Finite element coiled cochlea model
Isailovic, Velibor; Nikolic, Milica; Milosevic, Zarko; Saveljic, Igor; Nikolic, Dalibor; Radovic, Milos; Filipović, Nenad
2015-12-01
Cochlea is important part of the hearing system, and thanks to special structure converts external sound waves into neural impulses which go to the brain. Shape of the cochlea is like snail, so geometry of the cochlea model is complex. The simplified cochlea coiled model was developed using finite element method inside SIFEM FP7 project. Software application is created on the way that user can prescribe set of the parameters for spiral cochlea, as well as material properties and boundary conditions to the model. Several mathematical models were tested. The acoustic wave equation for describing fluid in the cochlea chambers - scala vestibuli and scala timpani, and Newtonian dynamics for describing vibrations of the basilar membrane are used. The mechanical behavior of the coiled cochlea was analyzed and the third chamber, scala media, was not modeled because it does not have a significant impact on the mechanical vibrations of the basilar membrane. The obtained results are in good agreement with experimental measurements. Future work is needed for more realistic geometry model. Coiled model of the cochlea was created and results are compared with initial simplified coiled model of the cochlea.
Nonlinear finite element modeling of corrugated board
A. C. Gilchrist; J. C. Suhling; T. J. Urbanik
1999-01-01
In this research, an investigation on the mechanical behavior of corrugated board has been performed using finite element analysis. Numerical finite element models for corrugated board geometries have been created and executed. Both geometric (large deformation) and material nonlinearities were included in the models. The analyses were performed using the commercial...
Non-linear finite element modeling
DEFF Research Database (Denmark)
Mikkelsen, Lars Pilgaard
The note is written for courses in "Non-linear finite element method". The note has been used by the author teaching non-linear finite element modeling at Civil Engineering at Aalborg University, Computational Mechanics at Aalborg University Esbjerg, Structural Engineering at the University...
Finite Element Model of Gear Induction Hardening
Hodek, J; Zemko, M; Shykula, P
2015-01-01
International audience; This paper presents a finite element model of a gear induction hardening process. The gear was surface-heated by an induction coil and quickly cooled by spraying water. The finite element model was developed as a three-dimensional model. The electromagnetic field, temperature field, stress distribution and microstructure distribution were examined. Temperature and microstructural characteristics were measured and used. The gear material data was obtained in part by mea...
Verification of Orthogrid Finite Element Modeling Techniques
Steeve, B. E.
1996-01-01
The stress analysis of orthogrid structures, specifically with I-beam sections, is regularly performed using finite elements. Various modeling techniques are often used to simplify the modeling process but still adequately capture the actual hardware behavior. The accuracy of such 'Oshort cutso' is sometimes in question. This report compares three modeling techniques to actual test results from a loaded orthogrid panel. The finite element models include a beam, shell, and mixed beam and shell element model. Results show that the shell element model performs the best, but that the simpler beam and beam and shell element models provide reasonable to conservative results for a stress analysis. When deflection and stiffness is critical, it is important to capture the effect of the orthogrid nodes in the model.
Equivalent drawbead model in finite element simulations
Carleer, Bart D.; Carleer, B.D.; Meinders, Vincent T.; Huetink, Han; Lee, J.K.; Kinzel, G.L.; Wagoner, R.
1996-01-01
In 3D simulations of the deep drawing process the drawbead geometries are seldom included. Therefore equivalent drawbeads are used. In order to investigate the drawbead behaviour a 2D plane strain finite element model was used. For verification of this model experiments were performed. The analyses
Finite Element Modeling of Cracks and Joints
Directory of Open Access Journals (Sweden)
Jozef Čížik
2006-12-01
Full Text Available The application of finite element method to the analysis of discontinuous structural systems has received a considerable interest in recent years. Examples of problems in which discontinuities play a prominent role in the physical behaviour of a system are numerous and include various types of contact problems and layered or jointed systems. This paper gives a state-of-the-art report on the different methods developed to date for the finite element modelling of cracks and joints in discontinuous systems. Particular attention, however, has been given to the use of joint/interface elements, since their application is considered to be most appropriate for modelling of all kinds of discontinuities that may present in a structural system. A chronology of development of the main types of joint elements, including their pertinent characteristics, is also given. Advantages and disadvantages of the individual methods and types of joint elements presented are briefly discussed, together with various applications of interest.
Finite element modelling of TRIP steels
Energy Technology Data Exchange (ETDEWEB)
Papatriantafillou, I.; Aravas, N.; Haidemenopoulos, G.N. [Dept. of Mechanical and Industrial Engineering, Univ. of Thessaly, Volos (Greece)
2004-11-01
A constitutive model that describes the mechanical behaviour of steels exhibiting ''Transformation Induced Plasticity'' (TRIP) during martensitic transformation is presented. Multiphase TRIP steels are considered as composite materials with a ferritic matrix containing bainite and retained austenite, which gradually transforms into martensite. The effective properties and overall behaviour of TRIP steels are determined by using homogenization techniques for non-linear composites. The developed constitutive model considers the different hardening behaviour of the individual phases and estimates the apportionment of plastic strain and stress between the individual phases of the composite. A methodology for the numerical integration of the resulting elastoplastic constitutive equations in the context of the finite element method is developed and the constitutive model is implemented in a general-purpose finite element program. The prediction of the model in uniaxial tension agrees well with the experimental data. The problem of necking of a bar in uniaxial tension is studied in detail. (orig.)
Coupled finite element modeling of piezothermoelastic materials
Senousy, M. S.; Rajapakse, R. K. N. D.; Gadala, M.
2007-04-01
The governing equations of piezo-thermoelastic materials show full coupling between mechanical, electric, and temperature fields. It is often assumed in the literature that in high-frequency oscillations, the coupling between the temperature and mechanical displacement and electric field is small and, therefore, can be neglected. A solution for the temperature field is then determined from an uncoupled equation. A finite element (FE) model that accounts for full coupling between the mechanical, electric, and thermal fields, nonlinear constitutive behavior and heat generation resulting from dielectric losses under alternating driving fields is under development. This paper presents a linear fully coupled model as an early development of the fully coupled nonlinear FE model. In the linear model, a solution for all field variables is obtained simultaneously and compared with the uncoupled solution. The finite element model is based on the weighted-residual principle and uses 2-D four-node isoparametric finite elements with four degrees of freedom per node. A thin piezoelectric square disk is modeled to obtain some preliminary understanding of the coupled fields in a piezoelectric stack actuator.
Finite element modeling of lipid bilayer membranes
Feng, Feng; Klug, William S.
2006-12-01
A numerical simulation framework is presented for the study of biological membranes composed of lipid bilayers based on the finite element method. The classic model for these membranes employs a two-dimensional-fluid-like elastic constitutive law which is sensitive to curvature, and subjects vesicles to physically imposed constraints on surface area and volume. This model is implemented numerically via the use of C1-conforming triangular Loop subdivision finite elements. The validity of the framework is tested by computing equilibrium shapes from previously-determined axisymmetric shape-phase diagram of lipid bilayer vesicles with homogeneous material properties. Some of the benefits and challenges of finite element modeling of lipid bilayer systems are discussed, and it is indicated how this framework is natural for future investigation of biologically realistic bilayer structures involving nonaxisymmetric geometries, binding and adhesive interactions, heterogeneous mechanical properties, cytoskeletal interactions, and complex loading arrangements. These biologically relevant features have important consequences for the shape mechanics of nonidealized vesicles and cells, and their study requires not simply advances in theory, but also advances in numerical simulation techniques, such as those presented here.
Finite element modelling of contracting skeletal muscle.
Oomens, C W J; Maenhout, M; van Oijen, C H; Drost, M R; Baaijens, F P
2003-09-29
To describe the mechanical behaviour of biological tissues and transport processes in biological tissues, conservation laws such as conservation of mass, momentum and energy play a central role. Mathematically these are cast into the form of partial differential equations. Because of nonlinear material behaviour, inhomogeneous properties and usually a complex geometry, it is impossible to find closed-form analytical solutions for these sets of equations. The objective of the finite element method is to find approximate solutions for these problems. The concepts of the finite element method are explained on a finite element continuum model of skeletal muscle. In this case, the momentum equations have to be solved with an extra constraint, because the material behaves as nearly incompressible. The material behaviour consists of a highly nonlinear passive part and an active part. The latter is described with a two-state Huxley model. This means that an extra nonlinear partial differential equation has to be solved. The problems and solutions involved with this procedure are explained. The model is used to describe the mechanical behaviour of a tibialis anterior of a rat. The results have been compared with experimentally determined strains at the surface of the muscle. Qualitatively there is good agreement between measured and calculated strains, but the measured strains were higher.
Finite element modeling for materials engineers using Matlab
Oluwole, Oluleke
2014-01-01
Finite Element Modeling for Materials Engineers Using MATLAB® combines the finite element method with MATLAB to offer materials engineers a fast and code-free way of modeling for many materials processes.
Finite element modelling of helmeted head impact under frontal ...
Indian Academy of Sciences (India)
Abstract. Finite element models of the head and helmet were used to study contact forces during frontal impact of the head with a rigid surface. The finite element model of the head consists of skin, skull, cerebro-spinal fluid (CSF), brain, tentorium and falx. The finite element model of the helmet consists of shell and foam.
Finite element modeling methods for photonics
Rahman, B M Azizur
2013-01-01
The term photonics can be used loosely to refer to a vast array of components, devices, and technologies that in some way involve manipulation of light. One of the most powerful numerical approaches available to engineers developing photonic components and devices is the Finite Element Method (FEM), which can be used to model and simulate such components/devices and analyze how they will behave in response to various outside influences. This resource provides a comprehensive description of the formulation and applications of FEM in photonics applications ranging from telecommunications, astron
Parallel direct solver for finite element modeling of manufacturing processes
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Martins, P.A.F.
2017-01-01
The central processing unit (CPU) time is of paramount importance in finite element modeling of manufacturing processes. Because the most significant part of the CPU time is consumed in solving the main system of equations resulting from finite element assemblies, different approaches have been...... developed to optimize solutions and reduce the overall computational costs of large finite element models....
FINITE ELEMENT MODEL FOR PREDICTING RESIDUAL ...
African Journals Online (AJOL)
direction (σx) had a maximum value of 375MPa (tensile) and minimum value of ... These results shows that the residual stresses obtained by prediction from the finite element method are in fair agreement with the experimental results.
Finite-Element Modelling of Biotransistors
Directory of Open Access Journals (Sweden)
Selvaganapathy PR
2010-01-01
Full Text Available Abstract Current research efforts in biosensor design attempt to integrate biochemical assays with semiconductor substrates and microfluidic assemblies to realize fully integrated lab-on-chip devices. The DNA biotransistor (BioFET is an example of such a device. The process of chemical modification of the FET and attachment of linker and probe molecules is a statistical process that can result in variations in the sensed signal between different BioFET cells in an array. In order to quantify these and other variations and assess their importance in the design, complete physical simulation of the device is necessary. Here, we perform a mean-field finite-element modelling of a short channel, two-dimensional BioFET device. We compare the results of this model with one-dimensional calculation results to show important differences, illustrating the importance of the molecular structure, placement and conformation of DNA in determining the output signal.
Finite element modeling of retinal prosthesis mechanics
Basinger, B. C.; Rowley, A. P.; Chen, K.; Humayun, M. S.; Weiland, J. D.
2009-10-01
Epiretinal prostheses used to treat degenerative retina diseases apply stimulus via an electrode array fixed to the ganglion cell side of the retina. Mechanical pressure applied by these arrays to the retina, both during initial insertion and throughout chronic use, could cause sufficient retinal damage to reduce the device's effectiveness. In order to understand and minimize potential mechanical damage, we have used finite element analysis to model mechanical interactions between an electrode array and the retina in both acute and chronic loading configurations. Modeling indicates that an acute tacking force distributes stress primarily underneath the tack site and heel edge of the array, while more moderate chronic stresses are distributed more evenly underneath the array. Retinal damage in a canine model chronically implanted with a similar array occurred in correlating locations, and model predictions correlate well with benchtop eyewall compression tests. This model provides retinal prosthesis researchers with a tool to optimize the mechanical electrode array design, but the techniques used here represent a unique effort to combine a modifiable device and soft biological tissues in the same model and those techniques could be extended to other devices that come into mechanical contact with soft neural tissues.
Finite element modelling of solidification phenomena
Indian Academy of Sciences (India)
The process of solidification process is complex in nature and the simulation of such process is required in industry before it is actually undertaken. Finite element method is used to simulate the heat transfer process accompanying the solidification process. The metal and the mould along with the air gap formation is ...
Finite Element Modeling of Burr Formation in Metal Cutting
Min, Sangkee; Dornfeld, David; Kim, J.; Shyu, B.
2007-01-01
In order to advance understanding of the burr formation process, a series of finite element models are introduced. First a finite element model of the burr formation of two-dimensional orthogonal cutting is introduced and validated with experimental observations. A detailed and thorough examination of the drilling burr forming process is undertaken. This information is then used in the construction of an analytical model and, leads to development of a three-dimensional finite element mode...
Finite element modeling of piezoelectric elements with complex electrode configuration
International Nuclear Information System (INIS)
Paradies, R; Schläpfer, B
2009-01-01
It is well known that the material properties of piezoelectric materials strongly depend on the state of polarization of the individual element. While an unpolarized material exhibits mechanically isotropic material properties in the absence of global piezoelectric capabilities, the piezoelectric material properties become transversally isotropic with respect to the polarization direction after polarization. Therefore, for evaluating piezoelectric elements the material properties, including the coupling between the mechanical and the electromechanical behavior, should be addressed correctly. This is of special importance for the micromechanical description of piezoelectric elements with interdigitated electrodes (IDEs). The best known representatives of this group are active fiber composites (AFCs), macro fiber composites (MFCs) and the radial field diaphragm (RFD), respectively. While the material properties are available for a piezoelectric wafer with a homogeneous polarization perpendicular to its plane as postulated in the so-called uniform field model (UFM), the same information is missing for piezoelectric elements with more complex electrode configurations like the above-mentioned ones with IDEs. This is due to the inhomogeneous field distribution which does not automatically allow for the correct assignment of the material, i.e. orientation and property. A variation of the material orientation as well as the material properties can be accomplished by including the polarization process of the piezoelectric transducer in the finite element (FE) simulation prior to the actual load case to be investigated. A corresponding procedure is presented which automatically assigns the piezoelectric material properties, e.g. elasticity matrix, permittivity, and charge vector, for finite element models (FEMs) describing piezoelectric transducers according to the electric field distribution (field orientation and strength) in the structure. A corresponding code has been
Finite element modelling of composite castellated beam
Directory of Open Access Journals (Sweden)
Frans Richard
2017-01-01
Full Text Available Nowadays, castellated beam becomes popular in building structural as beam members. This is due to several advantages of castellated beam such as increased depth without any additional mass, passing the underfloor service ducts without changing of story elevation. However, the presence of holes can develop various local effects such as local buckling, lateral torsional buckling caused by compression force at the flange section of the steel beam. Many studies have investigated the failure mechanism of castellated beam and one technique which can prevent the beam fall into local failure is the use of reinforced concrete slab as lateral support on castellated beam, so called composite castellated beam. Besides of preventing the local failure of castellated beam, the concrete slab can increase the plasticity moment of the composite castellated beam section which can deliver into increasing the ultimate load of the beam. The aim of this numerical studies of composite castellated beam on certain loading condition (monotonic quasi-static loading. ABAQUS was used for finite element modelling purpose and compared with the experimental test for checking the reliability of the model. The result shows that the ultimate load of the composite castellated beam reached 6.24 times than the ultimate load of the solid I beam and 1.2 times compared the composite beam.
Material Models for the Human Torso Finite Element Model
2018-04-04
ARL-TR-8338 ● Apr 2018 US Army Research Laboratory Material Models for the Human Torso Finite Element Model by Carolyn E...longer needed. Do not return it to the originator. ARL-TR-8338 ● Apr 2018 US Army Research Laboratory Material Models for the...Weapons and Materials Research Directorate, ARL Approved for public release; distribution is unlimited. ii REPORT
Modelling bucket excavation by finite element
Pecingina, O. M.
2015-11-01
Changes in geological components of the layers from lignite pits have an impact on the sustainability of the cup path elements and under the action of excavation force appear efforts leading to deformation of the entire assembly. Application of finite element method in the optimization of components leads to economic growth, to increase the reliability and durability of the studied machine parts thus the machine. It is obvious usefulness of knowledge the state of mechanical tensions that the designed piece or the assembly not to break under the action of tensions that must cope during operation. In the course of excavation work on all bucket cutting force components, the first coming into contact with the material being excavated cutting edge. Therefore in the study with finite element analysis is retained only cutting edge. To study the field of stress and strain on the cutting edge will be created geometric patterns for each type of cup this will be subject to static analysis. The geometric design retains the cutting edge shape and on this on the tooth cassette location will apply an areal force on the abutment tooth. The cutting edge real pattern is subjected to finite element study for the worst case of rock cutting by symmetrical and asymmetrical cups whose profile is different. The purpose of this paper is to determine the displacement and tensions field for both profiles considering the maximum force applied on the cutting edge and the depth of the cutting is equal with the width of the cutting edge of the tooth. It will consider the worst case when on the structure will act both the tangential force and radial force on the bucket profile. For determination of stress and strain field on the form design of cutting edge profile will apply maximum force assuming uniform distribution and on the edge surface force will apply a radial force. After geometric patterns discretization on the cutting knives and determining stress field, can be seen that at the
Mixed finite elements for global tide models.
Cotter, Colin J; Kirby, Robert C
2016-01-01
We study mixed finite element methods for the linearized rotating shallow water equations with linear drag and forcing terms. By means of a strong energy estimate for an equivalent second-order formulation for the linearized momentum, we prove long-time stability of the system without energy accumulation-the geotryptic state. A priori error estimates for the linearized momentum and free surface elevation are given in [Formula: see text] as well as for the time derivative and divergence of the linearized momentum. Numerical results confirm the theoretical results regarding both energy damping and convergence rates.
Parallel direct solver for finite element modeling of manufacturing processes
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Martins, P.A.F.
2017-01-01
The central processing unit (CPU) time is of paramount importance in finite element modeling of manufacturing processes. Because the most significant part of the CPU time is consumed in solving the main system of equations resulting from finite element assemblies, different approaches have been d...
Shear beams in finite element modelling : Software implementation and validation
Schreppers, G.J.; Hendriks, M.A.N.; Boer, A.; Ferreira, D.; Kikstra, W.P.
2015-01-01
Fiber models for beam and shell elements allow for relatively rapid finite element analysis of concrete structures and structural elements. This project aims at the development of the formulation of such elements and a pilot implementation. The reduction of calculation time and degrees of freedom
Probabilistic finite element modeling of waste rollover
International Nuclear Information System (INIS)
Khaleel, M.A.; Cofer, W.F.; Al-fouqaha, A.A.
1995-09-01
Stratification of the wastes in many Hanford storage tanks has resulted in sludge layers which are capable of retaining gases formed by chemical and/or radiolytic reactions. As the gas is produced, the mechanisms of gas storage evolve until the resulting buoyancy in the sludge leads to instability, at which point the sludge ''rolls over'' and a significant volume of gas is suddenly released. Because the releases may contain flammable gases, these episodes of release are potentially hazardous. Mitigation techniques are desirable for more controlled releases at more frequent intervals. To aid the mitigation efforts, a methodology for predicting of sludge rollover at specific times is desired. This methodology would then provide a rational basis for the development of a schedule for the mitigation procedures. In addition, a knowledge of the sensitivity of the sludge rollovers to various physical and chemical properties within the tanks would provide direction for efforts to reduce the frequency and severity of these events. In this report, the use of probabilistic finite element analyses for computing the probability of rollover and the sensitivity of rollover probability to various parameters is described
Finite element modelling of helmeted head impact under frontal ...
Indian Academy of Sciences (India)
CSF), brain, tentorium and falx. The finite element model of the helmet consists of shell and foam liner. ... mechanical behaviour of motorcycle helmet. ... the latter authors use a SI (Structural Intensity) approach to study power flow distribution.
Finite element modeling of the filament winding process using ABAQUS
Miltenberger, Louis C.
1992-01-01
A comprehensive stress model of the filament winding fabrication process, previously implemented in the finite element program, WACSAFE, was implemented using the ABAQUS finite element software package. This new implementation, referred to as the ABWACSAFE procedure, consists of the ABAQUS software and a pre/postprocessing routine that was developed to prepare necessary ABAQUS input files and process ABAQUS displacement results for stress and strain computation. The ABWACSAF...
Finite element modelling of helmeted head impact under frontal ...
Indian Academy of Sciences (India)
2016-08-26
Aug 26, 2016 ... Finite element models of the head and helmet were used to study contact forces during frontal impact of the head with a rigid surface. The ﬁnite element model of the head consists of skin, skull, cerebro-spinal ﬂuid (CSF), brain, tentorium and falx. The ﬁnite element model of the helmet consists of shell and ...
A nonlinear dynamic corotational finite element model for submerged pipes
De Vries, F. H.; Geijselaers, H. J.M.; Van Den Boogaard, A. H.; Huisman, A.
2017-01-01
A three dimensional finite element model is built to compute the motions of a pipe that is being laid on the seabed. This process is geometrically nonlinear, therefore co-rotational beam elements are used. The pipe is subject to static and dynamic forces. Static forces are due to gravity, current
The Finite Element Numerical Modelling of 3D Magnetotelluric
Directory of Open Access Journals (Sweden)
Ligang Cao
2014-01-01
Full Text Available The ideal numerical simulation of 3D magnetotelluric was restricted by the methodology complexity and the time-consuming calculation. Boundary values, the variation of weighted residual equation, and the hexahedral mesh generation method of finite element are three major causes. A finite element method for 3D magnetotelluric numerical modeling is presented in this paper as a solution for the problem mentioned above. In this algorithm, a hexahedral element coefficient matrix for magnetoelluric finite method is developed, which solves large-scale equations using preconditioned conjugate gradient of the first-type boundary conditions. This algorithm is verified using the homogeneous model, and the positive landform model, as well as the low resistance anomaly model.
AEROTAXI ground static test and finite element model validation
Directory of Open Access Journals (Sweden)
Radu BISCA
2011-06-01
Full Text Available In this presentation, we will concentrate on typical Ground Static Test (GST and Finite Element (FE software comparisons. It is necessary to note, that standard GST are obligatory for any new aircraft configuration. We can mention here the investigations of the AeroTAXITM, a small aircraft configuration, using PRODERA® equipment. A Finite Element Model (FEM of the AeroTAXITM has been developed in PATRAN/NASTRAN®, partly from a previous ANSYS® model. FEM can be used to investigate potential structural modifications or changes with realistic component corrections. Model validation should be part of every modern engineering analysis and quality assurance procedure.
FINITE ELEMENT MODELING OF THIN CIRCULAR SANDWICH PLATES DEFLECTION
Directory of Open Access Journals (Sweden)
K. S. Kurachka
2014-01-01
Full Text Available A mathematical model of a thin circular sandwich plate being under the vertical load is proposed. The model employs the finite element method and takes advantage of an axisymmetric finite element that leads to the small dimension of the resulting stiffness matrix and sufficient accuracy for practical calculations. The analytical expressions for computing local stiffness matrices are found, which can significantly speed up the process of forming the global stiffness matrix and increase the accuracy of calculations. A software is under development and verification. The discrepancy between the results of the mathematical model and those of analytical formulas for homogeneous thin circularsandwich plates does not exceed 7%.
The finite-difference and finite-element modeling of seismic wave propagation and earthquake motion
International Nuclear Information System (INIS)
Moszo, P.; Kristek, J.; Galis, M.; Pazak, P.; Balazovijech, M.
2006-01-01
Numerical modeling of seismic wave propagation and earthquake motion is an irreplaceable tool in investigation of the Earth's structure, processes in the Earth, and particularly earthquake phenomena. Among various numerical methods, the finite-difference method is the dominant method in the modeling of earthquake motion. Moreover, it is becoming more important in the seismic exploration and structural modeling. At the same time we are convinced that the best time of the finite-difference method in seismology is in the future. This monograph provides tutorial and detailed introduction to the application of the finite-difference, finite-element, and hybrid finite-difference-finite-element methods to the modeling of seismic wave propagation and earthquake motion. The text does not cover all topics and aspects of the methods. We focus on those to which we have contributed. (Author)
Ruiz-Baier, Ricardo; Lunati, Ivan
2016-10-01
We present a novel discretization scheme tailored to a class of multiphase models that regard the physical system as consisting of multiple interacting continua. In the framework of mixture theory, we consider a general mathematical model that entails solving a system of mass and momentum equations for both the mixture and one of the phases. The model results in a strongly coupled and nonlinear system of partial differential equations that are written in terms of phase and mixture (barycentric) velocities, phase pressure, and saturation. We construct an accurate, robust and reliable hybrid method that combines a mixed finite element discretization of the momentum equations with a primal discontinuous finite volume-element discretization of the mass (or transport) equations. The scheme is devised for unstructured meshes and relies on mixed Brezzi-Douglas-Marini approximations of phase and total velocities, on piecewise constant elements for the approximation of phase or total pressures, as well as on a primal formulation that employs discontinuous finite volume elements defined on a dual diamond mesh to approximate scalar fields of interest (such as volume fraction, total density, saturation, etc.). As the discretization scheme is derived for a general formulation of multicontinuum physical systems, it can be readily applied to a large class of simplified multiphase models; on the other, the approach can be seen as a generalization of these models that are commonly encountered in the literature and employed when the latter are not sufficiently accurate. An extensive set of numerical test cases involving two- and three-dimensional porous media are presented to demonstrate the accuracy of the method (displaying an optimal convergence rate), the physics-preserving properties of the mixed-primal scheme, as well as the robustness of the method (which is successfully used to simulate diverse physical phenomena such as density fingering, Terzaghi's consolidation
Finite element modelling of fibre-reinforced brittle materials
Kullaa, J.
1997-01-01
The tensile constitutive behaviour of fibre-reinforced brittle materials can be extended to two or three dimensions by using the finite element method with crack models. The three approaches in this study include the smeared and discrete crack concepts and a multi-surface plasticity model. The
Finite Element Modelling Of Solidification Of Zinc Alloy | Osinkolu ...
African Journals Online (AJOL)
The solidification process of Zinc alloy is modelled by solving heat transfer equations with the aid of finite element method (FEM) using appropriate boundary conditions at the mould walls. The commercial software, Matlab, has been used to model the solidification process. The temperature profiles for each casting condition ...
Finite Element Modeling of Airflow During Phonation
Directory of Open Access Journals (Sweden)
Šidlof P.
2010-07-01
Full Text Available In the paper a mathematical model of airflow in human vocal folds is presented. The geometry of the glottal channel is based on measurements of excised human larynges. The airflow is modeled by nonstationary incompressible Navier-Stokes equations in a 2D computational domain, which is deformed in time due to vocal fold vibration. The paper presents numerical results and focuses on flow separation in glottis. Quantitative data from numerical simulations are compared to results of measurements by Particle Image Velocimetry (PIV, performed on a scaled self-oscillating physical model of vocal folds.
Three dimensional mathematical model of tooth for finite element analysis
Directory of Open Access Journals (Sweden)
Puškar Tatjana
2010-01-01
Full Text Available Introduction. The mathematical model of the abutment tooth is the starting point of the finite element analysis of stress and deformation of dental structures. The simplest and easiest way is to form a model according to the literature data of dimensions and morphological characteristics of teeth. Our method is based on forming 3D models using standard geometrical forms (objects in programmes for solid modeling. Objective. Forming the mathematical model of abutment of the second upper premolar for finite element analysis of stress and deformation of dental structures. Methods. The abutment tooth has a form of a complex geometric object. It is suitable for modeling in programs for solid modeling SolidWorks. After analyzing the literature data about the morphological characteristics of teeth, we started the modeling dividing the tooth (complex geometric body into simple geometric bodies (cylinder, cone, pyramid,.... Connecting simple geometric bodies together or substricting bodies from the basic body, we formed complex geometric body, tooth. The model is then transferred into Abaqus, a computational programme for finite element analysis. Transferring the data was done by standard file format for transferring 3D models ACIS SAT. Results. Using the programme for solid modeling SolidWorks, we developed three models of abutment of the second maxillary premolar: the model of the intact abutment, the model of the endodontically treated tooth with two remaining cavity walls and the model of the endodontically treated tooth with two remaining walls and inserted post. Conclusion Mathematical models of the abutment made according to the literature data are very similar with the real abutment and the simplifications are minimal. These models enable calculations of stress and deformation of the dental structures. The finite element analysis provides useful information in understanding biomechanical problems and gives guidance for clinical research.
[Three dimensional mathematical model of tooth for finite element analysis].
Puskar, Tatjana; Vasiljević, Darko; Marković, Dubravka; Jevremović, Danimir; Pantelić, Dejan; Savić-Sević, Svetlana; Murić, Branka
2010-01-01
The mathematical model of the abutment tooth is the starting point of the finite element analysis of stress and deformation of dental structures. The simplest and easiest way is to form a model according to the literature data of dimensions and morphological characteristics of teeth. Our method is based on forming 3D models using standard geometrical forms (objects) in programmes for solid modeling. Forming the mathematical model of abutment of the second upper premolar for finite element analysis of stress and deformation of dental structures. The abutment tooth has a form of a complex geometric object. It is suitable for modeling in programs for solid modeling SolidWorks. After analysing the literature data about the morphological characteristics of teeth, we started the modeling dividing the tooth (complex geometric body) into simple geometric bodies (cylinder, cone, pyramid,...). Connecting simple geometric bodies together or substricting bodies from the basic body, we formed complex geometric body, tooth. The model is then transferred into Abaqus, a computational programme for finite element analysis. Transferring the data was done by standard file format for transferring 3D models ACIS SAT. Using the programme for solid modeling SolidWorks, we developed three models of abutment of the second maxillary premolar: the model of the intact abutment, the model of the endodontically treated tooth with two remaining cavity walls and the model of the endodontically treated tooth with two remaining walls and inserted post. Mathematical models of the abutment made according to the literature data are very similar with the real abutment and the simplifications are minimal. These models enable calculations of stress and deformation of the dental structures. The finite element analysis provides useful information in understanding biomechanical problems and gives guidance for clinical research.
A Finite Element Approach to Modeling Abrasive Wear Modes
Woldman, M.; van der Heide, Emile; Tinga, Tiedo; Masen, Marc Arthur
2016-01-01
Machine components operating in sandy environments will wear because of the abrasive interaction with sand particles. In this work, a method is derived to predict the amount of wear caused by such abrasive action, in order to improve the maintenance concept of the components. A finite element model
Finite element modeling of intermuscular interactions and myofascial force transmission
Yucesoy, C.A.; Koopman, Hubertus F.J.M.; Huijing, P.A.J.B.M.; Grootenboer, H.J.
2001-01-01
A finite element muscle model to study the principles of intermuscular myofascial force transmission is developed. The results obtained explain force differences at the distal and proximal tendons of muscles that have mechanical interaction. This is in agreement with experimental findings in other
Finite element modelling of elastic intraplate stresses due to ...
Indian Academy of Sciences (India)
Finite element modelling of elastic intraplate stresses due to heterogeneities in crustal density and mechanical properties for the Jabalpur earthquake region, central India. A Manglik1,∗. , S Thiagarajan. 1. , A V Mikhailova. 2 and Yu Rebetsky. 2. 1. National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, ...
finite element model for predicting residual stresses in shielded
African Journals Online (AJOL)
eobe
Diffractometer (XRD 6000). From the Finite Element Model Simulation, the transverse residual stress in the x ... Keywords: Residual stress, 3D FEM, Shielded manual metal arc welding, Low Carbon Steel (ASTM A36), X-Ray diffraction, degree of ..... I. ''Residual stress effects on fatigue life of welded structures using LEFM'',.
Finite element modeling of corneal strip extensometry
CSIR Research Space (South Africa)
Botha, N
2012-12-01
Full Text Available Donnell, ?Corneal tensile strength in fully healed radial keratotomy wounds.? Investigative Ophthalmology & Visual Science, vol. 35, no. 7, pp. 3022 ?3031, Jun. 1994. [Online]. Available: http://www.iovs.org/content/35/7/3022.abstract [12] A. Elsheikh, M. Brown...- timization process, are listed in Table I for two different age groups [12]. Note that the incompressibility parameter, D1, c SACAM 2012 26 is fixed at 0.004, which ensures the incompressibility of the material model. The corresponding extensometry test...
Adaptive Smoothed Finite Elements (ASFEM) for history dependent material models
Quak, W.; van den Boogaard, Antonius H.; Menary, Gary
2011-01-01
A successful simulation of a bulk forming process with finite elements can be difficult due to distortion of the finite elements. Nodal smoothed Finite Elements (NSFEM) are an interesting option for such a process since they show good distortion insensitivity and moreover have locking-free behavior
Finite element model for nonlinear shells of revolution
International Nuclear Information System (INIS)
Cook, W.A.
1979-01-01
Nuclear material shipping containers have shells of revolution as basic structural components. Analytically modeling the response of these containers to severe accident impact conditions requires a nonlinear shell-of-revolution model that accounts for both geometric and material nonlinearities. Existing models are limited to large displacements, small rotations, and nonlinear materials. The paper presents a finite element model for a nonlinear shell of revolution that will account for large displacements, large strains, large rotations, and nonlinear materials
Sensitive analysis of a finite element model of orthogonal cutting
Brocail, J.; Watremez, M.; Dubar, L.
2011-01-01
This paper presents a two-dimensional finite element model of orthogonal cutting. The proposed model has been developed with Abaqus/explicit software. An Arbitrary Lagrangian-Eulerian (ALE) formulation is used to predict chip formation, temperature, chip-tool contact length, chip thickness, and cutting forces. This numerical model of orthogonal cutting will be validated by comparing these process variables to experimental and numerical results obtained by Filice et al. [1]. This model can be considered to be reliable enough to make qualitative analysis of entry parameters related to cutting process and frictional models. A sensitivity analysis is conducted on the main entry parameters (coefficients of the Johnson-Cook law, and contact parameters) with the finite element model. This analysis is performed with two levels for each factor. The sensitivity analysis realised with the numerical model on the entry parameters has allowed the identification of significant parameters and the margin identification of parameters.
Directory of Open Access Journals (Sweden)
P.B. Silva
2013-01-01
Full Text Available Structural spectral elements are formulated using the analytical solution of the applicable elastodynamic equations and, therefore, mesh refinement is not needed to analyze high frequency behavior provided the elastodynamic equations used remain valid. However, for modeling complex structures, standard spectral elements require long and cumbersome analytical formulation. In this work, a method to build spectral finite elements from a finite element model of a slice of a structural waveguide (a structure with one dimension much larger than the other two is proposed. First, the transfer matrix of the structural waveguide is obtained from the finite element model of a thin slice. Then, the wavenumbers and wave propagation modes are obtained from the transfer matrix and used to build the spectral element matrix. These spectral elements can be used to model homogeneous waveguides with constant cross section over long spans without the need of refining the finite element mesh along the waveguide. As an illustrating example, spectral elements are derived for straight uniform rods and beams and used to calculate the forced response in the longitudinal and transverse directions. Results obtained with the spectral element formulation are shown to agree well with results obtained with a finite element model of the whole beam. The proposed approach can be used to generate spectral elements of waveguides of arbitrary cross section and, potentially, of arbitrary order.
Finite element realization of the UH model for unsaturated soils
International Nuclear Information System (INIS)
Luo Ting; Zhang Panpan; Yao Yangping; Liu Yuemiao
2014-01-01
Gaomiaozi bentonite which is the buffer/backfill materials of the HLW geological repository will be overconsolidated and unsaturated in a long period. The study of the model for overconsolidated unsaturated soils and its finite element application is of practical value. Based on the user subroutines, the UH model for unsaturated soils is developed in ABAQUS. Numerical simulations of triaxial test are performed using this program. The results obtained show a good agreement with the analytic solutions and the experimental data. (authors)
A verification procedure for MSC/NASTRAN Finite Element Models
Stockwell, Alan E.
1995-01-01
Finite Element Models (FEM's) are used in the design and analysis of aircraft to mathematically describe the airframe structure for such diverse tasks as flutter analysis and actively controlled landing gear design. FEM's are used to model the entire airplane as well as airframe components. The purpose of this document is to describe recommended methods for verifying the quality of the FEM's and to specify a step-by-step procedure for implementing the methods.
A finite element model of ferroelectric/ferroelastic polycrystals
Energy Technology Data Exchange (ETDEWEB)
HWANG,STEPHEN C.; MCMEEKING,ROBERT M.
2000-02-17
A finite element model of polarization switching in a polycrystalline ferroelectric/ferroelastic ceramic is developed. It is assumed that a crystallite switches if the reduction in potential energy of the polycrystal exceeds a critical energy barrier per unit volume of switching material. Each crystallite is represented by a finite element with the possible dipole directions assigned randomly subject to crystallographic constraints. The model accounts for both electric field induced (i.e. ferroelectric) switching and stress induced (i.e. ferroelastic) switching with piezoelectric interactions. Experimentally measured elastic, dielectric, and piezoelectric constants are used consistently, but different effective critical energy barriers are selected phenomenologically. Electric displacement versus electric field, strain versus electric field, stress versus strain, and stress versus electric displacement loops of a ceramic lead lanthanum zirconate titanate (PLZT) are modeled well below the Curie temperature.
Finite element modeling of trolling-mode AFM.
Sajjadi, Mohammadreza; Pishkenari, Hossein Nejat; Vossoughi, Gholamreza
2018-03-14
Trolling mode atomic force microscopy (TR-AFM) has overcome many imaging problems in liquid environments by considerably reducing the liquid-resonator interaction forces. The finite element model of the TR-AFM resonator considering the effects of fluid and nanoneedle flexibility is presented in this research, for the first time. The model is verified by ABAQUS software. The effect of installation angle of the microbeam relative to the horizon and the effect of fluid on the system behavior are investigated. Using the finite element model, frequency response curve of the system is obtained and validated around the frequency of the operating mode by the available experimental results, in air and liquid. The changes in the natural frequencies in the presence of liquid are studied. The effects of tip-sample interaction on the excitation of higher order modes of the system are also investigated in air and liquid environments. Copyright © 2018 Elsevier B.V. All rights reserved.
Finite element modeling of TFTR poloidal field coils
International Nuclear Information System (INIS)
Baumgartner, J.A.; O'Toole, J.A.
1986-01-01
The Tokamak Fusion Test Reactor (TFTR) Poloidal Field (PF) coils were originally analyzed to TFTR design conditions. The coils have been reanalyzed by PPPL and Grumman to determine operating limits under as-built conditions. Critical stress levels, based upon data obtained from the reanalysis of each PF coil, are needed for input to the TFTR simulation code algorithms. The primary objective regarding structural integrity has been to ascertain the magnitude and location of critical internal stresses in each PF coil due to various combinations of electromagnetic and thermally induced loads. For each PF coil, a global finite element model (FEM) of a coil sector is being analyzed to obtain the basic coil internal loads and displacements. Subsequent fine mesh local models of the coil lead stem and lead spur regions produce the magnitudes and locations of peak stresses. Each copper turn and its surrounding insulation are modeled using solid finite elements. The corresponding electromagnetic and thermal analyses are similarly modeled. A series of test beams were developed to determine the best combination of MSC/NASTRAN-type finite elements for use in PF coil analysis. The results of this analysis compare favorably with those obtained by the earlier analysis which was limited in scope
Adaptive Smoothed Finite Elements (ASFEM) for history dependent material models
International Nuclear Information System (INIS)
Quak, W.; Boogaard, A. H. van den
2011-01-01
A successful simulation of a bulk forming process with finite elements can be difficult due to distortion of the finite elements. Nodal smoothed Finite Elements (NSFEM) are an interesting option for such a process since they show good distortion insensitivity and moreover have locking-free behavior and good computational efficiency. In this paper a method is proposed which takes advantage of the nodally smoothed field. This method, named adaptive smoothed finite elements (ASFEM), revises the mesh for every step of a simulation without mapping the history dependent material parameters. In this paper an updated-Lagrangian implementation is presented. Several examples are given to illustrate the method and to show its properties.
Finite-element modelling of multilayer X-ray optics.
Cheng, Xianchao; Zhang, Lin
2017-05-01
Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical size 60 mm × 60 mm × 100-300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (10 7 ) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 10 16 elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 10 6 ), which causes low solution accuracy; and the number of elements is still very large (10 6 ). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.
Finite-element modelling of multilayer X-ray optics
Energy Technology Data Exchange (ETDEWEB)
Cheng, Xianchao; Zhang, Lin
2017-04-11
Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical size 60 mm × 60 mm × 100–300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (10^{7}) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 10^{16}elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 10^{6}), which causes low solution accuracy; and the number of elements is still very large (10^{6}). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.
Modeling Intracochlear Magnetic Stimulation: A Finite-Element Analysis.
Mukesh, S; Blake, D T; McKinnon, B J; Bhatti, P T
2017-08-01
This study models induced electric fields, and their gradient, produced by pulsatile current stimulation of submillimeter inductors for cochlear implantation. Using finite-element analysis, the lower chamber of the cochlea, scala tympani, is modeled as a cylindrical structure filled with perilymph bounded by tissue, bone, and cochlear neural elements. Single inductors as well as an array of inductors are modeled. The coil strength (~100 nH) and excitation parameters (peak current of 1-5 A, voltages of 16-20 V) are based on a formative feasibility study conducted by our group. In that study, intracochlear micromagnetic stimulation achieved auditory activation as measured through the auditory brainstem response in a feline model. With respect to the finite element simulations, axial symmetry of the inductor geometry is exploited to improve computation time. It is verified that the inductor coil orientation greatly affects the strength of the induced electric field and thereby the ability to affect the transmembrane potential of nearby neural elements. Furthermore, upon comparing an array of micro-inductors with a typical multi-site electrode array, magnetically excited arrays retain greater focus in terms of the gradient of induced electric fields. Once combined with further in vivo analysis, this modeling study may enable further exploration of the mechanism of magnetically induced, and focused neural stimulation.
SPLAI: Computational Finite Element Model for Sensor Networks
Directory of Open Access Journals (Sweden)
Ruzana Ishak
2006-01-01
Full Text Available Wireless sensor network refers to a group of sensors, linked by a wireless medium to perform distributed sensing task. The primary interest is their capability in monitoring the physical environment through the deployment of numerous tiny, intelligent, wireless networked sensor nodes. Our interest consists of a sensor network, which includes a few specialized nodes called processing elements that can perform some limited computational capabilities. In this paper, we propose a model called SPLAI that allows the network to compute a finite element problem where the processing elements are modeled as the nodes in the linear triangular approximation problem. Our model also considers the case of some failures of the sensors. A simulation model to visualize this network has been developed using C++ on the Windows environment.
Calibration of a finite element composite delamination model by experiments
DEFF Research Database (Denmark)
Gaiotti, M.; Rizzo, C.M.; Branner, Kim
2013-01-01
This paper deals with the mechanical behavior under in plane compressive loading of thick and mostly unidirectional glass fiber composite plates made with an initial embedded delamination. The delamination is rectangular in shape, causing the separation of the central part of the plate into two...... distinct sub-laminates. The work focuses on experimental validation of a finite element model built using the 9-noded MITC9 shell elements, which prevent locking effects and aiming to capture the highly non linear buckling features involved in the problem. The geometry has been numerically defined...
Statistical osteoporosis models using composite finite elements: a parameter study.
Wolfram, Uwe; Schwen, Lars Ole; Simon, Ulrich; Rumpf, Martin; Wilke, Hans-Joachim
2009-09-18
Osteoporosis is a widely spread disease with severe consequences for patients and high costs for health care systems. The disease is characterised by a loss of bone mass which induces a loss of mechanical performance and structural integrity. It was found that transverse trabeculae are thinned and perforated while vertical trabeculae stay intact. For understanding these phenomena and the mechanisms leading to fractures of trabecular bone due to osteoporosis, numerous researchers employ micro-finite element models. To avoid disadvantages in setting up classical finite element models, composite finite elements (CFE) can be used. The aim of the study is to test the potential of CFE. For that, a parameter study on numerical lattice samples with statistically simulated, simplified osteoporosis is performed. These samples are subjected to compression and shear loading. Results show that the biggest drop of compressive stiffness is reached for transverse isotropic structures losing 32% of the trabeculae (minus 89.8% stiffness). The biggest drop in shear stiffness is found for an isotropic structure also losing 32% of the trabeculae (minus 67.3% stiffness). The study indicates that losing trabeculae leads to a worse drop of macroscopic stiffness than thinning of trabeculae. The results further demonstrate the advantages of CFEs for simulating micro-structured samples.
Building Finite Element Models to Investigate Zebrafish Jaw Biomechanics.
Brunt, Lucy H; Roddy, Karen A; Rayfield, Emily J; Hammond, Chrissy L
2016-12-03
Skeletal morphogenesis occurs through tightly regulated cell behaviors during development; many cell types alter their behavior in response to mechanical strain. Skeletal joints are subjected to dynamic mechanical loading. Finite element analysis (FEA) is a computational method, frequently used in engineering that can predict how a material or structure will respond to mechanical input. By dividing a whole system (in this case the zebrafish jaw skeleton) into a mesh of smaller 'finite elements', FEA can be used to calculate the mechanical response of the structure to external loads. The results can be visualized in many ways including as a 'heat map' showing the position of maximum and minimum principal strains (a positive principal strain indicates tension while a negative indicates compression. The maximum and minimum refer the largest and smallest strain). These can be used to identify which regions of the jaw and therefore which cells are likely to be under particularly high tensional or compressional loads during jaw movement and can therefore be used to identify relationships between mechanical strain and cell behavior. This protocol describes the steps to generate Finite Element models from confocal image data on the musculoskeletal system, using the zebrafish lower jaw as a practical example. The protocol leads the reader through a series of steps: 1) staining of the musculoskeletal components, 2) imaging the musculoskeletal components, 3) building a 3 dimensional (3D) surface, 4) generating a mesh of Finite Elements, 5) solving the FEA and finally 6) validating the results by comparison to real displacements seen in movements of the fish jaw.
Finite-element numerical modeling of atmospheric turbulent boundary layer
Lee, H. N.; Kao, S. K.
1979-01-01
A dynamic turbulent boundary-layer model in the neutral atmosphere is constructed, using a dynamic turbulent equation of the eddy viscosity coefficient for momentum derived from the relationship among the turbulent dissipation rate, the turbulent kinetic energy and the eddy viscosity coefficient, with aid of the turbulent second-order closure scheme. A finite-element technique was used for the numerical integration. In preliminary results, the behavior of the neutral planetary boundary layer agrees well with the available data and with the existing elaborate turbulent models, using a finite-difference scheme. The proposed dynamic formulation of the eddy viscosity coefficient for momentum is particularly attractive and can provide a viable alternative approach to study atmospheric turbulence, diffusion and air pollution.
Gleadall, Andrew; Pan, Jingzhe; Ding, Lifeng; Kruft, Marc-Anton; Curcó, David
2015-11-01
Molecular dynamics (MD) simulations are widely used to analyse materials at the atomic scale. However, MD has high computational demands, which may inhibit its use for simulations of structures involving large numbers of atoms such as amorphous polymer structures. An atomic-scale finite element method (AFEM) is presented in this study with significantly lower computational demands than MD. Due to the reduced computational demands, AFEM is suitable for the analysis of Young's modulus of amorphous polymer structures. This is of particular interest when studying the degradation of bioresorbable polymers, which is the topic of an accompanying paper. AFEM is derived from the inter-atomic potential energy functions of an MD force field. The nonlinear MD functions were adapted to enable static linear analysis. Finite element formulations were derived to represent interatomic potential energy functions between two, three and four atoms. Validation of the AFEM was conducted through its application to atomic structures for crystalline and amorphous poly(lactide). Copyright © 2015 Elsevier Ltd. All rights reserved.
Model order reduction techniques with applications in finite element analysis
Qu, Zu-Qing
2004-01-01
Despite the continued rapid advance in computing speed and memory the increase in the complexity of models used by engineers persists in outpacing them. Even where there is access to the latest hardware, simulations are often extremely computationally intensive and time-consuming when full-blown models are under consideration. The need to reduce the computational cost involved when dealing with high-order/many-degree-of-freedom models can be offset by adroit computation. In this light, model-reduction methods have become a major goal of simulation and modeling research. Model reduction can also ameliorate problems in the correlation of widely used finite-element analyses and test analysis models produced by excessive system complexity. Model Order Reduction Techniques explains and compares such methods focusing mainly on recent work in dynamic condensation techniques: - Compares the effectiveness of static, exact, dynamic, SEREP and iterative-dynamic condensation techniques in producing valid reduced-order mo...
Assessment of factors influencing finite element vertebral model predictions.
Jones, Alison C; Wilcox, Ruth K
2007-12-01
This study aimed to establish model construction and configuration procedures for future vertebral finite element analysis by studying convergence, sensitivity, and accuracy behaviors of semiautomatically generated models and comparing the results with manually generated models. During a previous study, six porcine vertebral bodies were imaged using a microcomputed tomography scanner and tested in axial compression to establish their stiffness and failure strength. Finite element models were built using a manual meshing method. In this study, the experimental agreement of those models was compared with that of semiautomatically generated models of the same six vertebrae. Both manually and semiautomatically generated models were assigned gray-scale-based, element-specific material properties. The convergence of the semiautomatically generated models was analyzed for the complete models along with material property and architecture control cases. A sensitivity study was also undertaken to test the reaction of the models to changes in material property values, architecture, and boundary conditions. In control cases, the element-specific material properties reduce the convergence of the models in comparison to homogeneous models. However, the full vertebral models showed strong convergence characteristics. The sensitivity study revealed a significant reaction to changes in architecture, boundary conditions, and load position, while the sensitivity to changes in material property values was proportional. The semiautomatically generated models produced stiffness and strength predictions of similar accuracy to the manually generated models with much shorter image segmentation and meshing times. Semiautomatic methods can provide a more rapid alternative to manual mesh generation techniques and produce vertebral models of similar accuracy. The representation of the boundary conditions, load position, and surrounding environment is crucial to the accurate prediction of the
Finite element and analytical models for twisted and coiled actuator
Tang, Xintian; Liu, Yingxiang; Li, Kai; Chen, Weishan; Zhao, Jianguo
2018-01-01
Twisted and coiled actuator (TCA) is a class of recently discovered artificial muscle, which is usually made by twisting and coiling polymer fibers into spring-like structures. It has been widely studied since discovery due to its impressive output characteristics and bright prospects. However, its mathematical models describing the actuation in response to the temperature are still not fully developed. It is known that the large tensile stroke is resulted from the untwisting of the twisted fiber when heated. Thus, the recovered torque during untwisting is a key parameter in the mathematical model. This paper presents a simplified model for the recovered torque of TCA. Finite element method is used for evaluating the thermal stress of the twisted fiber. Based on the results of the finite element analyses, the constitutive equations of twisted fibers are simplified to develop an analytic model of the recovered torque. Finally, the model of the recovered torque is used to predict the deformation of TCA under varying temperatures and validated against experimental results. This work will enhance our understanding of the deformation mechanism of TCAs, which will pave the way for the closed-loop position control.
The Blended Finite Element Method for Multi-fluid Plasma Modeling
2016-07-01
Briefing Charts 3. DATES COVERED (From - To) 07 June 2016 - 01 July 2016 4. TITLE AND SUBTITLE The Blended Finite Element Method for Multi-fluid Plasma...BLENDED FINITE ELEMENT METHOD FOR MULTI-FLUID PLASMA MODELING Éder M. Sousa1, Uri Shumlak2 1ERC INC., IN-SPACE PROPULSION BRANCH (RQRS) AIR FORCE RESEARCH...MULTI-FLUID PLASMA MODEL 2 BLENDED FINITE ELEMENT METHOD Blended Finite Element Method Nodal Continuous Galerkin Modal Discontinuous Galerkin Model
Finite-element model of the active organ of Corti
Elliott, Stephen J.; Baumgart, Johannes
2016-01-01
The cochlear amplifier that provides our hearing with its extraordinary sensitivity and selectivity is thought to be the result of an active biomechanical process within the sensory auditory organ, the organ of Corti. Although imaging techniques are developing rapidly, it is not currently possible, in a fully active cochlea, to obtain detailed measurements of the motion of individual elements within a cross section of the organ of Corti. This motion is predicted using a two-dimensional finite-element model. The various solid components are modelled using elastic elements, the outer hair cells (OHCs) as piezoelectric elements and the perilymph and endolymph as viscous and nearly incompressible fluid elements. The model is validated by comparison with existing measurements of the motions within the passive organ of Corti, calculated when it is driven either acoustically, by the fluid pressure or electrically, by excitation of the OHCs. The transverse basilar membrane (BM) motion and the shearing motion between the tectorial membrane and the reticular lamina are calculated for these two excitation modes. The fully active response of the BM to acoustic excitation is predicted using a linear superposition of the calculated responses and an assumed frequency response for the OHC feedback. PMID:26888950
Modelling of Shaft Orbiting with 3-D Solid Finite Elements
Directory of Open Access Journals (Sweden)
J. Yu
1999-01-01
Full Text Available A 3-D solid finite element model which can include bending, torsional, axial and other motions is proposed to analyse dynamic responses of shafts. For uniform shafts, this model shows consistency with beam theories when bending vibration is examined. For non-uniform shafts such as tapered ones, however, this model gives much more reliable and accurate results than beam theories which use an assumption that plane sections remain plane. Reduction procedures can be applied which involve only small matrix operations for such a system with a large number of degrees of freedom. The equations of motion have been consistently derived in a rotating frame. Shaft orbiting motion is then defined in this frame, giving a clear view of its trajectories. Forced responses due to excitation in the rotating frame have been examined to find some characteristics of the orbiting shaft. Resonant orbiting frequencies, i.e., natural frequencies of rotating shafts, can be determined in terms of the rotating or fixed frame. Trajectories of transverse displacements have been found to be varying with the forcing frequencies. At resonance, a uniform shaft will only have forward or backward orbiting motion with circular orbits. For other forcing frequencies, however, even a uniform shaft could present both forward and backward orbiting motions with non-circular orbits at different locations along its length. It is anticipated that modelling of shaft orbiting in the rotating frame with the proposed 3-D solid finite elements will lead to accurate dynamic stress evaluation.
Generalized Potential Energy Finite Elements for Modeling Molecular Nanostructures.
Chatzieleftheriou, Stavros; Adendorff, Matthew R; Lagaros, Nikos D
2016-10-24
The potential energy of molecules and nanostructures is commonly calculated in the molecular mechanics formalism by superimposing bonded and nonbonded atomic energy terms, i.e. bonds between two atoms, bond angles involving three atoms, dihedral angles involving four atoms, nonbonded terms expressing the Coulomb and Lennard-Jones interactions, etc. In this work a new, generalized numerical simulation is presented for studying the mechanical behavior of three-dimensional nanostructures at the atomic scale. The energy gradient and Hessian matrix of such assemblies are usually computed numerically; a potential energy finite element model is proposed herein where these two components are expressed analytically. In particular, generalized finite elements are developed that express the interactions among atoms in a manner equivalent to that invoked in simulations performed based on the molecular dynamics method. Thus, the global tangent stiffness matrix for any nanostructure is formed as an assembly of the generalized finite elements and is directly equivalent to the Hessian matrix of the potential energy. The advantages of the proposed model are identified in terms of both accuracy and computational efficiency. In the case of popular force fields (e.g., CHARMM), the computation of the Hessian matrix by implementing the proposed method is of the same order as that of the gradient. This analysis can be used to minimize the potential energy of molecular systems under nodal loads in order to derive constitutive laws for molecular systems where the entropy and solvent effects are neglected and can be approximated as solids, such as double stranded DNA nanostructures. In this context, the sequence dependent stretch modulus for some typical base pairs step is calculated.
Development of a finite element model of the human abdomen.
