Finite Element Method Studies Research Articles

Three-dimensional theoretical model for effectively describing the effect of craniomaxillofacial structural factors on loading situation in the temporomandibular joint

BackgroundTemporomandibular joint (TMJ) overloading is considered a primary cause of temporomandibular joint disorders (TMD). Accordingly, craniomaxillofacial structural parameters affect the loading situation in the TMJ. However, no effective method exists for quantitatively measuring the loading variation in human TMJs. Clinical statistics, which draws from general rules from large amounts of clinical data, cannot entry for exploring the underlying biomechanical mechanism in craniomaxillofacial system. The finite element method (FEM) is an effective tool for analyze the stress and load on TMJs for several cases in a short period of time; however, it is difficult to generalize general patterns through calculations between different cases due to the different geometric characteristics and occlusal contacts between each case. Methods(1) This study included 88 subjects with 176 unilateral data to measure angle (α) of the distance to the plane of occlusion. The bone destruction score was evaluated for clinical statistics. To rule out effects of the potential factors and ensure the generality of the study, one participant with no obvious bone destruction was selected as the standard case for establishing the three-dimensional (3D) theoretical model and FEM. (2) Three groups of forces, including biting, muscles and joint reaction forces on mandible, were adopted to establish a 3D theoretical model. (3) By modifying the sagittal α and coronal three types of deviation angle (φ) of the original model, nine candidate models were obtained for the FEM studies. Results(1) The static equilibrium equations, were used to establish a 3D theoretical model for describing the loading of the TMJ. The theoretical model was validated by monotonously modifying the structural parameter in comparison to two-dimensional theoretical models reported previously; (2) The force on the TMJ gradually decreased with α, and this trend was validated by both clinic statistics and FEM results; (3) The effects of the three types of deviation angle were different. The results of the case where only rotating biting forces were considered was consistent with clinical statistics, indicating that the side with lower α experiences higher TMJ load. (4) Changing the unilateral proportionality coefficients of biting and muscle force produced opposite effects, wherein the effects of the muscle force were stronger than those of the biting forces. ConclusionsA negative correlation was observed between the joint load and α. Among the three types of asymmetric deformities, occlusal deviations were the primary factors leading to TMD. Unilateral occlusion can result in a greater load on the ipsilateral joint and should be avoided when using the side corresponding to the TMD. This study provides a theoretical basis for the biomechanical mechanism of TMD and also enables the targeted mitigation and treatment of TMD through structural modification.

Effect of Mg remelting and mechanical hooks of steel on the mechanical and fatigue responses of resistance element welded AZ31/DP780 joints: Experimental, FEM and thermodynamic calculation studies

This study focuses on the fatigue fracture response and microstructure behavior of a resistance element weld (REW) in assembling AZ31B magnesium alloy and dual phase (DP) 780 plates. With the increase of the welding current the prior austenite grain size (PAGS) increased, which resulted in a decrease in the fraction of an alpha prime martensite at the welding interface and had little influence on the dual phase at the welding interface. It is clear that the formation of a suitable hook accompanied by the phase transformation between S20C elements and DP780 steels at the interface can have a positive effect on the mechanical properties. However, the Mg melting and the formation of a partially melted zone (PMZ) affected the elongation decrease significantly. Furthermore, the insufficient penetrations of the welding interface, the severe melted Mg and the formation of porosities in the PMZ were fatal to the strength and fatigue performance. Morphologies and microstructure characteristics including phases of the REWed joint were quantitatively analyzed by electron back-scatter diffraction (EBSD) and thermodynamic calculation by coupling the phase diagrams (CALPHAD) method, respectively. The experiment results were incorporated into the finite element method (FEM) to numerically elucidate their effects against mechanical responses including fatigue behaviors. The results explained why the mechanical strength, fatigue endurance, and fracture modes are radically different for joint morphologies and microstructure developments.

Influence of Bone-Level Dental Implants Placement and of Cortical Thickness on Osseointegration: In Silico and In Vivo Analyses.

