Finite Element Method Calculations Research Articles

Design of Simple and Double Ridge Waveguide T-Coupler for Space Domain

The T-Coupler or the magic tee (or magic T or hybrid tee) is a hybrid or 3 dB coupler used in microwave systems. It is an alternative to the rat-race coupler. In contrast to the rat-race, the three-dimensional structure of the magic tee makes it less readily constructed in planar technologies such as micro strip or strip line. The magic tee was originally developed in World War II, and first published by W. A. Tyrell of Bell Labs in a 1947 IRE paper. Robert L. Kyhl and Bob Dicke independently created magic tees around the same time. This paper illustrates simple and double ridge waveguide T-coupler. The relationships between the scattering variables in this sort of network are fixed by the unitary condition. Such a network has the properties that it is a matched device with one adjacent port decoupled from any incident port. The object of this paper is to present some results of simulation on the coupling and directivity of double ridge cross-waveguide couplers in a field ridge waveguide. This results are obtain by Ansoft HFSS using the Finite Element Method (FEM) calculations and the Genetic Algorithms method, and which show good performance.

Grey wolf optimiser in design of leaf springs of railway vehicles

The paper deals with the usage of grey wolf optimiser (GWO) in the optimal design of leaf springs with railway vehicles. The main goal is minimisation of mass of leaf spring, with retention required characteristics of suspension system. Based on the exposed analytical model of leaf springs and requirements for suspension system, an optimisation model is developed. The developed model and GWO are applied in the optimal design of leaf spring of 4-axled freight wagon for axle load of 200 kN. The obtained results have shown that the proposed model and GWO provide significant reduction of mass of leaf springs of about 46.7%, in relation to the conventional design method. In addition, the numerical model of leaf spring is developed and the design obtained by GWO is verified by finite element method (FEM) calculation. Proposed approach enables significant material savings and reduction of production costs, as well as the reduction of design time of leaf springs of railway vehicles.

Yielding behavior of model magnetorheological fluids.

The yielding behavior of magnetorheological fluids is revisited through the use of finite element method calculations on model structures and carefully conducted experiments in a magnetorheometer. Model structures investigated in this work are monoclinic lattices with simple and body centered bases. From the simulation point of view we emphasize the influence of the interparticle gap separation. From the experimental point of view we elucidate the importance of the magnetic field application and the occurrence of slip at the confining surfaces. Simulations demonstrate that the yield stress τ0 scales with the interparticle center-to-center distance h as τ0/M2 ∝ h-6 where M is the particle magnetization. A good agreement is found when the simulated yield stresses are compared with the experimental ones, independent of the particular packing and interparticle gap.

Behavior characterization of viscoelastic materials for the finite element method calculation applying Prony series

Behavior characterization of viscoelastic materials for the finite element method calculation applying Prony series

Analytical study of flat and curved trapezoidal cold formed steel sheets by means of the yield line theory. Part 2: Curved sheets with transverse corrugations

The article presents a study of self-supporting arched roofs made from trapezoidal sheets by press-forming a series of transverse corrugations. The study is particularly focused on the effect of these corrugations. To this end, a study has been made of trapezoidal sheets with and without transverse corrugations and the results compared. Three approaches have been considered: Finite Element Method (FEM), experimental tests, and analytical calculations carried out with the Yield Line Theory (YLT). In the first part of the present article, the results of analyses performed with a rather elaborate finite element model are shown, as well as being verified with experimental tests. The FEM results demonstrate that transverse corrugations can have an important effect on the behavior and ultimate strength of the sheets. In the second part, the YLT models developed in the companion article, on the analysis of flat trapezoidal sheets, are adapted to the arched roofs. These analytical models have proved effective in facilitating full understanding of the behavior of curved sheets, as well as predicting, approximately, the loss of strength caused by the transverse corrugations.