Lee, J B; Yang, K H
2001-11-01
Currently, three-dimensional finite element models of the human body have been developed for frequently injured anatomical regions such as the brain, chest, extremities and pelvis. While a few models of the human body include the abdomen, these models have tended to oversimplify the complexity of the abdominal region. As the first step in understanding abdominal injuries via numerical methods, a 3D finite element model of a 50(th) percentile male human abdomen (WSUHAM) has been developed and validated against experimental data obtained from two sets of side impact tests and a series of frontal impact tests. The model includes a detailed representation of the liver, spleen, kidneys, spine, skin and major blood vessels. Hollow organs, such as the esophagus, stomach, small and large intestines, gallbladder, bile ducts, ureters, rectum and adrenal glands are grouped into three bodybags in order to provide realistic inertial properties and to maintain the position of the solid organs in their appropriate locations. Using direct connections, the model was joined superiorly to a partial model of the human thorax, and inferiorly to models of the human pelvis and the lower extremities that have been previously developed. Material properties for various tissues of the abdomen were derived from the literature. Data obtained in a series of cadaveric pendulum impact tests conducted at Wayne State University (WSU), a series of lateral drop tests conducted at Association Peugeot-Renault (APR) and a series of cadaveric lower abdomen frontal impact tests conducted at WSU were used to validate the model. Results predicted by the model match these experimental data for various impact speeds, impactor masses and drop heights. Further study is still needed in order to fully validate WSUHAM before it can be used to assess various impact loading conditions associated with vehicular crashes.
Finite element modeling of Balsa wood structures under severe loadings
International Nuclear Information System (INIS)
Toson, B.; Pesque, J.J.; Viot, P.
2014-01-01
In order to compute, in various situations, the requirements for transporting packages using Balsa wood as an energy absorber, a constitutive model is needed that takes into account all of the specific characteristics of the wood, such as its anisotropy, compressibility, softening, densification, and strain rate dependence. Such a model must also include the treatment of rupture of the wood when it is in traction. The complete description of wood behavior is not sufficient: robustness is also necessary because this model has to work in presence of large deformations and of many other external nonlinear phenomena in the surrounding structures. We propose such a constitutive model that we have developed using the commercial finite element package ABAQUS. The necessary data were acquired through an extensive compilation of the existing literature with the augmentation of personal measurements. Numerous validation tests are presented that represent different impact situations that a transportation cask might endure. (authors)
Transient finite element modeling of functional electrical stimulation.
Filipovic, Nenad D; Peulic, Aleksandar S; Zdravkovic, Nebojsa D; Grbovic-Markovic, Vesna M; Jurisic-Skevin, Aleksandra J
2011-03-01
Transcutaneous functional electrical stimulation is commonly used for strengthening muscle. However, transient effects during stimulation are not yet well explored. The effect of an amplitude change of the stimulation can be described by static model, but there is no differency for different pulse duration. The aim of this study is to present the finite element (FE) model of a transient electrical stimulation on the forearm. Discrete FE equations were derived by using a standard Galerkin procedure. Different tissue conductive and dielectric properties are fitted using least square method and trial and error analysis from experimental measurement. This study showed that FE modeling of electrical stimulation can give the spatial-temporal distribution of applied current in the forearm. Three different cases were modeled with the same geometry but with different input of the current pulse, in order to fit the tissue properties by using transient FE analysis. All three cases were compared with experimental measurements of intramuscular voltage on one volunteer.
Computation of Schenberg response function by using finite element modelling
International Nuclear Information System (INIS)
Frajuca, C; Bortoli, F S; Magalhaes, N S
2016-01-01
Schenberg is a detector of gravitational waves resonant mass type, with a central frequency of operation of 3200 Hz. Transducers located on the surface of the resonating sphere, according to a distribution half-dodecahedron, are used to monitor a strain amplitude. The development of mechanical impedance matchers that act by increasing the coupling of the transducers with the sphere is a major challenge because of the high frequency and small in size. The objective of this work is to study the Schenberg response function obtained by finite element modeling (FEM). Finnaly, the result is compared with the result of the simplified model for mass spring type system modeling verifying if that is suitable for the determination of sensitivity detector, as the conclusion the both modeling give the same results. (paper)
OXYGEN PRESSURE REGULATOR DESIGN AND ANALYSIS THROUGH FINITE ELEMENT MODELING
Directory of Open Access Journals (Sweden)
Asterios KOSMARAS
2017-05-01
Full Text Available Oxygen production centers produce oxygen in high pressure that needs to be defused. A regulator is designed and analyzed in the current paper for medical use in oxygen production centers. This study aims to design a new oxygen pressure regulator and perform an analysis using Finite Element Modeling in order to evaluate its working principle. In the design procedure,the main elements and the operating principles of a pressure regulator are taking into account. The regulator is designed and simulations take place in order to assessthe proposed design. Stress analysis results are presented for the main body of the regulator, as well as, flow analysis to determine some important flow characteristics in the inlet and outlet of the regulator.
A nonlinear dynamic corotational finite element model for submerged pipes
de Vries, F. H.; Geijselaers, H. J. M.; van den Boogaard, A. H.; Huisman, A.
2017-12-01
A three dimensional finite element model is built to compute the motions of a pipe that is being laid on the seabed. This process is geometrically nonlinear, therefore co-rotational beam elements are used. The pipe is subject to static and dynamic forces. Static forces are due to gravity, current and buoyancy. The dynamic forces exerted by the water are incorporated using Morison’s equation. The dynamic motions are computed using implicit time integration. For this the Hilber-Hughes-Taylor method is selected. The Newton-Raphson iteration scheme is used to solve the equations in every time step. During laying, the pipe is connected to the pipe laying vessel, which is subject to wave motion. Response amplitude operators are used to determine the motions of the ship and thus the motions of the top end of the pipe.
Finite element modeling of electrically rectified piezoelectric energy harvesters
International Nuclear Information System (INIS)
Wu, P H; Shu, Y C
2015-01-01
Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique. (paper)
Finite element modeling of electrically rectified piezoelectric energy harvesters
Wu, P. H.; Shu, Y. C.
2015-09-01
Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique.
Finite element modeling of multipass GMA welds in steel plates
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-12-01
Distortions from gas metal arc (GMA) multipass welds of thick steel plates were measured in experiments and calculated using finite element analysis. Two- and three-dimensional finite element simulations were compared with the experimentally measured in-plane distortions in a 2-3/4 in. thick steel plate. Thermal analyses were performed using 2D models of the weld cross-section. These temperature histories were used for 2D and 3D mechanical analyses. Data for verification of thermal analyses included weld cross-sections, weld pool crater shape from power-off tests, and embedded and surface thermocouple temperature histories. Mechanical analyses were verified using caliper measurements of shrinkage transverse to the weld and strain gage measurements. Calculated in-plane shrinkage from the 3D model for 4 passes compared well with caliper measurements of a test specimen`s distortion. Two-dimensional mechanical analyses were not capable of predicting the accumulation of shrinkage occurring after the first pass.
Comparing finite elements and finite differences for developing diffusive models of glioma growth.
Roniotis, Alexandros; Marias, Kostas; Sakkalis, Vangelis; Stamatakos, Georgios; Zervakis, Michalis
2010-01-01
Glioma is the most aggressive type of brain tumor. Several mathematical models have been developed during the last two decades, towards simulating the mechanisms that govern the development of glioma. The most common models use the diffusion-reaction equation (DRE) for simulating the spatiotemporal variation of tumor cell concentration. The proposed diffusive models have mainly used finite differences (FDs) or finite elements (FEs) for the approximation of the solution of the partial differential DRE. This paper presents experimental results on the comparison of the FEs and FDs, especially focused on the glioma model case. It is studied how the different meshes of brain can affect computational consistency, simulation time and efficiency of the model. The experiments have been studied on a test case, for which there is a known algebraic expression of the solution. Thus, it is possible to calculate the error that the different models yield.
Active earth pressure model tests versus finite element analysis
Directory of Open Access Journals (Sweden)
Pietrzak Magdalena
2017-01-01
Full Text Available The purpose of the paper is to compare failure mechanisms observed in small scale model tests on granular sample in active state, and simulated by finite element method (FEM using Plaxis 2D software. Small scale model tests were performed on rectangular granular sample retained by a rigid wall. Deformation of the sample resulted from simple wall translation in the direction ‘from the soil” (active earth pressure state. Simple Coulomb-Mohr model for soil can be helpful in interpreting experimental findings in case of granular materials. It was found that the general alignment of strain localization pattern (failure mechanism may belong to macro scale features and be dominated by a test boundary conditions rather than the nature of the granular sample.
Active earth pressure model tests versus finite element analysis
Pietrzak, Magdalena
2017-06-01
The purpose of the paper is to compare failure mechanisms observed in small scale model tests on granular sample in active state, and simulated by finite element method (FEM) using Plaxis 2D software. Small scale model tests were performed on rectangular granular sample retained by a rigid wall. Deformation of the sample resulted from simple wall translation in the direction `from the soil" (active earth pressure state. Simple Coulomb-Mohr model for soil can be helpful in interpreting experimental findings in case of granular materials. It was found that the general alignment of strain localization pattern (failure mechanism) may belong to macro scale features and be dominated by a test boundary conditions rather than the nature of the granular sample.
Surface photovoltage measurements and finite element modeling of SAW devices.
Energy Technology Data Exchange (ETDEWEB)
Donnelly, Christine
2012-03-01
Over the course of a Summer 2011 internship with the MEMS department of Sandia National Laboratories, work was completed on two major projects. The first and main project of the summer involved taking surface photovoltage measurements for silicon samples, and using these measurements to determine surface recombination velocities and minority carrier diffusion lengths of the materials. The SPV method was used to fill gaps in the knowledge of material parameters that had not been determined successfully by other characterization methods. The second project involved creating a 2D finite element model of a surface acoustic wave device. A basic form of the model with the expected impedance response curve was completed, and the model is ready to be further developed for analysis of MEMS photonic resonator devices.
Finite Element Modeling of the Posterior Eye in Microgravity
Feola, Andrew; Raykin, Julia; Mulugeta, Lealem; Gleason, Rudolph; Myers, Jerry G.; Nelson, Emily S.; Samuels, Brian; Ethier, C. Ross
2015-01-01
Microgravity experienced during spaceflight affects astronauts in various ways, including weakened muscles and loss of bone density. Recently, visual impairment and intracranial pressure (VIIP) syndrome has become a major concern for space missions lasting longer than 30 days. Astronauts suffering from VIIP syndrome have changes in ocular anatomical and visual impairment that persist after returning to earth. It is hypothesized that a cephalad fluid shift in microgravity may increase the intracranial pressure (ICP), which leads to an altered biomechanical environment of the posterior globe and optic nerve sheath (ONS).Currently, there is a lack of knowledge of how elevated ICP may lead to vision impairment and connective tissue changes in VIIP. Our goal was to develop a finite element model to simulate the acute effects of elevated ICP on the posterior eye and optic nerve sheath. We used a finite element (FE) analysis approach to understand the response of the lamina cribrosa and optic nerve to the elevations in ICP thought to occur in microgravity and to identify which tissue components have the greatest impact on strain experienced by optic nerve head tissues.
Rigid finite element model of a cracked rotor
Kulesza, Zbigniew; Sawicki, Jerzy T.
2012-08-01
The article introduces a new mathematical model for the cracked rotating shaft. The model is based on the rigid finite element (RFE) method, which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. In this article, the RFE method is extended and adopted for the modeling of rotating machines. An original concept of crack modeling utilizing the RFE method is developed. The crack is presented as a set of spring-damping elements of variable stiffness connecting two sections of the shaft. An alternative approach for approximating the breathing mechanism of the crack is introduced. The approach is simple and allows one to intuitively and systematically prepare and analyze the model of a cracked rotor. The proposed method is illustrated with numerical and experimental results. The experiments conducted for the uncracked free-free rotor as well as the numerical results obtained with other software confirm the accuracy of the RFE model. The numerical analysis conducted for a set of cracked rotors has shown that, depending on the eccentricity and its angular location, the breathing behavior of the crack may take different forms. In spite of this, the frequency spectra for different cracks are almost identical. Due to its simplicity and numerous advantages, the proposed approach may be useful for rotor crack detection, especially if methods utilizing the mathematical model of the rotor are applied.
An implicit discontinuous Galerkin finite element model for water waves
van der Vegt, Jacobus J.W.; Ambati, V.R.; Bokhove, Onno
2005-01-01
We discuss a new higher order accurate discontinuous Galerkin finite element method for non-linear free surface gravity waves. The algorithm is based on an arbitrary Lagrangian Eulerian description of the flow field using deforming elements and a moving mesh, which makes it possible to represent
Modelling Convergence of Finite Element Analysis of Cantilever Beam
African Journals Online (AJOL)
Convergence studies are carried out by investigating the convergence of numerical results as the number of elements is increased. If convergence is not obtained, the engineer using the finite element method has absolutely no indication whether the results are indicative of a meaningful approximation to the correct solution ...
NON-LINEAR FINITE ELEMENT MODELING OF DEEP DRAWING PROCESS
Directory of Open Access Journals (Sweden)
Hasan YILDIZ
2004-03-01
Full Text Available Deep drawing process is one of the main procedures used in different branches of industry. Finding numerical solutions for determination of the mechanical behaviour of this process will save time and money. In die surfaces, which have complex geometries, it is hard to determine the effects of parameters of sheet metal forming. Some of these parameters are wrinkling, tearing, and determination of the flow of the thin sheet metal in the die and thickness change. However, the most difficult one is determination of material properties during plastic deformation. In this study, the effects of all these parameters are analyzed before producing the dies. The explicit non-linear finite element method is chosen to be used in the analysis. The numerical results obtained for non-linear material and contact models are also compared with the experiments. A good agreement between the numerical and the experimental results is obtained. The results obtained for the models are given in detail.
Heterogeneous modelling and finite element analysis of the femur
Directory of Open Access Journals (Sweden)
Zhang Binkai
2017-01-01
Full Text Available As the largest and longest bone in the human body, the femur has important research value and application prospects. This paper introduces a fast reconstruction method with Mimics and ANSYS software to realize the heterogeneous modelling of the femur according to Hu distribution of the CT series, and simulates it in various situations by finite element analysis to study the mechanical characteristics of the femur. The femoral heterogeneous model shows the distribution of bone mineral density and material properties, which can be used to assess the diagnosis and treatment of bone diseases. The stress concentration position of the femur under different conditions can be calculated by the simulation, which can provide reference for the design and material selection of prosthesis.
Ship Impact Study: Analytical Approaches and Finite Element Modeling
Directory of Open Access Journals (Sweden)
Pawel Woelke
2012-01-01
Full Text Available The current paper presents the results of a ship impact study conducted using various analytical approaches available in the literature with the results obtained from detailed finite element analysis. Considering a typical container vessel impacting a rigid wall with an initial speed of 10 knots, the study investigates the forces imparted on the struck obstacle, the energy dissipated through inelastic deformation, penetration, local deformation patterns, and local failure of the ship elements. The main objective of the paper is to study the accuracy and generality of the predictions of the vessel collision forces, obtained by means of analytical closed-form solutions, in reference to detailed finite element analyses. The results show that significant discrepancies between simplified analytical approaches and detailed finite element analyses can occur, depending on the specific impact scenarios under consideration.
An improved finite element model for craniofacial surgery simulation.
Wang, Shengzheng; Yang, Jie
2009-11-01
A novel approach is proposed for simulating the deformation of the facial soft tissues in the craniofacial surgery simulation. A nonlinear finite mixed-element model (NFM-EM) based on solid-shell elements and Lagrange principle of virtual work is proposed, which addresses the heterogeneity in geometry and material properties found in the soft tissues of the face. Moreover, after the investigation of the strain-potential models, the biomechanical characteristics of skin, muscles and fat are modeled with the most suitable material properties. In addition, an improved contact algorithm is used to compute the boundary conditions of the soft tissue model. The quantitative validation and the comparative results with other models proved the effectiveness of the approach on the simulation of complex soft tissues. The average absolute value of errors stays below 0.5 mm and the 95% percentiles of the distance map is less than 1.5 mm. NFM-EM promotes the accuracy and effectiveness of the soft tissue deformation, and the effective contact algorithm bridges the bone-related planning and the prediction of the target face.
A hybrid finite-difference and analytic element groundwater model
Haitjema, Henk M.; Feinstein, Daniel T.; Hunt, Randall J.; Gusyev, Maksym
2010-01-01
Regional finite-difference models tend to have large cell sizes, often on the order of 1–2 km on a side. Although the regional flow patterns in deeper formations may be adequately represented by such a model, the intricate surface water and groundwater interactions in the shallower layers are not. Several stream reaches and nearby wells may occur in a single cell, precluding any meaningful modeling of the surface water and groundwater interactions between the individual features. We propose to replace the upper MODFLOW layer or layers, in which the surface water and groundwater interactions occur, by an analytic element model (GFLOW) that does not employ a model grid; instead, it represents wells and surface waters directly by the use of point-sinks and line-sinks. For many practical cases it suffices to provide GFLOW with the vertical leakage rates calculated in the original coarse MODFLOW model in order to obtain a good representation of surface water and groundwater interactions. However, when the combined transmissivities in the deeper (MODFLOW) layers dominate, the accuracy of the GFLOW solution diminishes. For those cases, an iterative coupling procedure, whereby the leakages between the GFLOW and MODFLOW model are updated, appreciably improves the overall solution, albeit at considerable computational cost. The coupled GFLOW–MODFLOW model is applicable to relatively large areas, in many cases to the entire model domain, thus forming an attractive alternative to local grid refinement or inset models.
Finite Element Modeling and Optimization of Mechanical Joining Technology
Chenot, Jean-Loup; Bouchard, Pierre-Olivier; Massoni, Elisabeth; Mocellin, Katia; Lasne, Patrice
2011-05-01
The main scientific ingredients are recalled for developing a general finite element code and model accurately large plastic deformation of metallic materials during joining processes. Multi material contact is treated using the classical master and slave approach. Rupture may occur in joining processes or even be imposed in self piercing riveting and it must be predicted to evaluate the ultimate strength of joins. Damage is introduced with a generalized uncoupled damage criterion, or by utilizing a coupled formulation with a Lemaître law. Several joining processes are briefly analyzed in term of specific scientific issues: riveting, self piercing riveting, clinching, crimping, hemming and screwing. It is shown that not only the joining process can be successfully simulated and optimized, but also the strength of the assembly can be predicted in tension and in shearing.
Finite element modelling of cornea mechanics: a review
Directory of Open Access Journals (Sweden)
Talisa Mohammad Nejad
2014-01-01
Full Text Available The cornea is a transparent tissue in front of the eye that refracts light and facilitates vision. A slight change in the geometry of the cornea remarkably affects the optical power. Because of this sensitivity, biomechanical study of the cornea can reveal much about its performance and function. In vivo and in vitro studies have been conducted to investigate the mechanics of the cornea and determine its characteristics. Numerical techniques such as the finite element method (FEM have been extensively implemented as effective and noninvasive methods for analyzing corneal mechanics and possible disorders. This article reviews the use of FEM for assessing the mechanical behavior of the cornea. Different applications of FEM in corneal disease studies, surgical predictions, impact simulations, and clinical applications have been reviewed. Some suggestions for the future of this type of modeling in the area of corneal mechanics are also discussed.
Finite Element Modelling of Cold Formed Stainless Steel Columns
Directory of Open Access Journals (Sweden)
M. Macdonald
2005-01-01
Full Text Available This paper describes the results obtained from a finite element investigation into the load capacity of column members of lipped channel cross-section, cold formed from Type 304 stainless steel, subjected to concentric and eccentric compression loading. The main aims of this investigation were to determine the effects which the non-linearity of the stress-strain behaviour of the material would have on the column behaviour under concentric or eccentric loading. Stress-strain curves derived from tests and design codes are incorporated into non-linear finite element analyses of eccentrically loaded columns and the results obtained are compared with those obtained on the basis of experiments on stainless steel channel columns with the same properties and dimensions. Comparisons of the finite element results and the test results are also made with existing design specifications and conclusions are drawn on the basis of the comparisons.
FINITE-ELEMENT MODELING OF WELDED X-SHAPED JOINT
Directory of Open Access Journals (Sweden)
V. V. Kyzniatsova
2014-01-01
Full Text Available The paper presents a modeling of non-stationary processes while making arc welding in the shielding gas medium of X-shaped joints which consist of re-bars having various diameters. Changes and specific features of stress-strain state in the X-shaped joint have been considered in the paper. Calculations are as much as possible approximated to a real situation: a 3D-geometrical and finite-element model is used, the problem is considered as elastic and contact one with due account of power loading. An analysis of the welded assembly consisting of re-bars with diameter of 4-10 mm has been performed using a finite element method. Computation of a welded connection with due consideration of geometrical nonlinearity has been done in the paper. It has been shown that tensile of re-bars under load causes uneven stress distribution in a welded joint and their significant concentration is observed at crossing points from the welded joint to a base metal. An analysis of the obtained equivalent stresses at nodes and details of the welded joint structure has shown that they did not exceed permissible values for all diameters in case of the considered loading conditions. A comparison of stress values calculated has been carried out in accordance with the proposed method and experimentally obtained data. It has been revealed that application of tensile load (determined experimentally to the connection stress values at the connection and welded joint boundary reach an yield strength and subsequently it causes destruction of the connection. It has been established that the margin of safety for such type of connections is averagely equal from 30 to 60 %. The submitted calculated data are in full agreement with experimental data that proves correctness in selection of calculation schemes and loads.
Finite Elements Modeling in Diagnostics of Small Closed Pneumothorax.
Lorkowski, J; Mrzygłód, M; Grzegorowska, O
2015-01-01
Posttraumatic pneumothorax still remains to be a serious clinical problem and requires a comprehensive diagnostic and monitoring during treatment. The aim of this paper is to present a computer method of modeling of small closed pneumothorax. Radiological images of 34 patients of both sexes with small closed pneumothorax were taken into consideration. The control group consisted of X-rays of 22 patients treated because of tension pneumothorax. In every single case the model was correlated with the clinical manifestations. The procedure of computational rapid analysis (CRA) for in silico analysis of surgical intervention was introduced. It included implementation of computerize tomography images and their automatic conversion into 3D finite elements model (FEM). In order to segmentize the 3D model, an intelligent procedure of domain recognition was used. In the final step, a computer simulation project of fluid-structure interaction was built, using the ANSYS\\Workbench environment of multi-physics analysis. The FEM model and computer simulation project were employed in the analysis in order to optimize surgical intervention. The model worked out well and was compatible with the clinical manifestations of pneumothorax. We conclude that the created FEM model is a promising tool for facilitation of diagnostic procedures and prognosis of treatment in the case of small closed pneumothorax.
Design Through Manufacturing: The Solid Model - Finite Element Analysis Interface
Rubin, Carol
2003-01-01
State-of-the-art computer aided design (CAD) presently affords engineers the opportunity to create solid models of machine parts which reflect every detail of the finished product. Ideally, these models should fulfill two very important functions: (1) they must provide numerical control information for automated manufacturing of precision parts, and (2) they must enable analysts to easily evaluate the stress levels (using finite element analysis - FEA) for all structurally significant parts used in space missions. Today's state-of-the-art CAD programs perform function (1) very well, providing an excellent model for precision manufacturing. But they do not provide a straightforward and simple means of automating the translation from CAD to FEA models, especially for aircraft-type structures. The research performed during the fellowship period investigated the transition process from the solid CAD model to the FEA stress analysis model with the final goal of creating an automatic interface between the two. During the period of the fellowship a detailed multi-year program for the development of such an interface was created. The ultimate goal of this program will be the development of a fully parameterized automatic ProE/FEA translator for parts and assemblies, with the incorporation of data base management into the solution, and ultimately including computational fluid dynamics and thermal modeling in the interface.
The finite-difference and finite-element modeling of seismic wave propagation and earthquake motion
International Nuclear Information System (INIS)
Moczo, P.; Kristek, J.; Pazak, P.; Balazovjech, M.; Moczo, P.; Kristek, J.; Galis, M.
2007-01-01
Numerical modeling of seismic wave propagation and earthquake motion is an irreplaceable tool in investigation of the Earth's structure, processes in the Earth, and particularly earthquake phenomena. Among various numerical methods, the finite-difference method is the dominant method in the modeling of earthquake motion. Moreover, it is becoming more important in the seismic exploration and structural modeling. At the same time we are convinced that the best time of the finite-difference method in seismology is in the future. This monograph provides tutorial and detailed introduction to the application of the finite difference (FD), finite-element (FE), and hybrid FD-FE methods to the modeling of seismic wave propagation and earthquake motion. The text does not cover all topics and aspects of the methods. We focus on those to which we have contributed. We present alternative formulations of equation of motion for a smooth elastic continuum. We then develop alternative formulations for a canonical problem with a welded material interface and free surface. We continue with a model of an earthquake source. We complete the general theoretical introduction by a chapter on the constitutive laws for elastic and viscoelastic media, and brief review of strong formulations of the equation of motion. What follows is a block of chapters on the finite-difference and finite-element methods. We develop FD targets for the free surface and welded material interface. We then present various FD schemes for a smooth continuum, free surface, and welded interface. We focus on the staggered-grid and mainly optimally-accurate FD schemes. We also present alternative formulations of the FE method. We include the FD and FE implementations of the traction-at-split-nodes method for simulation of dynamic rupture propagation. The FD modeling is applied to the model of the deep sedimentary Grenoble basin, France. The FD and FE methods are combined in the hybrid FD-FE method. The hybrid
Finite Element Models for Electron Beam Freeform Fabrication Process
Chandra, Umesh
2012-01-01
Electron beam freeform fabrication (EBF3) is a member of an emerging class of direct manufacturing processes known as solid freeform fabrication (SFF); another member of the class is the laser deposition process. Successful application of the EBF3 process requires precise control of a number of process parameters such as the EB power, speed, and metal feed rate in order to ensure thermal management; good fusion between the substrate and the first layer and between successive layers; minimize part distortion and residual stresses; and control the microstructure of the finished product. This is the only effort thus far that has addressed computer simulation of the EBF3 process. The models developed in this effort can assist in reducing the number of trials in the laboratory or on the shop floor while making high-quality parts. With some modifications, their use can be further extended to the simulation of laser, TIG (tungsten inert gas), and other deposition processes. A solid mechanics-based finite element code, ABAQUS, was chosen as the primary engine in developing these models whereas a computational fluid dynamics (CFD) code, Fluent, was used in a support role. Several innovative concepts were developed, some of which are highlighted below. These concepts were implemented in a number of new computer models either in the form of stand-alone programs or as user subroutines for ABAQUS and Fluent codes. A database of thermo-physical, mechanical, fluid, and metallurgical properties of stainless steel 304 was developed. Computing models for Gaussian and raster modes of the electron beam heat input were developed. Also, new schemes were devised to account for the heat sink effect during the deposition process. These innovations, and others, lead to improved models for thermal management and prediction of transient/residual stresses and distortions. Two approaches for the prediction of microstructure were pursued. The first was an empirical approach involving the
Adaptive unstructured meshes for finite element ocean modelling
Power, P. W.; Pain, C. C.; Piggott, M. D.; Marshall, D. P.; Fang, F.; Umpleby, A. P.; de Oliveira, C. R. E.; Goddard, A. J. H.
2003-04-01
Flow in the world's oceans occurs at a wide range of spatial scales, from micro-metres to mega-metres. In particular, regions of intense flow are often highly localised, for example Western Boundary Currents. Conventional numerical ocean models generally use static meshes. The Imperial College Ocean Model (ICOM) uses advanced finite element methods to evolve the mesh to follow regions of intense flow, where high resolution may be required. Coarser resolution can be used in other areas of the flow domain. Evolution of the unstructured mesh is achieved by the use of a variety of error norms which control a self-adaptive anisotrophic meshing algorithm. The objective of this work is a reduction in computational cost, ensuring areas of fine resolution are used only where and when they are required. In this work we present some examples of an error measure being used to obtain high-quality solutions to a set of benchmark problems, for example flow over a seamount and a wind driven gyre, while using a minimal number of elements. The long term objective of this work is to define a rigorous self-adaptive technique for use in an Oceanographic context, and we present plans for the implimentation of a sensitivity based error measure.
Finite element analysis of osteoporosis models based on synchrotron radiation
Xu, W.; Xu, J.; Zhao, J.; Sun, J.
2016-04-01
With growing pressure of social aging, China has to face the increasing population of osteoporosis patients as well as the whole world. Recently synchrotron radiation has become an essential tool for biomedical exploration with advantage of high resolution and high stability. In order to study characteristic changes in different stages of primary osteoporosis, this research focused on the different periods of osteoporosis of rats based on synchrotron radiation. Both bone histomorphometry analysis and finite element analysis were then carried on according to the reconstructed three dimensional models. Finally, the changes of bone tissue in different periods were compared quantitatively. Histomorphometry analysis showed that the structure of the trabecular in osteoporosis degraded as the bone volume decreased. For femurs, the bone volume fraction (Bone volume/ Total volume, BV/TV) decreased from 69% to 43%. That led to the increase of the thickness of trabecular separation (from 45.05μ m to 97.09μ m) and the reduction of the number of trabecular (from 7.99 mm-1 to 5.97mm-1). Simulation of various mechanical tests with finite element analysis (FEA) indicated that, with the exacerbation of osteoporosis, the bones' ability of resistance to compression, bending and torsion gradually became weaker. The compression stiffness of femurs decreased from 1770.96 Fμ m-1 to 697.41 Fμ m-1, the bending and torsion stiffness were from 1390.80 Fμ m-1 to 566.11 Fμ m-1 and from 2957.28N.m/o to 691.31 N.m/o respectively, indicated the decrease of bone strength, and it matched the histomorphometry analysis. This study suggested that FEA and synchrotron radiation were excellent methods for analysing bone strength conbined with histomorphometry analysis.
Lower extremity finite element model for crash simulation
Energy Technology Data Exchange (ETDEWEB)
Schauer, D.A.; Perfect, S.A.
1996-03-01
A lower extremity model has been developed to study occupant injury mechanisms of the major bones and ligamentous soft tissues resulting from vehicle collisions. The model is based on anatomically correct digitized bone surfaces of the pelvis, femur, patella and the tibia. Many muscles, tendons and ligaments were incrementally added to the basic bone model. We have simulated two types of occupant loading that occur in a crash environment using a non-linear large deformation finite element code. The modeling approach assumed that the leg was passive during its response to the excitation, that is, no active muscular contraction and therefore no active change in limb stiffness. The approach recognized that the most important contributions of the muscles to the lower extremity response are their ability to define and modify the impedance of the limb. When nonlinear material behavior in a component of the leg model was deemed important to response, a nonlinear constitutive model was incorporated. The accuracy of these assumptions can be verified only through a review of analysis results and careful comparison with test data. As currently defined, the model meets the objective for which it was created. Much work remains to be done, both from modeling and analysis perspectives, before the model can be considered complete. The model implements a modeling philosophy that can accurately capture both kinematic and kinetic response of the lower limb. We have demonstrated that the lower extremity model is a valuable tool for understanding the injury processes and mechanisms. We are now in a position to extend the computer simulation to investigate the clinical fracture patterns observed in actual crashes. Additional experience with this model will enable us to make a statement on what measures are needed to significantly reduce lower extremity injuries in vehicle crashes. 6 refs.
Finite element code development for modeling detonation of HMX composites
Duran, Adam V.; Sundararaghavan, Veera
2017-01-01
In this work, we present a hydrodynamics code for modeling shock and detonation waves in HMX. A stable efficient solution strategy based on a Taylor-Galerkin finite element (FE) discretization was developed to solve the reactive Euler equations. In our code, well calibrated equations of state for the solid unreacted material and gaseous reaction products have been implemented, along with a chemical reaction scheme and a mixing rule to define the properties of partially reacted states. A linear Gruneisen equation of state was employed for the unreacted HMX calibrated from experiments. The JWL form was used to model the EOS of gaseous reaction products. It is assumed that the unreacted explosive and reaction products are in both pressure and temperature equilibrium. The overall specific volume and internal energy was computed using the rule of mixtures. Arrhenius kinetics scheme was integrated to model the chemical reactions. A locally controlled dissipation was introduced that induces a non-oscillatory stabilized scheme for the shock front. The FE model was validated using analytical solutions for SOD shock and ZND strong detonation models. Benchmark problems are presented for geometries in which a single HMX crystal is subjected to a shock condition.
Vibration Response of Multi Storey Building Using Finite Element Modelling
Chik, T. N. T.; Zakaria, M. F.; Remali, M. A.; Yusoff, N. A.
2016-07-01
Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.
Finite element modeling to analyze TEER values across silicon nanomembranes.
Khire, Tejas S; Nehilla, Barrett J; Getpreecharsawas, Jirachai; Gracheva, Maria E; Waugh, Richard E; McGrath, James L
2018-01-05
Silicon nanomembranes are ultrathin, highly permeable, optically transparent and biocompatible substrates for the construction of barrier tissue models. Trans-epithelial/endothelial electrical resistance (TEER) is often used as a non-invasive, sensitive and quantitative technique to assess barrier function. The current study characterizes the electrical behavior of devices featuring silicon nanomembranes to facilitate their application in TEER studies. In conventional practice with commercial systems, raw resistance values are multiplied by the area of the membrane supporting cell growth to normalize TEER measurements. We demonstrate that under most circumstances, this multiplication does not 'normalize' TEER values as is assumed, and that the assumption is worse if applied to nanomembrane chips with a limited active area. To compare the TEER values from nanomembrane devices to those obtained from conventional polymer track-etched (TE) membranes, we develop finite element models (FEM) of the electrical behavior of the two membrane systems. Using FEM and parallel cell-culture experiments on both types of membranes, we successfully model the evolution of resistance values during the growth of endothelial monolayers. Further, by exploring the relationship between the models we develop a 'correction' function, which when applied to nanomembrane TEER, maps to experiments on conventional TE membranes. In summary, our work advances the the utility of silicon nanomembranes as substrates for barrier tissue models by developing an interpretation of TEER values compatible with conventional systems.
Customized Finite Element Modelling of the Human Cornea.
Simonini, Irene; Pandolfi, Anna
2015-01-01
To construct patient-specific solid models of human cornea from ocular topographer data, to increase the accuracy of the biomechanical and optical estimate of the changes in refractive power and stress caused by photorefractive keratectomy (PRK). Corneal elevation maps of five human eyes were taken with a rotating Scheimpflug camera combined with a Placido disk before and after refractive surgery. Patient-specific solid models were created and discretized in finite elements to estimate the corneal strain and stress fields in preoperative and postoperative configurations and derive the refractive parameters of the cornea. Patient-specific geometrical models of the cornea allow for the creation of personalized refractive maps at different levels of IOP. Thinned postoperative corneas show a higher stress gradient across the thickness and higher sensitivity of all geometrical and refractive parameters to the fluctuation of the IOP. Patient-specific numerical models of the cornea can provide accurate quantitative information on the refractive properties of the cornea under different levels of IOP and describe the change of the stress state of the cornea due to refractive surgery (PRK). Patient-specific models can be used as indicators of feasibility before performing the surgery.
Modelling cell motility and chemotaxis with evolving surface finite elements.
Elliott, Charles M; Stinner, Björn; Venkataraman, Chandrasekhar
2012-11-07
We present a mathematical and a computational framework for the modelling of cell motility. The cell membrane is represented by an evolving surface, with the movement of the cell determined by the interaction of various forces that act normal to the surface. We consider external forces such as those that may arise owing to inhomogeneities in the medium and a pressure that constrains the enclosed volume, as well as internal forces that arise from the reaction of the cells' surface to stretching and bending. We also consider a protrusive force associated with a reaction-diffusion system (RDS) posed on the cell membrane, with cell polarization modelled by this surface RDS. The computational method is based on an evolving surface finite-element method. The general method can account for the large deformations that arise in cell motility and allows the simulation of cell migration in three dimensions. We illustrate applications of the proposed modelling framework and numerical method by reporting on numerical simulations of a model for eukaryotic chemotaxis and a model for the persistent movement of keratocytes in two and three space dimensions. Movies of the simulated cells can be obtained from http://homepages.warwick.ac.uk/∼maskae/CV_Warwick/Chemotaxis.html.
Calibration under uncertainty for finite element models of masonry monuments
Energy Technology Data Exchange (ETDEWEB)
Atamturktur, Sezer,; Hemez, Francois,; Unal, Cetin
2010-02-01
Historical unreinforced masonry buildings often include features such as load bearing unreinforced masonry vaults and their supporting framework of piers, fill, buttresses, and walls. The masonry vaults of such buildings are among the most vulnerable structural components and certainly among the most challenging to analyze. The versatility of finite element (FE) analyses in incorporating various constitutive laws, as well as practically all geometric configurations, has resulted in the widespread use of the FE method for the analysis of complex unreinforced masonry structures over the last three decades. However, an FE model is only as accurate as its input parameters, and there are two fundamental challenges while defining FE model input parameters: (1) material properties and (2) support conditions. The difficulties in defining these two aspects of the FE model arise from the lack of knowledge in the common engineering understanding of masonry behavior. As a result, engineers are unable to define these FE model input parameters with certainty, and, inevitably, uncertainties are introduced to the FE model.
FEWA: a Finite Element model of Water flow through Aquifers
International Nuclear Information System (INIS)
Yeh, G.T.; Huff, D.D.
1983-11-01
This report documents the implementation and demonstration of a Finite Element model of Water flow through Aquifers (FEWA). The particular features of FEWA are its versatility and flexibility to deal with as many real-world problems as possible. Point as well as distributed sources/sinks are included to represent recharges/pumpings and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Source/sink strength over each element and node, hydraulic head at each Dirichlet boundary node, and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution method for the matrix equation approximating the partial differential equation of groundwater flow. FEWA also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. It is then demonstrated by two examples of how the model can be applied to heterogeneous and anisotropic aquifers with transient boundary conditions, time-dependent sources/sinks, and confining aquitards for a confined aquifer of variable thickness and for a free surface problem in an unconfined aquifer, respectively. 20 references, 25 figures, 8 tables
An implicit discontinuous Galerkin finite element model for water waves
van der Vegt, Jacobus J.W.; Tomar, S.K.; Yao, Z.H.; Yuan, M.W.; Zhong, W.X.
2004-01-01
An overview is given of a discontinuous Galerkin finite element method for linear free surface water waves. The method uses an implicit time integration method which is unconditionally stable and does not suffer from the frequently encountered mesh dependent saw-tooth type instability at the free
Finite element model to study two dimensional unsteady state ...
African Journals Online (AJOL)
Kunal Pathak
2015-10-20
Oct 20, 2015 ... Excess buffer;. Finite element method. Abstract The calcium signaling plays a crucial role in expansion and contraction of cardiac myo- cytes. This calcium signaling is achieved by calcium diffusion, buffering mechanisms and influx in cardiac myocytes. The various calcium distribution patterns required for ...
Can finite element models detect clinically inferior cemented hip implants?
Stolk, J.; Maher, S.A.; Verdonschot, N.J.J.; Prendergast, P.J.; Huiskes, R.
2003-01-01
Rigorous preclinical testing of cemented hip prostheses against the damage accumulation failure scenario will reduce the incidence of aseptic loosening. For that purpose, a finite element simulation is proposed that predicts damage accumulation in the cement mantle and prosthetic migration. If the
Finite element based model of parchment coffee drying
Directory of Open Access Journals (Sweden)
Preeda Prakotmak
2015-03-01
Full Text Available Heat and mass transfer in the parchment coffee during convective drying represents a complicated phenomena since it is important to consider not only the transport phenomena during drying but also the various changes of the drying materials. In order to describe drying of biomaterials adequately, a suitable mathematical model is needed. The aim of the present study was to develop a 3-D finite element model to simulate the transport of heat and mass within parchment coffee during the thin layer drying. Thin layer drying experiments of coffee bean and parchment coffee were conducted in the temperature range of 40-60o C, the relative humidity ranged from 14 to 28% and drying air velocity of 1.4 m/s. The moisture diffusivities in different coffee’s components (parchment and coffee bean were determined by minimizing the RMSE between the predicted and the experimental data of moisture contents. The simulated results showed that the moisture diffusivities of coffee bean were three orders of magnitude higher than those of the parchment. Moisture diffusivities of coffee components were found to significantly increase (P<0.05 with the increase in drying air temperature and were expressed by Arrhenius-type equations. Moreover, the model was also used to predict the moisture gradient in coffee bean during drying. The model simulates the moisture contents in different components of parchment coffee well and it provides a better understanding of the transport processes in the different components of the parchment coffee
Finite element modeling of nanotube structures linear and non-linear models
Awang, Mokhtar; Muhammad, Ibrahim Dauda
2016-01-01
This book presents a new approach to modeling carbon structures such as graphene and carbon nanotubes using finite element methods, and addresses the latest advances in numerical studies for these materials. Based on the available findings, the book develops an effective finite element approach for modeling the structure and the deformation of grapheme-based materials. Further, modeling processing for single-walled and multi-walled carbon nanotubes is demonstrated in detail.
Physical Constraint Finite Element Model for Medical Image Registration.
Directory of Open Access Journals (Sweden)
Jingya Zhang
Full Text Available Due to being derived from linear assumption, most elastic body based non-rigid image registration algorithms are facing challenges for soft tissues with complex nonlinear behavior and with large deformations. To take into account the geometric nonlinearity of soft tissues, we propose a registration algorithm on the basis of Newtonian differential equation. The material behavior of soft tissues is modeled as St. Venant-Kirchhoff elasticity, and the nonlinearity of the continuum represents the quadratic term of the deformation gradient under the Green- St.Venant strain. In our algorithm, the elastic force is formulated as the derivative of the deformation energy with respect to the nodal displacement vectors of the finite element; the external force is determined by the registration similarity gradient flow which drives the floating image deforming to the equilibrium condition. We compared our approach to three other models: 1 the conventional linear elastic finite element model (FEM; 2 the dynamic elastic FEM; 3 the robust block matching (RBM method. The registration accuracy was measured using three similarities: MSD (Mean Square Difference, NC (Normalized Correlation and NMI (Normalized Mutual Information, and was also measured using the mean and max distance between the ground seeds and corresponding ones after registration. We validated our method on 60 image pairs including 30 medical image pairs with artificial deformation and 30 clinical image pairs for both the chest chemotherapy treatment in different periods and brain MRI normalization. Our method achieved a distance error of 0.320±0.138 mm in x direction and 0.326±0.111 mm in y direction, MSD of 41.96±13.74, NC of 0.9958±0.0019, NMI of 1.2962±0.0114 for images with large artificial deformations; and average NC of 0.9622±0.008 and NMI of 1.2764±0.0089 for the real clinical cases. Student's t-test demonstrated that our model statistically outperformed the other methods in
Physical Constraint Finite Element Model for Medical Image Registration.
Zhang, Jingya; Wang, Jiajun; Wang, Xiuying; Gao, Xin; Feng, Dagan
2015-01-01
Due to being derived from linear assumption, most elastic body based non-rigid image registration algorithms are facing challenges for soft tissues with complex nonlinear behavior and with large deformations. To take into account the geometric nonlinearity of soft tissues, we propose a registration algorithm on the basis of Newtonian differential equation. The material behavior of soft tissues is modeled as St. Venant-Kirchhoff elasticity, and the nonlinearity of the continuum represents the quadratic term of the deformation gradient under the Green- St.Venant strain. In our algorithm, the elastic force is formulated as the derivative of the deformation energy with respect to the nodal displacement vectors of the finite element; the external force is determined by the registration similarity gradient flow which drives the floating image deforming to the equilibrium condition. We compared our approach to three other models: 1) the conventional linear elastic finite element model (FEM); 2) the dynamic elastic FEM; 3) the robust block matching (RBM) method. The registration accuracy was measured using three similarities: MSD (Mean Square Difference), NC (Normalized Correlation) and NMI (Normalized Mutual Information), and was also measured using the mean and max distance between the ground seeds and corresponding ones after registration. We validated our method on 60 image pairs including 30 medical image pairs with artificial deformation and 30 clinical image pairs for both the chest chemotherapy treatment in different periods and brain MRI normalization. Our method achieved a distance error of 0.320±0.138 mm in x direction and 0.326±0.111 mm in y direction, MSD of 41.96±13.74, NC of 0.9958±0.0019, NMI of 1.2962±0.0114 for images with large artificial deformations; and average NC of 0.9622±0.008 and NMI of 1.2764±0.0089 for the real clinical cases. Student's t-test demonstrated that our model statistically outperformed the other methods in comparison (p
DEFF Research Database (Denmark)
Carstensen, Josephine Voigt; Jomaas, Grunde; Pankaj, Pankaj
2013-01-01
One of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain-softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts to...... variation in values. Application of the evaluated fracture energy values shows that these impose severe element size and reinforcement ratio limits. The effect of the limits is illustrated for a RC specimen. © 2013 American Society of Civil Engineers.......One of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain-softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts...
Investigation of faulted tunnel models by combined photoelasticity and finite element analysis
International Nuclear Information System (INIS)
Ladkany, S.G.; Huang, Y.
1994-01-01
Models of square and circular tunnels with short faults cutting through their surfaces are investigated by photoelasticity. These models, when duplicated by finite element analysis can predict the stress states of square or circular faulted tunnels adequately. Finite element analysis, using gap elements, may be used to investigate full size faulted tunnel system
A Computational Approach for Automated Posturing of a Human Finite Element Model
2016-07-01
Std. Z39.18 July 2016 Memorandum Report A Computational Approach for Automated Posturing of a Human Finite Element Model Justin McKee and Adam...ARL-MR-0934• JULY 2016 US Army Research Laboratory A Computational Approach for Automated Posturing of a Human Finite ElementModel by Justin McKee... Automated Posturing of a Human Finite ElementModel by Justin McKee Bennett Aerospace, Inc., Cary, NC Adam Sokolow Weapons and Materials Research
Synthetic Modifications In the Frequency Domain for Finite Element Model Update and Damage Detection
2017-09-01
Aeronautical Society , 24, pp. 590–591. [23] Fritzen, C., and Kiefer, T., 1992, “Localization and Correction of Errors in Finite Element Models Based on...MODIFICATIONS IN THE FREQUENCY DOMAIN FOR FINITE ELEMENT MODEL UPDATE AND DAMAGE DETECTION by Ryun J. C. Konze September 2017 Thesis Advisor...FINITE ELEMENT MODEL UPDATE AND DAMAGE DETECTION 5. FUNDING NUMBERS 6. AUTHOR(S) Ryun J. C. Konze 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES
Predicting target displacements using ultrasound elastography and finite element modeling.
op den Buijs, Jorn; Hansen, Hendrik H G; Lopata, Richard G P; de Korte, Chris L; Misra, Sarthak
2011-11-01
Soft tissue displacements during minimally invasive surgical procedures may cause target motion and subsequent misplacement of the surgical tool. A technique is presented to predict target displacements using a combination of ultrasound elastography and finite element (FE) modeling. A cubic gelatin/agar phantom with stiff targets was manufactured to obtain pre- and post-loading ultrasound radio frequency (RF) data from a linear array transducer. The RF data were used to compute displacement and strain images, from which the distribution of elasticity was reconstructed using an inverse FE-based approach. The FE model was subsequently used to predict target displacements upon application of different boundary and loading conditions to the phantom. The influence of geometry was investigated by application of the technique to a breast-shaped phantom. The distribution of elasticity in the phantoms as determined from the strain distribution agreed well with results from mechanical testing. Upon application of different boundary and loading conditions to the cubic phantom, the FE model-predicted target motion were consistent with ultrasound measurements. The FE-based approach could also accurately predict the displacement of the target upon compression and indentation of the breast-shaped phantom. This study provides experimental evidence that organ geometry and boundary conditions surrounding the organ are important factors influencing target motion. In future work, the technique presented in this paper could be used for preoperative planning of minimally invasive surgical interventions.
Validation of a parametric finite element human femur model.
Klein, Katelyn F; Hu, Jingwen; Reed, Matthew P; Schneider, Lawrence W; Rupp, Jonathan D
2017-05-19
Finite element (FE) models with geometry and material properties that are parametric with subject descriptors, such as age and body shape/size, are being developed to incorporate population variability into crash simulations. However, the validation methods currently being used with these parametric models do not assess whether model predictions are reasonable in the space over which the model is intended to be used. This study presents a parametric model of the femur and applies a unique validation paradigm to this parametric femur model that characterizes whether model predictions reproduce experimentally observed trends. FE models of male and female femurs with geometries that are parametric with age, femur length, and body mass index (BMI) were developed based on existing statistical models that predict femur geometry. These parametric FE femur models were validated by comparing responses from combined loading tests of femoral shafts to simulation results from FE models of the corresponding femoral shafts whose geometry was predicted using the associated age, femur length, and BMI. The effects of subject variables on model responses were also compared with trends in the experimental data set by fitting similarly parameterized statistical models to both the results of the experimental data and the corresponding FE model results and then comparing fitted model coefficients for the experimental and predicted data sets. The average error in impact force at experimental failure for the parametric models was 5%. The coefficients of a statistical model fit to simulation data were within one standard error of the coefficients of a similarly parameterized model of the experimental data except for the age parameter, likely because material properties used in simulations were not varied with specimen age. In simulations to explore the effects of femur length, BMI, and age on impact response, only BMI significantly affected response for both men and women, with increasing
Finite element modelling of the dynamics of groovy ball bearings
Directory of Open Access Journals (Sweden)
Ajala Olamide
2018-01-01
Full Text Available Geometry modified thrust bearings exposed to rolling and sliding contact are subjected to wear and localized frictional heating caused by relative slip between the two sliding surfaces. This leads to a rise in temperature, thermal stresses and changes in the elastic and plastic strength and physical properties of the material. The changes in the properties in turn alter the stress state, the displacement field, life and reliability of the bearing. Hence, a finite-element model is created to study the dynamics of groovy thrust bearing. In this paper, Hertz contact theory and numerical method are used to simulate the dynamics and kinematics of groovy ball bearings. The optimal loading parameters are identified in this study based on the analysis of the system responses and properties. The results of the numerical analysis and validation are presented. The numerical analysis proves the concept of transforming rotational motion into axial oscillation and demonstrates the capabilities of the numerical simulation to accurately model the dynamics of the groovy ball bearing.
2017-11-01
FE finite element MAC modal assurance criteria SAE Society of Automotive Engineers SDIC stereo-digital image correlation SLAD Survivability...ARL-TR-8224 ● NOV 2017 US Army Research Laboratory Validating a Finite Element Model of a Structure Subjected to Mine Blast with...NOV 2017 US Army Research Laboratory Validating a Finite Element Model of a Structure Subjected to Mine Blast with Experimental Modal
International Nuclear Information System (INIS)
Lee, Byeong Hae
1992-02-01
This book gives descriptions of basic finite element method, which includes basic finite element method and data, black box, writing of data, definition of VECTOR, definition of matrix, matrix and multiplication of matrix, addition of matrix, and unit matrix, conception of hardness matrix like spring power and displacement, governed equation of an elastic body, finite element method, Fortran method and programming such as composition of computer, order of programming and data card and Fortran card, finite element program and application of nonelastic problem.
Finite element modelling of vocal tract changes after voice therapy
Directory of Open Access Journals (Sweden)
Vampola T.
2011-06-01
Full Text Available Two 3D finite element (FE models were constructed, based on CT measurements of a subject phonating on [a:] before and after phonation into a tube. Acoustic analysis was performed by exciting the models with acoustic flow velocity at the vocal folds. The generated acoustic pressure of the response was computed in front of the mouth and inside the vocal tract for both FE models. Average amplitudes of the pressure oscillations inside the vocal tract and in front of the mouth were compared to display the cost-efficiency of sound energy transfer at different formant frequencies. The formants F1–F3 correspond to classical vibration modes also solvable by 1D vocal tract model. However, for higher formants, there occur more complicated transversal modes which require 3D modelling. A special attention is given to the higher frequency range (above 3.5 Hz where transversal modes exist between piriform sinuses and valleculae. Comparison of the pressure oscillation inside and outside the vocal tract showed that formants differ in their efficiency, F4 (at about 3.5 kHz, i.e. at the speaker’s or singer’s formant region being the most effective. The higher formants created a clear formant cluster around 4 kHz after the vocal exercise with the tube. Since the human ear is most sensitive to frequencies between 2 and 4 kHz concentration of sound energy in this frequency region (F4–F5 is effective for communication. The results suggest that exercising using phonation into tubes help in improving the vocal economy.
Finite element model of magnetoconvection of a ferrofluid
International Nuclear Information System (INIS)
Snyder, S.M.; Cader, Tahir; Finlayson, B.A.
2003-01-01
Combined natural and magnetic convective heat transfer through a ferrofluid in a cubic enclosure is simulated numerically. The momentum equation includes a magnetic term that arises when a magnetic fluid is in the presence of a magnetic field gradient and a temperature gradient. In order to validate the theory, the wall temperature isotherms and Nusselt numbers are compared to experimental work of Sawada et al. (Int. J. Appl. Electromagn. Mater. 4 (1994) 329). Results are obtained using standard computational fluid dynamics codes, with modifications to account for the Langevin factor when needed. The CFD code FIDAP uses the finite element method, sometimes with a user-defined subroutine. The CFD code FEMLAB uses the finite element method with a user-supplied body force
Progress in Finite Element Modeling of the Lower Extremities
2015-06-01
an assembly architecture that is currently under development. 15. SUBJECT TERMS lower extremities, FEM , accelerative loading, biological...is on lower-leg injuries due to an underbody blast event beneath a vehicle. During such an event, the explosive gases and soil impart momentum to the...parsed by an external finite element method ( FEM ) solver. The program is written in C++ and heavily makes use of operator overloading, function
Finite-element method modeling of hyper-frequency structures
International Nuclear Information System (INIS)
Zhang, Min
1990-01-01
The modelization of microwave propagation problems, including Eigen-value problem and scattering problem, is accomplished by the finite element method with vector functional and scalar functional. For Eigen-value problem, propagation modes in waveguides and resonant modes in cavities can be calculated in a arbitrarily-shaped structure with inhomogeneous material. Several microwave structures are resolved in order to verify the program. One drawback associated with the vector functional is the appearance of spurious or non-physical solutions. A penalty function method has been introduced to reduce spurious' solutions. The adaptive charge method is originally proposed in this thesis to resolve waveguide scattering problem. This method, similar to VSWR measuring technique, is more efficient to obtain the reflection coefficient than the matrix method. Two waveguide discontinuity structures are calculated by the two methods and their results are compared. The adaptive charge method is also applied to a microwave plasma excitor. It allows us to understand the role of different physical parameters of excitor in the coupling of microwave energy to plasma mode and the mode without plasma. (author) [fr
Finite element modeling of AP1000 nuclear island
International Nuclear Information System (INIS)
Tinic, S.; Orr, R.
2003-01-01
The AP1000 is a standard design developed by Westinghouse and its partners for an advanced nuclear power plant utilizing passive safety features. It is based on the certified design of the AP600 and has been uprated to 1000 MWe. The plant has five principal building structures; the nuclear island, the turbine building; the annex building; the diesel generator building and the radwaste building. The nuclear island consists of the containment building (the steel containment vessel and the containment internal structures), the shield building, and the auxiliary building. These structures are founded on a common basemat and are collectively known as the nuclear island. This paper describes use of the general purpose finite element program ANSYS [2] in structural analyses and qualification of the AP1000 nuclear island buildings. It describes the modeling of the shield building and the auxiliary building and the series of analyses and the flow of information from the global analyses to the detailed analyses and building qualification. (author)
A finite element model for protein transport in vivo
Directory of Open Access Journals (Sweden)
Montas Hubert J
2007-06-01
Full Text Available Abstract Background Biological mass transport processes determine the behavior and function of cells, regulate interactions between synthetic agents and recipient targets, and are key elements in the design and use of biosensors. Accurately predicting the outcomes of such processes is crucial to both enhancing our understanding of how these systems function, enabling the design of effective strategies to control their function, and verifying that engineered solutions perform according to plan. Methods A Galerkin-based finite element model was developed and implemented to solve a system of two coupled partial differential equations governing biomolecule transport and reaction in live cells. The simulator was coupled, in the framework of an inverse modeling strategy, with an optimization algorithm and an experimental time series, obtained by the Fluorescence Recovery after Photobleaching (FRAP technique, to estimate biomolecule mass transport and reaction rate parameters. In the inverse algorithm, an adaptive method was implemented to calculate sensitivity matrix. A multi-criteria termination rule was developed to stop the inverse code at the solution. The applicability of the model was illustrated by simulating the mobility and binding of GFP-tagged glucocorticoid receptor in the nucleoplasm of mouse adenocarcinoma. Results The numerical simulator shows excellent agreement with the analytic solutions and experimental FRAP data. Detailed residual analysis indicates that residuals have zero mean and constant variance and are normally distributed and uncorrelated. Therefore, the necessary and sufficient criteria for least square parameter optimization, which was used in this study, were met. Conclusion The developed strategy is an efficient approach to extract as much physiochemical information from the FRAP protocol as possible. Well-posedness analysis of the inverse problem, however, indicates that the FRAP protocol provides insufficient
Directory of Open Access Journals (Sweden)
M.H.R. Ghoreishy
2008-02-01
Full Text Available This research work is devoted to the footprint analysis of a steel-belted radial tyre (185/65R14 under vertical static load using finite element method. Two models have been developed in which in the first model the tread patterns were replaced by simple ribs while the second model was consisted of details of the tread blocks. Linear elastic and hyper elastic (Arruda-Boyce material models were selected to describe the mechanical behavior of the reinforcing and rubbery parts, respectively. The above two finite element models of the tyre were analyzed under inflation pressure and vertical static loads. The second model (with detailed tread patterns was analyzed with and without friction effect between tread and contact surfaces. In every stage of the analysis, the results were compared with the experimental data to confirm the accuracy and applicability of the model. Results showed that neglecting the tread pattern design not only reduces the computational cost and effort but also the differences between computed deformations do not show significant changes. However, more complicated variables such as shape and area of the footprint zone and contact pressure are affected considerably by the finite element model selected for the tread blocks. In addition, inclusion of friction even in static state changes these variables significantly.
