Two-dimensional Finite Element Research Articles

Optimization design of Tubular Permanent Magnet Linear Generator based on entropy model for wave energy conversion

—The effective use of wave energy which has huge reserves is one of the ways to solve the climate problem and energy crisis. In this paper, a Tubular Permanent Magnet Linear Generator (TPMLG) is optimized by the combination of comprehensive sensitive parameters method and particle swarm optimization based on entropy model (EPSO). By introducing the information entropy model, the aggregation characteristics in the process of particle swarm search are accurately analyzed, which can effectively reduce the invalid iteration of particle swarm. Firstly, the main design parameters of TPMLG are designed using the basic initial principle of permanent magnet linear machines. Then, the two-dimensional parametric finite element analysis model of the TPMLG is established, and a comprehensive sensitivity index Sc is defined to calculate the sensitivity indices according to power density and thrust fluctuation. The strong sensitivity parameters are optimized Particle Swarm Optimization based on entropy model, and the Non-sensitivity parameters maintain the initial design values. Finally, an experimental prototype TPMLG was manufactured according to the optimized results. The speed of TPMLG was simulated by the universal testing machine MTS100kN, the experimental results show that the designed TPMLG can be effectively applied to the direct drive power take-off system.

Electromagnetic Behavior Simulation of REBCO Pancake Coils Considering REBCO Tape Rotation Under High Magnetic Field

Since the screening current induced in rare earth-barium-copper-oxide (REBCO) magnet generates an irregular magnetic field, a few screening current simulation methods have been proposed. For an insert REBCO magnet generating ultra-high magnetic field, a new screening current method has been proposed with consideration of the coil-deformation effect. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this paper, we have developed a new screening current method based on a partial element equivalent circuit (PEEC) model coupling with a two-dimensional stress finite element analysis to accurately the time-transient distribution of accurate screening current. In the presented method, the changes of self/mutual inductances are considered due to the coil deformation. As the simulation results, it was found that the coil deformation affected the screening current distribution. When considering the coil deformations, the screening current-induced fields to operating current are different for charging cycles. It is necessary to simulate the coil deformation to accurately estimate the screening current and the screening current-induced field.

Investigation of Rotor Topologies for Reducing Torque Ripple in Double-Layer IPMSMs for Automotive Applications

Interior permanent magnet synchronous motors (IPMSMs) are currently widely used for traction applications. However, the torque ripple in these motors needs to be reduced because it causes vibration and acoustic noise. Accordingly, this study first determined the guidelines for reducing the torque ripple of multilayer IPMSMs and then proposed a double-layer IPMSM with holes drilled in the rotor core. The torque ripple reduction for the proposed rotor structure was examined using two-dimensional finite element analysis and experiments with prototypes. The analytical results showed that, under maximum torque-per-ampere control, the torque ripple using the proposed model was suppressed by 54.8% compared with the reference model while limiting the average torque reduction to 3.6%. Moreover, multi-objective optimization based on the guidelines was performed. With the proposed structure, the torque characteristics at high and low currents were highly correlated, and a similar torque ripple reduction effect was obtained even at low current, which is frequently used in traction motors for automotive applications. Finally, optimization was performed for an IPMSM with other topologies, resulting in verification of the generalizability of the proposed method.

Electric field-assisted fused filament fabrication process for robust additive manufacturing in unconventional orientations

