Machines. Technologies. Materials.
Vol. 19 (2025), Issue 2

Table of Contents

  • MACHINES

    • Designing and modeling of grapple buckets

      pg(s) 42-48

      The paper presents the process of automated designing and parametric modeling of grapple buckets using the CAD system. The presented grapple buckets are designed for bulk materials and they are part of the grapple construction. Grapples are installed on cranes, excavators and other specialized machines. A methodology has been developed that covers all stages of design – from the creation of 3D models of the parts, sub-assemblies and assemblies, to the generation of design documentation, using template files. The presented approach allows the creation of parametric models with multiple configurations, which cover different variants of the products. Using the presented methodology leads to a reduction in the volume of created documentation and optimizes the design process. Data management within a PDM system ensures centralized storage, actuality and accessibility of information.

    • Exergy analysis of several pressure reduction valves during operation in steam power plant

      pg(s) 49-52

      This paper presents an exergy analysis of six pressure reduction valves which operate in a condensate/feedwater heating system of a 660 MW coal-fired steam power plant. For all observed pressure reduction valves is additionally investigated the ambient temperature change influence of their exergy parameters. Second pressure reduction valve (PRV2) has the highest exergy destruction of all observed valves (equal to 1003.36 kW at the base ambient state). The first five observed pressure reduction valves (from PRV1 to PRV5) have very high exergy efficiencies at the base ambient state, higher than 90%. The last observed valve, PRV6, has an exergy efficiency at the base ambient state notably lower in comparison to other five valves, equal to 64.90% only. The exergy variables of any pressure reduction valve are more and more influenced by the ambient temperature change when the operating parameters of working fluid which flows through the valve (fluid pressure and temperature) are closer to the ambient state.

  • TECHNOLOGIES

    • Effect of laser power, welding speed and linear energy density factors to mechanical properties in fiber-laser welding of AISI 316 stainless steel

      pg(s) 53-56

      Austenitic stainless steels are widely used in various industries, including petrochemicals, food processing, and textiles, due to their excellent corrosion resistance, acceptable mechanical properties, and cost-effectiveness. Additionally, their good weldability makes laser welding a popular choice for manufacturing various designs. However, achieving optimal weld quality in laser welding requires precise and controlled adjustment of several key parameters. In this study, the effects of two fundamental process parameters—laser power and welding speed—on the mechanical properties of laser-welded AISI 316 stainless steel structures were investigated. For this purpose, a 2-factor, 3-level full factorial experimental design was implemented. The welded structures were subjected to tensile testing, and their microstructures were analysed.

    • Large-scale distortion analysis of the welding and thermal straightening process chain

      pg(s) 57-61

      An coupled analytic-numerical model for calculation of distortions arising by welding fabrication is introduced. Target of the analytical model is the calculation of the inherent strains after the local thermal-mechanical influence of the welding or thermal straightening process. Following the fabrication processing chart the strains are loaded on an elastic FE-model of the structure and the residual stresses and distortions of the whole structure are calculated. The consideration of welding and thermal straightening scenarios, inclusively the assembling stages, is done by taking into consideration the intermediate variation of the strain state in the FE-model of the structure at every processing step. The important physical relations are demonstrated. The model is intended to be used for solving industrial tasks, i.e. intending acceptable precision and calculation time as well as low simulation costs.

    • Application of HHO Gas for Effective Sterilization in Plasma-based Ion Implantation

      pg(s) 62-65

      Plasma-based ion implantation (PBII) is a surface modification technique that applies a negative high-voltage pulse to a sample immersed in plasma. PBII is suitable for samples with complex geometries, as its ion sheath conforms to the sample’s shape, ensuring uniform ion implantation. Due to its precise controllability, PBII is widely used industrially for surface modification and has promising applications for sterilization. We previously used PBII with oxygen gas to successfully sterilize heat-resistant spore. Here, we evaluated the use of PBII with HHO as the process gas for sterilization. Sterilization exceeding 7D was achieved at 10 min and 3 Pa. The enhancement of the sterilization efficacy was attributed to the synergistic effect of plasma and thermal energy, which emerged as a consequence of a temperature increase exceeding 100°C due to adjustments in pulse width and delay time. These results indicate the possibility for temperature control in PBII technology, which has potential application in sterilization processes.

