Machines. Technologies. Materials.
Vol. 13 (2019), Issue 4

Table of Contents

  • MACHINES

    • Reliability evaluation of electronic component in military vehicles under thermal exposure and thermal cycling by accelerated test method

      pg(s) 149-151

      The majority of electronic components are susceptible to damage at high temperatures (overheating) and their reliability is affected by its operating temperature. The temperature can basically dictate the effective performance as well as the lifetime or life cycle of the electronic components. In addition, the reliability of electronic components is not only affected temperatures but also by changes in temperature over a period of time (thermal cycles). This article describes the methodology how to prepare, perform and evaluate the accelerated reliability compliance test of electronic components in military vehicles under thermal exposure and thermal cycling.

    • Quality control of multi-pass weld by means of acoustic emission

      pg(s) 152-157

      The article proposes a method of assessing the quality of multi-pass weld by acoustic emission. The AE method involves the identification of developing defects at the stage of stress changes in the material, as well as in the statically loaded state. In the process of control two independent data collection systems were used, which worked in the process of testing synchronously. The selected method of control of the object has a number of advantages over other methods of NDT.

    • System for processing concentrated and non-condensing gases in boilers

      pg(s) 155-157

      A heat regeneration system is presented for the emptying of the lime boilers in a normally conventional lime-room to reduce the sulphur gases emitted from the blowing tank. The vapor passes through the pipes from the blowing tank to the blowing condensate reservoir for regeneration of valuable secondary heat. Non-condensing gases are discharged from the blowing condensate tank to the gas cooler and then additionally for combustion. The condenser formed in the heat recovery condenser is led to the sewer. Heat recovery system for the emptying of the lime boilers reduces both gas emissions and energy costs

    • Statistical analysis of locomotives traction motors performance

      pg(s) 158-161

      In this article the authors quoted results of traction motors speed performance variations statistical analysis and wage wheels bands diameters deviations according to operation data. The authors of this publication offered the method of determining the nonuniformities of current distribution in the power circuit of the locomotive, based on probabilistic approach, and also performed its comparison with classic computation approach. The next statistical performance of the continuous current locomotives traction drive is as follows: mathematical expectation of the motors magnetic flux; mean square deviation of magnetic flux; statistical dispersion and average square deviation of wage wheels bands diameters. With help of the received data it became possible to improve determination of nonuniformities currents deviations on traction motors during loading of the electric locomotives.

    • Exergy analysis of wet cooling tower at various loads and ambient temperatures

      pg(s) 162-165

      This paper presents an exergy analysis of wet cooling tower at three different loads and in a range of the ambient temperatures. Increase in cooling tower load increases its exergy destruction and simultaneously decreases cooling tower exergy efficiency, while an increase in the ambient temperature causes a decrease in cooling tower exergy destruction and simultaneously decreases its exergy efficiency. The lowest cooling tower exergy destructions (between 1417.54 kW and 2925.65 kW) are obtained at low load. The highest cooling tower exergy efficiencies are calculated at the lowest observed ambient temperature of 5 °C – they amount 64.31 % at low load, 54.80 % at middle load and 53.94 % at high load. The change in ambient temperature for 5 °C resulted with a change in cooling tower exergy efficiency of 4 % or more on average.

    • Preparation and properties of carbon adsorbents based on plant raw materials and polymeric waste

      pg(s) 166-170

      The object of the research is waste polyethylene, polypropylene, polyethyleneterephthalate and polyvinylchloride, which are subjected to pyrolysis utilization with plant raw materials as a carrier. The purpose of the study is the thermal processing of these wastes into carbon adsorbents and the analysis of their adsorption properties. Combinations of the most spread polymeric wastes and plant raw materials, as well as products of its transformation (wood, peat, lignite, coal and its coke) were studied as feedstocks for the production of carbon adsorbents. The temperature regime of pyrolysis of plant materials was determined according to the results of thermographic analysis. The effect of the type of raw materials and polymeric wastes on the yield and on the parameters of porous structure of the produced adsorbents was estimated and the high-quality samples among them were selected.

