Finite Element Method Method Research Articles

Nonlinear seismic response and damage evolution of a mountain tunnel: Multi-scale simulation by IBEM-FEM coupled method

Studying dynamic response and damage assessment of mountain tunnels is paramount in earthquake engineering. This paper proposed a novel method, the indirect boundary element method-finite element method (IBEM-FEM) coupled method, aimed to concurrently simulate the amplification effect of kilometer-scale mountain topography and the damage evolution in a centimeter-scale lining tunnel section. The proposed method involves two fundamental steps. Initially, the input motion on the truncation boundary within the mountain is accurately determined using the indirect boundary element method (IBEM). Subsequently, the nonlinear dynamic behavior of the tunnel structure and its adjacent area is analyzed by the finite element method (FEM) based on the results from the previous step. This study numerically simulates the seismic damage and failure mechanisms of a mountain tunnel considering three influence factors: incident wave types, incident wave intensities, and surrounding rock mass grades. The results indicate that mountain topography amplifies the seismic response, thereby affecting the dynamic behavior of the tunnel. Under the incidence of SV-waves and P-waves, the dynamic damage distribution patterns of the tunnel lining are significantly different. Moreover, as seismic wave intensity increases, the peak values of tunnel stress exhibit a non-monotonic increasing trend. The surrounding rock mass grade also significantly affects the dynamic response and damage distribution of the mountain tunnel. Overall, the proposed IBEM-FEM coupled method can effectively consider complex mountain topography and is applicable for evaluating the nonlinear seismic response of mountain tunnels.

The Lateral Behavior of Large-Diameter Monopiles for Offshore Wind Turbines Based on the p-y Curve and Solid FEM Methods

With the rapid increase in offshore wind turbines in China, monopiles with diameters exceeding 2 m are widely used. As these piles are subjected to lateral loads caused by wind, waves, and currents, the designs of the pile foundations supporting the offshore wind turbines are significantly influenced by their lateral behaviors. For this reason, field tests of the largest monopile on the sea and additional analysis based on the solid finite element method (FEM) and p-y curves are carried out to reveal the response of monopiles subjected to lateral loads and to figure out key technical issues related to the design process. The results revealed that the p-y curves proposed by the API code for clay showed a much “softer” response, which resulted in the conservative design of the piles. The solid FEM relied heavily on the choosing of the parameters used. At relatively small deflections, the solid FEM presented reasonable results as compared with the tests which were, however, supposed to overestimate the ultimate capacity of the piles. The results also indicated the importance of the influence of the pile–soil gap and the application of parameter analysis to achieve relatively conservative results, if the solid FEM is adopted in the design.

Identification of damage in steel beam by natural frequency using ANNS models

Beams have played a significant role in engineering applications and they have been commonly used for modelling civil problems. In fact, different models and methods have been developed to identify the damage to the beams. In this paper, the artificial neural network (ANN) model was developed to predict the location, width and depth of the saw-cut of steel beams by the change of natural frequencies. The natural frequencies of a steel beam in different scenarios were identified by the Finite Element Method (FEM). In order to validate the accuracy of FEM model, the natural frequencies of the steel beam in the case of no saw-cut determined by this model were compared with those determined by the Frequency Domain Decomposition (FDD) method. The results indicated that, the combination of FEM method, FDD method and ANN model would have great significance in structure health monitoring.

Tunable Helmholtz Resonators Using Multiple Necks.

One of the uses of Helmholtz resonators is as sound absorbers for room acoustic applications, especially for the low frequency range. Their efficiency is centered around their resonance frequency which mainly depends on elements of their geometry such as the resonator volume and neck dimensions. Incorporating additional necks on the body of a Helmholtz resonator (depending on whether they are open or closed) has been found to alter the resulting resonance frequency. For this study, tunable Helmholtz resonators to multiple resonance frequencies, are proposed and investigated utilizing additional necks. The resonance frequencies of various multi-neck Helmholtz resonators are first modeled with the use of the finite element method (FEM), then calculated with the use of an analytical approach and the results of the two approaches are finally compared. The results of this study show that Helmholtz resonators with multiple resonances at desired frequencies are achievable with the use of additional necks, while FEM and analytical methods can be used for the estimation of the resonance frequencies. Analytical and FEM approach results show a good agreement in cases of small number of additional necks, while the increasing differences in cases of higher neck additions, were attributed to the change in effective length of the necks as demonstrated by FEM. The proposed approach can be useful for tunable sound absorbers for room acoustics applications according to the needs of a space. Also, this approach can be applied in cases of additional tunable air resonances of acoustic instruments (e.g., string instruments).

