Research

13 pages, 14681 KiB

Open AccessArticle

A Computational Study of Solid Si Target Dynamics under ns Pulsed Laser Irradiation from Elastic to Melting Regime

by Helen Papadaki, Evaggelos Kaselouris, Makis Bakarezos, Michael Tatarakis, Nektarios A. Papadogiannis and Vasilis Dimitriou

Computation 2023, 11(12), 240; https://doi.org/10.3390/computation11120240 - 03 Dec 2023

Viewed by 1218

Abstract

The dynamic behavior of solid Si targets irradiated by nanosecond laser pulses is computationally studied with transient, thermοmechanical three-dimensional finite element method simulations. The dynamic phase changes of the target and the generation and propagation of surface acoustic waves around the laser focal [...] Read more.

The dynamic behavior of solid Si targets irradiated by nanosecond laser pulses is computationally studied with transient, thermοmechanical three-dimensional finite element method simulations. The dynamic phase changes of the target and the generation and propagation of surface acoustic waves around the laser focal spot are provided by a finite element model of a very fine uniformly structured mesh, able to provide high-resolution results in short and long spatiotemporal scales. The dynamic changes in the Si material properties until the melting regime are considered, and the simulation results provide a detailed description of the irradiated area response, accompanied by the dynamics of the generation and propagation of ultrasonic waves. The new findings indicate that, due to the low thermal expansion coefficient and the high penetration depth of Si, the amplitude of the generated SAW is small, and the time and distance needed for the ultrasound to be generated is higher compared to dense metals. Additionally, in the melting regime, the development of high nonlinear thermal stresses leads to the generation and formation of an irregular ultrasound. Understanding the interaction between nanosecond lasers and Si is pivotal for advancing a wide range of technologies related to material processing and characterization. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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12 pages, 777 KiB

Open AccessArticle

Buckling Assessment in the Dynamics Mechanisms, Stewart Platform Case Study: In the Context of Loads and Joints, Deflection Positions Gradient

by Reza Hassanian and Morris Riedel

Computation 2023, 11(11), 227; https://doi.org/10.3390/computation11110227 - 15 Nov 2023

Viewed by 1494

Abstract

This study introduces an approach for modeling an arm of a Stewart platform to analyze the location of sections with a high deflection among the arms. Given the dynamic nature of the Stewart platform, its arms experience static and dynamic loads. The static [...] Read more.

This study introduces an approach for modeling an arm of a Stewart platform to analyze the location of sections with a high deflection among the arms. Given the dynamic nature of the Stewart platform, its arms experience static and dynamic loads. The static loads originate from the platform’s own weight components, while the dynamic loads arise from the movement or holding of equipment in a specific position using the end-effector. These loads are distributed among the platform arms. The arm encompasses various design categories, including spring-mass, spring-mass-damper, mass-actuator, and spring-mass-actuator. In accordance with these designs, joint points should be strategically placed away from critical sections where maximum buckling or deformation is prominent. The current study presents a novel model employing Euler’s formula, a fundamental concept in buckling analysis, to propose this approach. The results align with experimental and numerical reports in the literature that prove the internal force of the platform arm is affecting the arm stiffness. The equal stiffness of an arm is related to its internal force and its deflection. The study demonstrates how higher levels of dynamic loading influence the dynamic platform, causing variations in the maximum arm’s buckling deflection, its precise location, and the associated deflection slope. Notably, in platform arms capable of adjusting their tilt angles relative to the vertical axis, the angle of inclination directly correlates with deflection and its gradient. The assumption of linearity in Euler’s formula seems to reveal distinctive behavior in deflection gradients concerning dynamic mechanisms. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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36 pages, 9223 KiB

Open AccessArticle

A General Procedure to Formulate 3D Elements for Finite Element Applications

by Adnan Shahriar, Arsalan Majlesi and Arturo Montoya

Computation 2023, 11(10), 197; https://doi.org/10.3390/computation11100197 - 03 Oct 2023

Cited by 2 | Viewed by 2282

Abstract

This paper presents a general procedure to formulate and implement 3D elements of arbitrary order in meshes with multiple element types. This procedure includes obtaining shape functions and integration quadrature and establishing an approach for checking the generated element’s compatibility with adjacent elements’ [...] Read more.