Fused filament fabrication (FFF) is one of the most widely used thermoplastic additive manufacturing techniques that have great potential for numerous applications. However, for more advanced additive manufacturing with unusual environments, such as in-space manufacturing, conventional FFF is limited by the lack of gravity and inconsistent nozzle standoff distance. Varying nozzle standoff distances in the FFF process typically result in problems with the adhesion of extruded material as well as dimensional and geometrical errors in the extruded material, which leads to a long setup time and a high failure rate. Conventional FFF typically needs continuous monitoring or human intervention to ensure successful printing. This paper innovated an electric field-assisted FFF (E-FFF) process for robust fabricating parts in unconventional printing orientations while eliminating the need for constant supervision and human intervention to maintain and adjust the z-height calibration. The E-FFF system integrates a high-voltage power supply with a conventional FFF printer to produce an electrostatic force between the nozzle and the build plate. The generated electrostatic force is capable of attracting the extruded molten polymer material towards the build plate even at larger z-heights of up to 1200 μm under unconventional printing orientations. The effectiveness of the E-FFF process was demonstrated by comparing the E-FFF and conventional FFF processes. The results affirm the assistance of gravitational force on conventional FFF processes in the normal printing orientation. The novel E-FFF process with robust printing capabilities in the vertical and reverse orientations enables much larger nozzle standoff distances than that of the conventional FFF process, which exhibits great potential to be used in the micro/zero-gravity environment in the future. A two-dimensional finite element simulation model is used to understand the effects of applied voltage on the E-FFF process and calculate the electric field intensity. The simulation results showed that the electric field intensity of E = 1.27 × 106 V/m is sufficient for successful printing in all demonstrated printing orientations.

Bridging Law Application to Fracture of Fiber Concrete Containing Oil Shale Ash

Concrete is a widely used material in various industries, including hazardous waste management. At the same time, its production creates a significant carbon footprint. Therefore, intensive research is being conducted to create more eco-friendly concrete, for example, partially replacing cement with by-products such as oil shale ash (OSA) or improving properties by adding dispersed fibers such as basalt fibers (BFs). The article consists of experimental testing of nine types of concrete and the modeling of crack propagation in bending. The basic trends of crack propagation in samples of concrete with OSA and BFs are simulated using a two-dimensional Finite Element (FE) model considering only material degradation on the opening crack surface and experimental data of three- and four-point bending tests. Crack propagation is modeled using the bridging law approach. A surrogate model for predicting the peak loading as a function of tensile strength and fracture work was created. An examination of the results of the FE model shows that the bilinear and nonlinear bridging law functions best describe the crack growth in the analyzed material. A comparison of experimental and modeled results showed that the length of the composite BF strongly affects the accuracy of the numerical model.

Smart Structures Innovations Using Robust Control Methods

This study’s goal is to utilize robust control theory to effectively mitigate structural oscillations in smart structures. While modeling the structures, two-dimensional finite elements are used to account for system uncertainty. Advanced control methods are used to completely reduce vibration. Complete vibration suppression is achieved using advanced control techniques. In comparison to traditional control approaches, Hinfinity techniques offer the benefit of being easily adaptable to issues with multivariate systems. It is challenging to simultaneously optimize robust performance and robust stabilization. One technique that approaches the goal of achieving robust performance in mitigating structural oscillations in smart structures is H-infinity control. H-infinity control empowers control designers by enabling them to utilize traditional loop-shaping techniques on the multi-variable frequency response. This approach enhances the robustness of the control system, allowing it to better handle uncertainties and disturbances while achieving desired performance objectives. By leveraging H-infinity control, control designers can effectively shape the system’s frequency response to enhance stability, tracking performance, disturbance rejection, and overall robustness.

The geoelectric field coast effect: Results from two dimensional finite element method and analytic solutions

The geoelectric fields induced during geomagnetic disturbances (GMD) may affect the normal operation of technological systems at the Earth’s surface. The non-uniform Earth conductivity structure, especially large lateral conductivity contrasts, can lead to the enhancement of geoelectric fields near boundaries such as a coastline. In this paper, we give an overview of the applicability of a two-dimensional finite element method (2D-FEM) for studying lateral variations of the Earth’s conductivity, which can be considered as one of magnetotelluric sounding forward modelling methods, including both the E and the H polarization cases. Then the spatial distribution of the geoelectric field near a continent-ocean boundary is calculated with different models. This is compared with analytic solutions for simple models to verify the accuracy of the FEM modelling, which is calculated by using the ANSOFT software. More realistic scenarios are then developed to emphasize the advantages of FEM. The factors influencing the coast effect are discussed. Results show that frequency, the shape of seafloor boundaries, and the depth of ocean have a significant impact on the geoelectric fields. Therefore, these factors should attract more attention when assessing risk for man-made conducting systems located within the coastal influence range.

