FEM Approach Research Articles

IGA Approximations of Elastic Interfaces and their Defects in an Elastic Medium with Couple Stress

The objective of this work is to develop and implement a computational algorithm for calculating stress and couple-stress fields induced by bulk and interfacial line defects such as dislocations and generalized disclinations within phase/grain boundaries. The thermodynamic driving forces on line and planar defects, responsible for coupled plasticity and interface motion, fully coupled to stress, couple-stress and applied boundary conditions are also computed. A continuum approach for small deformations is considered following the formulation outlined in Acharya and Fressengeas (Continuum mechanics of the interaction of phase boundaries and dislocations in solids. In: Differential Geometry and Continuum Mechanics, pages 123–165, 2015), extended herein in the thermodynamics to accommodate physically necessary ingredients that arose in the modeling in Zhang and Acharya (J Mech Phys Solids 119:188–223, 2018), Zhang et al. (J Mech Phys Solids 114:258–302, 2018). Constitutive relations are derived from kinematics, balance laws and from the use of the second law of thermodynamics in global form. One of the challenges presented by this approach is the inclusion of couple stresses, Toupin (Arch Rational Mech Anal 17(2):85–112, 1964), and the consequent treatment of 4th order systems arising from the equations of balances of linear and angular momentum. In order to deal with these equations, the classical FEM approach is replaced by iso-geometric analysis (IGA), as proposed by Hughes et al. (Comput Methods Appl Mech Eng 194(39):4135–4195, 2005). Results on stress and couple stress fields of the various defects involved are computed. Further, the coupling of the dislocation density with the eigenwall allows for the capturing of the shear parallel to the grain boundary, which has been observed experimentally and through molecular dynamics.

Computational study of time-fractional non-linear Kawahara equations using Quintic B-spline and Galerkin’s method

This study presents two numerical methods focused on Quintic B-spline (QBS) and Galerkin finite element method (GFEM) for solving time-fractional Kawahara equations. The QBS is utilized as both the basis and test function in the FEM approach. We apply Caputo formula with quadrature rule for evaluation of temporal fractional part. The QBS and GFEM formulation are used to approximate the space functions and their derivatives. Furthermore, a four-point Gauss Legendre quadrature is employed to evaluate the source term in the GFEM. The efficiency and accuracy of the proposed scheme are evaluated using the E2 and E∞ norms. Additionally, Fourier stability analysis is conducted, and it is revealed that the method exhibits unconditional stability. The results, presented in the form of tables and graphs to demonstrate the effectiveness of the scheme.

Electrophoretic deposition of LiFePO4 and carbon black: A numerical study to explore longitudinal trends using Taguchi design

Developing Electrophoretic Deposition (EPD) for Composite Structural Batteries (CSBs) could revolutionise energy storage technology. CSBs offer an innovative solution by seamlessly integrating batteries into structures and effectively reducing weight and space constraints. Despite its successful implementation across various fields, EPD method still lacks comprehensive understanding of the underlying physical and chemical processes due to the number of variables involved. In this study the effects of key parameters associated with the process are investigated with a coupled FEM and analytical approach to find correlations with the deposition process. A Taguchi Design of Experiment with five parameters, namely voltage, concentration, relative weight ratio of LiFePO4 – carbon black particles, length and perimeter of the electrodes is implemented to identify the correlations with mass deposited, thickness of the coating and yield rate when LiFePO4 and Carbon Black particles in ethanol suspension are used. In order to capture the variation over time, each parameter is studied at six different time of deposition. A concentration that optimises yield rate resulting in thickness and mass deposition is identified. The resistivity of the suspension dictates the yield rate dynamics, allowing it to be designed within a specific range to meet requirements of different applications.

