Finite elements of nonlinear continua
Oden, J T
2000-01-01
Geared toward undergraduate and graduate students, this text extends applications of the finite element method from linear problems in elastic structures to a broad class of practical, nonlinear problems in continuum mechanics. It treats both theory and applications from a general and unifying point of view.The text reviews the thermomechanical principles of continuous media and the properties of the finite element method, and then brings them together to produce discrete physical models of nonlinear continua. The mathematical properties of these models are analyzed, along with the numerical s
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...... on the governing equations and methods of implementing....
Introduction to nonlinear finite element analysis
Kim, Nam-Ho
2015-01-01
This book introduces the key concepts of nonlinear finite element analysis procedures. The book explains the fundamental theories of the field and provides instructions on how to apply the concepts to solving practical engineering problems. Instead of covering many nonlinear problems, the book focuses on three representative problems: nonlinear elasticity, elastoplasticity, and contact problems. The book is written independent of any particular software, but tutorials and examples using four commercial programs are included as appendices: ANSYS, NASTRAN, ABAQUS, and MATLAB. In particular, the MATLAB program includes all source codes so that students can develop their own material models, or different algorithms. This book also: · Presents clear explanations of nonlinear finite element analysis for elasticity, elastoplasticity, and contact problems · Includes many informative examples of nonlinear analyses so that students can clearly understand the nonlinear theory · ...
Nonlinear Finite Element Analysis of Ocean Cables
Institute of Scientific and Technical Information of China (English)
Nam-Il KIM; Sang-Soo JEON; Moon-Young KIM
2004-01-01
This study has focused on developing numerical procedures for the dynamic nonlinear analysis of cable structures subjected to wave forces and ground motions in the ocean. A geometrically nonlinear finite element procedure using the isoparametric curved cable element based on the Lagrangian formulation is briefly summarized. A simple and accurate method to determine the initial equilibrium state of cable systems associated with self-weights, buoyancy and the motion of end points is presented using the load incremental method combined with penalty method. Also the Newmark method is used for dynamic nonlinear analysis of ocean cables. Numerical examples are presented to validate the present numerical method.
Nonlinear Finite Element Analysis of Sloshing
Directory of Open Access Journals (Sweden)
Siva Srinivas Kolukula
2013-01-01
Full Text Available The disturbance on the free surface of the liquid when the liquid-filled tanks are excited is called sloshing. This paper examines the nonlinear sloshing response of the liquid free surface in partially filled two-dimensional rectangular tanks using finite element method. The liquid is assumed to be inviscid, irrotational, and incompressible; fully nonlinear potential wave theory is considered and mixed Eulerian-Lagrangian scheme is adopted. The velocities are obtained from potential using least square method for accurate evaluation. The fourth-order Runge-Kutta method is employed to advance the solution in time. A regridding technique based on cubic spline is employed to avoid numerical instabilities. Regular harmonic excitations and random excitations are used as the external disturbance to the container. The results obtained are compared with published results to validate the numerical method developed.
Fast Stiffness Matrix Calculation for Nonlinear Finite Element Method
Directory of Open Access Journals (Sweden)
Emir Gülümser
2014-01-01
Full Text Available We propose a fast stiffness matrix calculation technique for nonlinear finite element method (FEM. Nonlinear stiffness matrices are constructed using Green-Lagrange strains, which are derived from infinitesimal strains by adding the nonlinear terms discarded from small deformations. We implemented a linear and a nonlinear finite element method with the same material properties to examine the differences between them. We verified our nonlinear formulation with different applications and achieved considerable speedups in solving the system of equations using our nonlinear FEM compared to a state-of-the-art nonlinear FEM.
Nonlinearly Coupled Superconducting Lumped Element Resonators
Collodo, Michele C.; Potočnik, Anton; Rubio Abadal, Antonio; Mondal, Mintu; Oppliger, Markus; Wallraff, Andreas
We study SQUID-mediated tunable coupling between two superconducting on-chip resonators in the microwave frequency range. In this circuit QED implementation, we employ lumped-element type resonators, which consist of Nb thin film structured into interdigitated finger shunt capacitors and meander inductors. A SQUID, functioning as flux dependent and intrinsically nonlinear inductor, is placed as a coupling element together with an interdigitated capacitor between the two resonators (cf. A. Baust et al., Phys Rev. B 91 014515 (2015)). We perform a spectroscopic measurement in a dilution refrigerator and find the linear photon hopping rate between the resonators to be widely tunable as well as suppressible for an appropriate choice of parameters, which is made possible due to the interplay of inductively and capacitively mediated coupling. Vanishing linear coupling promotes nonlinear effects ranging from onsite- to cross-Kerr interaction. A dominating cross-Kerr interaction related to this configuration is notable, as it induces a unique quantum state. In the course of analog quantum simulations, such elementary building blocks can serve as a precursor for more complex geometries and thus pave the way to a number of novel quantum phases of light
A hybrid transfinite element approach for nonlinear transient thermal analysis
Tamma, Kumar K.; Railkar, Sudhir B.
1987-01-01
A new computational approach for transient nonlinear thermal analysis of structures is proposed. It is a hybrid approach which combines the modeling versatility of contemporary finite elements in conjunction with transform methods and classical Bubnov-Galerkin schemes. The present study is limited to nonlinearities due to temperature-dependent thermophysical properties. Numerical test cases attest to the basic capabilities and therein validate the transfinite element approach by means of comparisons with conventional finite element schemes and/or available solutions.
Finite Element Analysis to Two-Dimensional Nonlinear Sloshing Problems
Institute of Scientific and Technical Information of China (English)
严承华; 王赤忠; 程尔升
2001-01-01
A two-dimensional nonlinear sloshing problem is analyzed by means of the fully nonlinear theory and time domainsecond order theory of water waves. Liquid sloshing in a rectangular container subjected to a horizontal excitation is sim-ulated by the finite element method. Comparisons between the two theories are made based on their numerical results. Itis found that good agreement is obtained for the case of small amplitude oscillation and obvious differences occur forlarge amplitude excitation. Even though, the second order solution can still exhibit typical nonlinear features ofnonlinear wave and can be used instead of the fully nonlinear theory.
Nonlinear structural finite element model updating and uncertainty quantification
Ebrahimian, Hamed; Astroza, Rodrigo; Conte, Joel P.
2015-04-01
This paper presents a framework for nonlinear finite element (FE) model updating, in which state-of-the-art nonlinear structural FE modeling and analysis techniques are combined with the maximum likelihood estimation method (MLE) to estimate time-invariant parameters governing the nonlinear hysteretic material constitutive models used in the FE model of the structure. The estimation uncertainties are evaluated based on the Cramer-Rao lower bound (CRLB) theorem. A proof-of-concept example, consisting of a cantilever steel column representing a bridge pier, is provided to verify the proposed nonlinear FE model updating framework.
Application of gap element to nonlinear mechanics analysis of drillstring
Institute of Scientific and Technical Information of China (English)
刘巨保; 丁皓江; 张学鸿
2002-01-01
This paper presents a nonlinear finite element method to resolve the problem of the nonlinear contact between the drillstring and hole wall by using a Multi-directional Contact Gap Element (MCGE) contacting at appropriate positi o ns in each beam element. The method was successfully applied to the Daqing Oil F ield GP1 well. It was shown that the drillstring's contact resistance at any wel l depth could be obtained by calculations and that as the error in the calculati on of the hole top load is below 10%, the calculation result can provide theoret ical basis for the design and operation of drillstrings.
Investigation of the behavior of protection elements against field radiated line coupled UWB-pulses
Directory of Open Access Journals (Sweden)
R. Krzikalla
2006-01-01
Full Text Available To protect electronic systems against electromagnetic interferences in general nonlinear protection circuits are used. These protection circuits are optimized mostly against special transient interferences such as lightning electromagnetic pulses (LEMP or electromagnetic pulses caused by nuclear explosions (NEMP. Previous investigations have shown that these protection elements could be undermined by so-called ultra wideband (UWB pulses. Thereby a direct charge of the UWB-pulse to the elements has been assumed. This assumption was a worst case approximation because in practice UWB-pulses only get into systems by coupling effects. In this investigation the behavior of typical nonlinear protection elements has been tested with field radiated line coupled UWB-pulses. For that line coupled UWB-pulses have been defined depending on the coupling behavior of typical electronic systems and a possibility of generation of this kind of pulses is presented. After it typical nonlinear protection elements such as spark gaps, varistors and protection diodes have been tested with the previously defined test pulses. Finally the measured behavior of the elements has been compared with the behavior by direct charged UWB-pulses and the protection effect of the elements against field radiated line coupled UWB-pulses is re-evaluated.
Nonlinear/linear unified thermal stress formulations - Transfinite element approach
Tamma, Kumar K.; Railkar, Sudhir B.
1987-01-01
A new unified computational approach for applicability to nonlinear/linear thermal-structural problems is presented. Basic concepts of the approach including applicability to nonlinear and linear thermal structural mechanics are first described via general formulations. Therein, the approach is demonstrated for thermal stress and thermal-structural dynamic applications. The proposed transfinite element approach focuses on providing a viable hybrid computational methodology by combining the modeling versatility of contemporary finite element schemes in conjunction with transform techniques and the classical Bubnov-Galerkin schemes. Comparative samples of numerical test cases highlight the capabilities of the proposed concepts.
THE MORTAR ELEMENT METHOD FOR A NONLINEAR BIHARMONIC EQUATION
Institute of Scientific and Technical Information of China (English)
Zhong-ci Shi; Xue-jun Xu
2005-01-01
The mortar element method is a new domain decomposition method(DDM) with nonoverlapping subdomains. It can handle the situation where the mesh on different subdomains need not align across interfaces, and the matching of discretizations on adjacent subdomains is only enforced weakly. But until now there has been very little work for nonlinear PDEs. In this paper, we will present a mortar-type Morley element method for a nonlinear biharmonic equation which is related to the well-known Navier-Stokes equation. Optimal energy and H1-norm estimates are obtained under a reasonable elliptic regularity assumption.
Nonlinear Finite Element Analysis of Reinforced Concrete Shells
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Mustafa K. Ahmed
2013-05-01
Full Text Available This investigation is to develop a numerical model suitable for nonlinear analysis of reinforced concrete shells. A nine-node Lagrangian element Figure (1 with enhanced shear interpolation will be used in this study. Table (1 describes shape functions and their derivatives of this element.An assumed transverse shear strain is used in the formulation of this element to overcome shear locking. Degenerated quadratic thick plate elements employing a layered discrelization through the thickness will be adopted. Different numbers of layers for different thickness can be used per element. A number of layers between (6 and 10 have proved to be appropriate to represent the nonlinear material behavior in structures. In this research 8 layers will be adequate. Material nonlinearities due to cracking of concrete, plastic flow or crushing of concrete in compression and yield condition of reinforcing steel are considered. The maximum tensile strength is used as a criterion for crack initiation. Attention is given to the tension stiffening phenomenon and the degrading effect of cracking on the compressive and shear strength of concrete. Perfect bond between concrete and steel is assumed. Attention is given also to geometric nonlinearities. An example have been chosen in order to demonstrate the suitability of the models by comparing the predicted behaviour with the experimental results for shell exhibiting various modes of failure.
An Orthogonal Residual Procedure for Nonlinear Finite Element Equations
DEFF Research Database (Denmark)
Krenk, S.
A general and robust solution procedure for nonlinear finite element equations with limit points is developed. At each equilibrium iteration the magnitude of the load is adjusted such that the residual force is orthogonal to the current displacement increment from the last equilibrium state...
Unstructured Spectral Element Model for Dispersive and Nonlinear Wave Propagation
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Eskilsson, Claes; Bigoni, Daniele
2016-01-01
). In the present paper we use a single layer of quadratic (in 2D) and prismatic (in 3D) elements. The model has been stabilized through a combination of over-integration of the Galerkin projections and a mild modal filter. We present numerical tests of nonlinear waves serving as a proof-of-concept validation...
A Dual Orthogonality Procedure for Nonlinear Finite Element Equations
DEFF Research Database (Denmark)
Krenk, S.; Hededal, O.
In the orthogonal residual procedure for solution of nonlinear finite element equations the load is adjusted in each equilibrium iteration to satisfy an orthogonality condition to the current displacement increment. It is here shown that the quasi-newton formulation of the orthogonal residual...
Probabilistic finite elements for transient analysis in nonlinear continua
Liu, W. K.; Belytschko, T.; Mani, A.
1985-01-01
The probabilistic finite element method (PFEM), which is a combination of finite element methods and second-moment analysis, is formulated for linear and nonlinear continua with inhomogeneous random fields. Analogous to the discretization of the displacement field in finite element methods, the random field is also discretized. The formulation is simplified by transforming the correlated variables to a set of uncorrelated variables through an eigenvalue orthogonalization. Furthermore, it is shown that a reduced set of the uncorrelated variables is sufficient for the second-moment analysis. Based on the linear formulation of the PFEM, the method is then extended to transient analysis in nonlinear continua. The accuracy and efficiency of the method is demonstrated by application to a one-dimensional, elastic/plastic wave propagation problem. The moments calculated compare favorably with those obtained by Monte Carlo simulation. Also, the procedure is amenable to implementation in deterministic FEM based computer programs.
A nonlinear truss finite element with varying stiffness
Directory of Open Access Journals (Sweden)
Ďuriš R.
2007-11-01
Full Text Available This contribution deals with a new truss element with varying stiffness intended to geometric and physically nonlinear analysis of composite structures. We present a two-node straight composite truss finite element derived by new nonincremental full geometric nonlinear approach. Stiffness matrix of this composite truss contains transfer constants, which accurately describe the polynomial longitudinal variation of cross-section area and material properties. These variations could be caused by nonhomogenous temperature field or by varying components volume fractions of the composite or/and functionally graded materials (FGM´s. Numerical examples were solved to verify the established relations. The accuracy of the new proposed finite truss element are compared and discused.
Finite element model calibration of a nonlinear perforated plate
Ehrhardt, David A.; Allen, Matthew S.; Beberniss, Timothy J.; Neild, Simon A.
2017-03-01
This paper presents a case study in which the finite element model for a curved circular plate is calibrated to reproduce both the linear and nonlinear dynamic response measured from two nominally identical samples. The linear dynamic response is described with the linear natural frequencies and mode shapes identified with a roving hammer test. Due to the uncertainty in the stiffness characteristics from the manufactured perforations, the linear natural frequencies are used to update the effective modulus of elasticity of the full order finite element model (FEM). The nonlinear dynamic response is described with nonlinear normal modes (NNMs) measured using force appropriation and high speed 3D digital image correlation (3D-DIC). The measured NNMs are used to update the boundary conditions of the full order FEM through comparison with NNMs calculated from a nonlinear reduced order model (NLROM). This comparison revealed that the nonlinear behavior could not be captured without accounting for the small curvature of the plate from manufacturing as confirmed in literature. So, 3D-DIC was also used to identify the initial static curvature of each plate and the resulting curvature was included in the full order FEM. The updated models are then used to understand how the stress distribution changes at large response amplitudes providing a possible explanation of failures observed during testing.