Quintuple grids plasmonic refractive index sensor for organic gas sensing application

In this article, an optical refractive index (RI) nanosensor has been presented. The layout is arranged in a metal–insulator-metal (MIM) waveguide configuration with gold being the plasmonic metal. The waveguides are coupled with quintuple grids resonant cavity where the grids are uneven in length. The transmission spectral profile of the schematic is numerically analyzed employing the two-dimensional Finite Element Method (FEM) within the mid-infrared region (MIR). Moreover, the key structural parameters are optimized individually to realize the maximum performance of the schematic. The most optimal structure displays a high sensitivity of 4737.87 nm/RIU and a FOM of 9.37. Furthermore, the structure can be suitably used in applications such as sensing organic gas vapors and temperature. Due to the practicality of the applications and the simplicity of the schematic along with the higher longevity provided by gold, this device can replace complex structures effectively.

The screw-type electrothermomechanical converter as a source of multiphysical influence on the technological environment

In ensuring the reliability of electromechanical converters in harsh conditions, the problem of increasing the energy efficiency of their application through structural, functional, and thermal integration with the technological environment is present. Thus, the research aims to determine the conditions of the direct multiphysical impact of a screw-type electromechanical converter on the technological environment. The method used is based on determining the list of features of screw-type electromechanical converters using the Comsol Multiphysics software, and a combination of three-dimensional and two-dimensional finite element models limited to the rotor with the inclusion of blades in the computational domain. Two variants of forming an algorithm for the multiphysical impact on the technological environment were studied: local concentration of the impact in certain areas of the rotor and uniform distribution along the rotor surface of temperature, pressure, magnetic induction, and electric field strength. The regularities of the distribution of magnetic induction on the outer surface of the ferromagnetic rotor at different azimuthal locations of the frontal parts of adjacent stators have been established. The distribution of the normal component of the magnetic flux density at the contact with the process medium in the form of rutile product or ilmenite concentrate is determined. The consumed electric energy is distributed in the stator tooth zone and the zone of electromagnetic field penetration into the rotor. Eddy currents are concentrated at the penetration depth from the rotor’s inner surface, with the penetration depth depending on the thermal state and sliding mode. The electric field intensity on the rotor’s outer surface reaches 0.8 V/m in the areas opposite the stator crowns and depends on the current activity of the phases at a given moment. Controlling the thermal and speed regime of the rotor can be used to create conditions for bioenergy stimulation on its surface in places of contact with the medium or to support the process of electrode heating of the technological medium. The adequacy of the mathematical models proposed for numerical modelling to the experimental data of the prototype of the screw electromechanical converter was confirmed, with deviations not exceeding 9.5%. The obtained results can be used to predict the optimal indicators of electromagnetic and heat transfer processes in screw electromechanical converters associated with the technological environment

Experimental and Numerical Flexural–Torsional Performance of Thin-Walled Open-Ended Steel Vertical Pile Foundations Subjected to Lateral Loads

This research investigates the effects of torsional moments on the mechanical behavior of thin-walled open-ended vertical pile foundations subjected to lateral wind loads. The aim of this research is to determine and quantify the errors using traditional design methods and provide more effective alternatives. The warping and torsion effect generated over the piles due to the resultant lateral load impact outside the shear center is analyzed in field tests. Complementarily, a two-dimensional finite element model based on the simple bending stress–strain state, as well as a three-dimensional finite element model considering torsional effects, were implemented and their results analyzed. Finally, a comparative analysis between the in-field lateral loading tests and the finite element model approaches was established by comparing load–displacement curves and using a non-linear Wrinkle model of the soil. Additionally, correlations between the experimental and finite element model errors for the cross-sections pile with a different torsional constant and torsional susceptibility index are shown. From the results, it has been ascertained that the slender thin-walled open-ended pile foundations are particularly sensitive to small load deviations from their center of gravity; this leads to the fact that the slenderer the load and the greater its eccentricity, the more it affects the torsion and warping of the pile. Calculation methodologies usually consider a simple in-plane bending behavior, which leads to errors between 44 and 58% in comparison with the experimental results obtained.