A finite element model for sound transmission through laminated composite plates
Ramakrishnan, J. V.; Koval, L. R.
1987-01-01
The finite element method is used to model the noise transmission through unstiffened and stiffened laminated composite panels of finite size into a closed cavity. Plate and acoustic finite elements are coupled and the frequencies of the coupled modes are determined. The model is then used to calculate the noise reduction of the panel. Results are compared to experimental values obtained at the NASA Langley Research Center. The purpose of this paper is to demonstrate the use of finite elements to model, for noise transmission calculations, complex structures, such as a stiffened composite panel or a composite panel with windows.
Finite Element Modeling Techniques for Analysis of VIIP
Feola, Andrew J.; Raykin, J.; Gleason, R.; Mulugeta, Lealem; Myers, Jerry G.; Nelson, Emily S.; Samuels, Brian C.; Ethier, C. Ross
2015-01-01
Visual Impairment and Intracranial Pressure (VIIP) syndrome is a major health concern for long-duration space missions. Currently, it is thought that a cephalad fluid shift in microgravity causes elevated intracranial pressure (ICP) that is transmitted along the optic nerve sheath (ONS). We hypothesize that this in turn leads to alteration and remodeling of connective tissue in the posterior eye which impacts vision. Finite element (FE) analysis is a powerful tool for examining the effects of mechanical loads in complex geometries. Our goal is to build a FE analysis framework to understand the response of the lamina cribrosa and optic nerve head to elevations in ICP in VIIP.
CONTRIBUTIONS TO THE FINITE ELEMENT MODELING OF LINEAR ULTRASONIC MOTORS
Directory of Open Access Journals (Sweden)
Oana CHIVU
2013-05-01
Full Text Available The present paper is concerned with the main modeling elements as produced by means of thefinite element method of linear ultrasonic motors. Hence, first the model is designed and then a modaland harmonic analysis are carried out in view of outlining the main outcomes
Finite-Element Modeling of Timber Joints with Punched Metal Plate Fasteners
DEFF Research Database (Denmark)
Ellegaard, Peter
2006-01-01
The focus of this paper is to describe the idea and the theory behind a finite-element model developed for analysis of timber trusses with punched metal plate fasteners (nail plates). The finite-element model includes the semirigid and nonlinear behavior of the joints (nonlinear nail and plate...... area over the joint lines. The finite-element model is based on the Foschi model, but with further improvements. After the theory of the model is described, results from experimental tests with two types of nail plate joints are compared with predictions given by the model. The model estimates...
Finite element model updating of concrete structures based on imprecise probability
Biswal, S.; Ramaswamy, A.
2017-09-01
Imprecise probability based methods are developed in this study for the parameter estimation, in finite element model updating for concrete structures, when the measurements are imprecisely defined. Bayesian analysis using Metropolis Hastings algorithm for parameter estimation is generalized to incorporate the imprecision present in the prior distribution, in the likelihood function, and in the measured responses. Three different cases are considered (i) imprecision is present in the prior distribution and in the measurements only, (ii) imprecision is present in the parameters of the finite element model and in the measurement only, and (iii) imprecision is present in the prior distribution, in the parameters of the finite element model, and in the measurements. Procedures are also developed for integrating the imprecision in the parameters of the finite element model, in the finite element software Abaqus. The proposed methods are then verified against reinforced concrete beams and prestressed concrete beams tested in our laboratory as part of this study.
Quick Method for Aeroelastic and Finite Element Modeling of Wind Turbine Blades
DEFF Research Database (Denmark)
Bennett, Jeffrey; Bitsche, Robert; Branner, Kim
2014-01-01
In this paper a quick method for modeling composite wind turbine blades is developed for aeroelastic simulations and finite element analyses. The method reduces the time to model a wind turbine blade by automating the creation of a shell finite element model and running it through a cross...... the user has two models of the same blade, one for performing a structural finite element model analysis and one for aeroelastic simulations. Here, the method is implemented and applied to reverse engineer a structural layup for the NREL 5MW reference blade. The model is verified by comparing natural...
A discrete finite element modelling and measurements for powder compaction
International Nuclear Information System (INIS)
Choi, J L; Gethin, D T
2009-01-01
An experimental investigation into friction between powder and a target surface together with numerical modelling of compaction and friction processes at a micro-scale are presented in this paper. The experimental work explores friction mechanisms by using an extended sliding plate apparatus operating at low load while sliding over a long distance. Tests were conducted for copper and 316 steel with variation in loads, surface finish and its orientation. The behaviours of the static and dynamic friction were identified highlighting the important influence of particle size, particle shape, material response and surface topography. The results also highlighted that under light loading the friction coefficient remains at a level lower than that derived from experiments on equipment having a wider dynamic range and this is attributed to the enhanced sensitivity of the measurement equipment. The results also suggest that friction variation with sliding distance is a consequence of damage, rather than presentation of an uncontaminated target sliding surface. The complete experimental cycle was modelled numerically using a combined discrete and finite element scheme enabling exploration of mechanisms that are defined at the particle level. Using compaction as the starting point, a number of simulation factors and process parameters were investigated. Comparisons were made with previously published work, showing reasonable agreement and the simulations were then used to explore the process response to the range of particle scale factors. Models comprising regular packing of round particles exhibited stiff response with high initial density. Models with random packing were explored and were found to reflect trends that are more closely aligned with experimental observation, including rearrangement, followed by compaction under a regime of elastic then plastic deformation. Numerical modelling of the compaction stage was extended to account for the shearing stage of the
Nakamura, Keiko; Tajima, Kiyoshi; Chen, Ker-Kong; Nagamatsu, Yuki; Kakigawa, Hiroshi; Masumi, Shin-ich
2013-12-01
This study focused on the application of novel finite-element analysis software for constructing a finite-element model from the computed tomography data of a human dentulous mandible. The finite-element model is necessary for evaluating the mechanical response of the alveolar part of the mandible, resulting from occlusal force applied to the teeth during biting. Commercially available patient-specific general computed tomography-based finite-element analysis software was solely applied to the finite-element analysis for the extraction of computed tomography data. The mandibular bone with teeth was extracted from the original images. Both the enamel and the dentin were extracted after image processing, and the periodontal ligament was created from the segmented dentin. The constructed finite-element model was reasonably accurate using a total of 234,644 nodes and 1,268,784 tetrahedral and 40,665 shell elements. The elastic moduli of the heterogeneous mandibular bone were determined from the bone density data of the computed tomography images. The results suggested that the software applied in this study is both useful and powerful for creating a more accurate three-dimensional finite-element model of a dentulous mandible from the computed tomography data without the need for any other software.
Determination of acoustic vibration in watermelon by finite element modeling
Nourain, Jamal; Ying, Yibin B.; Wang, Jianping; Rao, Xiuqin
2004-11-01
The analysis of the vibration responses of a fruit is suggested to measure firmness non-destructively. A wooden ball excited the fruits and the response signals were captured using an accelerometer sensor. The method has been well studied and understood on ellipsoidal shaped fruit (watermelon). In this work, using the finite element simulations, the applicability of the method on watermelon was investigated. The firmness index is dependent on the mass, density, and natural frequency of the lowest spherical modes (under free boundary conditions). This developed index extends the firmness estimation for fruits or vegetables from a spherical to an ellipsoidal shape. The mode of Finite element analysis (FEA) of watermelon was generated based on measured geometry, and it can be served as a theoretical reference for predicting the modal characteristics as a function of design parameters such as material, geometrical, and physical properties. It was found that there were four types of mode shapes. The 1st one was first-type longitudinal mode, the 2nd one was the second-type longitudinal mode, the 3rd one was breathing mode or pure compression mode, and the fourth was flexural or torsional mode shape. As suggested in many references, the First-type spherical vibration mode or oblate-Prolate for watermelon is the lowest bending modes, it's most likely related to fruit firmness. Comparisons of finite element and experimental modal parameters show that both results were agreed in mode shape as well as natural frequencies. In order to measure the vibration signal of the mode, excitation and sensors should be placed on the watermelon surface far away from the nodal lines. The excitation and the response sensors should be in accordance with vibration directions. The correlations between the natural frequency and firmness was 0.856, natural frequency and Young's modulus was 0.800, and the natural frequency and stiffness factor (SF) was 0.862. The stiffness factor (SF) is adequate
Finite element method for incompressible two-fluid model using a fractional step method
International Nuclear Information System (INIS)
Uchiyama, Tomomi
1997-01-01
This paper presents a finite element method for an incompressible two-fluid model. The solution algorithm is based on the fractional step method, which is frequently used in the finite element calculation for single-phase flows. The calculating domain is divided into quadrilateral elements with four nodes. The Galerkin method is applied to derive the finite element equations. Air-water two-phase flows around a square cylinder are calculated by the finite element method. The calculation demonstrates the close relation between the volumetric fraction of the gas-phase and the vortices shed from the cylinder, which is favorably compared with the existing data. It is also confirmed that the present method allows the calculation with less CPU time than the SMAC finite element method proposed in my previous paper. (author)
A holistic 3D finite element simulation model for thermoelectric power generator element
International Nuclear Information System (INIS)
Wu, Guangxi; Yu, Xiong
2014-01-01
Highlights: • Development of a holistic simulation model for the thermoelectric energy harvester. • Account for delta Seebeck coefficient and carrier charge densities variations. • Solution of thermo-electric coupling problem with finite element method. • Model capable of predicting phenomena not captured by traditional models. • A simulation tool for design of innovative TEM materials and structures. - Abstract: Harvesting the thermal energy stored in the ambient environment provides a potential sustainable energy source. Thermoelectric power generators have advantages of having no moving parts, being durable, and light-weighted. These unique features are advantageous for many applications (i.e., carry-on medical devices, embedded infrastructure sensors, aerospace, transportation, etc.). To ensure the efficient applications of thermoelectric energy harvesting system, the behaviors of such systems need to be fully understood. Finite element simulations provide important tools for such purpose. Although modeling the performance of thermoelectric modules has been conducted by many researchers, due to the complexity in solving the coupled problem, the influences of the effective Seebeck coefficient and carrier density variations on the performance of thermoelectric system are generally neglected. This results in an overestimation of the power generator performance under strong-ionization temperature region. This paper presents an advanced simulation model for thermoelectric elements that considers the effects of both factors. The mathematical basis of this model is firstly presented. Finite element simulations are then implemented on a thermoelectric power generator unit. The characteristics of the thermoelectric power generator and their relationship to its performance are discussed under different working temperature regions. The internal physics processes of the TEM harvester are analyzed from the results of computational simulations. The new model
Finite element modeling and simulation with ANSYS workbench
Chen, Xiaolin
2014-01-01
IntroductionSome Basic ConceptsAn Example in FEA: Spring SystemOverview of ANSYS WorkbenchSummaryProblemsBars and TrussesIntroductionReview of the 1-D Elasticity TheoryModeling of TrussesFormulation of the Bar ElementExamples with Bar ElementsCase Study with ANSYS WorkbenchSummaryProblemsBeams and FramesIntroductionReview of the Beam TheoryModeling of Beams and FramesFormulation of the Beam ElementExamples with Beam ElementsCase Study with ANSYS WorkbenchSummaryProblemsTwo-Dimensional ElasticityIntroductionReview of 2-D Elasticity TheoryModeling of 2-D Elasticity ProblemsFormulation of the Pla
Modeling bistable behaviors in morphing structures through finite element simulations.
Guo, Qiaohang; Zheng, Huang; Chen, Wenzhe; Chen, Zi
2014-01-01
Bistable structures, exemplified by the Venus flytrap and slap bracelets, can transit between different configurations upon certain external stimulation. Here we study, through three-dimensional finite element simulations, the bistable behaviors in elastic plates in the absence of terminate loads, but with pre-strains in one (or both) of the two composite layers. Both the scenarios with and without a given geometric mis-orientation angle are investigated, the results of which are consistent with recent theoretical and experimental studies. This work can open ample venues for programmable designs of plant/shell structures with large deformations, with applications in designing bio-inspired robotics for biomedical research and morphing/deployable structures in aerospace engineering.
Finite element modeling of electromagnetic fields and waves using NASTRAN
Moyer, E. Thomas, Jr.; Schroeder, Erwin
1989-01-01
The various formulations of Maxwell's equations are reviewed with emphasis on those formulations which most readily form analogies with Navier's equations. Analogies involving scalar and vector potentials and electric and magnetic field components are presented. Formulations allowing for media with dielectric and conducting properties are emphasized. It is demonstrated that many problems in electromagnetism can be solved using the NASTRAN finite element code. Several fundamental problems involving time harmonic solutions of Maxwell's equations with known analytic solutions are solved using NASTRAN to demonstrate convergence and mesh requirements. Mesh requirements are studied as a function of frequency, conductivity, and dielectric properties. Applications in both low frequency and high frequency are highlighted. The low frequency problems demonstrate the ability to solve problems involving media inhomogeneity and unbounded domains. The high frequency applications demonstrate the ability to handle problems with large boundary to wavelength ratios.
2001-05-01
Linear and non-linear finite element method models were developed for a reinforced concrete bridge that had been strengthened with fiber reinforced polymer composites. ANSYS and SAP2000 modeling software were used; however, most of the development ef...
The development of a curved beam element model applied to finite elements method
International Nuclear Information System (INIS)
Bento Filho, A.
1980-01-01
A procedure for the evaluation of the stiffness matrix for a thick curved beam element is developed, by means of the minimum potential energy principle, applied to finite elements. The displacement field is prescribed through polynomial expansions, and the interpolation model is determined by comparison of results obtained by the use of a sample of different expansions. As a limiting case of the curved beam, three cases of straight beams, with different dimensional ratios are analised, employing the approach proposed. Finally, an interpolation model is proposed and applied to a curved beam with great curvature. Desplacements and internal stresses are determined and the results are compared with those found in the literature. (Author) [pt
Panczak, Tim; Ring, Steve; Welch, Mark
1999-01-01
Thermal engineering has long been left out of the concurrent engineering environment dominated by CAD (computer aided design) and FEM (finite element method) software. Current tools attempt to force the thermal design process into an environment primarily created to support structural analysis, which results in inappropriate thermal models. As a result, many thermal engineers either build models "by hand" or use geometric user interfaces that are separate from and have little useful connection, if any, to CAD and FEM systems. This paper describes the development of a new thermal design environment called the Thermal Desktop. This system, while fully integrated into a neutral, low cost CAD system, and which utilizes both FEM and FD methods, does not compromise the needs of the thermal engineer. Rather, the features needed for concurrent thermal analysis are specifically addressed by combining traditional parametric surface based radiation and FD based conduction modeling with CAD and FEM methods. The use of flexible and familiar temperature solvers such as SINDA/FLUINT (Systems Improved Numerical Differencing Analyzer/Fluid Integrator) is retained.
Directory of Open Access Journals (Sweden)
Shouyan Jiang
2017-01-01
Full Text Available We model the fluid flow within the crack as one-dimensional flow and assume that the flow is laminar; the fluid is incompressible and accounts for the time-dependent rate of crack opening. Here, we discretise the flow equation by finite volume methods. The extended finite element methods are used for solving solid medium with crack under dynamic loads. Having constructed the approximation of dynamic extended finite element methods, the derivation of governing equation for dynamic extended finite element methods is presented. The implicit time algorithm is elaborated for the time descritisation of dominant equation. In addition, the interaction integral method is given for evaluating stress intensity factors. Then, the coupling model for modelling hydraulic fracture can be established by the extended finite element methods and the finite volume methods. We compare our present numerical results with our experimental results for verifying the proposed model. Finally, we investigate the water pressure distribution along crack surface and the effect of water pressure distribution on the fracture property.
Modelling of Conveyor Belt Passage by Driving Drum Using Finite Element Methods
Directory of Open Access Journals (Sweden)
Nikoleta Mikušová
2017-12-01
Full Text Available The finite element methods are used in many disciplines by the development of products, typically in mechanical engineering (for example in automotive industry, biomechanics, etc.. Some modern programs of the finite element's methods have specific tools (electromagnetic, fluid and structural simulations. The finite elements methods allow detailed presentation of structures by bending or torsion, complete design, testing and optimization before the prototype production. The aims of this paper were to the model of conveyor belt passage by driving drum. The model was created by the program Abaqus CAE. The created model presented data about forces, pressures, and deformation of the belt conveyor.
Finite element/percolation theory modelling of the micromechanical behavior of clayey soils.
Pérez-Rea, M Luz; Horta-Rangel, Jaime; López-Lara, Teresa; Hernández-Zaragoza, Juan B; Alcocer, Sergio M; Castaño, Victor M
2015-01-01
A hybrid model for soils, which combines percolation theory and finite element method is presented. The internal soil structure is modelled via the finite element method, and percolation networks are used for analyzing its mechanical behaviour. Through a microscopic characterization of elastic properties of soil grains, the model is generated. The effective percolation threshold obtained is lower than that of the network geometric percolation. The effective mechanical properties predicted are successfully compared to published experimental results.
Finite element/percolation theory modelling of the micromechanical behavior of clayey soils
P?rez-Rea, M Luz; Horta-Rangel, Jaime; L?pez-Lara, Teresa; Hern?ndez-Zaragoza, Juan B; Alcocer, Sergio M; Casta?o, Victor M
2015-01-01
A hybrid model for soils, which combines percolation theory and finite element method is presented. The internal soil structure is modelled via the finite element method, and percolation networks are used for analyzing its mechanical behaviour. Through a microscopic characterization of elastic properties of soil grains, the model is generated. The effective percolation threshold obtained is lower than that of the network geometric percolation. The effective mechanical properties predicted are...
2017-11-13
Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6040--17-9760 Equilibrium Wall-Model Implementation in a Nodal Finite Element Flow...DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Equilibrium Wall-Model Implementation in a Nodal Finite Element Flow Solver...Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The equilibrium wall model is implemented in a nodal
Efficient Finite Element Models for Calculation of the No-load losses of the Transformer
Directory of Open Access Journals (Sweden)
Kamran Dawood
2017-10-01
Full Text Available Different transformer models are examined for the calculation of the no-load losses using finite element analysis. Two-dimensional and three-dimensional finite element analyses are used for the simulation of the transformer. Results of the finite element method are also compared with the experimental results. The Result shows that 3-dimensional provide high accuracy as compared to the 2 dimensional full and half model. However, the 2-dimensional half model is the less time-consuming method as compared to the 3 and 2-dimensional full model. Simulation time duration taken by the different models of the transformer is also compared. The difference between the 3-dimensional finite element method and experimental results are less than 3%. These numerical methods can help transformer designers to minimize the development of the prototype transformers.
Transient thermal modelling of ball bearing using finite element method
Sibilli, Thierry; Igie, Uyioghosa
2017-01-01
Gas turbines are fitted with rolling element bearings, which transfer loads and supports the shafts. The interaction between the rotating and stationary parts in the bearing causes a conversion of some of the power into heat, influencing the thermal behaviour of the entire bearing chamber. To improve thermal modelling of bearing chambers, this work focused on modelling of the heat generated and dissipated around the bearings, in terms of magnitude and location, and the interaction with the co...
Finite element analysis of three dimensional crack growth by the use of a boundary element sub model
DEFF Research Database (Denmark)
Lucht, Tore
2009-01-01
A new automated method to model non-planar three dimensional crack growth is proposed which combines the advantages of both the boundary element method and the finite element method. The proposed method links the two methods by a submodelling strategy in which the solution of a global finite...... element model containing an approximation of the crack is interpolated to a much smaller boundary element model containing a fine discretization of the real crack. The method is validated through several numerical comparisons and by comparison to crack growth measured in a test specimen for an engineering...
Gabel, R.; Lang, P. F.; Smith, L. A.; Reed, D. A.
1989-01-01
Boeing Helicopter, together with other United States helicopter manufacturers, participated in a finite element applications program to emplace in the United States a superior capability to utilize finite element analysis models in support of helicopter airframe design. The activities relating to planning and creating a finite element vibrations model of the Boeing Model 36-0 composite airframe are summarized, along with the subsequent analytical correlation with ground shake test data.
Finite element models of non-Newtonian crater relaxation
Thomas, Paul J.; Schubert, Gerald
1987-01-01
The effects of a non-Newtonian rheology on the profiles of relaxing craters (such as those seen on the surfaces of the icy Galilean and Saturnian satellites) were studied. Two-dimensional finite element simulations of non-Newtonian viscous flow were performed, and the results were compared with those associated with Newtonian rheology. Viscous relaxation of craters in a non-Newtonian medium was significantly different from that in a Newtonian medium. Crater rims are observed to relax at a more rapid rate in a non-Newtonian region as a result of the movement of the low viscosity region to underneath the crater rim after the initial relaxation of the bowl. Significant differences are also found when central depth is plotted as a function of time. For a Newtonian medium, crater relaxation is exponential in form. In contrast, non-Newtonian crater relaxation is initially rapid, in response to the large initial stresses and small viscosities; however, as stresses decrease, this relaxation becomes extremely gradual.
Soft tissue deformation using a Hierarchical Finite Element Model.
Faraci, Alessandro; Bello, Fernando; Darzi, Ara
2004-01-01
Simulating soft tissue deformation in real-time has become increasingly important in order to provide a realistic virtual environment for training surgical skills. Several methods have been proposed with the aim of rendering in real-time the mechanical and physiological behaviour of human organs, one of the most popular being Finite Element Method (FEM). In this paper we present a new approach to the solution of the FEM problem introducing the concept of parent and child mesh within the development of a hierarchical FEM. The online selection of the child mesh is presented with the purpose to adapt the mesh hierarchy in real-time. This permits further refinement of the child mesh increasing the detail of the deformation without slowing down the simulation and giving the possibility of integrating force feedback. The results presented demonstrate the application of our proposed framework using a desktop virtual reality (VR) system that incorporates stereo vision with integrated haptics co-location via a desktop Phantom force feedback device.
Energy Technology Data Exchange (ETDEWEB)
XU, J.; COSTANTINO, C.; HOFMAYER, C.
2006-06-26
PAPER DISCUSSES COMPUTATIONS OF SEISMIC INDUCED SOIL PRESSURES USING FINITE ELEMENT MODELS FOR DEEPLY EMBEDDED AND OR BURIED STIFF STRUCTURES SUCH AS THOSE APPEARING IN THE CONCEPTUAL DESIGNS OF STRUCTURES FOR ADVANCED REACTORS.
National Research Council Canada - National Science Library
Minnicino, Michael
2005-01-01
... such as supplementing insensitive munition capabilities. The development of a finite-element (FE) model is a valitable tool for investigating design modifications to the container-foam support system without the need for expensive experimental tests...
Finite Element Models for Electron Beam Freeform Fabrication Process, Phase I
National Aeronautics and Space Administration — This Small Business Innovation Research proposal offers to develop the most accurate, comprehensive and efficient finite element models to date for simulation of the...
Implementation of a Unified Constitutive Model into the ABAQUS Finite Element Package
National Research Council Canada - National Science Library
Wescott, R
1999-01-01
Unified constitutive models have previously been developed at AMRL and implemented into the PAFEC and ABAQUS Finite Element packages to predict the stress-strain response of structures that undergo...
Energy Technology Data Exchange (ETDEWEB)
Patra, Anirban [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez Saez, Enrique [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-31
This report describes the implementation of a crystal plasticity framework (VPSC) for irradiation hardening and plastic deformation in the finite element code, MOOSE. Constitutive models for irradiation hardening and the crystal plasticity framework are described in a previous report [1]. Here we describe these models briefly and then describe an algorithm for interfacing VPSC with finite elements. Example applications of tensile deformation of a dog bone specimen and a 3D pre-irradiated bar specimen performed using MOOSE are demonstrated.
a finite element model for the analysis of bridge decks
African Journals Online (AJOL)
Dr Obe
ε(x, y) State of stress at a point σ(x, y). State of stress at a point. [D]. Elasticity matrix θx, θy. Rotations ... the partial differential equation for the deflection w of an orthotropic plate: ( ) (1) where 2H is the torsional ... θx, θy) and a cubic displacement model, (Fig. 2). Studies by Gallagher [4] showed that this element is efficient and ...
An Automated Method for Landmark Identification and Finite-Element Modeling of the Lumbar Spine.
Campbell, Julius Quinn; Petrella, Anthony J
2015-11-01
The purpose of this study was to develop a method for the automated creation of finite-element models of the lumbar spine. Custom scripts were written to extract bone landmarks of lumbar vertebrae and assemble L1-L5 finite-element models. End-plate borders, ligament attachment points, and facet surfaces were identified. Landmarks were identified to maintain mesh correspondence between meshes for later use in statistical shape modeling. 90 lumbar vertebrae were processed creating 18 subject-specific finite-element models. Finite-element model surfaces and ligament attachment points were reproduced within 1e-5 mm of the bone surface, including the critical contact surfaces of the facets. Element quality exceeded specifications in 97% of elements for the 18 models created. The current method is capable of producing subject-specific finite-element models of the lumbar spine with good accuracy, quality, and robustness. The automated methods developed represent advancement in the state of the art of subject-specific lumbar spine modeling to a scale not possible with prior manual and semiautomated methods.
Optical Finite Element Processor
Casasent, David; Taylor, Bradley K.
1986-01-01
A new high-accuracy optical linear algebra processor (OLAP) with many advantageous features is described. It achieves floating point accuracy, handles bipolar data by sign-magnitude representation, performs LU decomposition using only one channel, easily partitions and considers data flow. A new application (finite element (FE) structural analysis) for OLAPs is introduced and the results of a case study presented. Error sources in encoded OLAPs are addressed for the first time. Their modeling and simulation are discussed and quantitative data are presented. Dominant error sources and the effects of composite error sources are analyzed.
Finite element model updating of natural fibre reinforced composite structure in structural dynamics
Directory of Open Access Journals (Sweden)
Sani M.S.M.
2016-01-01
Full Text Available Model updating is a process of making adjustment of certain parameters of finite element model in order to reduce discrepancy between analytical predictions of finite element (FE and experimental results. Finite element model updating is considered as an important field of study as practical application of finite element method often shows discrepancy to the test result. The aim of this research is to perform model updating procedure on a composite structure as well as trying improving the presumed geometrical and material properties of tested composite structure in finite element prediction. The composite structure concerned in this study is a plate of reinforced kenaf fiber with epoxy. Modal properties (natural frequency, mode shapes, and damping ratio of the kenaf fiber structure will be determined using both experimental modal analysis (EMA and finite element analysis (FEA. In EMA, modal testing will be carried out using impact hammer test while normal mode analysis using FEA will be carried out using MSC. Nastran/Patran software. Correlation of the data will be carried out before optimizing the data from FEA. Several parameters will be considered and selected for the model updating procedure.
Heat transfer model and finite element formulation for simulation of selective laser melting
Roy, Souvik; Juha, Mario; Shephard, Mark S.; Maniatty, Antoinette M.
2017-10-01
A novel approach and finite element formulation for modeling the melting, consolidation, and re-solidification process that occurs in selective laser melting additive manufacturing is presented. Two state variables are introduced to track the phase (melt/solid) and the degree of consolidation (powder/fully dense). The effect of the consolidation on the absorption of the laser energy into the material as it transforms from a porous powder to a dense melt is considered. A Lagrangian finite element formulation, which solves the governing equations on the unconsolidated reference configuration is derived, which naturally considers the effect of the changing geometry as the powder melts without needing to update the simulation domain. The finite element model is implemented into a general-purpose parallel finite element solver. Results are presented comparing to experimental results in the literature for a single laser track with good agreement. Predictions for a spiral laser pattern are also shown.
Finite element modelling of creep process - steady state stresses and strains
Directory of Open Access Journals (Sweden)
Sedmak Aleksandar S.
2014-01-01
Full Text Available Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C*integral evaluation.
International Nuclear Information System (INIS)
Prihantoro, Rudy; Sutarno, Doddy; Nurhasan
2016-01-01
In this work, we seek numerical solution of 3-D Magnetotelluric (MT) using edge- based finite element method. This approach is a variant of standard finite element method and commonly referred as vector finite-element (VFE) method. Nonphysical solutions usually occurred when the solution is sought using standard finite element which is a node based element. Vector finite element attempt to overcome those nonphysical solutions by using the edges of the element as vector basis. The proposed approach on solving second order Maxwell differential equation of 3-D MT is using direct solver rather than iterative method. Therefore, divergence correction to accelerate the rate of convergence for its iterative solution is no longer needed. The utilization of direct solver has been verified previously for correctness by comparing the resulting solution to those given by analytical solution, as well as the solution come from the other numerical methods, for earth layered model, 2-D models and COMMEMI 3D-2 model. In this work, further verification resulted from recent comparison model of Dublin Test Model 1 (DTM1) is presented. (paper)
Finite elements and approximation
Zienkiewicz, O C
2006-01-01
A powerful tool for the approximate solution of differential equations, the finite element is extensively used in industry and research. This book offers students of engineering and physics a comprehensive view of the principles involved, with numerous illustrative examples and exercises.Starting with continuum boundary value problems and the need for numerical discretization, the text examines finite difference methods, weighted residual methods in the context of continuous trial functions, and piecewise defined trial functions and the finite element method. Additional topics include higher o
Finite element modelling of aluminum alloy 2024-T3 under transverse impact loading
Abdullah, Ahmad Sufian; Kuntjoro, Wahyu; Yamin, A. F. M.
2017-12-01
Fiber metal laminate named GLARE is a new aerospace material which has great potential to be widely used in future lightweight aircraft. It consists of aluminum alloy 2024-T3 and glass-fiber reinforced laminate. In order to produce reliable finite element model of impact response or crashworthiness of structure made of GLARE, one can initially model and validate the finite element model of the impact response of its constituents separately. The objective of this study was to develop a reliable finite element model of aluminum alloy 2024-T3 under low velocity transverse impact loading using commercial software ABAQUS. Johnson-Cook plasticity and damage models were used to predict the alloy's material properties and impact behavior. The results of the finite element analysis were compared to the experiment that has similar material and impact conditions. Results showed good correlations in terms of impact forces, deformation and failure progressions which concluded that the finite element model of 2024-T3 aluminum alloy under low velocity transverse impact condition using Johnson-Cook plastic and damage models was reliable.
Finite element modelling of elastic intraplate stresses due to ...
Indian Academy of Sciences (India)
deep seismic sounding data; Tectonophys. 202 375–397. Vlasov A N, Mnushkin M G and Yanovsky Yu G 2000. Object-oriented approach in programming of finite ele- ment method; In: Proc. 3rd. Int. Conf. on Advances of Computer Methods in Geotechnical and Geoenvi- ronmental Engineering (ed.) S A Yufin; pp. 367–372.
Finite element model updating of the UCF grid benchmark using measured frequency response functions
Sipple, Jesse D.; Sanayei, Masoud
2014-05-01
A frequency response function based finite element model updating method is presented and used to perform parameter estimation of the University of Central Florida Grid Benchmark Structure. The proposed method is used to calibrate the initial finite element model using measured frequency response functions from the undamaged, intact structure. Stiffness properties, mass properties, and boundary conditions of the initial model were estimated and updated. Model updating was then performed using measured frequency response functions from the damaged structure to detect physical structural change. Grouping and ungrouping were utilized to determine the exact location and magnitude of the damage. The fixity in rotation of two boundary condition nodes was accurately and successfully estimated. The usefulness of the proposed method for finite element model updating is shown by being able to detect, locate, and quantify change in structural properties.
Brigham, John C; Aquino, Wilkins; Aguilo, Miguel A; Diamessis, Peter J
2011-01-15
An approach for efficient and accurate finite element analysis of harmonically excited soft solids using high-order spectral finite elements is presented and evaluated. The Helmholtz-type equations used to model such systems suffer from additional numerical error known as pollution when excitation frequency becomes high relative to stiffness (i.e. high wave number), which is the case, for example, for soft tissues subject to ultrasound excitations. The use of high-order polynomial elements allows for a reduction in this pollution error, but requires additional consideration to counteract Runge's phenomenon and/or poor linear system conditioning, which has led to the use of spectral element approaches. This work examines in detail the computational benefits and practical applicability of high-order spectral elements for such problems. The spectral elements examined are tensor product elements (i.e. quad or brick elements) of high-order Lagrangian polynomials with non-uniformly distributed Gauss-Lobatto-Legendre nodal points. A shear plane wave example is presented to show the dependence of the accuracy and computational expense of high-order elements on wave number. Then, a convergence study for a viscoelastic acoustic-structure interaction finite element model of an actual ultrasound driven vibroacoustic experiment is shown. The number of degrees of freedom required for a given accuracy level was found to consistently decrease with increasing element order. However, the computationally optimal element order was found to strongly depend on the wave number.
Brigham, John C.; Aquino, Wilkins; Aguilo, Miguel A.; Diamessis, Peter J.
2010-01-01
An approach for efficient and accurate finite element analysis of harmonically excited soft solids using high-order spectral finite elements is presented and evaluated. The Helmholtz-type equations used to model such systems suffer from additional numerical error known as pollution when excitation frequency becomes high relative to stiffness (i.e. high wave number), which is the case, for example, for soft tissues subject to ultrasound excitations. The use of high-order polynomial elements allows for a reduction in this pollution error, but requires additional consideration to counteract Runge's phenomenon and/or poor linear system conditioning, which has led to the use of spectral element approaches. This work examines in detail the computational benefits and practical applicability of high-order spectral elements for such problems. The spectral elements examined are tensor product elements (i.e. quad or brick elements) of high-order Lagrangian polynomials with non-uniformly distributed Gauss-Lobatto-Legendre nodal points. A shear plane wave example is presented to show the dependence of the accuracy and computational expense of high-order elements on wave number. Then, a convergence study for a viscoelastic acoustic-structure interaction finite element model of an actual ultrasound driven vibroacoustic experiment is shown. The number of degrees of freedom required for a given accuracy level was found to consistently decrease with increasing element order. However, the computationally optimal element order was found to strongly depend on the wave number. PMID:21461402
Vertical discretization with finite elements for a global hydrostatic model on the cubed sphere
Yi, Tae-Hyeong; Park, Ja-Rin
2017-06-01
A formulation of Galerkin finite element with basis-spline functions on a hybrid sigma-pressure coordinate is presented to discretize the vertical terms of global Eulerian hydrostatic equations employed in a numerical weather prediction system, which is horizontally discretized with high-order spectral elements on a cubed sphere grid. This replaces the vertical discretization of conventional central finite difference that is first-order accurate in non-uniform grids and causes numerical instability in advection-dominant flows. Therefore, a model remains in the framework of Galerkin finite elements for both the horizontal and vertical spatial terms. The basis-spline functions, obtained from the de-Boor algorithm, are employed to derive both the vertical derivative and integral operators, since Eulerian advection terms are involved. These operators are used to discretize the vertical terms of the prognostic and diagnostic equations. To verify the vertical discretization schemes and compare their performance, various two- and three-dimensional idealized cases and a hindcast case with full physics are performed in terms of accuracy and stability. It was shown that the vertical finite element with the cubic basis-spline function is more accurate and stable than that of the vertical finite difference, as indicated by faster residual convergence, fewer statistical errors, and reduction in computational mode. This leads to the general conclusion that the overall performance of a global hydrostatic model might be significantly improved with the vertical finite element.
Finite element modelling and updating of friction stir welding (FSW joint for vibration analysis
Directory of Open Access Journals (Sweden)
Zahari Siti Norazila
2017-01-01
Full Text Available Friction stir welding of aluminium alloys widely used in automotive and aerospace application due to its advanced and lightweight properties. The behaviour of FSW joints plays a significant role in the dynamic characteristic of the structure due to its complexities and uncertainties therefore the representation of an accurate finite element model of these joints become a research issue. In this paper, various finite elements (FE modelling technique for prediction of dynamic properties of sheet metal jointed by friction stir welding will be presented. Firstly, nine set of flat plate with different series of aluminium alloy; AA7075 and AA6061 joined by FSW are used. Nine set of specimen was fabricated using various types of welding parameters. In order to find the most optimum set of FSW plate, the finite element model using equivalence technique was developed and the model validated using experimental modal analysis (EMA on nine set of specimen and finite element analysis (FEA. Three types of modelling were engaged in this study; rigid body element Type 2 (RBE2, bar element (CBAR and spot weld element connector (CWELD. CBAR element was chosen to represent weld model for FSW joints due to its accurate prediction of mode shapes and contains an updating parameter for weld modelling compare to other weld modelling. Model updating was performed to improve correlation between EMA and FEA and before proceeds to updating, sensitivity analysis was done to select the most sensitive updating parameter. After perform model updating, total error of the natural frequencies for CBAR model is improved significantly. Therefore, CBAR element was selected as the most reliable element in FE to represent FSW weld joint.
Ziegler, Erik; Chellappa, Sarah L; Gaggioni, Giulia; Ly, Julien Q M; Vandewalle, Gilles; André, Elodie; Geuzaine, Christophe; Phillips, Christophe
2014-12-01
We present a finite element modeling (FEM) implementation for solving the forward problem in electroencephalography (EEG). The solution is based on Helmholtz's principle of reciprocity which allows for dramatically reduced computational time when constructing the leadfield matrix. The approach was validated using a 4-shell spherical model and shown to perform comparably with two current state-of-the-art alternatives (OpenMEEG for boundary element modeling and SimBio for finite element modeling). We applied the method to real human brain MRI data and created a model with five tissue types: white matter, gray matter, cerebrospinal fluid, skull, and scalp. By calculating conductivity tensors from diffusion-weighted MR images, we also demonstrate one of the main benefits of FEM: the ability to include anisotropic conductivities within the head model. Root-mean square deviation between the standard leadfield and the leadfield including white-matter anisotropy showed that ignoring the directional conductivity of white matter fiber tracts leads to orientation-specific errors in the forward model. Realistic head models are necessary for precise source localization in individuals. Our approach is fast, accurate, open-source and freely available online. Copyright © 2014 Elsevier Inc. All rights reserved.
Finotello, Alice; Morganti, Simone; Auricchio, Ferdinando
2017-09-01
In the last few years, several studies, each with different aim and modeling detail, have been proposed to investigate transcatheter aortic valve implantation (TAVI) with finite elements. The present work focuses on the patient-specific finite element modeling of the aortic valve complex. In particular, we aim at investigating how different modeling strategies in terms of material models/properties and discretization procedures can impact analysis results. Four different choices both for the mesh size (from 20 k elements to 200 k elements) and for the material model (from rigid to hyperelastic anisotropic) are considered. Different approaches for modeling calcifications are also taken into account. Post-operative CT data of the real implant are used as reference solution with the aim of outlining a trade-off between computational model complexity and reliability of the results. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.
3D Finite Element Modeling of Single Bolt Connections under Static and Dynamic Tension Loading
Directory of Open Access Journals (Sweden)
Emily Guzas
2015-01-01
Full Text Available The Naval Undersea Warfare Center has funded research to examine a range of finite element approaches used for modeling bolted connections subjected to various loading conditions. Research focused on developing finite element bolt representations that were accurate and computationally efficient. A variety of finite element modeling approaches, from detailed models to simplified ones, were used to represent the behavior of single solid bolts under static and dynamic tension loading. Test cases utilized models of bolted connection test arrangements (static tension and dynamic tension developed for previous research and validated against test data for hollow bore bolts (Behan et al., 2013. Simulation results for solid bolts are validated against experimental data from physical testing of bolts in these load configurations.
Vande Geest, Jonathan P; Simon, B R; Rigby, Paul H; Newberg, Tyler P
2011-04-01
Finite element models (FEMs) including characteristic large deformations in highly nonlinear materials (hyperelasticity and coupled diffusive/convective transport of neutral mobile species) will allow quantitative study of in vivo tissues. Such FEMs will provide basic understanding of normal and pathological tissue responses and lead to optimization of local drug delivery strategies. We present a coupled porohyperelastic mass transport (PHEXPT) finite element approach developed using a commercially available ABAQUS finite element software. The PHEXPT transient simulations are based on sequential solution of the porohyperelastic (PHE) and mass transport (XPT) problems where an Eulerian PHE FEM is coupled to a Lagrangian XPT FEM using a custom-written FORTRAN program. The PHEXPT theoretical background is derived in the context of porous media transport theory and extended to ABAQUS finite element formulations. The essential assumptions needed in order to use ABAQUS are clearly identified in the derivation. Representative benchmark finite element simulations are provided along with analytical solutions (when appropriate). These simulations demonstrate the differences in transient and steady state responses including finite deformations, total stress, fluid pressure, relative fluid, and mobile species flux. A detailed description of important model considerations (e.g., material property functions and jump discontinuities at material interfaces) is also presented in the context of finite deformations. The ABAQUS-based PHEXPT approach enables the use of the available ABAQUS capabilities (interactive FEM mesh generation, finite element libraries, nonlinear material laws, pre- and postprocessing, etc.). PHEXPT FEMs can be used to simulate the transport of a relatively large neutral species (negligible osmotic fluid flux) in highly deformable hydrated soft tissues and tissue-engineered materials.
Model tests and elasto-plastic finite element analysis on multicavity type PCRV
International Nuclear Information System (INIS)
Nojiri, Y.; Yamazaki, M.; Kotani, K.; Matsuzaki, Y.
1978-01-01
Multicavity type PCRV models were tested to investigate elastic stress distributions, cracking and failure mode of the models, and to determine the adequacy and relative accuracy of finite element structural analyses. The behavior of the models under pressure was investigated, and it was found that the predictions of the analyses showed a good agreement with the test results
Yucesoy, C.A.; Huijing, P.A.J.B.M.; Koopman, Hubertus F.J.M.; Grootenboer, H.J.
2002-01-01
In previous applications of the finite element method in modeling mechanical behavior of skeletal muscle, the passive and active properties of muscle tissue were lumped in one finite element. Although this approach yields increased understanding of effects of force transmission, it does not support
Statistical finite element analysis.
Khalaji, Iman; Rahemifar, Kaamran; Samani, Abbas
2008-01-01
A novel technique is introduced for tissue deformation and stress analysis. Compared to the conventional Finite Element method, this technique is orders of magnitude faster and yet still very accurate. The proposed technique uses preprocessed data obtained from FE analyses of a number of similar objects in a Statistical Shape Model framework as described below. This technique takes advantage of the fact that the body organs have limited variability, especially in terms of their geometry. As such, it is well suited for calculating tissue displacements of body organs. The proposed technique can be applied in many biomedical applications such as image guided surgery, or virtual reality environment development where tissue behavior is simulated for training purposes.
A sliding point contact model for the finite element structures code EURDYN
International Nuclear Information System (INIS)
Smith, B.L.
1986-01-01
A method is developed by which sliding point contact between two moving deformable structures may be incorporated within a lumped mass finite element formulation based on displacements. The method relies on a simple mechanical interpretation of the contact constraint in terms of equivalent nodal forces and avoids the use of nodal connectivity via a master slave arrangement or pseudo contact element. The methodology has been iplemented into the EURDYN finite element program for the (2D axisymmetric) version coupled to the hydro code SEURBNUK. Sample calculations are presented illustrating the use of the model in various contact situations. Effects due to separation and impact of structures are also included. (author)
International Nuclear Information System (INIS)
Choi, S. N.; Kim, H. N.; Jang, K. S.; Kim, H. J.
2000-01-01
The purpose of this paper is to determine a two dimensional axisymmetric model through a comparative study between a three dimensional and an axisymmetric finite element analysis of the reactor coolant piping nozzle subject to internal pressure. The finite element analysis results show that the stress adopting the axisymmetric model with the radius of equivalent spherical vessel are well agree with that adopting the three dimensional model. The radii of equivalent spherical vessel are 3.5 times and 7.3 times of the radius of the reactor coolant piping for the safety injection nozzle and for the residual heat removal nozzle, respectively
Ahn, Tae-Soo; Baek, Moo-Jin; Lee, Dooho
2013-01-01
The middle ear consists of a tympanic membrane, ligaments, tendons, and three ossicles. An important function of the tympanic membrane is to deliver exterior sound stimulus to the ossicles and inner ear. In this study, the responses of the tympanic membrane in a human ear were measured and compared with those of a finite element model of the middle ear. A laser Doppler vibrometer (LDV) was used to measure the dynamic responses of the tympanic membrane, which had the measurement point on the cone of light of the tympanic membrane. The measured subjects were five Korean male adults and a cadaver. The tympanic membranes were stimulated using pure-tone sine waves at 18 center frequencies of one-third octave band over a frequency range of 200 Hz ~10 kHz with 60 and 80 dB sound pressure levels. The measured responses were converted into the umbo displacement transfer function (UDTF) with a linearity assumption. The measured UDTFs were compared with the calculated UDTFs using a finite element model for the Korean human middle ear. The finite element model of the middle ear consists of three ossicles, a tympanic membrane, ligaments, and tendons. In the finite element model, the umbo displacements were calculated under a unit sound pressure on the tympanic membrane. The UDTF of the finite element model exhibited good agreement with that of the experimental one in low frequency range, whereas in higher frequency band, the two response functions deviated from each other, which demonstrates that the finite element model should be updated with more accurate material properties and/or a frequency dependent material model.
3-d finite element model development for biomechanics: a software demonstration
Energy Technology Data Exchange (ETDEWEB)
Hollerbach, K.; Hollister, A.M.; Ashby, E.
1997-03-01
Finite element analysis is becoming an increasingly important part of biomechanics and orthopedic research, as computational resources become more powerful, and data handling algorithms become more sophisticated. Until recently, tools with sufficient power did not exist or were not accessible to adequately model complicated, three-dimensional, nonlinear biomechanical systems. In the past, finite element analyses in biomechanics have often been limited to two-dimensional approaches, linear analyses, or simulations of single tissue types. Today, we have the resources to model fully three-dimensional, nonlinear, multi-tissue, and even multi-joint systems. The authors will present the process of developing these kinds of finite element models, using human hand and knee examples, and will demonstrate their software tools.
An adaptive finite element model for hemolysis prediction
International Nuclear Information System (INIS)
Lacasse, D.; Pelletier, D.; Garon, A.
2002-01-01
This paper presents a numerical tool to predict hemolysis caused by mechanical devices that come in contact with blood. Predictions of hemolysis are obtained as a field variable H L , defined as an hemolysis index that takes values between 0 and 1. The field of H L is obtained by solving a hyperbolic equation using the discontinuous Galerkin method. Instead of solving the equation on a element by element basis, as normally done with this method, elemental systems are assembled in a global matrix. The technique readily yields solutions over any computational domain, including domains with recirculating flow fields. An adaptive remeshing algorithm is used to obtain grid independent results of hemolysis for a laminar flow of blood (Re=1600) in a pipe with a sudden contraction. (author)
Material Models and Properties in the Finite Element Analysis of Knee Ligaments: A Literature Review
Galbusera, Fabio; Freutel, Maren; Dürselen, Lutz; D’Aiuto, Marta; Croce, Davide; Villa, Tomaso; Sansone, Valerio; Innocenti, Bernardo
2014-01-01
Knee ligaments are elastic bands of soft tissue with a complex microstructure and biomechanics, which are critical to determine the kinematics as well as the stress bearing behavior of the knee joint. Their correct implementation in terms of material models and properties is therefore necessary in the development of finite element models of the knee, which has been performed for decades for the investigation of both its basic biomechanics and the development of replacement implants and repair strategies for degenerative and traumatic pathologies. Indeed, a wide range of element types and material models has been used to represent knee ligaments, ranging from elastic unidimensional elements to complex hyperelastic three-dimensional structures with anatomically realistic shapes. This paper systematically reviews literature studies, which described finite element models of the knee, and summarizes the approaches, which have been used to model the ligaments highlighting their strengths and weaknesses. PMID:25478560
ANSYS duplicate finite-element checker routine
Ortega, R.
1995-01-01
An ANSYS finite-element code routine to check for duplicated elements within the volume of a three-dimensional (3D) finite-element mesh was developed. The routine developed is used for checking floating elements within a mesh, identically duplicated elements, and intersecting elements with a common face. A space shuttle main engine alternate turbopump development high pressure oxidizer turbopump finite-element model check using the developed subroutine is discussed. Finally, recommendations are provided for duplicate element checking of 3D finite-element models.
Multi-scale simulation method with coupled finite/discrete element model and its application
Fang, Xiwu; Liu, Zhenyu; Tan, Jianrong; Qiu, Chan; Chen, Fengbei
2013-07-01
The existing research on continuous structure is usually analyzed with finite element method (FEM) and granular medium with discrete element method (DEM), but there are few researches on the coupling interaction between continuous structure and discrete medium. To the issue of this coupling interaction, a multi-scale simulation method with coupled finite/discrete element model is put forward, in their respective domains of discrete and finite elements, the nodes follow force law and motion law of their own method, and on the their interaction interface, the touch type between discrete and finite elements is distinguished as two types: full touch and partial touch, the interaction force between them is calculated with linear elastic model. For full touch, the contact force is proportional to the overlap distance between discrete element and finite element patch. For partial touch, first the finite element patch is extended on all sides indefinitely to be a complete plane, the full contact force can be obtained with the touch type between discrete element and plane being viewed as full touch, then the full overlap area between them and the actual overlap area between discrete element and finite element patch are computed, the actual contact force is obtained by scaling the full contact force with a factor η which is determined by the ratio of the actual overlap area to the full overlap area. The contact force is equivalent to the finite element nodes and the force and displacement on the nodes can be computed, so the ideal simulation results can be got. This method has been used to simulate the cutter disk of the earth pressure balance shield machine (EPBSM) made in North Heavy Industry (NHI) with its excavation diameter of 6.28 m cutting and digging the sandy clay layer. The simulation results show that as the gradual increase of excavating depth of the cutter head, the maximum stress occurs at the roots of cutters on the cutter head, while for the soil, the
Application of the Single Hardening Model in the Finite Element Program ABAQUS
DEFF Research Database (Denmark)
Jakobsen, Kim Parsberg
or in combined deformation and flow problems. Today, many of these problems are solved using various finite element computer softwares, capable of handling both geometric and material non-linearities. The latter is especially important in soil mechanics and soil-structure interaction problems. Despite the feat...... model, developed by Lade and Kim (Kim & Lade 1988, Lade & Kim 1988a, Lade & Kim 1988b) is implemented as a user defined material module, UMAT, in the commercial finite element program, ABAQUS. The advantages of the Single Hardening Model Iie in its ability to predict elastic and plastic displacements...
Hindle, D.; Malz, A.; Donndorf, S.; Kley, J.; Kopp, H.
2012-04-01
We develop a coupled numerical model for fluid flow in deforming sedimentary basins. We combine a distinct element method for large deformations of crustal materials, with a finite element method for fluid flow according to a diffusion type equation. The key question in such a model is how to simulate evolving permeabilities due to upper and possibly middle crustal deformation, and the coupled issue of how localisation of deformation in faults and shear zones is itself influenced by fluid flow and fluid pressure and vice versa. Currently our knowledge of these issues is restricted, even sketchy. There are a number of hypotheses, based partly on geological and isotope geochemical observations, such as "seismic pumping" models, and fluid induced weak décollement models for thrust sheet transport which have gained quite wide acceptance. Observations around thrusts at the present day have also often been interpreted as showing deformation induced permeability. However, combining all the physics of these processes into a numerical simulation is a complicated task given the ranges of, in particular time scales of the processes we infer to be operating based on our various observations. We start this task by using an elastic fracture relationship between normal stresses across distinct element contacts (which we consider to be the equivalent of discrete, sliding fractures) and their openness and hence their transmissivity. This relates the mechanical state of the distinct element system to a discrete permeability field. Further than that, the geometry of the mechanical system is used to provide boundary conditions for fluid flow in a diffusion equation which also incorporates the permeability field. The next question we address is how to achieve a feedback between fluid pressures and deformation. We try two approaches: one treats pore space in the DEM as real, and calculates the force exerted locally by fluids and adds this to the force balance of the model; another
Development of a finite element model of the Thor crash test dummy
2000-03-06
The paper describes the development of a detailed finite element model of the new advanced frontal crash test dummy, Thor. The Volpe Center is developing the model for LS-DYNA in collaboration with GESAC, the dummy hardware developer, under the direc...
Real-time volumetric deformable models for surgery simulation using finite elements and condensation
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Cotin, S.
1996-01-01
This paper discusses the application of SD solid volumetric Finite Element models to surgery simulation. In particular it introduces three new ideas for solving the problem of achieving real-time performance for these models. The simulation system we have developed is described and we demonstrate...... real-time deformation using the methods developed in the paper....
A finite element model for the stress and flexibility analysis of curved pipes
International Nuclear Information System (INIS)
Guerreiro, J.N.C.
1987-03-01
We present a finite element model for the analysis of pipe bends with flanged ends or flanged tangents. Comments are made on the consideration of the internal pressure load. Flexibility and stress instensification factores obtained with the present model are compared with others available. (Author) [pt
Vermolen, F.J.; Javierre, E.
2011-01-01
A simplified finite-element model for wound healing is proposed. The model takes into account the sequential steps of dermal regeneration, wound contraction, angiogenesis and wound closure. An innovation in the present study is the combination of the aforementioned partially overlapping processes,
Real-time volumetric deformable models for surgery simulation using finite elements and condensation
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Cotin, S.
1996-01-01
This paper discusses the application of SD solid volumetric Finite Element models to surgery simulation. In particular it introduces three new ideas for solving the problem of achieving real-time performance for these models. The simulation system we have developed is described and we demonstrate...
Creating a Test-Validated Finite-Element Model of the X-56A Aircraft Structure
Pak, Chan-Gi; Truong, Samson
2014-01-01
Small modeling errors in a finite-element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the X-56A Multi-Utility Technology Testbed aircraft is the flight demonstration of active flutter suppression and, therefore, in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground-vibration test-validated structural dynamic finite-element model of the X-56A aircraft is created in this study. The structural dynamic finite-element model of the X-56A aircraft is improved using a model-tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, whereas other properties such as c.g. location, total weight, and off-diagonal terms of the mass orthogonality matrix were used as constraints. The end result was an improved structural dynamic finite-element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.
Finite element based bladder modeling for image-guided radiotherapy of bladder cancer
Chai, Xiangfei; van Herk, Marcel; van de Kamer, Jeroen B.; Hulshof, Maarten C. C. M.; Remeijer, Peter; Lotz, Heidi T.; Bel, Arjan
2011-01-01
Purpose: A biomechanical model was constructed to give insight into pelvic organ motion as a result of bladder filling changes. Methods: The authors used finite element (FE) modeling to simulate bladder wall deformation caused by urine inflow. For ten volunteers, a series of MRI scans of the pelvic
Generation of 3-D finite element models of restored human teeth using micro-CT techniques.
Verdonschot, N.J.J.; Fennis, W.M.M.; Kuys, R.H.; Stolk, J.; Kreulen, C.M.; Creugers, N.H.J.
