Browsing by Author "Bobukh, Oleksandr S."

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Determination of the Deformation Parameters of the Steel Reinforcing Phase inside the Aluminum Matrix during Hot Rolling
(Dnipro University of Technology, Dnipro, Ukraine, 2022) Nosko, Maxim I.; Konovodov, Dmytro V.; Samsonenko, Andrii A.; Bobukh, Oleksandr S.
ENG: Purpose. Comparison of deformation parameters during rolling of reinforced composites based on aluminum alloy using braided and expanded steel meshes as a reinforcing phase. Methodology. An experimental study on the effect of pressure on the deformation of the reinforcing phase during rolling of aluminum composites is carried out. A wire mesh and expanded mesh made of stainless steel was used as a reinforcing phase. The effect of deformation on the change in the lattice angle of the reinforcing phase is investigated. Findings. In this work, experimental data on the parameters of deformation of the wire mesh and expanded mesh are obtained. A comparison is made of the shape change in such grids under hot rolling conditions between two aluminum plates, which play the role of a matrix. It is found that the elongation coefficients of the lattice for the experiment with a wire mesh μc is equal to 1.68–2.3, which is greater than the coefficient of elongation of the lattice in the expanded mesh of 1.55–2.2. Therefore, expanded sheets make the best reinforcing layer for aluminumbased composites produced by the rollbonding process. Expanded mesh also reduces the risk of rupture at the intersection of wires. Originality. In the work, for the first time, a comparison of the deformation parameters during roll bonding of composites based on an aluminum alloy, reinforced with a braided and expanded steel mesh, has been given. Obtaining composite materials by means of hot roll bonding requires an understanding of the flow of composite components during deformation and their influence on each other. These peculiarities have not been studied sufficiently. Currently, there is no reliable method for predicting the behavior of the material of a solid reinforcing phase of various shapes inside a composite. Practical value. Advantages of using an expanded steel mesh for reinforcing aluminumbased composites have been confirmed. Scientific results can be used to refine calculating methods for metal flow at high hydrostatic pressure with variable components of the stress tensor and the major stresses.
Estimation of Glass Lubricant Viscosity for Hot Extrusion of Cr-Ni Steel and Ni Alloy Tubes
(Dnipro University of Technology, 2022) Medvedev, Michael; Shyfrin, Yevgen; Frolov, Yaroslav V.; Bobukh, Oleksandr S.
ENG: Purpose. Estimation of optimal viscosity of a glass lubricant for chromium-nickel steel tube extrusion depending on the deformation resistance, chemical composition of metal and the temperature, degree and rate of deformation. Methodology. To determine the force conditions for tube extrusion, a complex factor of deformation resistance was used, which consists in estimating the value of deformation resistance under the basic process parameters of extrusion plants and its refinement depending on the deviations of heating temperature and wall thickness of billets as well as the degree and rate of deformation from the base conditions. Findings. The dependence of basic values of deformation resistance on the percentage of alloying elements (Ni + Cr) in steels has been found. With the addition of hardening alloying elements (Mo, W, V, Nb) into the alloy steel, its deformation resistance increases in proportion to their percentage. Analytical expressions for calculating the base values of deformation resistance for different extrusion plants have been obtained. Originality. For the first time, the principles governing estimation of the optimal viscosity of glass lubricants based on the chemical composition of steel to be formed, its temperature and the degree and rate of deformation of the blank, thickness of the lubricating layer and geometric dimensions of the tool (die) in hot extrusion of tubes have been established. Practical value. The use of the results of calculation according to the developed method will make it possible to increase the surface quality of tubes manufactured by extrusion and reduce the volume of their subsequent machining.
Heat Balance of Billets during Hot Extrusion of Nickel Alloy Pipes
(Ukrainian State University of Science and Technologies, Dnipro, 2026) Medvedev, M. I.; Bobukh, Oleksandr S.; Kuzmina, O. M.; Krasiuk, A. D.; Ivanova, Liudmyla Kh.
