Two-dimensional Finite Element Method Research Articles

Stability of Embankment Constructed on Soft Soil Treated with Soil–Cement Columns

The objective of this study was to investigate the effectiveness of soil–cement (SC) columns, provided either individually or in combination with lime columns, on the stability of embankment constructed on soft consolidating soil. The stability of the embankment was evaluated in terms of both the settlement and factor of safety at various time intervals during the consolidation. The effectiveness of columns was studied numerically using the two-dimensional plane strain finite element method. Settlement, excess pore water pressure and factor of safety were obtained at various time intervals. From the study, it was concluded that SC columns were effective in improving both the settlement and factor of safety of embankment throughout the consolidation of foundation soil. Provision of SC columns with lime columns was also effective in improving the stability of embankment. In addition, the stability of the embankment was affected by the arrangement of columns in the lime and SC composite system. The arrangement most effective to improve the settlement need not be the most effective system to improve the factor of safety after the construction of the embankment.

Investigation of an Outer Rotor In-Wheel Switched Reluctance Motor for Electric Vehicles by Finite Element Method

The demand of fossil fuel vehicles has decreased due to carbon emissions. Recently, electric vehicles (EV) with electric motor propulsion have gotten attention due to their zero carbon emissions and high efficiency. In this study, an outer rotor in wheel switched reluctance motor (IWSRM) with 18 poles on the stator and 24 poles on the rotor, designed for the propulsion of electric vehicles, is investigated in two-dimensional Finite Element Method (FEM). The magnetic field distributions of IWSRM for different rotor positions at nominal current are obtained. Then, the torque and phase inductance are calculated. As a result, the designed IWRSM provided low torque.

Non-reciprocal parity-time symmetry breaking based on magneto-optical and gain/loss double ring resonators

In this paper, we explore the operation of a nonreciprocal non-Hermitian system consisting of a lossy magneto-optical ring resonator coupled to another ring resonator with gain and loss, and we demonstrate that such a system can exhibit non-reciprocity-based broken parity-time (PT) symmetry and supports one-way exceptional points. The nonreciprocal PT-phase transition is analyzed with the use of both analytical tools based on coupled-mode theory and two-dimensional finite element method simulations. Our calculations show that the response of the system strongly depends on the regime of operation – broken or preserved PT-symmetry. This response is leveraged to show that the system can operate as an optical isolator or a one-way laser with functionality tuned by adjusting loss/gain in the second ring resonator. The proposed system can thus be promising for device applications such as magnetically or even optically switchable non-reciprocal devices and one-way micro-ring lasers.

A two-dimensional finite element approach to evaluate the sound transmission loss in perforated silencers

In this work, the two-dimensional finite element method approach is presented to evaluate sound transmission loss (TL) of perforated reactive silencers with holes uniformly distributed. In the hole domain, the sound pressure was described using a periodic positive square wave function to simplify the evaluation of sound waves in the azimuthal direction. Eight different models with perforated inner concentric tube are evaluated in terms of their TL. The proposed formulation results were verified using the traditional three-dimensional finite element method (FEM), showing good agreement. An additional verification was also performed using the three-dimensional FEM and the specific acoustic impedance of perforated inner concentric tube to couple the inner concentric duct with an expansion chamber. The periodic formulation and three-dimensional finite element analysis (FEA) used 4-node quadrilateral and 4-node tetrahedral elements, respectively. A final check was carried out with experimental analysis of 8 models and there was good agreement with results of the three numerical methods.

On the Use of Quadrilateral Meshes for Enhanced Analysis of Waveguide Devices with Manhattan-Type Geometry Cross-Sections

This work addresses the suitability of using structured meshes composed of quadrilateral finite elements, instead of the classical unstructured meshes made of triangular elements. These meshes are used in the modal analysis of waveguides with Manhattan-like cross-sections. For this problem, solved with the two-dimensional Finite Element Method, there are two main quality metrics: eigenvalue and eigenvector accuracy. The eigenvalue accuracy is first considered, showing how the proposed structured meshes are, given comparable densities, better, especially when dealing with waveguides presenting pairs of modes with the same cutoff frequency. The second metric is measured through a practical problem, which commonly appears in microwave engineering: discontinuity analysis. In this problem, for which the Mode-Matching technique is used, eigenvectors are needed to compute the coupling between the modes in the discontinuities, directly influencing the quality of the transmission and reflection parameters. In this case, it is found that the proposed analysis performs better given low-density meshes and mode counts, thus proving that quadrilateral-element structured meshes are more resilient than their triangular counterparts to higher-order eigenvectors.