    • Supply chain planning methodology for metals

      pg(s) 171-172

      The paper contains the results of the study on the systematization and formalization of specialized approaches to planning supply chains of leading metal companies and comparison of these practices with the standard supply chain management models SCOR & CCOR & DCOR and GSCF. The paper defines the main directions of development of the methodology of supply chain planning in terms of its adaptation to the specifics of metals.

    • Traffic synthetic model development and calibration in Anamorava region

      pg(s) 173-177

      The main objective of this paper is to develop and calibrate traffic synthetic model for forecasting traffic demand in Anamorava region. The model on existing situation is developed based on “meta model” which uses PTV Visum software. In order to set up a model were taken into account input variables number of residents, number of people employed, working places available as well as the traffic volume entering and exiting this region at “peak hour”. With intention to have traffic volumes as an outcome expressed as AADT, correction coefficients are applied. Multiplying the traffic volumes with correction coefficient there is traffic demand gained for the period of 24 hours which is an indicator to be used for comparison of results. In order to get the reliable model for forecasting, calibration of it is done through TFlow Fuzzy algorithm technique based on GEH test, R2 and percentage deviation criterions. Once the level is completed satisfactory, the final model can be used to forecast the traffic demand for this region.

    • Research into the effect of certain chemical elements in microalloyed steel grades on concast slab and rolled plate surface quality

      pg(s) 178-182

      Investigators has developed a complex technology of manufacture of high quality skelp and shipbuilding grades and nickel-,chromium-, molybdenum-, niobium- and vanadium- microalloyed steels with carbon mass fraction within 0.06% to 0.22% and manganese mass fraction within 1.0% to 1.7%. Over the course of the research, relative occurrence of surface cracks of various morphology – transverse, longitudinal, spider, net-like – on the concast slab surface has been determined. The above research resulted in the development of a number of technological innovations both in preparation of liquid steel for casting and in continuous casting itself, preventing initiation or reducing by 30% – 40% the amount of surface defects on the rolled plates.

    • The influence of natural aging and pre-aging on the mechanical, physical and microstructural properties of the EN AW-6060 aluminum alloy

      pg(s) 187-189

      The aim of this paper is the investigation of the effect of natural aging on the mechanical, physical and microstructural properties of an EN AW-6060 aluminum alloy. These properties were investigated during different aging treatments. Firstly, the effect of natural aging on properties was investigated, after which the influence of natural aging (room temperature pre-aging) on the artificial aging was studied. The results showed the beneficial effect of natural aging in both sets of experiment. During the natural aging, the hardness increased for around 20 % while electrical conductivity values were slightly higher than in the quenched sample. The hardness of the samples gradually increases up to 25 days of natural aging reaching a plateau state, after which the values of hardness remain the same. Also, room temperature pre-aging had a positive effect on subsequent artificial aging. Samples that were pre-aged for 40 days or more before artificial aging had around a 13 % increase in hardness values compared to the samples that were directly artificially aged. Electrical conductivity had increased by around 1 MS/m in pre-aged samples compared to only artificially aged samples. Optical microscopy investigations confirmed the existence of precipitated phases and their distribution in the microstructure.

    • Materialscience – mathematics and physics for evaluation of liquids in foundry

      pg(s) 190-193

      The base process was obtained: 3D hardening temperature field for the K-test under heat transfer at conditions with maximum intensity. A methodology for determining macro-level defects in aluminum alloys. It is definitely the placement of the K-test method in the process of creating the first order phase transition in a casting technology. The idea of interaction between the classical theory of crystallization and quantum mechanics for the processes of structure formation at casting was introduced by Stefan’s task in volume with nano-size.

    • The maximal values of packing coefficient for particles with different forms

      pg(s) 194-197

      It was analyzed the methods of constructions the matter with maximal of packing coefficient when the objects consist of the particles with forms either spheres or rods or plates. It was calculated the relations the partial size for relating of maximal packing coefficient. As examples of objects with coefficient of packing theirs particles we look on abrasive materials and products of the powder metallurgy and solid fuel etc.