Papers by Keyword: Anisotropy

Abstract: The research presented in this scientific paper focuses on modeling the dynamics of multicomponent systems with particles of different geometries using the GROMACS software package. Three main types of particles were analyzed in the study: spheres, ellipsoids, and plates, each of which has its own unique geometric characteristics that affect their behavior in the environment. The modeling allowed us to investigate the influence of particle shape on their diffusion, self-organization, and interaction between particles of different shapes. In particular, spherical particles, having an isotropic geometry, show the highest diffusion coefficient, since their symmetrical structure minimizes the resistance of the environment. This, in turn, makes them ideal for modeling simple interactions in liquids or colloids. Ellipsoidal particles, due to their anisotropy, have a slightly reduced diffusion coefficient, since their orientation in space affects the motion. Plates, which have a significant surface area relative to the volume, demonstrate the lowest diffusion rate, which is associated with a large interaction with the environment and the resistance created by their geometry. The results of the study also showed that the diffusion coefficient decreases with increasing particle size for all types. At the same time, spheres demonstrated the highest diffusion coefficient at the same size compared to other geometries, while plates have the lowest values ​​of this indicator. Analysis of the trajectories of particle motion in space using the GROMACS software allowed us to assess the influence of geometry on particle mobility. It was found that spheres exhibit the largest displacement amplitude, which indicates their high mobility and chaotic nature of the motion. Ellipsoids have a more stable motion with smaller displacements, which is associated with their geometric anisotropy. Plates, due to the large resistance of the environment, have the smallest displacements, which indicates limited mobility. It should be noted that the obtained research results open up opportunities for a deeper understanding of interactions in complex multicomponent systems and can be useful for further research in various fields. It is also worth noting that the comparison of different types of particles with different geometries and their influence on diffusion processes allowed us to obtain valuable information for improving models and practical applications in relevant fields of science and technology.

Abstract: The article presents a calculation method developed for assessing the strength characteristics of building structures constructed using 3D printing technology. The method takes into account the physical and mechanical properties of the material, including modulus of deformation, creep, and compressive strength. A comparative analysis between traditional brick masonry and 3D-printed sand concrete walls of the M300 grade demonstrated the higher load-bearing capacity of additive structures. The study also identifies the limitations of the proposed method when applied to wall fragments with complex geometries and highlights the lack of specialized standards in Ukraine. Particular attention is drawn to the need for adapting regulatory documents to account for the anisotropy of the material and the 10–30 % reduction in interlayer strength. Overall, the results confirm the promising potential of 3D printing for the rapid reconstruction of buildings and emphasize the importance of ensuring the safety and durability of such structures.

Abstract: Leather is a fiber-reinforced material with a more concentrated fiber distribution in three dimensions perpendicular to the tangential plane than in-plane. The asymmetric dispersion of fibers can have a significant effect on the mechanical properties of natural leather. The transverse isotropic constitutive model is unable to accurately describe the anisotropy of natural leather. Accordingly, we have devised a novel anisotropic theoretical framework that incorporates asymmetric fiber dispersion, with the objective of accurately characterizing the mechanical behavior of anisotropy with asymmetric fiber distribution. Our approach entails the incorporation of the Yeoh model into the theoretical framework, as well as the introduction of a specific anisotropy term within the strain energy function, with the objective of describing the nonlinear properties. By fitting the theoretical results of the model to tensile test data of natural leather specimens, the structural and material parameters were determined. We provided specific stress tensors to enable finite element analysis. Our finite element analysis investigates the effect of asymmetric fiber dispersion on the mechanical response under uniaxial and biaxial stretching. By simulating the tensile behavior of natural leather specimens under different tensile angles, we observe a non-homogeneous stress distribution and non-homogeneous deformation due to fiber families under fixed stretching. This theoretical framework based on a continuum model provides a theoretical reference for describing the mechanical properties of leather materials with asymmetric fiber dispersion.