Risk Assessment of Water Inrush in Coal Mine through Fault Based on Forchheimer and Non-Darcy Flows

Abstract Fault water inrush accident in coal mine construction is a serious hydrogeological disaster, which seriously endangers the safe operation of underground engineering. In the process of mining coal resources in Western China, a large number of serious mine water inrush accidents have occurred. Based on the investigation of geological conditions of fault in the Pingdingshan coal mine, the coupling model of the Darcy laminar flow and Brinkman flow is used to analyze the water inrush mechanism of a fault. On this basis, considering the higher permeability and water inrush rate, the Brinkman flow may not be used to simulate the nonlinear flow mechanism at the fault. Two improved models, the Brinkman equation and Forchheimer equation are used to analyze the mechanism of water inrush. Based on the two-dimensional finite element method, the process of water inrush into the water inrush zone is analyzed. The pressure and velocity nephogram under different conditions and the evolution characteristics of non-Darcy effect influence coefficient of fault water inrush are analyzed through parameter study. Based on the different permeability variation coefficients ξ (the ratio of fault permeability kF to aquifer constant permeability kA) and different fluid flow field changes, the Fletcher number and flow rate are compared with the theoretical data.

Analysis of methods and approaches of the electromagnetic calculation of induction machines regarding their use to solve multiphysical problems

PurposeFor the electromagnetic simulation of electrical machines, models with different ranges of values, levels of detail and accuracies are used. In this paper, numerical and two analytical models of an induction machine (IM) are analysed with respect to these aspects. The purpose of the paper is to use these analyses to discuss the suitability of the models for the simulation of various physical quantities of an IM.Design/methodology/approachAn exemplary IM is simulated using the two-dimensional numerical finite element method, an analytical harmonic wave model (HWM) and an extended HWM. The simulation results are analyzed among themselves in terms of their level of detail and accuracy. Furthermore, the results of operating map simulations are compared with measured operating maps of the exemplary machine, and the accuracy of the simulation approaches is discussed in the context of measurement deviations and uncertainties.FindingsThe difference in the accuracy of the machine models depends on the physical quantity of interest. Therefore, the choice of the simulation method depends on the nature of the problem and the expected range of results. For modeling global machine quantities, such as mean torque or losses, analytical methods such as the HWM s are sufficient in many applications because the simulation results are within the range of measurement accuracy of current measurement systems. Analytical methods are also suitable for local flux density curves under certain conditions. However, for the simulation of the influence of local physical effects on the machine behavior and of temporally highly resolved quantities in saturated operating points, the accuracy of the analytical models decreases and the use of the finite element method becomes necessary.Originality/valueIn this paper, an extension of the HWM is used to calculate the IM, which, in contrast to the HWM, models the saturation. Furthermore, the simulation results of the different electromagnetic IM models are put into the context of the uncertainty of a measurement of several identical IMs.

Spurious-free thickness-shear bulk acoustic resonators on lithium niobate using standard and broadband piston mode designs

This paper describes the design and fabrication of spurious-free thickness-shear bulk acoustic resonators (TSBARs) using the lithium niobate (LN) plate. Previously, the authors conjected from the experiment on the TSBAR that cut-off edges with crystal LN x plane serve as ideal reflectors for the piston mode operation, and complete suppression is possible by adding the standard piston mode design to the other edges normal to the X-axis. Following this conjecture, the traditional piston mode structure is designed by the traditional two-dimensional finite element method, and the TSBAR is fabricated following the design. The experiment showed complete suppression of the transverse mode resonances, and the conjecture was verified.

The Effects of Permanent Magnet Segmentations on Electromagnetic Performance in Ironless Brushless DC Motors

This paper investigates the electromagnetic torque by considering back electromagnetic force (back-EMF) trapezoidal degrees of ironless brushless DC (BLDC) motors through the two-dimensional finite element method (2-D FEM). First, the change percentages of the electromagnetic torque with back-EMF trapezoidal degrees, relative to those of PMs without segments, are investigated on the premise of the same back-EMF amplitude. It is found that both PM symmetrically and asymmetrically segmented types influence back-EMF trapezoidal degrees. Second, the corresponding electromagnetic torque, relative to that of PMs without segments, is studied in detail. The results show that the electromagnetic torque can be improved or deteriorated depending on whether the back-EMF trapezoidal degree is lower or higher than that of PMs without segments. Additionally, the electromagnetic torque can easily be improved by increasing the number of PMs’ symmetrical segments. In addition, the electromagnetic torque in PMs with asymmetrical segments is always higher than that of PMs without segments. Finally, two ironless PM BLDC motors with PMs symmetrically segmented into three segments and without segments are manufactured and tested. The experimental results show good agreement with those of the 2-D FEM method. This approach provides significant guidelines to electromagnetic torque improvement without much increase in manufacturing costs and process complexity.

