Nite Element Method Research Articles

NUMERICAL SOLUTION FOR THE DISTRIBUTION OF THE ELECTROMAGNETIC AND THERMAL FIELDS OF AN AIR-CORE TRANSFORMER

The article presents a numerical solution for the distribution of the electromagnetic and thermal fi elds of an air-core transformer using the fi nite element method. The distribution of the magnetic fi eld is determined for the dynamic steady state and magnetic nonlinear core characteristics. The model presented facilitates the establishment of criteria for optimizing transformer operation under various load conditions, environments as well as in the case of failures. Thus, the transformer can operate at maximum capacity while, at the same time, the probability of faults due to overheating is reduced to a minimum.

Strength calculation of the device for carrying out maintenance and repair of the chassis of fire trucks

The classifi cation is presented and the main designs of pullers designed for maintenance and repair of the chassis of middle class fi re trucks. The design of the puller was proposed, which differs from the existing analogues in smaller dimensions and weight with a constant load in the screw-nut transmission. The development of the device design was based on the use of materials with higher strength characteristics in a friction pair. A three-dimensional model is presented, which shows that the design of the device includes additional mounting holes for changing the confi guration of the grippers, and the puller screw is equipped with two socket wrench heads. The effi ciency of the developed design of the stripper was evaluated by the fi nite element method.

Analysis and Optimization of the Operating Range of a Monopole Antenna Involving ‘Meander’ Type Slot In- homogeneities

Subject and Purpose. The paper presents results of numerical modeling and experimental studies of a disk-shaped microstrip antenna involving ‘meander’ type slotted inhomogeneities. The work has been aimed at optimizing the operating range of the antenna and matching it to external circuits through the use of additional structural elements and appropriate feeding techniques. Methods and Methodology. The design features a circular disk-shaped microstrip resonator containing within its plane groups of slotted inhomogeneities which form a segmented meander line, with the segments oriented relative one another at an angle of 120°. The antenna could be fed through a segment of a screened coplanar line. The location of the screening plane of the coplanar line, as well as its dimensions, were variable. Numerical simulation was carried out within the ‘semi-open resonator’ technique using the finite element method. The degree of optimization of the operating range was estimated, based on analyzing spectral characteristics of the antenna, for a variety of its geometric parameters, and the magnitude of the return loss over a given frequency range. Measurements of the VSWR were carried out with reflectometers. Results. Frequency and power characteristics of a monopole, disk-shaped microstrip antenna have been analyzed and optimized over a wide frequency range. Mechanical dimensions of the additional shielding plane and location thereof have been identified as factors having significant influence upon the frequency-dependent, polarizational and power characteristics of the antenna. Conclusions. The operating frequency range, spectral and power characteristics of a monopole, disk-shaped microstrip antenna have been studied both theoretically and experimentally. Numerical simulations were carried out with the use of the fi nite element method. Experimental studies of the frequency characteristics were performed using reflectometry techniques. The antenna considered can find practical application over a wide frequency range, either as a single radiating element in a device or system, or a constituent part of an antenna array.

Тепловая модель асинхронного тягового электродвигателя тепловоза

Objective: Evaluation of the temperature regime of the windings of an asynchronous traction electric motor with a squirrel-cage rotor (ATED) of the DAT-350 type of a 2TE25A diesel locomotive using the de- Современные технологии – транспорту 467 ISSN 1815-588Х. Известия ПГУПС 2021/4 veloped thermal model. Methods: The research was carried out by the fi nite element method in the application for calculating steady-state temperature fi elds SolidWorks. Resuls: To ensure the specifi ed service life of the ATED, the temperature rise of the windings must be limited to safe values, based on the insulation class. Therefore, it is crucial that designers and operators have access to accurate and computati onally effi cient, physics-based ATED thermal behavior modeling tools. Practical results: Using the proposed methods, it is possible to accurately and effectively evaluate the thermal characteristics of ATED of promising diesel locomotives. In addition, designers can easily and quickly adjust the parameters and performance characteristics of the ATED in such a way that they are conducive to improving the overall performance of the locomotive.