Full finite element models and reduction strategies for the simulation of friction-induced vibrations of rolling contact systems

The aim of this paper is to develop a full Finite Element (FE) computational method for the dynamics of unstable frictional rolling contact systems in order to calculate reference solutions in many applications, especially curve squeal for railway transportation but also roller bearing or metal cutting. The proposed method is characterized by the use of a fine FE discretization of the contact surface in a Eulerian frame, nonlinear frictional contact laws and model reduction techniques. An application to the frictional rolling contact between two annular cylinders is presented in both quasi-static and dynamic cases with mode coupling instabilities. The validation of the approach in quasi-static conditions is carried out by comparison with CONTACT software. Stability and transient results show that the technique is able to simulate friction-induced vibrations at high frequencies. Reduced models are tested and show a good agreement with the full model.

Determination of Load-bearing Capacity of Reinforced Concrete Slabs with the Aid of Computer Program PRINS

The finite element method of calculation of reinforced concrete slabs strengthened with composite fabrics based on carbon fibers, implemented in the PRINS program, is considered. The method is designed for analyzing the stress-strain state of reinforced concrete structures when cracks in concrete and plastic deformations in the reinforcement arise. The calculation is carried out in increments, and at each step of loading a variable stiffness matrix is used. Its constant part represents the stiffness matrix at the beginning of the loading step, and the variable one is calculated taking into account the stress-strain state at the end of the current iteration. The variable part of the stiffness matrix, multiplied by the displacement vector found at the previous iteration, is transferred to the right side of the system of equations and is considered as an additional load. When cracks occur or when plastic strains appear, the stresses are corrected in accordance with the specified deformation diagrams. Therefore, at the end of the loading step the equilibrium conditions are checked. If necessary, the external and internal forces are balanced. When considering plastic deformations in concrete and reinforcement, the theory of plastic flow and the Huber-Mises yield criterion, modified taking into account the experimental studies of Kupfer et al, are used. An example of the reinforced concrete slab analysis with different variants of strengthening by composite and without strengthening is given. The results of the calculation are analyzed. The possibility of studying of the stress-strain state on the entire path of loading of reinforced concrete slabs up to destruction is shown.

Static simulation to horse shoes alternative materials based basic polymeric foam reinforced fiberglass with ANSYS software

In this journal, we used Finite Element Method (FEM) calculations based on ANSYS software. The software will involves the value of the material properties. Then, will used to simulate the manufacture of horse shoe, when the horse stood silent, for fiberglass reinforced polymer materials and compared with the usual materials for horse shoe, the Mild Carbon Steel (A36) so that will be obtained which is the best between the two materials. In this simulation work, the horse shoe receives a load of 500 kg. From this simulation we will obtain Equivalent Stress, Normal Stress on each axis (X, Y, Z) from the loading direction experienced by horse shoes. Equivalent equivalence values of 0.21509 MPa polymeric foam while Mild Carbon Steel (A36) 0.1034 MPa and normal polymeric foam voltage values for X-axis 0.016426, Y -0.007111 and Z 0.0695, while Normal Stress from Mild Carbon Steel (A36) for X axes 0.02233, Y 0.0204 and Z 0.047. The simulation results provide an understanding of the normal force resistance of polymeric foam materials for Mild Carbon Steel (A36) materials, whereas for polymeric foam materials the equivalent stress is superior to Mild Carbon Steel (A36)

Lattice Boltzmann method applied to antiplane shear loading of a stationary crack

AbstractIn this work, the dynamic behavior of linear elastic solids under antiplane shear deformation is studied by the Lattice Boltzmann method (LBM). The governing set of partial differential equations reduces to a scalar wave equation for the out of plane displacement in a two dimensional domain. We use the approach developed by Guangwu as starting point to solve this problem numerically. The numerical performance of the lattice Boltzmann scheme is tested for a stationary crack which can be compared to an analytical solution. Furthermore the performance of the lattice Boltzmann simulations are compared to classical Finite Element Method (FEM) computations with regard to calculation time and accuracy. Finally the stability with respect to the relaxation parameter is studied.