Numerical Constraints on Folding and Thrusting in Jiudong Basin: Implication for the Northeastward Growth of Qinghai–Tibetan Plateau

Under regional tectonic shortening in the northern margin of Qinghai–Tibetan Plateau, the fold-and-thrust belts composed of four thrust faults (North Qilian-Shan, North Yumu-Shan, South Heli-Shan, and North Jintanan-Shan) formed from southwest to northeast discontinuously sequentially in the Jiudong Basin area during Late Cenozoic. Meanwhile, the North Qilian-Shan, Yumu-Shan, and Heli-Shan ranges were formed successively, as the Earth's local surface was unequally uplifted. In this study, based on geological and geophysical observations, a simple two-dimensional elastic-plastic numerical finite element method model for a southwest-northeast section in Jiudong Basin is successfully established to simulate the spatiotemporal evolution of the local fold-and-thrust belts. Results show that the computed equivalent plastic strain concentration zones and the four observed thrust faults are consistently correlated in spatial position orientation and time sequence. The simulated upper-surface deformation is congruent with the observed topographic peaks and uplift sequences of the North Qilian-Shan, Yumu-Shan, and Heli-Shan ranges. This study provides a geodynamic basis for understanding the growth mechanism of the northern margin of Qinghai–Tibetan Plateau under tectonic horizontal shortening. Also, we provide a thorough sensitivity analysis for the model parameters of this particular geologic setting. Our sensitivity simulations, considering systematic case variations about the regional geometrical-material parameters, suggest the manifestation of three different possible evolution patterns of fold-and-thrust belts for a wedge above a decollement layer, with wedge plastic deformation migrating from 1) thick to thin end (well-known), 2) thin to thick end, and 3) both ends to middle. Finally, our results suggest that in this region, further growth of mountain ranges is expected to continue in the future.

Mosaic Based Optimization of NRD Guide Devices Using Binary Evolutionary Approaches and 2D-FVFEM

In this paper, efficient optimal design approaches based on mosaic optimization concept are developed for NRD guide devices to realize the high-performance compact millimeter-wave integrated circuit. Binary representation-based genetic algorithm, differential evolution algorithm, harmony search algorithm, firefly algorithm, and particle swarm optimization are developed to efficiently optimize the pixel pattern in the design region of NRD guide devices. To demonstrate the usefulness of these population-based optimizations, a comparative study based on the problem-solving success rate is conducted first. To carry out this study, four NRD circuit components are designed which include low crosstalk waveguide crossing, T-branch power splitter, bending waveguide, and frequency demultiplexer. The proposed optimal devices achieve high transmission efficiencies greater than 99.9%, 49.9%:49.9%, 99.9% at 60 GHz and 96.4%, 98.5% at 59 GHz and 61 GHz. In addition, the same NRD guide components except frequency demultiplexer are also designed at wideband operation and achieve broad bandwidth around 5 GHz, 4 GHz, and 3 GHz. In order to improve the computational efficiency, the originally developed two-dimensional full vectorial finite element method is employed for the numerical simulations. This paper demonstrates the detailed implementation procedure of developed evolutionary approaches for the material distribution in the design region of NRD guide devices, comparative study of developed optimization approaches, and proposed highly attributed NRD circuit components for the realization of NRD based high-performance compact millimeter-wave circuit.

Screening current induced field characteristics of HTS quasi-isotropic and simply stacked strands in alternating magnetic field

The screening current induced field (SCIF) in the flat REBCO coated conductors so called the second generation high temperature superconducting tapes cause undesirable effects in multiple applications. Their existence reduces the spatial uniformity and temporal stability of magnetic fields for applications of superconducting magnets. In this paper, we numerically and experimentally investigate the characterization of the screening current and SCIF of quasi-isotropic strand (Q-IS) and simply stacked strand (SSS) under external alternating magnetic field with various amplitudes, orientations, and excitation rates. The two-dimensional finite element method based on T-A formulation is adopted for simulation, the Q-IS and SSS samples are fabricated for experiments. The field angle is in the range of 0°–90° at intervals of 15°, the excitation rate varies from 20 mT s−1 to 800 mT s−1. We display the distribution of screening current in both strands under various field amplitudes and orientations. Then the dependence of the SCIF on the amplitude and orientation of the external field is studied, respectively. The spatial distribution of SCIF of both strands with different amplitudes and angles of the external field are also discussed. Besides, we analyze the properties of SCIF under various excitation rates. As a result, the SCIF of Q-IS is much smaller and has quasi-isotropic distribution compared to SSS, which represents that Q-IS has a relative smaller screening effect. The spatial point with the largest SCIF of Q-IS locates at the corner of the strand and is independent of the external field, but the corresponding point in SSS varies with the angle and amplitude. The Q-IS is also less susceptible to the change of rate. Therefore, Q-IS has more advantages when the screening effect is considered in superconducting applications.

