Machines. Technologies. Materials.
Vol. 14 (2020), Issue 4

Table of Contents

  • MACHINES

    • Innovative design solutions of universal motor gearbox with helical gears

      pg(s) 137-141

      Due to very force competition, all producer, not only manufacturers of gearboxes, have been forced to constantly improve their products. This has led to the harmonization of the technical characteristics of their gear units, even though they are not yet defined by the standard. Modern solutions of universal helical gearboxes are characterized, first of all, by large torque capacity and high values of gear ratio in the frame of relatively small overall dimensions of the gear unit. This paper provides an overview of common activities undertaken by manufacturers of universal helical gearbox to improve technical characteristics of their products.

    • On the kinematics and tooth flank geometry of Spr –gearing

      pg(s) 142-153

      This paper deals with gearing of a novel design. Insensitivity to the gear axes misalignment is the principle feature of gearing of the proposed design. The discussion begins with a brief historical overview on design of geometrically-accurate gearing. Then, fundamentals of gearing that is insensitive to the axes displacements are discussed. Elements of kinematics, an actual configuration of the gear axes of rotation, and so forth are covered in this discussion. Analytical expressions for tooth flanks of a gear and a mating pinion for gearing of the proposed design are derived. Features of interaction of tooth flanks of a gear and a mating pinion are briefly discussed. The paper ends with the analysis of potential applications of “ Spr pr gearing”, and conclusion.

  • TECHNOLOGIES

    • 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.

    • 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

    • 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.

    • 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.

    • 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.

  • MATERIALS

    • Corrosion of high purity magnesia refractories from iron-rich slags of ferronickel enrichment in OBM converters

      pg(s) 177-180

      The corrosion of high purity MgO refractories from molten iron-rich OBM converter slag has been investigated by performing experiments in an electric laboratory furnace. Corrosion tests were conducted at 1600 – 1650oC for 1, 2 or 4 hours. Following lab experiments, the mineralogical phases of MgO refractories, slags and the intermediate infiltration zone were identified by SEM/EDS. It has been shown that Fe infiltrates and replaces Mg in MgO refractories, thus forming magnesiowustite ((Mg,Fe)O). The maximum depth of the slag infiltration zone was estimated to 1.31 mm in the laboratory test where slag was in contact with the refractory for 4 h, at 1650⁰ C Thermodynamic modeling of the slag and refractories equilibrium conducted with FactSage 7.0, confirmed the formation of magnesiowustite in the intermediate zone, with progressively higher substitution rate of Mg by Fe. This increasing substitution results in a decrease of the melting point of magnesiowustite, thus causing the collapse of the refractories even at temperatures lower than the operational temperature.

    • Characterization of Sri Lankan brick clays for more advanced industrial uses

      pg(s) 181-185

      Brick clay is a well known type of clay which is available at various locations in world and the name was realized because of the constantly usages in the industry of brick manufacturing that based on the condign characteristic with the necessitate features for the bricks. The investigations of the fundamental and advanced physic-chemical characteristics of a type of Sri Lankan brick clay and bespeaking of the more advanced industrial uses of such clays are the ultimate realities of the existing study. The collected clay samples from a particular location were fundamentally characterized by testing the natural moisture content, grain size distribution, acidity of raw clay samples and the water absorption, bulk density, porosity and mechanical strengths of prepared bricks under 8000C using such clay In addition that those clay samples were characterized using X-ray fluorescence (XRF) spectrophotometer, Fourier transform infrared (FT-IR) spectrophotometer and X-ray diffraction (XRD) spectrophotometer. As the retributions of those analyses, mainly observed 6.57 of PH, uniformly graded grain size distribution, 37.36% clay and silt portion according to the weight and 21.45% natural moisture content from raw clay samples and 19.88% water absorption, 3.15 gcm-3of bulk density, 62.70% of porosity, 17.25MPa compressive strength, 0.31MPa splitting tensile strength from prepared bricks. The compositional analysis results showed 84% of Fe content with trace amounts of Ti, Ba and Ca, presence of calcite, quartz and more Fe minerals while lacking of any hazardous elements or compounds such as the heavy metals. By considering the characters of brick clay, it is possible to recommend this clay for the applications of water treatments, ceramic manufacturing, refractory material and sorption (adsorber) material for removal of metals.