Papers by Keyword: Computer Simulation

Abstract: This scientific work presents the development of a computer-simulation model for particle filling in three-dimensional space based on molecular dynamics methods. The Lennard-Jones potential was used to simulate interactions between particles, and the equations of motion were integrated using the Velocity Verlet algorithm. The model incorporates periodic boundary conditions (PBC), ensuring accurate representation of an infinite system without boundary effects. The simulation results confirm the system's energy stability: the total energy remains virtually unchanged throughout the simulation, indicating the correctness of numerical integration. Fluctuations in kinetic and potential energies demonstrate normal system dynamics, where energy is redistributed among particles through interactions. An analysis of the spatial distribution of particles revealed that the system remains in a liquid state, with no signs of solid structure formation or particle aggregation. Notably, the developed model enables the simulation of complex physical processes such as dense structure formation, particle transport, and self-packing. The obtained results highlight the efficiency of the molecular dynamics method for analyzing granular and particulate media, as well as for studying the physical properties of multi-particle systems. The model can be utilized to optimize technological processes related to material transportation, packaging, and storage, as well as for research into nanomaterials and composites.

Abstract: The trajectories of particles scattered on ideal surfaces of CdTe (001) < 110> have been calculated. The characteristic trajectories was received for Ar⁺ ions by initial energy 1 keV and at the angles of bombardment y=3⁰ and 7⁰. This trajectories studied by using semichannel model. It was shown that the trajectories of scattered ions from the surface atomic row, from the wall of the semichannel and from the bottom of the semichannel differ from each other. The first trajectories of scattered ions from a surface semichannel consisting of five Cd and Te atoms arranged layer-by-layer in two layers were obtained. The shapes of these three types of trajectories are discussed and the energies, scattering coefficients, and inelastic energy losses of the scattered ions are calculated. It is shown that the energy values, scattering coefficient and inelastic energy losses of scattered ions from surface atomic rows differ little from each other. For ions scattered from the wall of the semichannel and from the bottom of the semichannel, the values of these parameters lie in the range.

Abstract: The change in hardness due to 475°C embrittlement was investigated in the melt-run GTA welds of type 329J4L duplex stainless steel. A ferritic phase was hardened with ageing at 673-773K due to the phase decomposition into Fe-rich and Cr-rich phases, while an austenitic phase was barely hardened with ageing. Hardness in a ferritic phase was rapidly increased with ageing in the base metal (BM) region, and the hardening rate was reduced in the order of BM, weld metal (WM) and heat affected zone (HAZ). The ferrite/austenite fractions in HAZ and WM were higher than that in BM, furthermore, Cr content in a ferritic phase was lowered and Ni content in it was contrarily heightened in the same order of BM, WM and HAZ. A computed phase diagram suggested that the chemical composition of a ferritic phase in each region was located in the nucleation/growth region not spinodal decomposition region, which was situated between the spinodal and binodal lines. Computer simulation of phase decomposition phenomena in a ferritic phase using phase field model revealed that phase decomposition was accelerated with an increase in Cr content and a decrease in Ni content. It followed that Cr would enhance the 475°C embrittlement and Ni would inhibit it, because of the increased/decreased driving force of the phase decomposition. The difference in 475°C embrittlement behaviour at each region could be attributed to the difference in the chemical composition of a ferritic phase caused by the ferrite/austenite phase transformation during welding.

Abstract: Today, one of the problems of modern implants is their high rigidity, which can lead to bone resorption at the interface between the implant and the bone and to the gradual detachment of the implant. In addition, implant detachment can occur due to the positive Poisson's ratio of the implant along its entire length. This phenomenon is described in detail in [1]. As a possible solution to these problems, it is proposed to use lattice structures with negative Poisson's ratio from TiNi alloy. This alloy has a fairly low modulus of elasticity - about 48 GPa. The use of a porous (lattice) structure of an implant made of TiNi alloy will reduce the modulus of elasticity and bring it closer to the modulus of human cortical bone – 12-17 GPa [2], and possibly the modulus of elasticity of cancellous bone – 0.1-5 GPа [3]. In this work, a computer numerical simulation of strut based lattice structures with several variants of unit cell topology with a negative Poisson's ratio is carried out. For the obtained structures, the following characteristics were calculated - elastic modulus (Young's modulus), modulus of elasticity in shear, Poisson's ratio. The modeling process is implemented using the ANSYS 2019 R2 SpaceClaim finite element analysis package. The data obtained confirmed the promising possibility of modeling and fabricating lattice structures with a low elastic modulus and negative Poisson's ratio from a TiNi alloy. Also, on the basis of this data, conclusions about the influence of the topology and porosity of unit cells on the resulting characteristics of the lattice structure were made.