Ultra-power-dense heat exchanger development through genetic algorithm design and additive manufacturing

<h2>Summary</h2> This work presents the design, fabrication, and characterization of a three-dimensional heat exchanger (HX) having a tube-in-tube architecture using a genetic algorithm design and metal additive manufacturing (AM). The genetic algorithm aids the design of optimal fin geometries that minimize total thermal resistance between hot fluid and cold fluid. The genetic algorithm is coupled to a two-dimensional finite element method simulation to calculate conduction and convection in the device. Through careful thermal-hydraulic experiments, we demonstrate that our HX was able to achieve a power density of 26.6 W/cm³ and specific power of 15.7 kW/kg. The specific power of our additively manufactured device is 20X higher than that of a commercially available tube-in-tube HX with no fins. The optimized device also performs well compared with shell-and-tube and brazed plate heat exchangers that are designed for significantly higher heat transfer.

Contact Stresses and Dynamic Analysis of involute Spur Gear with FEM Approach

Abstract: This paper investigates the characteristics of a gear system including contact stresses, bending stresses, and the transmission errors of gears in mesh. The objective of this paper is to compare values of contact stress and dynamic analysis obtained by theoretical hertz equation with the ANSYS result. A two stage spur gear box has been designed for material handling application by manual calculation and then performs contact stress and dynamic Simulation to ensure its reliable working. The results of the two-dimensional Finite Element Method (FEM) analysis from ANSYS and theoretical results are well comparable. Keywords: involute, spur gear, contact stress, dynamic analysis, finite element analysis

Design of the Joint Motor for an Articulated Robot Considering Joint Load Characteristics

In this paper, we propose a method to efficiently design joint motors, which are the key elements that drive a cooperative robot. Designing joint motors with more power than the required capacity increases the volume and weight of the robot. On the other hand, designing joint motors with less power than the required capacity can lead to failure and safety accidents because of high temperature rise and mechanical instability. Therefore, in this study, the required capacities of the joint motors were determined through a dynamic analysis of the robot system and incorporated in the joint motor design specifications. An electromagnetic analysis was performed during design using the two-dimensional finite element method, and the detailed dimensions of the motor were determined using the response surface method, which is an optimal design technique. The thermal characteristics of the joint motor were evaluated using a thermal equivalent circuit. The designed joint motors were manufactured, and their performance were tested not only at the component level, but also at the robot system level to verify experimentally the validity and usefulness of the proposed joint motor design method.

Displacement Measurements and Numerical Analysis of Long-Term Rock Slope Deformation at Higashi-Shikagoe Limestone Quarry, Japan

The Higashi-Shikagoe limestone quarry is an open-pit mine situated in Hokkaido Prefecture, Japan, that has experienced four slope failure incidents since 1996. The rock slope behaviour has been monitored since the first failure event by measuring the rock slope surface displacement using an automated polar system. Recent measurements have revealed a gradual decrease of the distance between the beam generator and mirrors over time; however, the displacements and decrease rate differs between the centre and left- and right-hand sides of the quarry. This implies that the deformation characteristics of the rock slope and factors influencing the slope deformation differ at the centre and left- and right-hand sides of the quarry. In this study, the two-dimensional finite element method was used to identify the causes of slope deformation by investigating the effects of limestone excavation at the foot of the rock slope, the deterioration of a ∼70 m-thick clay layer at the rock slope foot wall, and shear failure owing to rainfall infiltration. The numerical results show that slope deformation on the left-hand side and centre of the quarry are induced by clay deterioration, whereas the right-hand side of the quarry is deformed owing to floor excavation and/or shear sliding. The rock slope is presently stable because the magnitude of the rate of displacement decrease is small and no acceleration is observed.

