Machines. Technologies. Materials.
Vol. 10 (2016), Issue 9

Table of Contents

  • MACHINES

    • EFFECT OF FRICTION ON A RECEDING CONTACT BETWEEN A PERFECT-FIT PIN, BUSHING AND PLATE

      pg(s) 3-6

      This paper presents the results of a finite element analysis of a receding frictional contact between a perfect-fit pin inside a bushing, which is in perfect fit with a hole in a plate. The elasticity of all three bodies is taken into account, and the bodies are considered as isotropic.

      The problem is analysed within the frame of linear theory of elasticity and under the assumption of plane strain conditions. The fact that the presence of friction affects contact pressure distributions is well known, and the results obtained for the structural problem presented here are a novelty in this field of study. In addition, the results are analysed for several different geometries, which gives an insight into the influence of the ratio between the pin radius and bushing thickness.

    • DETERMINATION OF INPUT/OUTPUT CHARACTERISTICS OF FULL-BRIDGE AC/DC/DC CONVERTER FOR ARC WELDING

      pg(s) 7-10

      This paper describes the design and practical implementation of AC/DC/DC converter in mode of arc welding. An analysis of the operation of AC/DC/DC converter and its input/output characteristics are determined with computer simulations. The practical part is con- sisted of AC/DC/DC converter prototype for arc welding with output power of 3 kW and switching frequency of 64 kHz. The operation of AC/DC/DC converter is validated with experimental measurements.

    • DESIGN OF A NEW FRANCIS TURBINE RUNNER FOR A REHABILITATION PROJECT IN TURKEY

      pg(s) 11-14

      This study presents the rehabilitation project for the Francis turbine runner of Kepez 1 Hydroelectric Power Plant (HEPP) in Antalya, Turkey. The aim of rehabilitation is to increase the power and efficiency of the plant and solve the existing problems such as cavitation. Initially, the head and flow rate of the turbine are estimated. Within the scope of this study, the design parameters which are necessary to obtain better cavitation characteristics and higher power and efficiency, are determined and computational fluid dynamics (CFD) is utilized to design a new runner geometry for better performance. The results of the CFD simulations are compared to the simulation results of the existing runner geometry which was obtained from the plant and scanned using laser scanning. The results show that cavitation characteristics and the efficiency, as well as the power of the HEPP are improved.

  • TECHNOLOGIES

    • EFFECTS OF MECHANICAL ALLOYING TIME AND ANNEALING TEMPERATURE ON THE PHYSICAL PROPERTIES OF Al – WC COMPOSITE POWDERS

      pg(s) 15-17

      In this study, mechanical alloying (MA) of Al-WC powder system was studied to produce aluminium composite powders having finer tungsten carbide fraction in aluminium matrix. For this purpose, elemental mixtures of 70 wt. % aluminium (Al) powder and 30 wt. % of tungsten carbide (WC) powder were mechanical alloyed for the duration of 2, 4 and 8 hrs. MA’ed powders then annealed at 300 ºC, 400ºC and 500ºC for 2 hours under inert atmosphere. Apparent densities of powders were measured in order to characterize both mechanical alloyed and annealed powders. Compressibility of the powders was determined by green density measurements after pressing.

      Microstructural characterizations were conducted with X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Strain rates and crystallite sizes were measured according to fundamentals parameter approach (FPA) by applying Lorentzian function using software TOPAS 4.2.

    • VIBRATION POWER GENERATION WITH PIEZOELECTRIC ELEMENT USING COUPLING WITH CYLINDRICAL SOUND FIELD ENCLOSED BY END PLATES HAVING DIFFERENT THICKNESS

      pg(s) 18-2

      This paper describes the electricity generation characteristics of a new energy-harvesting system with piezoelectric elements.
      The proposed system is composed of a rigid cylinder and thin plates at both ends. The piezoelectric elements are installed at the centers of both plates, and one side of each plate is subjected to a harmonic point force. In this system, vibration energy is converted into electrical energy via electro-mechanical coupling between the plate vibration and piezoelectric effect. In addition, the plate vibration excited by the point force induces a self-sustained vibration at the other plate via mechanical-acoustic coupling between the plate vibration and an internal sound field into the cylindrical enclosure. Therefore, the electricity generation characteristics should be considered as an electro- mechanical-acoustic coupling problem. Actually, the plate on the excitation side is lower than that on the non-excitation side in the natural frequency because of the influence of a vibrator to apply the point force to the plate, so that both natural frequencies are not identical and the effect of mechanical-acoustic coupling is not clarified very well. Then both frequencies are close by tuning the natural frequency due to thinning the plate on the non-excitation side. As a result, it is expected that the electricity generation characteristics are improved by promoting mechanical-acoustic coupling in comparison with the inherent situation.

    • PRECONDITIONS OF SEPARATION IN STR WITH INTEGRATED MEMBRANE FOR ENERGY-SAVING BY RECOVERY OF VALUE-ADDED MATERIALS

      pg(s) 22-25

      Energy-saving by recovery of value-added materials from complex dispersions by using semi-permeable membranes has been proved world-wide. The effect is related to fundamental knowledge of fluid flow and mass transfer in complex fluids close to membrane interfaces. Innovative biotechnologies for value-added products such as exopolysaccharides or antioxidants benefit by such explorations in preserving the biological activity of the target components. The paper presents a solution of theoretical model of a stirred tank reactor (STR) Biostat equipped with membrane immersed in a non-Newtonian model solution of exopolysaccharide, e.g. glucomannan and biomass. CFD methodology is employed to reveal original data on shear deformation rates and shear stress at the membrane interface, as well as to predict the average mass transfer coefficient related to the boundary layer at the membrane surface based on the flow information obtained. The results are compared with similar data reported for conventional systems with different impeller and systems with external membranes.

    • THE METHOD OF SPIRAL DESIGN MODEL FOR THE AUTOMATED DESIGN OF ANALOG IP-CORES IN COMPUTING

      pg(s) 26-29

      The systematic approach of complex technical devices design allows not only to design new devices and objects, but also to automate the design process. This article discusses the seven-layer spiral design model, which can be used to simplify the design process of complex devices in areas of mechanical engineering and computer engineering. The spiral model in this work is used for automation of analog IP-cores design; in particular, the windows application that implements the automated design system of analog low-pass filters was developed. The application allows user to design the filter scheme in automated mode after inputting the parameters. The proposed method has certain benefits compared to the known automated design methods for the specific object classes.

    • THE NUMERICAL-ANALYTIC SUBSTANTIATION OF THE POSSIBILITY OF AUTOMATED MOTION CONTROL OF AN AUTONOMOUS RIGID BODY WITHOUT ITS OWN PROPULSION SYSTEM IN INCOMPRESSIBLE STRATIFIED VISCOUS FLUID

      pg(s) 30-32

      The report presents a mathematical model of the motion control of an autonomous solid body moving in incompressible stratified viscous fluid and analytical and numerical analysis of this model. It is assumed that the body does not have its own propulsion system, but is equipped with controlled rudders – wings of finite span. It is moved by the influence of the buoyancy force and wings lift. The control is produced by the angle of attack of the wing change for ensuring access to the given point by this solid body. This body motion is considered to be plane-parallel motion. This paper results are based on the mathematical model which was presented by the authors at XII MTM Congress held in September 2015 and XIII MTM Congress held in March 2016.

  • MATERIALS