A new global finite element analysis of microwave circuits including lumped elements

This paper presents the stress analysis of the maxillary second premolar tooth under thermal loading as a result of hot/cold liquid in the mouth using the three-dimensional (3D) finite element method (FEM). The tooth was considered to be in a restored state with composite resin and amalgam on glass-ionomer as the base material. In the first step of the study, the temperature changes as a result of hot/cold liquid in the mouth were calculated. The thermal stress distributions owing to the temperature changes were then obtained. All calculation programs were prepared by the authors using FORTRAN 77. The tooth was assumed to be isotropic, homogeneous, elastic and unsymmetric. The distribution of temperature and stress were plotted for some critical points.

The coupling between lumped electronic circuits and electromagnetic fields is analysed in time domain by the finite element method (FEM) using edge elements. The classical solution of the vector electric field wave equation by Whitney-elements is modified to take into account the circuit elements. They are introduced in the FEM model by imposing that the current path of a circuit element coincides with an edge of the FEM mesh, so that the voltage drop across the lumped element coincides with the electric field circulation along the edge. In this way the imposition of the current-voltage characteristic of the lumped elements in the FEM equations is straightforward. The results obtained by the proposed method are compared with those obtained by Spice simulations. Copyright (C) 2000 John Wiley & Sons, Ltd.

The interaction between off-road tires and granular terrain has a great influence on the tractive performance of off-road vehicles. However, the finite element method or the discrete element method cannot effectively study the interaction between off-road tires and granular terrain. The three-dimensional combined finite element and discrete element method is applied to handle this problem. In this study, a calibrated finite element method–discrete element method model is established, in which the finite element model of off-road tire is validated by stiffness tests, while the discrete element model of gravel particles is validated by triaxial compression tests. The calibrated finite element method–discrete element method model can describe the structural mechanics of the off-road tire and the macroscopic mechanical properties of the gravel road. Tractive performance simulations of the off-road tire on gravel road under different slip conditions are performed with the commercial software LS-DYNA. The simulation results are basically corresponded with the soil-bin test results in terms of granular terrain deformation and tractive performance parameters versus the slip rates. Finally, the effects of tread pattern, wheel load, and tire inflation pressure on tractive performance of off-road tire on granular terrain are investigated. It indicates that the calibrated finite element method–discrete element method can be an effective tool for studying the tire–granular terrain interaction and predicting the tractive performance of off-road tire on granular terrain.

Isotropic consolidation test and consolidated-undrained triaxial test were first undertaken to obtain the parameters of the modified cam-clay (MCC) model and the behavior of natural clayey soil. Then, for the first time, numerical simulation of the two tests was performed by three-dimensional finite element method (FEM) using ABAQUS program. The consolidated-drained triaxial test was also simulated by FEM and compared with theoretical results of MCC model. Especially, the behaviors of MCC model during unloading and reloading were analyzed in detail by FEM. The analysis and comparison indicate that the MCC model is able to accurately describe many features of the mechanical behavior of the soil in isotropic consolidation test and consolidated-drained triaxial test. And the MCC model can well describe the variation of excess pore water pressure with the development of axial strain in consolidated-undrained triaxial test, but its ability to predict the relationship between axial strain and shear stress is relatively poor. The comparison also shows that FEM solutions of the MCC model are basically identical to the theoretical ones. In addition, Mandel-Cryer effect unable to be discovered by the conventional triaxial test in laboratories was disclosed by FEM. The analysis of unloading-reloading by FEM demonstrates that the MCC model disobeys the law of energy conservation under the cyclic loading condition if the elastic shear modulus is linearly pressure-dependent.

Verification of a three-dimensional unstructured finite element method using analytic and manufactured solutions

A simple structure formed by two metal patches symmetrically deposited at the two sides of the center microstrip is proposed and analyzed for blocking the higher order modes in a waveguide-packaged microstrip-line circuit. The variations (with the patch width) of the effective dielectric constants and field distributions of the modes in the packaged microstrip line with infinitely long side patches were first investigated using the two-dimensional (2-D) finite-element method (FEM) and the method of lines. The results suggested that there exists a range of patch widths at which the field distributions of the higher order modes are totally different from those of the microstrip line without side patches. The scattering of the patches as a function of the patch length and width was then studied using the three-dimensional (3-D) FEM with edge elements. It has been found that by simply choosing appropriate patch sizes, the parasitic higher order mode can be reflected without sacrificing the normal propagation of the dominant mode.

A three-dimensional FEM (finite element method) for solving elastic or viscoelastic wave propagation problems are tested. Viscoelastic wave equations are introduced by three relaxation mechanisms. Second-order polynomial interpolation function and perfectly matched layer (PML) absorbing boundary condition are composed to this FEM framework. Also, it performs effective CPU time reduction by parallel computing. The accuracy of the FEM is evaluated by three tests. FEM is compared to the analytical solution for Lamb’s problem and the semi-analytical solutions for layered elastic or viscoelastic media. Especially, FEM and the analytical solution for Lamb’s problem showed almost perfect convergence. Therefore, we conclude that FEM produces very exact waveform. Moreover, this conclusion can support the accuracy of FEM for viscoelastic wave equations.