Experimental and numerical analyses on nonlinear behaviour of wooden parallel chord trusses composed of self-tapping screws

Five different wooden parallel chord trusses were made of Canadian spruce 2 by 4 lumbers. Chord–web nodal points were composed of self-tapping-screws (STS) whose numbers per nodal point and allocations in nodal point were considered as the main experimental parameters which were varied from 2rows-2lines till 2rows-4lines. Load–slip relationships at nodal point were evaluated using the joint specimens made of similar materials. These parallel chord trusses were modeled using a finite element method (FEM) program by taking not only nonlinearity of nodal point joints but also material nonlinearity of chord members using fiber model into consideration. Strength properties of the chord members were deduced via specific gravity of chord member based on the regression equations given by a literature. Static monotonic central point loading tests were conducted on five specimens to investigate nonlinear behaviors of wooden parallel chord trusses. Comparisons between observed results by experiments and computed ones by FEM calculations showed a tendency that material nonlinearity gave less effect on the total nonlinear behaviour of the specimens when joint performance was inferior, on the other hand, as the joint performance increased material nonlinearity gave dominant effect on the total nonlinear behaviour of the specimens.

Numerical mode matching for sound propagation in silencers with granular material

This work presents an efficient numerical approach based on the combination of the mode matching technique and the finite element method (FEM) to model the sound propagation in silencers containing granular material and to evaluate their acoustic performance through the computation of transmission loss ( TL ). The methodology takes into account the presence of three-dimensional (3D) waves and the corresponding higher order modes, while reducing the computational expenditure of a full 3D FEM calculation. First, the wavenumbers and transversal pressure modes associated with the silencer cross section are obtained by means of a two-dimensional FEM eigenvalue problem, which allows the consideration of arbitrary transversal geometries and material heterogeneities. The numerical approach considers the possibility of using different filling levels of granular material, giving rise to cross sections with abrupt changes of properties located not only in the usual central perforated passage, but also in the transition between air and material, that involves a significant change in porosity. After solving the eigenvalue problem, the acoustic fields (acoustic pressure and axial velocity) are coupled at geometric discontinuities between ducts through the compatibility conditions to obtain the complete solution of the wave equation and the acoustic performance ( TL ). The granular material is analysed as a potential alternative to the traditional dissipative silencers incorporating fibrous absorbent materials. Sound propagation in granular materials can be modelled through acoustic equivalent properties, such as complex and frequency dependent density and speed of sound. TL results computed by means of the numerical approach proposed here show good agreement with full 3D FEM calculations and experimental measurements. As expected, the numerical mode matching outperforms the computational expenditure of the full 3D FEM approach. Different configurations have been studied to determine the influence on the TL of several parameters such as the size of the material grains, the filling level of the chamber, the granular material porosity and the geometry of the silencer cross section. • Numerical mode matching is applied to sound waves in silencers with granular medium. • It allows efficient computation of geometries with arbitrary cross section. • TL curves show good agreement with full 3D FEM results and experimental measurements. • The acoustic influence of granular size and silencer cross section is analysed.

Modal Analysis of a Thick-Disk Rotor with Interference Fit Using Finite Element Method

This paper is concerned with the modal analysis of a thick-disk rotor, which consists of an elastic shaft with a rigid thick disk assembled by interference fit, and the width of the thick disk is not negligible. Firstly, the friction moment on the contact surface of disk and shaft is deduced in terms of elastic theory, and a new enhanced coefficient of bending stiffness of assembly body is proposed and calculated for the first time. Secondly, the effect of the width of thick disk on diametrical moment of inertia, as well as the enhanced coefficient of bending stiffness of interference-fit part between disk and shaft, is included in the motion equations of thick-disk rotor, which are established based on finite element method, and the natural frequencies of rotor are obtained by solving the motion equations. Then the modal analysis is performed to get the natural frequencies in ANSYS Workbench, in which the friction coefficient and interference fit are set to be the same as those of the finite element calculation method. At last the modal experiment is done to verify the accuracy of calculation and simulation. The results show that the calculation values using enhanced stiffness of assembly part are in good agreement with those of ANSYS Workbench and experiment, and the percent errors of the first natural frequency and the second natural frequency are down to about 0.32% and 0.83%, respectively.