Combined FEM and phase field method for reliability design of forward degradation in SiC bipolar device

The reliability of 4H-SiC bipolar devices is compromised by the expansion of single Shockley stacking faults (SSFs) during forward-current operation. Because SSF expansion is governed by multiphysical aspects, including electrical, thermal, and stress states, analysis of the mounted structure is important for improving power module design. We propose a practical design method that analyzes the critical condition due to SSF expansion using a combined method with a multiphysical finite element method (FEM) and phase field model based on the time-dependent Ginzburg–Landau equation. In preliminary studies, the thermal deformation of the demonstration module and the variation of threshold current of a bar-shaped SSF were verified from experimental and reference data. Estimating the SSF expansion rate on the constructed response surface under the mutiphysical inputs from FEM, the proposed design method can be used effectively in the design process by changing the various design variables.

Effect Analysis of Demagnetization of Permanent Magnet Synchronous Motor for Electric Drilling Tool on Air-gap Flux Density

Electric drilling tools have been developed in the field of drilling because of their high efficiency. As the core component of electric drilling tool, permanent magnet synchronous motor(PMSM) provides power for drilling tool. However, in the process of drilling, the permanent magnet of PMSM will appear demagnetization.The value of air-gap flux density affects the performance and efficiency of the motor directly. Demagnetization faults are divided into uniform demagnetization and local demagnetization.In order to study the influence of demagnetization of PMSM on the air-gap flux density, mechanism of permanent magnet is analyzed Firstly, and then establishing numerical model with analytical method. Finally, simulation motor demagnetization using finite element method(FEM) based on Maxwell. No-load and load operating state are analyzed under the two fault modes are considered in this paper, and compared with the healthy state of the motor. The analytical results show that when the demagnetization fault occurs in the motor permanent magnet, the air-gap flux density will decrease accordingly.The FEM method results show that with the increase of uniform demagnetization rate, the flux density of the air-gap almost decreases in proportion to the increase of demagnetization rate. The demagnetization of single pole permanent magnet has little effect on the magnetic density of the nearby permanent magnet, but it will lead to the imbalance of the whole electromagnetic field of the motor. The air-gap flux density can be used as a characteristic index to judge the fault of demagnetization.

Deep learning-based prediction of delamination growth in composite structures: bayesian optimization and hyperparameter refinement

Abstract In this study, a novel method for detecting the growth of delamination in sandwich structures has been proposed. To this end, we suggested hybridizing the Deep Learning techniques (DL) and Finite Element Method (FEM) for predicting the growth of delamination in this structures. A dataset of simulated delamination growth under different delamination sizes has been produced using the FEM method. Then, a DL model has been trained using this dataset to precisely predict the growth of delamination. This study focused on predicting delamination growth using a tuned and optimized deep learning based regressor. Therefore, to find the ideal set of hyperparameters, the Bayesian optimization algorithm has been used for selecting the best structure and enhancing the regressor performance. Afterward, the model was evaluated and multiple processes were conducted to improve its behavior and solve its stability and overfitting issues. Particularly, an inconsistency between validation loss and training loss has been initially detected in the behaviour of the model, which may indicate overfitting. To tackle this issue, dropout regularization has been added, which improved the consistency between the loss functions but results in less smooth convergence from the expectations. So, in a third study, dropout and L1 regularization has been combined to improve the stability of the model. This combination achieved a consistent and smooth convergence between the validation and training loss functions. The findings highlight the importance of hyperparameter optimization and regularization techniques in improving regression model performance. The study shows the efficiency of Bayesian optimization in hyperparameter tuning and the iterative optimization of a regression model. Furthermore, the outcomes show that the suggested method can identify and predict delamination growth with high accuracy.