NEW ALTERNATING DIRECTION FINITE ELEMENT SCHEME FOR NONLINEAR PARABOLIC EQUATION
Institute of Scientific and Technical Information of China (English)
崔霞
2002-01-01
A new alternating direction (AD) finite element (FE) scheme for 3-dimensional nonlinear parabolic equation and parabolic integro-differential equation is studied. By using AD,the 3-dimensional problem is reduced to a family of single space variable problems, calculation work is simplified; by using FE, high accuracy is kept; by using various techniques for priori estimate for differential equations such as inductive hypothesis reasoning, the difficulty arising from the nonlinearity is treated. For both FE and ADFE schemes, the convergence properties are rigorously demonstrated, the optimal H1- and L2-norm space estimates and the O((△t)2) estimate for time variable are obtained.
Nonlinear Finite Element Analysis of Nanoindentation of Viral Capsids
Gibbons, M M; Gibbons, Melissa M.; Klug, William S.
2006-01-01
Recent Atomic Force Microscope (AFM) nanoindentation experiments measuring mechanical response of the protein shells of viruses have provided a quantitative description of their strength and elasticity. To better understand and interpret these measurements, and to elucidate the underlying mechanisms, this paper adopts a course-grained modeling approach within the framework of three-dimensional nonlinear continuum elasticity. Homogeneous, isotropic, elastic, thick shell models are proposed for two capsids: the spherical Cowpea Chlorotic Mottle Virus (CCMV), and the ellipsocylindrical bacteriophage $\\phi 29$. As analyzed by the finite element method, these models enable parametric characterization of the effects of AFM tip geometry, capsid dimensions, and capsid constitutive descriptions. The generally nonlinear force response of capsids to indentation is shown to be insensitive to constitutive details, and greatly influenced by geometry. Nonlinear stiffening and softening of the force response is dependent on ...
Geometrically Nonlinear Finite Element Analysis of a Composite Space Reflector
Lee, Kee-Joo; Leet, Sung W.; Clark, Greg; Broduer, Steve (Technical Monitor)
2001-01-01
Lightweight aerospace structures, such as low areal density composite space reflectors, are highly flexible and may undergo large deflection under applied loading, especially during the launch phase. Accordingly, geometrically nonlinear analysis that takes into account the effect of finite rotation may be needed to determine the deformed shape for a clearance check and the stress and strain state to ensure structural integrity. In this study, deformation of the space reflector is determined under static conditions using a geometrically nonlinear solid shell finite element model. For the solid shell element formulation, the kinematics of deformation is described by six variables that are purely vector components. Because rotational angles are not used, this approach is free of the limitations of small angle increments. This also allows easy connections between substructures and large load increments with respect to the conventional shell formulation using rotational parameters. Geometrically nonlinear analyses were carried out for three cases of static point loads applied at selected points. A chart shows results for a case when the load is applied at the center point of the reflector dish. The computed results capture the nonlinear behavior of the composite reflector as the applied load increases. Also, they are in good agreement with the data obtained by experiments.
Domain decomposition solvers for nonlinear multiharmonic finite element equations
Copeland, D. M.
2010-01-01
In many practical applications, for instance, in computational electromagnetics, the excitation is time-harmonic. Switching from the time domain to the frequency domain allows us to replace the expensive time-integration procedure by the solution of a simple elliptic equation for the amplitude. This is true for linear problems, but not for nonlinear problems. However, due to the periodicity of the solution, we can expand the solution in a Fourier series. Truncating this Fourier series and approximating the Fourier coefficients by finite elements, we arrive at a large-scale coupled nonlinear system for determining the finite element approximation to the Fourier coefficients. The construction of fast solvers for such systems is very crucial for the efficiency of this multiharmonic approach. In this paper we look at nonlinear, time-harmonic potential problems as simple model problems. We construct and analyze almost optimal solvers for the Jacobi systems arising from the Newton linearization of the large-scale coupled nonlinear system that one has to solve instead of performing the expensive time-integration procedure. © 2010 de Gruyter.
Arc-length technique for nonlinear finite element analysis
Institute of Scientific and Technical Information of China (English)
MEMON Bashir-Ahmed; SU Xiao-zu(苏小卒)
2004-01-01
Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, Received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.
Nonlinear analysis of the forced response of structural elements
Nayfeh, A. H.; Mook, D. T.; Sridhar, S.
1974-01-01
A general procedure is presented for the nonlinear analysis of the forced response of structural elements to harmonic excitations. Internal resonances (i.e., modal interactions) are taken into account. All excitations are considered, with special consideration given to resonant excitations. The general procedure is applied to clamped-hinged beams. The results reveal that exciting a higher mode may lead to a larger response in a lower interacting mode, contrary to the results of linear analyses.
Coupling nonlinear Stokes and Darcy flow using mortar finite elements
Ervin, Vincent J.
2011-11-01
We study a system composed of a nonlinear Stokes flow in one subdomain coupled with a nonlinear porous medium flow in another subdomain. Special attention is paid to the mathematical consequence of the shear-dependent fluid viscosity for the Stokes flow and the velocity-dependent effective viscosity for the Darcy flow. Motivated by the physical setting, we consider the case where only flow rates are specified on the inflow and outflow boundaries in both subdomains. We recast the coupled Stokes-Darcy system as a reduced matching problem on the interface using a mortar space approach. We prove a number of properties of the nonlinear interface operator associated with the reduced problem, which directly yield the existence, uniqueness and regularity of a variational solution to the system. We further propose and analyze a numerical algorithm based on mortar finite elements for the interface problem and conforming finite elements for the subdomain problems. Optimal a priori error estimates are established for the interface and subdomain problems, and a number of compatibility conditions for the finite element spaces used are discussed. Numerical simulations are presented to illustrate the algorithm and to compare two treatments of the defective boundary conditions. © 2010 Published by Elsevier B.V. on behalf of IMACS.
Directory of Open Access Journals (Sweden)
Woo-Young Jung
2015-04-01
Full Text Available For the solution of geometrically nonlinear analysis of plates and shells, the formulation of a nonlinear nine-node refined first-order shear deformable element-based Lagrangian shell element is presented. Natural co-ordinate-based higher order transverse shear strains are used in present shell element. Using the assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. Furthermore, a refined first-order shear deformation theory for thin and thick shells, which results in parabolic through-thickness distribution of the transverse shear strains from the formulation based on the third-order shear deformation theory, is proposed. This formulation eliminates the need for shear correction factors in the first-order theory. To avoid difficulties resulting from large increments of the rotations, a scheme of attached reference system is used for the expression of rotations of shell normal. Numerical examples demonstrate that the present element behaves reasonably satisfactorily either for the linear or for geometrically nonlinear analysis of thin and thick plates and shells with large displacement but small strain. Especially, the nonlinear results of slit annular plates with various loads provided the benchmark to test the accuracy of related numerical solutions.
Non-linear analysis and calculation of the performance of a shelving protection system by FEM
García Nieto, P. J.; del Coz Díaz, J. J.; Vilán Vilán, J. A.; Suárez Sierra, J. L.
2012-12-01
The aim of this paper consists on the study, analysis and calculation of the efficiency of a shelving protection system by means of the finite element method (FEM). These shelving protection systems are intended to prevent the eventual damage due to the impacts of transport elements in motion, such as: forklifts, dumpers, hand pallet trucks, and so on. The impact loads may threaten the structural integrity of the shelving system. The present structural problem is highly non-linear, due to the simultaneous presence of the following nonlinearities: material non-linearity (plasticity in this case), geometrical non-linearity (large displacements) and contact-type boundary conditions (between the rigid body and the protection system). A total of forty eight different FEM models are built varying the thickness of the steel plate (4, 5 and 6 mm), the impact height (0.1, 0.2, 0.3 and 0.4 meters) and the impact direction (head-on collision and side impact). Once the models are solved, the stress distribution, the overall displacements and the absorbed impact energy were calculated. In order to determine the best shelving protection's candidate, some constraints must be taken into account: the maximum allowable stress (235 MPa), the maximum displacement (0.05 m) and the absorbed impact energy (400 J according to the European Standard Rule PREN-15512). Finally, the most important results are shown and conclusions of this study are exposed.
A Dual Super-Element Domain Decomposition Approach for Parallel Nonlinear Finite Element Analysis
Jokhio, G. A.; Izzuddin, B. A.
2015-05-01
This article presents a new domain decomposition method for nonlinear finite element analysis introducing the concept of dual partition super-elements. The method extends ideas from the displacement frame method and is ideally suited for parallel nonlinear static/dynamic analysis of structural systems. In the new method, domain decomposition is realized by replacing one or more subdomains in a "parent system," each with a placeholder super-element, where the subdomains are processed separately as "child partitions," each wrapped by a dual super-element along the partition boundary. The analysis of the overall system, including the satisfaction of equilibrium and compatibility at all partition boundaries, is realized through direct communication between all pairs of placeholder and dual super-elements. The proposed method has particular advantages for matrix solution methods based on the frontal scheme, and can be readily implemented for existing finite element analysis programs to achieve parallelization on distributed memory systems with minimal intervention, thus overcoming memory bottlenecks typically faced in the analysis of large-scale problems. Several examples are presented in this article which demonstrate the computational benefits of the proposed parallel domain decomposition approach and its applicability to the nonlinear structural analysis of realistic structural systems.
Unconstrained Finite Element for Geometrical Nonlinear Dynamics of Shells
Directory of Open Access Journals (Sweden)
Humberto Breves Coda
2009-01-01
Full Text Available This paper presents a positional FEM formulation to deal with geometrical nonlinear dynamics of shells. The main objective is to develop a new FEM methodology based on the minimum potential energy theorem written regarding nodal positions and generalized unconstrained vectors not displacements and rotations. These characteristics are the novelty of the present work and avoid the use of large rotation approximations. A nondimensional auxiliary coordinate system is created, and the change of configuration function is written following two independent mappings from which the strain energy function is derived. This methodology is called positional and, as far as the authors' knowledge goes, is a new procedure to approximated geometrical nonlinear structures. In this paper a proof for the linear and angular momentum conservation property of the Newmark algorithm is provided for total Lagrangian description. The proposed shell element is locking free for elastic stress-strain relations due to the presence of linear strain variation along the shell thickness. The curved, high-order element together with an implicit procedure to solve nonlinear equations guarantees precision in calculations. The momentum conserving, the locking free behavior, and the frame invariance of the adopted mapping are numerically confirmed by examples.
A Novel Nonlinear Programming Model for Distribution Protection Optimization
Zambon, Eduardo; Bossois, Débora Z.; Garcia, Berilhes B.; Azeredo, Elias F.
2009-01-01
This paper presents a novel nonlinear binary programming model designed to improve the reliability indices of a distribution network. This model identifies the type and location of protection devices that should be installed in a distribution feeder and is a generalization of the classical optimizat
A mixed finite element method for nonlinear diffusion equations
Burger, Martin
2010-01-01
We propose a mixed finite element method for a class of nonlinear diffusion equations, which is based on their interpretation as gradient flows in optimal transportation metrics. We introduce an appropriate linearization of the optimal transport problem, which leads to a mixed symmetric formulation. This formulation preserves the maximum principle in case of the semi-discrete scheme as well as the fully discrete scheme for a certain class of problems. In addition solutions of the mixed formulation maintain exponential convergence in the relative entropy towards the steady state in case of a nonlinear Fokker-Planck equation with uniformly convex potential. We demonstrate the behavior of the proposed scheme with 2D simulations of the porous medium equations and blow-up questions in the Patlak-Keller-Segel model. © American Institute of Mathematical Sciences.
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.
Complex spatiotemporal behavior in a chain of one-way nonlinearly coupled elements
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Berkemer, Rainer; Gorria, C.;
2011-01-01
The dynamics of asymmetrically coupled nonlinear elements is considered. It is shown that there are two distinctive regimes of oscillatory behavior of one-way nonlinearly coupled elements depending on the relaxation time and the strength of the coupling. In the subcritical regime when...... nonlinear model....
Nonlinear explicit transient finite element analysis on the Intel Delta
Energy Technology Data Exchange (ETDEWEB)
Plaskacz, E.J. [Argonne National Lab., IL (United States); Ramirez, M.R.; Gupta, S. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Civil Engineering
1993-03-01
Many large scale finite element problems are intractable on current generation production supercomputers. High-performance computer architectures offer effective avenues to bridge the gap between computational needs and the power of computational hardware. The biggest challenge lies in the substitution of the key algorithms in an application program with redesigned algorithms which exploit the new architectures and use better or more appropriate numerical techniques. A methodology for implementing nonlinear finite element analysis on a homogeneous distributed processing network is discussed. The method can also be extended to heterogeneous networks comprised of different machine architectures provided that they have a mutual communication interface. This unique feature has greatly facilitated the port of the code to the 8-node Intel Touchstone Gamma and then the 512-node Intel Touchstone Delta. The domain is decomposed serially in a preprocessor. Separate input files are written for each subdomain. These files are read in by local copies of the program executable operating in parallel. Communication between processors is addressed utilizing asynchronous and synchronous message passing. The basic kernel of message passing is the internal force exchange which is analogous to the computed interactions between sections of physical bodies in static stress analysis. Benchmarks for the Intel Delta are presented. Performance exceeding 1 gigaflop was attained. Results for two large-scale finite element meshes are presented.
Nonlinear explicit transient finite element analysis on the Intel Delta
Energy Technology Data Exchange (ETDEWEB)
Plaskacz, E.J. (Argonne National Lab., IL (United States)); Ramirez, M.R.; Gupta, S. (Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Civil Engineering)
1993-01-01
Many large scale finite element problems are intractable on current generation production supercomputers. High-performance computer architectures offer effective avenues to bridge the gap between computational needs and the power of computational hardware. The biggest challenge lies in the substitution of the key algorithms in an application program with redesigned algorithms which exploit the new architectures and use better or more appropriate numerical techniques. A methodology for implementing nonlinear finite element analysis on a homogeneous distributed processing network is discussed. The method can also be extended to heterogeneous networks comprised of different machine architectures provided that they have a mutual communication interface. This unique feature has greatly facilitated the port of the code to the 8-node Intel Touchstone Gamma and then the 512-node Intel Touchstone Delta. The domain is decomposed serially in a preprocessor. Separate input files are written for each subdomain. These files are read in by local copies of the program executable operating in parallel. Communication between processors is addressed utilizing asynchronous and synchronous message passing. The basic kernel of message passing is the internal force exchange which is analogous to the computed interactions between sections of physical bodies in static stress analysis. Benchmarks for the Intel Delta are presented. Performance exceeding 1 gigaflop was attained. Results for two large-scale finite element meshes are presented.