Numerical buckling analysis for flat and cylindrical shells including through crack employing effective reproducing kernel meshfree modeling

Buckling behavior of flat and cylindrical shells including through-the-thickness crack (through crack) is examined employing an effective reproducing kernel (RK) meshfree method. The concept of convected coordinate system is adopted to deal with general curvilinear surfaces. Both field variables and shell geometry are approximated by RKs, which is conceptually same procedure with isoparametric Finite Element Method (FEM). Each node has five degrees of freedom (DOFs). The numerical integration of stiffness matrices is conducted by strain smoothing approaches. In the present study, a crack modeling is introduced into the curved shell geometry for analyzing cracked cylinder buckling problems effectively. The presented approach has an attractive feature, i.e., five DOFs cracked flat shell model is only required for analyzing three-dimensional (3D) cracked curved shell problems. The accuracy and effectiveness of the present method are critically examined through several numerical examples in which the obtained results are compared with reference solutions as well as with the results of commercial FEM package (ANSYS). Effects of the element types in the FEM computations are also examined by comparison of the results by linear and quadratic shell elements. The results shed light on the significant effects of considered configurations on buckling coefficients and mode shapes.

All-in-fiber method of generating orbital angular momentum with helically symmetric fibers.

An all-in-fiber method of generating orbital angular momentum (OAM) is proposed. A simple device composed with a section of helically symmetric fiber and another section of regular fiber is designed to convert input light to optical vortices. Finite element method calculation of first- and second-order OAM generation based on the coordinates transformation technique is taken to show that the eigenmodes of the helically symmetric fiber structures carry orbital and spin angular momentum. Simulation using the self-developed beam propagation method algorithm is also performed to verify the orbital angular momentum generation and evaluate the performance of the OAM generator.

Theoretical investigation of the enhancement factor for a single field emitter in close proximity to the counter electrode

Field emission of electrons enables the patterning process in field-emission scanning probe lithography. A nanotip mounted at an active cantilever is used as an electron field emitter. Since the field enhancement at the tip apex is crucial for the Fowler–Nordheim emission current, the electric field and its enhancement based on a finite-element method (FEM) calculation are studied. The influences of the tip radius, the tip opening angle, and the tip–sample distance are considered. The numerically obtained enhancement factor γp is compared to various models found in the literature. Only three of them agree with the FEM data well. For small ratios of tip–sample distance and tip radius, the data resemble a “hemisphere on a post” model, and for larger ratios, it is better modeled by a “hemiellipsoid on a plane” model despite its “hemisphere on a cone” shape.

FEM Calculations in Analysis of Steel Subsea Water Injection Flowlines Designing Process

Abstract The article describes the result of theoretical research aimed at assessing the loads and operating conditions of a Coiled Tubing pipeline injecting water, suspended to the mining platform of Lotos Petrobaltic. For this purpose, appropriate calculation models have been developed using the Finite Element Method (FEM), taking into account the nature of the analyzed object and its loads. The analyzes were carried out for two pipes (previously operated and newly proposed) differing in geometrical and strength parameters. The research was carried out for selected directions of load on the pipeline (originating from sea waves) and various variants of attaching the suspended pipeline to the mining platform.

Basilar membrane-inspired self-powered acoustic sensor enabled by highly sensitive multi tunable frequency band

Herein, we report a self-powered flexible piezoelectric acoustic sensor (f-PAS) inspired by basilar membrane in human cochlear. The f-PAS covered the voice frequency spectrum via the combination of its low quality (Q) factor and multi-resonant frequency tuning, exhibiting four to eight times higher sensitivity than the conventional condenser sensor. Our piezoelectric acoustic sensor with a thin membrane design produced sufficient output voltages by the distinct resonant movement of the Pb[Zr0.52Ti0.48]O3 (PZT) membrane under the minute acoustic sound stimuli. Multiple sensor channels were integrated in a single f-PAS chip with a size of 1.5 × 3 cm2, which acquire multi-tunable piezoelectric signals without any external power. A linear response of the resonance frequency of the curved piezoelectric membrane was theoretically investigated by a finite element method (FEM) calculation. Low Q factors from corresponding channels were achieved by optimal membrane thickness and channel length.

