Machines. Technologies. Materials.
Vol. 16 (2022), Issue 5

Table of Contents

  • MACHINES

    • Evolution of spindle assemblies of machines based on motor-spindle

      pg(s) 150-154

      Solving the problems caused by the growth of M-S diversity belongs to the latest current scientific field of research in modern mechanics and electromechanics, which is generalized to the concept of structural and systems research with models of microevolution and macroevolution. If genetic synthesis allows to find new structures of M-S and spindle nodes on their basis, then for the synthesis of schemes and structures it is advisable to use a system-morphological approach. To develop a morphological model, functional (morphological) features are selected, which are divided into three groups in accordance with the modular principle: the modules of the rotational motion of the spindle, the drive feed -translational motion and the clamp-expansion

    • Energy analysis of a steam turbine with two cylinders and steam re-heating

      pg(s) 155-158

      This paper presents an energy analysis of middle-power steam turbine with two cylinders (High Pressure Cylinder – HPC and Low Pressure Cylinder – LPC) and steam re-heater after the HPC (and before the LPC). Based on a steam operating parameters from the literature, performed energy analysis show that LPC develops higher power and has higher energy efficiency (81.45%) in comparison to HPC (which energy efficiency equals 80.12%). Re-heater is a heat exchanger (flue gases are used for steam heating) which has low energy loss (824.19 kW) and high energy efficiency (97.76%), what is expected energy performance of such heat exchanger. The entire analyzed turbine develops a power of 127480.60 kW and has energy loss equal to 29848.21 kW with energy efficiency of 81.03%.

  • TECHNOLOGIES

    • Quality assessment of heterogeneous welding joints made by GMAW method

      pg(s) 159-164

      At present, various types of steel grades are used in the production of welded structures and assemblies, resp. combinations of ferrous and non-ferrous metals. In these mutual combinations, it is necessary to know the specifics of weldability of both materials, to choose a suitable welding technology and a suitable filler material. In the experimental part, the quality of heterogeneous welded joints was verified by the GMAW method. A protective gas atmosphere of 82% Ar + 18% CO2 was used for welding (M21 – ISO 14175: 2008). The possibilities of welding and mutual combinations of austenitic stainless steel with structural non-alloy steel, structural alloyed high-strength steel with structural non-alloy steel were assessed. The quality of welds was evaluated using non-destructive and destructive tests in terms of standards: visual test STN EN ISO 17637, capillary penetration test STN EN ISO 22476-12, internal errors were evaluated using radiation tests STN EN ISO 17636-1. The destructive tests used the tensile test STN EN ISO 6892-1, the weld fracture test STN EN ISO 5173 and the Vickers hardness test STN EN ISO 6507-1, the bending impact test STN EN ISO 9016 and the metallographic analysis according to STN EN ISO 17639.

    • Effect of the forging process in a tool implementing alternating deformation on the structure and mechanical properties of AISI-5140H low-alloy structural steel

      pg(s) 165-166

      The article describes the concept of a new forging method of circular cross-section blanks in a forging tool, the design of which makes it possible to develop significant alternating deformations in the deformable metal. The results of comparative studies of the microstructure and mechanical properties of AISI-5140H low-alloy structural steel, formed in a new forging tool that implements alternating deformation and in flat strikers are presented.

    • Optimization of technological parameters of blasting process on metal surface roughness

      pg(s) 167-169

      The main goal of this contribution is study the microgeometry of blasted surfaces. The aim is to design suitable microgeometric characteristics for the description of pretreated surfaces, experimentally verify the influence of blasting agents of various shapes and sizes on the microgeometry of metal surfaces. The following types of evaluation are used to meet this goal: 2D roughness determinat ion and profilograms, 3D surface visualization and surface volume determination. The results of the experimental part will contribute to the optimization of technological parameters of the tearing process.

    • Improving the accuracy of electron-beam processing of small thickness optical plates

      pg(s) 170-175

      The article presents the results of increasing the accuracy of the operating parameters of the electron flow (power density, speed of electron-beam processing) in obtaining optical plates of small thickness as components of optical instrumentation devices. It is shown that flexible control of such parameters of tape electron flow allows to significantly (1.5-2 times) increase the accuracy and quality of surface processing of small thickness (up to millimeters) optical silicate plates (glass K8) by low-energy electron flow. The implementation of such management was carried out using an information-measuring system, the general principles and functional scheme of which are given in this article. The proposed system allows with high accuracy (relative error does not exceed 4.5%) and efficiency (the time between the moment of
      determining the parameters of the electron flow to the moment of its formation with the adjusted values of these parameters does not exceed 12-17 μs).

    • Optimization of joining parameters of thin-walled materials by flowdrill technology

      pg(s) 176-178

      This paper deals with the investigation of the effect of speed on the form fit joint of dissimilar materials. Thin -walled materials based on steel and aluminium alloy were joined by thermal drilling. The shape and size of the resulting bushing were evaluated. It turned out that the best material combination for joining by flowdrill technology are joints made of steel and aluminum alloy. Aluminum alloy must always be placed in the bottom position. The best parameters of the formed bushing were achieved with the combination of DC-Al or TL-Al materials, at tool speeds of at least 2400 rpm.

  • MATERIALS

    • Properties of polymer composites with long fibers

      pg(s) 179-182

      The paper is focused on composite materials with a polymer thermosetting matrix reinforced with long (continuous) fibers. These materials offer their specific properties that can be used in various areas of industry. From this point of view, polymer mat rix composites are, due to their mechanical properties and low weight, the most promising material for use in various application solutions. However, their disadvantage is the high price, which is higher than the price of conventionally used materials. The method of production of components from composite materials itself requires precisely specified technological procedures, which differs slightly from the traditionally used methods of component production, e.g. of metal materials.

    • Pattern steel: production technology and fracture surface evaluation

      pg(s) 183-185

      Presented article deals with the description of the technology of pattern steel production – forging welding, evaluation of fracture surfaces and mechanical tests of examined samples (resulting steel and its individual components). The damascus steel (pattern steel) was prepared by forge welding from a packet consist of a few hundred layers. Marbling was created by folding layers of 2 components: hard and tough steel of different thickness. For evaluation of mechanical properties was applied: Charpy impact test. The evaluation of the fracture surfaces of individual samples was performed by scanning electron microscopy (SEM). The values of mechanical properties of pattern steel themselves are in the range of values of mechanical properties of individual components. The fracture surfaces of the materials have a characteristic relief (in relation to the mechanical properties of the individual components).

    • Foam ceramic blocks with low thermal conductivity suitable for the construction of roads and urban square pavements and non-load-bearing partition walls

      pg(s) 186-188

      Lightweight porous ceramic has a number of advantages over the tightly sintered one depending on the field of application. As a building material with low thermal conductivity and good sound insulation properties, foam ceramic is a suitable material for the production of thermal and sound insulation panels, partition walls, as well as for layers laid under asphalt to protect road and urban square pavements from freezing. As a filling, foamed ceramic materials are also added during the production of lightweight concrete used in construction and architecture and in the manufacture of decorative and non-structural insulation elements. In the present study we consider the characteristics of marl clay, found around the village of Lovets near the town of Shumen, with coal as a foaming additive, and the technological regulation for the manufacture of foam ceramic blocks.