Generalized multiscale finite element methods. nonlinear elliptic equations
Efendiev, Yalchin R.
2013-01-01
In this paper we use the Generalized Multiscale Finite Element Method (GMsFEM) framework, introduced in [26], in order to solve nonlinear elliptic equations with high-contrast coefficients. The proposed solution method involves linearizing the equation so that coarse-grid quantities of previous solution iterates can be regarded as auxiliary parameters within the problem formulation. With this convention, we systematically construct respective coarse solution spaces that lend themselves to either continuous Galerkin (CG) or discontinuous Galerkin (DG) global formulations. Here, we use Symmetric Interior Penalty Discontinuous Galerkin approach. Both methods yield a predictable error decline that depends on the respective coarse space dimension, and we illustrate the effectiveness of the CG and DG formulations by offering a variety of numerical examples. © 2014 Global-Science Press.
Nonlinear Strain Measures, Shape Functions and Beam Elements for Dynamics of Flexible Beams
Energy Technology Data Exchange (ETDEWEB)
Sharf, I. [University of Victoria, Department of Mechanical Engineering (Canada)
1999-05-15
In this paper, we examine several aspects of the development of an explicit geometrically nonlinear beam element. These are: (i) linearization of the displacement field; (ii) the effect of a commonly adopted approximation for the nonlinear Lagrangian strain; and (iii) use of different-order shape functions for discretization. The issue of rigid-body check for a nonlinear beam element is also considered. An approximate check is introduced for an element based on an (approximate) intermediate strain measure. Several numerical examples are presented to support the analysis. The paper concludes with a discussion on the use of explicit nonlinear beam elements for multibody dynamics simulation.
Rahman, T.
2009-01-01
In this thesis, a finite element based perturbation approach is presented for geometrically nonlinear analysis of thin-walled structures. Geometrically nonlinear static and dynamic analyses are essential for this class of structures. Nowadays nonlinear analysis of thin-walled shell structures is oft
DEFF Research Database (Denmark)
Damkilde, Lars; Pedersen, Ronnie
2012-01-01
This paper describes a new triangular plane element which can be considered as a linear strain triangular element (LST) extended with incompatible displacement modes. The extended element will have a full cubic interpolation of strains and stresses. The extended LST-element is connected with other...... elements similar to the LST-element i.e. through three corner nodes and three mid-side nodes. The incompatible modes are associated with two displacement gradients at each mid-side node and displacements in the central node. The element passes the patch test and converges to the exact solution. The element...... has been tested on a standard linear test such as Cook’s panel, and is shown as expected to be somewhat more flexible than the LST-element and the compatible quadratic strain element (QST). The extended element has also been applied to material non-linear geotechnical problems. Geotechnical problems...
Non-linear finite element analysis in structural mechanics
Rust, Wilhelm
2015-01-01
This monograph describes the numerical analysis of non-linearities in structural mechanics, i.e. large rotations, large strain (geometric non-linearities), non-linear material behaviour, in particular elasto-plasticity as well as time-dependent behaviour, and contact. Based on that, the book treats stability problems and limit-load analyses, as well as non-linear equations of a large number of variables. Moreover, the author presents a wide range of problem sets and their solutions. The target audience primarily comprises advanced undergraduate and graduate students of mechanical and civil engineering, but the book may also be beneficial for practising engineers in industry.
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Some theoretical methods have been reported to deal with nonlinear problems of composite materials but the accuracy is not so good. In the meantime, a lot of nonlinear problems are difficult to be managed by the theoretical methods. The present study aims to use the developed method, the random microstructure finite element method, to deal with these nonlinear problems. In this paper, the random microstructure finite element method is used to deal with all three kinds of nonlinear property problems of composite materials. The analyzed results suggest that the influences of the nonlinear phenomena on the effective properties of composite materials are significant and the random microstructure finite element method is an efficient tool to investigate the nonlinear problems.
Efficient Realization of the Mixed Finite Element Discretization for nonlinear Problems
Knabner, Peter; Summ, Gerhard
2016-01-01
We consider implementational aspects of the mixed finite element method for a special class of nonlinear problems. We establish the equivalence of the hybridized formulation of the mixed finite element method to a nonconforming finite element method with augmented Crouzeix-Raviart ansatz space. We discuss the reduction of unknowns by static condensation and propose Newton's method for the solution of local and global systems. Finally, we show, how such a nonlinear problem arises from the mixe...
Tamma, Kumar K.; Railkar, Sudhir B.
1988-01-01
The 'transfinite element method' (TFEM) proposed by Tamma and Railkar (1987 and 1988) for the analysis of linear and nonlinear heat-transfer problems is described and demonstrated. The TFEM combines classical Galerkin and transform approaches with state-of-the-art FEMs to obtain a flexible hybrid modeling scheme. The fundamental principles of the TFEM and the derivation of the governing equations are reviewed, and numerical results for sample problems are presented in extensive graphs and briefly characterized. Problems analyzed include a square plate with a hole, a rectangular plate with natural and essential boundary conditions and varying thermal conductivity, the Space Shuttle thermal protection system, a bimaterial plate subjected to step temperature variations, and solidification in a semiinfinite liquid slab.
GLOBAL FINITE ELEMENT NONLINEAR GALERKIN METHOD FOR THE PENALIZED NAVIER-STOKES EQUATIONS
Institute of Scientific and Technical Information of China (English)
Yin-nian He; Yan-ren Hou; Li-quan Mei
2001-01-01
A global finite element nonlinear Galerkin method for the penalized Navier-Stokes equations is presented. This method is based on two finite element spaces XH and Xh,defined respectively on one coarse grid with grid size H and one fine grid with grid size h ＜＜ H. Comparison is also made with the finite element Galerkin method. If we choose H = O(ε-1/4h1/2), ε＞ 0 being the penalty parameter, then two methods are of the same order of approximation. However, the global finite element nonlinear Galerkin method is much cheaper than the standard finite element Galerkin method. In fact, in the finite element Galerkin method the nonlinearity is treated on the fine grid finite element space Xh and while in the global finite element nonlinear Galerkin method the similar nonlinearity is treated on the coarse grid finite element space XH and only the linearity needs to be treated on the fine grid increment finite element space Wh. Finally, we provide numerical test which shows above results stated.
Tamma, Kumar K.; Railkar, Sudhir B.
1987-01-01
The present paper describes the development of a new hybrid computational approach for applicability for nonlinear/linear thermal structural analysis. The proposed transfinite element approach is a hybrid scheme as it combines the modeling versatility of contemporary finite elements in conjunction with transform methods and the classical Bubnov-Galerkin schemes. Applicability of the proposed formulations for nonlinear analysis is also developed. Several test cases are presented to include nonlinear/linear unified thermal-stress and thermal-stress wave propagations. Comparative results validate the fundamental capablities of the proposed hybrid transfinite element methodology.
VEZF1 elements mediate protection from DNA methylation.
Directory of Open Access Journals (Sweden)
Jacqueline Dickson
2010-01-01
Full Text Available There is growing consensus that genome organization and long-range gene regulation involves partitioning of the genome into domains of distinct epigenetic chromatin states. Chromatin insulator or barrier elements are key components of these processes as they can establish boundaries between chromatin states. The ability of elements such as the paradigm beta-globin HS4 insulator to block the range of enhancers or the spread of repressive histone modifications is well established. Here we have addressed the hypothesis that a barrier element in vertebrates should be capable of defending a gene from silencing by DNA methylation. Using an established stable reporter gene system, we find that HS4 acts specifically to protect a gene promoter from de novo DNA methylation. Notably, protection from methylation can occur in the absence of histone acetylation or transcription. There is a division of labor at HS4; the sequences that mediate protection from methylation are separable from those that mediate CTCF-dependent enhancer blocking and USF-dependent histone modification recruitment. The zinc finger protein VEZF1 was purified as the factor that specifically interacts with the methylation protection elements. VEZF1 is a candidate CpG island protection factor as the G-rich sequences bound by VEZF1 are frequently found at CpG island promoters. Indeed, we show that VEZF1 elements are sufficient to mediate demethylation and protection of the APRT CpG island promoter from DNA methylation. We propose that many barrier elements in vertebrates will prevent DNA methylation in addition to blocking the propagation of repressive histone modifications, as either process is sufficient to direct the establishment of an epigenetically stable silent chromatin state.
Institute of Scientific and Technical Information of China (English)
Long Shuyao; Zhang Qin
2000-01-01
In this paper the dual reciprocity boundary element method is employed to solve nonlinear differential equation 2 u + u + εu3 = b. Results obtained in an example have a good agreement with those by FEM and show the applicability and simplicity of dual reciprocity method(DRM) in solving nonlinear dif ferential equations.
Evaluation of a transfinite element numerical solution method for nonlinear heat transfer problems
Cerro, J. A.; Scotti, S. J.
1991-01-01
Laplace transform techniques have been widely used to solve linear, transient field problems. A transform-based algorithm enables calculation of the response at selected times of interest without the need for stepping in time as required by conventional time integration schemes. The elimination of time stepping can substantially reduce computer time when transform techniques are implemented in a numerical finite element program. The coupling of transform techniques with spatial discretization techniques such as the finite element method has resulted in what are known as transfinite element methods. Recently attempts have been made to extend the transfinite element method to solve nonlinear, transient field problems. This paper examines the theoretical basis and numerical implementation of one such algorithm, applied to nonlinear heat transfer problems. The problem is linearized and solved by requiring a numerical iteration at selected times of interest. While shown to be acceptable for weakly nonlinear problems, this algorithm is ineffective as a general nonlinear solution method.
LEAST-SQUARES MIXED FINITE ELEMENT METHODS FOR NONLINEAR PARABOLIC PROBLEMS
Institute of Scientific and Technical Information of China (English)
Dan-ping Yang
2002-01-01
Two least-squares mixed finite element schemes are formulated to solve the initialboundary value problem of a nonlinear parabolic partial differential equation and the convergence of these schemes are analyzed.
The Full—Discrete Mixed Finite Element Methods for Nonlinear Hyperbolic Equations
Institute of Scientific and Technical Information of China (English)
YanpingCHEN; YunqingHUANG
1998-01-01
This article treats mixed finite element methods for second order nonlinear hyperbolic equations.A fully discrete scheme is presented and improved L2-error estimates are established.The convergence of both the function value andthe flux is demonstrated.
Barut, A.; Madenci, Erdogan; Tessler, A.
1997-01-01
This study presents a transient nonlinear finite element analysis within the realm of a multi-body dynamics formulation for determining the dynamic response of a moderately thick laminated shell undergoing a rapid and large rotational motion and nonlinear elastic deformations. Nonlinear strain measure and rotation, as well as 'the transverse shear deformation, are explicitly included in the formulation in order to capture the proper motion-induced stiffness of the laminate. The equations of motion are derived from the virtual work principle. The analysis utilizes a shear deformable shallow shell element along with the co-rotational form of the updated Lagrangian formulation. The shallow shell element formulation is based on the Reissner-Mindlin and Marguerre theory.
Institute of Scientific and Technical Information of China (English)
GUO Qintao; ZHANG Lingmi; TAO Zheng
2008-01-01
Thin wall component is utilized to absorb impact energy of a structure. However, the dynamic behavior of such thin-walled structure is highly non-linear with material, geometry and boundary non-linearity. A model updating and validation procedure is proposed to build accurate finite element model of a frame structure with a non-linear thin-walled component for dynamic analysis. Design of experiments (DOE) and principal component decomposition (PCD) approach are applied to extract dynamic feature from nonlinear impact response for correlation of impact test result and FE model of the non-linear structure. A strain-rate-dependent non-linear model updating method is then developed to build accurate FE model of the structure. Computer simulation and a real frame structure with a highly non-linear thin-walled component are employed to demonstrate the feasibility and effectiveness of the proposed approach.
Basic Studies of Nonlinear Optical Materials for Eye and Sensor Protection
2004-03-10
1 BASIC STUDIES OF NONLINEAR OPTICAL MATERIALS FOR EYE AND SENSOR PROTECTION I. Abstract: We have studied the spectroscopy, kinetics and...study liquid or solid materials from CW to 100x10-15 seconds. Basic Studies of Nonlinear Optical Materials for Eye and Sensor Protection
A Spectral Element Method for Nonlinear and Dispersive Water Waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Bigoni, Daniele; Eskilsson, Claes
The use of flexible mesh discretisation methods are important for simulation of nonlinear wave-structure interactions in offshore and marine settings such as harbour and coastal areas. For real applications, development of efficient models for wave propagation based on unstructured discretisation...... methods is of key interest. We present a high-order general-purpose three-dimensional numerical model solving fully nonlinear and dispersive potential flow equations with a free surface.......The use of flexible mesh discretisation methods are important for simulation of nonlinear wave-structure interactions in offshore and marine settings such as harbour and coastal areas. For real applications, development of efficient models for wave propagation based on unstructured discretisation...
Implementation of a strain energy-based nonlinear finite element in the object-oriented environment
Wegner, Tadeusz; Pęczak, Andrzej
2010-03-01
The objective of the paper is to describe a novel finite element computational method based on a strain energy density function and to implement it in the object-oriented environment. The original energy-based finite element was put into the known standard framework of classes and handled in a different manner. The nonlinear properties of material are defined with a modified strain energy density function. The local relaxation procedure proposed as a method used to resolve a nonlinear problem is implemented in C++ language. The hexahedral element with eight nodes as well as the adaptation of the nonlinear finite element is introduced. The chosen numerical model is made of nearly incompressible hyperelastic material. The application of the proposed element is shown on the example of a rectangular parallelepiped with a hollow port.
A sandwich bar element for geometric nonlinear thermo-elastic analysis
Directory of Open Access Journals (Sweden)
Murín J.
2008-11-01
Full Text Available This contribution deals with a two-node straight sandwich composite bar element with constant double symmetric rectangular cross-sectional area. This new bar element (based on the non-linear second-order theory is intended to perform the non-incremental full geometric non-linear analysis. Stiffness matrix of this composite bar contains transfer constants, which accurately describe polynomial uniaxial variation of the material thermo-physical properties.In the numerical experiments the weak coupled thermo-structural geometric non-linear problem was solved. Obtained results were compared with several analyses made by ANSYS programme. Findings show good accuracy of this new finite element. The results obtained with this element do not depend on the element mesh density.
Evaluation of a Nonlinear Finite Element Program - ABAQUS.
1983-03-15
shell elements) - Pipe elements with the effect of internal pressure Materials - A hypoelastic model for soils - Modified Cam Clay model - ORNL creep...is a lack of representation of different elements or material models . Furthermore, the manual that the reviewer has is in a rough draft form which... models (or routines) can be called to generate the material stiffness matrix D: • MATELA - Linearly elastic materials with isotropic, orthotropic and
Nonlinear dynamics of planetary gears using analytical and finite element models
Ambarisha, Vijaya Kumar; Parker, Robert G.