This paper presents a general procedure to formulate and implement 3D elements of arbitrary order in meshes with multiple element types. This procedure includes obtaining shape functions and integration quadrature and establishing an approach for checking the generated element’s compatibility with adjacent elements’ surfaces. This procedure was implemented in Matlab, using its symbolic and graphics toolbox, and complied as a GUI interface named ShapeGen3D to provide finite element users with a tool to tailor elements according to their analysis needs. ShapeGen3D also outputs files with the element formulation needed to enable users to implement the generated elements in other programming languages or through user elements in commercial finite element software. Currently, finite element (FE) users are limited to employing element formulation available in the literature, commercial software, or existing element libraries. Thus, the developed procedure implemented in ShapeGen3D offers FEM users the possibility to employ elements beyond those readily available. The procedure was tested by generating the formulation for a brick element, a brick transition element, and higher-order hexahedron and tetrahedron elements that can be used in a spectral finite element analysis. The formulation obtained for the 20-node element was in perfect agreement with the formulation available in the literature. In addition, the results showed that the interpolation condition was met for all the generated elements, which provides confidence in the implementation of the process. Researchers and educators can use this procedure to efficiently develop and illustrate three-dimensional elements. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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18 pages, 5526 KiB

Open AccessArticle

Computational Fracture Modeling for Effects of Healed Crack Length and Interfacial Cohesive Properties in Self-Healing Concrete Using XFEM and Cohesive Surface Technique

by John Hanna and Ahmed Elamin

Computation 2023, 11(7), 142; https://doi.org/10.3390/computation11070142 - 16 Jul 2023

Cited by 1 | Viewed by 941

Abstract

Healing patterns are a critical issue that influence the fracture mechanism of self-healing concrete (SHC) structures. Partial healing cracks could happen even during the normal operating conditions of the structure, such as sustainable applied loads or quick crack spreading. In this paper, the [...] Read more.

Healing patterns are a critical issue that influence the fracture mechanism of self-healing concrete (SHC) structures. Partial healing cracks could happen even during the normal operating conditions of the structure, such as sustainable applied loads or quick crack spreading. In this paper, the effects of two main factors that control healing patterns, the healed crack length and the interfacial cohesive properties between the solidified healing agent and the cracked surfaces on the load carrying capacity and the fracture mechanism of healed SHC samples, are computationally investigated. The proposed computational modeling framework is based on the extended finite element method (XFEM) and cohesive surface (CS) technique to model the fracture and debonding mechanism of 2D healed SHC samples under a uniaxial tensile test. The interfacial cohesive properties and the healed crack length have significant effects on the load carrying capacity, the crack initiation, the propagation, and the debonding potential of the solidified healing agent from the concrete matrix. The higher their values, the higher the load carrying capacity. The solidified healing agent will be debonded from the concrete matrix when the interfacial cohesive properties are less than 25% of the fracture properties of the solidified healing agent. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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22 pages, 8005 KiB

Open AccessArticle

A FEM Structural Analysis of a Francis Turbine Blade Parametrized Using Piecewise Bernstein Polynomials

by Heriberto Arias-Rojas, Miguel A. Rodríguez-Velázquez, Ángel Cerriteño-Sánchez, Francisco J. Domínguez-Mota and Sergio R. Galván-González

Computation 2023, 11(7), 123; https://doi.org/10.3390/computation11070123 - 26 Jun 2023

Cited by 1 | Viewed by 1145

Abstract

Several methodologies have successfully described the runner blade shape as a set of discrete sections joining the hub and shroud, defined by 3D geometrical forms of considerable complexity. This task requires an appropriate parametric approach for its accurate reconstruction. Among them, piecewise Bernstein [...] Read more.