Abstract: Rolled titanium alloy has been widely applied to components in aerospace industry. The cutting force and the quality of hole are studied in drilling of countersunk hole of rolled titanium alloy with the crystallographic anisotropy. The periodical changes in the cutting force were observed in drilling of rolled titanium alloy, whereas in drilling of carbon steel, the cutting force increases without periodical changes due to isotropic material. The cutting force depends on the cutting direction angle, defined as the relative angle of the cutting direction with respect to the workpiece coordinate system. When the cutting direction is parallel to the rolling direction, the cutting direction angle is denoted as 0°, and when it is perpendicular, the cutting direction angle is denoted as 90°. The cutting force becomes stable around a cutting direction angle of 0°, while high frequency vibrations are observed in the cutting force around a cutting direction angle of 90°. The countersunk angle and the surface finish depend on the cutting direction angle. The cutting forces, then, are analyzed using an analytical force simulation. A three-dimensional chip flow is interpreted as a piling up of orthogonal cuttings containing cutting velocities and chip flow velocities. The cutting force is predicted by the determined chip flow model, where the chip flow direction is determined to minimize the cutting energy. The changes in the shear plane cutting model of rolled titanium alloy are discussed in the simulation. These findings provide better understandings of the effect of anisotropy in drilling to improve the quality of countersunk holes.

Abstract: The article presents the results of experimental studies of the effect of material anisotropy and the presence of tunnel inhomogeneity of 3D-printed elements relative to the direction of compression on the mechanical and strength characteristics of the obtained samples. Test samples made by 3D printing using PETG plastic were used for the research. Research was performed for solid samples and samples with a system of free and reinforced cavities. The results of experimental studies allow us to study the influence of the presence of geometric and structural heterogeneity of bodies on their mechanical and strength characteristics during their 3D printing. Thepeformed studies allow to optimally choose the modes of 3D printing of elements taking into account the anisotropy of the material in order to ensure their maximum strength characteristics. The results of experimental studies confirm the results of numerical calculations [1] obtained on the basis of the finite element method.

Abstract: Electron mobility along the c-axis is the most important in SiC because the current flows along this direction in vertical SiC devices. However, previous reports on the drift mobility along the c-axis are still limited because of the difficulty of sample preparation or analysis. In this study, the authors presented the method to estimate the electron drift mobility of a lightly-doped epitaxial layer by using SiC(0001) vertical Schottky barrier diodes (SBDs). For the analyses, the effects of current spreading and series resistance were carefully considered based on experimental results obtained from SBDs with various device parameters, leading to a more accurate estimation. The mobility along the c-axis was obtained as 1070 ± 290 cm²/Vs for a donor density of 1 × 10¹⁵ cm^-3, and it was compared with the results by Hall effect measurement.

Abstract: Fibre-reinforced polymer (FRP) composites have many desirable properties such as high corrosion resistance and a high strength-to-weight ratio. They can also be easily optimised to suit different loading requirements. To produce functional components through 3D printing using FRPs, it is important to optimize the printing process parameters and to predict the mechanical properties of the printed components. The mathematical predictive approach is preferred over experiments it is flexible, fast and not as costly as experiments. In this work, a coupled finite element model for predicting flexural strength properties of additively manufactured parts is developed. The model takes into account the structure, material microstructure, and fused filament fabrication (FFF) process parameters in predicting the flexural strength of parts. The validity of the model is tested using a standard flexural bending specimen and an ankle-foot orthosis (AFO) prototype which are fabricated using short carbon fibre-reinforced polyamide 12 (PA12-CF) filament. The validity of the coupled analysis model was tested by comparing the model predictions of flexural strength with experimental results. The results provide a good prediction of part performance.