2007-05-01
Vibration-induced gear noise and dynamic loads remain key concerns in many transmission applications that use planetary gears. Tooth separations at large vibrations introduce nonlinearity in geared systems. The present work examines the complex, nonlinear dynamic behavior of spur planetary gears using two models: (i) a lumped-parameter model, and (ii) a finite element model. The two-dimensional (2D) lumped-parameter model represents the gears as lumped inertias, the gear meshes as nonlinear springs with tooth contact loss and periodically varying stiffness due to changing tooth contact conditions, and the supports as linear springs. The 2D finite element model is developed from a unique finite element-contact analysis solver specialized for gear dynamics. Mesh stiffness variation excitation, corner contact, and gear tooth contact loss are all intrinsically considered in the finite element analysis. The dynamics of planetary gears show a rich spectrum of nonlinear phenomena. Nonlinear jumps, chaotic motions, and period-doubling bifurcations occur when the mesh frequency or any of its higher harmonics are near a natural frequency of the system. Responses from the dynamic analysis using analytical and finite element models are successfully compared qualitatively and quantitatively. These comparisons validate the effectiveness of the lumped-parameter model to simulate the dynamics of planetary gears. Mesh phasing rules to suppress rotational and translational vibrations in planetary gears are valid even when nonlinearity from tooth contact loss occurs. These mesh phasing rules, however, are not valid in the chaotic and period-doubling regions.
Advance elements of optoisolation circuits nonlinearity applications in engineering
Aluf, Ofer
2017-01-01
This book on advanced optoisolation circuits for nonlinearity applications in engineering addresses two separate engineering and scientific areas, and presents advanced analysis methods for optoisolation circuits that cover a broad range of engineering applications. The book analyzes optoisolation circuits as linear and nonlinear dynamical systems and their limit cycles, bifurcation, and limit cycle stability by using Floquet theory. Further, it discusses a broad range of bifurcations related to optoisolation systems: cusp-catastrophe, Bautin bifurcation, Andronov-Hopf bifurcation, Bogdanov-Takens (BT) bifurcation, fold Hopf bifurcation, Hopf-Hopf bifurcation, Torus bifurcation (Neimark-Sacker bifurcation), and Saddle-loop or Homoclinic bifurcation. Floquet theory helps as to analyze advance optoisolation systems. Floquet theory is the study of the stability of linear periodic systems in continuous time. Another way to describe Floquet theory, it is the study of linear systems of differential equations with p...
Elements of nonlinear time series analysis and forecasting
De Gooijer, Jan G
2017-01-01
This book provides an overview of the current state-of-the-art of nonlinear time series analysis, richly illustrated with examples, pseudocode algorithms and real-world applications. Avoiding a “theorem-proof” format, it shows concrete applications on a variety of empirical time series. The book can be used in graduate courses in nonlinear time series and at the same time also includes interesting material for more advanced readers. Though it is largely self-contained, readers require an understanding of basic linear time series concepts, Markov chains and Monte Carlo simulation methods. The book covers time-domain and frequency-domain methods for the analysis of both univariate and multivariate (vector) time series. It makes a clear distinction between parametric models on the one hand, and semi- and nonparametric models/methods on the other. This offers the reader the option of concentrating exclusively on one of these nonlinear time series analysis methods. To make the book as user friendly as possible...
Ender, I. A.; Bakaleinikov, L. A.; Flegontova, E. Yu.; Gerasimenko, A. B.
2017-08-01
We have proposed an algorithm for the sequential construction of nonisotropic matrix elements of the collision integral, which are required to solve the nonlinear Boltzmann equation using the moments method. The starting elements of the matrix are isotropic and assumed to be known. The algorithm can be used for an arbitrary law of interactions for any ratio of the masses of colliding particles.
A stabilised nodal spectral element method for fully nonlinear water waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Eskilsson, C.; Bigoni, Daniele
2016-01-01
We present an arbitrary-order spectral element method for general-purpose simulation of non-overturning water waves, described by fully nonlinear potential theory. The method can be viewed as a high-order extension of the classical finite element method proposed by Cai et al. (1998) [5], although...... the numerical implementation differs greatly. Features of the proposed spectral element method include: nodal Lagrange basis functions, a general quadrature-free approach and gradient recovery using global L2 projections. The quartic nonlinear terms present in the Zakharov form of the free surface conditions...
Introduction to the Explicit Finite Element Method for Nonlinear Transient Dynamics
Wu, Shen R
2012-01-01
A systematic introduction to the theories and formulations of the explicit finite element method As numerical technology continues to grow and evolve with industrial applications, understanding the explicit finite element method has become increasingly important, particularly in the areas of crashworthiness, metal forming, and impact engineering. Introduction to the Explicit FiniteElement Method for Nonlinear Transient Dynamics is the first book to address specifically what is now accepted as the most successful numerical tool for nonlinear transient dynamics. The book aids readers in master
Domain decomposition based iterative methods for nonlinear elliptic finite element problems
Energy Technology Data Exchange (ETDEWEB)
Cai, X.C. [Univ. of Colorado, Boulder, CO (United States)
1994-12-31
The class of overlapping Schwarz algorithms has been extensively studied for linear elliptic finite element problems. In this presentation, the author considers the solution of systems of nonlinear algebraic equations arising from the finite element discretization of some nonlinear elliptic equations. Several overlapping Schwarz algorithms, including the additive and multiplicative versions, with inexact Newton acceleration will be discussed. The author shows that the convergence rate of the Newton`s method is independent of the mesh size used in the finite element discretization, and also independent of the number of subdomains into which the original domain in decomposed. Numerical examples will be presented.
SEACAS Theory Manuals: Part III. Finite Element Analysis in Nonlinear Solid Mechanics
Energy Technology Data Exchange (ETDEWEB)
Laursen, T.A.; Attaway, S.W.; Zadoks, R.I.
1999-03-01
This report outlines the application of finite element methodology to large deformation solid mechanics problems, detailing also some of the key technological issues that effective finite element formulations must address. The presentation is organized into three major portions: first, a discussion of finite element discretization from the global point of view, emphasizing the relationship between a virtual work principle and the associated fully discrete system, second, a discussion of finite element technology, emphasizing the important theoretical and practical features associated with an individual finite element; and third, detailed description of specific elements that enjoy widespread use, providing some examples of the theoretical ideas already described. Descriptions of problem formulation in nonlinear solid mechanics, nonlinear continuum mechanics, and constitutive modeling are given in three companion reports.
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...
A hybrid-stress solid-shell element for non-linear analysis of piezoelectric structures
Institute of Scientific and Technical Information of China (English)
SZE; K; Y
2009-01-01
This paper presents eight-node solid-shell elements for geometric non-linear analyze of piezoelectric structures. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger-Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid ele- ment, a hybrid-stress solid-shell element is formulated. The presented finite shell element is able to model arbitrary curved shell structures. Non-linear numerical examples demonstrate the ability of the proposed model to analyze nonlinear piezoelectric devices.
On the Possibility of Using Nonlinear Elements for Landau Damping in High-Intensity Beams
Energy Technology Data Exchange (ETDEWEB)
Alexahin, Y. [Fermilab; Gianfelice-Wendt, E. [Fermilab; Lebedev, V. [Fermilab; Valishev, A. [Fermilab
2016-09-30
Direct space-charge force shifts incoherent tunes downwards from the coherent ones breaking the Landau mechanism of coherent oscillations damping at high beam intensity. To restore it nonlinear elements can be employed which move back tunes of large amplitude particles. In the present report we consider the possibility of creating a “nonlinear integrable optics” insertion in the Fermilab Recycler to host either octupoles or hollow electron lens for this purpose. For comparison we also consider the classic scheme with distributed octupole families. It is shown that for the Proton Improvement Plan II (PIP II) parameters the required nonlinear tune shift can be created without destroying the dynamic aperture.
Wang, Qing; Yao, Jing-Zheng
2010-12-01
Several algorithms were proposed relating to the development of a framework of the perturbation-based stochastic finite element method (PSFEM) for large variation nonlinear dynamic problems. For this purpose, algorithms and a framework related to SFEM based on the stochastic virtual work principle were studied. To prove the validity and practicality of the algorithms and framework, numerical examples for nonlinear dynamic problems with large variations were calculated and compared with the Monte-Carlo Simulation method. This comparison shows that the proposed approaches are accurate and effective for the nonlinear dynamic analysis of structures with random parameters.
Quadratic solid-shell elements for nonlinear structural analysis and sheet metal forming simulation
Wang, Peng; Chalal, Hocine; Abed-Meraim, Farid
2017-01-01
In this paper, two quadratic solid-shell (SHB) elements are proposed for the three-dimensional modeling of thin structures. These consist of a 20-node hexahedral solid-shell element, denoted SHB20, and its 15-node prismatic counterpart, denoted SHB15. The formulation of these elements is extended in this work to include geometric and material nonlinearities, for application to problems involving large displacements and rotations as well as plasticity. For this purpose, the SHB elements are coupled with large-strain anisotropic elasto-plastic constitutive equations for metallic materials. Although based on a purely three-dimensional approach, several modifications are introduced in the formulation of these elements to provide them with interesting shell features. In particular, a special direction is chosen to represent the thickness, along which a user-defined number of integration points are located. Furthermore, for efficiency requirements and for alleviating locking phenomena, an in-plane reduced-integration scheme is adopted. The resulting formulations are implemented into the finite element software ABAQUS/Standard and, to assess their performance, a variety of nonlinear benchmark problems are investigated. Attention is then focused on the simulation of various complex sheet metal forming processes, involving large strain, anisotropic plasticity, and double-sided contact. From all simulation results, it appears that the SHB elements represent an interesting alternative to traditional shell and solid elements, due to their versatility and capability of accurately modeling selective nonlinear benchmark problems as well as complex sheet metal forming processes.
Quadratic solid-shell elements for nonlinear structural analysis and sheet metal forming simulation
Wang, Peng; Chalal, Hocine; Abed-Meraim, Farid
2016-10-01
In this paper, two quadratic solid-shell (SHB) elements are proposed for the three-dimensional modeling of thin structures. These consist of a 20-node hexahedral solid-shell element, denoted SHB20, and its 15-node prismatic counterpart, denoted SHB15. The formulation of these elements is extended in this work to include geometric and material nonlinearities, for application to problems involving large displacements and rotations as well as plasticity. For this purpose, the SHB elements are coupled with large-strain anisotropic elasto-plastic constitutive equations for metallic materials. Although based on a purely three-dimensional approach, several modifications are introduced in the formulation of these elements to provide them with interesting shell features. In particular, a special direction is chosen to represent the thickness, along which a user-defined number of integration points are located. Furthermore, for efficiency requirements and for alleviating locking phenomena, an in-plane reduced-integration scheme is adopted. The resulting formulations are implemented into the finite element software ABAQUS/Standard and, to assess their performance, a variety of nonlinear benchmark problems are investigated. Attention is then focused on the simulation of various complex sheet metal forming processes, involving large strain, anisotropic plasticity, and double-sided contact. From all simulation results, it appears that the SHB elements represent an interesting alternative to traditional shell and solid elements, due to their versatility and capability of accurately modeling selective nonlinear benchmark problems as well as complex sheet metal forming processes.
Eye/Sensor Protection against Laser Irradiation Organic Nonlinear Optical Materials
1989-06-12
Recent developments in organic nonlinear optical materials for application to eye and sensor protection are reviewed. This compendium includes a...noteworthy organic third-order nonlinear optical materials is included as an appendix. Lasers are playing an important and increasing role in modern
Material nonlinear analysis via mixed-iterative finite element method
Sutjahjo, Edhi; Chamis, Christos C.
1992-01-01
The performance of elastic-plastic mixed-iterative analysis is examined through a set of convergence studies. Membrane and bending behaviors are tested using 4-node quadrilateral finite elements. The membrane result is excellent, which indicates the implementation of elastic-plastic mixed-iterative analysis is appropriate. On the other hand, further research to improve bending performance of the method seems to be warranted.
GEOMETRICALLY NONLINEAR FE FORMULATIONS FOR THE MACRO-ELEMENT UNIPLET OF FOLDABLE STRUCTURES
Institute of Scientific and Technical Information of China (English)
陈务军; 付功义; 何艳丽; 董石麟
2002-01-01
Geometrically nonlinear stiffness matrix due to large displacement-small strain was firstly formulated ex-plicitly for the basic components of pantographic foldable structures,namely, the uniplet, derived from a three-node beam element. The formulation of the uniplet stiffness matrix is based on the precise nonlinear finite elementtheory and the displacement-harmonized and internal force constraints are applied directly to the deformationmodes of the three-node beam element. The formulations were derived in general form, and can be simplified forparticular foldable structures, such as flat, cylindrical and spherical structures. Finally, two examples were pre-sented to illustrate the applications of the stiffness matrix evolved.
Directory of Open Access Journals (Sweden)
G. Wollenberg
2004-01-01
Full Text Available An interconnection system whose loads protected by a voltage suppressor and a low-pass filter against overvoltages caused by coupling pulse-shaped electromagnetic waves is analyzed. The external wave influencing the system is assumed as a plane wave with HPM form. The computation is provided by a full-wave PEEC model for the interconnection structure incorporated in the SPICE code. Thus, nonlinear elements of the protection circuit can be included in the calculation. The analysis shows intermodulation distortions and penetrations of low frequency interferences caused by intermodulations through the protection circuits. The example examined shows the necessity of using full-wave models for interconnections together with non-linear circuit solvers for simulation of noise immunity in systems protected by nonlinear devices.
Nonlinear Finite Element Analysis of Pull-Out Test
DEFF Research Database (Denmark)
Saabye Ottesen, N
1981-01-01
A specific pull-out test used to determine in-situ concrete compressive strength is analyzed. This test consists of a steel disc that is extracted from the structure. The finite element analysis considers cracking as well as strain hardening and softening in the pre- and post-failure region......, respectively. The aim is to attain a clear insight into structural behavior. Special attention is given to the failure mode. Severe cracking occurs and the stress distribution is very inhomogeneous. However, large compressive forces run from the disc in a rather narrow band towards the support...
Taylor, Z A; Cheng, M; Ourselin, S
2008-05-01
The use of biomechanical modelling, especially in conjunction with finite element analysis, has become common in many areas of medical image analysis and surgical simulation. Clinical employment of such techniques is hindered by conflicting requirements for high fidelity in the modelling approach, and fast solution speeds. We report the development of techniques for high-speed nonlinear finite element analysis for surgical simulation. We use a fully nonlinear total Lagrangian explicit finite element formulation which offers significant computational advantages for soft tissue simulation. However, the key contribution of the work is the presentation of a fast graphics processing unit (GPU) solution scheme for the finite element equations. To the best of our knowledge, this represents the first GPU implementation of a nonlinear finite element solver. We show that the present explicit finite element scheme is well suited to solution via highly parallel graphics hardware, and that even a midrange GPU allows significant solution speed gains (up to 16.8 x) compared with equivalent CPU implementations. For the models tested the scheme allows real-time solution of models with up to 16,000 tetrahedral elements. The use of GPUs for such purposes offers a cost-effective high-performance alternative to expensive multi-CPU machines, and may have important applications in medical image analysis and surgical simulation.
