Table of Contents

  • Substitution of gear-bar mechanism with bar mechanism on the infeed mechanism of bottle washer

    pg(s) 3-6

    In this paper we will consider substitution of special mechanism, part of bottle washer, which caries bottles to special „baskets“. These mechanism are mostly gear-bar mechanism and their construction is very expensive and overhauls last too long because of complexity of mechanisms..
    Mechanisms synthesis based on highly developed analytical / numerical procedures will be considered in this thesis. This means that we will develop procedure for constructing bar mechanism which will be able to fulfill our task to transfer bottles into „ baskets”, and to return into start position. The mechanism should also meet requirements in terms of main dimensions, which should be the same as for the old mechanism so the substitution can be performed. Special attention will be paid to analyze the singular positions of the mechanism when it loses mobility. These positions it is necessary to solve in a way so that mechanism continues to move and perform its function.

  • Optimisation of gear geometrical parameters using KISSsoft

    pg(s) 7-10

    In this study, optimisation of speed gears for a tractor transmission was performed with KISSsoft software. Optimisation was carried out under three constraints. These constraints are input power-torque, volume for system in transmission and gear ratio for each speed. The purpose of this study was to optimize the module, face width, gear quality, centre distance, number of teeth, helix angle, addendum modification coefficient and pressure angle for each speed considering the constraints. Tooth bending stress, tooth contact stress, contact ratio and specific sliding were considered for evaluation during optimisation. Strength calculation of gear pairs which were optimized and defined all geometrical parameters with KISSsoft were also calculated with mathematical model indicated in ISO 6336. Then, the results were compared.

  • Numerical analysis of turbo-generator steam turbine energy efficiency and energy power losses change during the variation in developed power

    pg(s) 11-14

    Developed power variation of turbo-generator (TG) steam turbine allows insight into the change of turbine energy efficiency and energy power losses. Measurements were performed in five different TG steam turbine operating points and analysis is presented in three randomly selected operating points. Turbine developed power was varied from 500 kW until the maximum power of 3850 kW in steps of 100 kW. Turbine energy efficiency increases from 500 kW to 2700 kW and maximum energy efficiency was obtained at 70.13 % of maximum turbine power (at 2700 kW) in each operating point. From 2700 kW until the maximum of 3850 kW, TG turbine energy efficiency decreases. Change in TG turbine energy efficiency is caused by an uneven intensity of increase in turbine power and steam mass flow. For all observed operating points, energy efficiency during turbine exploitation is approximately 10 % or more lower than the maximum obtained one. A continuous increase in turbine energy power losses during the developed turbine power increase are the most influenced by the continuous increase in steam mass flow through the turbine.

  • Surface hardening of metallic materials by use of combined mat-forming treatment and electrospark doping

    pg(s) 15-18

    Analysis of the structural state and phase composition of surface metal layers after combined treatment of steel which includes preliminary surface plastic deformation of the workpiece, electrospark doping with use of rotating disk electrode 2 mm thick, made of WCCo hard alloy and subsequent surface ball smooth rolling, has been performed. It was shown that the use of combined treatment provides a gradient-layered structure with low surface roughness. Phase composition of the obtained layer consist of ferritic α-Fe phase and a number of carbide phases formed during the interaction of the electrode material with steel: F3W3C, WC and W2C semi-carbide. Wear resistance of the material after treatment exceeds similar properties of the original carbon steel up to 4 times.

  • A-TIG welding as a solution for nickel and manganese savings in duplex stainless steel welded joints

    pg(s) 19-22

    The paper presents the influence of the activation flux and shielding gas on tungsten inert gas welding of the duplex stainless steel. In introduction part the productivity and the cost-effectiveness of A-TIG welding for duplex stainless steels was explained. In the experimental part X2CrNiMoN22-5-3 7 mm thick stainless steel has been welded in butt joint. The welding process was performed by a robot with TIG equipment. With selected A-TIG welding technology preparation of plates and consumption of filler material (containing Cr, Ni and Mn) have been avoided. Specimens from the produced welds have been subjected to tensile strength test, macrostructure analysis and corrosion resistance analysis. The results have confirmed that this type of stainless steel can be welded without edge preparation and addition of filler material containing critical raw materials as Cr, Ni and Mn when the following welding parameters are set: current 200 A, welding speed 9,1 cm/min, heat input 1,2 kJ/mm and specific activation flux is used.

  • Effects of process parameters in plasma arc cutting on stainless steels and structural steel

    pg(s) 23-25

    Plasma arc cutting is a non-conventional manufacturing process that has potential for modern day metal cutting demands with good dimensional accuracy and high-quality surfaces without any extra operation. In this experimental study, AISI 304, AISI 430 and EN S235JR sheet materials having 5 mm. thicknesses, has cut with plasma arc cutting. Each material has cut with 6 different variations. Current, cutting speed, arc voltage, gas pressure and gas flow rate have been changed as process parameters. The quality of the cut has been monitored by measuring the edge roughness, the hardness of the heat-affected zone (HAZ) and the results has compared.