Several methodologies have successfully described the runner blade shape as a set of discrete sections joining the hub and shroud, defined by 3D geometrical forms of considerable complexity. This task requires an appropriate parametric approach for its accurate reconstruction. Among them, piecewise Bernstein polynomials have been used to create parametrizations of twisted runner blades by extracting some cross-sectional hydrofoil profiles from reference CAD data to be approximated by such polynomials. Using the interpolating polynomial coefficients as parameters, more profiles are generated by Lagrangian techniques. The generated profiles are then stacked along the spanwise direction of the blade via transfinite interpolation to obtain a smooth and continuous representation of the reference blade. This versatile approach makes the description of a range of different blade shapes possible within the required accuracy and, furthermore, the design of new blade shapes. However, even though it is possible to redefine new blade shapes using the aforementioned parametrization, a remaining question is whether the parametrized blades are suitable as a replacement for the currently used ones. In order to assess the mechanical feasibility of the new shapes, several stages of analysis are required. In this paper, bearing in mind the standard hydraulic test conditions of the hydrofoil test case of the Norwegian Hydropower Center, we present a structural stress–strain analysis of the reparametrization of a Francis blade, thus showing its adequate computational performance in two model tests. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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14 pages, 1372 KiB

Open AccessArticle

A Novel Finite Element Model for the Study of Harmful Vibrations on the Aging Spine

by Shivam Verma, Gurpreet Singh and Arnab Chanda

Computation 2023, 11(5), 93; https://doi.org/10.3390/computation11050093 - 05 May 2023

Cited by 1 | Viewed by 1124

Abstract

The human spine is susceptible to a wide variety of adverse consequences from vibrations, including lower back discomfort. These effects are often seen in the drivers of vehicles, earth-moving equipment, and trucks, and also in those who drive for long hours in general. [...] Read more.

The human spine is susceptible to a wide variety of adverse consequences from vibrations, including lower back discomfort. These effects are often seen in the drivers of vehicles, earth-moving equipment, and trucks, and also in those who drive for long hours in general. The human spine is composed of vertebrae, discs, and tissues that work together to provide it with a wide range of movements and significant load-carrying capability needed for daily physical exercise. However, there is a limited understanding of vibration characteristics in different age groups and the effect of vibration transmission in the spinal column, which may be harmful to the different sections. In this work, a novel finite element model (FEM) was developed to study the variation of vibration absorption capacity due to the aging effect of the different sections of the human spine. These variations were observed from the first three natural frequencies of the human spine structure, which were obtained by solving the eigenvalue problem of the novel finite element model for different ages. From the results, aging was observed to lead to an increase in the natural frequencies of all three spinal segments. As the age increased beyond 30 years, the natural frequency significantly increased for the thoracic segment, compared to lumber and cervical segments. A range of such novel findings indicated the harmful frequencies at which resonance may occur, causing spinal pain and possible injuries. This information would be indispensable for spinal surgeons for the prognosis of spinal column injury (SCI) patients affected by harmful vibrations from workplaces, as well as manufacturers of automotive and aerospace equipment for designing effective dampers for better whole-body vibration mitigation. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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15 pages, 9958 KiB

Open AccessArticle

Topological Optimization of Interconnection of Multilayer Composite Structures

by P. V. Dunchenkin, V. A. Cherekaeva, T. V. Yakovleva and A. V. Krysko

Computation 2023, 11(5), 87; https://doi.org/10.3390/computation11050087 - 25 Apr 2023

Viewed by 1159

Abstract

This study focuses on the topological optimization of adhesive overlap joints for structures subjected to longitudinal mechanical loads. The aim is to reduce peak stresses at the joint interface of the elements. Peak stresses in such joints can lead to failure of both [...] Read more.

This study focuses on the topological optimization of adhesive overlap joints for structures subjected to longitudinal mechanical loads. The aim is to reduce peak stresses at the joint interface of the elements. Peak stresses in such joints can lead to failure of both the joint and the structure itself. A new approach based on Rational Approximation of Material Properties (RAMP) and the Finite Element Method (FEM) has been proposed to minimize peak stresses in multi-layer composite joints. Using this approach, the Mises peak stresses of the optimal structural joint have been significantly reduced by up to 50% under mechanical loading in the longitudinal direction. The paper includes numerical examples of different types of structural element connections. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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15 pages, 2577 KiB

Open AccessArticle

Computational Investigation of Dental Implant Restoration Using Platform-Switched and -Matched Configurations

by Mohammad Afazal, Shubham Gupta, Abhishek Tevatia, Saba Afreen and Arnab Chanda

Computation 2023, 11(4), 79; https://doi.org/10.3390/computation11040079 - 12 Apr 2023

Cited by 2 | Viewed by 1659

Abstract

Dental trauma is a serious and highly prevalent health issue across the globe. Most of the frequent dental injuries result in the loss of teeth and affects the overall quality of life. The loss of a tooth is usually compensated by a dental [...] Read more.

