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This study investigates the shape memory behavior of epoxy-based pultruded flat laminates reinforced with unidirectional glass fibers. To evaluate the shape memory performance of the composite material, a series of tests by bending flat specimens to the shape programming angle has been conducted. The shape fixity and shape recovery ratios for the pultruded composite specimens with 90° fiber orientation constituted 78.4% and 92.6%, respectively, and 13.3% and 91.9%, for specimens with 0° fiber orientation. The results obtained in this study show that the shape fixity and recovery ratios of the composite material are only slightly dependent on the shape programming angle and the number of shape memory cycles (up to 10 cycles). The study also determined the shape fixity and shape recovery ratios for cured resin specimens, which constituted 99.7% and 98.2%, respectively. To lay the foundation for further studies on the simulation and optimization of the pultrusion process, the resin cure kinetics, the thermomechanical and thermophysical properties of the cured resin, and the mechanical characteristics of the pultruded shape memory polymer composite were analyzed.
Roman Korotkov; Alexander Vedernikov; Sergey Gusev; Omar Alajarmeh; Iskander Akhatov; Alexander Safonov. Shape memory behavior of unidirectional pultruded laminate. Composites Part A: Applied Science and Manufacturing 2021, 150, 106609 .
AMA StyleRoman Korotkov, Alexander Vedernikov, Sergey Gusev, Omar Alajarmeh, Iskander Akhatov, Alexander Safonov. Shape memory behavior of unidirectional pultruded laminate. Composites Part A: Applied Science and Manufacturing. 2021; 150 ():106609.
Chicago/Turabian StyleRoman Korotkov; Alexander Vedernikov; Sergey Gusev; Omar Alajarmeh; Iskander Akhatov; Alexander Safonov. 2021. "Shape memory behavior of unidirectional pultruded laminate." Composites Part A: Applied Science and Manufacturing 150, no. : 106609.
Cure-induced deformations are inevitable in pultruded composite profiles due to the peculiarities of the pultrusion process and usually require the use of costly shimming operations at the assembly stage for their compensation. Residual stresses formed at the production and assembly stages impair the mechanical performance of pultruded elements. A numerical technique that would allow the prediction and reduction of cure-induced deformations is essential for the optimization of the pultrusion process. This study is aimed at the development of a numerical model that is able to predict spring-in in pultruded L-shaped profiles. The model was developed in the ABAQUS software suite with user subroutines UMAT, FILM, USDFLD, HETVAL, and UEXPAN. The authors used the 2D approach to describe the thermochemical and mechanical behavior via the modified Cure Hardening Instantaneous Linear Elastic (CHILE) model. The developed model was validated in two experiments conducted with a 6-month interval using glass fiber/vinyl ester resin L-shaped profiles manufactured at pulling speeds of 200, 400, and 600 mm/min. Spring-in predictions obtained with the proposed numerical model fall within the experimental data range. The validated model has allowed authors to establish that the increase in spring-in values observed at higher pulling speeds can be attributed to a higher fraction of uncured material in the composite exiting the die block and the subsequent increase in chemical shrinkage that occurs under unconstrained conditions. This study is the first one to isolate and evaluate the contributions of thermal and chemical shrinkage into spring-in evolution in pultruded profiles. Based on this model, the authors demonstrate the possibility of achieving the same level of spring-in at increased pulling speeds from 200 to 900 mm/min, either by using a post-die cooling tool or by reducing the chemical shrinkage of the resin. The study provides insight into the factors significantly affecting the spring-in, and it analyzes the methods of spring-in reduction that can be used by scholars to minimize the spring-in in the pultrusion process.
Alexander Vedernikov; Alexander Safonov; Fausto Tucci; Pierpaolo Carlone; Iskander Akhatov. Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds. Polymers 2021, 13, 2748 .
AMA StyleAlexander Vedernikov, Alexander Safonov, Fausto Tucci, Pierpaolo Carlone, Iskander Akhatov. Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds. Polymers. 2021; 13 (16):2748.
Chicago/Turabian StyleAlexander Vedernikov; Alexander Safonov; Fausto Tucci; Pierpaolo Carlone; Iskander Akhatov. 2021. "Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds." Polymers 13, no. 16: 2748.
Additive manufacturing erases the distance between design ideas and finished parts. However, designers must use several software tools to use these advantages. Moreover, these tools operate with different representations of geometry. This paper describes the architecture of a new CAD/CAM system that uses only the function representation of the geometry (FRep). It provides all widely used design operations and allows an engineer to employ robust and efficient topology optimization algorithms. The developed CAD/CAM system consists of 3D modeling, simulation, topology optimization, and direct manufacturing modules. We successfully printed designed parts and performed mechanical tests of printed parts. The results of tests show good agreement with simulation data. The system makes it possible to create structures with the desired properties in a fast and flexible way. The proposed approach significantly helps in designing additive manufacturing process and saves time for its users.