ENG: Among the problems encountered in the production of nickel-based alloy pipes by hot extrusion sleeves on horizontal hydraulic presses, one of the main ones is the high level of product surface defects. To reduce rejects on this basis, it is important to understand the changes in the temperature field of the pipe billet throughout the entire technological process, since this factor is the key to the formation of surface defects in such pipes. The purpose of the work is to establish the regularities of temperature changes in nickel alloy pipe billets at the main stages of pipe production, which are made by extrusion on presses with a force of 16.0 MN and 31.5 MN with the use of glass lubricants. Methodology. The work was performed based on the results of a systematic analysis of the main technological stages of the actual process of producing hot-extruded pipes made of nickel alloy 602CA on presses with a force of 16.0 MN and 31.5 MN. The selected production stages include: transporting the billet (liner) from the induction heater to the glass-filled table, applying glass-filled material to the billet surface, transporting the billet with glass-filled material to the press, holding the billet in a container before extrusion, and extrusion in the container. The calculation of the stepwise temperature loss by the billet was performed using known and own empirical equations obtained from the results of thermography of the billets. The chemical composition of the billets was determined using an Elvax plus spectrometer. The temperature of the outer surface of the workpiece was measured using chromium-aluminium thermocouples complete with an electronic potentiometer. Results. It was found that the total change in the temperature of the sleeves during the cooling process during auxiliary operations on presses with a force of 16.0 MN and 31.5 MN at the same initial heating temperature of the workpieces is inversely proportional to their wall thickness. At the same time, this dependence is almost linear in the range of 40...120 mm wall thickness of the sleeves and 1050...1250 °C heating temperatures of the workpiece. Scientific novelty. For the first time, a methodology for calculating the temperature of the sleeves at the main stages of their preparation for the extrusion process has been developed. Practical utility. The use of the developed methodology for calculating the temperature of the liner allows for a reasonable choice of glass lubricant for the initial technological operations of extrusion on presses with a force of 16.0 MN and 31.5 MN using glass lubricant, which in turn contributes to improving the surface quality of pressed pipes, reducing the level of pipe rejects and reducing the volume of their the volume of their further mechanical processing.
Influence of Deformation Parameters on Mechanical Behaviour of Aluminium-Magnesium Roll-Bonded Composites with Kirigami-Structured Inlays
(Dnipro University of Technology, Dnipro, 2025) Frolov, Yaroslav V.; Nuernberger, Florian; Konovodov, Dmytro V.; Bobukh, Oleksandr S.; Boiarkin, Viacheslav V.
ENG: Purpose. To assess how the mechanical properties of a composite material comprising EN AW 1050 aluminium, and kirigami-inspired structure made from E235 steel and AZ31 magnesium alloy, depend on the initial configuration of its components and the degree of reduction during roll bonding. Methodology. The study involved roll-bonding five-layer composite sheets with the following configuration: two of the internal layers consisted of a kirigami structure implemented using an expanded metal mesh made from low-carbon steel. The outer matrix layers were aluminium alloy sheets, and the core matrix layer was formed from magnesium alloy sheets. The transformation of the kirigami structure within the composite was assessed using X-ray analysis. The mechanical properties of the composites were evaluated using three methods: impact bending tests, three-point bending tests and ball indentation tests. Findings. Experimental investigations yielded data on how the kirigami structure transforms within the five-layer composite, depending on the rolling reduction. It was found that a rolling reduction of 55 % provided an isotropic mechanical response. Mechanical testing showed that the energy absorption capacity was enhanced by 60–70 % with kirigami inlay, even under complex stress–strain conditions. The stiffness of the reinforced composite was found to be several times higher than that of unreinforced aluminium. Originality. This study is the pioneer in analysing the combined effect of component configuration and rolling reduction on the mechanical behaviour of a five-layer aluminium-magnesium composite reinforced with a steel kirigami structure. The study demonstrated that deformation parameters ensured reliable bonding between the aluminium and magnesium layers and significantly enhanced mechanical performance by controlling the transformation of the kirigami structure. Practical value. The findings of this study enhance our understanding of how rolling reduction and initial layer configuration affect the deformation behaviour of multilayer Al-Mg composites. They also lay the groundwork for designing novel composites reinforced with kirigami structures for advanced structural applications.