A new variant of the fem for evaluation the strenght of structures of complex geometry with heterogeneous material structure

Structures are known to feature a complex geometry and a complex material structure which varies depending on their functional purpose, technological capabilities and design. The finite difference method, collocation method, variational method, theoretical and experimental method, finite element method, among other methods, are employed to calculate the stress-strain state (SST) of structures of complex geometry. The finite element method (FEM) has become the most common one of them all. The spline version of the finite element method (SV FEM) has proven to be an effective FEM method used to calculate the SST of structures of complex geometry. Unlike the conventional FEM method, a preliminary parametrization of the entire area of complex geometry using the parameters outlined by the canonical domain and a cubic approximation of the desired variables within each element yields consistent finite elements. The unbroken geometric continuity maintained between the elements along with the continuity of the desired quantities and their first derivatives along the line of contact of the elements makes it possible to obtain reliable results with just a small number of partitions into finite elements. One should note the application of the basics of the spline version of the finite element method in two-dimensional SV FEM-2 and three-dimensional SV FEM-3 arrangements. One should also make mention of the idea of producing a synthesized version of SV FEM. Two-dimensional and three-dimensional elements being synthesized into one element would usher in a new phase in the development of the SV FEM approach which would describe the complex structures of construction materials in addition to complex geometry. SV FEM has made it possible to evaluate the SST of structural elements of complex geometry along with the thin layers that penetrate it in all three directions. The versions of SV FEM that are available now serve to assess the SST of a broad range of various thin-walled and non-thin-walled structures of complex geometry, including multilayer structures with thin layers in all three directions, with hard and soft coatings along the edges and with local defects on the surfaces of structures. This paper presents a number of SST calculations of specific structures that have been carried out via the FEM versions described above.

A comparison of countermeasures against landslide on the road No.152, Sapa Town, Lao Cai Province, Vietnam

Landslide hazards are one of the most common geological disasters due to the impacts of natural factors, mainly rainfall, and human activities, such as the construction of transport infrastructure and mining projects. In Vietnam, most of the landslides and slippage frequently occur in mountainous areas, especially in Lao Cai province during the rainy season. In 2021, a slope failure happened near the Mong Hoa valley, on Road No. 152, sections Km 2+728.26–Km 2+827.04 in Cau May ward, Sapa town, Lao Cai province. In this study, topographical features, geomorphological features, hydrological features, geological investigation, and laboratory tests were performed to analyse the slope stability. This study used the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM) to analyse the slope stability, and several countermeasures were proposed for this slope such as the retaining wall, ground anchors, and soil nails. This numerical result showed that the ground anchors and soil nails are the suitable method to prevent the instability of the slope. This study shows that compared with the traditional LEM method and advanced FEM method is that it can capture more results not only safety factor but also horizontal displacement and load anchor result. As a result, this analysis showed that the safety factor value in the finite element method was greater than that in the limit equilibrium method.

Numerical Simulation of Electrical Properties of Carbonate Reservoirs Using Digital Rocks

Rock electrical experiments are essential means of researching the conductive properties of rocks and are fundamental to interpreting resistivity logging. Carbonate rocks have more complex pore structures than sandstone, which results in more complex conductive properties. However, conducting experiments on representative rock samples from carbonate reservoirs is difficult, making it challenging to study the micro factors affecting electrical properties. Therefore, researching the conductive properties of carbonate rocks is difficult. To address this, in this paper, three-dimensional (3D) digital rock models with different porosities are generated, and conductive simulations are carried out on these models using the finite element method (FEM). Firstly, a micro-computed tomography (μ-CT) 3D image of a carbonate rock is obtained. Secondly, mathematical morphology-based methods are used on the μ-CT image to generate cores with varying porosities and fluid distributions. Then, the electrical properties are simulated using the FEM method, and the results are analyzed. The results reveal that the formation factor of the reservoir is mainly influenced by the shape and structure of the pores. The Archie equation is more suitable for carbonate reservoirs with water saturation levels greater than 60%. The wettability of the rock can alter the distribution of fluid in the reservoir space under different water saturation conditions. In pure water-wet rocks, the water phase mainly occupies small pores, while the oil phase occupies larger pores. As a result, compared to pure oil-wet rocks, water-wet rocks have more conductive channels and better conductivity. Therefore, it is important to determine the wettability of the rock when calculating water saturation using the Archie equation. The saturation index value of water-wet carbonate rock is about 2, while that of oil-wet rock is around 3–4. This research lays a foundation for studying the electrical conductivity of carbonate reservoirs using digital rocks.

