Machines. Technologies. Materials.
Vol. 20 (2026), Issue 1

Table of Contents

  • MACHINES

    • Analysis of risk in the development of device for field testing of anchor bolts

      pg(s) 3-6

      The subject of this paper is the analysis of technological risk by the combined application of the “Cause-Effect” method and the FMEA (Failure Mode and Effects Analysis) method, in the development of a device for technical testing of anchor bolts in field conditions. These methods are essential tools when it comes to risk analysis and management. In this research, an original solution of the testing device was given, which enables the testing of anchor bolts in a wide range. With this device, the most important parameters are monitored, which testify not only to the quality of the installation, but also to the quality of the base in which they are installed, as well as the anchor bolt itself. As the use of anchor bolts in responsible structures is increasing day by day, the need for research in the direction of testing these mechanical elements placed in the base, as critical components in many applications, naturally arises. The development of the initial prototype solution begins with the adoption of input parameters (type of anchor bolt, dimensions, geometric shape, expected load and tested spatial position), as well as output parameters that provide a reliable image of the behavior of the tested anchor bolt (displacement and actual axial force). Based on the adopted parameters, dimensioning, construction and production of technical drawings are carried out. Modern CAD CAE CAM systems that include 3D modeling and reproduction of prototypes from model materials will be used for rapid prototyping, and eco-friendly materials, processed using modern CNC technologies, will be used for the operational prototype of the device. The model’s functionality was tested in laboratory conditions. Applying methods for risk analysis and management allows us to improve design, increase safety and reliability, as well as measurement accuracy.

    • Segmental exergy analysis of a complex 210 mw three cylinder steam turbine

      pg(s) 7-10

      This paper presents exergy analysis results of a complex three cylinder steam turbine with nominal power 210 MW. The analysis is performed for each cylinder, cylinder part and whole turbine as well as for each segment of each turbine cylinder. In the observed turbine, Low Pressure Cylinder (LPC) has the highest exergy destruction (8668.15 kW) and the lowest exergy efficiency (87.19%), while Intermediate Pressure Cylinder (IPC) has the highest exergy efficiency (92.15%) of all cylinders. Exergy efficiency is the highest for each segment at each cylinder entrance and continuously decreases for all segments during steam expansion through each cylinder. In each cylinder, a segment which is the lowest influenced by the ambient temperature change is inlet segment – as steam expands through each cylinder, further segments became more and more influenced by the ambient temperature change. Steam re-heating process has a very beneficial influence on the exergy efficiency of the first two IPC segments (Seg. 3 and Seg. 4) which have the highest exergy efficiency in comparison to all other segments.

  • TECHNOLOGIES

    • Investigation of Cutting Edge Radius Influence on Tool Wear Using FEM Simulation in DEFORM 3D

      pg(s) 11-13

      This article presents a study of the influence of cutting edge rounding on the wear of monolithic milling tools using the finite element method (FEM) and DEFORM 3D software. After manufacturing by grinding, monolithic milling tools have considerably sharp cutting edges that are prone to breakage and chipping. Industrial practice and cutting edge zone theory recommend edge preparation to create a defined cutting edge radius. The optimal radius value depends on the machined material, cutting conditions, and other factors, and remains unclear. This study investigates the influence of the cutting edge radius on tool wear using 3D FEM simulation with the Usui wear model, which is considered suitable for machining processes. Initial simulations with sharp cutting edges were performed to determine the sensitivity of wear predictions to the Usui model constants. Subsequently, different cutting edge radii were simulated under identical cutting conditions. The simulation results demonstrate the relationship between cutting edge radius and wear progression. The findings provide guidelines for selecting suitable cutting edge preparation parameters to minimize tool wear when milling with monolithic tools.

    • Forecast-oriented optimization of production plans: closed-loop decision-making and model risk management

      pg(s) 14-17

      : This paper presents a forecast-oriented optimization framework for production and technological planning in modern metallurgical manufacturing systems. Forecasts of demand, raw material availability, and external constraints are widely used in the development of production plans; however, in traditional optimization models, forecast information is typically treated as a fixed input parameter, which leads to model risk and reduced robustness of decision-making. Within the proposed framework, forecasts are interpreted as dynamic and potentially inaccurate elements of the control system, and planning is performed in a closed-loop feedback structure integrating forecasting, model risk management, and optimization. The paper describes the architecture of an integrated forecast-oriented planning system and reports the results of computational experiments on the problem of forming a technological production plan for secondary aluminum alloys. The results demonstrate the impact of forecast accuracy on product cost and the computational complexity of the optimization process.

    • Finite Element Modeling of a Flat Reinforced Expanded Polytetrafluoroethylene Gasket

      pg(s) 18-21

      The porosity of flat ePTFE gaskets imposes requirements on the compression force during installation. Improving the tightness when using such gaskets is achieved by reinforcing them in a certain area. The combination of the complicated shape and the highly nonlinear properties of the material used necessitates the creation of an appropriate numerical model, through which to determine the compression force necessary to ensure the required tightness. In this work, a simulation using the finite element method has been created and used, which is based on the Marlow material model and a viscoelastic model of shear stress relaxation. Results have been obtained for the hydrostatic stress, the minimum principal strains and the fluid leakage path. The threshold values of the minimum principal strain at different magnitudes of the compression force have been determined.