2001-01-01
PURPOSE: This article describes the development of a three-dimensional finite element model of a premolar based on a microscale computed tomographic (CT) data-acquisition technique. The development of the model is part of a project studying the optimal design and geometry of adhesive tooth-colored
Finite element modelling of electric currents in AC submerged arc furnaces
CSIR Research Space (South Africa)
Mc Dougall, I
2007-01-01
Full Text Available Finite element models were generated of two submerged arc furnaces of different geometries. A 48MW circular furnace and a 68MW 6-in-line rectangular furnace were studied. The electrodes, raw material, slag and molten metal were included in the model...
Robbins, Joshua; Voth, Thomas
2007-06-01
The eXtended Finite Element Method (X-FEM) is a finite element based discretization technique developed originally to model dynamic crack propagation [1]. Since that time the method has been used for modeling physics ranging from static mesoscale material failure to dendrite growth. Here we adapt the recent advances of Benson et al. [2] and Belytchko et al. [3] to model shock loading of polycrystalline material. Through several demonstration problems we evaluate the method for modeling the shock response of polycrystalline materials at the mesoscale. Specifically, we use the X-FEM to model grain boundaries. This approach allows us to i) eliminate ad-hoc mixture rules for multi-material elements and ii) avoid explicitly meshing grain boundaries. ([1] N. Moes, J. Dolbow, J and T. Belytschko, 1999,``A finite element method for crack growth without remeshing,'' International Journal for Numerical Methods in Engineering, 46, 131-150. [2] E. Vitali, and D. J. Benson, 2006, ``An extended finite element formulation for contact in multi-material arbitrary Lagrangian-Eulerian calculations,'' International Journal for Numerical Methods in Engineering, 67, 1420-1444. [3] J-H Song, P. M. A. Areias and T. Belytschko, 2006, ``A method for dynamic crack and shear band propagation with phantom nodes,'' International Journal for Numerical Methods in Engineering, 67, 868-893.)
Fei, Qi; Li, Qiu-jun; Yang, Yong; Li, Dong; Tang, Hai; Li, Jin-jun; Wang, Bing-qiang; Wang, Yi-peng
2010-11-09
To build a three-dimensional finite element model of thoracolumbar spine with osteoporotic vertebral compression fracture (OVCF) and analyze its biomechanical change. The T10-L2 segment data were obtained from computed tomography (CT) scans of an elderly female with a single T12 OVCF. A three-dimensional finite element model of thoracolumbar spine was constructed with the MIMICS and ABAQUS software. The model was composed of bony vertebrae, articulating facets, intervertebral disc and associated ligaments. The basic stress analysis of T10-L2 motion segment was made for different material properties of bone, ligaments and facet joints contacting frictional property. The stress on the annulus fiber, nucleus pulposus, endplate and facet joints under axial pressure (0.3 MPa, 1.0 MPa, 4.0 MPa) were analyzed. A three-dimensional finite element model of human T12-L2 motion segment had 617468 elements. And the stress was higher in vertebral body than posterior structure. The distribution of pressure stresses in intervertebral disc was asymmetrical. The stress increased with a rising axial pressure. 3D finite element model of thoracolumbar OVCF and adjacent segments are successfully established. The results of stress analysis are both feasible and reliable.
Construction and validation of a three-dimensional finite element model of degenerative scoliosis.
Zheng, Jie; Yang, Yonghong; Lou, Shuliang; Zhang, Dongsheng; Liao, Shenghui
2015-12-24
With the aging of the population, degenerative scoliosis (DS) incidence rate is increasing. In recent years, increasing research on this topic has been carried out, yet biomechanical research on the subject is seldom seen and in vitro biomechanical model of DS nearly cannot be available. The objective of this study was to develop and validate a complete three-dimensional finite element model of DS in order to build the digital platform for further biomechanical study. A 55-year-old female DS patient (Suer Pan, ID number was P141986) was selected for this study. This study was performed in accordance with the ethical standards of Declaration of Helsinki and its amendments and was approved by the local ethics committee (117 hospital of PLA ethics committee). Spiral computed tomography (CT) scanning was conducted on the patient's lumbar spine from the T12 to S1. CT images were then imported into a finite element modeling system. A three-dimensional solid model was then formed from segmentation of the CT scan. The three-dimensional model of each vertebra was then meshed, and material properties were assigned to each element according to the pathological characteristics of DS. Loads and boundary conditions were then applied in such a manner as to simulate in vitro biomechanical experiments conducted on lumbar segments. The results of the model were then compared with experimental results in order to validate the model. An integral three-dimensional finite element model of DS was built successfully, consisting of 113,682 solid elements, 686 cable elements, 33,329 shell elements, 4968 target elements, 4968 contact elements, totaling 157,635 elements, and 197,374 nodes. The model accurately described the physical features of DS and was geometrically similar to the object of study. The results of analysis with the finite element model agreed closely with in vitro experiments, validating the accuracy of the model. The three-dimensional finite element model of DS built in
Directory of Open Access Journals (Sweden)
V. A. Zverev
2016-01-01
Full Text Available The article objective is to justify the rationale for selecting the multilayer finite element model parameters of the bearing structure of a general-purpose launch complex unit.A typical design element of the launch complex unit, i.e. a mount of the hydraulic or pneumatic cylinder, block, etc. is under consideration. The mount represents a set of the cantilevered axis and external structural cage. The most loaded element of the cage is disk to which a moment is transferred from the cantilevered axis due to actuator effort acting on it.To calculate the stress-strain state of disk was used a finite element method. Five models of disk mount were created. The only difference in models was the number of layers of the finite elements through the thickness of disk. There were models, which had one, three, five, eight, and fourteen layers of finite elements through the thickness of disk. For each model, we calculated the equivalent stresses arising from the action of the test load. Disk models were formed and calculated using the MSC Nastran complex software.The article presents results in the table to show data of equivalent stresses in each of the multi-layered models and graphically to illustrate the changing equivalent stresses through the thickness of disk.Based on these results we have given advice on selecting the proper number of layers in the model allowing a desirable accuracy of results with the lowest run time. In addition, it is concluded that there is a need to use the multi-layer models in assessing the performance of structural elements in case the stress exceeds the allowable one in their surface layers.
Weiser, Martin
2016-01-01
All relevant implementation aspects of finite element methods are discussed in this book. The focus is on algorithms and data structures as well as on their concrete implementation. Theory is covered as far as it gives insight into the construction of algorithms. Throughout the exercises a complete FE-solver for scalar 2D problems will be implemented in Matlab/Octave.
Validation Assessment of a Glass-to-Metal Seal Finite-Element Model
Energy Technology Data Exchange (ETDEWEB)
Jamison, Ryan Dale [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Emery, John M [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Romero, Vicente J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stavig, Mark E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Newton, Clay S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brown, Arthur [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-10-01
Sealing glasses are ubiquitous in high pressure and temperature engineering applications, such as hermetic feed-through electrical connectors. A common connector technology are glass-to-metal seals where a metal shell compresses a sealing glass to create a hermetic seal. Though finite-element analysis has been used to understand and design glass-to-metal seals for many years, there has been little validation of these models. An indentation technique was employed to measure the residual stress on the surface of a simple glass-to-metal seal. Recently developed rate- dependent material models of both Schott 8061 and 304L VAR stainless steel have been applied to a finite-element model of the simple glass-to-metal seal. Model predictions of residual stress based on the evolution of material models are shown. These model predictions are compared to measured data. Validity of the finite- element predictions is discussed. It will be shown that the finite-element model of the glass-to-metal seal accurately predicts the mean residual stress in the glass near the glass-to-metal interface and is valid for this quantity of interest.
Transport and dispersion of pollutants in surface impoundments: a finite element model
International Nuclear Information System (INIS)
Yeh, G.T.
1980-07-01
A surface impoundment model in finite element (SIMFE) is presented to enable the simulation of flow circulations and pollutant transport and dispersion in natural or artificial lakes, reservoirs or ponds with any number of islands. This surface impoundment model consists of two sub-models: hydrodynamic and pollutant transport models. Both submodels are simulated by the finite element method. While the hydrodynamic model is solved by the standard Galerkin finite element scheme, the pollutant transport model can be solved by any of the twelve optional finite element schemes built in the program. Theoretical approximations and the numerical algorithm of SIMFE are described. Detail instruction of the application are given and listing of FORTRAN IV source program are provided. Two sample problems are given. One is for an idealized system with a known solution to show the accuracy and partial validation of the models. The other is applied to Prairie Island for a set of hypothetical input data, typifying a class of problems to which SIMFE may be applied
Transport and dispersion of pollutants in surface impoundments: a finite element model
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.
1980-07-01
A surface impoundment model in finite element (SIMFE) is presented to enable the simulation of flow circulations and pollutant transport and dispersion in natural or artificial lakes, reservoirs or ponds with any number of islands. This surface impoundment model consists of two sub-models: hydrodynamic and pollutant transport models. Both submodels are simulated by the finite element method. While the hydrodynamic model is solved by the standard Galerkin finite element scheme, the pollutant transport model can be solved by any of the twelve optional finite element schemes built in the program. Theoretical approximations and the numerical algorithm of SIMFE are described. Detail instruction of the application are given and listing of FORTRAN IV source program are provided. Two sample problems are given. One is for an idealized system with a known solution to show the accuracy and partial validation of the models. The other is applied to Prairie Island for a set of hypothetical input data, typifying a class of problems to which SIMFE may be applied.
Development of a Granular Media Model for Finite Element Analysis
National Research Council Canada - National Science Library
SMith, Donald
2001-01-01
.... The model was evolved from a mechanistic interpretation of endochronic theory, which creates a modular system that can accommodate plasticity, visco-elasticity/plasticity, and damage within a single modeling format. The performance of the model is illustrated with the analysis of permanent deformations in a flexible pavement caused by repeated tire loads.
A Kriging Model Based Finite Element Model Updating Method for Damage Detection
Directory of Open Access Journals (Sweden)
Xiuming Yang
2017-10-01
Full Text Available Model updating is an effective means of damage identification and surrogate modeling has attracted considerable attention for saving computational cost in finite element (FE model updating, especially for large-scale structures. In this context, a surrogate model of frequency is normally constructed for damage identification, while the frequency response function (FRF is rarely used as it usually changes dramatically with updating parameters. This paper presents a new surrogate model based model updating method taking advantage of the measured FRFs. The Frequency Domain Assurance Criterion (FDAC is used to build the objective function, whose nonlinear response surface is constructed by the Kriging model. Then, the efficient global optimization (EGO algorithm is introduced to get the model updating results. The proposed method has good accuracy and robustness, which have been verified by a numerical simulation of a cantilever and experimental test data of a laboratory three-story structure.
Calibration of a finite element composite delamination model by experiments
DEFF Research Database (Denmark)
Gaiotti, M.; Rizzo, C.M.; Branner, Kim
2013-01-01
by a previously established modeling strategy (Branner et al., 2011; Gaiotti & Rizzo, 2011), using a pure shell model where the delamination is accounted for by properly offsetting its surfaces and connecting them to the intact plate via rigid link constraining algorithms. The numerical model developed...... modes related to the production methods is presented in this paper. A microscopic analysis of the fracture surfaces was carried out in order to better understand the failure mechanisms. © 2013 Taylor & Francis Group....
Dispersion analysis of the Pn -Pn-1DG mixed finite element pair for atmospheric modelling
Melvin, Thomas
2018-02-01
Mixed finite element methods provide a generalisation of staggered grid finite difference methods with a framework to extend the method to high orders. The ability to generate a high order method is appealing for applications on the kind of quasi-uniform grids that are popular for atmospheric modelling, so that the method retains an acceptable level of accuracy even around special points in the grid. The dispersion properties of such schemes are important to study as they provide insight into the numerical adjustment to imbalance that is an important component in atmospheric modelling. This paper extends the recent analysis of the P2 - P1DG pair, that is a quadratic continuous and linear discontinuous finite element pair, to higher polynomial orders and also spectral element type pairs. In common with the previously studied element pair, and also with other schemes such as the spectral element and discontinuous Galerkin methods, increasing the polynomial order is found to provide a more accurate dispersion relation for the well resolved part of the spectrum but at the cost of a number of unphysical spectral gaps. The effects of these spectral gaps are investigated and shown to have a varying impact depending upon the width of the gap. Finally, the tensor product nature of the finite element spaces is exploited to extend the dispersion analysis into two-dimensions.
Plan, formulate, and discuss a NASTRAN finite element model of the UH-60A helicopter airframe
Dinyovszky, P.; Twomey, W. J.
1990-01-01
Under a rotorcraft structural dynamics program sponsored by the NASA Langley Research Center, Sikorsky Aircraft, together with the other major helicopter airframe manufacturers, is engaged in a study to improve the use of finite element analysis to predict the dynamic behavior of helicopter airframes. This program, which was designated DAMVIBS (Design Analysis Methods for VIBrationS), includes activities in the areas of: planning, creating, and documenting finite element models of helicopter airframes; the performance of ground vibration tests; and the correlation of test and analysis. The work performed at Sikorsky Aircraft for planning, creating, and documenting a finite element model of the UH-60A BLACK HAWK helicopter airframe is summarized. A complete description of the components of the helicopter which are to be represented in the model is presented and includes: the structural arrangement, the identification of primary and secondary structure, the components of the drive and power trains, and the attachment of large weight items to the structure. Also presented are the techniques which were used to formulate the structural finite element model for static analysis, for forming the mass and vibration models for dynamic analysis, and the procedures which were used to check out and verify the integrity of the model. Initial predictions for the vibration modes for the helicopter are included.
Experimental Studies on Finite Element Model Updating for a Heated Beam-Like Structure
Directory of Open Access Journals (Sweden)
Kaipeng Sun
2015-01-01
Full Text Available An experimental study was made for the identification procedure of time-varying modal parameters and the finite element model updating technique of a beam-like thermal structure in both steady and unsteady high temperature environments. An improved time-varying autoregressive method was proposed first to extract the instantaneous natural frequencies of the structure in the unsteady high temperature environment. Based on the identified modal parameters, then, a finite element model for the structure was updated by using Kriging meta-model and optimization-based finite-element model updating method. The temperature-dependent parameters to be updated were expressed as low-order polynomials of temperature increase, and the finite element model updating problem was solved by updating several coefficients of the polynomials. The experimental results demonstrated the effectiveness of the time-varying modal parameter identification method and showed that the instantaneous natural frequencies of the updated model well tracked the trends of the measured values with high accuracy.
Finite Elements Contact Modelling of Planetary Gear Trains
Stoyanov, Svetlin; Dobrev, Vasko; Dobreva, Antoaneta
2017-10-01
The paper presents the application aspects of computer technologies concerning the process of creating theoretical contact models of planetary gear trains using Abaqus/Explicit. The necessary assumptions, constrains and specific features of these gear drives are discussed in details. The models created are appropriate and useful tools for computer simulation research of the dynamic behaviour of planetary gear trains.
Zeng, Zhi-Li; Cheng, Li-Ming; Zhu, Rui; Wang, Jian-Jie; Yu, Yan
2011-08-23
To build an effective nonlinear three-dimensional finite-element (FE) model of T(11)-L(3) segments for a further biomechanical study of thoracolumbar spine. The CT (computed tomography) scan images of healthy adult T(11)-L(3) segments were imported into software Simpleware 2.0 to generate a triangular mesh model. Using software Geomagic 8 for model repair and optimization, a solid model was generated into the finite element software Abaqus 6.9. The reasonable element C3D8 was selected for bone structures. Created between bony endplates, the intervertebral disc was subdivided into nucleus pulposus and annulus fibrosus (44% nucleus, 56% annulus). The nucleus was filled with 5 layers of 8-node solid elements and annulus reinforced by 8 crisscross collagenous fiber layers. The nucleus and annulus were meshed by C3D8RH while the collagen fibers meshed by two node-truss elements. The anterior (ALL) and posterior (PLL) longitudinal ligaments, flavum (FL), supraspinous (SSL), interspinous (ISL) and intertransverse (ITL) ligaments were modeled with S4R shell elements while capsular ligament (CL) was modeled with 3-node shell element. All surrounding ligaments were represented by envelope of 1 mm uniform thickness. The discs and bone structures were modeled with hyper-elastic and elasto-plastic material laws respectively while the ligaments governed by visco-elastic material law. The nonlinear three-dimensional finite-element model of T(11)-L(3) segments was generated and its efficacy verified through validating the geometric similarity and disc load-displacement and stress distribution under the impact of violence. Using ABAQUS/ EXPLICIT 6.9 the explicit dynamic finite element solver, the impact test was simulated in vitro. In this study, a 3-dimensional, nonlinear FE model including 5 vertebrae, 4 intervertebral discs and 7 ligaments consisted of 78 887 elements and 71 939 nodes. The model had good geometric similarity under the same conditions. The results of FEM
Development of a two-dimensional finite element plasma edge model
International Nuclear Information System (INIS)
Vesey, R.A.
1992-01-01
The fluid equations modeling plasma transport in the tokamak scrape-off region are discretized via optimal upwind finite element methods developed for convection-dominated problems. These methods allow the non-orthogonal geometry of the edge region to be represented accurately, while applying the necessary boundary conditions. Newton's method with mesh sequencing is used to arrive at a converged solution to the resulting nonlinear algebraic system of equations. Preliminary results are presented for a 20x20 finite element discretization of the ASDEX edge region, with some simplifications. General agreement between the finite element solution and the Braams code B2 is observed. The code will be extended to allow equilibrium-based meshes and arbitrary boundary geometries
Finite-element modeling of loading of spring from an orthotropic material
Veremeenko, Andrey; Chepurnenko, Anton; Shvetsov, Pavel; Zorchenko, Lidiia; Yazyev, Serdar
2017-10-01
In the paper, the stress-strain state of the springs from carbon fiber reinforced plastic was analyzed at its loading by a vertical load. The orthotropy of the material was taken into account. The solution was implemented in the software complexes Lira, ANSYS, and also using the program specially developed by the authors in the Matlab package. In the first case, the part was modeled by three-dimensional finite elements in the form of tetrahedral. In Lira and Matlab we used the plane finite elements of the plates. Comparison of the results obtained in three software complexes is given.
Evaluation of the finite element software ABAQUS for biomechanical modelling of biphasic tissues.
Wu, J Z; Herzog, W; Epstein, M
1998-02-01
The biphasic cartilage model proposed by Mow et al. (1980) has proven successful to capture the essential mechanical features of articular cartilage. In order to analyse the joint contact mechanics in real, anatomical joints, the cartilage model needs to be implemented into a suitable finite element code to approximate the irregular surface geometries of such joints. However, systematic and extensive evaluation of the capacity of commercial software for modelling the contact mechanics with biphasic cartilage layers has not been made. This research was aimed at evaluating the commercial finite element software ABAQUS for analysing biphasic soft tissues. The solutions obtained using ABAQUS were compared with those obtained using other finite element models and analytical solutions for three numerical tests: an unconfined indentation test, a test with the contact of a spherical cartilage surface with a rigid plate, and an axi-symmetric joint contact test. It was concluded that the biphasic cartilage model can be implemented into the commercial finite element software ABAQUS to analyse practical joint contact problems with biphasic articular cartilage layers.
A finite element model for nonlinear shells of revolution
International Nuclear Information System (INIS)
Cook, W.A.
1979-01-01
A shell-of-revolution model was developed to analyze impact problems associated with the safety analysis of nuclear material shipping containers. The nonlinear shell theory presented by Eric Reissner in 1972 was used to develop our model. Reissner's approach includes transverse shear deformation and moments turning about the middle surface normal. With these features, this approach is valid for both thin and thick shells. His theory is formulated in terms of strain and stress resultants that refer to the undeformed geometry. This nonlinear shell model is developed using the virtual work principle associated with Reissner's equilibrium equations. First, the virtual work principle is modified for incremental loading; then it is linearized by assuming that the nonlinear portions of the strains are known. By iteration, equilibrium is then approximated for each increment. A benefit of this approach is that this iteration process makes it possible to use nonlinear material properties. (orig.)
A High Order Filter with Galerkin Finite Element Method for the Spherical Local domain Model
Lee, C. H.; Cheong, H. B.; Kang, H. G.
2017-12-01
A High Order Filter with Galerkin Finite Element Method for the Spherical Local domain ModelChung-Hui Lee1 and Hyeong-Bin Cheong and Hyun-Gyu KangDepartment of Environmental Atmospheric Sciences, Pukyong National University, Busan, Korea (1 chlee@pukyong.ac.kr) A high-order filter with Galerkin finite element method is constructed by applying a two dimensional finite element method with quadrilateral basis functions to the spherical limited area domain. The quadrilateral basis function is defined as four shape-functions on separate four grid-boxes which share the same gridpoint. A first-order derivative is represented with an algebraic equation consisting of nine point stencil. Helmholtz equation on a sphere is the basic component of the high order filter and the filtering is performed by solving this equation with two dimensional finite element method. As the theory describes, for spherical Laplacian operator and first-order derivative, the convergence rates of the error were revealed to be second-order and fourth-order, respectively. In addition, since the convergence rate of errors for the filter in this study was the same as the filter with Fourier finite element method, the accuracy of the filter is comparable to the filter based on the Fourier finite element method. The high-order filter was applied to the WRF (Weather Research and Forecasting) as hyper-viscosity and its performance was compared with those of the built-in viscosity scheme of the WRF model. As a result of the tropical cyclone simulation, the forecast error for the high-order filter and the built-in viscosity were similar for the minimum pressure and track prediction. However, for the precipitation and rainfall distribution, the prediction with high-order filter appeared closer to observations than those with built-in viscosity.
A cohesive finite element formulation for modelling fracture and ...
Indian Academy of Sciences (India)
an adhesively bonded system is simulated employing the cohesive zone model. ... systems. While such an analysis is useful to predict the behaviour of a system till the point of initiation of crack propagation, its applicability reduces during the propagation phase. In ... CZM, also called embedded process zone (EPZ).
Finite element modelling of elastic intraplate stresses due to ...
Indian Academy of Sciences (India)
Keywords. Elastic stresses; continental crust; intraplate seismicity; rheology; geodynamics; modelling; seismology. Abstract. Deep lower crustal intraplate earthquakes are infrequent and the mechanism of their occurrence is not well understood. The Narmada–Son-lineament region in central India has experienced two such ...
A cohesive finite element formulation for modelling fracture and ...
Indian Academy of Sciences (India)
external (or boundary) load and displacement. This phenomenon may be illustrated through some simple systems involving linear and nonlinear springs. To this end, a linear and a nonlinear spring having load versus displacement characteristics, as shown in figures 3a. Cohesive FE formulation for modelling fracture. 569 ...
Wang, Q; Yang, Y; Fei, Q; Li, D; Li, J J; Meng, H; Su, N; Fan, Z H; Wang, B Q
2017-06-06
Objective: To build a three-dimensional finite element models of a modified posterior cervical single open-door laminoplasty with short-segmental lateral mass screws fusion. Methods: The C(2)-C(7) segmental data were obtained from computed tomography (CT) scans of a male patient with cervical spondylotic myelopathy and spinal stenosis.Three-dimensional finite element models of a modified cervical single open-door laminoplasty (before and after surgery) were constructed by the combination of software package MIMICS, Geomagic and ABAQUS.The models were composed of bony vertebrae, articulating facets, intervertebral disc and associated ligaments.The loads of moments 1.5Nm at different directions (flexion, extension, lateral bending and axial rotation)were applied at preoperative model to calculate intersegmental ranges of motion.The results were compared with the previous studies to verify the validation of the models. Results: Three-dimensional finite element models of the modified cervical single open- door laminoplasty had 102258 elements (preoperative model) and 161 892 elements (postoperative model) respectively, including C(2-7) six bony vertebraes, C(2-3)-C(6-7) five intervertebral disc, main ligaments and lateral mass screws.The intersegmental responses at the preoperative model under the loads of moments 1.5 Nm at different directions were similar to the previous published data. Conclusion: Three-dimensional finite element models of the modified cervical single open- door laminoplasty were successfully established and had a good biological fidelity, which can be used for further study.
Finite elements modeling of delaminations in composite laminates
DEFF Research Database (Denmark)
Gaiotti, m.; Rizzo, C.M.; Branner, Kim
2011-01-01
of the buckling strength of composite laminates containing delaminations. Namely, non-linear buckling and post-buckling analyses are carried out to predict the critical buckling load of elementary composite laminates affected by rectangular delaminations of different sizes and locations, which are modelled......The application of composite materials in many structures poses to engineers the problem to create reliable and relatively simple methods, able to estimate the strength of multilayer composite structures. Multilayer composites, like other laminated materials, suffer from layer separation, i.......e., delaminations, which may affect the stiffness and stability of structural components. Especially deep delaminations in the mid surface of laminates are expected to reduce the effective flexural stiffness and lead to collapse, often due to buckling behaviour. This paper deals with the numerical modelling...
A Multiphysics Finite Element and Peridynamics Model of Dielectric Breakdown
2017-09-01
not just in the temperature-conductivity dependence, but also in the equation of motion and elastic and thermal material properties. Third, the...here, and so in the fu- ture more sophisticated field-dependent conductivity models should be explored. Finally, magneto -static forces may also be...Reformulation of elasticity theory for discontinuities and long-range forces. J Mech Phy Sol. 2000;48(1):175–209. 4. Silling S, Askari E. A meshfree
Finite element modelling of vocal tract changes after voice therapy
Czech Academy of Sciences Publication Activity Database
Vampola, T.; Laukkanen, A. M.; Horáček, Jaromír; Švec, J. G.
2011-01-01
Roč. 5, č. 1 (2011), s. 77-88 ISSN 1802-680X R&D Projects: GA ČR GA101/08/1155 Institutional research plan: CEZ:AV0Z20760514 Keywords : biomechanics of human voice * voice production modelling * vocal excersing * voice training Subject RIV: BI - Acoustics http://www.kme.zcu.cz/acm/index.php/acm/article/view/138
The finite element method for micro-scale modeling of ultrasound propagation in cancellous bone.
Vafaeian, B; El-Rich, M; El-Bialy, T; Adeeb, S
2014-08-01
Quantitative ultrasound for bone assessment is based on the correlations between ultrasonic parameters and the properties (mechanical and physical) of cancellous bone. To elucidate the correlations, understanding the physics of ultrasound in cancellous bone is demanded. Micro-scale modeling of ultrasound propagation in cancellous bone using the finite-difference time-domain (FDTD) method has been so far utilized as one of the approaches in this regard. However, the FDTD method accompanies two disadvantages: staircase sampling of cancellous bone by finite difference grids leads to generation of wave artifacts at the solid-fluid interface inside the bone; additionally, this method cannot explicitly satisfy the needed perfect-slip conditions at the interface. To overcome these disadvantages, the finite element method (FEM) is proposed in this study. Three-dimensional finite element models of six water-saturated cancellous bone samples with different bone volume were created. The values of speed of sound (SOS) and broadband ultrasound attenuation (BUA) were calculated through the finite element simulations of ultrasound propagation in each sample. Comparing the results with other experimental and simulation studies demonstrated the capabilities of the FEM for micro-scale modeling of ultrasound in water-saturated cancellous bone. Copyright © 2014 Elsevier B.V. All rights reserved.
Solid Modeling and Finite Element Analysis of an Overhead Crane Bridge
Directory of Open Access Journals (Sweden)
C. Alkin
2005-01-01
Full Text Available The design of an overhead crane bridge with a double box girder has been investigated and a case study of a crane with 35 ton capacity and 13 m span length has been conducted. In the initial phase of the case study, conventional design calculations proposed by F. E. M. Rules and DIN standards were performed to verify the stress and deflection levels. The crane design was modeled using both solids and surfaces. Finite element meshes with 4-node tetrahedral and 4-node quadrilateral shell elements were generated from the solid and shell models, respectively. After a comparison of the finite element analyses, the conventional calculations and performance of the existing crane, the analysis with quadratic shell elements was found to give the most realistic results. As a result of this study, a design optimization method for an overhead crane is proposed.
Measurement of Temperature and Soil Properties for Finite Element Model Verification
2012-08-01
In recent years, ADOT&PF personnel have used TEMP/W, a commercially available two-dimensional finite element program, to conduct thermal modeling of various : embankment configurations in an effort to reduce the thawing of ice-rich permafrost through...
Accurate Modeling of a Transverse Flux Permanent Magnet Generator Using 3D Finite Element Analysis
DEFF Research Database (Denmark)
Hosseini, Seyedmohsen; Moghani, Javad Shokrollahi; Jensen, Bogi Bech
2011-01-01
This paper presents an accurate modeling method that is applied to a single-sided outer-rotor transverse flux permanent magnet generator. The inductances and the induced electromotive force for a typical generator are calculated using the magnetostatic three-dimensional finite element method. A n...
A Finite Element Model for the Analysis of Bridge Decks | Onyia ...
African Journals Online (AJOL)
However, the method is limited to only simply supported decks. Also, reading the charts and interpolating between curves can be very tiresome and can easily introduce errors in the analysis. This paper therefore proposes and develops a finite element model as a more versatile alternative for the analysis of bridge decks for ...
Cheng Piao; Todd F. Shupe; R.C. Tang; Chung Y. Hse
2008-01-01
Tapered composite poles with biomimicry features as in bamboo are a new generation of wood laminated composite poles that may some day be considered as an alternative to solid wood poles that are widely used in the transmission and telecommunication fields. Five finite element models were developed with ANSYS to predict and assess the performance of five types of...
A nonconforming finite element method for the Biot’s consolidation model in poroelasticity
X. Hu (Xiaozhe); C. Rodrigo (Carmen); F.J. Gaspar Lorenz (Franscisco); C.W. Oosterlee (Cornelis)
2017-01-01
textabstractA stable finite element scheme that avoids pressure oscillations for a three-field Biot’s model in poroelasticity is considered. The involved variables are the displacements, fluid flux (Darcy velocity), and the pore pressure, and they are discretized by using the lowest possible
Finite element modeling of camber evolution during sintering of bi-layers
DEFF Research Database (Denmark)
Tadesse Molla, Tesfaye; Ni, De Wei; Bulatova, Regina
2014-01-01
The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber dev...
Investigation of a Hybrid Winding Concept for Toroidal Inductors using 3D Finite Element Modeling
DEFF Research Database (Denmark)
Schneider, Henrik; Andersen, Thomas; Mønster, Jakob Døllner
2013-01-01
This paper investigates a hybrid winding concept for a toroidal inductor by simulating the winding resistance as a function of frequency. The problem of predicting the resistance of a non-uniform and complex winding shape is solved using 3D Finite Element Modeling. A prototype is built and tested...
Finite Element Modelling of Bends and Creases during Folding Ultra Thin Stainless Steel Foils
Datta, K.; Akagi, H.; Geijselaers, Hubertus J.M.; Huetink, Han
2003-01-01
Finite Element Modelling of an ultra thin foil of SUS 304 stainless steel is carried out. These foils are 20 mm and below in thickness. The development of stresses and strains during folding of these foils is studied. The objective of this study is to induce qualities of paper in the foils of
Multiscale Model Reduction with Generalized Multiscale Finite Element Methods in Geomathematics
Efendiev, Yalchin R.
2015-09-02
In this chapter, we discuss multiscale model reduction using Generalized Multiscale Finite Element Methods (GMsFEM) in a number of geomathematical applications. GMsFEM has been recently introduced (Efendiev et al. 2012) and applied to various problems. In the current chapter, we consider some of these applications and outline the basic methodological concepts.
Energy Technology Data Exchange (ETDEWEB)
Puckett, Anthony D. [Colorado State Univ., Fort Collins, CO (United States)
2000-09-01
The ability to model wave propagation in circular cylindrical bars of finite length numerically or analytically has many applications. In this thesis the capability of an explicit finite element method to model longitudinal waves in cylindrical rods with circular cross-sections is explored. Dispersion curves for the first four modes are compared to the analytical solution to determine the accuracy of various element sizes and time steps. Values for the time step and element size are determined that retain accuracy while minimizing computational time. The modeling parameters are validated by calculating a signal propagated with a broadband input force. Limitations on the applicability are considered along with modeling parameters that should be applicable to more general geometries.
Three-dimensional linear fracture mechanics analysis by a displacement-hybrid finite-element model
International Nuclear Information System (INIS)
Atluri, S.N.; Kathiresan, K.; Kobayashi, A.S.
1975-01-01
This paper deals with a finite-element procedures for the calculation of modes I, II and III stress intensity factors, which vary, along an arbitrarily curved three-dimensional crack front in a structural component. The finite-element model is based on a modified variational principle of potential energy with relaxed continuity requirements for displacements at the inter-element boundary. The variational principle is a three-field principle, with the arbitrary interior displacements for the element, interelement boundary displacements, and element boundary tractions as variables. The unknowns in the final algebraic system of equations, in the present displacement hybrid finite element model, are the nodal displacements and the three elastic stress intensity factors. Special elements, which contain proper square root and inverse square root crack front variations in displacements and stresses, respectively, are used in a fixed region near the crack front. Interelement displacement compatibility is satisfied by assuming an independent interelement boundary displacement field, and using a Lagrange multiplier technique to enforce such interelement compatibility. These Lagrangean multipliers, which are physically the boundary tractions, are assumed from an equilibrated stress field derived from three-dimensional Beltrami (or Maxwell-Morera) stress functions that are complete. However, considerable care should be exercised in the use of these stress functions such that the stresses produced by any of these stress function components are not linearly dependent
Use of the iterative solution method for coupled finite element and boundary element modeling
International Nuclear Information System (INIS)
Koteras, J.R.
1993-07-01
Tunnels buried deep within the earth constitute an important class geomechanics problems. Two numerical techniques used for the analysis of geomechanics problems, the finite element method and the boundary element method, have complementary characteristics for applications to problems of this type. The usefulness of combining these two methods for use as a geomechanics analysis tool has been recognized for some time, and a number of coupling techniques have been proposed. However, not all of them lend themselves to efficient computational implementations for large-scale problems. This report examines a coupling technique that can form the basis for an efficient analysis tool for large scale geomechanics problems through the use of an iterative equation solver
Finite element model updating of a small steel frame using neural networks
International Nuclear Information System (INIS)
Zapico, J L; González, M P; Alonso, R; González-Buelga, A
2008-01-01
This paper presents an experimental and analytical dynamic study of a small-scale steel frame. The experimental model was physically built and dynamically tested on a shaking table in a series of different configurations obtained from the original one by changing the mass and by causing structural damage. Finite element modelling and parameterization with physical meaning is iteratively tried for the original undamaged configuration. The finite element model is updated through a neural network, the natural frequencies of the model being the net input. The updating process is made more accurate and robust by using a regressive procedure, which constitutes an original contribution of this work. A novel simplified analytical model has been developed to evaluate the reduction of bending stiffness of the elements due to damage. The experimental results of the rest of the configurations have been used to validate both the updated finite element model and the analytical one. The statistical properties of the identified modal data are evaluated. From these, the statistical properties and a confidence interval for the estimated model parameters are obtained by using the Latin Hypercube sampling technique. The results obtained are successful: the updated model accurately reproduces the low modes identified experimentally for all configurations, and the statistical study of the transmission of errors yields a narrow confidence interval for all the identified parameters
Crack modeling of rotating blades with cracked hexahedral finite element method
Liu, Chao; Jiang, Dongxiang
2014-06-01
Dynamic analysis is the basis in investigating vibration features of cracked blades, where the features can be applied to monitor health state of blades, detect cracks in an early stage and prevent failures. This work presents a cracked hexahedral finite element method for dynamic analysis of cracked blades, with the purpose of addressing the contradiction between accuracy and efficiency in crack modeling of blades in rotor system. The cracked hexahedral element is first derived with strain energy release rate method, where correction of stress intensity factors of crack front and formulation of load distribution of crack surface are carried out to improve the modeling accuracy. To consider nonlinear characteristics of time-varying opening and closure effects caused by alternating loads, breathing function is proposed for the cracked hexahedral element. Second, finite element method with contact element is analyzed and used for comparison. Finally, validation of the cracked hexahedral element is carried out in terms of breathing effects of cracked blades and natural frequency in different crack depths. Good consistency is acquired between the results with developed cracked hexahedral element and contact element, while the computation time is significantly reduced in the previous one. Therefore, the developed cracked hexahedral element achieves good accuracy and high efficiency in crack modeling of rotating blades.
International Nuclear Information System (INIS)
Ishida, Hitoshi; Meshii, Toshiyuki
2010-01-01
This study proposes an element size selection method named the 'Impact-Meshing (IM) method' for a finite element waves propagation analysis model, which is characterized by (1) determination of element division of the model with strain energy in the whole model, (2) static analysis (dynamic analysis in a single time step) with boundary conditions which gives a maximum change of displacement in the time increment and inertial (impact) force caused by the displacement change. In this paper, an example of application of the IM method to 3D ultrasonic wave propagation problem in an elastic solid is described. These examples showed an analysis result with a model determined by the IM method was convergence and calculation time for determination of element subdivision was reduced to about 1/6 by the IM Method which did not need determination of element subdivision by a dynamic transient analysis with 100 time steps. (author)
DEFF Research Database (Denmark)
Rohde, John; Toftegaard, Thomas Skjødeberg
2012-01-01
Novel parametric finite-element models are provided for discrete SMD capacitors and inductors in the frequency range 100 MHz to 4 GHz. The aim of the models is to facilitate performance optimization and analysis of RF PCB designs integrating these SMD components with layout geometries such as ant......Novel parametric finite-element models are provided for discrete SMD capacitors and inductors in the frequency range 100 MHz to 4 GHz. The aim of the models is to facilitate performance optimization and analysis of RF PCB designs integrating these SMD components with layout geometries...... such as antennas and PCB traces. The models presented are benchmarked against real-life measurements and conventional circuit models. Furthermore, two example parallel-resonance circuits are designed based on interpolation of the results and validated by measurements in order to demonstrate the accuracy...
Modeling Concrete Material Structure: A Two-Phase Meso Finite Element Model
Bonifaz, E. A.; Baus, Juan; Lantsoght, Eva O. L.
Concrete is a compound material where aggregates are randomly placed within the cement paste. To describe the behavior of concrete structures at the ultimate, it is necessary to use nonlinear finite element models, which for shear and torsion problems do not always give satisfactory results. The current study aims at improving the modeling of concrete at the meso-level, which eventually can result in an improved assessment of existing structures. Concrete as a heterogeneous material is modeled consisting of hydrated cement paste and aggregates. The stress-strain curves of the hydrated cement paste and aggregates are described with results from the literature. A three-dimensional (3D) finite element model was developed to determine the influence of individual phases on the inelastic stress-strain distribution of concrete structures. A random distribution and morphology of the cement and aggregate fractions are achieved by using DREAM.3D. Two affordable computational dual-phase representative volume elements (RVEs) are imported to ABAQUS to be studied in compression and tension. The virtual specimens (concrete mesh) subjected to continuous monotonic strain loading conditions were constrained with 3D boundary conditions. Results demonstrate differences in stress-strain mechanical behavior in both compression and tension test simulations. A strong dependency of flow stress and plastic strain on phase type, aggregate (andesite) size, shape and distribution upon the composite local response are clearly observed. It is noted that the resistance to flow is higher in concrete meshes composed of finer and homogeneous aggregate particles because the Misses stresses and effective plastic strains are better distributed. This study shows that at the meso-level, concrete can be modeled consisting of aggregates and hydrated cement paste.
Azar, F S; Metaxas, D N; Schnall, M D
2001-10-01
Live guidance during needle breast procedures is not currently possible with high-field-strength (1.5-T), superconducting magnetic resonance (MR) imaging. The physician can calculate only the approximate location and extent of a tumor in the compressed patient breast before inserting the needle, and the tissue specimen removed at biopsy may not actually belong to the lesion of interest. The authors developed a virtual reality system for guiding breast biopsy with MR imaging, which uses a deformable finite element model of the breast. The geometry of the model is constructed from MR data, and its mechanical properties are modeled by using a nonlinear material model. This method allows the breast to be imaged with or without mild compression before the procedure. The breast is then compressed, and the finite element model is used to predict the position of the tumor during the procedure. Three breasts of patients with cancer were imaged with and without compression. Deformable models of these breasts were built, virtually compressed, and used to predict tumor positions in the real compressed breasts. The models were also used to register MR data sets of the same patient breast imaged with different amounts of compression. The model is shown to predict reasonably well the displacement by plate compression of breast lesions 5 mm or larger. A deformable model of the breast based on finite elements with nonlinear material properties can help in modeling and predicting breast deformation. The entire procedure lasts less than half an hour, making it clinically practical.
Finite Element Modelling of Elastic-Plastic Contact of Rough Surfaces
Abdo, Jamil; Haneef, Danish; Al-Shabibi, Abdullah
2010-01-01
The contact area and contact load of an elastic-plastic micro-contact was calculated. The ultimate stress asperity is embedded at a critical depth within the actual surface asperities. The finite element solution is used to define the limit at which failure is to occur. The present model is more accurate than the previous models since it accounts for the net elasticplastic by subtracting the plastic portion that reached the ultimate-stress asperity limit. Comparisons of the present model with...
Plan, formulate, and discuss a NASTRAN finite element model of the AH-64A helicopter airframe
Christ, Richard A.; Ferg, Douglas A.; Kilroy, Kevin A.; Toossi, Mostafa; Weisenburger, Richard K.
1990-01-01
A discussion of modeling plan objectives, followed by a description of the AH-64A aircraft including all general features, major components, and primary and structure definitions are presented. Following the aircraft description, a discussion of the modeling guidelines and model checkout procedure are provided. The NASTRAN finite element analysis is set up to be suitable to predict both static internal loads and vibrations. Finally, the results, schedule, and planned versus actual manhours for this work are presented.
Energy Technology Data Exchange (ETDEWEB)
Cho, Moon Sung; Suk, Ho Chun
2000-12-01
A static and finite-element (FE) analysis model was developed to simulate out-reactor fuel string strength tests with use of the structural analysis computer code ABAQUS. The FE model takes into account the deflection of fuel elements and stress and displacement in end-plates subjected to hydraulic drag loads. It was adapted to the strength tests performed for CANFLEX 43-element bundles and the existing 37-element bundles. The FE model was found to be in good agreement with the experiment results. With use of the FE model, the static behavior of the fuel bundle strings, such as load transfer between ring elements, end-plate rib effects, hydraulic drag load incurring plastic deformation in fuel string and hydraulic flow rate effects were investigated.
Triedman, John K.; Jolley, Matthew; Stinstra, Jeroen; Brooks, Dana H.; MacLeod, Rob
2008-01-01
ICD implants may be complicated by body size and anatomy. One approach to this problem has been the adoption of creative, extracardiac implant strategies using standard ICD components. Because data on safety or efficacy of such ad hoc implant strategies is lacking, we have developed image-based finite element models (FEMs) to compare electric fields and expected defibrillation thresholds (DFTs) using standard and novel electrode locations. In this paper, we review recently published studies by our group using such models, and progress in meshing strategies to improve efficiency and visualization. Our preliminary observations predict that they may be large changes in DFTs with clinically relevant variations of electrode placement. Extracardiac ICDs of various lead configurations are predicted to be effective in both children and adults. This approach may aid both ICD development and patient-specific optimization of electrode placement, but the simplified nature of current models dictates further development and validation prior to clinical or industrial utilization. PMID:18817926
Finite element modelling of crash response of composite aerospace sub-floor structures
McCarthy, M. A.; Harte, C. G.; Wiggenraad, J. F. M.; Michielsen, A. L. P. J.; Kohlgrüber, D.; Kamoulakos, A.
Composite energy-absorbing structures for use in aircraft are being studied within a European Commission research programme (CRASURV - Design for Crash Survivability). One of the aims of the project is to evaluate the current capabilities of crashworthiness simulation codes for composites modelling. This paper focuses on the computational analysis using explicit finite element analysis, of a number of quasi-static and dynamic tests carried out within the programme. It describes the design of the structures, the analysis techniques used, and the results of the analyses in comparison to the experimental test results. It has been found that current multi-ply shell models are capable of modelling the main energy-absorbing processes at work in such structures. However some deficiencies exist, particularly in modelling fabric composites. Developments within the finite element code are taking place as a result of this work which will enable better representation of composite fabrics.
Finite Element Model for Failure Study of Two-Dimensional Triaxially Braided Composite
Li, Xuetao; Binienda, Wieslaw K.; Goldberg, Robert K.
2010-01-01
A new three-dimensional finite element model of two-dimensional triaxially braided composites is presented in this paper. This meso-scale modeling technique is used to examine and predict the deformation and damage observed in tests of straight sided specimens. A unit cell based approach is used to take into account the braiding architecture as well as the mechanical properties of the fiber tows, the matrix and the fiber tow-matrix interface. A 0 deg / plus or minus 60 deg. braiding configuration has been investigated by conducting static finite element analyses. Failure initiation and progressive degradation has been simulated in the fiber tows by use of the Hashin failure criteria and a damage evolution law. The fiber tow-matrix interface was modeled by using a cohesive zone approach to capture any fiber-matrix debonding. By comparing the analytical results to those obtained experimentally, the applicability of the developed model was assessed and the failure process was investigated.
A Tensile Constitutive Relationship and a Finite Element Model of Electrospun Nanofibrous Mats
Directory of Open Access Journals (Sweden)
Yunlei Yin
2018-01-01
Full Text Available It is difficult to establish a numerical model for a certain structure of electrospun nanofibrous mats, due to their high porosity and non-linear characteristics, that can fully consider these characteristics and describe their mechanical behaviors. In this paper, an analytical method of meso-mechanics was adopted to establish the tensile constitutive relationship between a single fiber and mats from fiber-web microstructures. Meanwhile, a macroscopic finite element model was developed and verified through uniaxial tensile stress-strain experimental data of silk fibroin (SF/polycaprolactone (PCL nanofibrous mats. The compared results show that the constitutive relation and finite element model could satisfactorily express elastic-plastic tensile mechanical behaviors of the polymer. This model helps regulate the microstructure of nanofibrous mats to meet the mechanical requirements in engineering applications.
A Tensile Constitutive Relationship and a Finite Element Model of Electrospun Nanofibrous Mats.
Yin, Yunlei; Pan, Zhongxiang; Xiong, Jie
2018-01-08
It is difficult to establish a numerical model for a certain structure of electrospun nanofibrous mats, due to their high porosity and non-linear characteristics, that can fully consider these characteristics and describe their mechanical behaviors. In this paper, an analytical method of meso-mechanics was adopted to establish the tensile constitutive relationship between a single fiber and mats from fiber-web microstructures. Meanwhile, a macroscopic finite element model was developed and verified through uniaxial tensile stress-strain experimental data of silk fibroin (SF)/polycaprolactone (PCL) nanofibrous mats. The compared results show that the constitutive relation and finite element model could satisfactorily express elastic-plastic tensile mechanical behaviors of the polymer. This model helps regulate the microstructure of nanofibrous mats to meet the mechanical requirements in engineering applications.
Tissue Modeling and Analyzing with Finite Element Method: A Review for Cranium Brain Imaging
Yue, Xianfang; Wang, Li; Wang, Ruonan
2013-01-01
For the structure mechanics of human body, it is almost impossible to conduct mechanical experiments. Then the finite element model to simulate mechanical experiments has become an effective tool. By introducing several common methods for constructing a 3D model of cranial cavity, this paper carries out systematically the research on the influence law of cranial cavity deformation. By introducing the new concepts and theory to develop the 3D cranial cavity model with the finite-element method, the cranial cavity deformation process with the changing ICP can be made the proper description and reasonable explanation. It can provide reference for getting cranium biomechanical model quickly and efficiently and lay the foundation for further biomechanical experiments and clinical applications. PMID:23476630
Finite element modeling of stress corrosion cracking for electromagnetic nondestructive evaluations
International Nuclear Information System (INIS)
Wang, J.; Yusa, N.; Hashizume, H.
2012-01-01
This paper discusses appropriate numerical model for a stress corrosion crack (SCC) from the viewpoint of anisotropy of their conductivity. Two SCCs, which are introduced into a plate of type 316 stainless steel, are considered. Finite element simulations are carried out to evaluate the conductivity. In the simulations, the cracks are modeled as a region with a constant width on the basis of the destructive tests. The results show the conductivity on direction of width has large effect to the accuracy of numerical modeling of SCC, whereas the conductivities on direction of length and depth almost do not have remarkable effects. The results obtained by this study indicate that distribution of conductivity along the surface of a crack would be more important than the anisotropy in modeling SCCs in finite element simulations
Chortis, Dimitris I
2013-01-01
This book concerns the development of novel finite elements for the structural analysis of composite beams and blades. The introduction of material damping is also an important aspect of composite structures and it is presented here in terms of their static and dynamic behavior. The book thoroughly presents a new shear beam finite element, which entails new blade section mechanics, capable of predicting structural blade coupling due to composite coupling and/or internal section geometry. Theoretical background is further expanded towards the inclusion of nonlinear structural blade models and damping mechanics for composite structures. The models effectively include geometrically nonlinear terms due to large displacements and rotations, improve the modeling accuracy of very large flexible blades, and enable the modeling of rotational stiffening and buckling, as well as, nonlinear structural coupling. Validation simulations on specimen level study the geometric nonlinearities effect on the modal frequencies and...
DEFF Research Database (Denmark)
Cai, Hongzhu; Hu, Xiangyun; Xiong, Bin
2017-01-01
method which is unconditionally stable. We solve the diffusion equation for the electric field with a total field formulation. The finite element system of equation is solved using the direct method. The solutions of electric field, at different time, can be obtained using the effective time stepping...... method with trivial computation cost once the matrix is factorized. We try to keep the same time step size for a fixed number of steps using an adaptive time step doubling (ATSD) method. The finite element modeling domain is also truncated using a semi-adaptive method. We proposed a new boundary...... condition based on approximating the total field on the modeling boundary using the primary field corresponding to a layered background model. We validate our algorithm using several synthetic model studies....
Zhou, Xunfei; Hsieh, Sheng-Jen
2017-05-01
After years of development, Fused Deposition Modeling (FDM) has become the most popular technique in commercial 3D printing due to its cost effectiveness and easy-to-operate fabrication process. Mechanical strength and dimensional accuracy are two of the most important factors for reliability of FDM products. However, the solid-liquid-solid state changes of material in the FDM process make it difficult to monitor and model. In this paper, an experimental model was developed to apply cost-effective infrared thermography imaging method to acquire temperature history of filaments at the interface and their corresponding cooling mechanism. A three-dimensional finite element model was constructed to simulate the same process using element "birth and death" feature and validated with the thermal response from the experimental model. In 6 of 9 experimental conditions, a maximum of 13% difference existed between the experimental and numerical models. This work suggests that numerical modeling of FDM process is reliable and can facilitate better understanding of bead spreading and road-to-road bonding mechanics during fabrication.
Mohammadi, Hadi; Bahramian, Fereshteh; Wan, Wankei
2009-11-01
Modeling soft tissue using the finite element method is one of the most challenging areas in the field of biomechanical engineering. To date, many models have been developed to describe heart valve leaflet tissue mechanics, which are accurate to some extent. Nevertheless, there is no comprehensive method to modeling soft tissue mechanics, This is because (1) the degree of anisotropy in the heart valve leaflet changes layer by layer due to a variety of collagen fiber densities and orientations that cannot be taken into account in the model and also (2) a constitutive material model fully describing the mechanical properties of the leaflet structure is not available in the literature. In this framework, we develop a new high-order element using p-type finite element formulation to create anisotropic material properties similar to those of the heart valve leaflet tissue in only one single element. This element also takes the nonlinearity of the leaflet tissue into consideration using a bilinear material model. This new element is composed a two-dimensional finite element in the principal directions of leaflet tissue and a p-type finite element in the direction of thickness. The proposed element is easy to implement, much more efficient than standard elements available in commercial finite element packages. This study is one step towards the modeling of soft tissue mechanics using a meshless finite element approach to be applied in real-time haptic feedback of soft-tissue models in virtual reality simulation.
Development of a CAD Model Simplification Framework for Finite Element Analysis
2012-01-01
homotopy preserving medial axis transform by Sud et al. [38], and an extension on the common MAT method known as Θ-MAT for poly- hedral mesh models by...enhancement, ergonomic aspect, or part attach- ment method ; can facilitate the classification of the part’s criticality for analysis . The PART NAME and...ABSTRACT Title of thesis: DEVELOPMENT OF A CAD MODEL SIMPLIFICATION FRAMEWORK FOR FINITE ELEMENT ANALYSIS Brian Henry Russ, Master of Science, 2012
3D finite element model of the chinchilla ear for characterizing middle ear functions
Wang, Xuelin; Gan, Rong Z.
2016-01-01
Chinchilla is a commonly used animal model for research of sound transmission through the ear. Experimental measurements of the middle ear transfer function in chinchillas have shown that the middle ear cavity greatly affects the tympanic membrane (TM) and stapes footplate (FP) displacements. However, there is no finite element (FE) model of the chinchilla ear available in the literature to characterize the middle ear functions with the anatomical features of the chinchilla ear. This paper re...
Modal testing and finite element model updating of laser spot welds
Energy Technology Data Exchange (ETDEWEB)
Husain, N Abu; Khodaparast, H Haddad; Snaylam, A; James, S; Sharp, M; Dearden, G; Ouyang, H, E-mail: h.ouyang@liverpool.ac.u [Department of Engineering, Harrison Hughes Building, University of Liverpool, L69 3GH (United Kingdom)
2009-08-01
Spot welds are used extensively in automotive engineering. One of the latest manufacturing techniques for producing spot welds is Laser Welding. Finite element (FE) modelling of laser welds for dynamic analysis is a research issue because of the complexity and uncertainty of the welds and thus formed structures. In this work, FE model of the welds is developed by employing CWELD element in NASTRAN and its feasibility for representing laser spot welds is investigated. The FE model is updated based on the measured modal data of hat-plate structures and cast as a structural minimisation problem by the application of NASTRAN codes.
Kim, H. Alicia; Hardie, Robert; Yamakov, Vesselin; Park, Cheol
2015-01-01
This paper is the second part of a two-part series where the first part presents a molecular dynamics model of a single Boron Nitride Nanotube (BNNT) and this paper scales up to multiple BNNTs in a polymer matrix. This paper presents finite element (FE) models to investigate the effective elastic and piezoelectric properties of (BNNT) nanocomposites. The nanocomposites studied in this paper are thin films of polymer matrix with aligned co-planar BNNTs. The FE modelling approach provides a computationally efficient way to gain an understanding of the material properties. We examine several FE models to identify the most suitable models and investigate the effective properties with respect to the BNNT volume fraction and the number of nanotube walls. The FE models are constructed to represent aligned and randomly distributed BNNTs in a matrix of resin using 2D and 3D hollow and 3D filled cylinders. The homogenisation approach is employed to determine the overall elastic and piezoelectric constants for a range of volume fractions. These models are compared with an analytical model based on Mori-Tanaka formulation suitable for finite length cylindrical inclusions. The model applies to primarily single-wall BNNTs but is also extended to multi-wall BNNTs, for which preliminary results will be presented. Results from the Part 1 of this series can help to establish a constitutive relationship for input into the finite element model to enable the modeling of multiple BNNTs in a polymer matrix.
Turnbull, Heather; Omenzetter, Piotr
2017-04-01
The recent shift towards development of clean, sustainable energy sources has provided a new challenge in terms of structural safety and reliability: with aging, manufacturing defects, harsh environmental and operational conditions, and extreme events such as lightning strikes wind turbines can become damaged resulting in production losses and environmental degradation. To monitor the current structural state of the turbine, structural health monitoring (SHM) techniques would be beneficial. Physics based SHM in the form of calibration of a finite element model (FEMs) by inverse techniques is adopted in this research. Fuzzy finite element model updating (FFEMU) techniques for damage severity assessment of a small-scale wind turbine blade are discussed and implemented. The main advantage is the ability of FFEMU to account in a simple way for uncertainty within the problem of model updating. Uncertainty quantification techniques, such as fuzzy sets, enable a convenient mathematical representation of the various uncertainties. Experimental frequencies obtained from modal analysis on a small-scale wind turbine blade were described by fuzzy numbers to model measurement uncertainty. During this investigation, damage severity estimation was investigated through addition of small masses of varying magnitude to the trailing edge of the structure. This structural modification, intended to be in lieu of damage, enabled non-destructive experimental simulation of structural change. A numerical model was constructed with multiple variable additional masses simulated upon the blades trailing edge and used as updating parameters. Objective functions for updating were constructed and minimized using both particle swarm optimization algorithm and firefly algorithm. FFEMU was able to obtain a prediction of baseline material properties of the blade whilst also successfully predicting, with sufficient accuracy, a larger magnitude of structural alteration and its location.