Analysis of the adhesively bonded composite double cantilever beam specimen with emphasis on bondline constraint, adherend through-thickness flexibility and fracture process zone relative size

ABSTRACT The double cantilever beam (DCB) specimen is widely used to characterise the mode I fracture of adhesive joints. This paper analyses some particular characteristics of adhesively bonded composite DCB specimens which could affect test results. Three-dimensional (3D) and two-dimensional (2D) finite element analyses (FEA) were conducted in order to evaluate the effects bondline constraint and adherend through-thickness flexibility on the specimen response. Since beam theory-based data reduction schemes are widespread, beam models were also employed to analyze the effects of adherend through-thickness flexibility and fracture process zone relative size. It is shown that, although composite adherends are usually thinner and have much lower transverse moduli than metal adherends, the level of bondline constraint is similarly high. This may: limit the level of adhesive plastic deformations in the fracture process zone; generate high bondline tractions that increase the likelihood of interface failure and interlaminar damage in the composite adherends. The present analyses also show relevant effects of adherend through-thickness flexibility in the adhesive elastic loading stage. Finally, smaller fracture process zones relative to metal adherend DCB specimens were predicted by a beam cohesive zone model. This may explain lower fracture energy values reported with composite adherends in some studies.

Geo-investigation and Slope Stability Analysis of Debris Slides along Ramban-Gool Road Network, Jammu and Kashmir, India

Abstract The prevalent landslides in the Kashmir Himalaya are the result of a combination of several geo-environmental parameters in a precarious terrain and extensive developmental activities. The Ramban-Gool road network is one of the landslide prone regions in the valley which has witnessed a constant increase in the landslides, damaging the public property apart from creating major threat to human life and geo-environment. Keeping in view the peril of slope failures, stability assessment of a few vulnerable slopes was carried out along with geological and geotechnical investigation. The stability analysis was carried out using two-dimensional numerical simulation tool limit equilibrium method (LEM) and finite element method (FEM) in both dry and saturated conditions. The results obtained from the study have very clearly demarcated the stability of the slopes in terms of factor of safety. The factor of safety obtained revealed that except for two slopes having factor of safety marginally greater than 1, the other four slopes have factor of safety less than 1 under dry condition indicating unstable condition. The factor of safety further decreases for all the slopes under saturated condition. Furthermore, results obtained from both LEM and FEM show a close approximation with values varying from 1.33 to 0.75 in case of LEM analysis while FEM values vary from 1.31 to 0.76. From FEM analysis, total displacement was also determined for each slope to assess the extent of potential damage.

Numerical Simulation of Pore Pressure Change Caused by Hydrocarbon Generation in Chezhen Sag and Its Influence on Hydrocarbon Accumulation

The pore fluid pressure is important for the generation, migration, and accumulation of hydrocarbons. The Chezhen Sag region in the Bohai Bay Basin is typically characterized by pore fluid overpressure, which is the difference between the pore fluid pressure and the hydrostatic pore pressure. The formation mechanisms of pore overpressure and the accumulation regularity of the “upper source-lower reservoir” type in this region remain unknown. In order to investigate these problems, based on the existing seismic, logging data, and regional tectonic stress environment, we established a two-dimensional finite element model to simulate the fluid–solid coupling processes in the Chegu 25 block of the Chezhen depression. We calculated the abnormal overpressure generated at the source rock during hydrocarbon generation and the processes of hydrocarbon migration and accumulation along the faults and analyzed the dynamic conditions of the hydrocarbon downward accumulation. The results showed that overpressure could accelerate the migration of hydrocarbon and improve the efficiency of hydrocarbon accumulation. When the overpressure was too large, tensile fractures and shear fractures could occur, resulting in hydrocarbon dissipation, and changing the results of the oil and gas accumulation. The overpressure at the source rock was mainly caused by hydrocarbon generation, while the overpressure at the reservoir was primarily created by unbalanced compaction. As the dominant channel of hydrocarbon migration that exists, overpressure will change the direction and path of hydrocarbon migration in the fault. Therefore, the high permeability of the fault and the existence of pore fluid overpressure can explain the “upper source-lower reservoir” hydrocarbon accumulation model strongly explained the high permeability of faults and the presence of overpressure. The simulated overpressure results were also in good agreement with the mud weight equivalent overpressure and the drill stem tests (DSTs).