Dmitry Popov; Yulia Kuzminova; Evgenii Maltsev; Stanislav Evlashin; Alexander Safonov; Iskander Akhatov; Alexander Pasko. CAD/CAM System for Additive Manufacturing with a Robust and Efficient Topology Optimization Algorithm Based on the Function Representation. Applied Sciences 2021, 11, 7409 .
AMA StyleDmitry Popov, Yulia Kuzminova, Evgenii Maltsev, Stanislav Evlashin, Alexander Safonov, Iskander Akhatov, Alexander Pasko. CAD/CAM System for Additive Manufacturing with a Robust and Efficient Topology Optimization Algorithm Based on the Function Representation. Applied Sciences. 2021; 11 (16):7409.
Chicago/Turabian StyleDmitry Popov; Yulia Kuzminova; Evgenii Maltsev; Stanislav Evlashin; Alexander Safonov; Iskander Akhatov; Alexander Pasko. 2021. "CAD/CAM System for Additive Manufacturing with a Robust and Efficient Topology Optimization Algorithm Based on the Function Representation." Applied Sciences 11, no. 16: 7409.
Complex 3D objects with microstructures can be modelled using the function representation (FRep) approach and then manufactured. The task of modelling a geometric object with a sophisticated microstructure based on unit cell repetition is often too computationally expensive for CAD systems. FRep provides efficient tools to solve this problem. However, even for FRep the slicing step required for manufacturing can take a significant amount of time. An accelerated slicing algorithm for FRep 3D objects is proposed in this paper. This algorithm allows the preparation of FRep models for 3D printing without surface generation stage. The spatial index is employed to accelerate the slicing process. A novel compound adaptive criterion and a novel acceleration criterion are proposed to speed up the evaluation of the defining function of an FRep object. The use of these criteria is significantly reducing the computational time for contour construction during the slicing process. The K-d tree and R-tree data structures are used as spatial indexes. The performance of the accelerated slicing algorithm was tested. The contouring time was reduced 100-fold due to using the novel compound adaptive criterion with the novel acceleration criterion.
Evgenii Maltsev; Dmitry Popov; Svyatoslav Chugunov; Alexander Pasko; Iskander Akhatov. An Accelerated Slicing Algorithm for Frep Models. Applied Sciences 2021, 11, 6767 .
AMA StyleEvgenii Maltsev, Dmitry Popov, Svyatoslav Chugunov, Alexander Pasko, Iskander Akhatov. An Accelerated Slicing Algorithm for Frep Models. Applied Sciences. 2021; 11 (15):6767.
Chicago/Turabian StyleEvgenii Maltsev; Dmitry Popov; Svyatoslav Chugunov; Alexander Pasko; Iskander Akhatov. 2021. "An Accelerated Slicing Algorithm for Frep Models." Applied Sciences 11, no. 15: 6767.
Water droplets released from the sea surface represent one of the major causes of ice accretion on marine vessels. A one-dimensional model of the freezing of a spherical water droplet moving in cold air was developed. The crystallization model allows one to obtain an analytical solution if a uniform temperature distribution over the liquid’s core is assumed. The model was validated using STAR CCM+ Computational fluid dynamics (CFD) code. A collision of a partially frozen droplet with a solid wall assuming the plastic deformation of an ice crust was also considered. The ratio of the crust deformation to the crust thickness was evaluated. It was assumed that if this ratio were to exceed unity, the droplet would stick to the wall’s surface due to ice bridge formation caused by the water released from the droplet’s core.
Doston Shayunusov; Dmitry Eskin; Boris Balakin; Svyatoslav Chugunov; Stein Johansen; Iskander Akhatov. Modeling Water Droplet Freezing and Collision with a Solid Surface. Energies 2021, 14, 1020 .
AMA StyleDoston Shayunusov, Dmitry Eskin, Boris Balakin, Svyatoslav Chugunov, Stein Johansen, Iskander Akhatov. Modeling Water Droplet Freezing and Collision with a Solid Surface. Energies. 2021; 14 (4):1020.
Chicago/Turabian StyleDoston Shayunusov; Dmitry Eskin; Boris Balakin; Svyatoslav Chugunov; Stein Johansen; Iskander Akhatov. 2021. "Modeling Water Droplet Freezing and Collision with a Solid Surface." Energies 14, no. 4: 1020.