The work presented here introduces lumped elements to an iterative method based on the wave concept combined with the two-dimentional fast Fourrier transformation algorithm known as fast modal transformation (FMT). We extend this method to the analysis of microwave-distributed circuits containing passive or active, linear or nonlinear lumped elements which are characterized by their surface impedance as defined in this article. Simulation results of varactor-tuned filter and phase-shifter circuit examples are compared with the measurement results. Good agreement between simulated and experimental results validates the use of the iterative method for the analysis of planar circuits, including lumped elements. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 269–275, 2003.

Numerical 3-D FEM simulation of tensor model for liquid crystal displays

In this paper we develop a leap-frog-type finite element method for modeling the electromagnetic wave propagation in metamaterials. The metamaterial model equations are represented by integrodifferential Maxwell's equations, which are quite challenging to analyze and solve in that we have to solve a coupled problem with different partial differential equations given in different material regions. Our method is based on a mixed finite element method using edge elements, which can easily handle the tangential continuity of the electric field. Stability analysis and optimal error estimate are carried out for the proposed scheme. The scheme is implemented and confirmed to obey the proved optimal convergence rate by using a smooth analytical solution. Then the scheme is extended to model wave propagation in heterogeneous media composed of metamaterials and free space, and extensive numerical results (using a rectangular edge element, a triangular edge element, and mixed edge elements) demonstrate the effectiveness of our algorithm for modeling the exotic backward wave propagation phenomenon in metamaterials. To the best of our knowledge, this is the first paper with an exhaustive simulation of backward wave propagation in metamaterials using time-domain finite element methods.

This paper presents an ultra- wideband (UWB) resonator and a bandpass filter (BPF) consisting of quasi- lumped elements using a microstrip line (MSL). First of all, a resonator using a high-impedance inductive line and a gap capacitor is examined by an electromagnetic simulator. The simulated results of the resonator show UWB bandpass characteristics with two controllable stop- bands by adjusting the element values and the length of the resonator. Secondly, an UWB-BPF using the presented resonator is proposed, fabricated, simulated and measured. It is confirmed that desired UWB bandpass characteristics are realized by controlling two stopband characteristics.

The goal of this paper is to present a best practice for deep water sub-salt wellbore stability analysis. Conventional one-dimensional analytical tools and three-dimensional nonlinear finite element method (FEM) software were used jointly in an integrated manner in which the former was used to predict pore pressure with logging data, and thus provides input data for FEM analysis. Numerical results of sub-salt wellbore stability analysis were presented for the Viosca Knoll field in the deepwaters of the Gulf of Mexico. To obtain accurate stress field information around the salt, it is necessary to begin by performing an analysis at the field scale. This analysis presents correct boundary conditions for wellbore stability analysis at the wellbore-section scale. Submodeling techniques were used to manage the field-to-reservoir scale discrepancy. A field model, 10 km in depth and width, was built, and a pan-cake-shaped salt body with a diameter of 7 km was embedded in the model. Trajectory optimization was performed once the vector distribution of principal stresses was provided. At the wellbore section scale, a submodel was built and the minimum safe mud-weight gradient was numerically predicted. A variation in the axial direction of the wellbore was performed to determine the optimized wellbore direction at the salt exit. The proposed integrated approach of jointly using conventional analytical tools with FEM software offers an effective method and best practice for deepwater sub-salt wellbore stability analysis.

Acoustic Emission (AE) technique is non-destructive Structural Health Monitoring (SHM) technique which has the potential to detect internal damages in real time. Literature reveals that researchers have used three-dimensional (3d) Finite Element Method (FEM) to predict AE waveforms in isotropic and single-layer anisotropic plates. However, the study to predict acoustic emission waveforms using FEM in layered composites and sandwich plates is limited in literature. Modelling of such layered plates is challenging as material properties may vary from one layer to another across the plate thickness. In this study, an effort has been made for two-dimensional finite element modelling for predicting AE waveforms in layered composites and sandwich plates using a generalised refined plate theory modelling. Numerical examples are first solved for isotropic and anisotropic plates and validated with the results obtained from 3d FEM. New results are presented for multilayered composites and sandwich plates.

Adopting a three-dimensional contact finite element method, with complex connecting rod group assembled body model of computation, the fatigue strength of the connecting rod of a certain type of diesel engine was verified. A transient stress analysis was conducted on the connecting rod. Compared with the connecting rod static stretching and compression test, the three-dimensional contact finite element method, which was used to analyze the strength of the connecting rod subassembly, was feasible. Based on the three-dimensional contact finite element method, the connecting rod transient stress analysis results showed that the maximum stress of the connecting rod did not occur under the highest pressure of the cylinder, and the dynamic stress value was less than the static stress value.

A new technique for the combination of electromagnetic field simulations and analysis of complex active circuits is proposed, allowing the incorporation of the passive metalization of active components into electromagnetic simulations.