  • An experimental study for thermal and hydraulic performance of a mini channel shell and tube heat exchanger using low concentration nanofluids prepared with Al2O3 nanomaterials

    pg(s) 29-35

    In this study, tube side thermal and hydraulic performance of a mini channel shell and tube heat exchanger (MC-STHE) designed using Kern method was investigated experimentally for water and α-Al2O3/water nanofluids prepared in two different low volume fractions (0.02% and 0.2%). The average particle diameter of Al2O3 nanomaterial used in the preparation of nanofluids is 50 nm. The copper tubes (L/D=120) with inner diameter of 2 mm and outer diameter of 3 mm and a length of 240 mm were used in the MC-STHE. During the experiments, shell side water flow rate was kept constant at 180 L/h, while the water and nanofluids flow rates on the tube side were changed between 60-600 L/h. The use of nanofluids in the MC-STHE deteriorates tube side convective heat transfer coefficient in the flow rates below 125 L/h, while enhancing convective heat transfer coefficient in the flow rates above 125 L/h, compared to water. The enhancement ratios for convective heat transfer coefficient compared to water were found to be 0.82-1.66 for 0.02% Al2O3/water and 0.9- 1.74 for 0.2% Al2O3/water in the range of 60-600 L/h volume flow rates. However, in the applications in which enhancement of the heat transfer is desired, it was obtained that the increase in pumping power should be taken into consideration depending on the selected nanofluids volume fraction. According to efficiency index in which increase in heat transfer and pressure drop compared to water are evaluated together, it was found that the use of nanofluids was significant in the flow rates above 375 L/h for 0.02% Al2O3/water and in the flow rates above 300 L/h for 0.2% Al2O3/water. The use of mini-channel increased the compactness by decreasing the weight and volume of the heat exchanger, and in addition to this, higher heat transfer coefficients were obtained by using nanofluids instead of water.

  • Calculating contouring tool by finite difference method

    pg(s) 36-40

    During the radial deformation of contouring tool, its active diameter is getting smaller than the initial one, and the cutting depth is becoming lower than planned. Thus, the diametrical size of the machined hole is always smaller than contouring tool, by value of the elastic radial deformation. In this regard, in the manufacture of contouring tool, it is necessary to make appropriate adjustments in the diametrical size of its cutting edge, depending on its elastic radial deformation.
    The paper dwells on the thermo-elastic problem of calculating contouring tool for the purpose of determining the actuating diametrical size of its cutting edge, and for determining the area of the application of tool material. Solving of non-dimensional non-stationary problem is carried out by method of finite differences. At each time step, the system of algebraic equations is solved by iterative method.
    There have been obtained the results for the temperature field and displacement components.

  • Testing of the synthetic model for transport demand and for forecast on vehicles, the case stady

    pg(s) 41-44

    Choosing a model, shaping and using a model represent a sensitive stage of the transport system planning process. Considering the fact that contemporary software packages exist, based on modern technology and long – term experience it is decided to rely on the software package PTV Vision VISUM, for forecast in the traffic in Bitola town. Synthetic model is designed by this software package, modeling is done on existing situation and model’s calibration. In this paper will be represented testing on the model for transport demand for the city of Bitola, their validation.

  • Tribological properties of commercially pure copper and a lowalloyed chromium bronze

    pg(s) 45-48

    In this paper, we present the results of the tribological studies of commercially pure copper (99.9% Cu) and a low-alloyed chromium bronze (Cu-0.5%Cr), contacting a graphite-containing material. The samples under study were produced with two types of microstructures: a coarse-grained (CG) one, having an average grain size of 100-130 μm after annealing, and a submicrocrystalline (SMC) one, having an average grain size of 0.30-0.50 μm after multi-cycle severe plastic deformation (SPD) processing via equal-channel anglar pressing (ECAP) combined with Conform. It is shown that for the samples produced by ECAP-Conform, having an SMC structure, the friction coefficients are 12 – 20% lower than for the as-annealed samples, having a CG structure.

  • Debye’s temperature and dimensional border between macro – and nano states

    pg(s) 49-52

    Debye’s temperature θD is the temperature border between areas, CμV(Т) has constant value and, when T<θD, begins to decrease monotonically. θD is the crystal parameter, which allows to calculate the dimensional border between macro- and nanostates. The statement which is found in scientific discussions that θD depends on temperature is incorrect because it contradicts modern crystal-physical theories. The numerical value θD is defined experimentally and is related to the structure of crystals and to the processes taking place in them.

  • Crack resistance evaluation for Al+3.5% Mg alloys by measurments of ultrasonic velocities and hardness

    pg(s) 53-59

    The crack resistance in fracture mechanics is defined as critical value of stress intensity factor in the plane-strain fracture toughness. A mechanical test is used to assess it under certain conditions. This is a complicated, long and expensive procedure. In practice, it is of interest to determine the crack resistance for construction elements by means non-destructive evaluations (NDE).