This review discusses the development prospects of additive technologies for the manufacturing of complex technological items on the surface of the Moon under scarce resource availability and low-gravity conditions. One of the expected materials for 3D printing as part of a prospective lunar research program is the lunar regolith. It is easily accessible on the Moon in a few forms, depending on geographical location. Due to the limited availability of the lunar regolith on Earth, several attempts to use geological simulants of the regolith were made by research groups worldwide to analyze the applicability of additive manufacturing (AM) technologies for lunar 3D printing. The present review is aimed at discussing recent achievements in the development of chemical and technological aspects of 3D-printing technology for the use of the lunar regolith. A detailed description of all known AM approaches is presented, and the results obtained by various research groups are compared and discussed. All available experiments with 3D printing for in-situ fabrication with lunar regolith were analyzed, systematized, and generalized. Finally, we have formulated the basic requirements and approaches for adapting additive manufacturing methods to lunar surface conditions.
Maxim Isachenkov; Svyatoslav Chugunov; Iskander Akhatov; Igor Shishkovsky. Regolith-based additive manufacturing for sustainable development of lunar infrastructure – An overview. Acta Astronautica 2021, 180, 650 -678.
AMA StyleMaxim Isachenkov, Svyatoslav Chugunov, Iskander Akhatov, Igor Shishkovsky. Regolith-based additive manufacturing for sustainable development of lunar infrastructure – An overview. Acta Astronautica. 2021; 180 ():650-678.
Chicago/Turabian StyleMaxim Isachenkov; Svyatoslav Chugunov; Iskander Akhatov; Igor Shishkovsky. 2021. "Regolith-based additive manufacturing for sustainable development of lunar infrastructure – An overview." Acta Astronautica 180, no. : 650-678.
Pultrusion is one of the most efficient methods of producing polymer composite structures with a constant cross-section. Pultruded profiles are widely used in bridge construction, transportation industry, energy sector, and civil and architectural engineering. However, in spite of the many advantages thermoplastic composites have over the thermoset ones, the thermoplastic pultrusion market demonstrates significantly lower production volumes as compared to those of the thermoset one. Examining the thermoplastic pultrusion processes, raw materials, mechanical properties of thermoplastic composites, process simulation techniques, patents, and applications of thermoplastic pultrusion, this overview aims to analyze the existing gap between thermoset and thermoplastic pultrusions in order to promote the development of the latter one. Therefore, observing thermoplastic pultrusion from a new perspective, we intend to identify current shortcomings and issues, and to propose future research and application directions.
Kirill Minchenkov; Alexander Vedernikov; Alexander Safonov; Iskander Akhatov. Thermoplastic Pultrusion: A Review. Polymers 2021, 13, 180 .
AMA StyleKirill Minchenkov, Alexander Vedernikov, Alexander Safonov, Iskander Akhatov. Thermoplastic Pultrusion: A Review. Polymers. 2021; 13 (2):180.
Chicago/Turabian StyleKirill Minchenkov; Alexander Vedernikov; Alexander Safonov; Iskander Akhatov. 2021. "Thermoplastic Pultrusion: A Review." Polymers 13, no. 2: 180.
The particle size distribution significantly affects the material properties of the additively manufactured parts. In this work, the influence of bimodal powder containing nano- and micro-scale particles on microstructure and materials properties is studied. Moreover, to study the effect of the protective atmosphere, the test samples were additively manufactured from 316L stainless steel powder in argon and nitrogen. The samples fabricated from the bimodal powder demonstrate a finer subgrain structure, regardless of protective atmospheres and an increase in the Vickers microhardness, which is in accordance with the Hall-Petch relation. The porosity analysis revealed the deterioration in the quality of as-built parts due to the poor powder flowability. The surface roughness of fabricated samples was the same regardless of the powder feedstock materials used and protective atmospheres. The results suggest that the improvement of mechanical properties is achieved by adding a nano-dispersed fraction, which dramatically increases the total surface area, thereby contributing to the nitrogen absorption by the material.
Aleksandr M. Filimonov; Oleg A. Rogozin; Denis G. Firsov; Yulia O. Kuzminova; Semen N. Sergeev; Alexander P. Zhilyaev; Marat I. Lerner; Nikita E. Toropkov; Alexey P. Simonov; Ivan I. Binkov; Ilya V. Okulov; Iskander S. Akhatov; Stanislav A. Evlashin. Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction. Materials 2020, 14, 115 .
AMA StyleAleksandr M. Filimonov, Oleg A. Rogozin, Denis G. Firsov, Yulia O. Kuzminova, Semen N. Sergeev, Alexander P. Zhilyaev, Marat I. Lerner, Nikita E. Toropkov, Alexey P. Simonov, Ivan I. Binkov, Ilya V. Okulov, Iskander S. Akhatov, Stanislav A. Evlashin. Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction. Materials. 2020; 14 (1):115.