Design, analysis and verification of a knee joint oncological prosthesis finite element model.
Zach, Lukáš; Kunčická, Lenka; Růžička, Pavel; Kocich, Radim
2014-11-01
The aim of this paper was to design a finite element model for a hinged PROSPON oncological knee endoprosthesis and to verify the model by comparison with ankle flexion angle using knee-bending experimental data obtained previously. Visible Human Project CT scans were used to create a general lower extremity bones model and to compose a 3D CAD knee joint model to which muscles and ligaments were added. Into the assembly the designed finite element PROSPON prosthesis model was integrated and an analysis focused on the PEEK-OPTIMA hinge pin bushing stress state was carried out. To confirm the stress state analysis results, contact pressure was investigated. The analysis was performed in the knee-bending position within 15.4-69.4° hip joint flexion range. The results showed that the maximum stress achieved during the analysis (46.6 MPa) did not exceed the yield strength of the material (90 MPa); the condition of plastic stability was therefore met. The stress state analysis results were confirmed by the distribution of contact pressure during knee-bending. The applicability of our designed finite element model for the real implant behaviour prediction was proven on the basis of good correlation of the analytical and experimental ankle flexion angle data. Copyright © 2014 Elsevier Ltd. All rights reserved.
An inverse problem approach for structural damage detection - Finite element model refinement
Zimmerman, D. C.; Kaouk, M.
1992-01-01
In this work, a methodology for incorporating measured modal data into an existing refined finite element model is examined with the objective of detecting and locating structural damage. This same algorithm is also useful in terms of finite element model refinement. The algorithm is based on the partial inverse problem, in that only partial spectral information is required. The technique utilizes a symmetric eigenstructure assignment algorithm to perform the partial spectral assignment. Algorithms to enhance mode shape assignability and to preserve sparsity in the updated model are developed. The sparsity preservation is of particular importance when considering damage detection in truss-like structures. Several examples are presented which highlight the key points made within the paper.
Studying the Vocal Fold Vibration Using a Nonlinear Finite-Element Model
Tao, Chao; Jiang, Jack. J.; Zhang, Yu
2006-05-01
The vocal fold vibration and voice production are highly complex nonlinear processes. Nonlinear relationship of glottal pressure to airflow and the nonlinearities of vocal fold collision are two important nonlinear factors of vocal fold vibration. In this paper, we will study the vocal fold vibration using a nonlinear finite-element model. In this model, the nonlinear relationship of glottal pressure to airflow, the nonlinearities of vocal fold collision, and the interaction between the airflow and vocal folds are taken into account. The impact pressure, vocal fold vibration, and glottal pressure under various lung pressures are studies. The results show that the nonlinear finite-element model is a useful tool for studying the voice production and predicting mechanical trauma leading to injurious abuse, misuse of the voice and vocal nodule.
Mangado, Nerea; Piella, Gemma; Noailly, Jérôme; Pons-Prats, Jordi; Ballester, Miguel Ángel González
2016-01-01
Computational modeling has become a powerful tool in biomedical engineering thanks to its potential to simulate coupled systems. However, real parameters are usually not accurately known, and variability is inherent in living organisms. To cope with this, probabilistic tools, statistical analysis and stochastic approaches have been used. This article aims to review the analysis of uncertainty and variability in the context of finite element modeling in biomedical engineering. Characterization techniques and propagation methods are presented, as well as examples of their applications in biomedical finite element simulations. Uncertainty propagation methods, both non-intrusive and intrusive, are described. Finally, pros and cons of the different approaches and their use in the scientific community are presented. This leads us to identify future directions for research and methodological development of uncertainty modeling in biomedical engineering.
Marwala, Tshilidzi
2010-01-01
Finite element models (FEMs) are widely used to understand the dynamic behaviour of various systems. FEM updating allows FEMs to be tuned better to reflect measured data and may be conducted using two different statistical frameworks: the maximum likelihood approach and Bayesian approaches. Finite Element Model Updating Using Computational Intelligence Techniques applies both strategies to the field of structural mechanics, an area vital for aerospace, civil and mechanical engineering. Vibration data is used for the updating process. Following an introduction a number of computational intelligence techniques to facilitate the updating process are proposed; they include: • multi-layer perceptron neural networks for real-time FEM updating; • particle swarm and genetic-algorithm-based optimization methods to accommodate the demands of global versus local optimization models; • simulated annealing to put the methodologies into a sound statistical basis; and • response surface methods and expectation m...
Finite element fluid modeling of axisymmetric magnetized boundary plasma with recycling neutrals
International Nuclear Information System (INIS)
Zanino, R.
1992-01-01
Finite elements should provide a natural and flexible method for fluid modeling of the tokamak SOL, in particular when the SOL geometry is complex, and/or the poloidal magnetic field is very inclined to the limiter/divertor target. Here we present a Galerkin finite element code, FELS, for transport modeling of a 2-fluid magnetized boundary plasma in an axisymmetry domain, in the presence of recycling neutrals. The classical collisional plasma dynamics along magnetic field lines is taken into account, and a simple diffusive Ansatz is used for the fluxes across magnetic surfaces; electric currents and diamagnetic flows are neglected for the time being. An analytical fluid model is used for the recycling neutrals. Results are shown and discussed for the case of a simple geometry. (orig.)
Modeling the mechanics of axonal fiber tracts using the embedded finite element method.
Garimella, Harsha T; Kraft, Reuben H
2017-05-01
A subject-specific human head finite element model with embedded axonal fiber tractography obtained from diffusion tensor imaging was developed. The axonal fiber tractography finite element model was coupled with the volumetric elements in the head model using the embedded element method. This technique enables the calculation of axonal strains and real-time tracking of the mechanical response of the axonal fiber tracts. The coupled model was then verified using pressure and relative displacement-based (between skull and brain) experimental studies and was employed to analyze a head impact, demonstrating the applicability of this method in studying axonal injury. Following this, a comparison study of different injury criteria was performed. This model was used to determine the influence of impact direction on the extent of the axonal injury. The results suggested that the lateral impact loading is more dangerous compared to loading in the sagittal plane, a finding in agreement with previous studies. Through this analysis, we demonstrated the viability of the embedded element method as an alternative numerical approach for studying axonal injury in patient-specific human head models. Copyright © 2016 John Wiley & Sons, Ltd.
DEFF Research Database (Denmark)
Kiel, Nikolaj; Andersen, Lars Vabbersgaard; Niu, Bin
2012-01-01
, with as many applications as possible, for the least possible computational cost. The coupling method of the structural panels in the above mentioned modular finite element model is in this paper discussed and evaluated. The coupling of the panels are performed using the commercial finite element program...... ABAQUS [2], where the built-in element constraints applications are utilised. The models are setup in scripts, using the Python language, to ensure a fast and consistent model. It is found that the modules, i.e. panels, are easy to couple, if an auxiliary skeleton is introduced in all panel intersections...
Accuracy of finite-element models for the stress analysis of multiple-holed moderator blocks
International Nuclear Information System (INIS)
Smith, P.D.; Sullivan, R.M.; Lewis, A.C.; Yu, H.J.
1981-01-01
Two steps have been taken to quantify and improve the accuracy in the analysis. First, the limitations of various approximation techniques have been studied with the aid of smaller benchmark problems containing fewer holes. Second, a new family of computer programs has been developed for handling such large problems. This paper describes the accuracy studies and the benchmark problems. A review is given of some proposed modeling techniques including local mesh refinement, homogenization, a special-purpose finite element, and substructuring. Some limitations of these approaches are discussed. The new finite element programs and the features that contribute to their efficiency are discussed. These include a standard architecture for out-of-core data processing and an equation solver that operates on a peripheral array processor. The central conclusions of the paper are: (1) modeling approximation methods such as local mesh refinement and homogenization tend to be unreliable, and they should be justified by a fine mesh benchmark analysis; and (2) finite element codes are now available that can achieve accurate solutions at a reasonable cost, and there is no longer a need to employ modeling approximations in the two-dimensional analysis of HTGR fuel elements. 10 figures
Energy Technology Data Exchange (ETDEWEB)
Panescu, D. (EP Technologies, Inc., Sunnyvale, CA (United States)); Webster, J.G.; Tompkins, W.J. (Univ. of Wisconsin, Madison, WI (United States)); Stratbucker, R.A. (Radiation Health Center of the State of Nebraska, Omaha, NE (United States))
1995-02-01
The goal of this study was to determine the optimal electrode placement and size to minimize myocardial damage during defibrillation while rendering refractory a critical mass of cardiac tissue of 100%. For this purpose, we developed a 3-D finite element model with 55 388 nodes, 50 913 hexahedral elements, and simulated 16 different organs and tissues, as well as the properties of the electrolyte. The model used a nonuniform mesh with an average spatial resolution of 0.8 cm in all three dimensions. To validate this model, we measured the voltage across 3-cm[sup 2] Ag-AgCl electrodes when currents of 5 mA at 50 kHz were injected into a human subject's thorax through the same electrodes. For the same electrode placements and sizes and the same injected current, the finite element analysis produced results in good agreement with the experimental data. For the optimization of defibrillation, we tested 12 different electrode placements and seven different electrode sizes. The finite element analyses showed that the anterior-posterior electrode placement and an electrode size of about 90 cm[sup 2] offered the least chance of potential myocardial damage and required a shock energy of less than 350 J for 5-ms defibrillation pulses to achieve 100% critical mass. 47 refs., 8 figs., 4 tabs.
A finite element model updating technique for adjustment of parameters near boundaries
Gwinn, Allen Fort, Jr.
Even though there have been many advances in research related to methods of updating finite element models based on measured normal mode vibration characteristics, there is yet to be a widely accepted method that works reliably with a wide range of problems. This dissertation focuses on the specific class of problems having to do with changes in stiffness near the clamped boundary of plate structures. This class of problems is especially important as it relates to the performance of turbine engine blades, where a change in stiffness at the base of the blade can be indicative of structural damage. The method that is presented herein is a new technique for resolving the differences between the physical structure and the finite element model. It is a semi-iterative technique that incorporates a "physical expansion" of the measured eigenvectors along with appropriate scaling of these expanded eigenvectors into an iterative loop that uses the Engel's model modification method to then calculate adjusted stiffness parameters for the finite element model. Three example problems are presented that use eigenvalues and mass normalized eigenvectors that have been calculated from experimentally obtained accelerometer readings. The test articles that were used were all thin plates with one edge fully clamped. They each had a cantilevered length of 8.5 inches and a width of 4 inches. The three plates differed from one another in thickness from 0.100 inches to 0.188 inches. These dimensions were selected in order to approximate a gas turbine engine blade. The semi-iterative modification technique is shown to do an excellent job of calculating the necessary adjustments to the finite element model so that the analytically determined eigenvalues and eigenvectors for the adjusted model match the corresponding values from the experimental data with good agreement. Furthermore, the semi-iterative method is quite robust. For the examples presented here, the method consistently converged
Liu, Ying; Xu, Zhenhuan; Li, Yuguo
2018-04-01
We present a goal-oriented adaptive finite element (FE) modelling algorithm for 3-D magnetotelluric fields in generally anisotropic conductivity media. The model consists of a background layered structure, containing anisotropic blocks. Each block and layer might be anisotropic by assigning to them 3 × 3 conductivity tensors. The second-order partial differential equations are solved using the adaptive finite element method (FEM). The computational domain is subdivided into unstructured tetrahedral elements, which allow for complex geometries including bathymetry and dipping interfaces. The grid refinement process is guided by a global posteriori error estimator and is performed iteratively. The system of linear FE equations for electric field E is solved with a direct solver MUMPS. Then the magnetic field H can be found, in which the required derivatives are computed numerically using cubic spline interpolation. The 3-D FE algorithm has been validated by comparisons with both the 3-D finite-difference solution and 2-D FE results. Two model types are used to demonstrate the effects of anisotropy upon 3-D magnetotelluric responses: horizontal and dipping anisotropy. Finally, a 3D sea hill model is modelled to study the effect of oblique interfaces and the dipping anisotropy.
Modeling 3D PCMI using the Extended Finite Element Method with higher order elements
Energy Technology Data Exchange (ETDEWEB)
Jiang, W. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Spencer, Benjamin W. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2017-03-31
This report documents the recent development to enable XFEM to work with higher order elements. It also demonstrates the application of higher order (quadratic) elements to both 2D and 3D models of PCMI problems, where discrete fractures in the fuel are represented using XFEM. The modeling results demonstrate the ability of the higher order XFEM to accurately capture the effects of a crack on the response in the vicinity of the intersecting surfaces of cracked fuel and cladding, as well as represent smooth responses in the regions away from the crack.
International Nuclear Information System (INIS)
Wang Zhengzhi; Xu Yun; Gu Ping
2012-01-01
A polypropylene nanofibrillar array was successfully fabricated by template-assisted nanofabrication strategy. Adhesion properties of this gecko-inspired structure were studied through two parallel and independent approaches: experiments and finite element simulations. Experimental results show relatively good normal adhesion, but accompanied by high preloads. The interfacial adhesion was modelled by effective spring elements with piecewise-linear constitution. The effective elasticity of the fibre-array system was originally calculated from our measured elasticity of single nanowire. Comparisons of the experimental and simulative results reveal quantitative agreement except for some explainable deviations, which suggests the potential applicability of the present models and applied theories. (fast track communication)
Finite element modeling of heating phenomena of cracks excited by high-intensity ultrasonic pulses
International Nuclear Information System (INIS)
Chen Zhao-Jiang; Zheng Jiang; Zhang Shu-Yi; Mi Xiao-Bing; Zheng Kai
2010-01-01
A three-dimensional thermo-mechanical coupled finite element model is built up to simulate the phenomena of dynamical contact and frictional heating of crack faces when the plate containing the crack is excited by high-intensity ultrasonic pulses. In the finite element model, the high-power ultrasonic transducer is modeled by using a piezoelectric thermal-analogy method, and the dynamical interaction between both crack faces is modeled using a contact-impact theory. In the simulations, the frictional heating taking place at the crack faces is quantitatively calculated by using finite element thermal-structural coupling analysis, especially, the influences of acoustic chaos to plate vibration and crack heating are calculated and analysed in detail. Meanwhile, the related ultrasonic infrared images are also obtained experimentally, and the theoretical simulation results are in agreement with that of the experiments. The results show that, by using the theoretical method, a good simulation of dynamic interaction and friction heating process of the crack faces under non-chaotic or chaotic sound excitation can be obtained
Structural dynamic modeling for rotating blades using three dimensional finite elements
Energy Technology Data Exchange (ETDEWEB)
Kee, Young Jung; Shin, Sang Joon [Seoul National University, Seoul (Korea, Republic of)
2015-04-15
A precise analysis model was developed in this paper to investigate the dynamic characteristics of rotating composite blades. An eighteen-node solid-shell finite element was used to model the blade structures. This study is focused on geometrically nonlinear problems, because the material is assumed linear elastic. Incremental total Lagrangian approach was adopted to allow estimations on arbitrarily large rotations and displacements. The equations of motion for the finite element model were derived by using Hamilton's principle, and the resulting nonlinear equilibrium equations were solved by applying Newton-Raphson method combined with load control. A modified stress-strain relation was adopted to avoid the transverse shear locking problem, and fairly reliable results were obtained with no sign of locking phenomenon. The obtained numerical results were compared to several benchmark problems, and the results show a good correlation with the experimental data and other finite element analysis results. The vibration characteristics of shell- and beam-type blades were investigated. For shell-type blades, the dynamic characteristics may be significantly influenced by blade curvature, pre-twist, and geometric nonlinearity. For beam-type blades, one-dimensional beam and three-dimensional solid models offer comparable predictions for the straight and large aspect ratio blade. As blade aspect ratio decreases, considerable differences appear in the bending and torsion modes. The tip sweep angle tends to decrease the flap bending frequencies, but the torsion frequency increases with the tip sweep angle.
Structural dynamic modeling for rotating blades using three dimensional finite elements
International Nuclear Information System (INIS)
Kee, Young Jung; Shin, Sang Joon
2015-01-01
A precise analysis model was developed in this paper to investigate the dynamic characteristics of rotating composite blades. An eighteen-node solid-shell finite element was used to model the blade structures. This study is focused on geometrically nonlinear problems, because the material is assumed linear elastic. Incremental total Lagrangian approach was adopted to allow estimations on arbitrarily large rotations and displacements. The equations of motion for the finite element model were derived by using Hamilton's principle, and the resulting nonlinear equilibrium equations were solved by applying Newton-Raphson method combined with load control. A modified stress-strain relation was adopted to avoid the transverse shear locking problem, and fairly reliable results were obtained with no sign of locking phenomenon. The obtained numerical results were compared to several benchmark problems, and the results show a good correlation with the experimental data and other finite element analysis results. The vibration characteristics of shell- and beam-type blades were investigated. For shell-type blades, the dynamic characteristics may be significantly influenced by blade curvature, pre-twist, and geometric nonlinearity. For beam-type blades, one-dimensional beam and three-dimensional solid models offer comparable predictions for the straight and large aspect ratio blade. As blade aspect ratio decreases, considerable differences appear in the bending and torsion modes. The tip sweep angle tends to decrease the flap bending frequencies, but the torsion frequency increases with the tip sweep angle.
DEFF Research Database (Denmark)
Cai, Hongzhu; Čuma, Martin; Zhdanov, Michael
2015-01-01
This paper presents a parallelized version of the edge-based finite element method with a novel post-processing approach for numerical modeling of an electromagnetic field in complex media. The method uses an unstructured tetrahedral mesh which can reduce the number of degrees of freedom signific......This paper presents a parallelized version of the edge-based finite element method with a novel post-processing approach for numerical modeling of an electromagnetic field in complex media. The method uses an unstructured tetrahedral mesh which can reduce the number of degrees of freedom...... significantly. The linear system of finite element equations is solved using parallel direct solvers which are robust for ill-conditioned systems and efficient for multiple source electromagnetic (EM) modeling. We also introduce a novel approach to compute the scalar components of the electric field from...... the tangential components along each edge based on field redatuming. The method can produce a more accurate result as compared to conventional approach. We have applied the developed algorithm to compute the EM response for a typical 3D anisotropic geoelectrical model of the off-shore HC reservoir with complex...
Zhang, Chao; Binienda, Wieslaw K.; Morscher, Gregory; Martin, Richard E.
2012-01-01
The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composite
Gao, Yang; Ge, Zhishang; Zhai, Weihao; Tan, Shiwang; Zhang, Feng
2018-01-01
The static and dynamic characteristics of fuel tank are studied for the armoured vehicle in this paper. The CATIA software is applied to build the CAD model of the armoured vehicles’ fuel tank, and the finite element model is established in ANSYS Workbench. The finite element method is carried out to analyze the static and dynamic mechanical properties of the fuel tank, and the first six orders of mode shapes and their frequencies are also computed and given in the paper, then the stress distribution diagram and the high stress areas are obtained. The results of the research provide some references to the fuel tanks’ design improvement, and give some guidance for the installation of the fuel tanks on armoured vehicles, and help to improve the properties and the service life of this kind of armoured vehicles’ fuel tanks.
Directory of Open Access Journals (Sweden)
Suvanjumrat Chakrit
2017-01-01
Full Text Available Finite element model of tire rolling resistance test on the drum was developed using 3D steady state rolling analysis coupling with pre-inflation of 2D axisymmetric tire analysis. The complex components of the radial tires composing tread, sidewall, ply layers, steel belts, and lead wires were modeled using rebar elements which were embed into the rubber element using the tying equation. The Mooney-Rivlin hyperelastic constitutive model was employed to describe the large deformation behavior of tread and sidewall, while other components such as plies, steel belts and bead wires were assigned the linear isotropic material. The tire rolling resistance system was modeled by inflation of slick tire and compression on the drum for the footprint analysis regarding the rolling resistance test. The tire’s steady state characteristics such as footprint contact pressure, rolling resistance force, and time response characteristic of tires were predicted instead the experiment of the prototype.
Finite Element Model of Training in the superconducting quadrupole magnet SQ02
Energy Technology Data Exchange (ETDEWEB)
Caspi, Shlomo; Ferracin, Paolo
2007-11-01
This paper describes the use of 3D finite element models to study training in superconducting magnets. The simulations are used to examine coil displacements when the electromagnetic forces are cycled, and compute the frictional energy released during conductor motion with the resulting temperature rise. A computed training curve is then presented and discussed. The results from the numerical computations are compared with test results of the Nb{sub 3}Sn racetrack quadrupole magnet SQ02.
Quasi-static indentation modelling of aluminium specimen using finite element analysis
Mayank Nirbhay; Mahima Dua; Anurag Dixit; Satpal Sharma; R.K. Misra
2017-01-01
The influence of different types of rigid hemispherical and conical indenters on a rectangular specimen of aluminium has been investigated, in the small indenter test. A 3-D finite-element FE model was used to carry out the computation of the elastic-plastic solution of different rigid hemispherical and conical indenters. Three hemispherical-headed and four conical-headed indenters were designed and developed for testing. FE software ABAQUS® has been used to determine the load vs. indenter-di...
Evaluation of Solid Modeling Software for Finite Element Analysis of Woven Ceramic Matrix Composites
Nemeth, Noel N.; Mital, Subodh; Lang, Jerry
2010-01-01
Three computer programs, used for the purpose of generating 3-D finite element models of the Repeating Unit Cell (RUC) of a textile, were examined for suitability to model woven Ceramic Matrix Composites (CMCs). The programs evaluated were the open-source available TexGen, the commercially available WiseTex, and the proprietary Composite Material Evaluator (COMATE). A five-harness-satin (5HS) weave for a melt-infiltrated (MI) silicon carbide matrix and silicon carbide fiber was selected as an example problem and the programs were tested for their ability to generate a finite element model of the RUC. The programs were also evaluated for ease-of-use and capability, particularly for the capability to introduce various defect types such as porosity, ply shifting, and nesting of a laminate. Overall, it was found that TexGen and WiseTex were useful for generating solid models of the tow geometry; however, there was a lack of consistency in generating well-conditioned finite element meshes of the tows and matrix. TexGen and WiseTex were both capable of allowing collective and individual shifting of tows within a ply and WiseTex also had a ply nesting capability. TexGen and WiseTex were sufficiently userfriendly and both included a Graphical User Interface (GUI). COMATE was satisfactory in generating a 5HS finite element mesh of an idealized weave geometry but COMATE lacked a GUI and was limited to only 5HS and 8HS weaves compared to the larger amount of weave selections available with TexGen and WiseTex.
Applying control volume finite element for modelling direct injection boom spraying flow
El Aissaoui, Abdellah; Lebeau, Frédéric; Destain, Marie-France; Houmy, Karim
2009-01-01
Assessment of injection lag transport and uniformity of direct injection boom sprayer is an important issue for successful variable rate spraying technology. To estimate the boom lag transport and pressure loss, a numerical model is formulated on the basis of fluid hydrodynamic conservation equations. The software is implemented in visual basic. To solve the pressure – velocities equations, control volume finite element method (CV) is used to delimit elementary volumes of the boom. Linearizat...
Directory of Open Access Journals (Sweden)
Zhouhong Zong
2015-08-01
Full Text Available In the engineering practice, merging statistical analysis into structural evaluation and assessment is a tendency in the future. As a combination of mathematical and statistical techniques, response surface (RS methodology has been successfully applied to design optimization, response prediction and model validation. With the aid of RS methodology, these two serial papers present a finite element (FE model updating and validation method for bridge structures based on structural health monitoring. The key issues to implement such a model updating are discussed in this paper, such as design of experiment, parameter screening, construction of high-order polynomial response surface model, optimization methods and precision inspection of RS model. The proposed procedure is illustrated by a prestressed concrete continuous rigid-frame bridge monitored under operational conditions. The results from the updated FE model have been compared with those obtained from online health monitoring system. The real application to a full-size bridge has demonstrated that the FE model updating process is efficient and convenient. The updated FE model can relatively reflect the actual condition of Xiabaishi Bridge in the design space of parameters and can be further applied to FE model validation and damage identification.
International Nuclear Information System (INIS)
Hawileh, Rami A.; El-Maaddawy, Tamer A.; Naser, Mohannad Z.
2012-01-01
Highlights: ► A 3D nonlinear FE model is developed of RC deep beams with web openings. ► We used cohesion elements to simulate bond. ► The developed FE model is suitable for analysis of such complex structures. -- Abstract: This paper aims to develop 3D nonlinear finite element (FE) models for reinforced concrete (RC) deep beams containing web openings and strengthened in shear with carbon fiber reinforced polymer (CFRP) composite sheets. The web openings interrupted the natural load path either fully or partially. The FE models adopted realistic materials constitutive laws that account for the nonlinear behavior of materials. In the FE models, solid elements for concrete, multi-layer shell elements for CFRP and link elements for steel reinforcement were used to simulate the physical models. Special interface elements were implemented in the FE models to simulate the interfacial bond behavior between the concrete and CFRP composites. A comparison between the FE results and experimental data published in the literature demonstrated the validity of the computational models in capturing the structural response for both unstrengthened and CFRP-strengthened deep beams with openings. The developed FE models can serve as a numerical platform for performance prediction of RC deep beams with openings strengthened in shear with CFRP composites.
Duprey, Sonia; Bruyere, Karine; Verriest, Jean-Pierre
2010-01-01
Human body numerical models can help to develop protection devices against effects of road crashes. In the context of a side impact, a shoulder model able to predict shoulder injuries and more especially clavicle fracture would be helpful. A shoulder model derived from an existing finite element model of the human body representing an average male (50th percentile), HUMOS1, has been upgraded. An isolated clavicle model was assessed thanks to experimental corridors derived from dynamic tests up to failure. Then, the whole upgraded shoulder model was evaluated by comparison with results from experimental side impact tests on the shoulder. Eventually, the upgraded model was geometrically personalized toward the anthropometry of the subjects and its ability to simulate fractures was assessed. The isolated clavicle model was assessed as validated. The upgraded 50th percentile shoulder model provided accurate results in the subinjurious domain. At higher velocities, the personalized models produced realistic shoulder injuries: clavicle fracture was accurately predicted in four cases of six, the model was conservative for the two other cases. The upgraded shoulder model presented here was successfully submitted to a rigorous assessment process. Once geometrically personalized, it provided positive results for clavicle fracture prediction. As clavicle fracture is the major shoulder injury, this model could help the design of safety devices for shoulder protection. Furthermore, this study enhances the need for geometrical personalization methods when using finite element model for injury risk prediction.
Operational model updating of spinning finite element models for HAWT blades
Velazquez, Antonio; Swartz, R. Andrew; Loh, Kenneth J.; Zhao, Yingjun; La Saponara, Valeria; Kamisky, Robert J.; van Dam, Cornelis P.
2014-04-01
Structural health monitoring (SHM) relies on collection and interrogation of operational data from the monitored structure. To make this data meaningful, a means of understanding how damage sensitive data features relate to the physical condition of the structure is required. Model-driven SHM applications achieve this goal through model updating. This study proposed a novel approach for updating of aero-elastic turbine blade vibrational models for operational horizontal-axis wind turbines (HAWTs). The proposed approach updates estimates of modal properties for spinning HAWT blades intended for use in SHM and load estimation of these structures. Spinning structures present additional challenges for model updating due to spinning effects, dependence of modal properties on rotational velocity, and gyroscopic effects that lead to complex mode shapes. A cyclo-stationary stochastic-based eigensystem realization algorithm (ERA) is applied to operational turbine data to identify data-driven modal properties including frequencies and mode shapes. Model-driven modal properties are derived through modal condensation of spinning finite element models with variable physical parameters. Complex modes are converted into equivalent real modes through reduction transformation. Model updating is achieved through use of an adaptive simulated annealing search process, via Modal Assurance Criterion (MAC) with complex-conjugate modes, to find the physical parameters that best match the experimentally derived data.
The finite element method in making up meshes in ANSYS Meshing for CFD models
Directory of Open Access Journals (Sweden)
Віктор Іванович Троханяк
2015-11-01
Full Text Available Method of finite elements (FEM is used in calculating tasks of hydrodynamics and heat transfer tasks. The essence of the method consists in the approximate solution of a variational task. To formulate this task a functional concept is used. The type of a functional is different for different tasks and is selected through a special choice. Currently FEM is widely used in calculating the strength and in solving tasks of heat transfer in solids. However, it can be applied in calculating the flow of liquids and gases. There are also methods that combine elements of the finite volumes and finite elements methods. The combination of these methods make it possible to use a wide range of computational meshes ( tetragonal meshes, pyramidal meshes, prismatic meshes, polyhedral meshes what is necessary for solving tasks with complex geometry. This approach is used by CFD packages Ansys CFX, Ansys Fluent, Star-CD, Star-CCM +, Comsol and others. The method and the analysis of 2D mesh were carried out, using a method of final elements in ANSYS Meshing for heat exchangers with an inline arrangement of tubes in banks and with their curvilinear arrangement in compact banks of tubes of a new design. Particular features were considered and the algorithm of making up a mesh was developed for tasks of hydraulic and gas dynamics and thermal mass transfer. The most optimum and qualitative meshes for CFD models were chosen
Modeling fragmentation with new high order finite element technology and node splitting
Olovsson, Lars; Limido, Jérôme; Lacome, Jean-Luc; Grønsund Hanssen, Arve; Petit, Jacques
2015-09-01
The modeling of fragmentation has historically been linked to the weapons industry where the main goal is to optimize a bomb or to design effective blast shields. Numerical modeling of fragmentation from dynamic loading has traditionally been modeled by legacy finite element solvers that rely on element erosion to model material failure. However this method results in the removal of too much material. This is not realistic as retaining the mass of the structure is critical to modeling the event correctly. We propose a new approach implemented in the IMPETUS AFEA SOLVER® based on the following: New High Order Finite Elements that can easily deal with very large deformations; Stochastic distribution of initial damage that allows for a non homogeneous distribution of fragments; and a Node Splitting Algorithm that allows for material fracture without element erosion that is mesh independent. The approach is evaluated for various materials and scenarios: -Titanium ring electromagnetic compression; Hard steel Taylor bar impact, Fused silica Taylor bar impact, Steel cylinder explosion, The results obtained from the simulations are representative of the failure mechanisms observed experimentally. The main benefit of this approach is good energy conservation (no loss of mass) and numerical robustness even in complex situations.
Modeling fragmentation with new high order finite element technology and node splitting
Directory of Open Access Journals (Sweden)
Olovsson Lars
2015-01-01
Full Text Available The modeling of fragmentation has historically been linked to the weapons industry where the main goal is to optimize a bomb or to design effective blast shields. Numerical modeling of fragmentation from dynamic loading has traditionally been modeled by legacy finite element solvers that rely on element erosion to model material failure. However this method results in the removal of too much material. This is not realistic as retaining the mass of the structure is critical to modeling the event correctly. We propose a new approach implemented in the IMPETUS AFEA SOLVER® based on the following: New High Order Finite Elements that can easily deal with very large deformations; Stochastic distribution of initial damage that allows for a non homogeneous distribution of fragments; and a Node Splitting Algorithm that allows for material fracture without element erosion that is mesh independent. The approach is evaluated for various materials and scenarios: -Titanium ring electromagnetic compression; Hard steel Taylor bar impact, Fused silica Taylor bar impact, Steel cylinder explosion, The results obtained from the simulations are representative of the failure mechanisms observed experimentally. The main benefit of this approach is good energy conservation (no loss of mass and numerical robustness even in complex situations.
Leser, Patrick E.; Hochhalter, Jacob D.; Newman, John A.; Leser, William P.; Warner, James E.; Wawrzynek, Paul A.; Yuan, Fuh-Gwo
2015-01-01
Utilizing inverse uncertainty quantification techniques, structural health monitoring can be integrated with damage progression models to form probabilistic predictions of a structure's remaining useful life. However, damage evolution in realistic structures is physically complex. Accurately representing this behavior requires high-fidelity models which are typically computationally prohibitive. In the present work, a high-fidelity finite element model is represented by a surrogate model, reducing computation times. The new approach is used with damage diagnosis data to form a probabilistic prediction of remaining useful life for a test specimen under mixed-mode conditions.
Finite element modeling of surface subsidence induced by underground coal mining
International Nuclear Information System (INIS)
Su, D.W.H.
1992-01-01
The ability to predict the effects of longwall mining on topography and surface structures is important for any coal company in making permit applications and anticipating potential mining problems. The sophisticated finite element model described and evaluated in this paper is based upon five years of underground and surface observations and evolutionary development of modeling techniques and attributes. The model provides a very powerful tool to address subsidence and other ground control questions. The model can be used to calculate postmining stress and strain conditions at any horizon between the mine and the ground surface. This holds the promise of assisting in the prediction of mining-related hydrological effects
A blended continuous–discontinuous finite element method for solving the multi-fluid plasma model
Energy Technology Data Exchange (ETDEWEB)
Sousa, E.M., E-mail: sousae@uw.edu; Shumlak, U., E-mail: shumlak@uw.edu
2016-12-01
The multi-fluid plasma model represents electrons, multiple ion species, and multiple neutral species as separate fluids that interact through short-range collisions and long-range electromagnetic fields. The model spans a large range of temporal and spatial scales, which renders the model stiff and presents numerical challenges. To address the large range of timescales, a blended continuous and discontinuous Galerkin method is proposed, where the massive ion and neutral species are modeled using an explicit discontinuous Galerkin method while the electrons and electromagnetic fields are modeled using an implicit continuous Galerkin method. This approach is able to capture large-gradient ion and neutral physics like shock formation, while resolving high-frequency electron dynamics in a computationally efficient manner. The details of the Blended Finite Element Method (BFEM) are presented. The numerical method is benchmarked for accuracy and tested using two-fluid one-dimensional soliton problem and electromagnetic shock problem. The results are compared to conventional finite volume and finite element methods, and demonstrate that the BFEM is particularly effective in resolving physics in stiff problems involving realistic physical parameters, including realistic electron mass and speed of light. The benefit is illustrated by computing a three-fluid plasma application that demonstrates species separation in multi-component plasmas.
Thermoviscoelastic finite element modeling of laser-generated ultrasound in viscoelastic plates
International Nuclear Information System (INIS)
Sun Hongxiang; Zhang Shuyi
2010-01-01
Laser-generated ultrasound in a thin composite plate with thermoviscoelastic property has been studied quantitatively. According to thermoviscoelastic theory, considering the viscoelastic and thermophysical properties of materials, a numerical model for the laser-generated Lamb waves is established in the frequency domain by using a finite element method. It is confirmed that the temperature and displacement fields calculated in the frequency domain coincide well with those obtained in the time domain. In the numerical simulations of thermoviscoelastically generated Lamb waves, the effects of viscoelastic and elastic stiffness moduli, and the thickness of the materials have been taken into account in details. The characteristics of the Lamb waves in the numerical results agree well with the features of the disperse curves. The results show that the finite element method in this paper provides a useful technique to characterize mechanical properties of composite materials.
Ring tests on high density polyethylene: Full investigation assisted by finite element modeling
International Nuclear Information System (INIS)
Laiarinandrasana, L.; Devilliers, C.; Oberti, S.; Gaudichet, E.; Fayolle, B.; Lucatelli, J.M.
2011-01-01
In order to characterize the mechanical behavior of HDPE pipes, the ASTM D 2290-04 standard recommends carrying out tensile tests on notched rings, cut out from the pipe. This very simple test is also utilized to investigate the aging effect of the pipe by determining the strain at failure. Comparison between full ring and notched ring mechanical responses are discussed. Constitutive modeling including strain rate effects was performed by finite element analysis. This allowed a better understanding of the stress state in the cross section perpendicular to the loading direction. Additionally, the influence of a thin layer of oxidized HDPE in the inner wall of the ring was studied in the light of the finite element results.
Efendiev, Yalchin R.
2015-06-05
In this paper, we develop a multiscale finite element method for solving flows in fractured media. Our approach is based on generalized multiscale finite element method (GMsFEM), where we represent the fracture effects on a coarse grid via multiscale basis functions. These multiscale basis functions are constructed in the offline stage via local spectral problems following GMsFEM. To represent the fractures on the fine grid, we consider two approaches (1) discrete fracture model (DFM) (2) embedded fracture model (EFM) and their combination. In DFM, the fractures are resolved via the fine grid, while in EFM the fracture and the fine grid block interaction is represented as a source term. In the proposed multiscale method, additional multiscale basis functions are used to represent the long fractures, while short-size fractures are collectively represented by a single basis functions. The procedure is automatically done via local spectral problems. In this regard, our approach shares common concepts with several approaches proposed in the literature as we discuss. We would like to emphasize that our goal is not to compare DFM with EFM, but rather to develop GMsFEM framework which uses these (DFM or EFM) fine-grid discretization techniques. Numerical results are presented, where we demonstrate how one can adaptively add basis functions in the regions of interest based on error indicators. We also discuss the use of randomized snapshots (Calo et al. Randomized oversampling for generalized multiscale finite element methods, 2014), which reduces the offline computational cost.
A finite element modeling of a multifunctional hybrid composite beam with viscoelastic materials
Wang, Ya; Inman, Daniel J.
2013-04-01
The multifunctional hybrid composite structure studied here consists of a ceramic outer layer capable of withstanding high temperatures, a functionally graded ceramic layer combining shape memory alloy (SMA) properties of NiTi together with Ti2AlC (called Graded Ceramic/Metal Composite, or GCMeC), and a high temperature sensor patch, followed by a polymer matrix composite laced with vascular cooling channels all held together with various epoxies. Due to the recoverable nature of SMA and adhesive properties of Ti2AlC, the damping behavior of the GCMeC is largely viscoelastic. This paper presents a finite element formulation for this multifunctional hybrid structure with embedded viscoelastic material. In order to implement the viscoelastic model into the finite element formulation, a second order three parameter Golla-Hughes-McTavish (GHM) method is used to describe the viscoelastic behavior. Considering the parameter identification, a strategy to estimate the fractional order of the time derivative and the relaxation time is outlined. The curve-fitting aspects of both GHM and ADF show good agreement with experimental data obtained from dynamic mechanics analysis. The performance of the finite element of the layered multifunctional beam is verified through experimental model analysis.
Parallel goal-oriented adaptive finite element modeling for 3D electromagnetic exploration
Zhang, Y.; Key, K.; Ovall, J.; Holst, M.
2014-12-01
We present a parallel goal-oriented adaptive finite element method for accurate and efficient electromagnetic (EM) modeling of complex 3D structures. An unstructured tetrahedral mesh allows this approach to accommodate arbitrarily complex 3D conductivity variations and a priori known boundaries. The total electric field is approximated by the lowest order linear curl-conforming shape functions and the discretized finite element equations are solved by a sparse LU factorization. Accuracy of the finite element solution is achieved through adaptive mesh refinement that is performed iteratively until the solution converges to the desired accuracy tolerance. Refinement is guided by a goal-oriented error estimator that uses a dual-weighted residual method to optimize the mesh for accurate EM responses at the locations of the EM receivers. As a result, the mesh refinement is highly efficient since it only targets the elements where the inaccuracy of the solution corrupts the response at the possibly distant locations of the EM receivers. We compare the accuracy and efficiency of two approaches for estimating the primary residual error required at the core of this method: one uses local element and inter-element residuals and the other relies on solving a global residual system using a hierarchical basis. For computational efficiency our method follows the Bank-Holst algorithm for parallelization, where solutions are computed in subdomains of the original model. To resolve the load-balancing problem, this approach applies a spectral bisection method to divide the entire model into subdomains that have approximately equal error and the same number of receivers. The finite element solutions are then computed in parallel with each subdomain carrying out goal-oriented adaptive mesh refinement independently. We validate the newly developed algorithm by comparison with controlled-source EM solutions for 1D layered models and with 2D results from our earlier 2D goal oriented
Material assignment in finite element modeling: heterogeneous properties of the mandibular bone.
Xin, Pengfei; Nie, Pulin; Jiang, Bin; Deng, Simin; Hu, Guanghong; Shen, Steve G F
2013-03-01
The properties of the biomaterial are normally characterized by heterogeneity on all scales influencing the function and biomechanics. Elastic modulus (EM), which is one of the most important mechanical properties of material, is necessary for finite element modeling and needed to be determined by some methods. The aim of this study is to demonstrate the feasibility of assessment of EM from GrayValue (GV) of computed tomographic image and assignment of material properties in heterogeneous finite element modeling for studying the performance of the mandibular bones. Three mandibles obtained from fresh human cadavers were used in this study. All mandibular bones were scanned using computed tomography, and the original data were stored in optical disks. The finite element modeling of the 3 mandibles was meshed using Materialise Mimics 10.01 and Abaqus 6.10 software. Using the empirical expression on relationship between GV and EM, the empirical EM of the meshed mandibular elements were calculated. To verify the empirical EM, actual EM of the three was determined by nanoindentation test using Oliver and Pharr method. The dependence of EM on test regions and loading directions were also discussed. The empirical EM of the mandible element is in the range of 3.7 to 23.4 Gpa, and EM of the cortical element is in the range of 8.6 to 13.6 Gpa. In comparison, the actual EM of cortical bone tested by nanoindentation method is in the range of 10.0 to 22.0 Gpa. The tested EM is varied with the test regions and loading directions. The difference in the values of EM determined by the empirical analysis and by the nanoindentation test is approximately 5.0 Gpa. A mandibular finite element model with heterogeneous material properties is built. By analyzing the EM value of this model, it is concluded that the actual EM in anterior-posterior direction in mandibular ramus and EM in superior-inferior direction in mandibular body match the empirical EM better than the other directions.
International Nuclear Information System (INIS)
Barbieri, R.A.; Gastal, F.P.S.L.; Filho, A.C.
2005-01-01
Unbounded prestressed concrete has a growing importance all over the world and may be an useful technique for the structures involved in the construction of nuclear facilities. The absence of bonding means no strain compatibility so that equations developed for reinforced concrete are no longer valid. Practical estimates about the ultimate stress in the unbounded tendons may be obtained with empirical or numerical methods only. In order to contribute to the understanding on the behaviour of unbounded prestressed concrete members, a numerical model has been developed using a hybrid type finite element formulation for planar frame structures. Instead of short elements, as in the conventional finite element formulation, long elements may be used, improving computational efficiency. A further advantage is that the curvature variation within the element is obtained with higher accuracy if compared to the traditional formulation. This feature is important for unbounded tendons since its stresses depend on the whole member deformation. Second order effects in the planar frame are considered with either Updated or Partially Updated Lagrangian approaches. Instantaneous and time dependent behaviour as well as cyclic loads are considered too. Comparison with experimental results for prestressed concrete beams shows the adequacy of the proposed model. (authors)
Roediger, T.; Siebert, C.; Krause, P.
2008-12-01
The arid to semiarid Middle East is a region of extreme growth of population. Hence, the rare and over- expoitated water resources in that region have to be more protected against antropogenic and geogenic pollution. One way to help solving that complex issue is to develop an intelligent and integrated strategy to manage all available water resources, which is the aim of the multilateral SMART-project in the Lower Jordan Valley. To generate such an IWRM, all water resources (groundwater, surface runoff, waste water) of the valley and its shoulders have to be quanti- and qualitatively evaluated. The strategy of SMART is to upscale knowledge, extracted from local catchment areas to the project scale, which covers the area between Sea of Galilee, Jerusalem, Dead Sea and Amman. The study areas of the here presented sub-project are the Wadis Qilt (Palestine) and Al Arab (Jordan). The aim of the sub-project is to evaluate natural resources on catchment scale by combining hydrochemical and hydraulical methods to develop a high precision model. Concerning the quantification of the system, two seperated models will be linked: a numerical finite element flow-model for the groundwater passage and a new devolped hydrological model JAMS, which is excellently prepared for humid conditions. The power of JAMS is the highly accurate assessment of soil moisture balance and consequently of surface runoff and groundwater recharge. However, the empirical equations and input parameters have to be adjusted onto the conditions of the semiarid Wadi Al Arab and the arid Wadi Qilt. After the adaption of JAMS, the spatially and temporarily differentiated calculation of runoff and groundwater recharge is possible. Beside climatic gradients, the key issue is, to correctly evaluate the evapotranspiration in respect to the different classes of landuse. In the study area Wadi Al Arab, the groundwater recharge was calculated as area-indicated output parameter of JAMS. This output was used to be the
A Reduced Three Dimensional Model for SAW Sensors Using Finite Element Analysis.
El Gowini, Mohamed M; Moussa, Walied A
2009-01-01
A major problem that often arises in modeling Micro Electro Mechanical Systems (MEMS) such as Surface Acoustic Wave (SAW) sensors using Finite Element Analysis (FEA) is the extensive computational capacity required. In this study a new approach is adopted to significantly reduce the computational capacity needed for analyzing the response of a SAW sensor using the finite element (FE) method. The approach is based on the plane wave solution where the properties of the wave vary in two dimensions and are uniform along the thickness of the device. The plane wave solution therefore allows the thickness of the SAW device model to be minimized; the model is referred to as a Reduced 3D Model (R3D). Various configurations of this novel R3D model are developed and compared with theoretical and experimental frequency data and the results show very good agreement. In addition, two-dimensional (2D) models with similar configurations to the R3D are developed for comparison since the 2D approach is widely adopted in the literature as a computationally inexpensive approach to model SAW sensors using the FE method. Results illustrate that the R3D model is capable of capturing the SAW response more accurately than the 2D model; this is demonstrated by comparison of centre frequency and insertion loss values. These results are very encouraging and indicate that the R3D model is capable of capturing the MEMS-based SAW sensor response without being computationally expensive.
A one-dimensional mixed porohyperelastic transport swelling finite element model with growth
Harper, J.L.; Simon, B.R.; Vande Geest, J.P.
2013-01-01
A one-dimensional, large-strain, mixed porohyperelastic transport and swelling (MPHETS) finite element model was developed in MATLAB and incorporated with a well-known growth model for soft tissues to allow the model to grow (increase in length) or shrink (decrease in length) at constant material density. By using the finite element model to determine the deformation and stress state, it is possible to implement different growth laws in the program in the future to simulate how soft tissues grow and behave when exposed to various stimuli (e.g. mechanical, chemical, or electrical). The essential assumptions needed to use the MPHETS model with growth are clearly identified and explained in this paper. The primary assumption in this work, however, is that the stress upon which growth acts is the stress in the solid skeleton, i.e. the effective stress, Seff. It is shown that significantly different amounts of growth are experienced for the same loading conditions when using a porohyperelastic model as compared to a purely solid model. In one particular example, approximately 51% less total growth occurred in the MPHETS model than in the solid model even though both problems were subjected to the same external loading. This work represents a first step in developing more sophisticated models capable of capturing the complex mechanical and biochemical environment in growing and remodeling tissues. PMID:23778062
FEWA-FEMA, Finite Element Method Model of Materials Transport in Ground Water
International Nuclear Information System (INIS)
1989-01-01
1 - Description of program or function: FEWA is a finite element model designed to treat complex transient real-world problems of sources/ sinks, Dirichlet boundary values, Neumann or Cauchy fluxes, and leaky confining beds (aquitards) simultaneously. FEMA deals with the construction, verification, and demonstration of a finite element model of material transport through aquifers. The particular features of FEMA are its versatility and flexibility to deal with as many real-world problems as possible. 2 - Method of solution: In FEWA, both quadrilateral and triangular elements, or a combination of the two, are used to facilitate the discretization of a compound region with highly irregular curved boundaries. Also, a pointwise iteration solution strategy for solving the matrix equation approximating the partial differential equation is included as an alternative to the direct solution method. This inclusion makes the model efficient and applicable to large-field problems when the bandwidth of the matrix becomes large. Three optional sorption models are embodied in FEMA. These are linear isotherm and Freundlich and Langmuir nonlinear isotherms. Point as well as distributed source/sinks are included to represent artificial injection/withdrawals and natural infiltration of precipitation. All source/sinks can be transient or steady state. Finite element methods are adopted to transform the governing differential equations to the matrix equation. To increase the applicability of the model in terms of stability and convergence, twelve options have been included for the derivation of the matrix equation. The resulting matrix equation is solved with either the direct elimination or successive relaxation technique. 3 - Restrictions on the complexity of the problem: None noted
Generalized finite element dynamic modelling and simulation for flexible robot manipulators
Zhou, Feng
1993-01-01
The finite element approach is used to model multi-link flexible robotic manipulators. The kinematic character of flexible manipulators is analyzed using body-fixed and link element attached coordinates. Dynamic equations for flexible robot manipulators are then derived. The position of each point on the link is expressed using a transformation matrix, and the kinetic and potential energy for each element is computed and summed over all the elements. The Lagrangian formulation is applied to set up the dynamic equations of the system. Computational simulations are performed on single- and two-link manipulators with and without torque to check the validity and correctness of the derived dynamic equations. The Runge-Kutta method is used to solve the dynamic equations for flexible manipulators on which all the joints are revolute.
Numerical modelling of MPA-CVD reactors with the discontinuous Galerkin finite element method
Houston, Paul; Sime, Nathan
2017-07-01
In this article we develop a fully self consistent mathematical model describing the formation of a hydrogen plasma in a microwave power assisted chemical vapour deposition (MPA-CVD) reactor employed for the manufacture of synthetic diamond. The underlying multi-physics model includes constituent equations for the background gas mass average velocity, gas temperature, electromagnetic field energy and plasma density. The proposed mathematical model is numerically approximated based on exploiting the discontinuous Galerkin finite element method. We demonstrate the practical performance of this computational approach on a variety of CVD reactor geometries for a range of operating conditions.
A model finite-element to analyse the mechanical behavior of a PWR fuel rod
International Nuclear Information System (INIS)
Galeao, A.C.N.R.; Tanajura, C.A.S.
1988-01-01
A model to analyse the mechanical behavior of a PWR fuel rod is presented. We drew our attention to the phenomenon of pellet-pellet and pellet-cladding contact by taking advantage of an elastic model which include the effects of thermal gradients, cladding internal and external pressures, swelling and initial relocation. The problem of contact gives rise ro a variational formulation which employs Lagrangian multipliers. An iterative scheme is constructed and the finite element method is applied to obtain the numerical solution. Some results and comments are presented to examine the performance of the model. (author) [pt
Neurosurgery simulation using non-linear finite element modeling and haptic interaction
Lee, Huai-Ping; Audette, Michel; Joldes, Grand R.; Enquobahrie, Andinet
2012-02-01
Real-time surgical simulation is becoming an important component of surgical training. To meet the realtime requirement, however, the accuracy of the biomechancial modeling of soft tissue is often compromised due to computing resource constraints. Furthermore, haptic integration presents an additional challenge with its requirement for a high update rate. As a result, most real-time surgical simulation systems employ a linear elasticity model, simplified numerical methods such as the boundary element method or spring-particle systems, and coarse volumetric meshes. However, these systems are not clinically realistic. We present here an ongoing work aimed at developing an efficient and physically realistic neurosurgery simulator using a non-linear finite element method (FEM) with haptic interaction. Real-time finite element analysis is achieved by utilizing the total Lagrangian explicit dynamic (TLED) formulation and GPU acceleration of per-node and per-element operations. We employ a virtual coupling method for separating deformable body simulation and collision detection from haptic rendering, which needs to be updated at a much higher rate than the visual simulation. The system provides accurate biomechancial modeling of soft tissue while retaining a real-time performance with haptic interaction. However, our experiments showed that the stability of the simulator depends heavily on the material property of the tissue and the speed of colliding objects. Hence, additional efforts including dynamic relaxation are required to improve the stability of the system.
International Nuclear Information System (INIS)
Rousseau, J.
2009-07-01
That study focuses on concrete structures submitted to impact loading and is aimed at predicting local damage in the vicinity of an impact zone as well as the global response of the structure. The Discrete Element Method (DEM) seems particularly well suited in this context for modeling fractures. An identification process of DEM material parameters from macroscopic data (Young's modulus, compressive and tensile strength, fracture energy, etc.) will first be presented for the purpose of enhancing reproducibility and reliability of the simulation results with DE samples of various sizes. Then, a particular interaction, between concrete and steel elements, was developed for the simulation of reinforced concrete. The discrete elements method was validated on quasi-static and dynamic tests carried out on small samples of concrete and reinforced concrete. Finally, discrete elements were used to simulate impacts on reinforced concrete slabs in order to confront the results with experimental tests. The modeling of a large structure by means of DEM may lead to prohibitive computation times. A refined discretization becomes required in the vicinity of the impact, while the structure may be modeled using a coarse FE mesh further from the impact area, where the material behaves elastically. A coupled discrete-finite element approach is thus proposed: the impact zone is modeled by means of DE and elastic FE are used on the rest of the structure. An existing method for 3D finite elements was extended to shells. This new method was then validated on many quasi-static and dynamic tests. The proposed approach is then applied to an impact on a concrete structure in order to validate the coupled method and compare computation times. (author)
A hybrid finite element approach to modeling sound radiation from circular and rectangular ducts.
Duan, Wenbo; Kirby, Ray
2012-05-01
A numerical model based on a hybrid finite element method is developed that seeks to join sound pressure fields in interior and exterior regions. The hybrid method is applied to the analysis of sound radiation from open pipes, or ducts, and uses mode matching to couple a finite element discretization of the region surrounding the open end of the duct to wave based modal expansions for adjoining interior and exterior regions. The hybrid method facilitates the analysis of ducts of arbitrary but uniform cross section as well the study of conical flanges and here a modal expansion based on spherical harmonics is applied. Predictions are benchmarked against analytic solutions for the limiting cases of flanged and unflanged circular ducts and excellent agreement between the two methods is observed. Predictions are also presented for flanged and unflanged rectangular ducts, and because the hybrid method retains the sparse banded and symmetric matrices of the traditional finite element method, it is shown that predictions can be obtained within an acceptable time frame even for a three dimensional problem.
A finite element head and neck model as a supportive tool for deformable image registration.
Kim, Jihun; Saitou, Kazuhiro; Matuszak, Martha M; Balter, James M
2016-07-01
A finite element (FE) head and neck model was developed as a tool to aid investigations and development of deformable image registration and patient modeling in radiation oncology. Useful aspects of a FE model for these purposes include ability to produce realistic deformations (similar to those seen in patients over the course of treatment) and a rational means of generating new configurations, e.g., via the application of force and/or displacement boundary conditions. The model was constructed based on a cone-beam computed tomography image of a head and neck cancer patient. The three-node triangular surface meshes created for the bony elements (skull, mandible, and cervical spine) and joint elements were integrated into a skeletal system and combined with the exterior surface. Nodes were additionally created inside the surface structures which were composed of the three-node triangular surface meshes, so that four-node tetrahedral FE elements were created over the whole region of the model. The bony elements were modeled as a homogeneous linear elastic material connected by intervertebral disks. The surrounding tissues were modeled as a homogeneous linear elastic material. Under force or displacement boundary conditions, FE analysis on the model calculates approximate solutions of the displacement vector field. A FE head and neck model was constructed that skull, mandible, and cervical vertebrae were mechanically connected by disks. The developed FE model is capable of generating realistic deformations that are strain-free for the bony elements and of creating new configurations of the skeletal system with the surrounding tissues reasonably deformed. The FE model can generate realistic deformations for skeletal elements. In addition, the model provides a way of evaluating the accuracy of image alignment methods by producing a ground truth deformation and correspondingly simulated images. The ability to combine force and displacement conditions provides
A new approach for assigning bone material properties from CT images into finite element models.
Chen, G; Schmutz, B; Epari, D; Rathnayaka, K; Ibrahim, S; Schuetz, M A; Pearcy, M J
2010-03-22
Generation of subject-specific finite element (FE) models from computed tomography (CT) datasets is of significance for application of the FE analysis to bone structures. A great challenge that remains is the automatic assignment of bone material properties from CT Hounsfield Units into finite element models. This paper proposes a new assignment approach, in which material properties are directly assigned to each integration point. Instead of modifying the dataset of FE models, the proposed approach divides the assignment procedure into two steps: generating the data file of the image intensity of a bone in a MATLAB program and reading the file into ABAQUS via user subroutines. Its accuracy has been validated by assigning the density of a bone phantom into a FE model. The proposed approach has been applied to the FE model of a sheep tibia and its applicability tested on a variety of element types. The proposed assignment approach is simple and illustrative. It can be easily modified to fit users' situations. Copyright (c) 2009 Elsevier Ltd. All rights reserved.