Characterization of the dynamic forces transmitted to the support of a railway track, due to the roughness of wheels and rails - 3D finite element approach

Among the causes of railway vibrations, rail and wheel roughness is recognized as a major contribution. The excitation mechanism at work when rough wheels run on rough rails can be assimilated to a prescribed relative displacement between the wheels and the rails. This article deals with the modeling of this wheel/rail interaction phenomenon, using a 3D FEM approach. The input excitation data is the combined wheel / rail roughness spectrum, while the sought output is the spectrum of dynamic forces transmitted to the support. Characterization of these dynamic forces can be used, for instance, to assess the anti-vibration performance of a track. The presented approach overcomes the limitations of 2D or analytical approaches commonly encountered in dynamic studies of railway tracks: (a) It takes advantage of the finite element modeling flexibility, compared to analytical approaches, which are developed for specific configurations. (b) It can account for the infrastructure's dynamic flexibility, whether it is invariant in the longitudinal direction or not. (c) It can account for the 3D dynamic behavior of the track. As an illustration, the method is applied to a floating slab track, thereby showing the importance of the transverse modal behavior of the track in this case.

Structural Response Analysis and Comfort Evaluation of Residential Buildings: A Combined Wind Tunnel and FEM Approach

With global urbanization accelerating, high-rise buildings have become a common feature in the urban landscape, especially in coastal cities, where they encounter unique wind-load challenges. This study aims to quantify the structural response and occupant comfort of a high-rise residential building under wind-induced accelerations by integrating wind tunnel testing with finite element analysis (FEA). The research focuses on critical response parameters, including displacement, acceleration, and stress, to evaluate the building’s performance. Wind tunnel tests provided detailed wind pressure distribution data across the building’s surface, while multi-degree-of-freedom and finite element models facilitated precise numerical simulations. The findings highlight a significant directional and temporal variability in wind-load responses, with the most pronounced effects observed at a wind-direction angle of 105° relative to the building’s front-facing axis (0°). The study confirms that the combined application of wind tunnel tests and FEA offers a comprehensive approach to understanding wind-induced responses, essential for the scientifically accurate and effective design of high-rise structures.

Specifics of Experimental and Fem Approaches in Structural Integrity Assesment of Penstock Made of HSLA Steel

Taking into account the history of problems concerning high-strength low-alloyed (HSLA) steel used for manufacturing of penstocks (partly presented by authors in previous studies), this paper is oriented toward specifics on structural integrity assessment of construction in question. Experimental testing of parent material, i.e. HSLA steel, such as microstructure analysis, impact toughness testing and hardness measuring provide insight into characteristics of parent material properties. Considering geometry of penstock and specific requirements, finite element method (FEM), i.e. ABAQUS, was used to assess the structural integrity of penstock as a whole, specific the longitudinal welded joint under the different internal (working) pressure. It should be emphasized that a slight undermatching effect was investigated by FEM approach in this case. Focus is being put on plastic deformation investigation on aforementioned welded joint under maximum internal pressure of 120 bar.

Lid driven flow and heat transfer due to various positions of slit in a square cavity: FEM approach

A detailed analysis of flow and heat transfer due to moving slit within the various positions of the square cavity is discussed. The slit is strategically positioned and examined at three distinct locations within the square cavity i.e. left, middle and right. Constraints of the square cavity are defined for horizontal and vertical walls. The top horizontal wall is considered to be adiabatic while the other three walls of the cavity are cold. The upper surface of slit is heated and movable towards the left side of the square cavity while the other three walls are immovable and cold. The fluid flow dynamics and heat transfer within the enclosed cavity are governed by fundamental principles of mass, momentum and energy conservation. These governing principles manifest as intricate mathematical equations, specifically nonlinear partial differential equations accompanied with boundary conditions. The key parameters under consideration include the Reynolds number (250≤Re≤1500) and Richardson number (0.01≤Ri≤5) at a fixed Prandtl number (Pr=6.2). These parameters are analysed through variations in velocities, temperature profiles, isotherms and streamlines. In the computational framework, the momentum and temperature equations are addressed through quadratic interpolation, while linear interpolation is applied to handle the pressure equation. The numerical solution, utilizing Newton's technique and the PARADISO solver, is rigorously validated against existing research methodologies, establishing its methodological reliability. Higher Reynolds numbers shift the primary vortex towards the middle and create corner recirculation zones, more uniform heat distribution, while higher Richardson numbers increase buoyancy forces, reducing isotherm contours and affecting heat distribution. The local Nusselt number increases with the increase in Reynolds numbers but shows small changes with the increase in Richardson number. The value of Nusselt number decreases as the position of slit changes from left to right.