Dental trauma is a serious and highly prevalent health issue across the globe. Most of the frequent dental injuries result in the loss of teeth and affects the overall quality of life. The loss of a tooth is usually compensated by a dental implant. The common methods adopted while placing the implant tooth are platform switching and platform matching. A plethora of works has studied the qualitative performance of these methods across different situations clinically. However, a detailed comparative work studying in-depth the mechanical parameters has not been attempted yet. In this computational work, two commonly available different platform-switched and one platform-matched implant-abutment configurations were compared. A 3D model of an implant (5.5 × 9.5 mm) was designed and inserted into a human mandibular bone block using computer-aided design (CAD) and extracting the clinical imaging data. Three separate models of implant-abutment configurations such as Platform Switched (PS)-I, a 5.5 mm implant with a 3.8 mm wide abutment, Platform Switched (PS)-II, a 5.5 mm implant with a 4.5 mm wide abutment, and Platform Matched (PM), a 5.5-mm implant with a 5.5 mm wide abutment were analyzed. Clinically relevant vertical-, horizontal-, and oblique-type of occlusal loadings were applied to each model to characterize the mechanical response. Mechanical parameters such as von Mises stresses, deformations, and strain energies were obtained using finite element modeling (FEM). These parameters showed lower values for platform switching within the peri-implant bone and that may help to limit marginal bone loss. However, the same parameters were increasing more in the abutment, implant, and screw for the platform-switched implant configuration than that of platform-matched configuration. The computational framework, along with the results, are anticipated to guide the clinicians and medical practitioners in making better decisions while selecting the commonly available methods. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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23 pages, 8445 KiB

Open AccessArticle

Online Multiscale Finite Element Simulation of Thermo-Mechanical Model with Phase Change

by Dmitry Ammosov and Maria Vasilyeva

Computation 2023, 11(4), 71; https://doi.org/10.3390/computation11040071 - 29 Mar 2023

Cited by 2 | Viewed by 1400

Abstract

This paper presents a thermo-mechanical model with phase transition considering changes in the mechanical properties of the medium. The proposed thermo-mechanical model is described by a system of partial differential equations for temperature and displacements. In the model, soil deformations occur due to [...] Read more.

This paper presents a thermo-mechanical model with phase transition considering changes in the mechanical properties of the medium. The proposed thermo-mechanical model is described by a system of partial differential equations for temperature and displacements. In the model, soil deformations occur due to porosity growth caused by ice and water density differences. A finite-element approximation of this model on a fine grid is presented. The linearization from the previous time step is used to handle the nonlinearity of the problem. For reducing the size of the discrete problem, offline and online multiscale approaches based on the Generalized Multiscale Finite Element Method (GMsFEM) are proposed. A two-dimensional model problem simulating the heaving process of heterogeneous soil with a stiff inclusion was considered for testing the mathematical model and the multiscale approaches. Numerical solutions depict the process of soil heaving caused by changes in porosity due to the phase transition. The movement of the phase transition interface was observed. The change of medium properties, including the elastic modulus, was traced and corresponds to the phase transition interface. The proposed multiscale approaches significantly reduce the size of the discrete problem while maintaining reasonable accuracy. However, the online multiscale approach achieves better accuracy than the offline approach with fewer degrees of freedom. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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16 pages, 4474 KiB

Open AccessArticle

Composite Mould Design with Multiphysics FEM Computations Guidance

by Iñaki Garmendia, Haritz Vallejo and Usue Osés

Computation 2023, 11(2), 41; https://doi.org/10.3390/computation11020041 - 17 Feb 2023

Cited by 1 | Viewed by 1828

Abstract

Composite moulds constitute an attractive alternative to classical metallic moulds when used for components fabricated by processes such as Resin Transfer Moulding (RTM). However, there are many factors that have to be accounted for if a correct design of the moulds is sought [...] Read more.