Two-Dimensional Nonlinear Finite Element Analysis of CMC Microstructures
Mital, Subodh K.; Goldberg, Robert K.; Bonacuse, Peter J.
2012-01-01
A research program has been developed to quantify the effects of the microstructure of a woven ceramic matrix composite and its variability on the effective properties and response of the material. In order to characterize and quantify the variations in the microstructure of a five harness satin weave, chemical vapor infiltrated (CVI) SiC/SiC composite material, specimens were serially sectioned and polished to capture images that detailed the fiber tows, matrix, and porosity. Open source quantitative image analysis tools were then used to isolate the constituents, from which two dimensional finite element models were generated which approximated the actual specimen section geometry. A simplified elastic-plastic model, wherein all stress above yield is redistributed to lower stress regions, is used to approximate the progressive damage behavior for each of the composite constituents. Finite element analyses under in-plane tensile loading were performed to examine how the variability in the local microstructure affected the macroscopic stress-strain response of the material as well as the local initiation and progression of damage. The macroscopic stress-strain response appeared to be minimally affected by the variation in local microstructure, but the locations where damage initiated and propagated appeared to be linked to specific aspects of the local microstructure.
Duan, M.
2004-12-01
In this paper, a geometrically nonlinear hybrid/mixed curved quadrilateral shell element (HMSHEL4N) with four nodes is developed based on the modified Hellinger/Reissner variational principles. The performance of element is investigated and tested using some benchmark problems. A number of numerical examples of plate and shell nonlinear deflection problems are included. The results are compared with theoretical solutions and other numerical results. It is shown that HMSHEL4N does not possess spurious zero energy modes and any locking phenomenon, and is convergent and insensitive to the distorted mesh. A good agreement of the results with theoretical solutions, and better performance compared with displacement finite element method, are observed. It is seen that an efficient shell element based on stress and displacement field assumptions in solution and time is obtained.
A Stabilised Nodal Spectral Element Method for Fully Nonlinear Water Waves
Engsig-Karup, Allan Peter; Bigoni, Daniele
2015-01-01
We present an arbitrary-order spectral element method for general-purpose simulation of non-overturning water waves, described by fully nonlinear potential theory. The method can be viewed as a high-order extension of the classical finite element method proposed by Cai et al (1998) \\cite{CaiEtAl1998}, although the numerical implementation differs greatly. Features of the proposed spectral element method include: nodal Lagrange basis functions, a general quadrature-free approach and gradient recovery using global $L^2$ projections. The quartic nonlinear terms present in the Zakharov form of the free surface conditions can cause severe aliasing problems and consequently numerical instability for marginally resolved or very steep waves. We show how the scheme can be stabilised through a combination of over-integration of the Galerkin projections and a mild spectral filtering on a per element basis. This effectively removes any aliasing driven instabilities while retaining the high-order accuracy of the numerical...
Vismara, S. O.; Ricci, S.; Bellini, M.; Trittoni, L.
2016-06-01
The objective of the present paper is to describe a procedure to identify and model the non-linear behaviour of structural elements. The procedure herein applied can be divided into two main steps: the system identification and the finite element model updating. The application of the restoring force surface method as a strategy to characterize and identify localized non-linearities has been investigated. This method, which works in the time domain, has been chosen because it has `built-in' characterization capabilities, it allows a direct non-parametric identification of non-linear single-degree-of-freedom systems and it can easily deal with sine-sweep excitations. Two different application examples are reported. At first, a numerical test case has been carried out to investigate the modelling techniques in the case of non-linear behaviour based on the presence of a free-play in the model. The second example concerns the flap of the Intermediate eXperimental Vehicle that successfully completed its 100-min mission on 11 February 2015. The flap was developed under the responsibility of Thales Alenia Space Italia, the prime contractor, which provided the experimental data needed to accomplish the investigation. The procedure here presented has been applied to the results of modal testing performed on the article. Once the non-linear parameters were identified, they were used to update the finite element model in order to prove its capability of predicting the flap behaviour for different load levels.
Institute of Scientific and Technical Information of China (English)
Dongyang Shi; Haihong Wang; Yuepeng Du
2009-01-01
An anisotropic nonconforming finite element method is presented for a class of nonlinear Sobolev equations. The optimal error estimates and supercloseness are obtained for both semi-discrete and fully-discrete approximate schemes, which are the same as the traditional finite element methods. In addition, the global superconvergence is derived through the postprocessing technique. Numerical experiments are included to illustrate the feasibility of the proposed method.
Validation of Finite Element Solutions of Nonlinear, Periodic Eddy Current Problems
Directory of Open Access Journals (Sweden)
Plasser René
2014-12-01
Full Text Available An industrial application is presented to validate a finite element analysis of 3-dimensional, nonlinear eddy-current problems with periodic excitation. The harmonic- balance method and the fixed-point technique are applied to get the steady state solution using the finite element method. The losses occurring in steel reinforcements underneath a reactor due to induced eddy-currents are computed and compared to measurements.
Indian Academy of Sciences (India)
Fatih Goktepe; H Serdar Kuyuk; Erkan Celebi
2014-04-01
Earthquakes have caused colossal casualties and severe damages to engineering structures and especially leading to substantial economic loss to the underground structures and/or infrastructures. Pipelines are one of most important component of lifeline engineering. For instance, the Southern Caucasus- Eastern Turkey energy corridors are formed by several key pipelines carrying crude oil and natural gas from Azerbaijan, via Georgia, to world markets through Mediterranean Sea. Many project accomplished recently and construction of new corridors are still going on. They should be protected from earthquake disaster especially when they pass through high seismicity zones. The installation of wave impeding barriers (WIB) below the vulnerable infrastructures as pipelines established in soft soil can be used to reduce the effect of the earthquake induced ground borne vibrations. In this paper, a WIB as artificial bedrock based on the cut-off frequency of a soil layer over bedrock is proposed as isolation measurement in order to mitigate the dynamic response of the buried pipelines under earthquake strong ground motion. The computational simulation of the wave propagation problem is directly achieved by employing nonlinear 2D finite element modelling for prediction of screening performance of WIB on the dynamic response of vibrating coupled soil-pipeline system. Energy absorbing boundaries along the truncated interfaces of the unbounded nature of the underlying soil media are implemented in the time domain along with Newmark’s integration. An extensive parametric investigation and systematic computations are performed with different controlling parameters. The obtained numerical results point out that WIB can be very promising as an isolator to protect pipelines when they establish for a certain depth.
On high-continuity transfinite element formulations for linear-nonlinear transient thermal problems
Tamma, Kumar K.; Railkar, Sudhir B.
1987-01-01
This paper describes recent developments in the applicability of a hybrid transfinite element methodology with emphasis on high-continuity formulations for linear/nonlinear transient thermal problems. The proposed concepts furnish accurate temperature distributions and temperature gradients making use of a relatively smaller number of degrees of freedom; and the methodology is applicable to linear/nonlinear thermal problems. Characteristic features of the formulations are described in technical detail as the proposed hybrid approach combines the major advantages and modeling features of high-continuity thermal finite elements in conjunction with transform methods and classical Galerkin schemes. Several numerical test problems are evaluated and the results obtained validate the proposed concepts for linear/nonlinear thermal problems.
A SIMPLE FINITE ELEMENT FOR NON-LINEAR ANALYSIS OF COMPOSITE PLATES
Directory of Open Access Journals (Sweden)
V.B. Tungikar
2011-06-01
Full Text Available Finite Element Analysis for geometrically nonlinear behaviour of laminated composite plates is presented andcompared with the reported investigations. However structural non-linearity is encountered in certain cases andneeds attention. A higher order displacement field that accounts for transverse shear effects under geometricnonlinear condition is employed in the formulation of a four node, rectangular, element with thirteen degrees offreedom per node. First order Zigzag terms have been included in displacement field for improvement in theresponse. Von Karman strain approach is considered in the present analysis. Incremental Pica iterative scheme isused to solve resulting nonlinear equilibrium equations. The formulation demonstrates its excellence in theperformance for predicting response at various lay ups and plies conditions.
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.
Stupishin, L.; Nikitin, K.; Kolesnikov, A.
2017-05-01
A methodology for shell stability research and determining buckling load, based on the mixed finite element method are proposed. Axisymmetric geometrically nonlinear shallow shells made of orthotropic material are considered. The results of numerical research of stability by changing the shape of shells, ratio of elastic modulus of the material and parameters of the support contour are presented.
A Taylor-Galerkin finite element algorithm for transient nonlinear thermal-structural analysis
Thornton, E. A.; Dechaumphai, P.
1986-01-01
A Taylor-Galerkin finite element method for solving large, nonlinear thermal-structural problems is presented. The algorithm is formulated for coupled transient and uncoupled quasistatic thermal-structural problems. Vectorizing strategies ensure computational efficiency. Two applications demonstrate the validity of the approach for analyzing transient and quasistatic thermal-structural problems.
Ultimate limit state design of sheet pile walls by finite elements and nonlinear programming
DEFF Research Database (Denmark)
Krabbenhøft, Kristian; Damkilde, Lars; Krabbenhøft, Sven
2005-01-01
as a nonlinear programming problem where the yield moment of the wall is minimized subject to equilibrium and yield conditions. The finite element discretization used enables exact fulfillment of these conditions and thus, according to the lower bound theorem, the solutions are safe....
Ultimate Limit State Design Of Sheet Pile Walls By Finite Elements And Nonlinear Programming
DEFF Research Database (Denmark)
Krabbenhøft, Kristian; Damkilde, Lars; Krabbenhøft, Sven
2005-01-01
as a nonlinear programming problem where the yield moment of the wall is minimized subject to equilibrium and yield conditions. The finite element discretization used enables exact fulfillment of these conditions and thus, according to the lower bound theorem, the solutions are safe...
THE EFFECT OF NUMERICAL INTEGRATION IN FINITE ELEMENT METHODS FOR NONLINEAR PARABOLIC EQUATIONS
Institute of Scientific and Technical Information of China (English)
N＇guimbi; Germain
2001-01-01
Abstract. The effect of numerical integration in finite element methods applied to a class of nonlinear parabolic equations is considered and some sufficient conditions on the quadrature scheme to ensure that the order of convergence is unaltered in the presence of numerical integration are given. Optimal Lz and H1 estimates for the error and its time derivative are established.
COYOTE: a finite-element computer program for nonlinear heat-conduction problems
Energy Technology Data Exchange (ETDEWEB)
Gartling, D.K.
1982-10-01
COYOTE is a finite element computer program designed for the solution of two-dimensional, nonlinear heat conduction problems. The theoretical and mathematical basis used to develop the code is described. Program capabilities and complete user instructions are presented. Several example problems are described in detail to demonstrate the use of the program.
The Superconvergence of Mixed Finite Element Methods for Nonlinear Hyperbolic Equations
Institute of Scientific and Technical Information of China (English)
YanpingCHEN; YunqingHUANG
1998-01-01
Imprioved L2-error estimates are computed for mixed finte element methods for second order nonlinear hyperbolic equations.Superconvergence results,L∞ in time and discrete L2 in space,are derived for both the solution and gradients on the rectangular domain.Results are given for the continuous-time case.
Rahman, T.; Jansen, E.L.; Tiso, P.
2011-01-01
In this paper, a finite element-based approach for nonlinear vibration analysis of shell structures is presented. The approach makes use of a perturbation method that gives an approximation for the amplitude-frequency relation of the structure. The method is formulated using a functional notation an
Nonlinear finite-element analysis and biomechanical evaluation of the lumbar spine
DEFF Research Database (Denmark)
Wong, Christian; Gehrchen, P Martin; Darvann, Tron;
2003-01-01
A finite-element analysis (FEA) model of an intact lumbar disc-body unit was generated. The vertebral body of the FEA model consisted of a solid tetrahedral core of trabecular bone surrounded by a cortical shell. The disc consisted of an incompressible nucleus surrounded by nonlinear annulus fibers...
Rahman, T.; Jansen, E.L.; Tiso, P.
2011-01-01
In this paper, a finite element-based approach for nonlinear vibration analysis of shell structures is presented. The approach makes use of a perturbation method that gives an approximation for the amplitude-frequency relation of the structure. The method is formulated using a functional notation
Dielectric strength test to protection elements for live lines works
Directory of Open Access Journals (Sweden)
Carlos Eduardo Pinto-Salamanca
2017-06-01
Full Text Available This paper presents the design and assembly of a system of tests of sustained voltage to elements and equipment used in live line maneuvers through tests on gloves and dielectric rods, as these are the first points of contact to ensure safe operations. It means an advance for the creation of a laboratory certified in this type of tests at Universidad Pedagógica y Tecnológica de Colombia (UPTC Faculty of Duitama, considering that currently there are not laboratories that provide this service in Boyacá and Casanare. Dielectric strength tests were performed on personal protection elements and equipment under the parameters of ASTM D120, ASTM F496, ISO 60903, ASTM-F711 and IEEE 978, developing an assembly for testing gloves and dielectric rods with voltage levels up to 15 kV. The results validate the proposed system to outlook of circuit design and implementation, where tests were performed to establish dielectric capacities, in operating under open circuit conditions, with resistive load or short circuit. The compliance with the regulations established under the test sequences of safety parameters for the system and the follow-up to the tests was verified through the use of a management system for the generation of concepts of approval or rejection of the tested elements.
Simulation of 3D tumor cell growth using nonlinear finite element method.
Dong, Shoubing; Yan, Yannan; Tang, Liqun; Meng, Junping; Jiang, Yi
2016-01-01
We propose a novel parallel computing framework for a nonlinear finite element method (FEM)-based cell model and apply it to simulate avascular tumor growth. We derive computation formulas to simplify the simulation and design the basic algorithms. With the increment of the proliferation generations of tumor cells, the FEM elements may become larger and more distorted. Then, we describe a remesh and refinement processing of the distorted or over large finite elements and the parallel implementation based on Message Passing Interface to improve the accuracy and efficiency of the simulation. We demonstrate the feasibility and effectiveness of the FEM model and the parallelization methods in simulations of early tumor growth.
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.