Finite element method in computer simulation for improved patient care in dentistry: A systematic review

Background. The fi nite element method is gaining acknowledgment in Russia and other developed countries in a range of areas, including medicine. In stomatology, the method is applicable in research and implication of novel treatment and relevant material design.Objective. The review highlights usage of the fi nite element method in computer simulation to improve quality of patient dental care.Methods. The review analyses the state-of-the-art in current scientific literature. Records were mined in the PubMed and e-Library databases at a depth of 10 years, with selective inclusion of earlier articles. The query keywords were: finite element method [метод конечных элементов], computer simulation [компьютерная симуляция], quality of life improvement [повышение качества жизни], oral diseases [заболевания полости рта], dental treatment [стоматологическое лечение].Results. The review systematically surveys 56 scientific papers in the focus area for current state-of-the-art in the finite element analysis-empowered simulation in dentistry. The method’s rising employment is conditioned by its flexibility, 3D-object modelling simplicity and the rapid acquisition of reliable high-quality output. Its undoubted paramount advantage in dentistry is an explicit software visualisation of reliable results through co-modelling of multiple oral parameters.Conclusion. The growing acquaintance, mastering and use of this technique among researchers around the globe will give impetus to novel diagnosis and treatment, as well as relevant management algorithms in particular patient categories to enable personalisation of even mass dental check-up. This will reduce the number of visits, peri- and posttreatment error and complication rates for the improved patient’s quality of life and social rehabilitation.

FINITE ELEMENT ANALYSIS OF ROOT RESORPTION ASSOCIATED WITH TOOTH MOVEMENT: A SYSTEMATIC REVIEW”

Background: The purpose of this systematic review was to examine the available evidence of root resorption during orthodontic treatment with different force systems using nite element analysis. Methods: The following electronic databases were searched for literature till June 2021 : Pro-Quest Dissertation Abstracts and Thesis database, Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Google Scholar, Embase, US National Library of Medicine, and National Research Register. Root resorption studied under orthodontic forces, which simulated under various technique of nite element method (3D FEM) models were included in the study. The selected studies were assessed for the risk of bias using the Cochrane Collaboration risk of bias tool. The “trafc plot” and “weighted plot” risk of bias distribution were designed using the ROBVIS tool. The authors extracted and analyzed the data. Results: Fourteen studies fullled the inclusion criteria. The risks of biases were high for all studies.Data on quantity and direction of force applied, different type of root morphology and its various surface inuence on root resorption were extracted. The outcomes of the included studies were heterogeneous. Conclusion: Based on the current available literature, for reducing root resorption the excessive force may accelerate root resorption when it exceeds the typical human capillary blood pressure. Root resorption occurs more when extrusion/intrusion and tipping occur than when teeth actually move. A tooth with little or no orthodontic force load hardly shows any root resorption compared to one that has orthodontic force.

О ПРОВЕРКЕ ГИПОТЕЗЫ КОСИНУСНОГО РАСПРЕДЕЛЕНИЯ НАПРЯЖЕНИЙ В КОНТАКТЕ «ВАЛ-ОТВЕРСТИЕ»

One of the most common connection types in mechanical engineering and construction is the shaft-hole connection. The mechanical stresses caused by its loading are distributed in the contact zone of the loaded parts of the joint. In some cases, they can lead to destruction. Therefore, while designing, it is important to analyze the mechanical stresses in the contact zone. Traditionally, calculations assume that the contact stresses are distributed according to the cosine law. However, this is not entirely true, especially with diff erent shaft and hole diameters. The authors examined theoretical studies of the contact zone of the shaft and the hole (including the cases of diff erent diameters) and the stress distribution in the contact zone. Based on the studies, they performed numerical calculations in the APMWinMachine environment to determine the stresses in the volume of the shaft and the plate with a hole when loading the shaft-hole connection. The analyses were performed for the two-dimensional case by the fi nite element method in the APMStructure program. The results show that when the diameters in the connection are equal, the stress distribution is close to the cosine law. In this case, only one stress raiser occurs in the contact zone, which is located on the line of action of the loading force. However, if there is a slight discrepancy in the shaft and hole diameters, there are three stress raisers in which the connection may break – the central zone and two side zones. The angular distance between them can be determined based on the known theoretical formulas. The authors made an experiment with a plexiglass model, which qualitatively confi rmed the correctness of the analysis performed.

A new way to identify thin sheet behaviour: Micro-InDef

Incremental forming is a rapid prototyping process which uses a forming tool toform a sheet metal according to a predetermined trajectory. In this work, a micro incremental deformation test (Micro InDef test) derived from the principle of single point incremental sheet forming is developed and proposed. A complex mechanical loading is applied and has a strong potential for the identication of inelastic behavior using inverse method. In the rst part, this work addresses the parameters identication and validation procedures of ductile damage behavior of ultra-thin sheet metal under very large strain during this instrumented Micro InDef test. An inverse nite element method based on the comparison between numerical and experimental axial forming forces of the micro incremental deformation test is employed to extract a coupled ductile damaged plastic model. In the second part, the objective is to prove the reliability of ductile damage parameters identication using forming force. The richness of data contained in forming force is quantied and compared to the one from tensile test. Firstly, the verication of the estimated parameter's reliability is done via a simple analysis based on the forming force sensitivity to material parameters and secondly by calculating elastoplastic and elastoplastic with ductile damage.