Abstract: The oil and gas sector faces challenges in optimizing oil recovery from reservoirs due to trapped oil due to interfacial tension and surface forces. Characterizing anisotropic dielectric properties is crucial. The petroleum business is quickly changing, and a massive advancement in the application of nanotechnology in this field is envisaged. Because magnetic nanoparticles (MNP) are solid, tiny, and adsorb at the oil-water interface, they might be helpful. The interaction of MNP with electromagnetic waves appears to be capable of altering interfacial tension, which will boost oil recovery. The interaction of an oscillating B-field of electromagnetic waves with magnetic domains causes energy dissipation due to a shift in magnetic anisotropy from the easy axis of magnetization. The use of anisotropy energy in mobilizing oil in a porous media has recently been investigated. BaTiO₃ nanoparticles (NPs) were synthesized for this purpose, and their influence on oil mobility under electromagnetic waves (EM) was studied. The anisotropy energy was computed and determined to be 7.34kJ/mol. Under EM, the easy axis magnetization of BaTiO₃ nanoparticles oscillates and changes direction continually, facilitating oil mobilization in the porous media. The EM findings for reducing interfacial tension (IFT) between oil and water ranged from 4.5mN/m to 0.89mN/m. Under EM, it was discovered that BaTiO₃ nanoparticles might lower IFT by roughly 60%. The IFT must be small enough to allow oil flow during mobilization. The simulation findings demonstrate that the adsorption energy of n-hexane on the surface of hematite has a 47.9% lower energy value than water. With a 115.4% percentage difference, the stress autocorrelation function of n-hexane with hematite is greater than that of water.

Abstract: Anisotropy in tensile behaviour, plastic flow behaviour, and low cycle fatigue (LCF) behaviour of additively manufactured (AM) maraging steel in different build orientations are presented and compared with conventionally manufactured maraging steel. Also, the effect of heat treatment (namely, solution treatment and ageing) on tensile behaviour and low-cycle fatigue behaviour were studied. The AM maraging steel showed more anisotropy in as-built (AB) condition and moderate anisotropy in heat-treated (HT) condition. Experimental engineering stress-engineering strain and true stress-true strain data of AB AM maraging steel and HT conditions have been analysed using Hollomon, Ludwik, Swift, Ludwigson, and Voce plastic flow relationships. It is also observed that the 0° oriented specimen exhibits better tensile and LCF behaviour as compared to the 90° oriented specimen in AB and HT conditions.

Abstract: Aluminium 8011 cast plates subjected to cold rolling to reduce thickness from 12 mm to 3.5 sheets. As rolled aluminium sheet was subjected to annealing treatment after rolling. This work deals with the study of planar and normal anisotropy parameters of as rolled aluminium and rolled with annealed aluminium sheets. The tensile test samples were cut at 0°, 30°, 45°, 60° and 90° with respect to the rolling direction of as rolled Al sheet and rolled with annealed Al sheet. Tensile properties were measured at different orientations to the rolling directions. The wide variation in tensile strength was found in case of as rolled Al samples at different orientation to rolling direction of sheet (208 to 243 MPa). On the other hand nearly uniform tensile strength (128 MPa to 132 MPa) was measured for rolled and annealed Al samples at different orientations. As rolled Al samples shows anisotropic tensile properties where as isotropic tensile properties were measured for rolled with annealed Al samples. Al grains are more elongated along the rolling directions where as rolled and annealed Al sample shows more equiaxed grains which is attributed to isotropic behaviour of Al sheets. The normal anisotropy parameter or average r_m value is higher (1.24) in case of rolled and annealed sheet sample as compared to as rolled Al sheet r_m value (1.06). This is attributed to isotropic behaviour of rolled and annealed samples. Toughness and ductility properties are improved more than 3 times in case of rolled and annealed Al sheet samples. Annealing treatment of rolled Al sheet samples shows elongated grain morphology changes to equiaxed grains of aluminum which tends to improved formability and isotropic mechanical properties Al sheet. For determination of normal anisotropy (r_m) value, tensile results R values are required at angles of 0 degrees, 45 degrees, and 90 degrees. However in this study additional R values are estimated at 30 degree and 60 degree in order to understand trend of R value at every 30 degree from 0 to 90 degree.