CutFEM-based MEG forward modeling improves source separability and sensitivity to quasi-radial sources: A somatosensory group study.

Source analysis of magnetoencephalography (MEG) data requires the computation of the magnetic fields induced by current sources in the brain. This so-called MEG forward problem includes an accurate estimation of the volume conduction effects in the human head. Here, we introduce the Cut finite element method (CutFEM) for the MEG forward problem. CutFEM's meshing process imposes fewer restrictions on tissue anatomy than tetrahedral meshes while being able to mesh curved geometries contrary to hexahedral meshing. To evaluate the new approach, we compare CutFEM with a boundary element method (BEM) that distinguishes three tissue compartments and a 6-compartment hexahedral FEM in an n = 19 group study of somatosensory evoked fields (SEF). The neural generators of the 20 ms post-stimulus SEF components (M20) are reconstructed using both an unregularized and a regularized inversion approach. Changing the forward model resulted in reconstruction differences of about 1 centimeter in location and considerable differences in orientation. The tested 6-compartment FEM approaches significantly increase the goodness of fit to the measured data compared with the 3-compartment BEM. They also demonstrate higher quasi-radial contributions for sources below the gyral crowns. Furthermore, CutFEM improves source separability compared with both other approaches. We conclude that head models with 6 compartments rather than 3 and the new CutFEM approach are valuable additions to MEG source reconstruction, in particular for sources that are predominantly radial.

Do foreign investment, human development index, labor, and poverty influence economic growth in Indonesia?

Economic growth is one of the primary indicators of a country's success in improving the welfare of its people. In Indonesia, the dynamics of economic growth are highly complex and intriguing to study. This research aims to assess the impact of foreign investment, the human development index, labor, and poverty levels on economic growth in Indonesia. The method employed is a quantitative approach using data from 34 provinces in Indonesia between 2020 and 2022, obtained from the official BPS website. The analysis was conducted using panel data. The findings, using the FEM approach, indicate that individually, foreign investment, the human development index, and labor positively contribute to economic growth, while poverty does not have a significant impact. Overall, foreign investment, the human development index, labor, and poverty collectively influence economic growth in Indonesia. Therefore, the government should enhance economic growth by increasing foreign investment through stable policies, investing in education and healthcare, and ensuring a skilled workforce that meets market demand.

Granular Pile Settlement Prediction on Varying Soil Strata: FEM Approach

Granular Pile Settlement Prediction on Varying Soil Strata: FEM Approach

Verification and validation of a coupled CFD–FEM approach with overset structured grid through free decay and regular wave tests

This paper presents a comprehensive verification and validation study applied to the hydrodynamic analysis of a semi-submersible Floating Offshore Wind Turbine (FOWT) platform. The numerical simulation is conducted using a coupled Computational Fluid Dynamics-Finite Element Method (CFD–FEM) approach. The CFD program incorporates an overset grid interpolation method, facilitating a more systematic grid refinement in the estimation of discretization uncertainties. A mooring analysis program, based on the FEM scheme, is integrated with the CFD program to simulate the dynamic responses of mooring system. The necessity of the nonlinear mooring model is demonstrated by comparing solutions with a comparative test using a linear mooring model. The verification study, based on a least-squares-based extrapolation method, quantifies the spatial and temporal discretization errors of the numerical model. The numerical solutions based on the baseline model are further validated against the model test measurements. A pitch free decay model test and a regular wave model test conducted within the OC5 project are utilized for the verification and validation study. Results from both tests demonstrate the reliability and accuracy of the coupled method.