Estimation of square die backward extrusion forces of bar stock

Тhe results for estimation of the square die extrusion forces of cylindrical billets are presented. The study is performed on the basis of the fi nite element method. The results obtained during the simulation are analyzed statistically. Regression dependences for forces are obtained, with the help of which reverse extrusion studies are performed.

A new numerical application of the generalized Rosenau-RLW equation

In this article, a collocation fi nite element method based on septic B-splines as a tool has been carried out to obtain the numerical solutions of the nonlinear generalized Rosenau-RLW equation. One of the advantages of this method is that when the bases are chosen at a high degree, better numerical solutions are obtained. Effectiveness of the method is demonstrated by solving the equation with various initial and boundary conditions. Also, in order to detect the performance of the method we have computed L2 and L1 error norms and two lowest invariants IM and IE: The obtained numerical results have been compared with some of those in the literature for similar parameters. This comparison clearly shows that the obtained results are better than and found in good conformity with the some earlier results. Stability analysis denotes that our algorithm, based on a Crank Nicolson approximation in time, is unconditionally stable.

Computational Analysis of Shallow Water Waves with Korteweg-de Vries Equation

The collocation nite element method is applied to obtain solitary wave solutions to Korteweg-de Vriesequation with power law nonlinearity. The stability and error analysises are also carried out for these waves.Additionally, conservation laws are studied numerically.

Investigating the seismic behavior of RC shear walls with openings strengthened with FRP sheets using different schemes

This paper investigates the seismic behavior of RC shear walls strengthened by Fiber Reinforced Polymer (FRP) composites. In this research, the e ects of strengthening shear walls with di fferent strengthening schemes and also strengthening walls with openings in di fferent dimensions and locations are studied. The development of nonlinear nite element methods has improved the accuracy of seismic analysis of complex structures. In this study, the ABAQUS software is used to investigate the nal resisting parameters,ductility, and behavior factor in these walls using nonlinear static analysis. The ndings prove that the applied strengthening schemes increase the nal strength of the wall. Also, the increasing ductility, behavior factor, and increased overstrength factor in some of these walls compared with original walls are observed. The ndings also prove that special openings with limited dimensions to improve seismic behavior of the wall are e ective, and the only limitation of using these openings is decreasing the nal strength which can be made up by using a proper strengthening scheme of FRP.

Моделирование тепловых процессов в контактном проводе методом конечных элементов в программном комплексе Comsol Multiphysics 5.2

Моделирование тепловых процессов в контактном проводе методом конечных элементов в программном комплексе Comsol Multiphysics 5.2

HETEROGENEOUS HARDENING OF MACHINES PARTS BY SURFACE PLASTIC DEFORMATION

The operational characteristics of the components of mining and metallurgical machinery can be improved by forming the heterogeneous-hardened surface layer. The article considers the forming methods of heterogeneous structure by surface plastic deformation (SPD). The importance of identifying the nature of the infl uence of parameters of heterogeneous hardened layer on the performance of machine parts are indicated. Modeling of the process of heterogeneous hardening of SPD of the fi nite element method was executed. The authorsgive recom mendations about application of heterogeneous hardening of SPD for hardening the heavy-duty parts. It was found that the use of diff erent methods of SPD allows widely vary the degree of depth and the uniformity of the hardening of machine parts. Therefore, this increase in operation life of responsible highly loaded parts operating under fatigue loading due to hardening of the heterogeneous surface layer may reach 1.5 times or more.

分子動力学法を用いた半導体微細パターン材のアモルファスシリコン層における酸化膜形成解析と真性応力評価

The intrinsic stress at hetero interface is one of key factors to induce the structural instability of micropatterning in semiconductor devices, and it is essential to quantitatively predict the intrinsic stress in terms of atomic structure. In our previous study, we established the method to predict the lateral undulation buckling of micropattern using continuum buckling theory and .nite element method. However, there is a possibility that several-nanometer surface oxidized layer, which is formed during oxygen plasma etching process, involves the intrinsic stress of the order of 1 GPa and affects the buckling criteria. Since the experimental measurement of the stress of such a nano-scale layer is beyond the present technology, an atomistic simulation could be a tool to discuss the possibility. In this study, we make a molecular dynamics model for the plasma etching and predict the intrinsic stress of the oxidized layer on the surface of amorphous silicon (a-Si). Our approach reveals that the layer thickness depends on the incident energy of oxygen and that the intrinsic stress exceeds 1 GPa. Therefore, we conclude that it would be possible for the oxidized a-Si film to trigger the buckling of micropatterning even if the initial a-Si structure involves no stress.