The purpose of this research is to study the biomechanical response of dental implants in bone-level type locations, 0.5 mm above and below the bone level. In addition, the influence of the thickness of the cortical bone on osseointegration is determined due to the mechanical loads transfer from the dental implant to the cortical and trabecular bone. The thicknesses studied were 1.5 mm and 2.5 mm. Numerical simulations were performed using a finite element method (FEM)-based model. In order to verify the FEM model, the in silico results were compared with the results obtained from a histological analysis performed in an in vivo study with 30 New Zealand rabbits. FEM was performed using a computerized 3D model of bone-level dental implants inserted in the lower jawbone with an applied axial load of 100 N. The analysis was performed using different distances from the bone level and different thicknesses of cortical bone. The interface area of bone growth was evaluated by analyzing the bone–implant contact (BIC), region of interest (ROI) and total bone area (BAT) parameters obtained through an in vivo histological process and analyzed by scanning electron microscopy (SEM). Bone-level implants were inserted in the rabbit tibiae, with two implants placed per tibia. These parameters were evaluated after three or six weeks of implantation. FEM studies showed that placements 0.5 mm below the bone level presented lower values of stress distribution compared to the other studied placements. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that this position presented the highest BIC value after three or six weeks of implantation. In this placement, vertical bone growth could be observed up the bone level. The smallest thickness of the study showed a better transfer of mechanical loads, which leads to a better osseointegration. In silico and in vivo results both concluded that the implants placed 0.5 mm below the cortical bone and with lower thicknesses presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

Finite Element Method for the Evaluation of the Human Spine: A Literature Overview.

The finite element method (FEM) represents a computer simulation method, originally used in civil engineering, which dates back to the early 1940s. Applications of FEM have also been used in numerous medical areas and in orthopedic surgery. Computing technology has improved over the years and as a result, more complex problems, such as those involving the spine, can be analyzed. The spine is a complex anatomical structure that maintains the erect posture and supports considerable loads. Applications of FEM in the spine have contributed to the understanding of bone biomechanics, both in healthy and abnormal conditions, such as scoliosis, fractures (trauma), degenerative disc disease and osteoporosis. However, since FEM is only a digital simulation of the real condition, it will never exactly simulate in vivo results. In particular, when it concerns biomechanics, there are many features that are difficult to represent in a FEM. More FEM studies and spine research are required in order to examine interpersonal spine stiffness, young spine biomechanics and model accuracy. In the future, patient-specific models will be used for better patient evaluations as well as for better pre- and inter-operative planning.

Crestal module design optimization of dental implants: finite element analysis and in vivo studies.

The aim of this study was to evaluate the biomechanical behavior of Bone Level dental implants with four different neck designs in contact with cortical bone. Numerical simulations were performed using a Finite Element Method (FEM) based-model. In order to verify the FEM model, the in silico results were compared with the results obtained from histological analysis performed in an in vivo study with New Zealand rabbits. FEM was performed using a computerized 3D model of Bone Level dental implants inserted in the lower jaw bone with an applied axial load of 100 N. The analysis was performed using four different implant neck designs: even surfaced, screwed, three-ring design and four-ring design. Interface are of bone growth was evaluated by analyzing the Bone-Implant-Contact (BIC) parameter obtained from in vivo histological process and analyzed by Scanning Electron Microscopy (SEM). Bone Level implants were inserted in the rabbit tibia, placing two implants per tibia. The BIC was evaluated after three and six weeks of implantation. FEM studies showed that the three-ring design presented lower values of stress distribution compared to the other studied designs. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that the three-ring design presented the highest BIC value after 3 and 6 weeks of implantation. In silico and in vivo results both concluded that the implants with three-ring neck design presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

The DEMO Helium Cooled Lithium Lead “advanced-plus” Breeding Blanket: Design improvement and FEM studies

In the framework of the European “HORIZON 2020” research program, the EUROfusion Consortium develops a design of a fusion demonstrator (DEMO). CEA-Saclay, with the support of Wigner-CR and IPP-CR, is in charge of one of the four Breeding Blanket (BB) concepts investigated in Europe for DEMO: the Helium Cooled Lithium Lead (HCLL) BB. The BB directly surrounding the plasma is a major component ensuring tritium self-sufficiency, shielding against neutrons from D-T plasmas and heat extraction for electricity conversion.In this article, the equatorial outboard module of the HCLL reference DEMO BB (“advanced-plus” BB) concept is studied regarding thermal and mechanical behavior during normal and accidental conditions that led to modify the design and enhance the performances. A numerical approach based on the Finite Element Method (FEM) is followed. The methodology established, the assumptions done as well as the results obtained in each case are reported and critically analysed, scrutinizing some open issues on this “advanced-plus” reference concept.