    • Analytical-numerical approach for computation of welding residual stresses in large shell structures

      pg(s) 22-25

      In this paper, the inherent strain method is employed for the purpose of predicting welding residual stresses in large shell structures. Such structures include roof structures in the construction industry and deck sections in the shipbuilding industry. The study focuses on the numerical aspect of the inherent strain method, with the objective of investigating the most appropriate technique for transferring analytically calculated inherent strains into the elastic finite element model of the structure. The approach under consideration takes into account the thermally induced stresses, to the extent that they are considered to be significant for the structures and their behaviour in question, with the objective of determining the field of welding residual stresses over the entire structure (macro-scaled). The work proposes theoretical parameters for the alignment of finite element meshes within the weld seam domain. The discussion in the conclusion encompasses the general application capabilities, limitations, and challenges for further development

  • MATERIALS

    • Influence of femtosecond laser processing parameters on the surface morphology of titanium alloy

      pg(s) 26-29

      Titanium alloys are essential in biomedicine due to their high specific strength and biocompatibility, with surface properties directly influencing the successful osseointegration of implants. In this study, surface texturing of an experimental titanium alloy was performed using an ultrafast femtosecond laser with varying pulse energies. Roughness and topography were analysed using optical profilometry and confocal laser scanning microscopy, while microhardness was measured by the Vickers method. The results show that a pulse energy of 2.1 µJ, with a wavelength of 1030 nm, pulse duration of 190 fs, and repetition rate of 1 MHz, constitutes the optimal laser process parameters for achieving the desired surface properties in engineering and biomedical applications.

    • Observed Damage Patterns and Material Strength Deficiencies in URM Dwellings After the 2019 Albania Earthquake

      pg(s) 30-33

      This paper investigates the link between earthquake damage and material strength deficiencies in four unreinforced masonry (URM) dwellings in Kruja, Albania, which all reached Damage State 4 (DS-4) during the Mw 6.4 earthquake of 26 November 2019. Post-earthquake field inspections showed similar failure patterns in all buildings, including diagonal shear cracking, corner separation and local out-of-plane instability, pointing to limited shear capacity and weak masonry bonding.
      To clarify the causes of this behaviour, laboratory tests were carried out on brick units, mortar samples and masonry prisms taken from the damaged buildings. The test results indicate that both mortar and masonry compressive strengths are significantly lower than the values commonly assumed in Eurocode 6 for structural assessment. This strength deficit explains the brittle response and the rapid stiffness degradation observed during the earthquake.
      The combined use of field observations and laboratory data confirms the key role of construction quality in the seismic vulnerability of older URM dwellings and underlines the importance of material-based assessment approaches for similar residential buildings.

    • Structure and properties of AlB12-Al detonation coatings on Steel 45

      pg(s) 34-37

      The work is dedicated to the study of the properties of detonation coatings AlB12-30 wt.% Al (AB70) applied to Steel 45 using the DNEPR-5M installation. The coatings have the following characteristics: thickness h ~ 170-200 μm, Hμ = 27-29 GPa, HV = 4.35 GPa. Changes in the tribological characteristics of the composite depending on the friction mode are analyzed. The AB70 coating is found to have stable tribological characteristics: f = 0.21-0.38, wear rate I = 3.3-8.6 μm/km. Samples with coatings exceed uncoated Steel 45 in wear resistance. Changes in the surface structure after friction depending on the sliding speed and load are shown. Two wear mechanisms – oxidative and adhesive-abrasive – are established. A conclusion was drawn regarding the possibility of using the AlB12-Al system to apply detonation coatings.

    • Fermented grape pomace ash – by-product of rakia (brandy) production

      pg(s) 38-44

      This study investigates the chemical, mineralogical, and functional characteristics of fermented grape pomace ash generated after brandy production and subsequent combustion. Semi-quantitative WDXRF analysis revealed a Ca–K–P-dominated composition with high alkalinity, significant phosphorus content, and notable copper concentration. The water-soluble fraction of the ash was determined to be 17.1 wt.%, indicating a moderate content of mobile inorganic salts that may influence leaching behaviour and environmental compatibility. XRD and vibrational spectroscopy confirmed the presence of lime, calcite, silicates, sulphates, and calcium phosphate phases, including hydroxyapatite, together with a significant amorphous fraction and residual carbon. UV–Vis analysis indicated partial reduction of copper species to metallic nanoparticles, suggesting heterogeneous redox conditions during thermal treatment. The combined composition confers potential functionality in soil amendment, mineral carbonation for CO₂ sequestration, and incorporation into cementitious or alkali-activated systems, although soluble salts and copper mobility represent critical constraints, requiring application-specific environmental and performance assessment.