Kirigami Inspired Solid-State Alloying (KISA) Method of Creation of Functionally Graded Materials
(Український державний університет науки і технологій, ІВК «Системні технології», Дніпро, 2025) Frolov, Yaroslav V.; Bobukh, Oleksandr S.; Boiarkin, Viacheslav V.; Konovodov, Dmytro V.
ENG: Kirigami-inspired solid-state alloying (KISA) is an innovative technique that applies kirigami principles to control the distribution of alloying elements within a matrix during pressure bonding. By employing precise cuts and patterns, KISA manipulates diffusion and precipitate formation at micro- and nanoscale levels, leading to tailored material properties. This method eliminates challenges associated with conventional liquid alloying, such as oxidation and element loss, while enabling controlled microstructure evolution through roll bonding and heat treatment. Key advantages include improved phase distribution, enhanced interfacial properties, and adaptability for various material types, including powders and amorphous substances. KISA presents new opportunities for designing functionally graded materials with customized mechanical, electrical, and thermal characteristics.
Patterning of Surfaces for Subsequent Roll Bonding in a Low-Oxygen Environment Using Deformable Mesh Inlays
(MDPI, 2023) Frolov, Yaroslav V.; Bobukh, Oleksandr S.; Samsonenko, Andrii A.; Nürnberger, Florian
ENG: Efficient roll bonding for the manufacturing of clad strips not only requires surface activation but also is improved by a surface patterning to reduce the initial contact area. This increases contact stresses and facilitates a joining without an increasing rolling force. Experiments to pattern surfaces with deformable inlays during cold rolling for a subsequent bonding in low-oxygen atmosphere were carried out using two types of rolling mills, two types of inlays and two types of assemblies. Digital twins of selected experiments were created by means of the FE simulation software QForm UK 10.2.4. The main set of rolling parameters, which play a significant role during formation of the pattern shape considering deformation of the patterning tool, were investigated. The pilot roll bonding of patterned components under vacuum conditions, provided using vacuum sealer bags, allowed for an experimental realization of this approach. The concept technological chain of roll bonding in a low-oxygen or oxygen-free environment comprises the following stages: roll patterning; surface activation and sealing of the strips in a vacuum bag; subsequent roll bonding of the prepared strips inside the protective bag. The difference between the shape of the pattern created and the initial shape of the mesh insert can be quantitatively described by the change of its angle. This difference reaches maximum values when smaller rolls are used with increased rolling reductions. This maximum value is limited by the springback of the deformed insert; the limit is reached more easily if the inlay is not positioned on the rolling plane.
Roll Bonding of Al-Based Composite Reinforced with C10 Steel Expanded Mesh Inlay
(MDPI, Switzerland, 2021) Frolov, Yaroslav V.; Nosko, Maxim; Samsonenko, Andrii A.; Bobukh, Oleksandr S.; Remez, Oleg A.
ENG: The most complex issue related to the design of high efficiency composite materials is the behavior of the reinforcing component during the bonding process. This study presents numerical and experimental investigations of the shape change in the reinforcing inlay in an aluminum-steel mesh-aluminum composite during roll-bonding. A flat composite material consisting of two outer strips of an EN AW 1050 alloy and an inlay of expanded C10 steel mesh was obtained via hot roll bonding with nominal rolling reductions of 20%, 30%, 40% and 50% at a temperature of 500 °C. The experimental procedure was carried out using two separate rolling mills with diameters equal to 135 and 200 mm, respectively. A computer simulation of the roll bonding was performed using the finite element software QForm 9.0.10 by Micas Simulations Limited, Oxford, UK. The distortion of the mesh evaluated via the change in angle between its strands was described using computer tomography scanning. The dependence of the absorbed impact energy of the roll bonded composite on the parameters of the deformation zone was found. The results of the numerical simulation of the steel mesh shape change during roll bonding concur with the data from micro-CT scans of the composites. The diameter of rolls applied during the roll bonding, along with rolling reduction and temperature, have an influence on the resulting mechanical properties, i.e., the absorbed bending energy. Generally, the composites with reinforcement exhibit up to 20% higher impact energy in comparison with the non-reinforced composites. View Full-Text.