Chicago/Turabian StyleAleksandr M. Filimonov; Oleg A. Rogozin; Denis G. Firsov; Yulia O. Kuzminova; Semen N. Sergeev; Alexander P. Zhilyaev; Marat I. Lerner; Nikita E. Toropkov; Alexey P. Simonov; Ivan I. Binkov; Ilya V. Okulov; Iskander S. Akhatov; Stanislav A. Evlashin. 2020. "Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction." Materials 14, no. 1: 115.
In the present investigation, the plasma electrolytic oxidation (PEO) process was employed to form aluminum oxide coating layers to enhance corrosion resistance properties of high-strength aluminum alloys. The formed protective coating layers were examined by means of scanning electron microscopy (SEM) and characterized by several electrochemical techniques, including open circuit potential (OCP), linear potentiodynamic polarization (LP) and electrochemical impedance spectroscopy (EIS). The results were reported in comparison with the bare 6061-O aluminum alloy to determine the corrosion performance of the coated 6061-O alloy. The PEO-treated aluminum alloy showed substantially higher corrosion resistance in comparison with the untreated substrate material. A relationship was found between the coating formation stage, process parameters and the thickness of the oxide-formed layers, which has a measurable influence on enhancing corrosion resistance properties. This study demonstrates promising results of utilizing PEO process to enhance corrosion resistance properties of high-strength aluminum alloys and could be recommended as a method used in industrial applications.
Dmitry V. Dzhurinskiy; Stanislav S. Dautov; Petr G. Shornikov; Iskander Sh. Akhatov. Surface Modification of Aluminum 6061-O Alloy by Plasma Electrolytic Oxidation to Improve Corrosion Resistance Properties. Coatings 2020, 11, 4 .
AMA StyleDmitry V. Dzhurinskiy, Stanislav S. Dautov, Petr G. Shornikov, Iskander Sh. Akhatov. Surface Modification of Aluminum 6061-O Alloy by Plasma Electrolytic Oxidation to Improve Corrosion Resistance Properties. Coatings. 2020; 11 (1):4.
Chicago/Turabian StyleDmitry V. Dzhurinskiy; Stanislav S. Dautov; Petr G. Shornikov; Iskander Sh. Akhatov. 2020. "Surface Modification of Aluminum 6061-O Alloy by Plasma Electrolytic Oxidation to Improve Corrosion Resistance Properties." Coatings 11, no. 1: 4.
3D printing allows the fabrication of ceramic implants, making a personalized approach to patients’ treatment a reality. In this work, we have tested the applicability of the Function Representation (FRep) method for geometric simulation of implants with complex cellular microstructure. For this study, we have built several parametric 3D models of 4 mm diameter cylindrical bone implant specimens of four different types of cellular structure. The 9.5 mm long implants are designed to fill hole defects in the trabecular bone. Specimens of designed ceramic implants were fabricated at a Ceramaker 900 stereolithographic 3D printer, using a commercial 3D Mix alumina (Al2O3) ceramic paste. Then, a single-axis compression test was performed on fabricated specimens. According to the test results, the maximum load for tested specimens constituted from 93.0 to 817.5 N, depending on the size of the unit cell and the thickness of the ribs. This demonstrates the possibility of fabricating implants for a wide range of loads, making the choice of the right structure for each patient much easier.
Alexander Safonov; Evgenii Maltsev; Svyatoslav Chugunov; Andrey Tikhonov; Stepan Konev; Stanislav Evlashin; Dmitry Popov; Alexander Pasko; Iskander Akhatov. Design and Fabrication of Complex-Shaped Ceramic Bone Implants via 3D Printing Based on Laser Stereolithography. Applied Sciences 2020, 10, 7138 .
AMA StyleAlexander Safonov, Evgenii Maltsev, Svyatoslav Chugunov, Andrey Tikhonov, Stepan Konev, Stanislav Evlashin, Dmitry Popov, Alexander Pasko, Iskander Akhatov. Design and Fabrication of Complex-Shaped Ceramic Bone Implants via 3D Printing Based on Laser Stereolithography. Applied Sciences. 2020; 10 (20):7138.
Chicago/Turabian StyleAlexander Safonov; Evgenii Maltsev; Svyatoslav Chugunov; Andrey Tikhonov; Stepan Konev; Stanislav Evlashin; Dmitry Popov; Alexander Pasko; Iskander Akhatov. 2020. "Design and Fabrication of Complex-Shaped Ceramic Bone Implants via 3D Printing Based on Laser Stereolithography." Applied Sciences 10, no. 20: 7138.
