STRUCTURE AND MECHANICAL PROPERTIES OF Cu/Al6082T6 JOINTS PRODUCED BY WELDING WITH SCANNING ELECTRON BEAM

  • TITLE: STRUCTURE AND MECHANICAL PROPERTIES OF Cu/Al6082T6 JOINTS PRODUCED BY WELDING WITH SCANNING ELECTRON BEAM
  • AUTHOR(S): D. Kaisheva, V. Dunchev, G. Kotlarski, B. Stoyanov, M. Ormanova, V. Todorov, M. Atanasova, S. Valkov
  • ABSTRACT: This study presents the results of the electron-beam welding of pure copper (Cu) and aluminum (Al6082T6) alloy. The effect of the beam power on the phase composition, structure, and microhardness of the welded joints was studied. The power of the electron beam was set to 2400 W, 2700 W, and 3000 W, respectively. The phase composition of the fabricated joints was investigated by X-ray diffraction (XRD). The microstructure and chemical composition were performed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The mechanical properties of the welded samples were examined by microhardness investigation. The results obtained for the microhardness are discussed concerning the applied technological conditions, defined by the power of the electron beam. Furthermore, the possible applications of the obtained welded joints of copper and aluminum Al6082T6 alloy are discussed in the different fields in modern industry.
  • DOI: https://doi.org/10.62853/ELEV1494
  • PAGES: 46-49
  • DOWNLOAD: STRUCTURE AND MECHANICAL PROPERTIES OF Cu/Al6082T6 JOINTS PRODUCED BY WELDING WITH SCANNING ELECTRON BEAM
  • HOW TO CITE THIS ARTICLE: Kaisheva D., Dunchev V., Kotlarski G., Stoyanov B., Ormanova M., Todorov V., Atanasova M., Valkov S. Structure and mechanical properties of Cu/Al6082T6 joints produced by welding with scanning electron beam. Journal of the Technical University of Gabrovo 66 (2023) 46-49

NANOHARDNESS AND MODULE OF ELASTICITY OF CR-BASED NITRIDE COATINGS DEPOSITED AT TEMPERATURES BELOW 200°C

  • TITLE: NANOHARDNESS AND MODULE OF ELASTICITY OF CR-BASED NITRIDE COATINGS DEPOSITED AT TEMPERATURES BELOW 200°C
  • AUTHOR(S): V. Chitanov, E. Zlatareva, L. Kolaklieva, R. Kakanakov, T. Cholakova, S. Kolchev, C. Pashinski
  • ABSTRACT: Sets of Cr-based hard coatings were prepared via reactive closed field unbalanced magnetron sputtering (CFUBMS). Substrate temperature was kept in range of 150 to 200ºC during deposition. Nanohardness (H) and effective modulus of elasticity (E*) of the CrN, CrAlN, CrTiN and CrTiAlN coatings were examined using depth-sensing indentation method. The results from the combined examination of the research ratios showed that the triple and quaternary hard coatings have superior mechanical properties and they strongly depend on the deposition conditions.
  • DOI: https://doi.org/10.62853/HXOV5505
  • PAGES: 43-45
  • DOWNLOAD: NANOHARDNESS AND MODULE OF ELASTICITY OF CR-BASED NITRIDE COATINGS DEPOSITED AT TEMPERATURES BELOW 200°C
  • HOW TO CITE THIS ARTICLE: Chitanov V., Zlatareva E., Kolaklieva L., Kakanakov R., Cholakova T., Kolchev S., Pashinski C. Nanohardness and module of elasticity of Cr-based nitride coatings deposited at temperatures below 200ºC. Journal of the Technical University of Gabrovo 66 (2023) 43-45