Torque ripples reduction in a synchronous reluctance motor by rotor parameters optimization

PurposeHigh torque ripple is the significant challenge of the synchronous reluctance machine in household electric appliances, electric vehicles and so on. This paper aims to present an optimized design of a synchronous reluctance rotor structure to reduce the torque ripple with improving the average torque by the particle swarm optimization (PSO) algorithm.Design/methodology/approachThe optimization of rotor geometries has been investigated. Most of the rotor parameters such as the width of iron parts, the width of barriers along d and q axes and the endpoint angle of barriers are optimized by a new method using the PSO algorithm. After optimization, the resulted optimum design along with the initial design is simulated by two-dimensional finite element method and results are compared. At the end, a prototype is constructed and tested. Results of the experiment are compared with the simulation results where acceptable adoption is yielded.FindingsMinimizing the torque ripple without losing the average torque is an important achievement of the synchronous reluctance motor (SynRM) optimization; furthermore, the finite element analysis and experimental results indicate that the torque ripple of the SynRM with the optimized rotor is reduced significantly. Also, increasing the number of optimization parameters can effectively obtain an accurate shape of the SynRM barrier.Originality/valueBecause of the high number of parameters in synchronous reluctance rotors, the majority of proposed optimizations did not use all geometric parameters of the rotor and tried to simplify the optimization by ignoring several optimization parameters or reducing the number of flux barriers. In this optimization, most of the rotor parameters have been used to achieve the precise barrier shape with the aim of reducing the torque ripple in SynRM.

Field simulation of settlement analysis for shallow foundation using cone penetration data

This paper deals with the settlement analysis of a vertically loaded strip footing by the use of two-dimensional random field finite element method. Total settlement and rotation of the footing have been calculated by elasto-plastic solution in finite element model. Deformation modulus of soil Ed was assigned conforming to 2D Gaussian random field using Karhunen–Loéve series expansion. Spatial variability of Ed was represented by the horizontal and vertical correlation lengths (θvE and θhE). CPTu database from Adapazari, Turkey has been employed to estimate the correlation lengths. Soil profile was modelled with 4 layers in accordance with random field from in-situ test results, and correlation lengths were assigned to each different layer. Random field realizations were produced by MATLAB code, and probability density functions (PDF) of maximum total settlement and rotation of the footing were constructed using Monte Carlo Simulations by iterative solutions of each realization with finite element analysis. Probabilities of failure (Pf) by settlement and rotation were calculated from PDFs. Initially, the analysis was carried out using average values of each horizontal and vertical correlation lengths that were assigned to every soil layer. Subsequently, analyses were iterated with maximum and minimum values of the correlation lengths in order that both the effect of horizontal and vertical spatial variability can be considered. 1000 calculations were performed for the 5 analysis models, with 200 random field realizations for each model. The effect of varying θvE and θhE on total settlement and rotation of the footing has also been investigated.

FINITE ELEMENT ANALYSIS OF SHADED POLE MOTOR BASED ON MAXWELL2D

Shaded pole induction motor is one of the simplest and least expensive types of single-phase motors, but one of the most difficult to analyze. In this paper, we adopted a two-dimensional finite element method 2DFEM, which is one of the most accurate methods to analyze such motors. We used Ansys Maxwell2D software with assist of AutoCAD software in modeling and analyzing a reluctance-augmented shaded pole motor. The 2DFEM results of torques and currents for this motor obtained from Maxwell2D were compared with the analytical results and appeared a good agreement.

Debonding Failure Analysis of Reinforced Concrete Beams Strengthened with CFRP Plates.

In this study, experimental work was carried out on reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymers (CFRP) plates. This study aims to examine the effect of the reinforcement ratio on the flexural behavior of these beams and propose a new model for predicting the debonding moment. Six RC beams consisting of three control beams and three beams strengthened with CFRP plates were tested. The beams were simply supported and loaded with four-point bending. The test variable was the tensile reinforcement ratio (1%, 1.5%, and 2.5%). Analytical prediction using the fiber element method was also carried out to obtain the complete theoretical response of the beam due to flexural loads. The test results show that the reinforcement ratio affected the bending performance of RC beams with CFRP plates. Following this, the experimental data from 60 beam test results from published literature and this study were analyzed. From these data, it was found that the ratio of tensile reinforcement, the ratio of modulus of elasticity of concrete, the modulus of elasticity of the plate, and plate thickness all affect the value of debonding moment. A parametric study using fiber elements and the two-dimensional finite element method was also carried out to confirm the effect of these variables on debonding failure. These variables were then used to develop an equation to predict the debonding moment of RC beams strengthened with CFRP plates, using simple statistical analysis. This analysis resulted in a simple model for predicting the debonding moment. Then the model is entered into a computer program, and the complete response of the cross-section due to debonding failure can be obtained.