Table of Contents


    • Influence of trolley motion in the dynamic behavior of semi-portal cranes

      pg(s) 170-175

      The paper presents dynamic analysis of the Semi-Portal Cranes for the case of Trolley motion travelling on Crane’s Girders. Semi-portal cranes are mainly mounted in the industrial facilities, and they consist of metallic structures with big dimensions and many mechanisms that carry heavy loads. We will analyze the influence of the Trolley motion in the dynamic behavior of Semi-Portal Crane while carrying maximum Load, in particular the influence of Load swinging and oscillations. The method of analysis is acquiring experimental measurements and comparing those results with the results gained through modeling of crane, and carrying simulations. Designing the Crane’s 3D model with software and motion simulations is the method applied in the paper to analyze dynamics and is important to explain the form and intensity of oscillations that can cause accidents, failures of parts, and other concerns about the safety. Analysis will be done for maximal and minimal speed of the Trolley. Conclusions from this paper will be useful about the design, dynamic response and safety of Semi-Portal Cranes. The analysis will be focused to find main kinematic and dynamic parameters influencing the crane dynamics, like forces, moments, speed (velocity), and Load swinging magnitude. The Crane is modeled based on the Data from standard manufacturer of Semi-Portal Cranes.

    • A hoisting mechanism of clamshell cranes with a planetary gear train

      pg(s) 176-180

      Clamshell cranes are hoisting machines (machines with cyclic action) designed for handling bulk materials. The name of these cranes comes from the load gripping device – clamshell grab. In addition to the clamshell (two-jaw) grab for bulk materials, there are grabs designed for long-size and single loads. In the case of high-productivity bulk materials handling, double-rope clamshells are most suitable, which require a specialized clamshell crane with two hoisting mechanisms. The article discusses a reducer for a crane hoisting mechanism with an embedded planetary gear train (PGT), allowing the two ropes to move together, at the same speed, as well as independently of each other, or together at different speeds. The different modes of operation of the mechanism are considered. An analysis of the possible kinematic schemes of the PGT is made. The necessary kinematic calculations are made to select the most suitable variant of the PGT.


    • About the possibility of local laser hardening of the treed of railway wheels

      pg(s) 181-184

      The features of structural changes in the cove zone on the tread of worn out railway wheels were investigated. The influence of laser processing in pulsed and continuous mode on the nature of the structure and properties of wheel steel was shown. The influence of laser treatment on the increase in the hardness and wear resistance of wheel steel has been established. It was shown possibility and necessity of local laser hardening of cove zone of railway wheels tread by coming out of bainite structure. A method for improving the wear resistance of the tread by local laser treatment has been proposed.

    • Heat generated in the process of abrasion

      pg(s) 185-188

      The heat released during the grinding process is directly proportional to the size of the forces developed in the cutting process, which depend on the nature and mechanical properties of the workpiece material, the geometric parameters of the cutting tool, the properties of cutting fluids used during the machining process.
      Experimental research has confirmed the hypothesis that an increase in cutting speed leads to an increase in the amount of heat released and consequently to an increase in the temperature of the workpiece when using the same temperature control system. The paper presents the identification of heat sources in grinding process, as well as the distribution of heat to the elements which are part of the processing system.

    • Development of dual-function materials by utilization of coal combustion by-products for CO2 capture and conversion into synthetic fuel

      pg(s) 189-192

      The utilization of fly ash (FA) generated by the combustion of coal in thermal power plants instead of its disposal is a critical issue worldwide, which imposes the best available techniques and standards for sustainable practical application of this abundant resource. The present study considers an opportunity for smart utilization of fly ash from domestic Bulgarian lignite coal by its conversion into dualfunctional material with high adsorption capacity to capture carbon emissions and catalytic ability to convert them into synthetic fuel. FА with a high content of iron oxides, obtained as an average sample from the hydroseal of electrostatic precipitators of a Bulgarian coal-fired power plant, is converted by alkaline treatment to a zeolite-like material. Due to its favorable surface characteristics, the obtained material was tested for its adsorption potential toward CO2 at pressure of 5.5 MPa. High content of iron oxides uniformly distributed into the zeolite matrix is a prerequisite for the catalytic properties of the material, which contribute to the conversion of CO2 to methane, proven by infrared spectrophotometry and thermogravimetry combined with gas chromatography and mass-selective detector.