Evolution of additively manufactured (AM) ceramics’ microstructure between manufacturing stages is a hardly explored topic. These data are of high demand for advanced numerical modeling. In this work, 3D microstructural models of Al2O3 greenbody, brownbody and sintered material are presented and analyzed, for ceramic samples manufactured with SLA-based AM workflow, using a commercially available ceramic paste and 3D printer. The novel data, acquired at the micro- and mesoscale, using Computed Tomography (CT), Scanning Electron Microscopy (SEM) and Focused Ion-Beam SEM (FIB/SEM) techniques, allowed a deep insight into additive ceramics characteristics. We demonstrated the spatial 3D distribution of ceramic particles, an organic binder and pores at every stage of AM workflow. The porosity of greenbody samples (1.6%), brownbody samples (37.3%) and sintered material (4.9%) are analyzed. Pore distribution and possible originating mechanisms are discussed. The location and shape of pores and ceramic particles are indicative of specific physical processes driving the ceramics manufacturing. We will use the presented microstructural 3D models as input and verification data for advanced numerical simulations developed in the project.
Svyatoslav Chugunov; Nikolaus Adams; Iskander Akhatov. Evolution of SLA-Based Al2O3 Microstructure During Additive Manufacturing Process. Materials 2020, 13, 3928 .
AMA StyleSvyatoslav Chugunov, Nikolaus Adams, Iskander Akhatov. Evolution of SLA-Based Al2O3 Microstructure During Additive Manufacturing Process. Materials. 2020; 13 (18):3928.
Chicago/Turabian StyleSvyatoslav Chugunov; Nikolaus Adams; Iskander Akhatov. 2020. "Evolution of SLA-Based Al2O3 Microstructure During Additive Manufacturing Process." Materials 13, no. 18: 3928.
3D printing using fused composite filament fabrication technique (FFF) allows prototyping and manufacturing of durable, lightweight, and customizable parts on demand. Such composites demonstrate significantly improved printability, due to the reduction of shrinkage and warping, alongside the enhancement of strength and rigidity. In this work, we use polypropylene filament reinforced by short glass fibers to demonstrate the effect of fiber orientation on mechanical tensile properties of the 3D printed specimens. The influence of the printed layer thickness and raster angle on final fiber orientations was investigated using X-ray micro-computed tomography. The best ultimate tensile strength of 57.4 MPa and elasticity modulus of 5.5 GPa were obtained with a 90° raster angle, versus 30.4 MPa and 2.5 GPa for samples with a criss-cross 45°, 135° raster angle, with the thinnest printed layer thickness of 0.1 mm.
Eugene Shulga; Radmir Karamov; Ivan S. Sergeichev; Stepan D. Konev; Liliya I. Shurygina; Iskander S. Akhatov; Sergey D. Shandakov; Albert G. Nasibulin. Fused Filament Fabricated Polypropylene Composite Reinforced by Aligned Glass Fibers. Materials 2020, 13, 3442 .
AMA StyleEugene Shulga, Radmir Karamov, Ivan S. Sergeichev, Stepan D. Konev, Liliya I. Shurygina, Iskander S. Akhatov, Sergey D. Shandakov, Albert G. Nasibulin. Fused Filament Fabricated Polypropylene Composite Reinforced by Aligned Glass Fibers. Materials. 2020; 13 (16):3442.
Chicago/Turabian StyleEugene Shulga; Radmir Karamov; Ivan S. Sergeichev; Stepan D. Konev; Liliya I. Shurygina; Iskander S. Akhatov; Sergey D. Shandakov; Albert G. Nasibulin. 2020. "Fused Filament Fabricated Polypropylene Composite Reinforced by Aligned Glass Fibers." Materials 13, no. 16: 3442.
The present paper is focused on an experimental study of the damage-to-failure mechanism of additively manufactured 316L stainless steel specimens subjected to very high cycle fatigue (VHCF) loading. Ultrasonic axial tension-compression tests were carried out on specimens for up to 109 cycles, and fracture surface analysis was performed. A fine granular area (FGA) surrounding internal defects was observed and formed a “fish-eye” fracture type. Nonmetallic inclusions and the lack of fusion within the fracture surfaces that were observed with SEM were assumed to be sources of damage initiation and growth of the FGAs. The characteristic diameter of the FGAs was ≈500 mm on the fracture surface and were induced by nonmetallic inclusions; this characteristic diameter was the same as that for the fracture surface induced by a lack of fusion. Fracture surfaces corresponding to the high cycle fatigue (HCF) regime were discussed as well to emphasize damage features related to the VHCF regime.
Boris Voloskov; Stanislav Evlashin; Sarkis Dagesyan; Sergey Abaimov; Iskander Akhatov; Ivan Sergeichev. Very High Cycle Fatigue Behavior of Additively Manufactured 316L Stainless Steel. Materials 2020, 13, 3293 .
AMA StyleBoris Voloskov, Stanislav Evlashin, Sarkis Dagesyan, Sergey Abaimov, Iskander Akhatov, Ivan Sergeichev. Very High Cycle Fatigue Behavior of Additively Manufactured 316L Stainless Steel. Materials. 2020; 13 (15):3293.