A systematic approach to obtain optimized low-cost balsa wood structure subjected to the effects of uncertainties: A FEM approach

A systematic approach to obtain optimized low-cost balsa wood structure subjected to the effects of uncertainties: A FEM approach

Thermal-structural Modeling of power electronic package: effects of deposition geometry and dry spot on the stress distributions

A Power Electronics package is a heterogeneous system made of semiconductor devices (dies), metallic-ceramic substrate, baseplate and encapsulating material.The electronic devices can be MOSFETs (Metal Oxide Semiconductors Field Effect Transistors), diodes, IGBTs (Insulated Gate Bipolar Transistors) and passive components such as capacitors, resistors and sensors integrated on support circuit; the complete set of semiconductor devices installed on a package form the so-called “power modulus”.These devices play an important role in the transmission and conversion of energy in electric and hybrid vehicles. Due to the elevated currents and, consequently, the elevated temperatures at which these systems work, and due to the mismatch of the thermal-mechanical properties of the materials from which they are made, stresses and strains develop within the devices.Such stresses can be locally concentrated and amplified, depending on the deposition geometry of the various layers constituting the semiconductor device. Edge termination structures are essential to decrease the electric field at die’s edges, and, including brittle compounds in their composition, like Si3N4 or SiO, they are quite sensitive to mechanical stress.Another reason that may cause the stresses concentrations is the presence of dry spots. Dry spots are areas of various size, located at the interface between die or leadframe and the encapsulating resin, where there is a total or partial lack of adhesion.The aims of this work are, mainly, two. At first, four linear finite element analyses have been performed in order to evaluate the stresses concentrations at the corners of edge termination structure.The first case concerns sharp corners and the other cases concern differently filleted corners. In the second part of this work, it has been analysed the dry spot effect on stress distributions. Due to the small size of the defect with respect to the whole package, a Global-Local FEM approach has been used, creating a local subdomain where the mesh is denser than the global domain and a running a further separate numerical analysis which takes its boundary conditions from the global analysis, so delivering reliable small-scale stress and strain gradients. This approach permits to achieve accurate analyses focused on zones of interest of the global domain, limiting the increase of the computational cost of the modelling.

Comparison of Machinability of Al-4.5%Cu/TiB2/3p MMC for Multi-Layer Coated Insert: Validated FEM and Statistical Approaches

Aluminum-based Metal Matrix Composites (MMC) are commonly used in metal-cutting applications due to their better mechanical and physical properties, such as high strength, hardness, and low weight. Also, modern coating applications, especially multi-layer coated tools, have the cutting-edge potential for relieving the difficulties of machining MMCs to improve insert performances. Therefore, this study aimed to reveal the turning Al-4.5%Cu/TiB2/3p performance of the multi-layer coated cemented carbide insert with verified FEM and statistical approaches. Different coating materials, two and three of which were soft and hard, were appointed at different thicknesses and sequences in the design of experimentally calibrated simulations. The Grey Relation Analysis (GRA) was set to investigate the multi-layer coated insert performance for turning the MMC concerning the resultant cutting forces (FR) and maximum insert temperature (Tmax). The optimal multi-layered coating was found at levels 4-2-4-3-2 for the factors of coating materials: tungsten disulfide (WS2), molybdenum disulfide (MoS2), titanium nitride (TiN), aluminum oxide (Al2O3), and titanium carbo-nitride (TiCN), respectively. The contribution rates of each factor were significant concerning General Linear Model (GLM) at 47.13% and 24.43% for WS2 and Al2O3 coatings materials, respectively. In the future, multi-layered coatings can be a valuable solution for the difficulties of machining the MMCs.

Analytically assisted FEM approach for the design and optimization of laterally excited bulk acoustic wave resonators (XBARs) with a high electromechanical coupling

Analytically assisted FEM approach for the design and optimization of laterally excited bulk acoustic wave resonators (XBARs) with a high electromechanical coupling

Soil-slope stability investigation using different nail inclinations: a comprehensive LSD, FEM and experimental approach

Soil-slope stability investigation using different nail inclinations: a comprehensive LSD, FEM and experimental approach

Mesoscale FEM approach on cemented sands: Generating and testing the digital twin