Topology Optimization of a Femoral Stem in Titanium and Carbon to Reduce Stress Shielding with the FEM Method

Arthroplasty is commonly performed to treat advanced osteoarthritis or other degenerative joint conditions; however, it can also be considered for young patients with severe joint damage that significantly limits their functionality and quality of life. Young patients are still at risk of aseptic mobilization and bone resorption due to the phenomenon of stress shielding that causes an uneven distribution of tensions along the femoral contact surface prosthesis. This phenomenon can be limited by choosing the material of the prosthesis appropriately or by varying its stiffness, making sure that its mechanical behavior simulates that of the femur as much as possible. The aim of this study is to evaluate the mechanical strength of a prosthesis optimized both in shape and material and compare the results with a standard titanium prosthesis. Methods: Through three-dimensional modeling and the use of finite element method (FEM) software such as ANSYS, the mechanical behavior of traditional prosthesis and prosthesis optimized topologically respecting the ASTM F2996-13 standard. Results: With topological optimization, there is a stress reduction from 987 MPa to 810 MPa with a mass reduction of 30%. When carbon fiber is used, it is possible to further reduce stress to 509 MPa. Conclusions: The reduction in stress on the femoral stem allows an optimal distribution of the load on the cortical bone, thus decreasing the problem of stress shielding.

Numerical investigation of structural models equipped with tuned liquid damper

Tuned liquid dampers (TLDs) are introduced in structural systems to suppress vibration of the structure due to dynamic actions. Using a grid-based Finite Volume Method-Finite Element Method (FVM/FEM), efficiency of TLDs of cylindrical and rectangular geometries was evaluated by performing a two-way Fluid-Structure Interaction (FSI) analysis. The nonlinear sloshing response of fluid was simulated by employing a three-dimensional Navier–Stokes equation as the governing equation and occurrence of wave breaking was accounted by using Volume of Fluid (VOF) method for free surface tracking. Utilizing the developed numerical model, a series of three-dimensional transient analysis were conducted on a structure with and without TLDs aiming to investigate effect of base excitation amplitude. The result show that maximum performance of TLDs at resonance is obtained when the forcing ratio is limited to 0.1, and for this case, both cylindrical and rectangular TLDs displayed comparable efficiency. Effect of excitation frequency fe was also investigated under a wide range of the forcing ratio showing that as fe increases, the natural frequency of coupled TLD-structural system approaches the natural frequency of un-damped structural system.

State of art on FEM approach in inverse heat transfer problems for different materials

The present study investigates the utilisation of the Finite Element Method (FEM) in addressing Inverse Heat Transfer issues associated with diverse materials. The Finite Element Method (FEM) is a widely utilised methodology in engineering design that effectively tackles thermal problems and heat transfer. The versatility of this technology transcends the domain of engineering and has been found to have practical applications in various fields such as biomedical science, aerospace, and chemistry. The Finite Element Method (FEM) has demonstrated its proficiency in addressing inverse heat transfer problems that are linked to a variety of materials, each of which has unique characteristics. The following discourse proceeds to conduct a thorough analysis of the application of the Finite Element Method (FEM) in resolving inverse heat transfer predicaments with a view to achieving optimal results. The present paper expounds upon the inherent benefits and drawbacks associated with the utilisation of finite element techniques for the purpose of resolving inverse heat transfer problems. Furthermore, the present study examines the pragmatic implementation of the Finite Element Method (FEM) in addressing heat transfer issues in diverse fields, such as Boiler design, Heat exchanger design, Cooling tower design, and Nuclear reactor design. The paper offers tangible illustrations of how the FEM method can be utilised to tackle practical heat transfer difficulties by emphasising these particular applications. This paper provides a contribution to the comprehension of the effectiveness of the Finite Element Method when addressing inverse heat transfer problems. The aforementioned statement highlights the adaptability of this methodology in managing diverse substances with distinct characteristics and furnishes discernment into its benefits and drawbacks. Moreover, the article elucidates the multifarious implementations of the Finite Element Method (FEM) in the domain of thermal energy transfer, providing pragmatic exemplars of its efficacy in areas such as the design of boilers, heat exchangers, cooling towers, and nuclear reactors.