Chicago/Turabian StyleBoris Voloskov; Stanislav Evlashin; Sarkis Dagesyan; Sergey Abaimov; Iskander Akhatov; Ivan Sergeichev. 2020. "Very High Cycle Fatigue Behavior of Additively Manufactured 316L Stainless Steel." Materials 13, no. 15: 3293.
The solidification of an undercooled liquid is physically unstable. The dominating instability modes are affected by both the evolving temperature field in the solid and liquid phases, and characteristics of the phase interface such as the curvature and the propagation velocity. To capture the instability mode, therefore both the temperature field and the interface have to be represented accurately in a numerical model of the phase-change process. In this work, we develop conservative interface exchange terms for a sharp-interface formulation of liquid-solid phase transition. Conservation at the interface is maintained by explicit formulation of interface fluxes into both solid and liquid phases. We propose a semi-implicit level-set formulation to evolve the phase interface. A new formulation for the interface surface in a cut cell is derived, which includes the Stefan condition. We achieve low numerical dissipation by an explicit third-order Runge-Kutta scheme for time discretization, and a novel WENO-like (Weighted Essentially Non-Oscillatory) interface-gradient reconstruction. This distinguishes our level-set based sharp-interface model from previous level-set based approaches, which rely on finite-difference based interface treatment, and thus do not ensure discrete conservation at the interface. The flux terms in our approach take into account surface-tension and kinetic effects on the interface temperature (Gibbs-Thomson relation). The Stefan condition provides a relation between interface fluxes of mass and energy, and the interface-propagation velocity. Computational efficiency is maintained by a multiresolution approach for local mesh adaptation, and an adaptive local time-stepping scheme. We present one- and two-dimensional simulation results for the growth of a planar solidification front and a single parabolic dendrite affected by surface tension. The results agree well with experimental and analytical reference data, showing that the model is capable to capture both stable (planar) and unstable (dendritic-like) growth processes in the heat-diffusion dominated regime. The convergence order for successively finer meshes in the one-dimensional case is one for the interface location and the temperature field, outperforming previously reported level-set based approaches. We present numerical data of a growing crystal with four-fold symmetry. Our results indicate that the artificial dissipation of the underlying numerical scheme affects its capability to reproduce consistently physical tip-splitting instabilities. The proposed low-dissipation scheme is able to resolve such instabilities. Finally, we demonstrate the capability of the method to simulate multiple growing crystals with anisotropic surface-tension and kinetic effects.
J.W.J. Kaiser; S. Adami; I.S. Akhatov; N.A. Adams. A semi-implicit conservative sharp-interface method for liquid-solid phase transition. International Journal of Heat and Mass Transfer 2020, 155, 119800 .
AMA StyleJ.W.J. Kaiser, S. Adami, I.S. Akhatov, N.A. Adams. A semi-implicit conservative sharp-interface method for liquid-solid phase transition. International Journal of Heat and Mass Transfer. 2020; 155 ():119800.
Chicago/Turabian StyleJ.W.J. Kaiser; S. Adami; I.S. Akhatov; N.A. Adams. 2020. "A semi-implicit conservative sharp-interface method for liquid-solid phase transition." International Journal of Heat and Mass Transfer 155, no. : 119800.
A graphene nanobubble consists of a graphene sheet, an atomically flat substrate, and a substance enclosed between them. Unlike conventional confinement with rigid walls and a fixed volume, the graphene nanobubble has one stretchable wall, which is the graphene sheet, and its volume can be adjusted by changing the shape. In this study, we developed a model of a graphene nanobubble based on classical density functional theory and the elastic theory of membranes. The proposed model takes into account the inhomogeneity of the enclosed substance, the nonrigidity of the wall, and the alternating volume. As an example application, we utilize the developed model to investigate fluid argon inside graphene nanobubbles at room temperature. We observed a constant height-to-radius ratio over the whole range of radii considered, which is in agreement with the results from experiments and molecular dynamics simulations. The developed model provides a theoretical tool to study both the inner structure of the confined substance and the shape of the graphene nanobubble. The model can be easily extended to other types of nonrigid confinement.A graphene nanobubble consists of a graphene sheet, an atomically flat substrate, and a substance enclosed between them. Unlike conventional confinement with rigid walls and a fixed volume, the graphene nanobubble has one stretchable wall, which is the graphene sheet, and its volume can be adjusted by changing the shape. In this study, we developed a model of a graphene nanobubble based on classical density functional theory and the elastic theory of membranes. The proposed model takes into account the inhomogeneity of the enclosed substance, the nonrigidity of the wall, and the alternating volume. As an example application, we utilize the developed model to investigate fluid argon inside graphene nanobubbles at room temperature. We observed a constant height-to-radius ratio over the whole range of radii considered, which is in agreement with the results from experiments and molecular dynamics simulations. The developed model provides a theoretical tool to study both the inner structure of the confined su...
