show different chemical composition and microstructure of materials. 17G1S-U steel has a row-like ferritic-pearlitic structure with a hardness of 200 HV 0.1. S960QL steel has a martensitic structure with a hardness of 353 HV 0.1. Steels showed very close corrosion rate in both electrolytes.

  • Technique of tooth relieving of worm hobs for cutting Novikov gears with double lines of action

    pg(s) 166-172

    Worm hobs for cutting Novikov gears have the profile of a generating worm, which varies not only in a radius, but also in a sign of curvature. A technique for relieving tooth flanks of these hobs by disk grinding wheel is developed. It allows for bringing together grinding and ground profiles in an axial section of the generating worm as close as possible. A method for calculating setting-ups and profile coordinates of the grinding wheel is given for real production conditions.

  • Fatigue calculation of “SH” drainpipes

    pg(s) 163-165

    During the combustion processes of fuels, fuel gasses are created which flow over the heat exchanger. The flow of fuel gasses brings ash particles which are deposited on heat exchanger surfaces and thus reduce the heat exchange efficiency. The removal of ash deposits from the heat exchanger is performed by a striker. Striker indirectly strikes the floor of the lower chamber of the heat exchanger via the mandrel and transmits kinetic energy to it. The impact results in inertial forces on the layer of deposits that are greater than those of adhesion forces between the surface of the exchanger pipes and the ash deposits. The pipes are loaded with displacement caused by the impact of a mandrel used to clean the heat exchanger, displacement caused by the operating pressure inside the pipe, and thermal elongation. The load of the pipes is cyclic, and calculation was performed according to the standards: EN 12952-3:2012-03 and EN 13445-3:2009. The calculation was performed at critical pipe cross-sections. The Abaqus/CAE2016 software package was used to determine the critical cross-sections of pipes and stress that occur in them. The model was created using beam finite elements. After analyzing the stress and applying the standards, a conclusion is reached on the fatigue strength of the drainage pipes. The heat exchanger pipes are made of austenitic W.Nr.2.5956 and 16Mo3 steels. The pipe with maximum fatigue stress of 208 MPa is made of 16Mo3 steel, which has a tensile strength from 450 to 600 MPa. Young modulus of elasticity at an operating temperature of 383 ° C is E = 173,9 GPa. The permanent strength diagram is taken from EN 12952-3: 2011 standard shows that this material can withstand 107 cycles with such fatigue stress, and the required number of cycles is determined based on the customer’s request which is the projected number of years. The plant is projected on operating 5 years. The designed number of cycles is 350400 cycles, so it is concluded that the pipes satisfy the conditions of exploitation.

  • Adhesive bonding of dissimilar materials

    pg(s) 159-162

    The paper is focused on research results of dissimilar materials joining by adhesive bonding. Galvanized and non-galvanized steel sheets with a thickness of 0.8 mm were joined together. To compare the effect of the presence or absence of the Zn layer on the strength of the adhesive joints, control joints were made, consisting only of galvanized and only of non-galvanized materials. The materials were joined on one hand without any surface preparation, and on the other hand prepared by degreasing and mechanical roughening with sandpaper. Epoxy/PVC-Polymerblend adhesive with glass beads was used for bonding to check the thickness of the adhesive. The tensile lap-shear strength was tested according to DIN EN 1465. The joints made of galvanized materials only proved the highest, the joints made of nongalvanized materials only proved the lowest shear strength. The mixed joints did not reach the joint strength of galvanized materials, but exceeded the joint strength of non-galvanized materials. The adhesion of the adhesive to non-galvanized substrates seems to be the limiting factor of the strength of mixed joints

  • Determining the quality of renovation layers by using nano HVOF coatings

    pg(s) 154-158

    The paper presents the results of the research aimed at determining the quality of coatings applied by the HVOF spray coating technology and the advances in its application. WC-Co-Cr 86/10/4 nano covers were evaluated at two grain sizes. The effect of nano particle size on coatings quality was evaluated under abrasive wear conditions with bound abrasive in the initial state and after thermal cyclic loading. Coating thickness measurements, microhardness and structural analysis of the coatings were performed. As the number of thermal cycles increased, the hardness of the coatings increased. A thermal load between 600 and 800 ° C results in the crystallization of the amorphous phase, which leads to the precipitation of the WC phase from the Co-Cr matrix, and thus to an increase in the microhardness of the coating. The REM analysis of the structure of nano coatings confirmed that the exposure of the samples to the thermal load had an influence on their structural  composition. As the number of thermal cycles increased, the wear of the coatings under dry friction conditions increased.