    • Virtual estimation of the intensity of deformation when producing samples from a magnesium alloy of the composition Mg-1% Ca by SPD methods according to ECAP and HPT schemes

      pg(s) 193-197

      The application of mathematical methods is one of the most rational approaches used to solve tasks of evaluating the efficiency of unconventional metal forming processes. Using computer simulation in the DEFORM-3D application software package, we performed virtual full factorial experiments for the processes of producing individual samples by equal-channel angular pressing (ECAP) and highpressure torsion (HPT) from the Mg-1%Ca magnesium alloy, taking assumptions into account. At the stage of the simulation task preparation, it was accepted that the most significant factors that influence the fabrication of defect-free semi-products by severe plastic deformation (SPD) via ECAP are the processing temperature and the number of processing cycles via route Вс. In both models, strain intensity was taken as the response parameter. To simulate the SPD process of HPT, the processing temperature and the number of revolutions were used as the main variable factors. In the virtual full factorial experiment, the effect of independent factors on strain intensity was evaluated. As a result of the experiments, regression equations were obtained, variants of the rational processing regimes for the investigated alloy were presented, and their effect on the response parameter was analyzed. The proposed and implemented numerical models allow us to recommend the ECAP processing of the Mg-1%Ca magnesium alloy at a deformation speed of 1.0 mm/s and temperature of about 350 °С for 2 – 4 cycles, and the HPT processing under a hydrostatic pressure of 6 GPa at room temperature with the number of revolutions from 3 to 5.

    • High-entropy alloy of Fe-Ti-Cr-Mn-Si-C system, produced by hot forging from powder mixtures of ferroalloys

      pg(s) 198-200

      The peculiarities of the structure and phase composition of the high-entropy alloy of the TiCrFeMnSiC system obtained from the powder mixture of ferrotitanium, ferrochrome and ferrosilicon-manganese ferroalloys are considered in the work. The technological scheme of alloy production included joint grinding of the mixture in a planetary mill, consolidation of the blanks, their heating to 1100 0C, hot forging on the arc press and subsequent annealing of hot-forged samples at 1200 0C. According to the results of X-ray analysis of the obtained alloy, it was found that the main phase of the alloy is the BCC phase with the parameter of the cubic lattice a = 0.2868 nm, which is a solid solution based on alloying components of the original charge. The phase composition of the composite also recorded ti tanium carbide TiC with FCC lattice with the parameter a = 0.4319 nm, which corresponds to a stoichiometric composition of about TiC0.6 and a small amount of FCC phase of iron-chromium carbide (Cr, Fe)23C6 with lattice parameter a = 1.0645 nm. The material has a high hardness (up to 60-61 HRC), which can provide high resistance of this multicomponent alloy.

    • The concept of energetic and technological compliance of components in materials science of fluorine composites

      pg(s) 201-204

      The structural and technological aspects of the polytetrafluoroethylene-matrix composites formation are shown. It is shown that due to the existence of inert components in the process of interfacial interaction with the degree of filling in the traditional technological paradigm implemented structural paradox manifests itself in proportion to the reduction of the parameter of tensile strength with increasing degree of filling. According to the concept of energy and technological compliance of components the technological principles to eliminate the negative impact of the structural paradox fluorine composites are proposed.

    • Preparation of specimens for standard tensile testing of plastic materials for FDM 3D printing

      pg(s) 205-208

      Additional manufacturing (AM), commonly known as 3D printing, exists for 40 years, still evolving and improving. AM has gained great popularity in modern industries due to many advantages concerning conventional manufacturing technologies. Consequently, AM is one of nine pillars of the currently dominating industry trend – Industry 4.0. Initially, AM was mostly used for making models. Now, objects made by AM technologies, often are physical parts ready to be used as final products or to be installed as parts of assemblies in more complex systems. Because of that, in more applications, the mechanical properties of these parts have to be known for the purpose to determine load carrying capacity essential for their functionality. Mechanical properties are being tested using appropriate methods, specimens, and equipment. In order to obtain comparable and evaluable test results, the test procedures and means should be s tandardized. Therefore, there was a need to develop standards for testing materials used for AM. International standardization in the field of AM started 10 years ago. The international body for standardization ISO developed and published a certain number of standards, but this is just beginning. This paper discusses aspects of AM standardization in the field of testing the mechanical properties of materials for 3D printing using fused deposition modelling (FDM). As an illustration of the standard application, specimens were prepared for testing the tensile properties of plastic materials widely used in AM: PLA, PETG and ABS+.

    • Advantages and disadvantages of fiberglass casing in oil and gas wells

      pg(s) 209-211

      Casing is an extremely important element in the process of drilling a well borehole, as they define the diameter of the well and, among many other tasks, protect it from collapsing. In order to ensure long-term successful performance of all tasks, it is necessary to appropriately dimension casing, which means that the appropriate inner and outer diameter should be selected with the appropriate material and its quality, with proper installation depth for each set of casing. Conventional casing made of steel is most often used and this is still an ideal material for most wells. However, this material is prone to corrosion, which is a major problem on certain locations du ring the
      production life of the well. Reduction and possibly elimination of corrosion on casing led the industry to explore financially viable composite materials, such as fiberglass, that could withstand expected stresses in well conditions with better corrosion resistance th an steel.