T. F. Aslyamov; E. S. Iakovlev; I. Sh. Akhatov; P. A. Zhilyaev. Model of graphene nanobubble: Combining classical density functional and elasticity theories. The Journal of Chemical Physics 2020, 152, 054705 .
AMA StyleT. F. Aslyamov, E. S. Iakovlev, I. Sh. Akhatov, P. A. Zhilyaev. Model of graphene nanobubble: Combining classical density functional and elasticity theories. The Journal of Chemical Physics. 2020; 152 (5):054705.
Chicago/Turabian StyleT. F. Aslyamov; E. S. Iakovlev; I. Sh. Akhatov; P. A. Zhilyaev. 2020. "Model of graphene nanobubble: Combining classical density functional and elasticity theories." The Journal of Chemical Physics 152, no. 5: 054705.
Low-permeable materials, either artificial or natural, are essential components of the current technological development. Their production or processing requires a comprehensive characterization method based on confident reference standards. Permeability standards for values below 10−15 m2 are lacking. In this study, we explored the feasibility of using the ceramic sintering process to reach low, but measurable values of gas permeability in Al2O3 samples, as one of the potential materials for reference standards. The studied samples were produced with a ceramic 3D printer, which enables the manufacturing of low-permeable samples having complex geometrical arrangements. A series of preliminary laboratory testing indicated the available gas permeability range from 2.4 × 10−15 m2 for the pre-sintered samples to 1.8 × 10−21 m2 for the sintered samples. The verification of the permeability reduction was carried out using a unique unsteady state fast and accurate measurement method. The results confirm the possibility of developing a technology for materials manufacturing with low porosity and permeability. Such materials open many areas for application, including manufacturing of ceramics with controlled transport properties and low-permeability standards for calibrating laboratory equipment for geosciences, construction industries, biomedical, and other relevant fields.
Svyatoslav Chugunov; Andrey Kazak; Mohammed Amro; Carsten Freese; Iskander Akhatov. Towards Creation of Ceramic-Based Low Permeability Reference Standards. Materials 2019, 12, 3886 .
AMA StyleSvyatoslav Chugunov, Andrey Kazak, Mohammed Amro, Carsten Freese, Iskander Akhatov. Towards Creation of Ceramic-Based Low Permeability Reference Standards. Materials. 2019; 12 (23):3886.
Chicago/Turabian StyleSvyatoslav Chugunov; Andrey Kazak; Mohammed Amro; Carsten Freese; Iskander Akhatov. 2019. "Towards Creation of Ceramic-Based Low Permeability Reference Standards." Materials 12, no. 23: 3886.
Developing bone scaffolds can greatly improve the patient’s quality of life by accelerating the rehabilitation process. In this paper, we studied the process of composite polycaprolactone supercritical foaming for tissue engineering. The influence of graphene oxide and reduced graphene oxide on the foaming parameters was studied. The structural and mechanical properties were studied. The scaffolds demonstrated mechanical flexibility and endurance. The co-culturing and live/dead tests demonstrated that the obtained scaffolds are biocompatible. Different composite scaffolds induced various surface cell behaviors. The experimental data demonstrate that composite foams are promising candidates for in vivo medical trials.
Stanislav Evlashin; Pavel Dyakonov; Mikhail Tarkhov; Sarkis Dagesian; Sergey Rodionov; Anastasia Shpichka; Mikhail Kostenko; Stepan Konev; Ivan Sergeichev; Petr Timashev; Iskander Akhatov. Flexible Polycaprolactone and Polycaprolactone/Graphene Scaffolds for Tissue Engineering. Materials 2019, 12, 2991 .
AMA StyleStanislav Evlashin, Pavel Dyakonov, Mikhail Tarkhov, Sarkis Dagesian, Sergey Rodionov, Anastasia Shpichka, Mikhail Kostenko, Stepan Konev, Ivan Sergeichev, Petr Timashev, Iskander Akhatov. Flexible Polycaprolactone and Polycaprolactone/Graphene Scaffolds for Tissue Engineering. Materials. 2019; 12 (18):2991.
Chicago/Turabian StyleStanislav Evlashin; Pavel Dyakonov; Mikhail Tarkhov; Sarkis Dagesian; Sergey Rodionov; Anastasia Shpichka; Mikhail Kostenko; Stepan Konev; Ivan Sergeichev; Petr Timashev; Iskander Akhatov. 2019. "Flexible Polycaprolactone and Polycaprolactone/Graphene Scaffolds for Tissue Engineering." Materials 12, no. 18: 2991.