  • Influence of complex ultrasound vibrations and composite lubricants on wear resistance of materials of endoprosthesis

    pg(s) 117-119

    As a rule, parts that are made of titanium alloys are critical parts that can work in corrosive medium, accept alternating loads, have certain parameters of surface quality and surface layer. A finite-element simulation of a burnishing process of titanium alloy Ti-6Al-4V (an alloy that is widely used in medicine, as an example in endoprostheses) with/without ultrasonic loading at various processing speeds was carried out. It is established that when burnishing with ultrasonic vibrations of the tool, it is possible to obtain a qualitatively different picture of the distribution of residual stresses in the surface layer of the part. The features of the contact interaction of the tool with the workpiece surface were established for ultrasonic vibrations of the tool. For finite element simulation two types of ultrasonic vibrations were chosen (according to real ultrasonic tool): longitudinal and longitudinal-torsion vibrations. It is shown that the use of ultrasound can reduce the temperature of the deformation zone, which is extremely important when processing titanium alloys. It was also found that the use of metal-containing lubricant can improve the surface quality  arameters after ultrasonic burnishing.

  • High pressure die casting mould renovation by cladding

    pg(s) 114-116

    The paper presents the results of the research of the evaluation of the overlay layers quality made by the fusible arc methods. By applying arc welding methods, it is possible to significantly extend the life of injection molds and thus significantly reduce production costs. The newly formed layers must meet a number of requirements so as not to degrade the advantages of high-pressure injection technology over conventional casting technologies. High pressure casting solves most of the problems of conventional casting technologies such as: porosity of the casting, high surface roughness, long casting time, inability to produce thin cross-sections and low dimensional accuracy. During exploitation, the mold surface is damaged, mostly by thermal cracking and combined adhesive-abrasive wear. Material used for high pressure die casting permanent mold is a medium alloyed hot tool steel Uddeholm Dievar. Layers were made using three types of filler materials on the Fronius TransTig 4000. To eliminate the effect of mixing, three layers were made. The quality of the deposits was assessed by non-destructive and destructive tests.

  • Influence of chemical surface pretreatment on adhesion properties and protective effect of coatings

    pg(s) 110-114

    The quality of the resulting surface treatment is influenced especially by the pre-treatment of the substrate, the design of the surface treatment such as the choice of the coating system, the method and the quality of application. From a variety of chemical surface pre-treatment methods, Bonderite chemical pre-treatment is at the forefront. This chemical pre-treatment is used at ambient temperature, phosphate-free. It forms a nano-ceramic protective layer on steel, zinc and aluminum surfaces. The use of Bonderite gives the coating a high quality, which shows good adhesion and excellent corrosion protection. Contribution is devoted to the evaluation of these properties

  • Investigation of the influence of basic technical parameters of ribbon electron flow on the microrelief of the optical glass surface

    pg(s) 106-109

    The article presents the results of a study of the influence of the main technical parameters of a ribbon electron flow on the microrelief of the surface of optical glass. A mathematical apparatus has been developed that allows the processing of probe characteristics obtained by sensing the energy parameters of a paraxial electron flow. The dependence of the influence of the main technical parameters (shape, size and distribution of current density) of a low-energy electronic stream of ribbon form on the microrelief of the surface of an optical glass of the crown variety has been established. This made it possible to evaluate the interaction of the electron flow with the surface of the optical glass. It was also found that the useful current of the electron flow is about 30% of the total emission current of the cathode of the electron gun. It is shown that the following factors can influence the accuracy of determining the technical parameters of a ribbon electron flow by sounding: a decrease in the diameter of the probes under the influence of the electron flow and heating of the probes during measurement. The total error of the probe method for determining the current density of the electron flow does not exceed 8%. Using atomic force microscopy, it was established that after processing the surfaces of optical glass of the crown variety with a low-energy electron-beam of a ribbon-shaped shape, provided that the rational shape, size and distribution of current density both in the working space and on the treated surface are reduced by irregularities from 40-75 nm to 3.5-5 nm. However, it was noted that the surface of the glass after electron flow treatment has a more uniform structure and is free from microdefects, in contrast to surfaces without electron flow processing