Mechanical effect of reconstructed shapes of autologous ossicles on middle ear acoustic transmission.

Conductive hearing loss is caused by a variety of defects, such as chronic otitis media, osteosclerosis, and malformation of the ossicles. In such cases, the defective bones of the middle ear are often surgically reconstructed using artificial ossicles to increase the hearing ability. However, in some cases, the surgical procedure does not result in increased hearing, especially in a difficult case, for example, when only the footplate of the stapes remains and all of the other bones are destroyed. Herein, the appropriate shapes of the reconstructed autologous ossicles, which are suitable for various types of middle-ear defects, can be determined by adopting an updating calculation based on a method that combines numerical prediction of the vibroacoustic transmission and optimization. In this study, the vibroacoustic transmission characteristics were calculated for bone models of the human middle ear by using the finite element method (FEM), after which Bayesian optimization (BO) was applied. The effect of the shape of artificial autologous ossicles on the acoustic transmission characteristics of the middle ear was investigated with the combined FEM and BO method. The results suggested that the volume of the artificial autologous ossicles especially has a great influence on the numerically obtained hearing levels.

Application and optimization of an artificial neural network to forecast thermo-mechanical behaviour of HLE steel under weld spot effect

The reliability of assembled structures is significantly influenced by the applied thermomechanical stresses and the robustness degree of the simulation numerical methods. The utilization of classical numerical methods such as the finite element method (FEM), extended finite element method XFEM, and mean weighted residuals method are computational costs due to the complexity of the materials behaviour laws, physicals mathematical model and laboratory apparatus cost. To ensure accurate investigation techniques, it should be performed a numerical model used for resolving welding physical equations governed. The main objective of this study is to architect and optimize an intelligent model based on an artificial neural network to resolve a complex model of the calculation effect of spot welding on the behaviour of HLE steel. The ANN model gives a strong correlation between the dataset as numeric input and the target. The artificial neuron network gives a proxy model approach to exploit input data and results extracted by simulation of weld spot using finite element method FEM. The performance evaluation of the ANN model was carried out using mean square error and regression analysis. As a result, the present model ANN gives with minimum computational cost a good match of temperature estimating, equivalent stress and strain along the contact area of two thin plates of steel studied assembled by weld spot with a comparison between classical models using FEM.

Diffusion - Convection Equation of Galactic Cosmic Rays (GCR) in the Atmosphere and Its Analytical, Numerical Solutions by Using Finite Elements Method Using Parker Transport Equation

This study depicts that to find the Analytical and numerical solutions of Diffusion – Convections Equations of Galactic Cosmic Rays (GCRs) by Finite Element method (FEM) and also to find the Energy Equation of GCRs by using a part of Parker’s transport equation. This considers moreover centres on the exactness and acknowledgment of the FEM strategy by utilizing dissemination blunder, scattering mistake and add up to blunder investigation. The comes about are depicted both graphically and in a unthinkable frame, which essentially guarantees the method’s legitimacy and the algorithm’s proficiency to maintain the exactness, effortlessness, and nonlinear Convection-Diffusion Equation conditions. The proposed method may be connected for tackling any nonlinear convection diffusion equation. We concentrate on assaying the confluence and stability of the nonlinear parabolic partial differential equation. This study focuses on the delicacy and acceptance of FEM method by exercising dispersion error dissipation error, and total error analysis.