Electromagnetic FEM studies of disruptions and engineering consequences for the power supply and coils design of planned upper divertor at ASDEX Upgrade

A new upper divertor is proposed for the ASDEX Upgrade (AUG) tokamak experiment. It is planned to be equipped with internal coils for investigation of alternative magnetic configurations like e.g. “snowflake” (Herrmann et al., 2017 [1]). Since the coils are close to the plasma, high induced and very stiff voltages are expected during disruption events. Because only very vague analytical estimates of voltages, forces and coupling factors were available, an improvement by the help of Finite Element Method (FEM) was envisaged. Therefore, recorded measurements of currents, plasma position, plasma profile and the geometry were integrated in an electromagnetic simulation as boundary conditions to calculate resulting field distributions during selected AUG disruptions. The time resolution can be better than 100 μs and the required computing resources are comparably small due to the assumption of 2D axis-symmetry. The results were compared with magnetic probe measurements integrated into the tokamak ultimately observing good agreement. After this, the FE model was modified including the new divertor to calculate all relevant parameters. The output of these calculations has strong implications for the coil and power supply design: i) The power supply will be protected by a new kind of crowbar to avoid damage of the power supply due to overvoltage and uncontrolled current and force rise of the coils. The concept of this so called “ripping crowbar” is introduced, which is now under development. ii) The coil cable should be coaxial shaped to monitor isolation faults and to become inherently safe against single-turn shortcuts, identified as destructive fault scenario.

Design, 3D Modelling, and study on L-Bracket Rib Strength through FEM Analysis: A Comparative Study using Solid Works and Ansys Software

Brackets are integral to many engineering applications, providing structure support and stability. The use of FEM analysis in this study allows for a more accurate and detailed understanding of the behaviour of brackets under different loading conditions. Our findings provide valuable insights into the design and optimisation of frames using FEM, highlighting the novelty of this approach. In this study, we have designed and created a 3D model of a bracket using Solid Works software. The bracket's strength and other design parameters were investigated using Finite Element Method (FEM). FEM studies were carried out for different thicknesses, lengths, and rib designs in the bracket. The FEM results from Solid Works were compared with those obtained using Ansys software. Based on the comparison, we concluded the FEM results and suggested the optimum thickness and design of the rib. Additionally, we compared the deformation in Solid Works & ANSYS software for the same boundary & loading conditions for three different bracket configurations. Overall, this study demonstrates the potential of FEM analysis in improving the design and performance of brackets in engineering applications. By comparing the results from different software and configurations, we identified the optimal design parameters for the frame, providing a valuable contribution to the field.

Magnetic circuit modelling of transformer core induction – resolution and accuracy

As a tool for optimisation of transformer cores, numerical modelling is used to estimate local induction distributions. Compared to finite element method (FEM), the magnetic circuit modelling (MACC) uses much lower amounts of elements which raises questions of resolution and accuracy. This study compares MACC models of different resolutions, two flux paths (2FP) and four paths (4FP). Both are characterised by low computing times. The low resolution of 2FP offers compact information about global flux distributions, as a function of modified core geometry or material. The increased resolution of 4FP favours the assessment of regional concentration of rotational and circular magnetisation. A rough comparison with FEM illustrates that quantitative FEM studies of such mechanisms are impossible without specific post-processing. With respect to the overall accuracy of MACC, it is not determined by the number of elements but on the accuracy of geometrical assumptions and allocated permeability functions. For the transverse direction and overlap regions, the corresponding accuracy of related terms may be close to 10%, due to product tolerance or mechanical stress. Both high meshing densities and low approximation values are of academic nature. The attractiveness of modelling is not given by accuracy, but by revealing complex distributions with good approximation of instantaneous data.