Composite moulds constitute an attractive alternative to classical metallic moulds when used for components fabricated by processes such as Resin Transfer Moulding (RTM). However, there are many factors that have to be accounted for if a correct design of the moulds is sought after. In this paper, the Finite Element Method (FEM) is used to help in the design of the mould. To do so, a thermo-electrical simulation has been performed through MSC-Marc in the preheating phase in order to ensure that the mould is able to be heated, through the Joule’s effect, according to the thermal cycle specified under operating conditions. Mean temperatures of 120 °C and 100 °C are predicted for the lower and upper semi-mould parts, respectively. Additionally, a thermo-electrical-mechanical calculation has been completed with MSC-Marc to calculate the tensile state along the system during the preheating stage. For the filling phase, the filling process itself has been simulated through RTM-Worx. Both the uniform- and non-uniform temperature distribution approaches have been used to assess the resulting effect. It has been found that this piece of software cannot model the temperature dependency of the resin and a numerical trick must have been applied in the second case to overcome it. Results have been found to be very dependent on the approach, the filling time being 73% greater when modelling a non-uniform temperature distribution. The correct behaviour of the mould during the filling stage, as a consequence of the filling pressure, has been also proved with a specific mechanical analysis conducted with MSC-Marc. Finally, the thermo-elastic response of the mould during the curing stage has been numerically assessed. This analysis has been made through MSC-Marc, paying special attention to the curing of the resin and the exothermic reaction that takes place. For the sake of accuracy, a user subroutine to include specific curing laws has been used. Material properties employed are also described in detail following a modified version of the Scott model, with curing properties extracted from experiments. All these detailed calculations have been the cornerstone to designing the composite mould and have also unveiled some capabilities that were missed in the commercial codes employed. Future versions of these commercial codes will have to deal with these weak points but, as a whole, the Finite Element Method is shown to be an appropriate tool for helping in the design of composite moulds. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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11 pages, 5085 KiB

Open AccessArticle

Performance Analysis of SiGe-Cladded Silicon MMI Coupler in Presence of Stress

by Sneha Kumari, Akhilesh Kumar Pathak, Rahul Kumar Gangwar and Sumanta Gupta

Computation 2023, 11(2), 34; https://doi.org/10.3390/computation11020034 - 14 Feb 2023

Cited by 1 | Viewed by 1273

Abstract

In this study, we demonstrate the influence of operating temperature variation and stress-induced effects on a silicon-on-insulator (SOI)-based multi-mode interference coupler (MMI). Here, SiGe is introduced as the cladding layer to analyze its effect on the optical performance of the MMI coupler. SiGe [...] Read more.

In this study, we demonstrate the influence of operating temperature variation and stress-induced effects on a silicon-on-insulator (SOI)-based multi-mode interference coupler (MMI). Here, SiGe is introduced as the cladding layer to analyze its effect on the optical performance of the MMI coupler. SiGe cladding thickness is varied from 5 nm to 40 nm. Characterization of the MMI coupler for ridge waveguides with both rectangular and trapezoidal sidewall slope angle cross-sections is reviewed in terms of power splitting ratio and birefringence. Stress-induced birefringence as a function of operating temperature and cladding thickness for fundamental mode have been calculated. A trapezoidal waveguide with 40 nm of cladding thickness induces more stress and, therefore, affects birefringence more than a rectangular waveguide of any thickness. Simulation results using the finite element method (FEM) confirmed that operating temperature variation, upper cladding thickness, and its stress effect are significant parameters that drastically modify the performance of an MMI coupler. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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13 pages, 6475 KiB

Open AccessArticle

A Novel Computational Model for Traction Performance Characterization of Footwear Outsoles with Horizontal Tread Channels

by Shubham Gupta, Subhodip Chatterjee, Ayush Malviya, Gurpreet Singh and Arnab Chanda

Computation 2023, 11(2), 23; https://doi.org/10.3390/computation11020023 - 02 Feb 2023

Cited by 5 | Viewed by 1427

Abstract

Slips and falls are among the most serious public safety hazards. Adequate friction at the shoe–floor contact is necessary to reduce these risks. In the presence of slippery fluids such as water or oil, the footwear outsole is crucial for ensuring appropriate shoe–floor [...] Read more.