Institute of Scientific and Technical Information of China (English)
QIN Xinqiang; MA Yichen; GONG Chunqiong
2004-01-01
A two-grid method for solving nonlinear convection-dominated diffusion equations is presented. The method use discretizations based on a characteristic mixed finite-element method and give the linearization for nonlinear systems by two steps. The error analysis shows that the two-grid scheme combined with the characteristic mixed finite-element method can decrease numerical oscillation caused by dominated convections and solve nonlinear advection-dominated diffusion problems efficiently.
A URI 4-NODE QUADRILATERAL ELEMENT BY ASSUMED STRAIN METHOD FOR NONLINEAR PROBLEMS
Institute of Scientific and Technical Information of China (English)
WANG Jinyan; CHEN Jun; LI Minghui
2004-01-01
In this paper one-point quadrature "assumed strain" mixed element formulation based on the Hu-Washizu variational principle is presented. Special care is taken to avoid hourglass modes and volumetric locking as well as shear locking. The assumed strain fields are constructed so that those portions of the fields which lead to volumetric and shear locking phenomena are eliminated by projection, while the implementation of the proposed URI scheme is straightforward to suppress hourglass modes. In order to treat geometric nonlinearities simply and efficiently, a corotational coordinate system is used. Several numerical examples are given to demonstrate the performance of the suggested formulation, including nonlinear static/dynamic mechanical problems.
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...
Slope Safety Factor Calculations With Non-Linear Yield Criterion Using Finite Elements
DEFF Research Database (Denmark)
Clausen, Johan; Damkilde, Lars
2006-01-01
The factor of safety for a slope is calculated with the finite element method using a non-linear yield criterion of the Hoek-Brown type. The parameters of the Hoek-Brown criterion are found from triaxial test data. Parameters of the linear Mohr-Coulomb criterion are calibrated to the same triaxial...... are carried out at much higher stress levels than present in a slope failure, this leads to the conclusion that the use of the non-linear criterion leads to a safer slope design...
Slope Safety Factor Calculations With Non-Linear Yield Criterion Using Finite Elements
DEFF Research Database (Denmark)
Clausen, Johan Christian; Damkilde, Lars
2006-01-01
The factor of safety for a slope is calculated with the finite element method using a non-linear yield criterion of the Hoek-Brown type. The parameters of the Hoek-Brown criterion are found from triaxial test data. Parameters of the linear Mohr-Coulomb criterion are calibrated to the same triaxial...... are carried out at much higher stress levels than present in a slope failure, this leads to the conclusion that the use of the non-linear criterion leads to a safer slope design....
Guermond, Jean-Luc
2014-01-01
© 2014 Society for Industrial and Applied Mathematics. This paper proposes an explicit, (at least) second-order, maximum principle satisfying, Lagrange finite element method for solving nonlinear scalar conservation equations. The technique is based on a new viscous bilinear form introduced in Guermond and Nazarov [Comput. Methods Appl. Mech. Engrg., 272 (2014), pp. 198-213], a high-order entropy viscosity method, and the Boris-Book-Zalesak flux correction technique. The algorithm works for arbitrary meshes in any space dimension and for all Lipschitz fluxes. The formal second-order accuracy of the method and its convergence properties are tested on a series of linear and nonlinear benchmark problems.
Slope Safety Factor Calculations With Non-Linear Yield Criterion Using Finite Elements
DEFF Research Database (Denmark)
Clausen, Johan Christian; Damkilde, Lars
2006-01-01
The factor of safety for a slope is calculated with the finite element method using a non-linear yield criterion of the Hoek-Brown type. The parameters of the Hoek-Brown criterion are found from triaxial test data. Parameters of the linear Mohr-Coulomb criterion are calibrated to the same triaxial...... are carried out at much higher stress levels than present in a slope failure, this leads to the conclusion that the use of the non-linear criterion leads to a safer slope design....
Slope Safety Factor Calculations With Non-Linear Yield Criterion Using Finite Elements
DEFF Research Database (Denmark)
Clausen, Johan; Damkilde, Lars
2006-01-01
The factor of safety for a slope is calculated with the finite element method using a non-linear yield criterion of the Hoek-Brown type. The parameters of the Hoek-Brown criterion are found from triaxial test data. Parameters of the linear Mohr-Coulomb criterion are calibrated to the same triaxial...... are carried out at much higher stress levels than present in a slope failure, this leads to the conclusion that the use of the non-linear criterion leads to a safer slope design...
Wang, X.; Zheng, G. T.
2016-02-01
A simple and general Equivalent Dynamic Stiffness Mapping technique is proposed for identifying the parameters or the mathematical model of a nonlinear structural element with steady-state primary harmonic frequency response functions (FRFs). The Equivalent Dynamic Stiffness is defined as the complex ratio between the internal force and the displacement response of unknown element. Obtained with the test data of responses' frequencies and amplitudes, the real and imaginary part of Equivalent Dynamic Stiffness are plotted as discrete points in a three dimensional space over the displacement amplitude and the frequency, which are called the real and the imaginary Equivalent Dynamic Stiffness map, respectively. These points will form a repeatable surface as the Equivalent Dynamic stiffness is only a function of the corresponding data as derived in the paper. The mathematical model of the unknown element can then be obtained by surface-fitting these points with special functions selected by priori knowledge of the nonlinear type or with ordinary polynomials if the type of nonlinearity is not pre-known. An important merit of this technique is its capability of dealing with strong nonlinearities owning complicated frequency response behaviors such as jumps and breaks in resonance curves. In addition, this technique could also greatly simplify the test procedure. Besides there is no need to pre-identify the underlying linear parameters, the method uses the measured data of excitation forces and responses without requiring a strict control of the excitation force during the test. The proposed technique is demonstrated and validated with four classical single-degree-of-freedom (SDOF) numerical examples and one experimental example. An application of this technique for identification of nonlinearity from multiple-degree-of-freedom (MDOF) systems is also illustrated.
Bíró, Oszkár; Koczka, Gergely; Preis, Kurt
2014-05-01
An efficient finite element method to take account of the nonlinearity of the magnetic materials when analyzing three-dimensional eddy current problems is presented in this paper. The problem is formulated in terms of vector and scalar potentials approximated by edge and node based finite element basis functions. The application of Galerkin techniques leads to a large, nonlinear system of ordinary differential equations in the time domain. The excitations are assumed to be time-periodic and the steady-state periodic solution is of interest only. This is represented either in the frequency domain as a finite Fourier series or in the time domain as a set of discrete time values within one period for each finite element degree of freedom. The former approach is the (continuous) harmonic balance method and, in the latter one, discrete Fourier transformation will be shown to lead to a discrete harmonic balance method. Due to the nonlinearity, all harmonics, both continuous and discrete, are coupled to each other. The harmonics would be decoupled if the problem were linear, therefore, a special nonlinear iteration technique, the fixed-point method is used to linearize the equations by selecting a time-independent permeability distribution, the so-called fixed-point permeability in each nonlinear iteration step. This leads to uncoupled harmonics within these steps. As industrial applications, analyses of large power transformers are presented. The first example is the computation of the electromagnetic field of a single-phase transformer in the time domain with the results compared to those obtained by traditional time-stepping techniques. In the second application, an advanced model of the same transformer is analyzed in the frequency domain by the harmonic balance method with the effect of the presence of higher harmonics on the losses investigated. Finally a third example tackles the case of direct current (DC) bias in the coils of a single-phase transformer.
Directory of Open Access Journals (Sweden)
Zainorizuan Mohd Jaini
2013-12-01
Full Text Available Innovative technologies have resulted in more effective ceramic composite as high rate loading-resistance and protective layer. The ceramic composite layer consists of ceramic frontal plate that bonded by softer-strong reinforced polymer network, consequently gains the heterogeneous condition. These materials serve specific purposes of defeating high rate loading and maintaining the structural integrity of the layer. Further due to the lack of a constituent material and tedious problem in heterogonous material modelling, a numerical homogenization is employed to analyse the isotropic material properties of ceramic composite layer in homogenous manner. The objective of this study is to derive a constitutive law of the ceramic composite using the multi-scale analysis. Two-dimensional symmetric macrostructure of the ceramic composite was numerically modelled using the hybrid finite-discrete element method to investigate the effective material properties and strength profile. The macrostructure was modelled as brittle material with nonlinear material properties. The finite element method is incorporated with a Rankine-Rotating Crack approach and discrete element to model the fracture onset. The prescribed uniaxial and biaxial loadings were imposed along the free boundaries to create different deformations. Due to crack initiation on the macrostructure, the averaged stresses were calculated to plot the stress-strain curves and the effective yield stress surface. From the multi-scale analysis, the rate-dependency of Mohr-Coulomb constitutive law was derived for the ceramic composite layer.
Directory of Open Access Journals (Sweden)
Qi Song
2013-01-01
Full Text Available This paper proposes a partial refactorization for faster nonlinear analysis based on sparse matrix solution, which is nowadays the default solution choice in finite element analysis and can solve finite element models up to millions degrees of freedom. Among various fill-in’s reducing strategies for sparse matrix solution, the graph partition is in general the best in terms of resultant fill-ins and floating-point operations and furthermore produces a particular graph of sparse matrix that prevents local change of entries from wide spreading in factorization. Based on this feature, an explicit partial triangular refactorization with local change is efficiently constructed with limited additional storage requirement in row-sparse storage scheme. The partial refactorization of the changed stiffness matrix inherits a big percentage of the original factor and is carried out only on partial factor entries. The proposed method provides a new possibility for faster nonlinear analysis and is mainly suitable for material nonlinear problems and optimization problems. Compared to full factorization, it can significantly reduce the factorization time and can make nonlinear analysis more efficient.
Astroza, Rodrigo; Ebrahimian, Hamed; Conte, Joel P.
2015-03-01
This paper describes a novel framework that combines advanced mechanics-based nonlinear (hysteretic) finite element (FE) models and stochastic filtering techniques to estimate unknown time-invariant parameters of nonlinear inelastic material models used in the FE model. Using input-output data recorded during earthquake events, the proposed framework updates the nonlinear FE model of the structure. The updated FE model can be directly used for damage identification and further used for damage prognosis. To update the unknown time-invariant parameters of the FE model, two alternative stochastic filtering methods are used: the extended Kalman filter (EKF) and the unscented Kalman filter (UKF). A three-dimensional, 5-story, 2-by-1 bay reinforced concrete (RC) frame is used to verify the proposed framework. The RC frame is modeled using fiber-section displacement-based beam-column elements with distributed plasticity and is subjected to the ground motion recorded at the Sylmar station during the 1994 Northridge earthquake. The results indicate that the proposed framework accurately estimate the unknown material parameters of the nonlinear FE model. The UKF outperforms the EKF when the relative root-mean-square error of the recorded responses are compared. In addition, the results suggest that the convergence of the estimate of modeling parameters is smoother and faster when the UKF is utilized.
Tamma, Kumar K.; Railkar, Sudhir B.
1988-01-01
The present paper describes the applicability of hybrid transfinite element modeling/analysis formulations for nonlinear heat conduction problems involving phase change. The methodology is based on application of transform approaches and classical Galerkin schemes with finite element formulations to maintain the modeling versatility and numerical features for computational analysis. In addition, in conjunction with the above, the effects due to latent heat are modeled using enthalpy formulations to enable a physically realistic approximation to be dealt computationally for materials exhibiting phase change within a narrow band of temperatures. Pertinent details of the approach and computational scheme adapted are described in technical detail. Numerical test cases of comparative nature are presented to demonstrate the applicability of the proposed formulations for numerical modeling/analysis of nonlinear heat conduction problems involving phase change.
Nonlinear tracking in a diffusion process with a Bayesian filter and the finite element method
DEFF Research Database (Denmark)
Pedersen, Martin Wæver; Thygesen, Uffe Høgsbro; Madsen, Henrik
2011-01-01
A new approach to nonlinear state estimation and object tracking from indirect observations of a continuous time process is examined. Stochastic differential equations (SDEs) are employed to model the dynamics of the unobservable state. Tracking problems in the plane subject to boundaries...... become complicated using SMC because Monte Carlo randomness is introduced. The finite element (FE) method solves the Kolmogorov equations of the SDE numerically on a triangular unstructured mesh for which boundary conditions to the state-space are simple to incorporate. The FE approach to nonlinear state...... estimation is suited for off-line data analysis because the computed smoothed state densities, maximum a posteriori parameter estimates and state sequence are deterministic conditional on the finite element mesh and the observations. The proposed method is conceptually similar to existing point...
Directory of Open Access Journals (Sweden)
Husain M. Husain
2013-05-01
Full Text Available In this work a program is developed to carry out the nonlinear analysis (material nonlinearity of prestressed concrete beams using tendons of carbon fiber reinforced polymer (CFRP instead of steel. The properties of this material include high strength, light weight, and insusceptibility to corrosion and magnetism. This material is still under investigation, therefore it needs continuous work to make it beneficial in concrete design. Four beams which are tested experimentally by Yan et al. are examined by the developed computer program to reach a certain analytical approach of the design and analysis of such beams because there is no available restrictions or recommendations covering this material in the codes. The program uses the finite element analysis by dividing the beams into isoparametric 20-noded brick elements. The results obtained are good in comparison with experimental results.
Real-Time Nonlinear Finite Element Computations on GPU - Application to Neurosurgical Simulation.
Joldes, Grand Roman; Wittek, Adam; Miller, Karol
2010-12-15
Application of biomechanical modeling techniques in the area of medical image analysis and surgical simulation implies two conflicting requirements: accurate results and high solution speeds. Accurate results can be obtained only by using appropriate models and solution algorithms. In our previous papers we have presented algorithms and solution methods for performing accurate nonlinear finite element analysis of brain shift (which includes mixed mesh, different non-linear material models, finite deformations and brain-skull contacts) in less than a minute on a personal computer for models having up to 50.000 degrees of freedom. In this paper we present an implementation of our algorithms on a Graphics Processing Unit (GPU) using the new NVIDIA Compute Unified Device Architecture (CUDA) which leads to more than 20 times increase in the computation speed. This makes possible the use of meshes with more elements, which better represent the geometry, are easier to generate, and provide more accurate results.
Non-linear shape functions over time in the space-time finite element method
Directory of Open Access Journals (Sweden)
Kacprzyk Zbigniew
2017-01-01
Full Text Available This work presents a generalisation of the space-time finite element method proposed by Kączkowski in his seminal of 1970’s and early 1980’s works. Kączkowski used linear shape functions in time. The recurrence formula obtained by Kączkowski was conditionally stable. In this paper, non-linear shape functions in time are proposed.
Error estimations of mixed finite element methods for nonlinear problems of shallow shell theory
Karchevsky, M.
2016-11-01
The variational formulations of problems of equilibrium of a shallow shell in the framework of the geometrically and physically nonlinear theory by boundary conditions of different main types, including non-classical, are considered. Necessary and sufficient conditions for their solvability are derived. Mixed finite element methods for the approximate solutions to these problems based on the use of second derivatives of the bending as auxiliary variables are proposed. Estimations of accuracy of approximate solutions are established.