  • MATERIALS

    • On the tribological characterization of novel SiNb and SiW cast irons

      pg(s) 66-68

      In this study, the tribological behavior of new generation cast irons (SiNb and SiW) developed as an alternative to cast irons containing high silicon and molybdenum (SiMo) is investigated under dry friction conditions. All cast irons are produced by sand mold casting as Y blocks according to ASTM A536-84 standard and metallurgical characterization studies have revealed that they all have spheroidal graphite and dispersed carbides like Mo-rich M6C, Nb-rich MC and W-rich M6C type depending on the alloying element, within a ferritic matrix. Although no significant change is observed in the spherical morphology of graphite in cast iron matrices, a significant change is observed in the amount of graphite and image analysis studies reveal that the graphite content (area-%) in SiNb and SiW cast irons is 4,02 and 4,30, respectively, compared to SiMo cast iron (5,80). A significant change in the hardness of cast irons is also determined depending on the microstructural features; SiNb (228 ± 7 HV10) and SiW (218 ± 5 HV10) cast irons have higher hardness values compared to SiMo cast iron (192 ± 5 HV10). Cast irons and alumina ball as counterpart material are subjected to a tribological interaction for 150 m under dry friction conditions at a nominal load of 10 N and a ball sliding speed of 0.08 m/s and the findings indicate that (i) the coefficient of friction (CoF) decreases as the graphite content increases, with SiMo having the lowest CoF (0.023), followed by SiW (0.025), and SiNb showing the highest CoF (0.040), (ii) the specific wear rate increases as the hardness decreases, therefore, SiMo has the highest specific wear rate, whereas SiNb demonstrates the lowest specific wear rate and (iii) adhesive wear is the dominant wear mechanism for all ductile cast irons due to the presence of their ferritic matrix.

    • Investigation of Bi2Te3 single crystal doped with Se obtained using Bridgman method

      pg(s) 69-70

      Researches in this paper included characterization of bismuth telluride single crystal doped with selenium. In order to study the effect of Se doping on the thermoelectric properties of Bi2Te2.7Se0.3 single crystal, an ingot was prepared by Bridgman method. The Bi2Te2.7Se0.3 single crystal in 11 mm × 80 mm size was grown.
      The obtained empirical formula does not deviate from the given compound formula. Bulk sample was characterized by Seebeck coefficient (S) as а function of temperature in the range of 40 – 320°C by а homemade impedance meter.

    • Advanced characterization methods of titanium alloy

      pg(s) 71-74

      In recent decades, increasing research in materials science and biomedical engineering has contributed to significant progress in biomedical metallic materials, some of which are titanium materials. The titanium used in the production of biomedical materials is usually alloyed with other elements such as niobium, molybdenum, copper and zirconium. Titanium alloys have become one of the most successful materials for biomedical applications, especially in orthopaedics and dentistry, due to their excellent biological, physical and mechanical properties. This article gives an overview of advanced characterization methods for titanium alloys such as light and electron microscopy, Xray diffraction, energy dispersive spectrometry, differential scanning calorimetry, differential thermal analysis, thermogravimetry and dynamic mechanical analysis. The article provides of the current status of the development of biomedical titanium alloys and use of advanced characterization methods, in the development of Ti-Cu alloys.

    • Influence of Al2O3 content on the mechanical properties of sintered Al-10Cu-xAl2O3 composites

      pg(s) 75-78

      This study investigates the influence of Al₂ O₃ content on the mechanical properties of sintered Al-10Cu-xAl₂ O₃ (x = 2.5, 5, and 7.5 wt.%) composite materials, produced via powder metallurgy and subjected to quasi-static and dynamic compressive loadings. Quasistatic tests were performed at a constant strain rate of 0.003 s⁻ ¹, while dynamic tests were conducted at strain rates corresponding to impact velocities of approximately 10 m/s and 20 m/s. The results indicate that a higher Al₂ O₃ content enhances the mechanical properties of the composite under both quasi-static and dynamic compression. The most significant improvements were observed under high strain rate impact loading, highlighting the potential of sintered Al-10Cu-xAl₂ O₃ for applications in dynamic environments.

    • Lightweight heavy geopolymer foam based on fayalite slag: Influence of alkali concentration on cellular structure

      pg(s) 79-82

      The lightweight cellular building materials has driven significant interest recently due to increasing requirements of energy efficiency of the buildings. This study investigates the potential of fayalite slag, a by-product of copper production, as a precursor for lightweight geopolymer foams. Geopolymer foams were synthesized using a combination of fayalite slag and metakaolin, employing gas forming agents to achieve a porous cellular macrostructure. The influence of alkali concentration was examined on the cellular structure, physical properties and microstructure (FT-IR) of the resulting materials. The findings contribute to the development of sustainable, highperformance geopolymer materials suitable for insulation and fire-resistant applications.