CLASSIM: A relational database driven crop model interface

Crop models are valuable tools for examining the interactions of cultivar characteristics, environment, and management practices, and how they affect crop growth and development. The difficulty in finding all the data needed to set up a simulation can often deter potential users from utilizing a crop model. Model interfaces are necessary to make these complex tools accessible to end-users who may lack the expertise needed to work with the models directly, but who would benefit from the information generated by the models. As crop models vary in terms of input and output structures, there is no one universally compatible interface, so different crop model suites require their own interface. CLASSIM is a graphical user interface (GUI) for a suite of models developed by USDA-ARS. The interface provides a simplified tool to assemble input data for a model simulation. Web access to online databases for soil and weather data simplifies finding site-related data. The user is guided step by step to build the necessary input files. A database structure facilitates data entry, storage, and retrieval. The use of Structured Query Language (SQL) for data retrieval allows for advanced analysis and visualization outside of the interface. We describe the features of the GUI and provide examples of various operations. Model outputs are provided in tables and graphs to allow for visualization and analysis. Two-dimensional contour plots of soil processes are provided to visualize output from the two-dimensional finite element soil model. CLASSIM also allows users to set up single- and multiple-season runs for maize, cotton, soybean, potato, and fallow treatments, and is expected to be expanded to more crops in the future. A user-friendly GUI is essential for making simulation tools accessible to the broad range of researchers and practitioners working to solve the agricultural system challenges.

Artificial neural network-based investigation on high-speed train-induced embankment vibration in frozen regions

High-speed trains (HSTs) induce vibrations that deteriorate the embankments of ballastless tracks, particularly in frozen regions, necessitating vibration assessments for existing high-speed railways (HSRs). This study developed an indirect thermal-dynamic coupled two-dimensional (2D) finite element (FE) model to investigate the dynamic responses of the embankment of ballastless tracks to various subgrades and subsoils, train speeds, and frost depths in frozen regions. The results indicate that subgrade is the key parameter to analysing the dynamic response of the train–track–ground system considering train speeds. A fast and high-accuracy prediction method for the vibration responses was developed using an artificial neural network (ANN) and used to predict the vibration level under different conditions. Prediction results determined train speeds under 400 km/h safe for HSRs. This study can improve knowledge of ballastless track substructure design and extend the applicability of the current railway code to higher train speed conditions in frozen regions.

Effect of a gap on the open hole tension strength of carbon fiber reinforced plastic laminates

Tensile tests of quasi-isotropic laminates with a circular open hole, which include a gap in the hole area, were conducted to demonstrate the effect of the gap on the strength. The test showed that the reduction in the open-hole strength owing to the gap was less significant than that in the no-hole tensile strength. A two-dimensional mechanical model of quasi-isotropic laminates with an arbitrary inclined gap was proposed and analytically solved to obtain a closed-form expression for the stress concentration. An approximate expression was provided as the sum of the global uniform stress field and the local stress field near the open hole, which was solved based on a complex variable method. The present analytical solution agrees well with the corresponding two-dimensional finite element solutions. The solution indicated that the stress increase owing to the gap is limited at the stress concentration area. The analytical results were consistent with the experimental results.

On seismic isolation of soil-meta-foundation-structure systems

Meta-materials are engineered composites with physical properties that can introduce frequency band gap regions suitable for wave manipulation and filtering. This study investigates the seismic behavior of soil–structure systems with a meta-foundation designed using alternatively repeated layers of concrete and rubber. First, the frequency band gaps of the meta-foundation were derived using the Floquet-Bloch theory. The frequency band gaps for different meta-foundation configurations with infinite and finite numbers of unit cells were presented. Then, a two-dimensional (2D) plane-strain finite element simulation was proposed to study the isolation performance of meta-foundations on or embedded in soil half-space. Finally, two four-story steel structures with different dynamic characteristics were modeled under different input motions. The results show that direct embedment of meta-foundations in soil may break periodicity, requiring special treatments on the side boundaries of the foundation. Moreover, the numerical results show considerably enhanced structural performance for the meta-foundation system with a reduction up to 95.1% and 97.9% for the maximum horizontal acceleration and inter-story drift, respectively, compared to the non-isolated system. The results also indicate enhanced soil response under the meta-foundation and acceptable structural performance outside the band gap frequencies compared to the non-isolated system.