Przekop, Adam; Wu, Hsi-Yung T.; Shaw, Peter
2014-01-01
The Environmentally Responsible Aviation Project aims to develop aircraft technologies enabling significant fuel burn and community noise reductions. Small incremental changes to the conventional metallic alloy-based 'tube and wing' configuration are not sufficient to achieve the desired metrics. One of the airframe concepts that might dramatically improve aircraft performance is a composite-based hybrid wing body configuration. Such a concept, however, presents inherent challenges stemming from, among other factors, the necessity to transfer wing loads through the entire center fuselage section which accommodates a pressurized cabin confined by flat or nearly flat panels. This paper discusses a nonlinear finite element analysis of a large-scale test article being developed to demonstrate that the Pultruded Rod Stitched Efficient Unitized Structure concept can meet these challenging demands of the next generation airframes. There are specific reasons why geometrically nonlinear analysis may be warranted for the hybrid wing body flat panel structure. In general, for sufficiently high internal pressure and/or mechanical loading, energy related to the in-plane strain may become significant relative to the bending strain energy, particularly in thin-walled areas such as the minimum gage skin extensively used in the structure under analysis. To account for this effect, a geometrically nonlinear strain-displacement relationship is needed to properly couple large out-of-plane and in-plane deformations. Depending on the loading, this nonlinear coupling mechanism manifests itself in a distinct manner in compression- and tension-dominated sections of the structure. Under significant compression, nonlinear analysis is needed to accurately predict loss of stability and postbuckled deformation. Under significant tension, the nonlinear effects account for suppression of the out-of-plane deformation due to in-plane stretching. By comparing the present results with the previously
On the development of hierarchical solution strategies for nonlinear finite element formulations
Padovan, J.; Lackney, J.
1984-01-01
This paper develops a hierarchical type solution scheme which can handle the field equations associated with nonlinear finite element simulations. The overall procedure possesses various levels of application namely degree of freedom, nodal, elemental, substructural as well as global. In particular iteration, updating, assembly and solution control occurs at the various hierarchical levels. Due to the manner of formulation, the degree of matrix inversion depends on the size of the various hierarchical partitioned groups. In this context, degree of freedom partitioning requires no inversion. To benchmark the overall scheme, the results of several numerical examples are presented.
Padovan, Joe
1987-01-01
In a three-part series of papers, a generalized finite element analysis scheme is developed to handle the steady and transient response of moving/rolling nonlinear viscoelastic structure. This paper considers the development of the moving/rolling element strategy, including the effects of large deformation kinematics and viscoelasticity modeled by fractional integrodifferential operators. To improve the solution strategy, a special hierarchical constraint procedure is developed for the case of steady rolling/translating, as well as a transient scheme involving the use of a Grunwaldian representation of the fractional operator.
A refined mixed shear flexible finite element for the nonlinear analysis of laminated plates
Putcha, N. S.; Reddy, J. N.
1986-01-01
The present study is concerned with the development of a mixed shear flexible finite element with relaxed continuity for the geometrically linear and nonlinear analysis of laminated anisotropic plates. The formulation of the element is based on a refined higher-order theory. This theory satisfies the zero transverse shear stress boundary conditions on the top and bottom faces of the plate. Shear correction coefficients are not needed. The developed element consists of 11 degrees-of-freedom per node, taking into account three displacements, two rotations, and six moment resultants. An evaluation of the element is conducted with respect to the accuracy obtained in the bending of laminated anistropic rectangular plates with different lamination schemes, loadings, and boundary conditions.
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A.G. Sereda
2015-06-01
Full Text Available Purpose. Theoretical justification and engineering of induction motors heat protection method from overload currents taking into account nonlinear distortion of the phase current and implementation as a microprocessor device functioning algorithm. Methodology. To solve the problem used the theory of the representing complex harmonic oscillations analog signals expansion into the oscillation spectrum forming elementary harmonic components in order to compare their properties by applying the theory of discrete signals and systems, as well as methods of spectral analysis and discrete signals filtering. The harmonic analysis versatility is that any periodic signal may be synthesized from harmonic oscillation of certain amplitude, frequency and initial phase. A mathematical model for determining the phase current harmonic content of power supply networks with isolated neutral and non-linear loads types and, as a consequence, the distortion of sinusoidal phase current change is developed by multiplying the analog current in time dependency on the grate delta-function with different sampling intervals, in which the use of simple and widely used in relay protection units, in particular electronic overcurrent relays, mathematical operations of integration squares instantaneous current allows the most in harmony with the mathematical tools to build other network protection types. Findings. The necessity to increase the sensitivity of the induction motors heat protection from overload currents taking into account nonlinear distortion of the phase currents is proved. By nonlinear distortion harmonic analysis of the phase currents the motor protection reliability increasing provided by taking into account the higher harmonic components of the phase currents, which causes to additional losses and heating of the stator winding. It uses the simplest and widely used in protective relaying mathematical apparatus determining of most significant higher harmonics
Sun, Young; Shang, Dashan; Chai, Yisheng; Cao, Zexian; Lu, Jun
2015-09-01
From the viewpoint of electric circuit theory, the three fundamental two-terminal passive circuit elements, resistor R , capacitor C, and inductor L, are defined in terms of a relationship between two of the four basic circuit variables, charge q, current i, voltage v, and magnetic flux φ. From a symmetry concern, there should be a fourth fundamental element defined from the relationship between charge q and magnetic flux φ. Here we present both theoretical analysis and experimental evidences to demonstrate that a two-terminal passive device employing the magnetoelectric (ME) effects can exhibit a direct relationship between charge q and magnetic flux φ, and thus is able to act as the fourth fundamental circuit element. The ME effects refer to the induction of electric polarization by a magnetic field or magnetization by an electric field, and have attracted enormous interests due to their promise in many applications. However, no one has linked the ME effects with fundamental circuit theory. Both the linear and nonlinear-memory devices, termed transtor and memtranstor, respectively, have been experimentally realized using multiferroic materials showing strong ME effects. Based on our work, a full map of fundamental two-terminal circuit elements is constructed, which consists of four linear and four nonlinear-memory elements. This full map provides an invaluable guide to developing novel circuit functionalities in the future.
Non-linear Vibrations of Deep Cylindrical Shells by the p-Version Finite Element Method
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Pedro Ribeiro
2010-01-01
Full Text Available A p-version shell finite element based on the so-called shallow shell theory is for the first time employed to study vibrations of deep cylindrical shells. The finite element formulation for deep shells is presented and the linear natural frequencies of different shells, with various boundary conditions, are computed. These linear natural frequencies are compared with published results and with results obtained using a commercial software finite element package; good agreement is found. External forces are applied and the displacements in the geometrically non-linear regime computed with the p-model are found to be close to the ones computed using a commercial FE package. In all numerical tests the p-FE model requires far fewer degrees of freedom than the regular FE models. A numerical study on the dynamic behaviour of deep shells is finally carried out.
A HIGH ORDER ADAPTIVE FINITE ELEMENT METHOD FOR SOLVING NONLINEAR HYPERBOLIC CONSERVATION LAWS
Institute of Scientific and Technical Information of China (English)
Zhengfu Xu; Jinchao Xu; Chi-Wang Shu
2011-01-01
In this note,we apply the h-adaptive streamline diffusion finite element method with a small mesh-dependent artificial viscosity to solve nonlinear hyperbolic partial differential equations,with the objective of achieving high order accuracy and mesh efficiency.We compute the numerical solution to a steady state Burgers equation and the solution to a converging-diverging nozzle problem.The computational results verify that,by suitably choosing the artificial viscosity coefficient and applying the adaptive strategy based on a posterior error estimate by Johnson et al.,an order of N-3/2 accuracy can be obtained when continuous piecewise linear elements are used,where N is the number of elements.
A stabilised nodal spectral element method for fully nonlinear water waves
Engsig-Karup, A. P.; Eskilsson, C.; Bigoni, D.
2016-08-01
We present an arbitrary-order spectral element method for general-purpose simulation of non-overturning water waves, described by fully nonlinear potential theory. The method can be viewed as a high-order extension of the classical finite element method proposed by Cai et al. (1998) [5], although the numerical implementation differs greatly. Features of the proposed spectral element method include: nodal Lagrange basis functions, a general quadrature-free approach and gradient recovery using global L2 projections. The quartic nonlinear terms present in the Zakharov form of the free surface conditions can cause severe aliasing problems and consequently numerical instability for marginally resolved or very steep waves. We show how the scheme can be stabilised through a combination of over-integration of the Galerkin projections and a mild spectral filtering on a per element basis. This effectively removes any aliasing driven instabilities while retaining the high-order accuracy of the numerical scheme. The additional computational cost of the over-integration is found insignificant compared to the cost of solving the Laplace problem. The model is applied to several benchmark cases in two dimensions. The results confirm the high order accuracy of the model (exponential convergence), and demonstrate the potential for accuracy and speedup. The results of numerical experiments are in excellent agreement with both analytical and experimental results for strongly nonlinear and irregular dispersive wave propagation. The benefit of using a high-order - possibly adapted - spatial discretisation for accurate water wave propagation over long times and distances is particularly attractive for marine hydrodynamics applications.
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Ahad Zeinali
2007-12-01
Full Text Available Introduction: Because of the importance of vertebral compressive fracture (VCF role in increasing the patients’ death rate and reducing their quality of life, many studies have been conducted for a noninvasive prediction of vertebral compressive strength based on bone mineral density (BMD determination and recently finite element analysis. In this study, QCT-voxel based nonlinear finite element method is used for predicting vertebral compressive strength. Material and Methods: Four thoracolumbar vertebrae were excised from 3 cadavers with an average age of 42 years. They were then put in a water phantom and were scanned using the QCT. Using a computer program prepared in MATLAB, detailed voxel based geometry and mechanical characteristics of the vertebra were extracted from the CT images. The three dimensional finite element models of the samples were created using ANSYS computer program. The compressive strength of each vertebra body was calculated based on a linearly elastic-linearly plastic model and large deformation analysis in ANSYS and was compared to the value measured experimentally for that sample. Results: Based on the obtained results the QCT-voxel based nonlinear finite element method (FEM can predict vertebral compressive strength more effectively and accurately than the common QCT-voxel based linear FEM. The difference between the predicted strength values using this method and the measured ones was less than 1 kN for all the samples. Discussion and Conclusion: It seems that the QCT-voxel based nonlinear FEM used in this study can predict more effectively and accurately the vertebral strengths based on every vertebrae specification by considering their detailed geometric and densitometric characteristics.
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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.
Enhanced focus steering abilities of multi-element therapeutic arrays operating in nonlinear regimes
Energy Technology Data Exchange (ETDEWEB)
Yuldashev, P., E-mail: petr@acs366.phys.msu.ru; Ilyin, S. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Gavrilov, L. [Andreyev Acoustics Institute, 4 Schvernik Str., 117036 Moscow (Russian Federation); Sapozhnikov, O.; Khokhlova, V. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40" t" h, Street, Seattle, WA 98105 (United States); Kreider, W. [Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40" t" h, Street, Seattle, WA 98105 (United States)
2015-10-28
Steering abilities of a typical HIFU therapeutic array operated in linear and nonlinear regimes were compared using numerical simulation with the 3D Westervelt equation. The array included 256 elements of 1.2 MHz frequency and 6.6 mm diameter distributed in a quasi-random pattern over a spherical shell with a 130 mm aperture and a focal length of 120 mm. In the case of linear focusing, thermal effects are proportional to the intensity level and the criterion for safe array operation is that the intensity in the grating lobes should be less than 10% of the intensity in the main focus. In the case of nonlinear focusing, the heating effect is no longer proportional to intensity; therefore the heat deposition rate was chosen as the relevant metric, using the same 10% threshold for the secondary lobe in comparison with the focal maximum. When steering the focus, the same linearly predicted intensity level at the main focus was maintained by increasing the array power. Numerical simulations of the acoustic field were performed for nonlinear propagation both in water and in tissue. It was shown that for shock-forming conditions in the main focus, the steering range of safe electronic focusing is larger than that for linear propagation conditions. Nonlinear sonication regimes therefore can be used to enlarge tissue volumes that can be sonicated using electronic steering of the focus of HIFU arrays.
Nonlinear simulation of arch dam cracking with mixed finite element method
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Ren Hao
2008-06-01
Full Text Available This paper proposes a new, simple and efficient method for nonlinear simulation of arch dam cracking from the construction period to the operation period, which takes into account the arch dam construction process and temperature loads. In the calculation mesh, the contact surface of pair nodes is located at places on the arch dam where cracking is possible. A new effective iterative method, the mixed finite element method for friction-contact problems, is improved and used for nonlinear simulation of the cracking process. The forces acting on the structure are divided into two parts: external forces and contact forces. The displacement of the structure is chosen as the basic variable and the nodal contact force in the possible contact region of the local coordinate system is chosen as the iterative variable, so that the nonlinear iterative process is only limited within the possible contact surface and is much more economical. This method was used to simulate the cracking process of the Shuanghe Arch Dam in Southwest China. In order to prove the validity and accuracy of this method and to study the effect of thermal stress on arch dam cracking, three schemes were designed for calculation. Numerical results agree with actual measured data, proving that it is feasible to use this method to simulate the entire process of nonlinear arch dam cracking.
Enhanced focus steering abilities of multi-element therapeutic arrays operating in nonlinear regimes
Yuldashev, P.; Ilyin, S.; Gavrilov, L.; Sapozhnikov, O.; Kreider, W.; Khokhlova, V.
2015-10-01
Steering abilities of a typical HIFU therapeutic array operated in linear and nonlinear regimes were compared using numerical simulation with the 3D Westervelt equation. The array included 256 elements of 1.2 MHz frequency and 6.6 mm diameter distributed in a quasi-random pattern over a spherical shell with a 130 mm aperture and a focal length of 120 mm. In the case of linear focusing, thermal effects are proportional to the intensity level and the criterion for safe array operation is that the intensity in the grating lobes should be less than 10% of the intensity in the main focus. In the case of nonlinear focusing, the heating effect is no longer proportional to intensity; therefore the heat deposition rate was chosen as the relevant metric, using the same 10% threshold for the secondary lobe in comparison with the focal maximum. When steering the focus, the same linearly predicted intensity level at the main focus was maintained by increasing the array power. Numerical simulations of the acoustic field were performed for nonlinear propagation both in water and in tissue. It was shown that for shock-forming conditions in the main focus, the steering range of safe electronic focusing is larger than that for linear propagation conditions. Nonlinear sonication regimes therefore can be used to enlarge tissue volumes that can be sonicated using electronic steering of the focus of HIFU arrays.