INVESTIGATION OF CATIONIC SURFACTANTS ADSORPTION BEHAVIOUR ON SILICON WAFERS USING IMAGING ELLIPSOMETRY

  • TITLE: INVESTIGATION OF CATIONIC SURFACTANTS ADSORPTION BEHAVIOUR ON SILICON WAFERS USING IMAGING ELLIPSOMETRY
  • AUTHOR(S): M. Georgiev, B. Konstantinov, K. Marinova, J. Petkov, K. Danov
  • ABSTRACT: The research paper explores the adsorption properties of cationic surfactants on silicon wafers through imaging ellipsometry. The objective of this research is to shed light on the layer structures formed by cationic surfactants, specifically those based on dimethyl ammonium chloride, on silicon wafers. The study involved the deposition of three distinct cationic surfactants on the wafer's surface, followed by the measurement of the adsorption layers formed. The findings reveal the creation of thin, smooth, and irregular adsorption layers. Interestingly, no correlation was found between the thickness of the adsorption layer and the surfactant tail's chain length. The research underlines the significant role which the imaging ellipsometry can have for studying surfactants' adsorption properties on surfaces, contributing to their optimal usage in various fields.
  • DOI: https://doi.org/10.62853/WVFB5121
  • PAGES: 38-42
  • DOWNLOAD: INVESTIGATION OF CATIONIC SURFACTANTS ADSORPTION BEHAVIOUR ON SILICON WAFERS USING IMAGING ELLIPSOMETRY
  • HOW TO CITE THIS ARTICLE: Georgiev M., Konstantinov B., Marinova K., Petkov J., Danov K. Investigation of cationic surfactants adsorption behavior on silicon wafers using imaging ellipsometry. Journal of the Technical University of Gabrovo 66 (2023) 38-42

STUDY OF THE RHEOLOGICAL CHARACTERISTICS OF VEGETABLE OILS

  • TITLE: STUDY OF THE RHEOLOGICAL CHARACTERISTICS OF VEGETABLE OILS
  • AUTHOR(S): H. Hristov, P. Bonev, G. Iliev
  • ABSTRACT: One of the most important properties of liquids is their viscosity. It characterizes the magnitude of the internal friction when the individual layers of the liquid change relative to each other. A study was conducted to determine the effect of higher shear rates on the absolute viscosity of vegetable oil at various temperatures from 3 to 100°C. The absolute viscosity of the vegetable oil was determined using the HAAKE MARS iQ Air, a rotating viscometer with a coaxial cylinder. Based on the rheograms, it is observed that the vegetable oil is most viscous at 100°C and least viscous at 3°C. The absolute viscosity of vegetable oil is reported to decrease with increasing temperature.
  • DOI: https://doi.org/10.62853/BVXL3090
  • PAGES: 34-37
  • DOWNLOAD: STUDY OF THE RHEOLOGICAL CHARACTERISTICS OF VEGETABLE OILS
  • HOW TO CITE THIS ARTICLE: Hristov H., Bonev P., Iliev G. Study of the rheological characteristics of vegetable oils. Journal of the Technical University of Gabrovo 66 (2023) 34-37

MACHINING OF TOOTH PROFILES ON CNC MACHINES

  • TITLE: MACHINING OF TOOTH PROFILES ON CNC MACHINES
  • AUTHOR(S): H. Yakimov, I. Aleksandrova, Y. Mitev
  • ABSTRACT: Conventional methods of tooth machining using worm modular milling cutters, gear wheels and gear combs have common disadvantages - they require specialized equipment, are characterized by complex readjustment and relatively low productivity, which are eliminated in skiving. This paper views the possibilities for machining tooth profiles by means of skiving on CNC turning and milling machines. A new version of the kinematics of the process upon cutting inclined teeth has been implemented, where the feed is in the direction of the tooth, no correction in the angular speed is required and a skiving tool profiled according to the profile of the machined surface is used. Meshing of a tooth pair with crossed axes is reproduced. As a result of the crossing, slipping of the profiles occurs, which is the main cutting motion. The cutting speed, as a determining mode factor, can vary widely and depends on a number of design and technological parameters. Single-factor experiments have been conducted to determine the influence of the conditions of the implementation of the skiving process (the crossing angle of the tool axes and the workpiece, determining the magnitude of the cutting speed, and feed rate) on the quality parameters of the machined surfaces (tooth profile deviation, tooth direction deviation, accumulated pitch error, largest pitch difference and radial runout error) and the corresponding graphical dependencies have been constructed. A 7-12 degree of accuracy of the machined tooth profiles has been ensured.
  • DOI: https://doi.org/10.62853/KMYU1846
  • PAGES: 29-33
  • DOWNLOAD: MACHINING OF TOOTH PROFILES ON CNC MACHINES
  • HOW TO CITE THIS ARTICLE: Yakimov H., Aleksandrova I., Mitev Y. Machining of tooth profiles on CNC machines. Journal of the Technical University of Gabrovo 66 (2023) 29-33