Practical aspects of finite element method applications in dentistry

The use of numerical methods, such as finite element method (FEM), has been widely adopted in solving structural problems with complex geometry under external loads when analytical solutions are unachievable. Basic idea behind FEM is to divide the complex body geometry into smaller and simpler domains, called finite elements, and then to formulate solution for each element instead of seeking a solution for the entire domain. After finding the solutions for all elements they can be combined to obtain a solution for the whole domain. This numerical method is mostly used in engineering, but it is also useful for studying the biomechanical properties of materials used in medicine and the influence of mechanical forces on the biological systems. Since its introduction in dentistry four decades ago, FEM became powerful tool for the predictions of stress and strain distribution on teeth, dentures, implants and surrounding bone. FEM can indicate aspects of biomaterials and human tissues that can hardly be measured in vivo and can predict the stress distribution in the contact areas which are not accessible, such as areas between the implant and cortical bone, denture and gingiva, or around the apex of the implant in trabecular bone. Aim of this paper is to present - using results of several successful FEM studies - the usefulness of this method in solving dentistry problems, as well as discussing practical aspects of FEM applications in dentistry. Some of the method limitations, such as impossibility of complete replication of clinical conditions and need for simplified assumptions regarding loads and materials modeling, are also presented. However, the emphasis is on FE modelling of teeth, bone, dentures and implants and their modifications according to the requirements. All presented studies have been carried out in commercial software for FE analysis ANSYS Workbench.

3D multiscale modeling of strain localization in granular media

A hierarchical multiscale modeling approach is used to investigate three-dimensional (3D) strain localization in granular media. Central to the multiscale approach is a hierarchical coupling of finite element method (FEM) and discrete element method (DEM), wherein the FEM is employed to treat a boundary value problem of a granular material and the required constitutive relation for FEM is derived directly from the DEM solution of a granular assembly embedded at each of the FEM Gauss integration points as the representative volume element (RVE). While being effective in reproducing the complex mechanical responses of granular media, the hierarchical approach helps to bypass the necessity of phenomenological constitutive models commonly needed by conventional FEM studies and meanwhile offers a viable way to link the macroscopic observations with their underlying microscopic mechanisms. To model the phenomenon of strain localization, key issues pertaining to the selection of proper RVE packings are first discussed. The multiscale approach is then applied to simulate the strain localization problem in a cubical specimen and a cylindrical specimen subjected to either conventional triaxial compression (CTC) or conventional triaxial extension (CTE) loading, which is further compared to a case under plane-strain biaxial compression (PBC) loading condition. Different failure patterns, including localized, bulging and diffuse failure modes, are observed and analyzed. Amongst all testing conditions, the PBC condition is found most favorable for the formation of localized failure. The CTC test on the cubical specimen leads to a 3D octopus-shaped localization zone, whereas the cylindrical specimen under CTC shows seemingly bulging failure from the outlook but rather more complex failure patterns within the specimen. The CTE test on a uniform specimen normally ends in a diffuse failure. Different micro mechanisms and controlling factors underlying the various interesting observations are examined and discussed.

A review of finite-element modelling in snow mechanics

The finite-element method (FEM) is one of the main numerical analysis methods in continuum mechanics and mechanics of solids (Huebner and others, 2001). Through mesh discretization of a given continuous domain into a finite number of sub-domains, or elements, the method finds approximate solutions to sets of simultaneous partial differential equations, which express the behavior of the elements and the entire system. For decades this methodology has played an accelerated role in mechanical engineering, structural analysis and, in particular, snow mechanics. To the best of our knowledge, the application of finite-element analysis in snow mechanics has never been summarized. Therefore, in this correspondence we provide a table with a detailed review of the main FEM studies on snow mechanics performed from 1971 to 2012 (40 papers), for facilitating comparison between different mechanical approaches, outlining numerical recipes and for future reference. We believe that this kind of compact review in a tabulated form will produce a snapshot of the state of the art, and thus become an appropriate, timely and beneficial reference for any relevant follow-up research, including, for example, not only snow avalanche questions, but also modeling of snow microstructure and tire–snow interaction. To that end, this correspondence is organized according to the following structure. Table 1 includes all essential information about previously published FEM studies originally developed to investigate stresses in snow with all corresponding mechanical and numerical parameters. Columns in Table 1 provide references to particular studies, placed in chronological order. Rows correspond to the main model parameters and other details of each considered case.

Analysis and Comparison of a Permanent-Magnet DC Motor with a Field-Winding DC Motor

The influence of magnetic saturation on electromagnetic field distribution in both a permanent- magnet direct-current (PMDC) motor and a field-winding (wound-field) direct-current (FWDC) motor, with the same output mechanical power, has been studied. In this paper, an approximate analytical method and time-stepping Finite Element Method (FEM) are used for prediction of Back-EMF and electromagnetic torque. No-load and rotor-lucked conditions, according to experimental measurements, and the FEM and analytical method studies of the motors have been considered. A sensitivity analysis has also been successfully accomplished on the major design parameters that affect motor performance. At last, these two DC motors are compared, in spite of their differences, on the basis of measured output characteristics.