Study of gap conductance model for thermo mechanical fully coupled finite element model
International Nuclear Information System (INIS)
Kim, Hyo Cha; Yang, Yong Sik; Kim, Dae Ho; Bang, Je Geon; Kim, Sun Ki; Koo, Yang Hyun
2012-01-01
A light water reactor (LWR) fuel rod consists of zirconium alloy cladding and uranium dioxide pellets, with a slight gap between them. Therefore, the mechanical integrity of zirconium alloy cladding is the most critical issue, as it is an important barrier for fission products released into the environment. To evaluate the stress and strain of the cladding during operation, fuel performance codes with a one-dimensional (1D) approach have been reported since the 1970s. However, it is difficult for a 1D model to simulate the stress and strain of the cladding accurately owing to a lack of degree of freedom. A LWR fuel performance code should include thermo-mechanical coupled model owing to the existence of the fuel-cladding gap. Generally, the gap that is filled with helium gas results in temperature drop along radius direction. The gap conductance that determines temperature gradient within the gap is very sensitive to gap thickness. For instance, once the gap size increases up to several microns in certain region, difference of surface temperatures increases up to 100 Kelvin. Therefore, iterative thermo-mechanical coupled analysis is required to solve temperature distribution throughout pellet and cladding. Consequently, the Finite Element (FE) module, which can simulate a higher degree of freedom numerically, is an indispensable requirement to understand the thermomechanical behavior of cladding. FRAPCON-3, which is reliable performance code, has iterative loop for thermo-mechanical coupled calculation to solve 1D gap conductance model. In FEMAXI-III, 1D thermal analysis module and FE module for stress-strain analysis were separated. 1D thermal module includes iterative analysis between them. DIONISIO code focused on thermal contact model as function of surface roughness and contact pressure when the gap is closed. In previous works, gap conductance model has been developed only for 1D model or hybrid model (1D and FE). To simulate temperature, stress and strain
Finite element modeling of 129Xe diffusive gas exchange NMR in the human alveoli
Stewart, Neil J.; Parra-Robles, Juan; Wild, Jim M.
2016-10-01
Existing models of 129Xe diffusive exchange for lung microstructural modeling with time-resolved MR spectroscopy data have considered analytical solutions to one-dimensional, homogeneous models of the lungs with specific assumptions about the alveolar geometry. In order to establish a model system for simulating the effects of physiologically-realistic changes in physical and microstructural parameters on 129Xe exchange NMR, we have developed a 3D alveolar capillary model for finite element analysis. To account for the heterogeneity of the alveolar geometry across the lungs, we have derived realistic geometries for finite element analysis based on 2D histological samples and 3D micro-CT image volumes obtained from ex vivo biopsies of lung tissue from normal subjects and patients with interstitial lung disease. The 3D alveolar capillary model permits investigation of the impact of alveolar geometrical parameters and diffusion and perfusion coefficients on the in vivo measured 129Xe CSSR signal response. The heterogeneity of alveolar microstructure that is accounted for in image-based models resulted in considerable alterations to the shape of the 129Xe diffusive uptake curve when compared to 1D models. Our findings have important implications for the future design and optimization of 129Xe MR experiments and in the interpretation of lung microstructural changes from this data.
International Nuclear Information System (INIS)
Viswanathan, H.S.
1995-01-01
The finite element code FEHMN is a three-dimensional finite element heat and mass transport simulator that can handle complex stratigraphy and nonlinear processes such as vadose zone flow, heat flow and solute transport. Scientists at LANL have been developed hydrologic flow and transport models of the Yucca Mountain site using FEHMN. Previous FEHMN simulations have used an equivalent K d model to model solute transport. In this thesis, FEHMN is modified making it possible to simulate the transport of a species with a rigorous chemical model. Including the rigorous chemical equations into FEHMN simulations should provide for more representative transport models for highly reactive chemical species. A fully kinetic formulation is chosen for the FEHMN reactive transport model. Several methods are available to computationally implement a fully kinetic formulation. Different numerical algorithms are investigated in order to optimize computational efficiency and memory requirements of the reactive transport model. The best algorithm of those investigated is then incorporated into FEHMN. The algorithm chosen requires for the user to place strongly coupled species into groups which are then solved for simultaneously using FEHMN. The complete reactive transport model is verified over a wide variety of problems and is shown to be working properly. The simulations demonstrate that gas flow and carbonate chemistry can significantly affect 14 C transport at Yucca Mountain. The simulations also provide that the new capabilities of FEHMN can be used to refine and buttress already existing Yucca Mountain radionuclide transport studies
A three-dimensional finite element model for biomechanical analysis of the hip.
Chen, Guang-Xing; Yang, Liu; Li, Kai; He, Rui; Yang, Bin; Zhan, Yan; Wang, Zhi-Jun; Yu, Bing-Nin; Jian, Zhe
2013-11-01
The objective of this study was to construct a three-dimensional (3D) finite element model of the hip. The images of the hip were obtained from Chinese visible human dataset. The hip model includes acetabular bone, cartilage, labrum, and bone. The cartilage of femoral head was constructed using the AutoCAD and Solidworks software. The hip model was imported into ABAQUS analysis system. The contact surface of the hip joint was meshed. To verify the model, the single leg peak force was loaded, and contact area of the cartilage and labrum of the hip and pressure distribution in these structures were observed. The constructed 3D hip model reflected the real hip anatomy. Further, this model reflected biomechanical behavior similar to previous studies. In conclusion, this 3D finite element hip model avoids the disadvantages of other construction methods, such as imprecision of cartilage construction and the absence of labrum. Further, it provides basic data critical for accurately modeling normal and abnormal loads, and the effects of abnormal loads on the hip.
A parametric model order reduction technique for poroelastic finite element models.
Lappano, Ettore; Polanz, Markus; Desmet, Wim; Mundo, Domenico
2017-10-01
This research presents a parametric model order reduction approach for vibro-acoustic problems in the frequency domain of systems containing poroelastic materials (PEM). The method is applied to the Finite Element (FE) discretization of the weak u-p integral formulation based on the Biot-Allard theory and makes use of reduced basis (RB) methods typically employed for parametric problems. The parametric reduction is obtained rewriting the Biot-Allard FE equations for poroelastic materials using an affine representation of the frequency (therefore allowing for RB methods) and projecting the frequency-dependent PEM system on a global reduced order basis generated with the proper orthogonal decomposition instead of standard modal approaches. This has proven to be better suited to describe the nonlinear frequency dependence and the strong coupling introduced by damping. The methodology presented is tested on two three-dimensional systems: in the first experiment, the surface impedance of a PEM layer sample is calculated and compared with results of the literature; in the second, the reduced order model of a multilayer system coupled to an air cavity is assessed and the results are compared to those of the reference FE model.
Kou, Jisheng
2017-06-09
In this paper, a new three-field weak formulation for Stokes problems is developed, and from this, a dual-mixed finite element method is proposed on a rectangular mesh. In the proposed mixed methods, the components of stress tensor are approximated by piecewise constant functions or Q1 functions, while the velocity and pressure are discretized by the lowest-order Raviart-Thomas element and the piecewise constant functions, respectively. Using quadrature rules, we demonstrate that this scheme can be reduced into a finite volume method on staggered grid, which is extensively used in computational fluid mechanics and engineering.
Comparison of stability in the operative treatment of pelvic injuries in a finite element model.
Bodzay, Tamás; Flóris, István; Váradi, Károly
2011-10-01
The comparison of the stability of four surgical methods for the treatment of vertically and rotationally unstable type C pelvic ring injuries. We produced a type C pelvic ring injury (type Denis II fracture of the sacrum and symphysiolysis) on a finite element model, in the case of standing on both feet. We stabilized the symphysiolysis with a five-hole reconstruction plate; the sacrum fracture was fixed in the first experiment with two, two-hole reconstruction plates on the ventral surface, in the second one we applied dorsally the transsacral, narrow DC plate, in the third one with KFI-H plate, and in the last one with iliosacral screw. Finite element modeling was performed by the use of the ALGOR software. Not only bones and joints, but joints and mechanically important ligaments were modeled as well. We measured the shift between the two surfaces of the fracture gap, compared to the results of measurements accomplished on cadaver models. Larger shift could be elicited after transsacral plating than after direct plating. These results correspond to those of the parallel investigation of the bony ligamentous cadaver pelvis specimens. The shift values after KFI-H plating and iliosacral screw fixation are larger than after direct plating, but smaller than after transsacral plating. The tension created in the implants is less than the allowed values; therefore, the choice of operation should depend on the type of injury. The finite element model may be utilized for the comparison of different methods of osteosynthesis for the treatment of injuries described above. Due to several difficulties in investigations performed on cadaver specimens, this model has undoubted utility.
A comparison of numerical methods used for finite element modelling of soft tissue deformation
Pathmanathan, P
2009-05-01
Soft tissue deformation is often modelled using incompressible non-linear elasticity, with solutions computed using the finite element method. There are a range of options available when using the finite element method, in particular the polynomial degree of the basis functions used for interpolating position and pressure, and the type of element making up the mesh. The effect of these choices on the accuracy of the computed solution is investigated, using a selection of model problems motivated by typical deformations seen in soft tissue modelling. Model problems are set up with discontinuous material properties (as is the case for the breast), steeply changing gradients in the body force (as found in contracting cardiac tissue), and discontinuous first derivatives in the solution at the boundary, caused by a discontinuous applied force (as in the breast during mammography). It was found that the choice of pressure basis functions is vital in the presence of a material interface, higher-order schemes do not perform as well as may be expected when there are sharp gradients, and in general it is important to take the expected regularity of the solution into account when choosing a numerical scheme. © IMechE 2009.
Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.
1995-01-01
A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme was computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressirve wave environment such as that usually encountered in a commercial aircraft engine and most laboratory settings.
Quiza, Ramón; Davim, J Paulo
2012-01-01
Artificial intelligence (AI) techniques and the finite element method (FEM) are both powerful computing tools, which are extensively used for modeling and optimizing manufacturing processes. The combination of these tools has resulted in a new flexible and robust approach as several recent studies have shown. This book aims to review the work already done in this field as well as to expose the new possibilities and foreseen trends. The book is expected to be useful for postgraduate students and researchers, working in the area of modeling and optimization of manufacturing processes.
Evaluating the accuracy of finite element models at reduced length scales
Kemp, Connor
Finite element models are used frequently in both engineering and scientific research. While they can provide useful information as to the performance of materials, as length scales are decreased more sophisticated model descriptions are required. It is also important to develop methods by which existing models may be verified against experimental findings. The present study evaluates the ability of various finite element models to predict materials behaviour at length scales ranging from several microns to tens of nanometers. Considering this motivation, this thesis is provided in manuscript form with the bulk of material coming from two case studies. Following an overview of relevant literature in Chapter 2, Chapter 3 considers the nucleation of delta-zirconium hydrides in a Zircaloy-2 matrix. Zirconium hydrides are an important topic in the nuclear industry as they form a brittle phase which leads to delayed hydride cracking during reactor start-up and shut-down. Several FE models are used to compare present results with literature findings and illustrate the weaknesses of standard FE approaches. It is shown that standard continuum techniques do not sufficiently capture the interfacial effects of an inclusion-matrix system. By using nano-scale material descriptions, nucleation lattice strains are obtained which are in good agreement with previous experimental studies. The motivation for Chapter 4 stems from a recognized need to develop a method for modeling corrosion behaviour of materials. Corrosion is also an issue for reactor design and an ability to predict failure points is needed. Finite element models could be used for this purpose, provided model accuracy is verified first. In Chapter 4 a technique is developed which facilitates the extraction of sub-micron resolution strain data from correlation images obtained during in-situ tensile deformation. By comparing image correlation results with a crystal plasticity finite element code it is found that good
An axisymmetrical non-linear finite element model for induction heating in injection molding tools
DEFF Research Database (Denmark)
Guerrier, Patrick; Nielsen, Kaspar Kirstein; Menotti, Stefano
2016-01-01
To analyze the heating and cooling phase of an induction heated injection molding tool accurately, the temperature dependent magnetic properties, namely the non-linear B-H curves, need to be accounted for in an induction heating simulation. Hence, a finite element model has been developed...... in to the injection molding tool. The model shows very good agreement with the experimental temperature measurements. It is also shown that the non-linearity can be used without the temperature dependency in some cases, and a proposed method is presented of how to estimate an effective linear permeability to use...
Moreno Chaparro, Nicolas
2013-06-01
A variational multi scale approach to model blood flow through arteries is proposed. A finite element discretization to represent the coarse scales (macro size), is coupled to smoothed dissipative particle dynamics that captures the fine scale features (micro scale). Blood is assumed to be incompressible, and flow is described through the Navier Stokes equation. The proposed cou- pling is tested with two benchmark problems, in fully coupled systems. Further refinements of the model can be incorporated in order to explicitly include blood constituents and non-Newtonian behavior. The suggested algorithm can be used with any particle-based method able to solve the Navier-Stokes equation.
Chen, Ming; Mogul, David Jeffery
2009-04-30
Computational studies of the head utilizing finite element models (FEMs) have been used to investigate a wide variety of brain-electromagnetic (EM) field interaction phenomena including magnetic stimulation of the head using transcranial magnetic stimulation (TMS), direct electric stimulation of the brain for electroconvulsive therapy, and electroencephalography source localization. However, no human head model of sufficient complexity for studying the biophysics under these circumstances has been developed which utilizes structures at both the regional and cellular levels and provides well-defined smooth boundaries between tissues of different conductivities and orientations. The main barrier for building such accurate head models is the complex modeling procedures that include 3D object reconstruction and optimized meshing. In this study, a structurally detailed finite element model of the human head was generated that includes details to the level of cerebral gyri and sulci by combining computed tomography and magnetic resonance images. Furthermore, cortical columns that contain conductive processes of pyramidal neurons traversing the neocortical layers were included in the head model thus providing structure at or near the cellular level. These refinements provide a much more realistic model to investigate the effects of TMS on brain electrophysiology in the neocortex.
Peridynamic Multiscale Finite Element Methods
Energy Technology Data Exchange (ETDEWEB)
Costa, Timothy [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bond, Stephen D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Littlewood, David John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Moore, Stan Gerald [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-12-01
The problem of computing quantum-accurate design-scale solutions to mechanics problems is rich with applications and serves as the background to modern multiscale science research. The prob- lem can be broken into component problems comprised of communicating across adjacent scales, which when strung together create a pipeline for information to travel from quantum scales to design scales. Traditionally, this involves connections between a) quantum electronic structure calculations and molecular dynamics and between b) molecular dynamics and local partial differ- ential equation models at the design scale. The second step, b), is particularly challenging since the appropriate scales of molecular dynamic and local partial differential equation models do not overlap. The peridynamic model for continuum mechanics provides an advantage in this endeavor, as the basic equations of peridynamics are valid at a wide range of scales limiting from the classical partial differential equation models valid at the design scale to the scale of molecular dynamics. In this work we focus on the development of multiscale finite element methods for the peridynamic model, in an effort to create a mathematically consistent channel for microscale information to travel from the upper limits of the molecular dynamics scale to the design scale. In particular, we first develop a Nonlocal Multiscale Finite Element Method which solves the peridynamic model at multiple scales to include microscale information at the coarse-scale. We then consider a method that solves a fine-scale peridynamic model to build element-support basis functions for a coarse- scale local partial differential equation model, called the Mixed Locality Multiscale Finite Element Method. Given decades of research and development into finite element codes for the local partial differential equation models of continuum mechanics there is a strong desire to couple local and nonlocal models to leverage the speed and state of the
Taddei, Fulvia; Martelli, Saulo; Gill, Harinderjit Singh; Cristofolini, Luca; Viceconti, Marco
2010-02-01
Metal-on-metal hip resurfacing is becoming increasingly popular, and a number of new devices have been recently introduced that, in the short term, appear to have satisfactory outcome but many questions are still open on the biomechanics of the resurfaced femur. This could be investigated by means of finite element analysis, but, in order to be effective in discerning potential critical conditions, the accuracy of the models' predictions should be assessed. The major goal of this study was to validate, through a combined experimental-numerical study, a finite element modeling procedure for the simulation of resurfaced femurs. In addition, a preliminary biomechanical analysis of the changes induced in the femoral neck biomechanics by the presence of the device was performed, under a physiologic range of hip joint reaction directions. For this purpose, in vitro tests and a finite element model based on the same specimen were developed using a cadaver femur. The study focused on the Conserve Plus, one of the most common contemporary resurfacing designs. Five loading configurations were identified to correspond to the extremes of physiological directions for the hip joint. The agreement between experimental measurements and numerical predictions was good both in the prediction of the femoral strains (R(2)>0.9), and in the prosthesis micromotions (errorprosthesis, apart from localized strain increments that can be considerable, always predicted near the stem. Low micromotions and contact pressure were predicted, suggesting a good stability of the prosthesis. The model accuracy was good in the prediction of the femoral strains and moderately good in the prediction of the bone-prosthesis micromovements. Although the investigated loading conditions were not completely physiological, the preliminary biomechanical analysis showed relatively small changes for the proximal femur after implantation. This validated model can support realistic simulations to examine physiological
Finite Element Modeling of Avascular Tumor Growth Using a Stress-Driven Model.
Iranmanesh, Faezeh; Nazari, Mohammad Ali
2017-08-01
Tumor growth being a multistage process has been investigated from different aspects. In the present study, an attempt is made to represent a constitutive-structure-based model of avascular tumor growth in which the effects of tensile stresses caused by collagen fibers are considered. Collagen fibers as a source of anisotropy in the structure of tissue are taken into account using a continuous fiber distribution formulation. To this end, a finite element modeling is implemented in which a neo-Hookean hyperelastic material is assigned to the tumor and its surrounding host. The tumor is supplied with a growth term. The growth term includes the effect of parameters such as nutrient concentration on the tumor growth and the tumor's solid phase content in the formulation. Results of the study revealed that decrease of solid phase is indicative of decrease in growth rate and the final steady-state value of tumor's radius. Moreover, fiber distribution affects the final shape of the tumor, and it could be used to control the shape and geometry of the tumor in complex morphologies. Finally, the findings demonstrated that the exerted stresses on the tumor increase as time passes. Compression of tumor cells leads to the reduction of tumor growth rate until it gradually reaches an equilibrium radius. This finding is in accordance with experimental data. Hence, this formulation can be deployed to evaluate both the residual stresses induced by growth and the mechanical interactions with the host tissue.
International Nuclear Information System (INIS)
Johnson, H.W.; Vaish, A.K.; Porter, F.L.; McGeorge, R.
1975-01-01
A modelling technique which can be used to obtain the dynamic response of a floating nuclear plant (FNP) moored in an artificial basin is presented. Hydrodynamic effects of the seawater in the basin have a significant impact on the response of the FNP and must be included. A three dimensional model of the platform and mooring system (using beam elements) is used, with the hydrodynamic effects represented by added mass and damping. For an essentially square plant in close proximity to the site structures, the three dimensional nature of the basin must be considered in evaluating the added mass and damping. A method for estimating these effects from planer finite element analyses is developed. The accuracy of the planar finite element model in obtaining two-dimensional added mass and damping is shown through comparison with existing the documented results. In addition, a comparison is shown for open ocean added mass and damping with a three-dimensional solution using velocity potential functions. It is concluded that the overall technique results in a reasonable and conservative calculation of the dynamic response of the floating nuclear plant. (orig./HP) [de
Finite element model based on refined plate theories for laminated glass units
Directory of Open Access Journals (Sweden)
Alena Zemanová
Full Text Available AbstractLaminated glass units exhibit complex response as a result of different mechanical behavior and properties of glass and polymer foil. We aim to develop a finite element model for elastic laminated glass plates based on the refined plate theory by Mau. For a geometrically nonlinear description of the behavior of units, each layer behaves according to the Reissner-Mindlin kinematics, complemented with membrane effects and the von Kármán assumptions. Nodal Lagrange multipliers enforce the compatibility of independent layers in this approach. We have derived the discretized model by the energy-minimization arguments, assuming that the unknown fields are approximated by bi-linear functions at the element level, and solved the resulting system by the Newton method with consistent linearization. We have demonstrated through verification and validation examples that the proposed formulation is reliable and accurately reproduces the behavior of laminated glass units. This study represents a first step to the development of a comprehensive, mechanics-based model for laminated glass systems that is suitable for implementation in common engineering finite element solvers.
A nonlinear finite element model of a piezoelectric tube actuator with hysteresis and creep
International Nuclear Information System (INIS)
Chung, S H; Fung, Eric H K
2010-01-01
Piezoelectric tube actuators are commonly used for nanopositioning in atomic force microscopes (AFMs). However, piezoelectric tube actuators exhibit hysteresis and creep which significantly limit the accuracy of nanopositioning. A finite element model of a piezoelectric tube actuator with hysteresis and creep is important for control purposes, but so far one has not been developed. The purpose of this paper is to present a nonlinear finite element (FE) model with hysteresis and creep for design purposes. Prandtl–Ishlinskii (PI) hysteresis operators and creep operators are adopted into constitutive equations. The nonlinear FE model is formulated using energy approach and Hamilton's principle. The parameters of the PI hysteresis operators and the creep operators are identified by comparing the simulation results and experimental results of other researchers. The working operation of the piezoelectric tube actuator is simulated by the reduced order FE model, and the displacement error due to hysteresis, creep and coupling effect is investigated. An output feedback controller is implemented into the reduced order FE model to show that this model is controllable
Integration of system identification and finite element modelling of nonlinear vibrating structures
Cooper, Samson B.; DiMaio, Dario; Ewins, David J.
2018-03-01
The Finite Element Method (FEM), Experimental modal analysis (EMA) and other linear analysis techniques have been established as reliable tools for the dynamic analysis of engineering structures. They are often used to provide solutions to small and large structures and other variety of cases in structural dynamics, even those exhibiting a certain degree of nonlinearity. Unfortunately, when the nonlinear effects are substantial or the accuracy of the predicted response is of vital importance, a linear finite element model will generally prove to be unsatisfactory. As a result, the validated linear FE model requires further enhancement so that it can represent and predict the nonlinear behaviour exhibited by the structure. In this paper, a pragmatic approach to integrating test-based system identification and FE modelling of a nonlinear structure is presented. This integration is based on three different phases: the first phase involves the derivation of an Underlying Linear Model (ULM) of the structure, the second phase includes experiment-based nonlinear identification using measured time series and the third phase covers augmenting the linear FE model and experimental validation of the nonlinear FE model. The proposed case study is demonstrated on a twin cantilever beam assembly coupled with a flexible arch shaped beam. In this case, polynomial-type nonlinearities are identified and validated with force-controlled stepped-sine test data at several excitation levels.
Finite element models to represent seismic activity of the Indian plate
Directory of Open Access Journals (Sweden)
S. Jayalakshmi
2017-01-01
Full Text Available Quantification of seismic activity is one of the most challenging problems faced by earthquake engineers in probabilistic seismic hazard analysis. Currently, this problem has been attempted using empirical approaches which are based on the regional earthquake recurrence relations from the available earthquake catalogue. However, at a specified site of engineering interest, these empirical models are associated with large number of uncertainties due to lack of sufficient data. Due to these uncertainties, engineers need to develop mechanistic models to quantify seismic activity. A wide range of techniques for modeling continental plates provides useful insights on the mechanics of plates and their seismic activity. Among the different continental plates, the Indian plate experiences diffused seismicity. In India, although Himalaya is regarded as a plate boundary and active region, the seismicity database indicates that there are other regions in the Indian shield reporting sporadic seismic activity. It is expected that mechanistic models of Indian plate, based on finite element method, simulate stress fields that quantify the seismic potential of active regions in India. This article explores the development of a finite element model for Indian plate by observing the simulated stress field for various boundary conditions, geological and rheological conditions. The study observes that the magnitude and direction of stresses in the plate is sensitive to these conditions. The numerical analysis of the models shows that the simulated stress field represents the active seismic zones in India.
Modeling bending of α-titanium with embedded polycrystal plasticity in implicit finite elements
Energy Technology Data Exchange (ETDEWEB)
Knezevic, Marko, E-mail: knezevic@lanl.gov [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lebensohn, Ricardo A. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Cazacu, Oana; Revil-Baudard, Benoit [Department of Mechanical and Aerospace Engineering, University of Florida, REEF, 1350 N Poquito Road, Shalimar, FL 32539 (United States); Proust, Gwénaëlle [School of Civil Engineering, University of Sydney, NSW 2006 (Australia); Vogel, Sven C. [Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM (United States); Nixon, Michael E. [Air Force Research Laboratory, Munitions Directorate, Eglin AFB, FL 32542 (United States)
2013-03-01
An accurate description of the mechanical response of α-titanium requires consideration of mechanical anisotropy. In this work we adapt a polycrystal self-consistent model embedded in finite elements to simulate deformation of textured α-titanium under quasi-static conditions at room temperature. Monotonic tensile and compressive macroscopic stress–strain curves, electron backscattered diffraction and neutron diffraction data are used to calibrate and validate the model. We show that the model captures with great accuracy the anisotropic strain hardening and texture evolution in the material. Comparisons between predictions and experimental data allow us to elucidate the role that the different plastic deformation mechanisms play in determining microstructure and texture evolution. The polycrystal model, embedded in an implicit finite element code, is then used to simulate geometrical changes in bending experiments of α-titanium bars. These predictions, together with results of a macroscopic orthotropic elasto-plastic model that accounts for evolving anisotropy, are compared with the experiments. Both models accurately capture the experimentally observed upward shift of the neutral axis as well as the rigidity of the material response along hard-to-deform crystallographic
International Nuclear Information System (INIS)
Onishi, Y.; Arnold, E.M.; Mayer, D.W.
1979-08-01
The finite element model, FETRA, simulates transport of sediment and radionuclides (and other contaminants, such as heavy metals, pesticides, and other toxic substances) in surface water bodies. The model is an unsteady, two-dimensional (longitudinal and lateral) model which consists of the following three submodels coupled to include sediment-contaminant interactions: (1) sediment transport submodel, (2) dissolved contaminant transport submodel, and (3) particulate contaminant (contaminant adsorbed by sediment) transport submodel. Under the current phase of the study, FETRA was modified to include sediment-wave interaction in order to extend the applicability of the model to coastal zones and large lakes (e.g., the Great Lakes) where wave actions can be one of the dominant mechanisms to transport sediment and toxic contaminant. FETRA was further modified to handle both linear and quadratic approximations to velocity and depth distributions in order to be compatible with various finite element hydrodynamic models (e.g., RMA II and CAFE) which supply hydrodynamic input data to FETRA. The next step is to apply FETRA to coastal zones to simulate transport of sediment and radionuclides with their interactions in order to test and verify the model under marine and large lacustrine environments
Agarwal, Pavan
Micromechanics of Composites analyze stresses inside any heterogeneous material. These stresses can not only be used for calculation of effective stiffness or compliance, but also for predicting strength and failure modes for these materials. This thesis is devoted to the stress analysis of unidirectional composites by finite element method. The key distinction from other finite element method modeling of the unidirectional composite was that the load on the cell was not prescribed, but was to be calculated taking into account the influence of the closest neighbors of the cell. Transversal unidirectional tension/compression and transversally symmetrical biaxial tension/compression were analyzed. In this project, two kinds of fiber materials were mainly focused upon namely; Carbon and E-glass. Here single cell and multi-cell models for cylindrical, square and hexagonal geometries were considered. The entire work was primarily focused on the cylindrical model since it constitutes the basic model in any mechanical industry. The models were experimented by taking different fiber volumes and applying relative pressure/loading to each. Stresses on the boundary were analyzed between the interface of fiber and matrix. Same was done with the multi-cell models, and analytical results were determined. Produced practical data was compared with analytical solutions for single cell and infinitely big regular array of inclusions in the matrix.
THREE-DIMENSIONAL NONLINEAR FINITE ELEMENT MODELING FOR LATERALLY LOADED VERTICAL PILES
Directory of Open Access Journals (Sweden)
M. Kubilay KELESOĞLU
2006-01-01
Full Text Available This paper presents a study for laterally loaded free head concrete piles using the finite element method (FEM. The finite element mesh is constituted from three-dimensional elements. The pile and soil boundary are defined cylindrically while lateral load is defined as single concentrated load from the top of the pile head. Various types of soil and pile properties are analysed and the load-deformation curves for different types of soils namely, sands and clays are evaluated.
A Finite Element Model for Mechanical Analysis of LHC Main Dipole Magnet Coils
Pojer, Mirko; Scandale, Walter
2007-01-01
After years of studies and observations, the mechanical stability of the LHC main dipole magnets still remains an open issue. The robustness of these magnets has already been asserted and their reliability in operation is not far from being proven. However, anomalous mechanical behaviors sometimes observed are not yet completely understood. A finite element model, which has been recently developed at CERN, aims at providing an instrument for better explaining these anomalies. Cable modeling and contact between elements, friction and mechanical hysteresis are the key features of this model. The simulation of the hysteresis experienced by the coil during collaring, presented here, is the starting point for the representation of the whole life cycle of the dipole coil.
Mesh-morphing algorithms for specimen-specific finite element modeling.
Sigal, Ian A; Hardisty, Michael R; Whyne, Cari M
2008-01-01
Despite recent advances in software for meshing specimen-specific geometries, considerable effort is still often required to produce and analyze specimen-specific models suitable for biomechanical analysis through finite element modeling. We hypothesize that it is possible to obtain accurate models by adapting a pre-existing geometry to represent a target specimen using morphing techniques. Here we present two algorithms for morphing, automated wrapping (AW) and manual landmarks (ML), and demonstrate their use to prepare specimen-specific models of caudal rat vertebrae. We evaluate the algorithms by measuring the distance between target and morphed geometries and by comparing response to axial loading simulated with finite element (FE) methods. First a traditional reconstruction process based on microCT was used to obtain two natural specimen-specific FE models. Next, the two morphing algorithms were used to compute mappings from the surface of one model, the source, to the other, the target, and to use this mapping to morph the source mesh to produce a target mesh. The microCT images were then used to assign element-specific material properties. In AW the mappings were obtained by wrapping the source and target surfaces with an auxiliary triangulated surface. In ML, landmarks were manually placed on corresponding locations on the surfaces of both source and target. Both morphing algorithms were successful in reproducing the shape of the target vertebra with a median distance between natural and morphed models of 18.8 and 32.2 microm, respectively, for AW and ML. Whereas AW-morphing produced a surface more closely resembling that of the target, ML guaranteed correspondence of the landmark locations between source and target. Morphing preserved the quality of the mesh producing models suitable for FE simulation. Moreover, there were only minor differences between natural and morphed models in predictions of deformation, strain and stress. We therefore conclude that
Modeling Overlapping Laminations in Magnetic Core Materials Using 2-D Finite-Element Analysis
DEFF Research Database (Denmark)
Jensen, Bogi Bech; Guest, Emerson David; Mecrow, Barrie C.
2015-01-01
This paper describes a technique for modeling overlapping laminations in magnetic core materials using two-dimensional finite-element (2-D FE) analysis. The magnetizing characteristic of the overlapping region is captured using a simple 2-D FE model of the periodic overlapping geometry...... and a composite material is created, which has the same magnetization characteristic. The benefit of this technique is that it allows a designer to perform design and optimization of magnetic cores with overlapped laminations using a 2-D FE model rather than a 3-D FE model, which saves modeling and simulation...... time. The modeling technique is verified experimentally by creating a composite material of a lap joint with a 3-mm overlapping region and using it in a 2-D FE model of a ring sample made up of a stack of 20 laminations. The B-H curve of the simulated ring sample is compared with the B-H curve obtained...
Modeling and finite element simulation of the magneto-mechanical behavior of ferrogels
International Nuclear Information System (INIS)
Attaran, Abdolhamid; Brummund, Jörg; Wallmersperger, Thomas
2017-01-01
In our previous study (see Ref. Attaran et al. (in press) ) we formulated a continuum model for ferrogels considering them as multicomponent materials. In the present work a reduced model for ferrogels is presented consisting only of a polymer network (P) and fixed magnetic particles (f). The reduced model is solved using the finite element method where the only degrees of freedom are mechanical displacement and magnetic potential. Elongation and contraction of a ferrogel are observed parallel and perpendicular to the applied magnetic field direction, respectively. These results are in a good qualitative agreement with experimental results. With our modeling approach, we were able to investigate (i) the influence of the magnetic field on the polymer gel containing magnetic particles and (ii) the resulting mechanical deformation of a ferrogel. - Highlights: • A reduced continuum model for ferrogels, consisting of a polymer network and fixed magnetic particles, is presented. • A coupled magneto-mechanical problem is formulated and solved numerically using the Finite Element Method in 2D. • Deformation of a ferrogel in a magnetic field for a circular gel and a strip of a ferrogel is investigated. • Elongation of the ferrogel is observed in the direction of the applied magnetic field. • Contraction of the ferrogel is observed perpendicular to the applied magnetic field.
Directory of Open Access Journals (Sweden)
Marcin Luczak
2014-01-01
Full Text Available This paper presents selected results and aspects of the multidisciplinary and interdisciplinary research oriented for the experimental and numerical study of the structural dynamics of a bend-twist coupled full scale section of a wind turbine blade structure. The main goal of the conducted research is to validate finite element model of the modified wind turbine blade section mounted in the flexible support structure accordingly to the experimental results. Bend-twist coupling was implemented by adding angled unidirectional layers on the suction and pressure side of the blade. Dynamic test and simulations were performed on a section of a full scale wind turbine blade provided by Vestas Wind Systems A/S. The numerical results are compared to the experimental measurements and the discrepancies are assessed by natural frequency difference and modal assurance criterion. Based on sensitivity analysis, set of model parameters was selected for the model updating process. Design of experiment and response surface method was implemented to find values of model parameters yielding results closest to the experimental. The updated finite element model is producing results more consistent with the measurement outcomes.
Rajaraman, Prathish K; Manteuffel, T A; Belohlavek, M; Heys, Jeffrey J
2017-01-01
A new approach has been developed for combining and enhancing the results from an existing computational fluid dynamics model with experimental data using the weighted least-squares finite element method (WLSFEM). Development of the approach was motivated by the existence of both limited experimental blood velocity in the left ventricle and inexact numerical models of the same flow. Limitations of the experimental data include measurement noise and having data only along a two-dimensional plane. Most numerical modeling approaches do not provide the flexibility to assimilate noisy experimental data. We previously developed an approach that could assimilate experimental data into the process of numerically solving the Navier-Stokes equations, but the approach was limited because it required the use of specific finite element methods for solving all model equations and did not support alternative numerical approximation methods. The new approach presented here allows virtually any numerical method to be used for approximately solving the Navier-Stokes equations, and then the WLSFEM is used to combine the experimental data with the numerical solution of the model equations in a final step. The approach dynamically adjusts the influence of the experimental data on the numerical solution so that more accurate data are more closely matched by the final solution and less accurate data are not closely matched. The new approach is demonstrated on different test problems and provides significantly reduced computational costs compared with many previous methods for data assimilation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Modeling and finite element simulation of the magneto-mechanical behavior of ferrogels
Energy Technology Data Exchange (ETDEWEB)
Attaran, Abdolhamid, E-mail: abdolhamid.attaran@tu-dresden.de; Brummund, Jörg; Wallmersperger, Thomas
2017-06-01
In our previous study (see Ref. Attaran et al. (in press) ) we formulated a continuum model for ferrogels considering them as multicomponent materials. In the present work a reduced model for ferrogels is presented consisting only of a polymer network (P) and fixed magnetic particles (f). The reduced model is solved using the finite element method where the only degrees of freedom are mechanical displacement and magnetic potential. Elongation and contraction of a ferrogel are observed parallel and perpendicular to the applied magnetic field direction, respectively. These results are in a good qualitative agreement with experimental results. With our modeling approach, we were able to investigate (i) the influence of the magnetic field on the polymer gel containing magnetic particles and (ii) the resulting mechanical deformation of a ferrogel. - Highlights: • A reduced continuum model for ferrogels, consisting of a polymer network and fixed magnetic particles, is presented. • A coupled magneto-mechanical problem is formulated and solved numerically using the Finite Element Method in 2D. • Deformation of a ferrogel in a magnetic field for a circular gel and a strip of a ferrogel is investigated. • Elongation of the ferrogel is observed in the direction of the applied magnetic field. • Contraction of the ferrogel is observed perpendicular to the applied magnetic field.
Herkt, Sabrina
2008-01-01
This thesis shows an approach to combine the advantages of MBS tyre models and FEM models for the use in full vehicle simulations. The procedure proposed in this thesis aims to describe a nonlinear structure with a Finite Element approach combined with nonlinear model reduction methods. Unlike most model reduction methods - as the frequently used Craig-Bampton approach - the method of Proper Orthogonal Decomposition (POD) offers a projection basis suitable for nonlinear models. For the linear...
Kim, Yoon Hyuk; Wu, Mengying; Kim, Kyungsoo
2013-01-01
Osteoporosis is a disease in which low bone mass and microarchitectural deterioration of bone tissue lead to enhanced bone fragility and susceptibility to fracture. Due to the complex anatomy of the vertebral body, the difficulties associated with obtaining bones for in vitro experiments, and the limitations on the control of the experimental parameters, finite element models have been developed to analyze the biomechanical properties of the vertebral body. We developed finite element models ...
Development of a finite element model of the ligamentous cervical vertebral column of a Great Dane.
Bonelli, Marília de Albuquerque; Shah, Anoli; Goel, Vijay; Costa, Fabiano Séllos; da Costa, Ronaldo Casimiro
2018-01-29
Cervical spondylomyelopathy (CSM), also known as wobbler syndrome, affects mainly large and giant-breed dogs, causing compression of the cervical spinal cord and/or nerve roots. Structural and dynamic components seem to play a role in the development of CSM; however, pathogenesis is not yet fully understood. Finite element models have been used for years in human medicine to study the dynamic behavior of structures, but it has been mostly overlooked in veterinary studies. To our knowledge, no specific ligamentous spine models have been developed to investigate naturally occurring canine myelopathies and possible surgical treatments. The goal of this study was to develop a finite element model (FEM) of the C 2 -C 7 segment of the ligamentous cervical vertebral column of a neurologically normal Great Dane without imaging changes. The FEM of the intact C 2 -C 7 cervical vertebral column had a total of 188,906 elements (175,715 tetra elements and 12,740 hexa elements). The range of motion (in degrees) for the FEM subjected to a moment of 2Nm was approximately 27.94 in flexion, 25.86 in extension, 24.14 in left lateral bending, 25.27 in right lateral bending, 17.44 in left axial rotation, and 16.72 in right axial rotation. We constructed a ligamentous FEM of the C 2 -C 7 vertebral column of a Great Dane dog, which can serve as a platform to be modified and adapted for studies related to biomechanics of the cervical vertebral column and to further improve studies on osseous-associated cervical spondylomyelopathy. Copyright © 2018 Elsevier Ltd. All rights reserved.
A high performance finite element model for wind farm modeling in forested areas
Owen, Herbert; Avila, Matias; Folch, Arnau; Cosculluela, Luis; Prieto, Luis
2015-04-01
Wind energy has grown significantly during the past decade and is expected to continue growing in the fight against climate change. In the search for new land where the impact of the wind turbines is small several wind farms are currently being installed in forested areas. In order to optimize the distribution of the wind turbines within the wind farm the Reynolds Averaged Navier Stokes equations are solved over the domain of interest using either commercial or in house codes. The existence of a canopy alters the Atmospheric Boundary Layer wind profile close to the ground. Therefore in order to obtain a more accurate representation of the flow in forested areas modification to both the Navier Stokes and turbulence variables equations need to be introduced. Several existing canopy models have been tested in an academic problem showing that the one proposed by Sogachev et. al gives the best results. This model has been implemented in an in house CFD solver named Alya. It is a high performance unstructured finite element code that has been designed from scratch to be able to run in the world's biggest supercomputers. Its scalabililty has recently been tested up to 100000 processors in both American and European supercomputers. During the past three years the code has been tuned and tested for wind energy problems. Recent efforts have focused on the canopy model following industry needs. In this work we shall benchmark our results in a wind farm that is currently being designed by Scottish Power and Iberdrola in Scotland. This is a very interesting real case with extensive experimental data from five different masts with anemometers at several heights. It is used to benchmark both the wind profiles and the speed up obtained between different masts. Sixteen different wind directions are simulated. The numerical model provides very satisfactory results for both the masts that are affected by the canopy and those that are not influenced by it.
Mechanical Properties of Uranium Silicides by Nanoindentation and Finite Elements Modeling
Carvajal-Nunez, U.; Elbakhshwan, M. S.; Mara, N. A.; White, J. T.; Nelson, A. T.
2018-02-01
Three methods were used to measure the mechanical properties of {U}3{Si}, {U}_3{Si}2, and USi. Quasi-static and continuous stiffness measurement nanoindentation were used to determine hardness and Young's modulus, and microindentation was used to evaluate the bulk hardness. Hardness and Young's modulus of the three U-Si compounds were both observed to increase with Si content. Finally, finite elements modelling was used to validate the nanoindentation data calculated for {U}3{Si}2 and estimate its yield strength.
Finite-Element Model-Based Design Synthesis of Axial Flux PMBLDC Motors
DEFF Research Database (Denmark)
Fasil, Muhammed; Mijatovic, Nenad; Jensen, Bogi Bech
2016-01-01
This paper discusses design synthesis of a permanent magnet brushless DC (PMBLDC) machine using a finite element (FE) model. This work differentiates itself from the past studies by following a synthesis approach, in which many designs that satisfy performance criteria are considered instead...... of a unique solution. The designer can later select a design, based on comparing parameters of the designs, which are critical to the application that the motor will be used. The presented approach makes it easier to define constraints for a design synthesis problem. A detailed description of the setting up...... is demonstrated by designing a segmented axial torus PMBLDC motor for an electric two-wheeler....
A model for the structural analysis of concrete by the finite element method
International Nuclear Information System (INIS)
Pereira, A.M.; Melo Carvalho, L.A. de
1978-01-01
The non-linear effects due to cracking, crushing of the concrete and steel yielding are taken into account by means of a stress transfer process, in the finite elements that reach characteristic values for these situations. It was supposed a linear stress-strain relaitonship for the concrete to traction and a perfect elastoplastic behavior for the concrete to compression. For the steel it was supposed a perfect elasto-plastic behavior. The results obtained with the use proposed model are compared with experimental and analytical results of other works. (Author)
Accurate Finite Element Modelling of Chipboard Single-Stud Floor Panels subjected to Dynamic Loads
DEFF Research Database (Denmark)
Sjöström, A.; Flodén, O.; Persson, K.
2012-01-01
In multi-storey buildings, the use of lightweight material has many advantages. The low weight, the low energy consumption and the sustainability of the material are some attractive benefits from using lightweight materials. Compared with heavier structures i.e. concrete the challenge...... in constructing a building compliant with building codes vis-a-vis the propagation of sound and vibrations within the structure is a challenge. Focusing on junctions in a multi-storey lightweight buildings, a modular finite element model is developed to be used for analyses of vibration transmission...
Pellet Cladding Mechanical Interaction Modeling Using the Extended Finite Element Method
Energy Technology Data Exchange (ETDEWEB)
Spencer, Benjamin W.; Jiang, Wen; Dolbow, John E.; Peco, Christian
2016-09-01
As a brittle material, the ceramic UO2 used as light water reactor fuel experiences significant fracturing throughout its life, beginning with the first rise to power of fresh fuel. This has multiple effects on the thermal and mechanical response of the fuel/cladding system. One such effect that is particularly important is that when there is mechanical contact between the fuel and cladding, cracks that extending from the outer surface of the fuel into the volume of the fuel cause elevated stresses in the adjacent cladding, which can potentially lead to cladding failure. Modeling the thermal and mechanical response of the cladding in the vicinity of these surface-breaking cracks in the fuel can provide important insights into this behavior to help avoid operating conditions that could lead to cladding failure. Such modeling has traditionally been done in the context of finite-element-based fuel performance analysis by modifying the fuel mesh to introduce discrete cracks. While this approach is effective in capturing the important behavior at the fuel/cladding interface, there are multiple drawbacks to explicitly incorporating the cracks in the finite element mesh. Because the cracks are incorporated in the original mesh, the mesh must be modified for cracks of specified location and depth, so it is difficult to account for crack propagation and the formation of new cracks at other locations. The extended finite element method (XFEM) has emerged in recent years as a powerful method to represent arbitrary, evolving, discrete discontinuities within the context of the finite element method. Development work is underway by the authors to implement XFEM in the BISON fuel performance code, and this capability has previously been demonstrated in simulations of fracture propagation in ceramic nuclear fuel. These preliminary demonstrations have included only the fuel, and excluded the cladding for simplicity. This paper presents initial results of efforts to apply XFEM to
Constitutive model for shape memory alloys and its use in design and finite element analysis
Bose, Sudip; Santhanam, Sridhar
2002-07-01
A constitutive model for predicting the thermomechanical behavior of Shape Memory Alloys (SMAs) has been developed and validated. The model uses an approach similar to Brinson, Liang and Rogers, and Tanaka. It links key thermomechanical variables: stress, strain, temperature, and martensite fraction. A basic differential form for the SMA constitutive behavior, developed by Tanaka, forms the foundation of the model. The model is completed with a definition of the rules governing the behavior of martensite fraction. Like Brinson, the model distinguishes between de-twinned and twinned martensite. The phase transition temperatures are assumed to be a linear function of applied stress. The forward and reverse phase transformations are described by piecewise exponential functions. There are a number of parameters in the model that need to be determined using experimental data. The critical transformation temperatures are determined by resistivity measurements. All other parameters are determined by mechanical tension testing followed by nonlinear least-squares estimations. Mechanical testing consisted of displacement controlled, tension tests on Nitinol wires at several temperatures. The effectiveness of this model is demonstrated by its use in the design of an SMA actuated robotic arm. The constitutive model is used in conjunction with a lumped heat transfer model, a kinematic model, and a dynamic model to predict the behavior of the arm. Comparison between predictions and experimentally observed behavior is very good indicating a sound constitutive model. The model is also built into a finite element code that simulates pseudoelastic SMA behavior. The code considers geometric and material nonlinearities. The behavior of a simple pseudoelastic device is shown to be well predicted by the finite element code.
Finite element modeling of pellet-clad mechanical interaction with ABAQUS
International Nuclear Information System (INIS)
Cheon, C. S.; Lee, B. H.; Koo, Y. H.; Oh, J. Y.; Son, D. S.
2002-01-01
Pellet-clad mechanical interaction (PCMI) was modelled by an axisymmetric finite element method. Thermomechanical models of pellet and clad materials and a contact model for their interaction have been implemented in addition to the application of appropriate boundary conditions so that the FE model was configured. Temperature and displacement were evaluated through a coupled analysis using a general purposed FE code, ABAQUS. Also, a batch program has been developed to efficiently deal with a series of jobs such as making an interface with a fuel performance code, the generation of an input deck for ABAQUS code and its execution, and an interpretation of the output. Under various conditions, results from the present FE model were analyzed. Preliminary verification was conducted by comparing the clad elongation measured during an in-pile PCMI experiment with that calculated by means of the developed FE model
Finite element analysis and modeling of temperature distribution in turning of titanium alloys
Directory of Open Access Journals (Sweden)
Moola Mohan Reddy
2018-04-01
Full Text Available The titanium alloys (Ti-6Al-4V have been widely used in aerospace, and medical applications and the demand is ever-growing due to its outstanding properties. In this paper, the finite element modeling on machinability of Ti-6Al-4V using cubic boron nitride and polycrystalline diamond tool in dry turning environment was investigated. This research was carried out to generate mathematical models at 95% confidence level for cutting force and temperature distribution regarding cutting speed, feed rate and depth of cut. The Box-Behnken design of experiment was used as Response Surface Model to generate combinations of cutting variables for modeling. Then, finite element simulation was performed using AdvantEdge®. The influence of each cutting parameters on the cutting responses was investigated using Analysis of Variance. The analysis shows that depth of cut is the most influential parameter on resultant cutting force whereas feed rate is the most influential parameter on cutting temperature. Also, the effect of the cutting-edge radius was investigated for both tools. This research would help to maximize the tool life and to improve surface finish.
Finite Element Based Physical Chemical Modeling of Corrosion in Magnesium Alloys
Directory of Open Access Journals (Sweden)
Venkatesh Vijayaraghavan
2017-03-01
Full Text Available Magnesium alloys have found widespread applications in diverse fields such as aerospace, automotive, bio-medical and electronics industries due to its relatively high strength-to-weight ratio. However, stress corrosion cracking of these alloys severely restricts their applications in several novel technologies. Hence, it will be useful to identify the corrosion mechanics of magnesium alloys under external stresses as it can provide further insights on design of these alloys for critical applications. In the present study, the corrosion mechanics of a commonly used magnesium alloy, AZ31, is studied using finite element simulation with a modified constitutive material damage model. The data obtained from the finite element modeling were further used to formulate a mathematical model using computational intelligence algorithm. Sensitivity and parametric analysis of the derived model further corroborated the mechanical response of the alloy in line with the corrosion physics. The proposed approach is anticipated to be useful for materials engineers for optimizing the design criteria for magnesium alloys catered for high temperature applications.
Energy Technology Data Exchange (ETDEWEB)
Soulami, Ayoub [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Paxton, Dean M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burkes, Douglas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2014-04-23
Pacific Northwest National Laboratory (PNNL) has been investigating manufacturing processes for the uranium-10% molybdenum (U-10Mo) alloy plate-type fuel for the U.S. high-performance research reactors. This work supports the Convert Program of the U.S. Department of Energy’s National Nuclear Security Administration (DOE/NNSA) Global Threat Reduction Initiative. This report documents modeling results of PNNL’s efforts to perform finite-element simulations to predict roll separating forces and rolling defects. Simulations were performed using a finite-element model developed using the commercial code LS-Dyna. Simulations of the hot rolling of U-10Mo coupons encapsulated in low-carbon steel have been conducted following two different schedules. Model predictions of the roll-separation force and roll-pack thicknesses at different stages of the rolling process were compared with experimental measurements. This report discusses various attributes of the rolled coupons revealed by the model (e.g., dog-boning and thickness non-uniformity).
Finite-Element Software for Conceptual Design
DEFF Research Database (Denmark)
Lindemann, J.; Sandberg, G.; Damkilde, Lars
2010-01-01
and research. Forcepad is an effort to provide a conceptual design and teaching tool in a finite-element software package. Forcepad is a two-dimensional finite-element application based on the same conceptual model as image editing applications such as Adobe Photoshop or Microsoft Paint. Instead of using...
Finite Element Model for Nonlinear Analysis of Reinforced Concrete Beams and Plane Frames
Directory of Open Access Journals (Sweden)
R.S.B. STRAMANDINOLI
Full Text Available Abstract In this work, a two-dimensional finite element (FE model for physical and geometric nonlinear analysis of reinforced concrete beams and plane frames, developed by the authors, is presented. The FE model is based on the Euler-Bernoulli Beam Theory, in which shear deformations are neglected. The bar elements have three nodes with a total of seven degrees of freedom. Three Gauss-points are utilized for the element integration, with the element section discretized into layers at each Gauss point (Fiber Model. It is assumed that concrete and reinforcing bars are perfectly bonded, and each section layer is assumed to be under a uniaxial stress-state. Nonlinear constitutive laws are utilized for both concrete and reinforcing steel layers, and a refined tension-stiffening model, developed by the authors, is included. The Total Lagrangean Formulation is adopted for geometric nonlinear consideration and several methods can be utilized to achieve equilibrium convergence of the nonlinear equations. The developed model is implemented into a computer program named ANEST/CA, which is validated by comparison with some tests on RC beams and plane frames, showing an excellent correlation between numerical and experimental results.
Solution of Finite Element Equations
DEFF Research Database (Denmark)
Krenk, Steen
An important step in solving any problem by the finite element method is the solution of the global equations. Numerical solution of linear equations is a subject covered in most courses in numerical analysis. However, the equations encountered in most finite element applications have some special...... features that justify the development of specialized solution algorithms....
Three-dimensional Finite Element Modelling of Composite Slabs for High Speed Rails
Mlilo, Nhlanganiso; Kaewunruen, Sakdirat
2017-12-01
Currently precast steel-concrete composite slabs are being considered on railway bridges as a viable alternative replacement for timber sleepers. However, due to their nature and the loading conditions, their behaviour is often complex. Present knowledge of the behaviour of precast steel-concrete composite slabs subjected to rail loading is limited. FEA is an important tool used to simulate real life behaviour and is widely accepted in many disciples of engineering as an alternative to experimental test methods, which are often costly and time consuming. This paper seeks to detail FEM of precast steel-concrete slabs subjected to standard in-service loading in high-speed rail with focus on the importance of accurately defining material properties, element type, mesh size, contacts, interactions and boundary conditions that will give results representative of real life behaviour. Initial finite element model show very good results, confirming the accuracy of the modelling procedure
Three-dimensional dynamic response modeling of floating nuclear plants using finite element methods
International Nuclear Information System (INIS)
Johnson, H.W.; Vaish, A.K.; Porter, F.L.; McGeorge, R.
1976-01-01
A modelling technique which can be used to obtain the dynamic response of a floating nuclear plant (FNP) moored in an artificial basin is presented. Hydrodynamic effects of the seawater in the basin have a significant impact on the response of the FNP and must be included. A three-dimensional model of the platform and mooring system (using beam elements) is used, with the hydrodynamic effects represented by added mass and damping. For an essentially square plant in close proximity to the site structures, the three-dimensional nature of the basin must be considered in evaluating the added mass and damping. However, direct solutions for hydrodynamic effects with complex basin geometry are not, as yet, available. A method for estimating these effects from planar finite element analysis is developed. (Auth.)
Massively Parallel Finite Element Programming
Heister, Timo
2010-01-01
Today\\'s large finite element simulations require parallel algorithms to scale on clusters with thousands or tens of thousands of processor cores. We present data structures and algorithms to take advantage of the power of high performance computers in generic finite element codes. Existing generic finite element libraries often restrict the parallelization to parallel linear algebra routines. This is a limiting factor when solving on more than a few hundreds of cores. We describe routines for distributed storage of all major components coupled with efficient, scalable algorithms. We give an overview of our effort to enable the modern and generic finite element library deal.II to take advantage of the power of large clusters. In particular, we describe the construction of a distributed mesh and develop algorithms to fully parallelize the finite element calculation. Numerical results demonstrate good scalability. © 2010 Springer-Verlag.
Development, Validation and Parametric study of a 3-Year-Old Child Head Finite Element Model
Cui, Shihai; Chen, Yue; Li, Haiyan; Ruan, ShiJie
2015-12-01
Traumatic brain injury caused by drop and traffic accidents is an important reason for children's death and disability. Recently, the computer finite element (FE) head model has been developed to investigate brain injury mechanism and biomechanical responses. Based on CT data of a healthy 3-year-old child head, the FE head model with detailed anatomical structure was developed. The deep brain structures such as white matter, gray matter, cerebral ventricle, hippocampus, were firstly created in this FE model. The FE model was validated by comparing the simulation results with that of cadaver experiments based on reconstructing the child and adult cadaver experiments. In addition, the effects of skull stiffness on the child head dynamic responses were further investigated. All the simulation results confirmed the good biofidelity of the FE model.
Distributed parameter and finite element models for wave propagation in railway contact lines
Sorrentino, S.; Anastasio, D.; Fasana, A.; Marchesiello, S.
2017-12-01
A distributed parameter model of a railway two-level catenary system is presented for the analysis of the coupled wave dynamics. The wires are modelled as two straight axis parallel beams, with linear equilibrium equations, and the moving load applied by the pantograph is modelled as a constant concentrated travelling force. The general solution is sought by an application of the Ritz-Galerkin method, and then compared with direct time integrations of a finite element model (FEM), achieved by two different integration schemes. The proposed model provides a valid reference for appropriately selecting the FEM parameters, in order to reduce the errors due to spurious modes, affecting the numerical integrations especially at high speeds of the moving pantograph.
Finite Element Modeling of the Inertia Friction Welding of Dissimilar High-Strength Steels
Bennett, C. J.; Attallah, M. M.; Preuss, M.; Shipway, P. H.; Hyde, T. H.; Bray, S.