Solid-State Diffusion and Intermetallic Phase Formation in Roll-Bonded Mg–Zn Composites with Kirigami-Patterned Inlay
(Wiley-VCH GmbH, Weinheim, 2026) Frolov, Yaroslav V.; Bobukh, Oleksandr S.; Klose, Christian; Nürnberger, Florian; Maier, Hans Jürgen
ENG: Solid-state diffusion and intermetallic phase formation were examined in roll-bonded magnesium alloy–zinc (Mg–Zn) composites that contain a kirigami-patterned magnesium alloy (ZX10) inlay. The kirigami-patterned inlay was embedded between two zinc sheets and roll-bonded at 310°C. Subsequent heat treatments at 318°C and 328°C promoted interfacial diffusion as well as the formation of intermetallic phases. The kirigami geometry of the inlay was employed as a process-level tool to impose spatially inhomogeneous deformation during roll bonding. This caused localized stress concentrations, driving the controlled transformation of the initial pattern within the deformation zone. It also prevented the thin inlay from failing prematurely and ensured its controlled distribution along the sample. Inhomogeneous strain distribution introduced three-dimensional diffusion pathways that activated bonding and initiated phase transformation. Flexural testing revealed a significant increase in mechanical strength compared to values calculated using the rule of mixtures. The maximum strength observed was 100 MPa for samples heat-treated at 318°C. Microstructural analyses showed a progression from adhesive bonding (group A) to uniform intermetallic layers (group B) and complex, multiphase regions containing eutectic, dendritic, and porous fractions (group C). Energy-dispersive X-ray spectroscopy confirmed zinc diffusion into the magnesium solid solution, indicating the onset of solid-state alloying. The combined effects of plastic deformation, thermal activation, and the kirigami-patterned Zn inlay resulted in Mg–Zn composites with enhanced interfacial integrity and a tailored phase composition. These composites offer a promising pathway for advanced material compounds to be used in biomedical and mechanical applications.
Transformation of the Kirigami-Type Deformable Inlay during Roll Bonding
(Dnipro University of Technology, Dnipro, 2025) Frolov, Yaroslav V.; Konovodov, Dmytro V.; Bobukh, Oleksandr S.; Boiarkin, Viacheslav V.
ENG: Purpose. To quantitatively analyze the deformation of kirigami-type deformable inlays during the roll bonding process using soft outer matrices, with the goal of predicting their behavior within the composite structure. Methodology. The research involved the fabrication of three-layer composite sheets through roll bonding. Expanded meshes made of mild steel and stainless steel served as the inlay phase, while copper and aluminum alloy sheets were employed as matrix materials. The transformation of the inlay phase within the composite sheets was evaluated. Findings. The experimental investigation yielded data on the deformation behavior of kirigami-type inlays embedded within three-layer sheets during roll bonding. It was observed that using an aluminum matrix induces greater axial metal flow in the deformation zone, leading to a significant increase in the mesh distortion angle. A copper matrix primarily causes flattening of the mesh cells with minimal changes to their angular deformation. In contrast, rolling the steel mesh without a matrix results in negligible angular distortion until the rolling reduction exceeds 50 %. Originality. This study represents the first quantitative analysis of the geometric transformation of kirigami-type deformable inlays as a function of deformation magnitude and matrix material properties during roll bonding. Understanding the shape transformation of the reinforcing phase within the composite sheet enables more accurate prediction of the contact area between the matrix materials during the bonding process. Practical value. The findings of this research provide a basis for predicting the final geometry of kirigami structures within composite materials.