A liquid–gas phase transition of ethane inside graphene nanobubbles below the critical temperature leads to a ‘forbidden range’ of radii, in which no stable bubbles exist.
Evgeny Iakovlev; Petr Zhilyaev; Iskander S. Akhatov. Modeling of the phase transition inside graphene nanobubbles filled with ethane. Physical Chemistry Chemical Physics 2019, 21, 18099 -18104.
AMA StyleEvgeny Iakovlev, Petr Zhilyaev, Iskander S. Akhatov. Modeling of the phase transition inside graphene nanobubbles filled with ethane. Physical Chemistry Chemical Physics. 2019; 21 (33):18099-18104.
Chicago/Turabian StyleEvgeny Iakovlev; Petr Zhilyaev; Iskander S. Akhatov. 2019. "Modeling of the phase transition inside graphene nanobubbles filled with ethane." Physical Chemistry Chemical Physics 21, no. 33: 18099-18104.
Composite materials play an important role in aircraft, space and automotive industries, wind power industry. One of the most commonly used methods for the manufacture of composite materials is the impregnation of dry textiles by a viscous liquid binder. During the process, cavities (voids) of various sizes can be formed and then move in a liquid resin flows in the complex system of channels formed by textile fibers. The presence of such cavities results in a substantial deterioration of the mechanical properties of the composites. As a result, the development and effective implementation of the numerical methods and approaches for the effective 3D simulation of the viscous liquid flow around a rigid structure of different configuration. In the present study, the mathematical model and its effective numerical implementation for the study of hydrodynamic processes around fixed structure at low Reynolds numbers is considered. The developed approach is based on the boundary element method for 3D problems accelerated both via an advanced scalable algorithm (FMM), and via utilization of a heterogeneous computing architecture (multicore CPUs and graphics processors). This enables direct large scale simulations on a personal workstation, which is confirmed by test and demo computations. The simulation results and details of the method and accuracy/performance of the algorithm are discussed. The results of the research may be used for the solution of problems related to microfluidic device construction, theory of the composite materials production, and are of interest for computational hydrodynamics as a whole.
Olga A. Abramova; Yulia A. Pityuk; Nail A. Gumerov; Iskander Sh. Akhatov. Three-Dimensional Simulation of Stokes Flow Around a Rigid Structure Using FMM/GPU Accelerated BEM. Programmieren für Ingenieure und Naturwissenschaftler 2018, 427 -438.
AMA StyleOlga A. Abramova, Yulia A. Pityuk, Nail A. Gumerov, Iskander Sh. Akhatov. Three-Dimensional Simulation of Stokes Flow Around a Rigid Structure Using FMM/GPU Accelerated BEM. Programmieren für Ingenieure und Naturwissenschaftler. 2018; ():427-438.
Chicago/Turabian StyleOlga A. Abramova; Yulia A. Pityuk; Nail A. Gumerov; Iskander Sh. Akhatov. 2018. "Three-Dimensional Simulation of Stokes Flow Around a Rigid Structure Using FMM/GPU Accelerated BEM." Programmieren für Ingenieure und Naturwissenschaftler , no. : 427-438.
The compliance contribution of a penny-shaped crack having multiple contacts between crack faces is analyzed. In order to reduce the number of parameters involved, regular lattices of circular contacts are considered. It is found, in particular, that, at the same total area of contacts, a large number of small contacts produces stronger stiffening effect than a small number of large contacts; hence the total contact area is not the parameter controlling the crack compliance contribution. The effects of contacts on both the normal and the shear crack compliances are found to be very close. In the case of moderately non-regular contact lattices, the results were found to be only marginally different from the results for regular ones. Results are conveniently expressed in terms of “Holm's radius” – the radius of a single contact that would have produced the same effect. Being applied to multiple cracks with contacts, our results yield the “adjusted”, for the presence of contacts, value of crack density.
A. Markov; S. Abaimov; I. Sevostianov; M. Kachanov; S. Kanaun; Iskander Akhatov. The effect of multiple contacts between crack faces on crack contribution to the effective elastic properties. International Journal of Solids and Structures 2018, 163, 75 -86.
AMA StyleA. Markov, S. Abaimov, I. Sevostianov, M. Kachanov, S. Kanaun, Iskander Akhatov. The effect of multiple contacts between crack faces on crack contribution to the effective elastic properties. International Journal of Solids and Structures. 2018; 163 ():75-86.
Chicago/Turabian StyleA. Markov; S. Abaimov; I. Sevostianov; M. Kachanov; S. Kanaun; Iskander Akhatov. 2018. "The effect of multiple contacts between crack faces on crack contribution to the effective elastic properties." International Journal of Solids and Structures 163, no. : 75-86.