2013-11-01
Finite element (FE) process modeling of inertia friction welding between dissimilar high-strength steels, AerMet® 100 and SCMV, has been carried out using the DEFORM™-2D (v10.0) software. This model was validated against experimental data collected for a test weld performed between the materials; this included process data such as upset and rotational velocities as well as thermal data collected during the process using embedded thermocouples. The as-welded hoop residual stress from the FE model was also compared with experimental measurements taken on the welded component using synchrotron X-ray and neutron diffraction techniques. The modeling work considered the solid-state phase transformations which occur in the steels, and the trends in the residual stress data were well replicated by the model.
Non-linear rotation-free shell finite-element models for aortic heart valves.
Gilmanov, Anvar; Stolarski, Henryk; Sotiropoulos, Fotis
2017-01-04
Hyperelastic material models have been incorporated in the rotation-free, large deformation, shell finite element (FE) formulation of (Stolarski et al., 2013) and applied to dynamic simulations of aortic heart valve. Two models used in the past in analysis of such problem i.e. the Saint-Venant and May-Newmann-Yin (MNY) material models have been considered and compared. Uniaxial tests for those constitutive equations were performed to verify the formulation and implementation of the models. The issue of leaflets interactions during the closing of the heart valve at the end of systole is considered. The critical role of using non-linear anisotropic model for proper dynamic response of the heart valve especially during the closing phase is demonstrated quantitatively. This work contributes an efficient FE framework for simulating biological tissues and paves the way for high-fidelity flow structure interaction simulations of native and bioprosthetic aortic heart valves. Copyright © 2016. Published by Elsevier Ltd.
Directory of Open Access Journals (Sweden)
Ibrahim Dauda Muhammad
2015-01-01
Full Text Available The single-walled zirconia nanotube is structurally modeled and its Young’s modulus is valued by using the finite element approach. The nanotube was assumed to be a frame-like structure with bonds between atoms regarded as beam elements. The properties of the beam required for input into the finite element analysis were computed by connecting energy equivalence between molecular and continuum mechanics. Simulation was conducted by applying axial tensile strain on one end of the nanotube while the other end was fixed and the corresponding reaction force recorded to compute Young’s modulus. It was found out that Young’s modulus of zirconia nanotubes is significantly affected by some geometrical parameters such as chirality, diameter, thickness, and length. The obtained values of Young’s modulus for a certain range of diameters are in agreement with what was obtained in the few experiments that have been conducted so far. This study was conducted on the cubic phase of zirconia having armchair and zigzag configuration. The optimal diameter and thickness were obtained, which will assist in designing and fabricating bulk nanostructured components containing zirconia nanotubes for various applications.
International Nuclear Information System (INIS)
Muto, K.; Motosaka, M.; Kamata, M.; Masuda, K.; Urao, K.; Mameda, T.
1985-01-01
In order to investigate the 3-dimensional earthquake response characteristics of an embedded structure with consideration for soil-structure interaction, the authors have developed an analytical method using 3-dimensional hybrid model of boundary elements (BEM) and finite elements (FEM) and have conducted a dynamic analysis of an actual nuclear reactor building. This paper describes a comparative study between two different embedment depths in soil as elastic half-space. As the results, it was found that the earthquake response intensity decreases with the increase of the embedment depth and that this method was confirmed to be effective for investigating the 3-D response characteristics of embedded structures such as deflection pattern of each floor level, floor response spectra in high frequency range. (orig.)
The finite element modeling and thermal analysis of the special focal plane of LAMOST
Zuo, Heng; Yang, Dehua; Li, Guoping
2010-07-01
The Large Area Multi-Object Spectroscopic Telescope (LAMOST) is a meridian reflecting Schmidt telescope with a 40m optical axis between the reflecting Schmidt plate and the spherical primary mirror. In the middle is located the spherical focal plane, through which there are corresponding 4000+ unit mounting holes for the fibers, and on its back, there attached a support truss adapted from Serrurier concept. The mechanical stabilization of the focal plane system naturally has magnificent impact on the observation efficiency of the LAMOST. A comprehensive Finite Element Model of the focal plane system has been built to evaluate thermally induced degradation of its mechanical accuracy using the nodal modification technique within ANSYS, and diverse temperature load cases have been considered on the Finite Element model and related thermal analyses have been carried out to investigate thermal deformation of the focal plane. Subsequently the calculated deflection of the working surface has been extracted and reconstructed with least square fitting in MATLAB. The results show that temperature change around the telescope has little effect on the performance of the focal plane within temperature variation requirements of the LAMOST. The methods of modeling and analyzing used in this research are informative for future large telescope projects.
Kit Wong, Ching; Wu, Patrick
2017-04-01
Wu (2004) developed a transformation scheme to model viscoelatic deformation due to glacial loading by commercial finite element package - ABAQUS. Benchmark tests confirmed that this method works extremely well on incompressible earth model. Bangtsson & Lund (2008),however, showed that the transformation scheme would lead to incorrect results if compressible material parameters are used. Their study implies that Wu's method of stress transformation is inadequate to model the load induced deformation of a compressible earth under the framework of ABAQUS. In light of this, numerical experiments are carried out to find if there exist other methods that serve this purpose. All the tested methods are not satisfying as the results failed to converge through iterations, except at the elastic limit. Those tested methods will be outlined and the results will be presented. Possible reasons of failure will also be discussed. Bängtsson, E., & Lund, B. (2008). A comparison between two solution techniques to solve the equations of glacially induced deformation of an elastic Earth. International journal for numerical methods in engineering, 75(4), 479-502. Wu, P. (2004). Using commercial finite element packages for the study of earth deformations, sea levels and the state of stress. Geophysical Journal International, 158(2), 401-408.
Analysis of crack propagation in human long bone by using finite element modeling
Salim, Mohammad Shahril; Salleh, Ahmad Faizal; Daud, Ruslizam
2017-12-01
The aim of this research is to present a numerical modeling of crack for human long bone specifically on femur shaft bone under mode I loading condition. Two - dimensional model (2D) of long bone was developed based on past research study. The finite element analysis and construction of the model are done using Mechanical APDL (ANSYS) v14.0 software. The research was conducted mainly based on two conditions that were at different crack lengths and different loading forces for male and female. In order to evaluate the stress intensity factor (KI) of the femur shaft of long bone, this research employed finite element method to predict the brittle fracture loading by using three-point bending test. The result of numerical test found that the crack was formed when the crack length reached 0.0022 m where KI values are proportional with the crack's length. Also, various loading forces in range of 400 N to 1000 N were applied in an attempt to study their effect on stress intensity factor and it was found that the female dimension has higher KI values compared to male. It was also observed that K values found by this method have good agreement with theoretical results based on previous research.
Finite element modelling of Plantar Fascia response during running on different surface types
Razak, A. H. A.; Basaruddin, K. S.; Salleh, A. F.; Rusli, W. M. R.; Hashim, M. S. M.; Daud, R.
2017-10-01
Plantar fascia is a ligament found in human foot structure located beneath the skin of human foot that functioning to stabilize longitudinal arch of human foot during standing and normal gait. To perform direct experiment on plantar fascia seems very difficult since the structure located underneath the soft tissue. The aim of this study is to develop a finite element (FE) model of foot with plantar fascia and investigate the effect of the surface hardness on biomechanical response of plantar fascia during running. The plantar fascia model was developed using Solidworks 2015 according to the bone structure of foot model that was obtained from Turbosquid database. Boundary conditions were set out based on the data obtained from experiment of ground reaction force response during running on different surface hardness. The finite element analysis was performed using Ansys 14. The results found that the peak of stress and strain distribution were occur on the insertion of plantar fascia to bone especially on calcaneal area. Plantar fascia became stiffer with increment of Young’s modulus value and was able to resist more loads. Strain of plantar fascia was decreased when Young’s modulus increased with the same amount of loading.
Xiao, Tiaojie; Liu, Yun; Wang, Yun; Fu, Li-Yun
2018-02-01
It is important to understand how magnetotelluric (MT) modeling can most effectively be performed in general anisotropic media. However, previous studies in this area have mainly focused on the use of one-dimensional (1D) and two-dimensional (2D) algorithms. Thus, building on earlier work, it is important to study the performance of three-dimensional (3D) modeling in arbitrary conductivity media; therefore, an edge-based finite element (FE) method has been developed for 3D MT modeling in arbitrary conductivity media. This approach is based on the initial derivation of a series of equivalent variational equations that are based on Maxwell equations, generated using the weighted residual method. Specific values were then obtained for coefficient matrixes of this edge-based FE method using hexahedral meshes, and the algorithm was verified by comparing its results with finite difference (FD) solutions generated using a 2D anisotropic model. Finally, the results of a 3D anisotropic model were analyzed detailed for three conditions; another 3D anisotropic model was designed and its results were compared with two isotropic models'.
International Nuclear Information System (INIS)
Viswanathan, H.S.
1996-08-01
The finite element code FEHMN, developed by scientists at Los Alamos National Laboratory (LANL), is a three-dimensional finite element heat and mass transport simulator that can handle complex stratigraphy and nonlinear processes such as vadose zone flow, heat flow and solute transport. Scientists at LANL have been developing hydrologic flow and transport models of the Yucca Mountain site using FEHMN. Previous FEHMN simulations have used an equivalent Kd model to model solute transport. In this thesis, FEHMN is modified making it possible to simulate the transport of a species with a rigorous chemical model. Including the rigorous chemical equations into FEHMN simulations should provide for more representative transport models for highly reactive chemical species. A fully kinetic formulation is chosen for the FEHMN reactive transport model. Several methods are available to computationally implement a fully kinetic formulation. Different numerical algorithms are investigated in order to optimize computational efficiency and memory requirements of the reactive transport model. The best algorithm of those investigated is then incorporated into FEHMN. The algorithm chosen requires for the user to place strongly coupled species into groups which are then solved for simultaneously using FEHMN. The complete reactive transport model is verified over a wide variety of problems and is shown to be working properly. The new chemical capabilities of FEHMN are illustrated by using Los Alamos National Laboratory's site scale model of Yucca Mountain to model two-dimensional, vadose zone 14 C transport. The simulations demonstrate that gas flow and carbonate chemistry can significantly affect 14 C transport at Yucca Mountain. The simulations also prove that the new capabilities of FEHMN can be used to refine and buttress already existing Yucca Mountain radionuclide transport studies
Finite Element Models for Electron Beam Freeform Fabrication Process, Phase II
National Aeronautics and Space Administration — This Small Business Innovation Research Phase II proposal offers to develop a comprehensive computer simulation methodology based on the finite element method for...
Finite Element Modeling and Optimization of Tube-Shaped Ultrasonic Motors
National Research Council Canada - National Science Library
Bouchilloux, P
2003-01-01
.... Then, we show how the finite element method (ATILA) can be used, in combination with genetic optimization procedures, to design tube-shaped motors in various dimensions and for different performance objectives. Several design examples are presented and discussed.
Detailed finite element method modeling of evaporating multi-component droplets
Energy Technology Data Exchange (ETDEWEB)
Diddens, Christian, E-mail: C.Diddens@tue.nl
2017-07-01
The evaporation of sessile multi-component droplets is modeled with an axisymmetic finite element method. The model comprises the coupled processes of mixture evaporation, multi-component flow with composition-dependent fluid properties and thermal effects. Based on representative examples of water–glycerol and water–ethanol droplets, regular and chaotic examples of solutal Marangoni flows are discussed. Furthermore, the relevance of the substrate thickness for the evaporative cooling of volatile binary mixture droplets is pointed out. It is shown how the evaporation of the more volatile component can drastically decrease the interface temperature, so that ambient vapor of the less volatile component condenses on the droplet. Finally, results of this model are compared with corresponding results of a lubrication theory model, showing that the application of lubrication theory can cause considerable errors even for moderate contact angles of 40°. - Graphical abstract:.
Application of equivalent medium parameters in finite element models of microwave metamaterials
Hewitt, C.; Alves, F.; Luscombe, J.; Grbovic, D.
2018-03-01
Simulated or experimentally measured reflection and transmission are used to obtain effective permittivity (ɛ), permeability (μ), and conductivity (σ) for a planar microwave metamaterial. These parameters are then used in a finite element model of macro-scale metamaterial objects, where the metamaterial is taken to be a homogeneous layer with frequency-dependent ɛ, μ, and σ. We demonstrate good agreement between reflection and absorption of metamaterial structure and those obtained from modeling homogenized, macro-scale metamaterials. We further demonstrate use of the method for geometrically scaled, oddly shaped macroscopic objects. This method significantly reduces computation requirements and enables modeling of metamaterial-made, large area objects without modeling their actual intricate metamaterial structure.
Finite element modeling of the radiative properties of Morpho butterfly wing scales.
Mejdoubi, A; Andraud, C; Berthier, S; Lafait, J; Boulenguez, J; Richalot, E
2013-02-01
With the aim of furthering the explanation of iridescence in Morpho butterflies, we developed an optical model based on the finite-element (FE) method, taking more accurately into account the exact morphology of the wing, origin of iridescence. We modeled the photonic structure of a basal scale of the Morpho rhetenor wing as a three-dimensional object, infinite in one direction, with a shape copied from a TEM image, and made out of a slightly absorbing dielectric material. Periodic boundary conditions were used in the FE method to model the wing periodic structure and perfectly matched layers permitted the free-space scattering computation. Our results are twofold: first, we verified on a simpler structure, that our model yields the same result as the rigorous coupled wave analysis (RCWA), and second, we demonstrated that it is necessary to assume an absorption gradient in the true structure, to account for experimental reflectivity measured on a real wing.
Two-dimensional finite elements model for selenium transport in saturated and unsaturated zones.
Tayfur, Gokmen; Tanji, Kenneth K; Baba, Alper
2010-10-01
A two-dimensional finite element model was developed to simulate species of selenium transport in two dimensions in both saturated and unsaturated soil zones. The model considers water, selenate, selenite, and selenomethionine uptake by plants. It also considers adsorption and desorption, oxidation and reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. In addition to simulating water flow, selenate, selenite, and selenomethionine transport, the model also simulates organic and gaseous selenium transport. The developed model was applied to simulate two different observed field data. The simulation of the observed data was satisfactory, with mean absolute error of 48.5 microg/l and mean relative error of 8.9%.
DEFF Research Database (Denmark)
Stamatelos, Dimtrios; Kappatos, Vassilios
2017-01-01
Purpose – This paper presents the development of an advanced structural assessment approach for aerospace components (metallic and composites). This work focuses on developing an automatic image processing methodology based on Non Destructive Testing (NDT) data and numerical models, for predicting...... the residual strength of these components. Design/methodology/approach – An image processing algorithm, based on the threshold method, has been developed to process and quantify the geometric characteristics of damages. Then, a parametric Finite Element (FE) model of the damaged component is developed based...... on the inputs acquired from the image processing algorithm. The analysis of the metallic structures is employing the Extended FE Method (XFEM), while for the composite structures the Cohesive Zone Model (CZM) technique with Progressive Damage Modelling (PDM) is used. Findings – The numerical analyses...
Multigrid Methods for A Mixed Finite Element Method of The Darcy-Forchheimer Model.
Huang, Jian; Chen, Long; Rui, Hongxing
2018-01-01
An efficient nonlinear multigrid method for a mixed finite element method of the Darcy-Forchheimer model is constructed in this paper. A Peaceman-Rachford type iteration is used as a smoother to decouple the nonlinearity from the divergence constraint. The nonlinear equation can be solved element-wise with a closed formulae. The linear saddle point system for the constraint is reduced into a symmetric positive definite system of Poisson type. Furthermore an empirical choice of the parameter used in the splitting is proposed and the resulting multigrid method is robust to the so-called Forchheimer number which controls the strength of the nonlinearity. By comparing the number of iterations and CPU time of different solvers in several numerical experiments, our multigrid method is shown to convergent with a rate independent of the mesh size and the Forchheimer number and with a nearly linear computational cost.
Combining Laser Microsurgery and Finite Element Modeling to Assess Cell-Level Epithelial Mechanics
Hutson, M. Shane; Veldhuis, J.; Ma, Xiaoyan; Lynch, Holley E.; Cranston, P. Graham; Brodland, G. Wayne
2009-01-01
Abstract Laser microsurgery and finite element modeling are used to determine the cell-level mechanics of the amnioserosa—a morphogenetically crucial epithelium on the dorsal surface of fruit fly embryos (Drosophila melanogaster). In the experiments, a tightly focused laser ablates a subcellular hole (1 μm in diameter) that passes clean through the epithelium. The surrounding cells recoil from the wound site with a large range of initial recoil velocities. These depend on the embryo's developmental stage and the subcellular wound site. The initial recoil (up to 0.1 s) is well reproduced by a base finite element model, which assumes a uniform effective viscosity inside the cells, a constant tension along each cell-cell boundary, and a large, potentially anisotropic, far-field stress—one that far exceeds the stress equivalent of the cell-edge tensions. After 0.1 s, the experimental recoils slow dramatically. This observation can be reproduced by adding viscoelastic rods along cell edges or as a fine prestressed mesh parallel to the apical and basal membranes of the cell. The mesh also reproduces a number of double-wounding experiments in which successive holes are drilled in a single cell. PMID:20006944
Directory of Open Access Journals (Sweden)
James Sae Siew
2015-01-01
Full Text Available Rail turnouts are built to enable flexibility in the rail network as they allow for vehicles to switch between various tracks, therefore maximizing the utilisation of existing rail infrastructure. In general, railway turnouts are a safety-critical and expensive feature to a rail system as they suffer aggressive operational loads, in comparison to a plain rail track, and thus require frequent monitoring and maintenance. In practice, great consideration is given to the dynamic interaction between the turnouts components as a failed component may have adverse effects on the performance of neighbouring components. This paper presents a nonlinear 3D finite element (FE model, taking into account the nonlinearities of materials, in order to evaluate the interaction and behaviour of turnout components. Using ABAQUS, the finite element model was developed to simulate standard concrete bearers with 60 kg/m rail and with a tangential turnout radius of 250 m. The turnout structure is supported by a ballast layer, which is represented by a nonlinearly deformable tensionless solid. The numerical studies firstly demonstrate the importance of load transfer mechanisms in the failure modes of the turnout components. The outcome will lead to a better design and maintenance of railway turnouts, improving public safety and operational reliability.
Finite-Element Modeling of Viscoelastic Cells During High-Frequency Cyclic Strain
Directory of Open Access Journals (Sweden)
David W. Holdsworth
2012-03-01
Full Text Available Mechanotransduction refers to the mechanisms by which cells sense and respond to local loads and forces. The process of mechanotransduction plays an important role both in maintaining tissue viability and in remodeling to repair damage; moreover, it may be involved in the initiation and progression of diseases such as osteoarthritis and osteoporosis. An understanding of the mechanisms by which cells respond to surrounding tissue matrices or artificial biomaterials is crucial in regenerative medicine and in influencing cellular differentiation. Recent studies have shown that some cells may be most sensitive to low-amplitude, high-frequency (i.e., 1–100 Hz mechanical stimulation. Advances in finite-element modeling have made it possible to simulate high-frequency mechanical loading of cells. We have developed a viscoelastic finite-element model of an osteoblastic cell (including cytoskeletal actin stress fibers, attached to an elastomeric membrane undergoing cyclic isotropic radial strain with a peak value of 1,000 µstrain. The results indicate that cells experience significant stress and strain amplification when undergoing high-frequency strain, with peak values of cytoplasmic strain five times higher at 45 Hz than at 1 Hz, and peak Von Mises stress in the nucleus increased by a factor of two. Focal stress and strain amplification in cells undergoing high-frequency mechanical stimulation may play an important role in mechanotransduction.
Microstructural characterization and finite element modeling of AZ31 magnesium alloys welded joints
Directory of Open Access Journals (Sweden)
José A. Segarra
2018-03-01
Full Text Available In this article, it has been studied how the microstructure of AZ31 magnesium alloy can be affected by the thermic cycles produced by welding processes, trying to modeling by element finite software the thermic cycles in this material. The AZ31 samples tested were welded using Gas Tugsten Arc Welding (GTAW and different filler materials. For this investigation, optic microscopy, scanning electronic microscopy, and finite elements method software has been used. This work indicates in one hand that in this type of alloys the microconstituyentes are Al-Mn o Al-Mn-Mg compounds, the presence of β-phase cannot be found at room temperature in this research at room, on the other hand the obtained simulation models indicate that the recrystallization takes place in the areas which reach maximum temperatures around 550 °C, this value is also the limit of the dissolution area for the Al-Mn o Al-Mn-Mg precipitated particles which are very likely to act as inhibitors of the corrosion in NaCl electrolytes.
A Finite Element Model of a MEMS-based Surface Acoustic Wave Hydrogen Sensor
Directory of Open Access Journals (Sweden)
Walied A. Moussa
2010-02-01
Full Text Available Hydrogen plays a significant role in various industrial applications, but careful handling and continuous monitoring are crucial since it is explosive when mixed with air. Surface Acoustic Wave (SAW sensors provide desirable characteristics for hydrogen detection due to their small size, low fabrication cost, ease of integration and high sensitivity. In this paper a finite element model of a Surface Acoustic Wave sensor is developed using ANSYS12© and tested for hydrogen detection. The sensor consists of a YZ-lithium niobate substrate with interdigital electrodes (IDT patterned on the surface. A thin palladium (Pd film is added on the surface of the sensor due to its high affinity for hydrogen. With increased hydrogen absorption the palladium hydride structure undergoes a phase change due to the formation of the β-phase, which deteriorates the crystal structure. Therefore with increasing hydrogen concentration the stiffness and the density are significantly reduced. The values of the modulus of elasticity and the density at different hydrogen concentrations in palladium are utilized in the finite element model to determine the corresponding SAW sensor response. Results indicate that with increasing the hydrogen concentration the wave velocity decreases and the attenuation of the wave is reduced.
Parallel Computation of Flow in Heterogeneous Media Modelled by Mixed Finite Elements
Cliffe, K. A.; Graham, I. G.; Scheichl, R.; Stals, L.
2000-11-01
In this paper we describe a fast parallel method for solving highly ill-conditioned saddle-point systems arising from mixed finite element simulations of stochastic partial differential equations (PDEs) modelling flow in heterogeneous media. Each realisation of these stochastic PDEs requires the solution of the linear first-order velocity-pressure system comprising Darcy's law coupled with an incompressibility constraint. The chief difficulty is that the permeability may be highly variable, especially when the statistical model has a large variance and a small correlation length. For reasonable accuracy, the discretisation has to be extremely fine. We solve these problems by first reducing the saddle-point formulation to a symmetric positive definite (SPD) problem using a suitable basis for the space of divergence-free velocities. The reduced problem is solved using parallel conjugate gradients preconditioned with an algebraically determined additive Schwarz domain decomposition preconditioner. The result is a solver which exhibits a good degree of robustness with respect to the mesh size as well as to the variance and to physically relevant values of the correlation length of the underlying permeability field. Numerical experiments exhibit almost optimal levels of parallel efficiency. The domain decomposition solver (DOUG, http://www.maths.bath.ac.uk/~parsoft) used here not only is applicable to this problem but can be used to solve general unstructured finite element systems on a wide range of parallel architectures.
Wilson, Cian R.; Spiegelman, Marc; van Keken, Peter E.
2017-02-01
We introduce and describe a new software infrastructure TerraFERMA, the Transparent Finite Element Rapid Model Assembler, for the rapid and reproducible description and solution of coupled multiphysics problems. The design of TerraFERMA is driven by two computational needs in Earth sciences. The first is the need for increased flexibility in both problem description and solution strategies for coupled problems where small changes in model assumptions can lead to dramatic changes in physical behavior. The second is the need for software and models that are more transparent so that results can be verified, reproduced, and modified in a manner such that the best ideas in computation and Earth science can be more easily shared and reused. TerraFERMA leverages three advanced open-source libraries for scientific computation that provide high-level problem description (FEniCS), composable solvers for coupled multiphysics problems (PETSc), and an options handling system (SPuD) that allows the hierarchical management of all model options. TerraFERMA integrates these libraries into an interface that organizes the scientific and computational choices required in a model into a single options file from which a custom compiled application is generated and run. Because all models share the same infrastructure, models become more reusable and reproducible, while still permitting the individual researcher considerable latitude in model construction. TerraFERMA solves partial differential equations using the finite element method. It is particularly well suited for nonlinear problems with complex coupling between components. TerraFERMA is open-source and available at http://terraferma.github.io, which includes links to documentation and example input files.
International Nuclear Information System (INIS)
Fuller, K.N.G.; Gough, J.; Ahmadi, H.R.
1993-01-01
The International Atomic Energy Agency has initiated a co-ordinated research programme on implementation of base-isolation for nuclear structures. This paper discusses two areas relevant to modelling elastomeric base-isolators. These are the use of simplified models to predict the response of isolated structures to earthquake inputs and finite element analysis for calculating the stress distributions within the isolators. In the former, a curvilinear hysteretic model of the high damping natural rubber able to accommodate the stiffening of the rubber at large shear deflections is presented. Its predictions of structural accelerations and bearing displacement produced by design earthquakes and those above the design level are compared with those using a linear spring and dashpot model. A comparison has been made between two finite element analyses using MARC and ABAQUS of the force-deformation behaviour of a single disc of rubber bonded on both sides. The disc was loaded both in compression and shear. Two forms of strain energy functions were used namely Mooney-RivIin and Ogden. The agreement between MARC and ABAQUS for the Mooney-Rivlin model for the material was very good. This was not however the case for the Ogden model and a difference of 25% in the maximum vertical deflection of the disc under 200kN load was observed. The need for a 'benchmark' problem is identified. This could be used to establish the accuracy of the finite element solvers. A problem based on the work of Rivlin on the force-deformation behaviour of cylinder of rubber under torsion is nominated. An appraisal of strain energy functions based on Mooney-RivIin formulations is carried out. It is shown that even for a five term series the strain energy function is incapable of catering for the rapid change of modulus at small strains both for simple and pure shear modes of deformation. This function models tension/compression data much better. The work identifies the need for evaluating other forms
Using a finite element pediatric hip model in clinical 2 evaluation - a feasibility study
DEFF Research Database (Denmark)
Skytte, T. L.; Mikkelsen, Lars Pilgaard; Sonne-Holm, Stig
2017-01-01
to calculate the resulting stress in the normal direction. At a load of 233% BW the model predicted peak pressures in the hip joint of 9.7-13.8 MPa and an area in contact of 351-405 mm2. Experimental validation using the hip joint of a child was not ethical viable. Instead, our results were compared......The paper describe a method to construct a finite element model of the hip joint of a child based on clinical recorded CT data. A model which can be used for diagnostic aid and pre-operative surgical evaluation. First part of this development is a feasibility study of this method. A scan...
The Development of Finite Element Model for Pellet-Cladding Mechanical Interaction
International Nuclear Information System (INIS)
Lee, Jin-Seok; Yoo, Jong-Sung; Kim, Hyeong-Koo; Kim, Yong-Hwan; Lee, Chong-Chul; Mitchell, D.; Aleshin, Y.
2007-01-01
This paper studies a FEA(Finite Element Analysis) model to describe PCMI under a power ramp and pressure loading conditions. From this PCMI model, the stress fields of pellet and cladding are evaluated. In order to compute the stress and strain fields in the cladding which were failed under the power ramp, this model might be extended to include the missing chip shape which occurred in the process of assembling or manufacturing of fuel rod. This missing chip of pellet has an affects on the temperature and the stress of the cladding in the vicinity of the chip edge so that the possibility of fuel failure is increased during the power ramp. The pellet fragmentation can be also accounted because the fuel cracking occurs immediately after reactor start-up and plays an important role in relaxing stresses in pellet but escalating the stress in cladding
Numerical simulation of potato slices drying using a two-dimensional finite element model
Directory of Open Access Journals (Sweden)
Beigi Mohsen
2017-01-01
Full Text Available An experimental and numerical study was conducted to investigate the process of potato slices drying. For simulating the moisture transfer in the samples and predict the dehydration curves, a two-dimensional finite element model was developed and programmed in Compaq Visual Fortran, version 6.5. The model solved the Fick’s second law for slab in a shrinkage system to calculate the unsteady two-dimensional moisture transmission in rectangular coordinates (x,y. Moisture diffusivity and moisture transfer coefficient were determined by minimizing the sum squares of residuals between experimental and numerical predicted data. Shrinkage kinetics of the potato slices during dehydration was determined experimentally and found to be a linear function of removed moisture. The determined parameters were used in the mathematical model. The predicted moisture content values were compared to the experimental data and the validation results demonstrated that the dynamic drying curves were predicted by the methodology very well.
Finite Element Modeling of RMS Roughness Effect on the Contact Stiffness of Rough Surfaces
Directory of Open Access Journals (Sweden)
M.B. Amor
2016-09-01
Full Text Available The present study considers finite element analysis of an elastic and elastic-plastic contact between a rigid flat and a real rough surface taking into account the asperities interaction. Numerical modeling and measurement of the normal interfacial stiffness were conducted. Surfaces with different rms roughness values were investigated in the elastic and power-law hardening models to highlight the combined effect of the topography and the strain hardening on the contact characteristics. The influence of the surface roughness on the interaction between neighboring micro-contacts, the residual stress and deformation for the power-law hardening material was analyzed. The obtained results have shown the importance of considering the strain hardening in the modeling of a rough contact especially for rougher surface.
Multiscale damage and strength of lamellar bone modeled by cohesive finite elements.
Hamed, Elham; Jasiuk, Iwona
2013-12-01
A computational multiscale model of damage mechanisms and strength of lamellar bone is presented. The analysis incorporates the hierarchical structure of bone spanning the nanoscale (mineralized collagen fibril), the sub-microscale (single lamella) and the microscale (lamellar structure) levels. Due to the presence of several constituents (collagen, hydroxyapatite minerals, and non-collagenous proteins) and the different microstructural features at each scale, various deformation and failure mechanisms occur in bone at its several levels of hierarchy. The model takes into account the dominant damage mechanisms at the above mentioned three scales and predicts the strength of bone by using a cohesive finite element method. Elastic moduli of bone at these three different scales are also obtained as part of these calculations. The obtained modeling results compare well with other theoretical and experimental data available in the literature. © 2013 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Babak Ganji
2016-09-01
Full Text Available In the present paper, an electromagnetic simulation model is introduced for the conventional type of linear switched reluctance motor (LSRM in which the dynamic characteristics of the motor are predicted precisely by carrying out 2D finite element (FE transient analysis using ANSYS FE package. The simulation model is created totally in ANSYS parametric design language (APDL as a parametric model and it can be used easily for different designs of the conventional LSRMs. Introducing linear switched reluctance motor with segmental translator as a new type of LSRM, performance principles and design criteria are presented for two various topologies of this motor. Carrying out 2D FE transient analysis, dynamic characteristics of these two motors are predicted and compared to those obtained for the conventional LSRM.
Energy Technology Data Exchange (ETDEWEB)
Qi, M.; Wegner, J.; Ganzer, L. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE
2013-08-01
Polymer flooding, as an EOR method, has become one of the most important driving forces after water flooding. The conventional believe is that polymer flooding can only improve sweep efficiency, but it has no contribution to residual oil saturation reduction. However, experimental studies indicated that polymer solution can also improve displacement efficiency and decrease residual oil saturation. To get a better understanding of the mechanism to increase the microscopic sweep efficiency and the displacement efficiency, theoretical studies are required. In this paper, we studied the viscoelasticity effect of polymer by using a numerical simulator, which is based on Finite Element Analysis. Since it is showed experimentally that the first normal stress difference of viscoelastic polymer solution is higher than the second stress difference, the Oldroyd-B model was selected as the constitutive equation in the simulation. Numerical modelling of Oldroyd-B viscoelastic fluids is notoriously difficult. Standard Galerkin finite element methods are prone to numerical oscillations, and there is no convergence as the elasticity of fluid increases. Therefore, we use a stabilised finite element model. In order to verify our model, we first built up a model with the same geometry and fluid properties as presented in literature and compared the results. Then, with the tested model we simulated the effect of viscoelastic polymer fluid on dead pores in three simplified pore structures, which are contraction structure, expansion structure and expansion-contraction structure. Correspondingly, the streamlines and velocity contours of polymer solution, with different Reynolds numbers (Re) and Weissenberg numbers (We), flowing in these three structures are showed. The simulation results indicate that the viscoelasticity of polymer solution is the main contribution to increase the micro-scale sweep efficiency. With higher elasticity, the velocity of polymer solution is getting bigger at
Castaldo, Raffaele; Tizzani, Pietro
2016-04-01
Many numerical models have been developed to simulate the deformation and stress changes associated to the faulting process. This aspect is an important topic in fracture mechanism. In the proposed study, we investigate the impact of the deep fault geometry and tectonic setting on the co-seismic ground deformation pattern associated to different earthquake phenomena. We exploit the impact of the structural-geological data in Finite Element environment through an optimization procedure. In this framework, we model the failure processes in a physical mechanical scenario to evaluate the kinematics associated to the Mw 6.1 L'Aquila 2009 earthquake (Italy), the Mw 5.9 Ferrara and Mw 5.8 Mirandola 2012 earthquake (Italy) and the Mw 8.3 Gorkha 2015 earthquake (Nepal). These seismic events are representative of different tectonic scenario: the normal, the reverse and thrust faulting processes, respectively. In order to simulate the kinematic of the analyzed natural phenomena, we assume, under the plane stress approximation (is defined to be a state of stress in which the normal stress, sz, and the shear stress sxz and syz, directed perpendicular to x-y plane are assumed to be zero), the linear elastic behavior of the involved media. The performed finite element procedure consist of through two stages: (i) compacting under the weight of the rock successions (gravity loading), the deformation model reaches a stable equilibrium; (ii) the co-seismic stage simulates, through a distributed slip along the active fault, the released stresses. To constrain the models solution, we exploit the DInSAR deformation velocity maps retrieved by satellite data acquired by old and new generation sensors, as ENVISAT, RADARSAT-2 and SENTINEL 1A, encompassing the studied earthquakes. More specifically, we first generate 2D several forward mechanical models, then, we compare these with the recorded ground deformation fields, in order to select the best boundaries setting and parameters. Finally
Finite Element Based Lagrangian Vortex Dynamics Model for Wind Turbine Aerodynamics
International Nuclear Information System (INIS)
McWilliam, Michael K; Crawford, Curran
2014-01-01
This paper presents a novel aerodynamic model based on Lagrangian Vortex Dynamics (LVD) formulated using a Finite Element (FE) approach. The advantage of LVD is improved fidelity over Blade Element Momentum Theory (BEMT) while being faster than Numerical Navier-Stokes Models (NNSM) in either primitive or velocity-vorticity formulations. The model improves on conventional LVD in three ways. First, the model is based on an error minimization formulation that can be solved with fast root finding algorithms. In addition to improving accuracy, this eliminates the intrinsic numerical instability of conventional relaxed wake simulations. The method has further advantages in optimization and aero-elastic simulations for two reasons. The root finding algorithm can solve the aerodynamic and structural equations simultaneously, avoiding Gauss-Seidel iteration for compatibility constraints. The second is that the formulation allows for an analytical definition for sensitivity calculations. The second improvement comes from a new discretization scheme based on an FE formulation and numerical quadrature that decouples the spatial, influencing and temporal meshes. The shape for each trailing filament uses basis functions (interpolating splines) that allow for both local polynomial order and element size refinement. A completely independent scheme distributes the influencing (vorticity) elements along the basis functions. This allows for concentrated elements in the near wake for accuracy and progressively less in the far-wake for efficiency. Finally the third improvement is the use of a far-wake model based on semi-infinite vortex cylinders where the radius and strength are related to the wake state. The error-based FE formulation allows the transition to the far wake to occur across a fixed plane
Izadbakhsh, Adel; Inal, Kaan; Mishra, Raja K.
2012-04-01
In this paper, the finite strain plastic deformation of AM30 magnesium alloy has been simulated using the crystal plasticity finite element method. The simulations have been carried out using a rate-dependent elastic-viscoplastic crystal plasticity constitutive model implemented in a user defined material subroutine (UMAT) in the commercial software LS-DYNA. The plastic deformation mechanisms accounted for in the model are the slip systems in the matrix (parent grain), extension twinning systems and the slip systems inside the extension twinned regions. The parameters of the constitutive model have been calibrated using the experimental data. The calibrated model has then been used to predict the deformation of AM30 magnesium alloy in bending and simple shear. For the bending strain path, the effects of texture on the strain accommodated by the deformation mechanisms and bending moment have been investigated. For simple shear, the effects of texture on the relative activity of deformation mechanisms, shear stress and texture evolution have been investigated. Also, the effect of twinning on shear stress and texture evolution has been studied. The numerical analyses predicted a more uniform strain distribution during bending and simple shear for rolled texture compared with extruded texture.
A discontinuous finite element approach to cracking in coupled poro-elastic fluid flow models
Wilson, C. R.; Spiegelman, M. W.; Evans, O.; Ulven, O. I.; Sun, W.
2016-12-01
Reaction-driven cracking is a coupled process whereby fluid-induced reactions drive large volume changes in the host rock which produce stresses leading to crack propagation and failure. This in turn generates new surface area and fluid-flow pathways for subsequent reaction in a potentially self-sustaining system. This mechanism has has been proposed for the pervasive serpentinization and carbonation of peridotite, as well as applications to mineral carbon sequestration and hydrocarbon extraction. The key computational issue in this problem is implementing algorithms that adequately model the formation of discrete fractures. Here we present models using a discontinuous finite element method for modeling fracture formation (Radovitsky et al., 2011). Cracks are introduced along facets of the mesh by the relaxation of penalty parameters once a failure criterion is met. It is fully described in the weak form of the equations, requiring no modification of the underlying mesh structure and allowing fluid properties to be easily adjusted along cracked facets. To develop and test the method, we start by implementing the algorithm for the simplified Biot equations for poro-elasticity using the finite element model assembler TerraFERMA. We consider hydro-fracking around a borehole (Grassl et al., 2015), where elevated fluid pressure in the poro-elastic solid causes it to fail radially in tension. We investigate the effects of varying the Biot coefficient and adjusting the fluid transport properties in the vicinity of the crack and compare our results to related dual-graph models (Ulven & Sun, submitted). We discuss issues arising from this method, including the formation of null spaces and appropriate preconditioning and solution strategies. Initial results suggest that this method provides a promising way to incorporate cracking into our reactive fluid flow models and future work aims to integrate the mechanical and chemical aspects of this process.
Lacroix, Damien; Planell, Josep A; Prendergast, Patrick J
2009-05-28
Scaffold biomaterials for tissue engineering can be produced in many different ways depending on the applications and the materials used. Most research into new biomaterials is based on an experimental trial-and-error approach that limits the possibility of making many variations to a single material and studying its interaction with its surroundings. Instead, computer simulation applied to tissue engineering can offer a more exhaustive approach to test and screen out biomaterials. In this paper, a review of the current approach in biomaterials designed through computer-aided design (CAD) and through finite-element modelling is given. First we review the approach used in tissue engineering in the development of scaffolds and the interactions existing between biomaterials, cells and mechanical stimuli. Then, scaffold fabrication through CAD is presented and characterization of existing scaffolds through computed images is reviewed. Several case studies of finite-element studies in tissue engineering show the usefulness of computer simulations in determining the mechanical environment of cells when seeded into a scaffold and the proper design of the geometry and stiffness of the scaffold. This creates a need for more advanced studies that include aspects of mechanobiology in tissue engineering in order to be able to predict over time the growth and differentiation of tissues within scaffolds. Finally, current perspectives indicate that more efforts need to be put into the development of such advanced studies, with the removal of technical limitations such as computer power and the inclusion of more accurate biological and genetic processes into the developed algorithms.
Li, Jianfeng; Xiao, Mingqing; Liang, Yajun; Tang, Xilang; Li, Chao
2018-01-01
The solenoid valve is a kind of basic automation component applied widely. It’s significant to analyze and predict its degradation failure mechanism to improve the reliability of solenoid valve and do research on prolonging life. In this paper, a three-dimensional finite element analysis model of solenoid valve is established based on ANSYS Workbench software. A sequential coupling method used to calculate temperature filed and mechanical stress field of solenoid valve is put forward. The simulation result shows the sequential coupling method can calculate and analyze temperature and stress distribution of solenoid valve accurately, which has been verified through the accelerated life test. Kalman filtering algorithm is introduced to the data processing, which can effectively reduce measuring deviation and restore more accurate data information. Based on different driving current, a kind of failure mechanism which can easily cause the degradation of coils is obtained and an optimization design scheme of electro-insulating rubbers is also proposed. The high temperature generated by driving current and the thermal stress resulting from thermal expansion can easily cause the degradation of coil wires, which will decline the electrical resistance of coils and result in the eventual failure of solenoid valve. The method of finite element analysis can be applied to fault diagnosis and prognostic of various solenoid valves and improve the reliability of solenoid valve’s health management.
Pelat, Adrien; Felix, Simon; Pagneux, Vincent
2011-03-01
In modeling the wave propagation within a street canyon, particular attention must be paid to the description of both the multiple reflections of the wave on the building facades and the radiation in the free space above the street. The street canyon being considered as an open waveguide with a discontinuously varying cross-section, a coupled modal-finite element formulation is proposed to solve the three-dimensional wave equation within. The originally open configuration-the street canyon open in the sky above-is artificially turned into a close waveguiding structure by using perfectly matched layers that truncate the infinite sky without introducing numerical reflection. Then the eigenmodes of the resulting waveguide are determined by a finite element method computation in the cross-section. The eigensolutions can finally be used in a multimodal formulation of the wave propagation along the canyon, given its geometry and the end conditions at its extremities: initial field condition at the entrance and radiation condition at the output. © 2011 Acoustical Society of America
Ruoff, Jürgen; Würslin, Christian; Graf, Hansjörg; Schick, Fritz
2012-05-01
Prediction of interactions between the radiofrequency electromagnetic field in magnetic resonance scanners and electrically conductive material surrounded by tissue plays an increasing role for magnetic resonance safety. Testing of conductive implants or instruments is usually performed by standardized experimental setups and temperature measurements at distinct geometrical points, which cannot always reflect worst-case situations. A finite element method based on Matlab (The Mathworks, Natick, MA) and the finite element method program Comsol Multiphysics (Stockholm, Sweden) with a spatially highly variable mesh size solving Maxwell's full-wave equations was applied for a comprehensive simulation of the complete geometrical arrangement of typical birdcage radiofrequency coils loaded with small conductive structures in a homogenous medium. Conductive implants like rods of variable length and closed and open ring structures, partly exhibiting electromagnetic resonance behavior, were modeled and evaluated regarding the distribution of the B(1)- and E-field, induced currents and specific absorption rates. Numerical simulations corresponded well with experiments using a spin-echo sequence for visualization of marked B(1)-field inhomogeneities. Even resonance effects in conductive rods and open rings with suitable geometry were depicted accurately. The proposed method has high potential for complementation or even replacement of common experimental magnetic resonance compatibility measurements. Copyright © 2011 Wiley Periodicals, Inc.
A study of finite element modeling for simulation of vehicle rollover
Lin, Zhigui; Liu, Changye; Lv, Juncheng; Jia, Ligang; Sun, Haichao; Chen, Tao
2017-04-01
At present, the automobile ownership has been a very large figure, and growing rapidly with the social progress and development. Automobile has been one of the most important transportation in people's life. Accordingly, there are a large number of fatalities and serious injuries in traffic accident every year. Vehicle safety has been paid more and more attentions in recent years. There are several kinds of traffic accidents including frontal crash, side crash, etc., while rollover crash is a special kind. The vehicle rollover has the lowest incidence in the all kinds of traffic accidents but has the highest rate of seriously injuries, most of which lead to death. For these reasons, it is very necessary to study the vehicle rollover crash. However, it's so hard that there are a small amount of literatures studying rollover due to its variety, large degree of freedom, and difficulty to repeat and control. The method to investigate rollover crash contains experiment, the finite element method and rigid-body-based models. The finite element method contains many advantages such as low cost, repeatability, detailed data and so on, but the limitation is obvious. A test and simulation has been accomplished to study the FEM for vehicle rollover crash particularly in this paper.
Pazos, Valérie; Mongrain, Rosaire; Tardif, Jean-Claude
2010-06-01
Clinical studies on lipid-lowering therapy have shown that changing the composition of lipid pools reduced significantly the risk of cardiac events associated with plaque rupture. It has been shown also that changing the composition of the lipid pool affects its mechanical properties. However, knowledge about the mechanical properties of human atherosclerotic lesions remains limited due to the difficulty of the experiments. This paper aims to assess the feasibility of characterizing a lipid pool embedded in the wall of a pressurized vessel using finite-element simulations and an optimization algorithm. Finite-element simulations of inflation experiments were used together with nonlinear least squares algorithm to estimate the material model parameters of the wall and of the inclusion. An optimal fit of the simulated experiment and the real experiment was sought with the parameter estimation algorithm. The method was first tested on a single-layer polyvinyl alcohol (PVA) cryogel stenotic vessel, and then, applied on a double-layered PVA cryogel stenotic vessel with a lipid inclusion.
quadratic spline finite element method
Directory of Open Access Journals (Sweden)
A. R. Bahadir
2002-01-01
Full Text Available The problem of heat transfer in a Positive Temperature Coefficient (PTC thermistor, which may form one element of an electric circuit, is solved numerically by a finite element method. The approach used is based on Galerkin finite element using quadratic splines as shape functions. The resulting system of ordinary differential equations is solved by the finite difference method. Comparison is made with numerical and analytical solutions and the accuracy of the computed solutions indicates that the method is well suited for the solution of the PTC thermistor problem.
Books and monographs on finite element technology
Noor, A. K.
1985-01-01
The present paper proviees a listing of all of the English books and some of the foreign books on finite element technology, taking into account also a list of the conference proceedings devoted solely to finite elements. The references are divided into categories. Attention is given to fundamentals, mathematical foundations, structural and solid mechanics applications, fluid mechanics applications, other applied science and engineering applications, computer implementation and software systems, computational and modeling aspects, special topics, boundary element methods, proceedings of symmposia and conferences on finite element technology, bibliographies, handbooks, and historical accounts.
Finite Element Modeling of the Behavior of Armor Materials Under High Strain Rates and Large Strains
Polyzois, Ioannis
For years high strength steels and alloys have been widely used by the military for making armor plates. Advances in technology have led to the development of materials with improved resistance to penetration and deformation. Until recently, the behavior of these materials under high strain rates and large strains has been primarily based on laboratory testing using the Split Hopkinson Pressure Bar apparatus. With the advent of sophisticated computer programs, computer modeling and finite element simulations are being developed to predict the deformation behavior of these metals for a variety of conditions similar to those experienced during combat. In the present investigation, a modified direct impact Split Hopkinson Pressure Bar apparatus was modeled using the finite element software ABAQUS 6.8 for the purpose of simulating high strain rate compression of specimens of three armor materials: maraging steel 300, high hardness armor (HHA), and aluminum alloy 5083. These armor materials, provided by the Canadian Department of National Defence, were tested at the University of Manitoba by others. In this study, the empirical Johnson-Cook visco-plastic and damage models were used to simulate the deformation behavior obtained experimentally. A series of stress-time plots at various projectile impact momenta were produced and verified by comparison with experimental data. The impact momentum parameter was chosen rather than projectile velocity to normalize the initial conditions for each simulation. Phenomena such as the formation of adiabatic shear bands caused by deformation at high strains and strain rates were investigated through simulations. It was found that the Johnson-Cook model can accurately simulate the behavior of body-centered cubic (BCC) metals such as steels. The maximum shear stress was calculated for each simulation at various impact momenta. The finite element model showed that shear failure first occurred in the center of the cylindrical specimen and
Generic finite element models of orthodontic mini-implants: Are they reliable?
Albogha, Mhd Hassan; Takahashi, Ichiro
2015-11-05
Many finite element (FE) studies used different settings for modeling orthodontic mini-implants (OMIs). This study aims to compare different approaches for modeling OMI with FE method, to exhibit the role of key factors in modeling process. A computerized tomography (CT) dataset of a living human is used to develop subject-specific FE model of bone specimen, and a microCT was used to generate the geometry of OMI. Another five models were developed to assess the effect of changing different settings of FE modeling process. These five models differed from the subject-specific model in either: (i) bone properties' assignment method, (ii) geometries and constrains' conditions, or (iii) simulation method of bone-implant contact (BIC). The models presented significant differences in maximum principal strain distribution. These differences were most apparent when the models differed either in the nature of BIC or the method of assigning bone properties. The models different only in bone geometries showed differences in the intensity of strain rather than its distribution pattern. There is a need for assessment and validation of all FE modeling approaches currently used for simulation of mechanical environment in the bone surrounding OMIs. Copyright © 2015 Elsevier Ltd. All rights reserved.
Finite element modelling of chain-die forming for ultra-high strength steel
Majji, Raju; Xiang, Yang; Ding, Scott; Yang, Chunhui
2017-10-01
There has been a high demand for weight reduction in automotive vehicles while maintaining passenger safety. A potential steel material to achieve this is Ultra High Strength Steel (UHSS). As a high strength material, it is difficult to be formed with desired profiles using traditional sheet metal forming processes such as Cold Roll Forming. To overcome this problem, a potentially alternative solution is Chain-die Forming (CDF), recently developed. The basic principal of the CDF is to fully combine roll forming and bending processes. The main advantage of this process is the elongated deformation length that significantly increases effective roll radius. This study focuses on identifying issues with the CDF by using CAD modelling, Motion Analysis and Finite Element Analysis (FEA) to devise solutions and construct a more reliable process in an optimal design sense. Some attempts on finite element modelling and simulation of the CDF were conducted using relatively simple models in literature and the research was still not sufficient enough for optimal design of a typical CDF for UHSS. Therefore two numerical models of Chain-die Forming process are developed in this study, including a) one having a set of rolls similar to roll forming but with a large radius, i.e., 20 meters; and b) the other one with dies and punch segments similar to a typical CDF machine. As a case study, to form a 60° channel with single pass was conducted using these two devised models for a comparison. The obtained numerical results clearly show the CDF could generate less residual stress, low strain and small springback of a single pass for the 60° UHSS channel. The design analysis procedure proposed in this study could greatly help the mechanical designers to devise a cost-effective and reliable CDF process for forming UHSS.
Nonlinear, finite deformation, finite element analysis
Nguyen, Nhung; Waas, Anthony M.
2016-06-01
The roles of the consistent Jacobian matrix and the material tangent moduli, which are used in nonlinear incremental finite deformation mechanics problems solved using the finite element method, are emphasized in this paper, and demonstrated using the commercial software ABAQUS standard. In doing so, the necessity for correctly employing user material subroutines to solve nonlinear problems involving large deformation and/or large rotation is clarified. Starting with the rate form of the principle of virtual work, the derivations of the material tangent moduli, the consistent Jacobian matrix, the stress/strain measures, and the objective stress rates are discussed and clarified. The difference between the consistent Jacobian matrix (which, in the ABAQUS UMAT user material subroutine is referred to as DDSDDE) and the material tangent moduli ( C e ) needed for the stress update is pointed out and emphasized in this paper. While the former is derived based on the Jaumann rate of the Kirchhoff stress, the latter is derived using the Jaumann rate of the Cauchy stress. Understanding the difference between these two objective stress rates is crucial for correctly implementing a constitutive model, especially a rate form constitutive relation, and for ensuring fast convergence. Specifically, the implementation requires the stresses to be updated correctly. For this, the strains must be computed directly from the deformation gradient and corresponding strain measure (for a total form model). Alternatively, the material tangent moduli derived from the corresponding Jaumann rate of the Cauchy stress of the constitutive relation (for a rate form model) should be used. Given that this requirement is satisfied, the consistent Jacobian matrix only influences the rate of convergence. Its derivation should be based on the Jaumann rate of the Kirchhoff stress to ensure fast convergence; however, the use of a different objective stress rate may also be possible. The error associated
A Lower Limb-Pelvis Finite Element Model with 3D Active Muscles.
Mo, Fuhao; Li, Fan; Behr, Michel; Xiao, Zhi; Zhang, Guanjun; Du, Xianping
2018-01-01
A lower limb-pelvis finite element (FE) model with active three-dimensional (3D) muscles was developed in this study for biomechanical analysis of human body. The model geometry was mainly reconstructed from a male volunteer close to the anthropometry of a 50th percentile Chinese male. Tissue materials and structural features were established based on the literature and new implemented experimental tests. In particular, the muscle was modeled with a combination of truss and hexahedral elements to define its passive and active properties as well as to follow the detailed anatomy structure. Both passive and active properties of the model were validated against the experiments of Post-Mortem Human Surrogate (PMHS) and volunteers, respectively. The model was then used to simulate driver's emergency braking during frontal crashes and investigate Knee-Thigh-Hip (KTH) injury mechanisms and tolerances of the human body. A significant force and bending moment variance was noted for the driver's femur due to the effects of active muscle forces during emergency braking. In summary, the present lower limb-pelvis model can be applied in various research fields to support expensive and complex physical tests or corresponding device design.
Stress categorization in nozzle to pressure vessel connections finite elements models
International Nuclear Information System (INIS)
Albuquerque, Levi Barcelos de
1999-01-01
The ASME Boiler and Pressure Vessel Code, Section III , is the most important code for nuclear pressure vessels design. Its design criteria were developed to preclude the various pressure vessel failure modes throughout the so-called 'Design by Analysis', some of them by imposing stress limits. Thus, failure modes such as plastic collapse, excessive plastic deformation and incremental plastic deformation under cyclic loading (ratchetting) may be avoided by limiting the so-called primary and secondary stresses. At the time 'Design by Analysis' was developed (early 60's) the main tool for pressure vessel design was the shell discontinuity analysis, in which the results were given in membrane and bending stress distributions along shell sections. From that time, the Finite Element Method (FEM) has had a growing use in pressure vessels design. In this case, the stress results are neither normally separated in membrane and bending stress nor classified in primary and secondary stresses. This process of stress separation and classification in Finite Element (FE) results is what is called stress categorization. In order to perform the stress categorization to check results from FE models against the ASME Code stress limits, mainly from 3D solid FE models, several research works have been conducted. This work is included in this effort. First, a description of the ASME Code design criteria is presented. After that, a brief description of how the FEM can be used in pressure vessel design is showed. Several studies found in the literature on stress categorization for pressure vessel FE models are reviewed and commented. Then, the analyses done in this work are presented in which some typical nozzle to pressure vessel connections subjected to internal pressure and concentrated loads were modeled with solid finite elements. The results from linear elastic and limit load analyses are compared to each other and also with the results obtained by formulae for simple shell
International Nuclear Information System (INIS)
Pot, G.; Laurence, D.; Rharif, N.E.; Leal de Sousa, L.; Compe, C.
1995-12-01
This paper deals with the introduction of a second moment closure turbulence model (Reynolds Stress Model) in an industrial finite element code, N3S, developed at Electricite de France.The numerical implementation of the model in N3S will be detailed in 2D and 3D. Some details are given concerning finite element computations and solvers. Then, some results will be given, including a comparison between standard k-ε model, R.S.M. model and experimental data for some test case. (authors). 22 refs., 3 figs
Pak, Chan-Gi; Truong, Samson S.
2014-01-01
Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of Multi Utility Technology Test Bed, X-56A, aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of X-56A. The ground vibration test validated structural dynamic finite element model of the X-56A is created in this study. The structural dynamic finite element model of the X-56A is improved using a model tuning tool. In this study, two different weight configurations of the X-56A have been improved in a single optimization run.
Finite element model for beef chilling using CFD-generated heat transfer coefficients
Energy Technology Data Exchange (ETDEWEB)
Pham, Q.T. [University of New South Wales, Sydney, NSW 2052 (Australia); Trujillo, F.J. [Food Science Australia, 11 Julius Avenue, North Ryde, NSW 2113 (Australia); McPhail, N. [Food Science Australia, P.O. Box 3312, Tingalpa DC, Brisbane, QLD 4173 (Australia)
2009-01-15
A combined model of the beef chilling process is presented, in which computational fluid dynamics (CFD) was used to estimate the local heat and mass transfer coefficients, assuming uniform surface temperatures, and a set of 2-D finite element grids was used to solve the heat transfer equation in the product, which has an elongated shape. Another set of 1-D grids was used to solve the water transport equation near the surface of the meat. The surface transfer coefficients were calculated for various combinations of air orientations and speeds, and summarised in a set of regression equations. The model was verified by existing and new data on heat load, temperatures, weight loss and surface water activity. (author)
Finite Element Analysis of the Amontons-Coulomb's Model using Local and Global Friction Tests
International Nuclear Information System (INIS)
Oliveira, M. C.; Menezes, L. F.; Ramalho, A.; Alves, J. L.