Slips and falls are among the most serious public safety hazards. Adequate friction at the shoe–floor contact is necessary to reduce these risks. In the presence of slippery fluids such as water or oil, the footwear outsole is crucial for ensuring appropriate shoe–floor traction. While the influence of flooring and contaminants on footwear traction has been extensively studied across several outsole surfaces, limited studies have investigated the science of outsole design and how it affects footwear traction performance. In this work, the tread channels of a commonly found outsole pattern, i.e., horizontally oriented treads, was varied parametrically across the widths (i.e., 2, 4, 6 mm) and gaps (i.e., 2, 3, 4 mm). Nine outsole designs were developed and their traction, fluid pressures, and fluid flow rates during slipping were estimated using a mechanical slip testing and a CFD-based computational framework. Outsoles which had wider tread (i.e., 6 mm) surfaces showed increased slip risks on wet flooring. Outsoles with large gaps (i.e., 4 mm) exhibited increased traction performance when slipped on wet flooring (R² = 0.86). These novel results are anticipated to provide valuable insights into the science of footwear traction and provide important guidelines for the footwear manufacturers to optimize outsole surface design to reduce the risk of slips and falls. In addition to this, the presented CFD-based computational framework could help develop better outsole designs to further solve this problem. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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11 pages, 2221 KiB

Open AccessArticle

Size-Dependent Switching in Thin Ferroelectric Films: Mathematical Aspects and Finite Element Simulation

by Elena Veselova, Anna Maslovskaya and Alexander Chebotarev

Computation 2023, 11(1), 14; https://doi.org/10.3390/computation11010014 - 15 Jan 2023

Cited by 1 | Viewed by 1613

Abstract

The paper is devoted to the theoretical analysis and numerical implementation of a mathematical model of a nonlinear reaction–diffusion system on the COMSOL Multiphysics platform. The applied problem of the computer simulation of polarization switching in thin ferroelectric films is considered. The model [...] Read more.

The paper is devoted to the theoretical analysis and numerical implementation of a mathematical model of a nonlinear reaction–diffusion system on the COMSOL Multiphysics platform. The applied problem of the computer simulation of polarization switching in thin ferroelectric films is considered. The model is based on the Landau–Ginzburg–Devonshire–Khalatnikov thermodynamic approach and formalized as an initial-boundary value problem for a semilinear parabolic partial differential equation. The theoretical foundations of the model were explained. The user interface design application was developed with COMSOL Multiphysics. A series of computational experiments was performed to study the ferroelectric hysteresis and temperature dependences of polarization on the example of a ferroelectric barium titanate film. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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19 pages, 11913 KiB

Open AccessArticle

Modeling of Quantum Dots with the Finite Element Method

by G.A. Mantashian, P.A. Mantashyan and D.B. Hayrapetyan

Computation 2023, 11(1), 5; https://doi.org/10.3390/computation11010005 - 02 Jan 2023

Cited by 8 | Viewed by 2671

Abstract

Considering the increasing number of experimental results in the manufacturing process of quantum dots (QDs) with different geometries, and the fact that most numerical methods that can be used to investigate quantum dots with nontrivial geometries require large computational capacities, the finite element [...] Read more.

Considering the increasing number of experimental results in the manufacturing process of quantum dots (QDs) with different geometries, and the fact that most numerical methods that can be used to investigate quantum dots with nontrivial geometries require large computational capacities, the finite element method (FEM) becomes an incredibly attractive tool for modeling semiconductor QDs. In the current article, we used FEM to obtain the first twenty-six probability densities and energy values for the following GaAs structures: rectangular, spherical, cylindrical, ellipsoidal, spheroidal, and conical QDs, as well as quantum rings, nanotadpoles, and nanostars. The results of the numerical calculations were compared with the exact analytical solutions and a good deviation was obtained. The ground-state energy dependence on the element size was obtained to find the optimal parameter for the investigated structures. The abovementioned calculation results were used to obtain valuable insight into the effects of the size quantization’s dependence on the shape of the QDs. Additionally, the wavefunctions and energies of spherical CdSe/CdS quantum dots were obtained while taking into account the diffusion effects on the potential depth with the use of a piecewise Woods–Saxon potential. The diffusion of the effective mass and the dielectric permittivity was obtained with the use of a normal Woods–Saxon potential. A structure with a quasi-type-II band alignment was obtained at the core size of ≈2.2 nm This result is consistent with the experimental data. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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16 pages, 5907 KiB