Numerical approaches in simulating Trichel pulse characteristics in point-plane configuration

In this work, a detailed comparison is made of a few different approaches to numerical modeling of non-equilibrium gas discharge plasmas in dry ambient air at atmospheric conditions, leading to Trichel pulse discharge. Simulation models are based on a two-dimensional axisymmetric finite element discretization of point-plane geometry. The negative corona discharge and the hydrodynamic approximation for generic ionic species (electrons, positive and negative ions) are used. The models account for the drift, diffusion, and reactions of the species. They comprise continuity equations coupled to Poisson’s equation for the electric field. Three different formulations were used to specify the ionic reaction rate coefficients. In the first one, the reaction coefficients are approximated by the analytical expressions as a function of the electric field intensity. Two others extract the reaction coefficients from the solution of the Boltzmann equation as a function of the reduced electric field or the electron energy. The effect of gas flow and heating on the pulse characteristics is also investigated. The accuracy of the models has been validated by comparing them with the experimental data.

Simulation of the 2016 Kumamoto Earthquakes Using the Finite Element Method with Concentrated Friction

In this paper, the process of simulating the occurrence of an earthquake on the fault plane for the 2016 Kumamoto, Japan earthquake is investigated dynamically using finite element methods. The two-dimensional finite element method is used by concentrating friction at the finite points. The used element is the elastic element, whose properties are determined based on the shear wave velocity and longitudinal wave. In order to verify the proposed method, the acceleration and velocity response spectra, Fourier spectrum, and other main parameters of the record obtained from the simulation were compared with the Kik-net data. From the obtained results, the role of displacement and velocity of its application to the fault plate in PGA can be pointed out, so that with a faster displacement of the fault plane, a larger PGA is expected. Friction and shear stiffness between the two fault planes and the dependence of friction on velocity are the main and influential factors in the characteristics of the produced earthquake. In high-frequency earthquakes, friction is dependent on velocity, and when friction is not dependent on velocity, static plays a major role, and no drastic changes in the response spectrum are observed.

Influence of mechanical characteristics of deep composite salt-gypsum layers on safe drilling of directional wells: a case study of Palaeogene in the Kuqa Piedmont structure, Tarim Basin, China

The directional wells can effectively improve the development efficiency of deep and ultra-deep pre-salt oil and gas reservoirs in the Kuqa Mountains of Tarim basin. Under the condition of deep temperature and pressure, the mechanical properties of the composite salt-gypsum layers are complex. During the directional drilling process, that the salt rock is easy to creep causes the drill stick. Under the condition of controlling the well inclination, it is difficult to choose the appropriate drilling fluid density to resist creep and thus maintain the stability of the wellbore. On the basis of rock mechanics experiments, this study established a two-dimensional finite element model considering the combination of composite salt-gypsum layers and inclined well with the effect of in-situ stress, analyzed the influence of temperature, differential stress and well deviation on the salt rock creep. The density of drilling fluid for preventing creep sticking is calculated, and a safe drilling fluid density chart for preventing creep shrinkage of composite salt-gypsum layers is compiled. The results show that when the differential stress is less than 10 MPa, the creep rate of the Tarim composite salt-gypsum layers are at least 10 times higher than that of the Gulf of Mexico salt layers; the creep rate increases with the increase of the differential stress and temperature, and the creep rate is an incremental curve; taking the highly deviated well in the Bozi area as an example, where the shrinkage ratio caused by sticking is set to be 5%, the drilling fluid density chart for creep resistance at 45° and 60° inclination is built, which is consistent with the actual drilling in the field. The results can provide design basis for the selection of anti-creep drilling fluid density in the directional wells in the Kuqa Piedmont composite salt-gypsum layers.