Abstract: This paper describes QForm computer simulation of a large-sized blade preform shaping, using cross-wedge rolling. Scenarios of friction consideration between the workpiece and the tool are examined.

Abstract: The analysis of existing processing methods was carried out. A series of virtual experiments was performed; based on their results dependences of the height of residual ridges, the temperature on the workpiece surface and the temperature in the cutting zone on the parameters of the processing mode when boring internal holes with a rotating cutter block were constructed based on the results of virtual computer simulation. An optimization model of the boring process was built. The objective function was received. Within the optimization model framework, solutions were obtained that allow, at the highest value of axial feed, to ensure the required surface quality and avoid changes in the physical and mechanical properties of the material.

Abstract: This article presents the results of computer modeling of small-angle scattering of Ar+ ions from the surface of the SiO₂ thin film under bombardment by low-energy. The study of the trajectory of the scattered ions showed that the trajectories with two focuses are observed not only near the center of the semichannel but also nearby the surface of the atomic chain. An increase in the value of the initial energy of incident particles leads to a narrowing of the trajectory of the scattered ions, which leads to the appearance of low-intensity peaks in the energy spectrum of the scattered ions.

Abstract: In this paper presents the computer simulation results on the investigations of the ion scattering processe on the defect InP(001)<110>,<ī10> surface under low-energy grazing ion bombardment have been presented. The peculiarities trajectories of the scattered ions from surface defect, atomic chain and semichannel have been investigated by computer simulation. It was found some trajectories nearby surface atomic chain which have loop shape and a line form. At grazing ion incidence, from a correlation of the experimental and calculated energy distributions of the scattered particles, one may determine a spatial extension of the missing atom on the monocrystal surface damaged by the ion bombardment.

Abstract: One of the effective ways to improve the quality of semi-finished products made from aluminum alloys is to eliminate the columnar and fan-shaped structure in them, refine the grain and achieve homogeneity, is modification and alloying. Modification of the melt is carried out using ligatures and allows a significant increase in the casting rate without fear of an excessive increase in the degree of zonal segregation during crystallization, as well as ensuring the uniformity of the chemical composition over the section. An important role in the quality of modification is also played by the manufacturing technology of the master alloy itself, which should ensure an increase in the cooling rate during crystallization. To obtain an alloy with the required properties, the quality of the charge materials used must be considered. First of all, this concerns master alloys, which are used for alloying and modifying the alloy. The most common for the manufacture of ingots and shaped castings are master alloys containing boron or boron and titanium. The boron content in these ligatures is 1-5%. It is generally accepted that a large amount of boron (except for the rise in the cost of the alloy itself) upon accelerated cooling promotes the refinement of the internal structure of the grain, but can lead to an increase in large inclusions of TiB2.

Abstract: A promising direction for the development of steel and alloy processing processes is the intensification of plastic deformation by creating zones of localization of shear strains not only in the longitudinal but also in the transverse directions of the deformed metal flow. Intensification of alternating deformations along the entire cross-section and, especially, in the axial zone of the billet by creating new deformation schemes is an effective way to increase the physical, mechanical and functional properties of the metal with the maximum approximation of the finished product size to the original billet size. The paper shows that a promising idea is the development of new technological schemes that implement severe alternating deformation in existing metal forming processes. A continuous rolling method of wide strips is proposed, which provides severe alternating deformation with minor changes in the size of the billet. Based on this method, a scheme of continuous rolling of the strip with the intensification of plastic deformation of the metal is designed. The results of computer simulation showed that the new rolling method increases the strain uniformity in height and the value of the strain degree in the plane of symmetry of the billet.