Open AccessArticle

Study of the Sloshing Dynamics in Partially Filled Rectangular Tanks with Submerged Baffles Using VOF and LES Turbulence Methods for Different Impact Angles

by Xavier Vallés Rebollo, Ehsan Sadeghi, Ibuki Kusano and Andrés-Amador García-Granada

Computation 2022, 10(12), 225; https://doi.org/10.3390/computation10120225 - 19 Dec 2022

Cited by 3 | Viewed by 2369

Abstract

This research studies how the angle and dimensions of a single baffle affect the dynamics of a fluid in a closed rectangular tank under an accelerated harmonic vibration in resonance. A half-filled non-deformable rectangular tank with a single centered submerged baffle has been [...] Read more.

This research studies how the angle and dimensions of a single baffle affect the dynamics of a fluid in a closed rectangular tank under an accelerated harmonic vibration in resonance. A half-filled non-deformable rectangular tank with a single centered submerged baffle has been simulated using ANSYS^® FLUENT. The study aims to characterize the effect of changing the baffle’s angle; hence, 10 simulations have been performed: without a baffle, 90°, 30°, 60°, 120° and 150°, either maintaining the baffle’s length or the projected height constant. The computational fluid dynamics (CFD) method using volume of fluid (VOF) and large eddy simulation (LES) are used to predict the movement of the fluid in two dimensions, which have been benchmarked against experimental data with excellent agreement. The motion is sinusoidal in the +X direction, with a frequency of oscillation equal to its first vibration mode. The parameters studied have been the free surface elevation, values at three different points and maximum; the center of gravity’s position, velocity, and acceleration; and the forces against the tank’s walls. It has been found that the 90° angle has the most significant damping effect, stabilizing the free-surface elevation, reducing the center of gravity dispersion, and leveling the impacting forces. Smaller angles also tame the sloshing and stabilize it. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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18 pages, 7318 KiB

Open AccessArticle

Modeling the Static and Dynamic Behaviors of a Large Heavy-Duty Lathe Machine under Rated Loads

by Chien-Yu Lin, Yuan-Ping Luh, Wei-Zhu Lin, Bo-Chen Lin and Jui-Pin Hung

Computation 2022, 10(12), 207; https://doi.org/10.3390/computation10120207 - 25 Nov 2022

Cited by 3 | Viewed by 3976

Abstract

The static and dynamic performances of a machine tool structure are considered to constitute the primary factors affecting the load-carrying capacity, geometric accuracy and surface precision of the workpiece. The machining performance of a large machine tool under stable conditions is effectively determined [...] Read more.

The static and dynamic performances of a machine tool structure are considered to constitute the primary factors affecting the load-carrying capacity, geometric accuracy and surface precision of the workpiece. The machining performance of a large machine tool under stable conditions is effectively determined by its dynamic response to the cutting force at low-frequency excitation. This study, therefore, investigated the static and dynamic characteristics of a large heavy-duty lathe machine tool in which the headstock and tailstock comprised critical component modules supporting a large workpiece during low-speed machining. Using a finite element model, the influences of the structural modules on the static and dynamic characteristics of the lathe were analyzed, considering the effects of the workpiece load. The results indicated that the fundamental vibration modes of the lathe were primarily dominated by headstock, tailstock, and workpiece behaviors. The maximum compliances of the lathe under the rated load were found to occur at relatively low frequencies (22, 40.7, and 82.7 Hz) and increase with the reduction in workpiece weight. Notably, these modal frequencies were significantly higher than the maximum rotational speed of the spindle (450 rpm). In addition, the dynamic rigidity corresponding to the rated speed was higher than that induced at the natural frequency. These results indicate that the subject lathe possesses sufficient capacity to sustain the cutting load during stable turning machining. This study can, therefore, help designers improve the performance of machine tools for future fabrication. Full article

(This article belongs to the Special Issue Application of Finite Element Methods)

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