Methods for Describing the Electromagnetic Properties of Silver and Gold Nanoparticles

This Account provides an overview of the methods that are currently being used to study the electromagnetics of silver and gold nanoparticles, with an emphasis on the determination of extinction and surface-enhanced Raman scattering (SERS) spectra. These methods have proven to be immensely useful in recent years for interpreting a wide range of nanoscience experiments and providing the capability to describe optical properties of particles up to several hundred nanometers in dimension, including arbitrary particle structures and complex dielectric environments (adsorbed layers of molecules, nearby metal films, and other particles). While some of the methods date back to Mie's celebrated work a century ago, others are still at the forefront of algorithm development in computational electromagnetics. This Account gives a qualitative description of the physical and mathematical basis behind the most commonly used methods, including both analytical and numerical methods, as well as representative results of applications that are relevant to current experiments. The analytical methods that we discuss are either derived from Mie theory for spheres or from the quasistatic (Gans) model as applied to spheres and spheroids. In this discussion, we describe the use of Mie theory to determine electromagnetic contributions to SERS enhancements that include for retarded dipole emission effects, and the use of the quasistatic approximation for spheroidal particles interacting with dye adsorbate layers. The numerical methods include the discrete dipole approximation (DDA), the finite difference time domain (FDTD) method, and the finite element method (FEM) based on Whitney forms. We discuss applications such as using DDA to describe the interaction of two gold disks to define electromagnetic hot spots, FDTD for light interacting with metal wires that go from particle-like plasmonic response to the film-like transmission as wire dimension is varied, and FEM studies of electromagnetic fields near cubic particles.

Shear lag prediction in symmetrical laminated composite box beams using artificial neural network

Presence of high degree of orthotropy enhances shear lag phenomenon in laminated composite box-beams and it persists till failure. In this paper three key parameters governing shear lag behavior of laminated composite box beams are identified and defined by simple expressions. Uniqueness of the identified key parameters is proved with the help of finite element method (FEM) based studies. In addition to this, for the sake of generalization of prediction of shear lag effect in symmetrical laminated composite box beams a feed forward back propagation neural network (BPNN) model is developed. The network is trained and tested using the data base generated by extensive FEM studies carried out for various b/D, b/tF, tF/tW and laminate configurations. An optimum network architecture has been established which can effectively learn the pattern. Computational efficiency of the developed ANN makes it suitable for use in optimum design of laminated composite box-beams.

Finite-element analysis of the electric field distribution in conductance cell

The finite-element method (FEM) for the modeling of the electric field distribution in impedance cells designed according to the assumptions of the van der Pauw method of electrical conductivity (specific conductance) measurement has been used. Particularly, the effect of electrode-electrolyte solution interface (EESI) on the electric field distribution has been studied. It has been found that the EESI of current (driving) electrodes influences the cell electric field distribution. It has been concluded, as well, that the potential difference of the potential electrodes-being a measure of the conductivity of the electrolyte solution filling the cell-does not depend on whether EESI exists, provided the current electrodes are driven from a current source. The results of measurement experiments confirming the FEM studies are presented in the following paper as well.

Numerical Flow Simulation of Viscoplastic Slurries and Design Criteria for a Tape Casting Unit

Numerical simulations have been carried out using the finite element method (FEM) for the forming flow of ceramic tapes. The flow domain encompasses both the slurry reservoir and the doctor‐blade region with free surface and is fully two‐dimensional. The material of this study is an organic‐bonded alumina slurry used in a previous experimental investigation and is modeled as a viscoplastic Bing‐ham fluid with a yield stress. For different substrate speeds, the entire flow domain is analyzed and the extent and shape of yielded/unyielded regions are found. The computed free surface profiles are in close agreement with the experimental ones. Large vortices appear in the reservoir and their intensity is computed under different operating conditions. The lubrication approximation theory (LAT) is then used to deduce a new reservoir design with tapered walls avoiding recirculation. Subsequent FEM studies show the adequacy of the new design to achieve certain criteria such as elimination of vortices and an evenly distributed unyielded region. It is proposed that a combination of LAT and FEM techniques be used for design of ceramic tape casting equipment.