2011-01-01
In spite of the abundant number of experimental friction tests that have been reported, the contact with friction modeling persists to be one of the factors that determine the effectiveness of sheet metal forming simulation. This difficulty can be understood due to the nature of the friction phenomena, which comprises the interaction of different factors connected to both sheet and tools' surfaces. Although in finite element numerical simulations friction models are commonly applied at the local level, they normally rely on parameters identified based on global experimental tests results. The aim of this study is to analyze the applicability of the Amontons-Coulomb's friction coefficient identified using complementary tests: (i) load-scanning, at the local level and (ii) draw-bead, at the global level; to the numerical simulation of sheet metal forming processes.
A fully coupled finite element model for stress distribution in buried gas pipeline
International Nuclear Information System (INIS)
Yahya Sukirman; Zainal Zakaria; Woong Soon Yue
2001-01-01
The study of stress-strain relationship is very important in many designs of buried structures over the years. The behavior and mechanism between the interaction of soil and buried structures such as a natural pipeline will mostly contributes to the integrity of the pipeline. This paper presents a fully coupled finite element of consolidation analysis model to study the stress-strain distribution along a buried pipeline before it excess its maximum deformation limit. The behavior of the soil-pipeline system can be modelled by a non-linear elasto-plastic based on Mohr-Coulomb and critical state yield surfaces. The deformation and deflection of the pipeline due to drained and external loading condition will be considered here. Finally the stress-strain distribution of the buried pipeline will be utilised to obtain the maximum deformation limit and the deflection of the buried pipeline. (Author)
Tomita, Sunao; Suzuki, Hayato; Kajiwara, Itsuro; Nakamura, Gen; Jiang, Yu; Suga, Mikio; Obata, Takayuki; Tadano, Shigeru
2018-01-01
Magnetic resonance elastography (MRE) is a technique to identify the viscoelastic moduli of biological tissues by solving the inverse problem from the displacement field of viscoelastic wave propagation in a tissue measured by MRI. Because finite element analysis (FEA) of MRE evaluates not only the viscoelastic model for a tissue but also the efficiency of the inversion algorithm, we developed FEA for MRE using commercial software called ANSYS, the Zener model for displacement field of a wave inside tissue, and an inversion algorithm called the modified integral method. The profile of the simulated displacement field by FEA agrees well with the experimental data measured by MRE for gel phantoms. Similarly, the value of storage modulus (i.e., stiffness) recovered using the modified integral method with the simulation data is consistent with the value given in FEA. Furthermore, applying the suggested FEA to a human liver demonstrates the effectiveness of the present simulation scheme.
Directory of Open Access Journals (Sweden)
Kunal Pathak
2016-09-01
Full Text Available The calcium signaling plays a crucial role in expansion and contraction of cardiac myocytes. This calcium signaling is achieved by calcium diffusion, buffering mechanisms and influx in cardiac myocytes. The various calcium distribution patterns required for achieving calcium signaling in myocytes are still not well understood. In this paper an attempt has been made to develop a model of calcium distribution in myocytes incorporating diffusion of calcium, point source and excess buffer approximation. The model has been developed for a two dimensional unsteady state case. Appropriate boundary conditions and initial condition have been framed. The finite element method has been employed to obtain the solution. The numerical results have been used to study the effect of buffers and source amplitude on calcium distribution in myocytes.
Finite Element Analysis of Biot’s Consolidation with a Coupled Nonlinear Flow Model
Directory of Open Access Journals (Sweden)
Yue-bao Deng
2016-01-01
Full Text Available A nonlinear flow relationship, which assumes that the fluid flow in the soil skeleton obeys the Hansbo non-Darcian flow and that the coefficient of permeability changes with void ratio, was incorporated into Biot’s general consolidation theory for a consolidation simulation of normally consolidated soft ground with or without vertical drains. The governing equations with the coupled nonlinear flow model were presented first for the force equilibrium condition and then for the continuity condition. Based on the weighted residual method, the finite element (FE formulations were then derived, and an existing FE program was modified accordingly to take the nonlinear flow model into consideration. Comparative analyses using established theoretical solutions and numerical solutions were completed, and the results were satisfactory. On this basis, we investigated the effect of the coupled nonlinear flow on consolidation development.
Finite element modeling of ground deformation and gravity field at Mt. Etna
Directory of Open Access Journals (Sweden)
G. Ganci
2008-06-01
Full Text Available An elastic 3-D axi-symmetric model based on Finite Element Method (FEM is proposed to compute ground deformation and gravity changes caused by overpressure sources in volcanic areas. The numerical computations are focused on the modeling of a complex description of Mt Etna in order to evaluate the effect of topography, medium heterogeneities and source geometries. Both ground deformation and gravity changes are investigated by solving a coupled numerical problem considering a simplified ground surface profile and a multi-layered crustal structure inferred from seismic tomography. The role of the source geometry is also explored taking into account spherical and ellipsoidal volumetric sources. The comparison between numerical results and those predicted by analytical solutions disclosed significant discrepancies. These differences constrain the applicability of simple spherical source and homogeneous half-space hypotheses, which are usually implicitly assumed when analytical solutions are applied.
Directory of Open Access Journals (Sweden)
Mohammed Asif. M
2015-12-01
Full Text Available Solid state joining techniques are increasingly employed in joining duplex stainless steel materials due to their high integrity. Continuous drive friction welding is a solid state welding technique which is used to join similar and dissimilar materials. This joining technique is characterized by short cycle time, low heat input and narrow heat affected zones. The simulation becomes an important tool in friction welding because of short welding cycle. In the present work, a three dimensional non-linear finite element model was developed. The thermal history and axial shortening profiles were predicted using ANSYS, a software tool. This numerical model was validated using experimental results. The results show that the frictional heating stage of the process has more influence on temperature and upsetting stage has more impact on axial shortening. The knowledge of these parameters would lead to optimization of input parameters and improvement of design and machine tools.
Directory of Open Access Journals (Sweden)
Myriam Rocío Pallares Muñoz
2009-01-01
Full Text Available Designing mechanical systems which are submitted to vibration requires calculation methods which are very different to those u-sed in other disciplines because, when this occurs, the magnitude of the forces becomes secondary and the frequency with which the force is repeated becomes the most important aspect. It must be taken care of, given that smaller periodic forces can prompt disasters than greater static forces. The article presents a representative problem regarding systems having forced vibration, the mathematical treatment of differential equations from an electrical and mechanical viewpoint, an electrical analogy, numerical modeling of circuits using ANSYS finite element software, analysis and comparison of numerical modeling results compared to test values, the post-processing of results and conclusions regarding electrical analogy methodology when analysing forced vibra-tion systems.
Quasi-static indentation modelling of aluminium specimen using finite element analysis
Directory of Open Access Journals (Sweden)
Mayank Nirbhay
2017-03-01
Full Text Available The influence of different types of rigid hemispherical and conical indenters on a rectangular specimen of aluminium has been investigated, in the small indenter test. A 3-D finite-element FE model was used to carry out the computation of the elastic-plastic solution of different rigid hemispherical and conical indenters. Three hemispherical-headed and four conical-headed indenters were designed and developed for testing. FE software ABAQUS® has been used to determine the load vs. indenter-displacement curves, reaction forces, deformation contours and Von-Mises stresses. The FE model was validated by comparing the results with the experimental data received from the Hertz Contact Theory and was found to be in reasonably good agreement.
Hydrodynamics of free surface flows modelling with the finite element method
Hervouet, Jean-Michel
2007-01-01
A definitive guide for accurate state-of-the-art modelling of free surface flows Understanding the dynamics of free surface flows is the starting point of many environmental studies, impact studies, and waterworks design. Typical applications, once the flows are known, are water quality, dam impact and safety, pollutant control, and sediment transport. These studies used to be done in the past with scale models, but these are now being replaced by numerical simulation performed by software suites called "hydro-informatic systems". The Telemac system is the leading software package worldwide, and has been developed by Electricité de France and Jean-Michel Hervouet, who is the head and main developer of the Telemac project. Written by a leading authority on Computational Fluid Dynamics, the book aims to provide environmentalists, hydrologists, and engineers using hydro-informatic systems such as Telemac and the finite element method, with the knowledge of the basic principles, capabilities, different hypothese...
Finite element model of size, shape and blood pressure on rupture of intracranial saccular aneurysms
Rica Nabong, Jennica; David, Guido
2017-10-01
Rupture of intracranial saccular aneurysms is a primary concern for neurologists and patients because it leads to stroke and permanent disability. This paper examines the role of blood pressure, in connection with size of and wall thickness, in the rupture of saccular aneurysms. A bulb-shaped geometry of a saccular aneurysm is obtained from angiographic images of a patient and modeled using Finite Elements based on the principle of virtual work under the Fung stress-strain relationship. The numerical model is subjected to varying levels of systolic blood pressure. Rupture is assumed to occur when the wall stress exceeded its mechanical strength. The results show which sizes of this class of aneurysms are at high risk of rupture for varying levels of blood pressure.
Sun, Wei; Sacks, Michael S
2005-11-01
Numerical simulations of the anisotropic mechanical properties of soft tissues and tissue-derived biomaterials using accurate constitutive models remain an important and challenging research area in biomechanics. While most constitutive modeling efforts have focused on the characterization of experimental data, only limited studies are available on the feasibility of utilizing those models in complex computational applications. An example is the widely utilized exponential constitutive model proposed by Fung. Although present in the biomechanics literature for several decades, implementation of this model into finite element (FE) simulations has been limited. A major reason for limited numerical implementations are problems associated with inherent numerical instability and convergence. To address this issue, we developed and applied two restrictions for a generalized Fung-elastic constitutive model necessary to achieve numerical stability. These are (1) convexity of the strain energy function, and (2) the condition number of material stiffness matrix set lower than a prescribed value. These constraints were implemented in the nonlinear regression used for constitutive model parameter estimation to the experimental biaxial mechanical data. We then implemented the generalized Fung-elastic model into a commercial FE code (ABAQUS, Pawtucket, RI, USA). Single element and multi-element planar biaxial test simulations were conducted to verify the accuracy and robustness of the implementation. Results indicated that numerical convergence and accurate FE implementation were consistently obtained. The present study thus presents an integrated framework for accurate and robust implementation of pseudo-elastic constitutive models for planar soft tissues. Moreover, since our approach is formulated within a general FE code, it can be straightforwardly adopted across multiple software platforms.
de Wit, A.J.; Akcay-Perdahcioglu, Didem; van den Brink, W.M.; de Boer, Andries
2012-01-01
Depending on the type of analysis, Finite Element(FE) models of different fidelity are necessary. Creating these models manually is a labor intensive task. This paper discusses a generic approach for generating FE models of different fidelity from a single reference FE model. These different
de Wit, A.J.; Akcay-Perdahcioglu, Didem; van den Brink, W.M.; de Boer, Andries; Rolfes, R.; Jansen, E.L.
2011-01-01
Depending on the type of analysis, Finite Element(FE) models of different fidelity are necessary. Creating these models manually is a labor intensive task. This paper discusses a generic approach for generating FE models of different fidelity from a single reference FE model. These different
A three-dimensional finite element model for the mechanics of cell-cell interactions.
Viens, Denis; Brodland, G Wayne
2007-10-01
Technical challenges, including significant ones associated with cell rearrangement, have hampered the development of three-dimensional finite element models for the mechanics of embryonic cells. These challenges have been overcome by a new formulation in which the contents of each cell, assumed to have a viscosity mu, are modeled using a system of orthogonal dashpots. This approach overcomes a stiffening artifact that affects more traditional models, in which space-filling viscous elements are used to model the cytoplasm. Cells are assumed to be polyhedral in geometry, and each n-sided polygonal face is subdivided into n triangles with a common node at the face center so that it needs not remain flat. A constant tension gamma is assumed to act along each cell-cell interface, and cell rearrangements occur through one of two complementary topological transformations. The formulation predicts mechanical interactions between pairs of similar or dissimilar cells that are consistent with experiments, two-dimensional simulations, contact angle theory, and intracellular pressure calculations. Simulations of the partial engulfment of one tissue type by another show that the formulation is able to model aggregates of several hundred cells without difficulty. Simulations carried out using this formulation suggest new experimental approaches for measuring cell surface tensions and interfacial tensions. The formulation holds promise as a tool for gaining insight into the mechanics of isolated or aggregated embryonic cells and for the design and interpretation of experiments that involve them.
Finite element analysis of an atomistically derived cohesive model for brittle fracture
International Nuclear Information System (INIS)
Lloyd, J T; McDowell, D L; Zimmerman, J A; Jones, R E; Zhou, X W
2011-01-01
In order to apply information from molecular dynamics (MD) simulations in problems governed by engineering length and time scales, a coarse graining methodology must be used. In previous work by Zhou et al (2009 Acta Mater. 57 4671–86), a traction-separation cohesive model was developed using results from MD simulations with atomistic-to-continuum measures of stress and displacement. Here, we implement this cohesive model within a combined finite element/cohesive surface element framework (referred to as a finite element approach or FEA), and examine the ability for the atomistically informed FEA to directly reproduce results from MD. We find that FEA shows close agreement of both stress and crack opening displacement profiles at the cohesive interface, although some differences do exist that can be attributed to the stochastic nature of finite temperature MD. The FEA methodology is then used to study slower loading rates that are computationally expensive for MD. We find that the crack growth process initially exhibits a rate-independent relationship between crack length and boundary displacement, followed by a rate-dependent regime where, at a given amount of boundary displacement, a lower applied strain rate produces a longer crack length. Our method is also extended to larger length scales by simulating a compact tension fracture-mechanics specimen with sub-micrometer dimensions. Such a simulation shows a computational speedup of approximately four orders of magnitude over conventional atomistic simulation, while exhibiting the expected fracture-mechanics response. Finally, differences between FEA and MD are explored with respect to ensemble and temperature effects in MD, and their impact on the cohesive model and crack growth behavior. These results enable us to make several recommendations to improve the methodology used to derive cohesive laws from MD simulations. In light of this work, which has critical implications for efforts to derive continuum laws
Programming the finite element method
Smith, I M; Margetts, L
2013-01-01
Many students, engineers, scientists and researchers have benefited from the practical, programming-oriented style of the previous editions of Programming the Finite Element Method, learning how to develop computer programs to solve specific engineering problems using the finite element method. This new fifth edition offers timely revisions that include programs and subroutine libraries fully updated to Fortran 2003, which are freely available online, and provides updated material on advances in parallel computing, thermal stress analysis, plasticity return algorithms, convection boundary c
Finite Element Modelling for Static and Free Vibration Response of Functionally Graded Beam
Directory of Open Access Journals (Sweden)
Ateeb Ahmad Khan
Full Text Available Abstract A 1D Finite Element model for static response and free vibration analysis of functionally graded material (FGM beam is presented in this work. The FE model is based on efficient zig-zag theory (ZIGT with two noded beam element having four degrees of freedom at each node. Linear interpolation is used for the axial displacement and cubic hermite interpolation is used for the deflection. Out of a large variety of FGM systems available, Al/SiC and Ni/Al2O3 metal/ceramic FGM system has been chosen. Modified rule of mixture (MROM is used to calculate the young's modulus and rule of mixture (ROM is used to calculate density and poisson's ratio of FGM beam at any point. The MATLAB code based on 1D FE zigzag theory for FGM elastic beams is developed. A 2D FE model for the same elastic FGM beam has been developed using ABAQUS software. An 8-node biquadratic plane stress quadrilateral type element is used for modeling in ABAQUS. Three different end conditions namely simply-supported, cantilever and clamped- clamped are considered. The deflection, normal stress and shear stress has been reported for various models used. Eigen Value problem using subspace iteration method is solved to obtain un-damped natural frequencies and the corresponding mode shapes. The results predicted by the 1D FE model have been compared with the 2D FE results and the results present in open literature. This proves the correctness of the model. Finally, mode shapes have also been plotted for various FGM systems.
Dynamic analysis of reactor containment building using axisymmetric finite element model
International Nuclear Information System (INIS)
Thakkar, S.K.; Dubey, R.N.
1989-01-01
The structural safety of nuclear reactor building during earthquake is of great importance in view of possibility of radiation hazards. The rational evaluation of forces and displacements in various portions of structure and foundation during strong ground motion is most important for safe performance and economic design of the reactor building. The accuracy of results of dynamic analysis is naturally dependent on the type of mathematical model employed. Three types of mathematical models are employed for dynamic analysis of reactor building beam model axisymmetric finite element model and three dimensional model. In this paper emphasis is laid on axisymmetric model. This model of containment building is considered a reinfinement over conventional beam model of the structure. The nuclear reactor building on a rocky foundation is considered herein. The foundation-structure interaction is relatively less in this condition. The objective of the paper is to highlight the significance of modelling of non-axisymmetric portion of building, such as reactor internals by equivalent axisymmetric body, on the structural response of the building
ADAPTIVE FINITE ELEMENT MODELING TECHNIQUES FOR THE POISSON-BOLTZMANN EQUATION
HOLST, MICHAEL; MCCAMMON, JAMES ANDREW; YU, ZEYUN; ZHOU, YOUNGCHENG; ZHU, YUNRONG
2011-01-01
We consider the design of an effective and reliable adaptive finite element method (AFEM) for the nonlinear Poisson-Boltzmann equation (PBE). We first examine the two-term regularization technique for the continuous problem recently proposed by Chen, Holst, and Xu based on the removal of the singular electrostatic potential inside biomolecules; this technique made possible the development of the first complete solution and approximation theory for the Poisson-Boltzmann equation, the first provably convergent discretization, and also allowed for the development of a provably convergent AFEM. However, in practical implementation, this two-term regularization exhibits numerical instability. Therefore, we examine a variation of this regularization technique which can be shown to be less susceptible to such instability. We establish a priori estimates and other basic results for the continuous regularized problem, as well as for Galerkin finite element approximations. We show that the new approach produces regularized continuous and discrete problems with the same mathematical advantages of the original regularization. We then design an AFEM scheme for the new regularized problem, and show that the resulting AFEM scheme is accurate and reliable, by proving a contraction result for the error. This result, which is one of the first results of this type for nonlinear elliptic problems, is based on using continuous and discrete a priori L∞ estimates to establish quasi-orthogonality. To provide a high-quality geometric model as input to the AFEM algorithm, we also describe a class of feature-preserving adaptive mesh generation algorithms designed specifically for constructing meshes of biomolecular structures, based on the intrinsic local structure tensor of the molecular surface. All of the algorithms described in the article are implemented in the Finite Element Toolkit (FETK), developed and maintained at UCSD. The stability advantages of the new regularization scheme
Surgery simulation using fast finite elements
DEFF Research Database (Denmark)
Bro-Nielsen, Morten
1996-01-01
This paper describes our recent work on real-time surgery simulation using fast finite element models of linear elasticity. In addition, we discuss various improvements in terms of speed and realism......This paper describes our recent work on real-time surgery simulation using fast finite element models of linear elasticity. In addition, we discuss various improvements in terms of speed and realism...
Analytical and Finite Element Modeling of Nanomembranes for Miniaturized, Continuous Hemodialysis
Directory of Open Access Journals (Sweden)
Tucker Burgin
2015-12-01
Full Text Available Hemodialysis involves large, periodic treatment doses using large-area membranes. If the permeability of dialysis membranes could be increased, it would reduce the necessary dialyzer size and could enable a wearable device that administers a continuous, low dose treatment of chronic kidney disease. This paper explores the application of ultrathin silicon membranes to this purpose, by way of analytical and finite element models of diffusive and convective transport of plasma solutes during hemodialysis, which we show to be predictive of experimental results. A proof-of-concept miniature nanomembrane dialyzer design is then proposed and analytically predicted to clear uremic toxins at near-ideal levels, as measured by several markers of dialysis adequacy. This work suggests the feasibility of miniature nanomembrane-based dialyzers that achieve therapeutic levels of uremic toxin clearance for patients with kidney failure.
Comparison of Finite Element Modeling and Experimental Pressure Distribution in a Diamond Anvil Cell
Kondrat'yev, Andreiy I.; Murphy, Michael J.; Weir, Samuel T.; Vohra, Yogesh K.
2002-10-01
Ultra high pressures can be obtained in a Diamond Anvil Cell (DAC) device by optimizing the geometrical shape of diamond anvil and by use of high strength gasket materials. Radial pressure distribution in a diamond-coated rhenium gasket was measured by the micro-collimated X-ray diffraction techniques at NSLS, Brookhaven National Laboratory up to peak pressure of 220 GPa. The process of DAC compression was described by finite element analysis using NIKE-2D software. The mechanical properties of the diamond-coated gasket material were modeled and radial pressure distribution obtained was in good agreement with the experimental data. The calculated shear stress in diamond in the axial direction was shown to depend strongly on the yield strength of the gasket material and may limit the ultimate pressure that can be obtained with the use of high strength gasket materials. Supported by the National Science Foundation (NSF) Grant No. DMR-0203779.
Hidalgo, Homero, Jr.
2000-01-01
An innovative methodology for determining structural target mode selection and mode selection based on a specific criterion is presented. An effective approach to single out modes which interact with specific locations on a structure has been developed for the X-33 Launch Vehicle Finite Element Model (FEM). We presented Root-Sum-Square (RSS) displacement method computes resultant modal displacement for each mode at selected degrees of freedom (DOF) and sorts to locate modes with highest values. This method was used to determine modes, which most influenced specific locations/points on the X-33 flight vehicle such as avionics control components, aero-surface control actuators, propellant valve and engine points for use in flight control stability analysis and for flight POGO stability analysis. Additionally, the modal RSS method allows for primary or global target vehicle modes to also be identified in an accurate and efficient manner.
Coupled electromagnetic and structural finite element analysis of a superconducting dipole model
International Nuclear Information System (INIS)
Hirtenfelder, F.
1996-01-01
Many devices contain parts that undergo motion due to electromagnetic forces. The motion causes the electromagnetic fields to change. Thus the electromagnetic fields must be computed along with the structural motion. In many cases the motion produced by electromagnetic forces is desired motion. However, in many devices, some undesired motion can occur due to electromagnetic forces. The motion creases motion-induced eddy currents which in turn affect the electromagnetic fields and forces. A finite element technique is described that fully couples structural and electromagnetic analysis in the time domain. The code is applied to a superconducting dipole model in order to study deformations and stresses during ramp and quench. The results of this coupled analysis enables the designer to visualize deformations, vibrations, displacements and all electromagnetic field quantities of the device and to try different solutions to enhance its performance
Modeling of heterogeneous elastic materials by the multiscale hp-adaptive finite element method
Klimczak, Marek; Cecot, Witold
2018-01-01
We present an enhancement of the multiscale finite element method (MsFEM) by combining it with the hp-adaptive FEM. Such a discretization-based homogenization technique is a versatile tool for modeling heterogeneous materials with fast oscillating elasticity coefficients. No assumption on periodicity of the domain is required. In order to avoid direct, so-called overkill mesh computations, a coarse mesh with effective stiffness matrices is used and special shape functions are constructed to account for the local heterogeneities at the micro resolution. The automatic adaptivity (hp-type at the macro resolution and h-type at the micro resolution) increases efficiency of computation. In this paper details of the modified MsFEM are presented and a numerical test performed on a Fichera corner domain is presented in order to validate the proposed approach.
Dynamic finite element model updating of prestressed concrete continuous box-girder bridge
Lin, Xiankun; Zhang, Lingmi; Guo, Qintao; Zhang, Yufeng
2009-09-01
The dynamic finite element model (FEM) of a prestressed concrete continuous box-girder bridge, called the Tongyang Canal Bridge, is built and updated based on the results of ambient vibration testing (AVT) using a real-coded accelerating genetic algorithm (RAGA). The objective functions are defined based on natural frequency and modal assurance criterion (MAC) metrics to evaluate the updated FEM. Two objective functions are defined to fully account for the relative errors and standard deviations of the natural frequencies and MAC between the AVT results and the updated FEM predictions. The dynamically updated FEM of the bridge can better represent its structural dynamics and serve as a baseline in long-term health monitoring, condition assessment and damage identification over the service life of the bridge.
A numerical strategy for finite element modeling of frictionless asymmetric vocal fold collision
DEFF Research Database (Denmark)
Granados, Alba; Misztal, Marek Krzysztof; Brunskog, Jonas
2016-01-01
. Theoretical background and numerical analysis of the finite-element position-based contact model are presented, along with validation. A novel contact detection mechanism capable to detect collision in asymmetric oscillations is developed. The effect of inexact contact constraint enforcement on vocal fold...... dynamics is examined by different variational methods for inequality constrained minimization problems, namely the Lagrange multiplier method and the penalty method. In contrast to the penalty solution, which is related to classical spring-like contact forces, numerical examples show that the parameter......-independent Lagrange multiplier solution is more robust and accurate in the estimation of dynamical and mechanical features at vocal fold contact. Furthermore, special attention is paid to the temporal integration schemes in relation to the contact problem, the results suggesting an advantage of highly diffusive...
Finite Element Model Characterization Of Nano-Composite Thermal And Environmental Barrier Coatings
Yamada, Yoshiki; Zhu, Dongming
2011-01-01
Thermal and environmental barrier coatings have been applied for protecting Si based ceramic matrix composite components from high temperature environment in advanced gas turbine engines. It has been found that the delamination and lifetime of T/EBC systems generally depend on the initiation and propagation of surface cracks induced by the axial mechanical load in addition to severe thermal loads. In order to prevent T/EBC systems from surface cracking and subsequent delamination due to mechanical and thermal stresses, T/EBC systems reinforced with nano-composite architectures have showed promise to improve mechanical properties and provide a potential crack shielding mechanism such as crack bridging. In this study, a finite element model (FEM) was established to understand the potential beneficial effects of nano-composites systems such as SiC nanotube-reinforced oxide T/EBC systems.
Dynamic mortar finite element method for modeling of shear rupture on frictional rough surfaces
Tal, Yuval; Hager, Bradford H.
2017-09-01
This paper presents a mortar-based finite element formulation for modeling the dynamics of shear rupture on rough interfaces governed by slip-weakening and rate and state (RS) friction laws, focusing on the dynamics of earthquakes. The method utilizes the dual Lagrange multipliers and the primal-dual active set strategy concepts, together with a consistent discretization and linearization of the contact forces and constraints, and the friction laws to obtain a semi-smooth Newton method. The discretization of the RS friction law involves a procedure to condense out the state variables, thus eliminating the addition of another set of unknowns into the system. Several numerical examples of shear rupture on frictional rough interfaces demonstrate the efficiency of the method and examine the effects of the different time discretization schemes on the convergence, energy conservation, and the time evolution of shear traction and slip rate.
Electrical vehicle drive control based on finite element induction motor model
Energy Technology Data Exchange (ETDEWEB)
Kandianis, T.; Kladas, A.G.; Manias, S.N.; Tegopoulos, J.A. [National Technical Univ., Athens (Greece)
1997-03-01
In electrical vehicle applications, AC drives have become attractive rivals of DC drives due to the evolution in semiconductor technology. A paramount concern in such applications is the overall efficiency of the motor and its PWM controller. In this paper, the methodology for determination of an induction motor model including parameter variations for different operating conditions is presented. The method is based on finite elements, and alternative techniques enabling to derive the equivalent circuit parameters from the field solution are described and discussed. The suitability of different techniques for the consideration of time variations in the application considered, such as complex variables and time stepping techniques, has been commented. The derived parameters are in good agreement with the low frequency response of the motor when supplied by a PWM inverter.
Huang, Maosong; Qu, Xie; Lü, Xilin
2017-11-01
By solving a nonlinear complementarity problem for the consistency condition, an improved implicit stress return iterative algorithm for a generalized over-nonlocal strain softening plasticity was proposed, and the consistent tangent matrix was obtained. The proposed algorithm was embodied into existing finite element codes, and it enables the nonlocal regularization of ill-posed boundary value problem caused by the pressure independent and dependent strain softening plasticity. The algorithm was verified by the numerical modeling of strain localization in a plane strain compression test. The results showed that a fast convergence can be achieved and the mesh-dependency caused by strain softening can be effectively eliminated. The influences of hardening modulus and material characteristic length on the simulation were obtained. The proposed algorithm was further used in the simulations of the bearing capacity of a strip footing; the results are mesh-independent, and the progressive failure process of the soil was well captured.
International Nuclear Information System (INIS)
Kim, K. S.; Lee, H. J.
2009-11-01
PRE-WELD program, which generates automatically the input file for the finite element analysis on the 2D butt welding at the dissimilar metal weld part, was developed. This program is pre-process program of the FEM code for analyzing the residual stress at the welding parts. Even if the users have not the detail knowledge for the FEM modelling, the users can make the ABAQUS INPUT easily by inputting the shape data of welding part, the weld current and voltage of welding parameters. By using PRE-WELD program, we can save the time and the effort greatly for preparing the ABAQUS INPUT for the residual stress analysis at the welding parts, and make the exact input without the human error
Comparative Analysis of Bulge Deformation between 2D and 3D Finite Element Models
Directory of Open Access Journals (Sweden)
Qin Qin
2014-02-01
Full Text Available Bulge deformation of the slab is one of the main factors that affect slab quality in continuous casting. This paper describes an investigation into bulge deformation using ABAQUS to model the solidification process. A three-dimensional finite element analysis model of the slab solidification process has been first established because the bulge deformation is closely related to slab temperature distributions. Based on slab temperature distributions, a three-dimensional thermomechanical coupling model including the slab, the rollers, and the dynamic contact between them has also been constructed and applied to a case study. The thermomechanical coupling model produces outputs such as the rules of bulge deformation. Moreover, the three-dimensional model has been compared with a two-dimensional model to discuss the differences between the two models in calculating the bulge deformation. The results show that the platform zone exists in the wide side of the slab and the bulge deformation is affected strongly by the ratio of width-to-thickness. The indications are also that the difference of the bulge deformation for the two modeling ways is little when the ratio of width-to-thickness is larger than six.
3D finite element model of the chinchilla ear for characterizing middle ear functions.
Wang, Xuelin; Gan, Rong Z
2016-10-01
Chinchilla is a commonly used animal model for research of sound transmission through the ear. Experimental measurements of the middle ear transfer function in chinchillas have shown that the middle ear cavity greatly affects the tympanic membrane (TM) and stapes footplate (FP) displacements. However, there is no finite element (FE) model of the chinchilla ear available in the literature to characterize the middle ear functions with the anatomical features of the chinchilla ear. This paper reports a recently completed 3D FE model of the chinchilla ear based on X-ray micro-computed tomography images of a chinchilla bulla. The model consisted of the ear canal, TM, middle ear ossicles and suspensory ligaments, and the middle ear cavity. Two boundary conditions of the middle ear cavity wall were simulated in the model as the rigid structure and the partially flexible surface, and the acoustic-mechanical coupled analysis was conducted with these two conditions to characterize the middle ear function. The model results were compared with experimental measurements reported in the literature including the TM and FP displacements and the middle ear input admittance in chinchilla ear. An application of this model was presented to identify the acoustic role of the middle ear septa-a unique feature of chinchilla middle ear cavity. This study provides the first 3D FE model of the chinchilla ear for characterizing the middle ear functions through the acoustic-mechanical coupled FE analysis.
Analysis of automotive rolling lobe air spring under alternative factors with finite element model
International Nuclear Information System (INIS)
Wong, Pak Kin; Xie, Zhengchao; Zhao, Jing; Xu, Tao; He, Feng
2014-01-01
Air springs are widely used in automotive suspensions for their superior performance in terms of low friction motion, adjustable load carrying capacity and user-friendly ride height control. However, it has posed great difficulties in constructing an accurate model as well as the analysis of the influence of alternative factors, such as cord angle, cord diameter and initial pressure. In this paper, a numerical model of the rolling lobe air spring (RLAS) is built by using finite element method and compared with an existing analytical model. An experiment with respect to the vertical stiffness of the RLAS is carried out to validate the accuracy of the proposed model. Evaluation result reveals that the existing analytical model cannot represent the performance of the RLAS very well, whereas the accuracy of the numerical model is very good. With the verified numerical model, the impacts of many alternative factors on the characteristics of the RLAS are analyzed. Numerical results show that the newly proposed model is reliable to determine the vertical characteristic and physical dimensions of the RLAS under the alternative factors.
Laursen, Tod A
2003-01-01
This book comprehensively treats the formulation and finite element approximation of contact and impact problems in nonlinear mechanics. Intended for students, researchers and practitioners interested in numerical solid and structural analysis, as well as for engineers and scientists dealing with technologies in which tribological response must be characterized, the book includes an introductory but detailed overview of nonlinear finite element formulations before dealing with contact and impact specifically. Topics encompassed include the continuum mechanics, mathematical structure, variational framework, and finite element implementations associated with contact/impact interaction. Additionally, important and currently emerging research topics in computational contact mechanics are introduced, encompassing such topics as tribological complexity, conservative treatment of inelastic impact interaction, and novel spatial discretization strategies.
Development of a detailed aircraft tyre finite element model for safety assessment
International Nuclear Information System (INIS)
Guo, H.; Bastien, C.; Blundell, M.; Wood, G.
2014-01-01
Highlights: • A full-scaled LS-Dyna finite element aircraft tyre model has been developed. • Rubber and fabric material properties have been characterized and correlated. • The FE tyre model has been validated by comparing static simulations with tests. • Dynamic simulations have been analyzed to achieve landing safety assessment. - Abstract: This paper describes the development of a detailed finite element (FE) model of an aircraft test tyre in order to investigate its performance and assess its safety criteria. It is noticed that rubber and fabric composite materials are the major components of this tyre model and their characterization requires tests and correlation. The characterization of such materials is of great importance in the model development process. Due to its complicated mechanical behaviour that exceeds the linear elastic theory, rubber is generally considered as hyperelastic material in FE analysis. It can be defined by a stored energy function with various coefficients that need to be determined by a series of experimental test data. The key issue is to define an appropriate energy function that can provide good fit with the experimental test data. Initially, a full-scaled LS-Dyna FE model has been development to replicate the actual geometry of the target test tyre. The material properties of each individual component have been characterized and correlated with industrial uniaxial tension test data. The inflation and static load simulations have been analyzed basing on the characterized tyre model, indicating its reliability. The dynamic simulations that aim to duplicate tyre load upon aircraft landing scenarios have also been analyzed. Following the comments and guidelines from aircraft industrial data, the dynamic simulations have covered the tyre loading scenarios from normal (soft) landing, hard landing to crash landing under different aircraft landing weights and vertical speeds. The tyre deflection rate and the contact load have
Quasi-Static Viscoelastic Finite Element Model of an Aircraft Tire
Johnson, Arthur R.; Tanner, John A.; Mason, Angela J.
1999-01-01
An elastic large displacement thick-shell mixed finite element is modified to allow for the calculation of viscoelastic stresses. Internal strain variables are introduced at the element's stress nodes and are employed to construct a viscous material model. First order ordinary differential equations relate the internal strain variables to the corresponding elastic strains at the stress nodes. The viscous stresses are computed from the internal strain variables using viscous moduli which are a fraction of the elastic moduli. The energy dissipated by the action of the viscous stresses is included in the mixed variational functional. The nonlinear quasi-static viscous equilibrium equations are then obtained. Previously developed Taylor expansions of the nonlinear elastic equilibrium equations are modified to include the viscous terms. A predictor-corrector time marching solution algorithm is employed to solve the algebraic-differential equations. The viscous shell element is employed to computationally simulate a stair-step loading and unloading of an aircraft tire in contact with a frictionless surface.
Lee, Chu-Hee; Landham, Priyan R; Eastell, Richard; Adams, Michael A; Dolan, Patricia; Yang, Lang
2017-09-01
Finite element models of an isolated vertebral body cannot accurately predict compressive strength of the spinal column because, in life, compressive load is variably distributed across the vertebral body and neural arch. The purpose of this study was to develop and validate a patient-specific finite element model of a functional spinal unit, and then use the model to predict vertebral strength from medical images. A total of 16 cadaveric functional spinal units were scanned and then tested mechanically in bending and compression to generate a vertebral wedge fracture. Before testing, an image processing and finite element analysis framework (SpineVox-Pro), developed previously in MATLAB using ANSYS APDL, was used to generate a subject-specific finite element model with eight-node hexahedral elements. Transversely isotropic linear-elastic material properties were assigned to vertebrae, and simple homogeneous linear-elastic properties were assigned to the intervertebral disc. Forward bending loading conditions were applied to simulate manual handling. Results showed that vertebral strengths measured by experiment were positively correlated with strengths predicted by the functional spinal unit finite element model with von Mises or Drucker-Prager failure criteria ( R 2 = 0.80-0.87), with areal bone mineral density measured by dual-energy X-ray absorptiometry ( R 2 = 0.54) and with volumetric bone mineral density from quantitative computed tomography ( R 2 = 0.79). Large-displacement non-linear analyses on all specimens did not improve predictions. We conclude that subject-specific finite element models of a functional spinal unit have potential to estimate the vertebral strength better than bone mineral density alone.
Directory of Open Access Journals (Sweden)
James O’Daniel
2011-01-01
Full Text Available Simulating fragment penetration into steel involves complicated modeling of severe behavior of the materials through multiple phases of response. Penetration of a fragment-like projectile was simulated using finite element (FE and meshfree particle formulations. Extreme deformation and failure of the material during the penetration event were modeled with several approaches to evaluate each as to how well it represents the actual physics of the material and structural response. A steel Fragment Simulating Projectile (FSP – designed to simulate a fragment of metal from a weapon casing – was simulated for normal impact into a flat square plate. A range of impact velocities was used to examine levels of exit velocity ranging from relatively small to one on the same level as the impact velocity. The numerical code EPIC, used for all the simulations presented herein, contains the element and particle formulations, as well as the explicit methodology and constitutive models needed to perform these simulations. These simulations were compared against experimental data, evaluating the damage caused to the projectile and the target plates, as well as comparing the residual velocity when the projectile perforated the target.
Wong, J.; Göktepe, S.; Kuhl, E.
2014-01-01
Summary Computational modeling of the human heart allows us to predict how chemical, electrical, and mechanical fields interact throughout a cardiac cycle. Pharmacological treatment of cardiac disease has advanced significantly over the past decades, yet it remains unclear how the local biochemistry of an individual heart cell translates into global cardiac function. Here we propose a novel, unified strategy to simulate excitable biological systems across three biological scales. To discretize the governing chemical, electrical, and mechanical equations in space, we propose a monolithic finite element scheme. We apply a highly efficient and inherently modular global-local split, in which the deformation and the transmembrane potential are introduced globally as nodal degrees of freedom, while the chemical state variables are treated locally as internal variables. To ensure unconditional algorithmic stability, we apply an implicit backward Euler finite difference scheme to discretize the resulting system in time. To increase algorithmic robustness and guarantee optimal quadratic convergence, we suggest an incremental iterative Newton-Raphson scheme. The proposed algorithm allows us to simulate the interaction of chemical, electrical, and mechanical fields during a representative cardiac cycle on a patient-specific geometry, robust and stable, with calculation times on the order of four days on a standard desktop computer. PMID:23798328
A new 3D finite element model of the IEC 60318-1 artificial ear
Bravo, Agustín; Barham, Richard; Ruiz, Mariano; López, Juan Manuel; DeArcas, Guillermo; Recuero, Manuel
2008-08-01
The artificial ear specified in IEC 60318-1 is used for the measurement of headphones and has been designed to present an acoustic load equivalent to that of normal human ears. In this respect it is specified in terms of an acoustical impedance, and modelled by a lumped parameter approach. However, this has some inherent frequency limitations and becomes less valid as the acoustic wavelength approaches the characteristic dimensions within the device. In addition, when sound propagates through structures such as narrow tubes, annular slits or over sharp corners, noticeable thermal and viscous effects take place causing further departure from the lumped parameter model. A new numerical model has therefore been developed, which gives proper consideration to the aforementioned effects. Both kinds of losses can be simulated by means of the LMS Virtual Lab acoustic software which facilitates finite and boundary element modelling of the whole artificial ear. A full 3D model of the artificial ear has therefore been developed based on key dimensional data found in IEC 60318-1. The model has been used to calculate the acoustical impedance, and the results compared with the corresponding data determined from the lumped parameter model. The numerical simulation of the artificial ear has been shown to provide realistic results, and is a powerful tool for developing a detailed understanding of the device. It is also proving valuable in the revision of IEC 60318-1 that is currently in progress.
Development of a Finite Element Head Model for the Study of Impact Head Injury
Directory of Open Access Journals (Sweden)
Bin Yang
2014-01-01
Full Text Available This study is aimed at developing a high quality, validated finite element (FE human head model for traumatic brain injuries (TBI prediction and prevention during vehicle collisions. The geometry of the FE model was based on computed tomography (CT and magnetic resonance imaging (MRI scans of a volunteer close to the anthropometry of a 50th percentile male. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The cerebrospinal fluid (CSF was simulated explicitly as a hydrostatic fluid by using a surface-based fluid modeling method. The model was validated in the loading condition observed in frontal impact vehicle collision. These validations include the intracranial pressure (ICP, brain motion, impact force and intracranial acceleration response, maximum von Mises stress in the brain, and maximum principal stress in the skull. Overall results obtained in the validation indicated improved biofidelity relative to previous FE models, and the change in the maximum von Mises in the brain is mainly caused by the improvement of the CSF simulation. The model may be used for improving the current injury criteria of the brain and anthropometric test devices.
Development of a finite element head model for the study of impact head injury.
Yang, Bin; Tse, Kwong-Ming; Chen, Ning; Tan, Long-Bin; Zheng, Qing-Qian; Yang, Hui-Min; Hu, Min; Pan, Gang; Lee, Heow-Pueh
2014-01-01
This study is aimed at developing a high quality, validated finite element (FE) human head model for traumatic brain injuries (TBI) prediction and prevention during vehicle collisions. The geometry of the FE model was based on computed tomography (CT) and magnetic resonance imaging (MRI) scans of a volunteer close to the anthropometry of a 50th percentile male. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The cerebrospinal fluid (CSF) was simulated explicitly as a hydrostatic fluid by using a surface-based fluid modeling method. The model was validated in the loading condition observed in frontal impact vehicle collision. These validations include the intracranial pressure (ICP), brain motion, impact force and intracranial acceleration response, maximum von Mises stress in the brain, and maximum principal stress in the skull. Overall results obtained in the validation indicated improved biofidelity relative to previous FE models, and the change in the maximum von Mises in the brain is mainly caused by the improvement of the CSF simulation. The model may be used for improving the current injury criteria of the brain and anthropometric test devices.
[The finite element modeling of human pelvis and its application in medicolegal expertise].
Li, Zheng-dong; Zou, Dong-hua; Liu, Ning-guo; Huang, Ping; Chen, Yi-jiu
2010-12-01
To develop a novel three dimensional finite element(FE) model of the human pelvis and investigate the biomechanics of the pelvic injury and explore the applications of FE approach in forensic medicine. The FE model of pelvis including bilateral iliac bones, sacrum, bilateral femurs, joint cartilages and ligaments was developed with Mimics 13.1 based on the CT images. The CT value of material properties were assigned. A static pressure of 600 N was applied at the upper surface of the sacrum endplate downwards along the vertical axis of sacral bone to validate the model. To simulate the side impacts, the lateral forces of 1, 2, 3, 4 and 5 kN were applied to the trochanter surface of right femur, respectively. The von Mises stress contours, displacement contours and stress distribution curves were subsequently calculated. An integrated FE model of pelvis including the joint cartilages and ligaments was successfully established. The model geometry coincided well with the CT images. The stress distributions of pelvis in erect position mainly located near the sacroiliac joints and the greater sciatic notches. Stress concentration was found on the superior and inferior pubis ramus, hip and sacroiliac joints on both sides under side impacts. The established FE model has accurate and reliable biomechanical features. The FE model can be used to simulate injury and provide intuitive and accurate evidence for medicolegal expertise.
Wu, Kuan
2007-12-01
The co-sintering behavior of low temperature co-fired ceramics (LTCC) is investigated by combining experiment and simulation methods. The numerical method offers a way to provide quantitative information regarding the final sintered shape of multilayer ceramics, which can be used to optimize the design of multilayer, multifunctional components and help reduce tedious and expensive empirical design iterations. To predict the sintering behavior of LTCC, parameters in the viscoplastic constitutive equations for single materials (such as shear viscosity G, bulk viscosity K, and sintering stress sigma s, etc.) need to be known. An apparatus was constructed for in situ measurements of the longitudinal and radial shrinkage during free sintering and sinter forging experiments. Cylindrical samples of individual LTCC materials (DuPont 951AX, Heraeus CT-800, Ferro A6-S) were made. Free sintering and sinter-forging experiments have been performed at various heating rates and under different intermittently applied axial loads. Various methods for analyzing the data were used to extract those parameters and their dependence on temperature and relative density. The constitutive parameters obtained from experiments were then implemented in the user subroutine UMAT of the general-purpose finite element program ABAQUS to simulate the free sintering behavior of bi-layer structures (DU951/CT800) with different thickness ratios. The simulation results were then compared with the actual experimental results, which were obtained by free co-sintering bi-layer planar samples with different thickness ratios. Simulation results showed the finite element analysis was successful in predicting the shape changes and the stresses at different positions during sintering of bi-layer structures. This finite element model was also used to examine the sensitivity to various parameters of the sintering results, such as elastic Poisson's ratio v, Young's modulus E, sintering stress sigmas, shear and
International Nuclear Information System (INIS)
Boyle, C.; Meguid, S.A.
2014-01-01
The Nuclear Waste Management Organization (NWMO) is developing a Used Fuel Container (UFC) optimized for CANDU fuel with an integrally bonded copper coating corrosion barrier. This paper demonstrates a validated finite element coating model, which can accurately predict the response of the UFC's steel-copper coating composite. Tensile, adhesion, and three-point bend tests were conducted for copper cold spray and electrodeposited coatings. The nonlinear finite element model accurately predicted the response of three different coating types, including cracking and delamination failure mechanisms, beyond the design basis loadings. The model will further be utilized to evaluate alternative UFC designs under anticipated repository conditions to assess safety margins. (author)
Nazari, Mohammad Ali; Perrier, Pascal; Payan, Yohan
2013-01-01
Purpose: The authors aimed to design a distributed lambda model (DLM), which is well adapted to implement three-dimensional (3-D), finite-element descriptions of muscles. Method: A muscle element model was designed. Its stress-strain relationships included the active force-length characteristics of the ? model along the muscle fibers, together…
Prediction of railway induced ground vibration through multibody and finite element modelling
Directory of Open Access Journals (Sweden)
G. Kouroussis
2013-04-01
Full Text Available The multibody approach is now recognized as a reliable and mature computer aided engineering tool. Namely, it is commonly used in industry for the design of road or railway vehicles. The paper presents a framework developed for predicting the vibrations induced by railway transportation. Firstly, the vehicle/track subsystem is simulated, on the basis of the home-made C++ library EasyDyn, by mixing the multibody model of the vehicle and the finite element model of the track, coupled to each other through the wheel/rail contact forces. Only the motion in the vertical plane is considered, assuming a total symmetry between left and right rails. This first step produces the time history of the forces exerted by the ballast on the foundation, which are then applied to a full 3-D FEM model of the soil, defined under the commercial software ABAQUS. The paper points out the contribution of the pitch motion of the bogies and carbodies which were neglected in previous publications, as well as the interest of the so-called coupled-lumped mass model (CLM to represent the influence of the foundation in the track model. The potentialities of the model are illustrated on the example of the Thalys high-speed train, riding at 300 km h−1 on the Belgian site of Mévergnies.
Pathophysiological aspects of cystocele with a 3D finite elements model.
Lamblin, Géry; Mayeur, Olivier; Giraudet, Géraldine; Jean Dit Gautier, Estelle; Chene, Gautier; Brieu, Mathias; Rubod, Chrystèle; Cosson, Michel
2016-11-01
The objective of this study is to design a 3D biomechanical model of the female pelvic system to assess pelvic organ suspension theories and understand cystocele mechanisms. A finite elements (FE) model was constructed to calculate the impact of suspension structure geometry on cystocele. The sample was a geometric model of a control patient's pelvic organs. The method used geometric reconstruction, implemented by the biomechanical properties of each anatomic structure. Various geometric configurations were simulated on the FE method to analyse the role of each structure and compare the two main anatomic theories. The main outcome measure was a 3D biomechanical model of the female pelvic system. The various configurations of bladder displacement simulated mechanisms underlying medial, lateral and apical cystocele. FE simulation revealed that pubocervical fascia is the most influential structure in the onset of median cystocele (essentially after 40 % impairment). Lateral cystocele showed a stronger influence of arcus tendineus fasciae pelvis (ATFP) on vaginal wall displacement under short ATFP lengthening. In apical cystocele, the uterosacral ligament showed greater influence than the cardinal ligament. Suspension system elongation increased displacement by 25 % in each type of cystocele. A 3D digital model enabled simulations of anatomic structures underlying cystocele to better understand cystocele pathophysiology. The model could be used to predict cystocele surgery results and personalising technique by preoperative simulation.
High Spatial Resolution Multi-Organ Finite Element Modeling of Ventricular-Arterial Coupling
Directory of Open Access Journals (Sweden)
Sheikh Mohammad Shavik
2018-03-01
Full Text Available While it has long been recognized that bi-directional interaction between the heart and the vasculature plays a critical role in the proper functioning of the cardiovascular system, a comprehensive study of this interaction has largely been hampered by a lack of modeling framework capable of simultaneously accommodating high-resolution models of the heart and vasculature. Here, we address this issue and present a computational modeling framework that couples finite element (FE models of the left ventricle (LV and aorta to elucidate ventricular—arterial coupling in the systemic circulation. We show in a baseline simulation that the framework predictions of (1 LV pressure—volume loop, (2 aorta pressure—diameter relationship, (3 pressure—waveforms of the aorta, LV, and left atrium (LA over the cardiac cycle are consistent with the physiological measurements found in healthy human. To develop insights of ventricular-arterial interactions, the framework was then used to simulate how alterations in the geometrical or, material parameter(s of the aorta affect the LV and vice versa. We show that changing the geometry and microstructure of the aorta model in the framework led to changes in the functional behaviors of both LV and aorta that are consistent with experimental observations. On the other hand, changing contractility and passive stiffness of the LV model in the framework also produced changes in both the LV and aorta functional behaviors that are consistent with physiology principles.
Finite element model to study temperature distribution in skin and deep tissues of human limbs.
Agrawal, Mamta; Pardasani, K R
2016-12-01
The temperature of body tissues is viewed as an indicator of tissue response in clinical applications since ancient times. The tissue temperature depends on various physical and physiological parameters like blood flow, metabolic heat generation, thermal conductivity of tissues, shape and size of organs etc. In this paper a finite element model has been proposed to study temperature distribution in skin and deep tissues of human limbs. The geometry of human limb is taken as elliptical tapered shape. It is assumed that outer surface of the limb is exposed to the environment. The appropriate boundary conditions have been framed based on physical conditions of the problem. The model has been developed for a three dimensional steady state case. Hexahedral circular sectoral elements are used to discretize the region. The results have been computed to obtain temperature profiles and study the relation of tissue temperature with the parameters like atmospheric temperature, rate of evaporation, thickness of tissues layers and shape of the limb. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Finite Element Modeling of Adsorption Processes for Gas Separation and Purification
International Nuclear Information System (INIS)
Humble, Paul H.; Williams, Richard M.; Hayes, James C.
2009-01-01
Pacific Northwest National Laboratory (PNNL) has expertise in the design and fabrication of automated radioxenon collection systems for nuclear explosion monitoring. In developing new systems there is an ever present need to reduce size, power consumption and complexity. Most of these systems have used adsorption based techniques for gas collection and/or concentration and purification. These processes include pressure swing adsorption, vacuum swing adsorption, temperature swing adsorption, gas chromatography and hybrid processes that combine elements of these techniques. To better understand these processes, and help with the development of improved hardware, a finite element software package (COMSOL Multiphysics) has been used to develop complex models of these adsorption based operations. The partial differential equations used include a mass balance for each gas species and adsorbed species along with a convection conduction energy balance equation. These equations in conjunction with multicomponent temperature dependent isotherm models are capable of simulating separation processes ranging from complex multibed PSA processes, and multicomponent temperature programmed gas chromatography, to simple two component temperature swing adsorption. These numerical simulations have been a valuable tool for assessing the capability of proposed processes and optimizing hardware and process parameters.
Energy Technology Data Exchange (ETDEWEB)
Günay, E. [Gazi University, Mechanical Engineering Department, 06570, Ankara (Turkey)
2016-04-21
In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values. In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.
Günay, E.
2016-04-01
In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values. In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.
International Nuclear Information System (INIS)
Günay, E.
2016-01-01
In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values. In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.
Numerical modeling of two-phase binary fluid mixing using mixed finite elements
Sun, Shuyu
2012-07-27
Diffusion coefficients of dense gases in liquids can be measured by considering two-phase binary nonequilibrium fluid mixing in a closed cell with a fixed volume. This process is based on convection and diffusion in each phase. Numerical simulation of the mixing often requires accurate algorithms. In this paper, we design two efficient numerical methods for simulating the mixing of two-phase binary fluids in one-dimensional, highly permeable media. Mathematical model for isothermal compositional two-phase flow in porous media is established based on Darcy\\'s law, material balance, local thermodynamic equilibrium for the phases, and diffusion across the phases. The time-lag and operator-splitting techniques are used to decompose each convection-diffusion equation into two steps: diffusion step and convection step. The Mixed finite element (MFE) method is used for diffusion equation because it can achieve a high-order and stable approximation of both the scalar variable and the diffusive fluxes across grid-cell interfaces. We employ the characteristic finite element method with moving mesh to track the liquid-gas interface. Based on the above schemes, we propose two methods: single-domain and two-domain methods. The main difference between two methods is that the two-domain method utilizes the assumption of sharp interface between two fluid phases, while the single-domain method allows fractional saturation level. Two-domain method treats the gas domain and the liquid domain separately. Because liquid-gas interface moves with time, the two-domain method needs work with a moving mesh. On the other hand, the single-domain method allows the use of a fixed mesh. We derive the formulas to compute the diffusive flux for MFE in both methods. The single-domain method is extended to multiple dimensions. Numerical results indicate that both methods can accurately describe the evolution of the pressure and liquid level. © 2012 Springer Science+Business Media B.V.
Wang, Xiaoling; Meng, Shuo; Han, Jingshi
2017-10-03
The Bacterial flagellar filament can undergo a polymorphic phase transition in response to both mechanical and chemical variations in vitro and in vivo environments. Under mechanical stimuli, such as viscous flow or forces induced by motor rotation, the filament changes its phase from left-handed normal (N) to right-handed semi-coiled (SC) via phase nucleation and growth. Our detailed mechanical analysis of existing experiments shows that both torque and bending moment contribute to the filament phase transition. In this paper, we establish a non-convex and non-local continuum model based on the Ginzburg-Landau theory to describe main characteristics of the filament phase transition such as new-phase nucleation, growth, propagation and the merging of neighboring interfaces. The finite element method (FEM) is adopted to simulate the phase transition under a displacement-controlled loading condition (rotation angle and bending deflection). We show that new-phase nucleation corresponds to the maximum torque and bending moment at the stuck end of the filament. The hysteresis loop in the loading and unloading curves indicates energy dissipation. When the new phase grows and propagates, torque and bending moment remain static. We also find that there is a drop in load when the two interfaces merge, indicating a concomitant reduction in the interfacial energy. Finally, the interface thickness is governed by the coefficients of the gradient of order parameters in the non-local interface energy. Our continuum theory and the finite element method provide a method to study the mechanical behavior of such biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.
On symmetric pyramidal finite elements
Czech Academy of Sciences Publication Activity Database
Liu, L.; Davies, K. B.; Yuan, K.; Křížek, Michal
2004-01-01
Roč. 11, 1-2 (2004), s. 213-227 ISSN 1492-8760 R&D Projects: GA AV ČR IAA1019201 Institutional research plan: CEZ:AV0Z1019905 Keywords : mesh generation * finite element method * composite elements Subject RIV: BA - General Mathematics Impact factor: 0.108, year: 2004