Taylor-Petrov-Galerkin method for the numerical solution of KdV equation

In order to nd the approximate solution of the KdV equation, we use the nite element method of Taylor-Petrov-Galerkin, in which discretization in the time variable is carried out using Taylor series expansion and for discretization in space are considered as test functions cubic B-splines and Legendre polynomials as weight functions. These functions are adequate in that they satisfy continuity, integrability and orthogonality required to apply the method.

A Research on Nitinol Alloy Material Fatigue Behavior Analysis of Cardiovascular Stent in Medical Engineering

Biocompatible cardiovascular stents are small cylindrical support structures introduced into the stenosed arteries to reopen the lumen and to restore blood ow in treating heart disease, which have revolutionized interventional cardiology. Cardiovascular stent designers are confronted with two basic requirements, such as an in nite life and the thinnest wires. Pulsatile pressure, repetitive mechanical forces, within the coronary artery may result in stent fatigue and fracture after stent implantation, particularly in patients with complex coronary disease. This research describes the simulation analysis of cardiovascular stents, to provide designers with estimates of their in vivo structural behavior and fatigue properties. Stent material failure or device fatigue remains major concern for stent manufactures and researchers. The objective of this research was to simulate the mechanical behavior of the stent using nite element method. A nite element analysis (FEA) of cardiovascular stent under fatigue cyclic loading conditions is presented. Commercial software was employed to study the fatigue performance of nitinol alloy materials in new stent systems. The e ects of deployment, and static cyclic pressure loading on cardiovascular stent fatigue life were simulated and analyzed for nitinol alloy material. The investigation results displayed a signi cant correlation between material combinations, stent loading, and fatigue behavior.

A fictitious domain approach for Fluid-Structure Interactions based on the eXtended Finite Element Method.

In this work we develop a ctitious domain method for the Stokes problem which allows computations in domains whose boundaries do not depend on the mesh. The method is based on the ideas of Xfem and has been rst introduced for the Poisson problem. The uid part is treated by a mixed nite element method, and a Dirichlet condition is imposed by a Lagrange multiplier on an immersed structure localized by a level-set function. A stabilization technique is carried out in order to get the convergence for this multiplier. The latter represents the forces that the uid applies on the structure. The aim is to perform uid-structure simulations for which these forces have a central role. We illustrate the capacities of the method by extending it to the incompressible Navier-Stokes equations coupled with a moving rigid solid.

Finite Element Method for Static Problems of Cubic Quasicrystals

Finite Element Method for Static Problems of Cubic Quasicrystals L.-Z. Yang, F.-M. He and Y. Gaoa,∗ College of Science, China Agricultural University, Beijing 100083, China College of Engineering, China Agricultural University, Beijing 100083, China Sichuan Hydropower Investment and Management Group Ltd, 611130, China We put forward a nite element method for static problems of cubic quasicrystals by variation of a suitable general potential functional. As an example we study a quasicrystal column containing a penny-shaped crack. The comparison with analytical results shows that the precision and e ciency of the numerical solution are satisfactory. The procedure can be used to solve more complicated boundary value problems and can be extended towards more sophisticated methods of crack tip loading analysis.

EXTRAPOLATED EXPANDED MIXED FINITE ELEMENT APPROXIMATIONS OF SEMILINEAR SOBOLEV EQUATIONS

Abstract. In this paper, we construct extrapolated expanded mixed nite element approximations to approximate the scalar unknown, itsgradient and its ux of semilinear Sobolev equations. To avoid the di-culty of solving the system of nonlinear equations, we use an extrapolatedtechnique in our construction of the approximations. Some numerical ex-amples are used to show the eciency of our schemes. 1. IntroductionIn this paper, we consider the following semilinear Sobolev equation(1.1) u t (u x + u tx ) x = f(x;t;u); in (0;L) (0;T];(1.2) u x (0;t) + u tx (0;t) = u x (L;t) + u tx (L;t) = 0; in (0;T];(1.3) u(x;0) = u 0 (x); in (0;L);where 0 <T<1and u 0 (x) and f(x;t;u) are suciently smooth functions sothat (1.1)-(1.3) has a suciently smooth unique solution. The problem (1.1)-(1.3) arises in the various areas, for examples, in the ow of uids through ssured materials [1] and thermodynamics [4]. For details about the physicalsigni cance and the existence and uniqueness of the solutions of the Sobolevequations, we refer to [1, 2, 3, 4, 6, 7, 12].The advantages of mixed nite element formulations can be summarizedas follows: one can simultaneously approximate both the displacement and theux(or the stress or the pressure) and one can approximate the ux to the sameorder of convergence as the unknown scalar u(x;t). Due to these advantages,the mixed nite element method has been applied to some types of Sobolevequations by the authors in [8, 10, 11].