The mechanics of Cemented Granular Material (CGM) have been studied by means of geotechnical experimental testing, whose output consists the basis of mathematical models which approach the material response in various loading states. The information derived from standard experimental response curves is the basis of understanding and handling the material. Still, it is intuitive to analyse the CGM down to the mesoscale and dray conclusions over the interaction of the constituent material phases. Diverging from the practice of equivalent continuum, the alternative description of a three phase composite of sand particles, cement binder and void pores has been realised in this study. In order to implement the specific morphology of this multiphase, geomaterial, X-ray Computed Tomography is used to capture the internal structure and quantify it into a three dimensional greyvalue map (or a three dimensional image). The distinction of the material phases is made possible by the application of a developed filter, which corrects the artefacts caused by beam hardening phenomena and allows for the generation of a phase segmented equivalent image. An image adapted meshing algorithm has been utilized to transform the labelled image into a tetrahedral mesh, grouped into sets that correspond to the different materials. The tetrahedral domain was assigned boundary conditions and was numerically tested under uniaxial compression using the finite element method. The kinematics of the simulation proved that the mesoscale approach, which carries internal structure information of the granular fabric and the cement paste distribution, provides a output which captures the kinematics of the granular skeleton.

Simulation of the ultimate bearing capacity of a spread foundation on sandy soils: rigid plastic FEM approach with inclined load and size effect incorporating stress-dependent non-linear yield function

Simulation of the ultimate bearing capacity of a spread foundation on sandy soils: rigid plastic FEM approach with inclined load and size effect incorporating stress-dependent non-linear yield function

Thermodynamic optimization in laminar and fully developed flow in double pipe heat exchanger with arrow-shaped extended surfaces: A novel design

An innovative design of extended fins in the form of arrow fins is optimized for high performance heat transfer in a double pipe heat exchanger (DPHX). The arrow fins are designed within the trapezoidal fin to save material, weight, cost and making energy-efficient DPH. The arrow fins are investigated for the first time in DPHX. The FEM approach is used for computational simulation of the present work. A thermal boundary condition of constant heat flux is imposed on the arrow fins and inner pipe assembly. The results are computed in terms of fRe, Nusselt number and j-factor. The results dictate that the geometrical configurations of arrow DPHX for a significant rise in the values of the Nusselt number are: 80 % height of arrow fins is recommended when the number of arrow fins varies from 6 to 24, 20 % height for 30 arrow fins in the case of smaller values of radii ratio (Rˆ). For larger values of Rˆ, 20 % height of arrow fins may be selected for M=6&30, while for arrow fins varying from 12 to 24,H*=0.8 is recommended. On comparison of the thermal performance of the arrow-finned DPHX with the trapezoidal-finned DPHX, the maximum rise of the Nusselt number and j-factor are 113.2 % and 124.2 %, respectively. The proposed design of arrow-finned DPHX has advantages over the design of trapezoidal finned DPHX due to the significant decrease both in manufacturing cost and weight, increased thermal performance, and saving energy.

Method of matched sections as a beam-like approach for plate analysis

A new numerical method in application to the plate problem is suggested. It starts from consideration of the rectangular elements, each operating by 6 beam-like parameters: four bending parameters (displacement, angle of rotation, bending moment, transverse force) and two rotation parameters (angle of rotation and twisting moment). So, contrary to the classical FEM approach, the conjugation between the adjacent elements occurs between the adjacent sections rather than in polygon vertexes (nodes), and this gives the name to the method – method of matched sections, MMS. Technically, 6 left-side and 6 lower-side parameters are 12 inlet parameters, while 6 upper-side and right-side parameters are 12 outlet parameters; each element is defined by 24 parameters. Outlet parameters are related to inlet ones by 12 matrix relations, which are derived from the approximate solution of each differential equation (equilibrium, physical, and geometrical equations) of the plate theory. The matrix relation between inlet and outlet parameters is written in a form suitable for applying the transfer matrix method. The numerical examples for the thin and Mindlin plates show the high efficiency and accuracy of the method. In particular, the results for the Mindlin plate for minimal thickness give the same results as the thin plate (no shear locking); the method is insensitive to cases when, for adjacent elements, the ratio of dimensions or ratio of rigidities (elastic constants) differ by several orders of magnitude. The application of the method for the thermal as well as for the vibration problem is considered. The possible extension of the method to any curved geometry is discussed, too.