  • Estimation of structural similarity between plant-derived phenolic compounds and drug molecules by virtual screening of DrugBank

    pg(s) 83-86

    Phenols are widely distributed in various plants and plant-derived foods. Currently, there is an increasing interest in their application as food supplements. In this study we performed a virtual screening to identify potential molecular targets of phenolic compounds derived from medicinal plants known for their antioxidant and anticancer effects. A dataset of 75 phenols, reported in the literature and a virtual library of 7770 unique drug compounds, extracted from the DrugBank database (https://www.drugbank.ca/) were used. Multi-conformer structure databases were created using OpenEye OMEGA, shape- and chemical-based overlays of the conformers were performed in OpenEye ROCS (https://www.eyesopen.com/). As a result of the virtual screening, followed by data filtration and analysis, two bacterial enzymes, responsible for DNA replication, were suggested as potential novel targets of a plant-derived hydroxyanthraquinone. This research allows outlining the potential receptor-mediated pharmacological mechanisms of phenolic compounds and aims to be a first step in the development of in silico protocol for their prioritisation as healthy dietary supplements.

  • The importance of preventive thermographic inspections within periodic verifications of the quality of low-voltage electrical installations

    pg(s) 78-82

    During the lifelong maintenance of low-voltage electrical installations in any facility special attention must be given to firecausing failures, which cannot be detected by conventional protection devices (miniature circuit breakers, fuse-links, residual current devices, etc.). Such failures are most often caused by poor electrical contacts. International regulations and standards, which define periodic verification of the quality of low-voltage electrical installations, do not contain procedures by which a poor electrical contact would be detected at an early stage. However, one of the techniques used for this purpose today is performing preventive thermographic inspections (a standard covering this area is available only in the USA). By such inspections a poor electrical contact which creates prerequisites for the occurrence of an initial fire in a low-voltage electrical installation can easily and effectively be detected. Detected failures and irregularities can most frequently be eliminated by simple interventions of electricians or facility technical services. Experience from a large number of periodic verifications of the quality of low-voltage electrical installations in industrial and administrative facilities, conducted by personnel of the Laboratory for testing low-voltage electrical and lightning protection installations at the School of Electrical Engineering in Belgrade, showed that many dangerous failures would not be detected without performing preventive thermographic inspections. Several practical examples of such failures, detected in low-voltage electrical installations in industrial and administrative facilities during preventive thermographic inspections, are presented and analysed. The procedure of performing preventive thermographic inspections within periodic verifications of the quality of low-voltage electrical installations, as well as the explanation for proper interpretation of the measurement results based on the ΔТ and absolute temperature criteria, are also given in this paper.

  • Improving the wear resistance of the meat comminutor knives by using the method of pulse-plasma hardening

    pg(s) 75-77

    The paper presents experimental results of hardening of the meat comminutor knives by using the pulse-plasma method. A search for existing methods for increasing the wear resistance of knives of meat-cutting machines has been carried out. The determination of the increase in wear resistance of the meat comminutor knives has been carried out according to the following stages: knives hardening; knives testing on the meat comminutor with the simultaneous execution of control prints; determination of the radius of blade curvature using an optical microscope and processing of research results. It is experimentally established that the use of the proposed method allows to increase the wear resistance of the meat comminutor knives by 4 times. Also, during the study, the optimal hardening modes of the meat comminutor knives are determined. The graphical dependence of the amount of knives wear on the presence and regime of hardening treatment is presented.