DETERMINATION OF THE RATIONAL GEOMETRICAL PARAMETERS OF PLATE TYPE ELEMENTS OF MAGNETIC MATRIX OF THE POLYGRADIENT SEPARATOR

Introduction. Polygradient magnetic separation has wide application in industry and in biomedicine. Working process in polygradient separators takes place in a matrix, magnetic elements of which create magnetic forces sufficient to remove small ferro- and paramagnetic inclusions. Problem. The influence of mutual arrangement of elements on character of distribution of magnetic field is not taken into account during calculation of characteristics of magnetic field in magnetic matrixes. It makes comparative analysis of matrixes of different configurations quite difficult. Fulfillment of comparative analysis of strength characteristics of magnetic fields of multicomponent matrixes of polygradient separators of various configurations requires further researches. Goal. To determine the dependence of the strength characteristics of the polygradient electromagnetic separator on the geometrical parameters of the plate type elements of the multicomponent matrix. Methodology . The finite element method for calculation of power characteristics of separator magnetic field, method of comparative analysis and simple search method for determination of rational geometric parameters of the matrix have been used during the solution of the paper problem. Results. Estimation of entire spectrum of force field in plane of working zones of investigated structures in two-dimensional location for determination of rational variants of polygradient matrixes has been done. The main stages of computational experiment are given. Method of comparative analysis of power characteristics of investigated variants of matrix structures with corresponding characteristics of basic version of separator for determination of rational geometrical variants of polygradient matrixes has been applied. By results of calculations the rational geometric parameters of polygradient matrix has been chosen. The characteristics of power magnetic fields in working gaps of matrixes of polygradient separator have been studied. It made possible to determine the rational structural variants of matrix on basis of parameter of effective area of working zone. Practical value. The results of research can be used in practice of design of electromagnetic separators with polygradient matrixes.

Application of field modeling and determination of parameters in electrical engineering education

PurposeThis paper aims to present application of electromagnetic field (EMF) modeling in the educational process of electrical engineering study. Special attention has been paid to determination of specific parameters and characteristics as a function of device design. The aim is to introduce to the students the great opportunities for study and optimization of system behavior, based on the modeling of EMF distribution.Design/methodology/approachIllustrative examples have been considered, in which the students have to model the EMF distribution in relatively simple devices, using both analytical field determination and finite element method (FEM) analysis. The task includes also the determination of capacitances, inductances, magnetic fluxes, energies and forces. The problem has to be solved for different values of geometry parameters and material properties of the device. Thus, students can examine specific relation between field distribution and changes of the design.FindingsThe modeling of EMF distribution for different geometry and material properties allows determination of key factors, significantly influencing the behavior and processes in the studied device, which is the basic element in the computer-aided design systems and it can be used in subsequent system optimization.Practical implicationsThe wide possibilities and advantages of the FEM simulations have been demonstrated in the modeling of EMF distribution and obtaining of device parameters. It enables students to significantly improve their knowledge in EMF theory and helps the future engineers to estimate the great advantages and possibilities for optimal device designing, which offer them the numerical simulation of electromagnetic processes.Originality/valueThis work illustrates possibilities, advantages and many years of author’s experience in application of EMF modeling in the teaching process in the study of electrical engineering specialties. The work problems presented have been solved analytically and on the basis of computer FEM simulations, which allows comparison of the opportunities and necessary efforts, offered by both kinds of methods.

Enhanced photon-extraction efficiency from InGaAs/GaAs quantum dots in deterministic photonic structures at 1.3 μm fabricated by in-situ electron-beam lithography

The main challenge in the development of non-classical light sources remains their brightness that limits the data transmission and processing rates as well as the realization of practical devices operating in the telecommunication range. To overcome this issue, we propose to utilize universal and flexible in-situ electron-beam lithography and hereby, we demonstrate a successful technology transfer to telecom wavelengths. As an example, we fabricate and characterize especially designed photonic structures with strain-engineered single InGaAs/GaAs quantum dots that are deterministically integrated into disc-shaped mesas. Utilizing this approach, an extraction efficiency into free-space (within a numerical aperture of 0.4) of (10±2) % has been experimentally obtained in the 1.3 μm wavelength range in agreement with finite-element method calculations. High-purity single-photon emission with g(2)(0)<0.01 from such deterministic structure has been demonstrated under quasi-resonant excitation.