Progress in FEM modeling on mechanical and electromechanical properties of carbon nanotube cement-based composites

Abstract Carbon nanotubes (CNTs) reinforced cementitious composite (CNRC) with excellent electrical and self-sensing properties, which enables it to serve as an intrinsic sensor for structural health monitoring (SHM). However, the requirements of modern industry for accurate calculation and performance design of engineering materials are not met by traditional experimental studies alone. The finite element method (FEM) has the advantages of simplicity of operation, accuracy, and cost-effectiveness, and it has been widely used in the property verification and prediction of various composite materials. In this article, the constitutive model, FEM modeling method, and simulation process of CNRC along with existing model types, innate relations, and model parameters are reviewed, and the corresponding mechanical, electrical, and electromechanical coupling properties of CNRC under different parameters are systematically analyzed by FEM method. By combining different uncertainty parameters and model types, the advantages and disadvantages of FEM for mechanical, electromechanical coupling, and SHM applications of CNRC modeling are explored. The results are in good agreement with those in the existing CNRC experiment, which effectively proves the reliability of the FEM method in CNRC research. This work is important to develop a sound theoretical model verification and performance prediction for early applications in SHM of CNRC.

TEMGYM Advanced – NanoMi lens characterisation

A complete analysis including finite element method (FEM) calculation, focal length properties, and thirdorder geometric aberrations of the open-source electrostatic lens from the NanoMi project is presented. The analysis is carried out by the software TEMGYM Advanced, a free package developed to carry out ray-tracing and lens characterisation in Python. Previously TEMGYM Advanced has shown how to analyse the aberrations of analytical lens fields; this paper expands upon this work to demonstrate how to apply a suitable fitting method to discrete lens fields obtained via FEM methods so that the aberrations of real lens designs can be calculated. Each software platform used in this paper is freely available in the community and creates a free and viable alternative to commercial lens design packages.

Numerical analysis and experimental measurement on segmented ring transducer acoustic fields

In order to overcome the shortcomings of the two traditional methods of finite element method (FEM) and direct coupling of mechanical FEM and acoustic boundary element method (BEM) in the comprehensive simulation of acoustic characteristics of non-two-dimensional axisymmetrical transducers, the acoustic FEM and acoustic BEM coupling method is adopted in this study to model, calculate and analyze the three-dimensional (3D) model of the segmented ring transducer. Firstly, the basic theory of FEM, BEM and FEM-BEM coupling calculation of the transducer is introduced. Secondly, a 1/8 3D model of the segmented ring transducer is built to simulate the underwater electro-acoustic characteristics of the transducer. Finally, a transducer prototype is manufactured according to the numerical model, and the electro-acoustic performance of the transducer is measured in the anechoic tank. The numerical results of transmission voltage response (TVR), admittance and radiation directivity curves are in good agreement with the experimentally measured results, which indicate that the proposed method is correct and effective. Therefore, the method could be used to comprehensively calculate the acoustic characteristics of the segmented ring transducer. In addition, the method could be used not only to study the acoustic problems of other transducers or transducers arrays with complex structures that are non-two-dimensional axisymmetrical, but also to comprehensively analyze and predict the near-field and far-field acoustic characteristics of any transducers including two-dimensional (2D) axisymmetrical transducers.

Development of Calculation Technique for FEM Thermal Simulation Using Virtual Fluid Elements

In recent years, CAE (Computer-aided engineering) using FEM (Finite element method) simulations were generally used in the design field. FEM simulations were classified as static implicit and explicit dynamics methods. Particularly FEM simulations using the static implicit method were very generally and usefully used in the industrial world. The static implicit method FEM consists of static, buckling, thermal, vibration analyses, and so on. This FEM thermal analysis can't calculate the phenomena of heat transfer and internal forced cooling in some enclosures of a machine tool. On the other hand, when the temperature distributions in a structure such as that are calculated, FVM fluid simulation was used for that. However, this simulation can't exactly calculate a complex structure in a machine tool, needs very long calculation times and the calculation accuracy is very poor. Therefore, in this research, the calculation technique regarding FEM thermal simulation using 4 virtual fluid elements was developed and evaluated for the phenomena of heat build-up and internal forced cooling in some enclosures of a machine tool. The algorithms and the calculation models regarding 4 virtual fluid elements were developed, then the proposed method was evaluated in the experiment. It is concluded from the results that; (1) the 4 virtual fluid elements were developed for FEM thermal simulation instead of FVM fluid simulation, (2) FEM thermal simulation with the developed 4 virtual fluid elements has high calculation accuracy and a short calculation time, (3) the proposed method was very effective in the design.