Impact of Measuring Part Elements of Transformer Differential Protection on Input Signal Processing
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Andreev M.V
2017-08-01
Full Text Available The electric power system (EPS is a large, multi-parameter, non-linear and dynamic system. The problem of calculation of relay protection (RP settings has become more urgent nowadays. The situation is exacerbated by the active implementation of renewable energy sources, FACTS, etc., which significantly change the “traditional” EPS and their operating modes. The problem can be solved by deep analysis of functioning of main elements of RP devices in the specific operating conditions and revision of coefficients used in settings calculation. That can be done using RPs detailed mathematical models and modern EPS simulators. The results of the analysis will make it possible to formulate a new methodology for setting up RP. That is a final goal. In the framework of solving this problem, the novel approach for developing RPs’ detailed mathematical models is formulated and theoretically proved. On the basis of this approach, mathematical models of the system “instrumental transformer - auxiliary transformer - analog filter” (measuring part of digital transformer differential protection for different types of auxiliary current transformers (active and passive and filters (Butterworth, Chebyshev, Bessel are developed. A comparative numerical analysis of their frequency and phase responses is carried out, including taking into account the magnetization of instrumental current transformers. Summarizing, the theoretical and practical studies presented in the article allows formulating requirements for RPs’ detailed mathematical models, which will be used in the further research.
Assessment of the non-linear behaviour of plastic ankle foot orthoses by the finite element method
Syngellakis, S.; Arnold, M. A.; Rassoulian, H.
2000-01-01
The stiffness characteristics of plastic ankle foot orthoses (AFOs) are studied through finite element modelling and stress analysis. Particular attention is given to the modelling and prediction of non-linear AFO behaviour, which has been frequently observed in previous experimental studies but not fully addressed analytically. Both large deformation effects and material non-linearity are included in the formulation and their individual influence on results assessed. The finite element progr...
Nonlinear Legendre Spectral Finite Elements for Wind Turbine Blade Dynamics: Preprint
Energy Technology Data Exchange (ETDEWEB)
Wang, Q.; Sprague, M. A.; Jonkman, J.; Johnson, N.
2014-01-01
This paper presents a numerical implementation and examination of new wind turbine blade finite element model based on Geometrically Exact Beam Theory (GEBT) and a high-order spectral finite element method. The displacement-based GEBT is presented, which includes the coupling effects that exist in composite structures and geometric nonlinearity. Legendre spectral finite elements (LSFEs) are high-order finite elements with nodes located at the Gauss-Legendre-Lobatto points. LSFEs can be an order of magnitude more efficient that low-order finite elements for a given accuracy level. Interpolation of the three-dimensional rotation, a major technical barrier in large-deformation simulation, is discussed in the context of LSFEs. It is shown, by numerical example, that the high-order LSFEs, where weak forms are evaluated with nodal quadrature, do not suffer from a drawback that exists in low-order finite elements where the tangent-stiffness matrix is calculated at the Gauss points. Finally, the new LSFE code is implemented in the new FAST Modularization Framework for dynamic simulation of highly flexible composite-material wind turbine blades. The framework allows for fully interactive simulations of turbine blades in operating conditions. Numerical examples showing validation and LSFE performance will be provided in the final paper.
A Two-grid Method with Expanded Mixed Element for Nonlinear Reaction-diffusion Equations
Institute of Scientific and Technical Information of China (English)
Wei Liu; Hong-xing Rui; Hui Guo
2011-01-01
Expanded mixed finite element approximation of nonlinear reaction-diffusion equations is discussed. The equations considered here are used to model the hydrologic and bio-geochemical phenomena. To linearize the mixed-method equations, we use a two-grid method involving a small nonlinear system on a coarse gird of size H and a linear system on a fine grid of size h. Error estimates are derived which demonstrate that the error is O(△t + hk+1 + H2k+2-d/2) (k ≥ 1), where k is the degree of the approximating space for the primary variable and d is the spatial dimension. The above estimates are useful for determining an appropriate H for the coarse grid problems.
Finite Element Solutions for the Space Fractional Diffusion Equation with a Nonlinear Source Term
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Y. J. Choi
2012-01-01
Full Text Available We consider finite element Galerkin solutions for the space fractional diffusion equation with a nonlinear source term. Existence, stability, and order of convergence of approximate solutions for the backward Euler fully discrete scheme have been discussed as well as for the semidiscrete scheme. The analytical convergent orders are obtained as O(k+hγ˜, where γ˜ is a constant depending on the order of fractional derivative. Numerical computations are presented, which confirm the theoretical results when the equation has a linear source term. When the equation has a nonlinear source term, numerical results show that the diffusivity depends on the order of fractional derivative as we expect.
Institute of Scientific and Technical Information of China (English)
LI YaoChen
2007-01-01
The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated.Some assumptions are presented based on the published experimental data.The electrical yielding criterion,mechanical yielding criterion and isotropic hardening model are established.The flow theory in incremental forms in polarization procedure is presented.The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically.Finally,the nonlinear constitutive law expressed in a form of matrices and vectors,which is immediately associated with finite element analysis,is formulated.In the example problem of a rectangular specimen subjected to a uniaxial electric field,the procedure from virgin state to fully polarized state is simulated.Afterward,a uniaxial compressive loading is applied to depolarizing the specimen.Results are in agreement with the experimental data.
Institute of Scientific and Technical Information of China (English)
2007-01-01
The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, mechanical yielding criterion and isotropic hardening model are established. The flow theory in incremental forms in polarization procedure is presented. The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically. Finally, the nonlinear constitutive law expressed in a form of matrices and vectors, which is immediately associated with finite element analysis, is formulated. In the example problem of a rectangular specimen subjected to a uniaxial electric field, the procedure from virgin state to fully polarized state is simulated. Afterward, a uniaxial compressive loading is applied to depolarizing the specimen. Results are in agreement with the experimental data.
Analysis and Application of Advanced Control Strategies to a Heating Element Nonlinear Model
Turhan, C.; Simani, S.; Zajic, I.; Gokcen Akkurt, G.
2017-01-01
This paper presents the design of different control strategies applied to a heating element nonlinear model. The description of this heating element was obtained exploiting a data-driven and physically meaningful nonlinear continuous-time model, which represents a test-bed used in passive air conditioning for sustainable housing applications. This model has low complexity while achieving high simulation performance. The physical meaningfulness of the model provides an enhanced insight into the performance and functionality of the system. In return, this information can be used during the system simulation and improved model- based and data-driven control designs for tight temperature regulation. The main purpose of this study is thus to give several examples of viable and practical designs of control schemes with application to this heating element model. Moreover, extensive simulations and Monte- Carlo analysis are the tools for assessing experimentally the main features of the proposed control schemes, in the presence of modelling and measurement errors. These developed control methods are also compared in order to evaluate advantages and drawbacks of the considered solutions. Finally, the exploited simulation tools can serve to highlight the potential application of the proposed control strategies to real air conditioning systems.
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Romanas Karkauskas
2011-04-01
Full Text Available The expressions of the finite element method tangent stiffness matrix of geometrically nonlinear constructions are not fully presented in publications. The matrixes of small displacements stiffness are usually presented only. To solve various problems of construction analysis or design and to specify the mode of the real deflection of construction, it is necessary to have a fully described tangent matrix analytical expression. This paper presents a technique of tangent stiffness matrix generation using discrete body total potential energy stationary conditions considering geometrically nonlinear 2D frame element taking account of interelement interaction forces only. The obtained vector-function derivative of internal forces considering nodal displacements is the tangent stiffness matrix. The analytical expressions having nodal displacements of matrixes forming the content of the 2D frame construction element tangent stiffness matrix are presented in the article. The suggested methodology has been checked making symbolical calculations in the medium of MatLAB calculation complex. The analytical expression of the stiffness matrix has been obtained.Article in Lithuanian
Nonlinear nonuniform torsional vibrations of bars by the boundary element method
Sapountzakis, E. J.; Tsipiras, V. J.
2010-05-01
In this paper a boundary element method is developed for the nonuniform torsional vibration problem of bars of arbitrary doubly symmetric constant cross-section taking into account the effect of geometrical nonlinearity. The bar is subjected to arbitrarily distributed or concentrated conservative dynamic twisting and warping moments along its length, while its edges are supported by the most general torsional boundary conditions. The transverse displacement components are expressed so as to be valid for large twisting rotations (finite displacement-small strain theory), thus the arising governing differential equations and boundary conditions are in general nonlinear. The resulting coupling effect between twisting and axial displacement components is considered and torsional vibration analysis is performed in both the torsional pre- or post-buckled state. A distributed mass model system is employed, taking into account the warping, rotatory and axial inertia, leading to the formulation of a coupled nonlinear initial boundary value problem with respect to the variable along the bar angle of twist and to an "average" axial displacement of the cross-section of the bar. The numerical solution of the aforementioned initial boundary value problem is performed using the analog equation method, a BEM based method, leading to a system of nonlinear differential-algebraic equations (DAE), which is solved using an efficient time discretization scheme. Additionally, for the free vibrations case, a nonlinear generalized eigenvalue problem is formulated with respect to the fundamental mode shape at the points of reversal of motion after ignoring the axial inertia to verify the accuracy of the proposed method. The problem is solved using the direct iteration technique (DIT), with a geometrically linear fundamental mode shape as a starting vector. The validity of negligible axial inertia assumption is examined for the problem at hand.
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Muhammet Karaton
2014-01-01
Full Text Available A beam-column element based on the Euler-Bernoulli beam theory is researched for nonlinear dynamic analysis of reinforced concrete (RC structural element. Stiffness matrix of this element is obtained by using rigidity method. A solution technique that included nonlinear dynamic substructure procedure is developed for dynamic analyses of RC frames. A predicted-corrected form of the Bossak-α method is applied for dynamic integration scheme. A comparison of experimental data of a RC column element with numerical results, obtained from proposed solution technique, is studied for verification the numerical solutions. Furthermore, nonlinear cyclic analysis results of a portal reinforced concrete frame are achieved for comparing the proposed solution technique with Fibre element, based on flexibility method. However, seismic damage analyses of an 8-story RC frame structure with soft-story are investigated for cases of lumped/distributed mass and load. Damage region, propagation, and intensities according to both approaches are researched.
Karaton, Muhammet
2014-01-01
A beam-column element based on the Euler-Bernoulli beam theory is researched for nonlinear dynamic analysis of reinforced concrete (RC) structural element. Stiffness matrix of this element is obtained by using rigidity method. A solution technique that included nonlinear dynamic substructure procedure is developed for dynamic analyses of RC frames. A predicted-corrected form of the Bossak-α method is applied for dynamic integration scheme. A comparison of experimental data of a RC column element with numerical results, obtained from proposed solution technique, is studied for verification the numerical solutions. Furthermore, nonlinear cyclic analysis results of a portal reinforced concrete frame are achieved for comparing the proposed solution technique with Fibre element, based on flexibility method. However, seismic damage analyses of an 8-story RC frame structure with soft-story are investigated for cases of lumped/distributed mass and load. Damage region, propagation, and intensities according to both approaches are researched.
Finite element method for nonlinear Riesz space fractional diffusion equations on irregular domains
Yang, Z.; Yuan, Z.; Nie, Y.; Wang, J.; Zhu, X.; Liu, F.
2017-02-01
In this paper, we consider two-dimensional Riesz space fractional diffusion equations with nonlinear source term on convex domains. Applying Galerkin finite element method in space and backward difference method in time, we present a fully discrete scheme to solve Riesz space fractional diffusion equations. Our breakthrough is developing an algorithm to form stiffness matrix on unstructured triangular meshes, which can help us to deal with space fractional terms on any convex domain. The stability and convergence of the scheme are also discussed. Numerical examples are given to verify accuracy and stability of our scheme.
ALE Fractional Step Finite Element Method for Fluid-Structure Nonlinear Interaction Problem
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A computational procedure is developed to solve the problems of coupled motion of a structure and a viscous incompressible fluid. In order to incorporate the effect of the moving surface of the structure as well as the free surface motion, the arbitrary Lagrangian-Eulerian formulation is employed as the basis of the finite element spatial discretization. For numerical integration in time, the fraction step method is used. This method is useful because one can use the same linear interpolation function for both velocity and pressure. The method is applied to the nonlinear interaction of a structure and a tuned liquid damper. All computations are performed with a personal computer.
Solution of Nonlinear Coupled Heat and Moisture Transport Using Finite Element Method
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T. Krejčí
2004-01-01
Full Text Available This paper deals with a numerical solution of coupled of heat and moisture transfer using the finite element method. The mathematical model consists of balance equations of mass, energy and linear momentum and of the appropriate constitutive equations. The chosen macroscopic field variables are temperature, capillary pressures, gas pressure and displacement. In contrast with pure mechanical problems, there are several difficulties which require special attention. Systems of algebraic equations arising from coupled problems are generally nonlinear, and the matrices of such systems are nonsymmetric and indefinite. The first experiences of solving complicated coupled problems are mentioned in this paper.
Tang, Yao-Zong; Li, Xiao-Lin
2017-03-01
We first give a stabilized improved moving least squares (IMLS) approximation, which has better computational stability and precision than the IMLS approximation. Then, analysis of the improved element-free Galerkin method is provided theoretically for both linear and nonlinear elliptic boundary value problems. Finally, numerical examples are given to verify the theoretical analysis. Project supported by the National Natural Science Foundation of China (Grant No. 11471063), the Chongqing Research Program of Basic Research and Frontier Technology, China (Grant No. cstc2015jcyjBX0083), and the Educational Commission Foundation of Chongqing City, China (Grant No. KJ1600330).
Institute of Scientific and Technical Information of China (English)
Yan-ping Chen; Yun-qing Huang
2001-01-01
Improved L2-error estimates are computed for mixed finite element methods for second order nonlinear hyperbolic equations. Results are given for the continuous-time case. The convergence of the values for both the scalar function and the flux is demonstrated. The technique used here covers the lowest-order Raviart-Thomas spaces, as well as the higherorder spaces. A second paper will present the analysis of a fully discrete scheme (Numer.Math. J. Chinese Univ. vol.9, no.2, 2000, 181-192).
Almeida, EDGARD S.; Spilker, ROBERT L.
1998-01-01
This two-part paper addresses finite element-based computational models for the three-dimensional (3-D) nonlinear analysis of soft hydrated tissues, such as articular cartilage in diarthrodial joints, under physiologically relevant loading conditions. A biphasic continuum description is used to represent the soft tissue as a two-phase mixture of incompressible inviscid fluid and a hyperelastic, transversely isotropic solid. Alternate mixed-penalty and velocity-pressure finite element formulations are used to solve the nonlinear biphasic governing equations, including the effects of strain-dependent permeability and a hyperelastic solid phase under finite deformation. The resulting first-order, nonlinear system of equations is discretized in time using an implicit finite difference scheme, and solved using the Newton-Raphson method. Details of the formulations were presented in Part I [1]. In Part II, the two formulations are used to develop two-dimensional (2-D) quadrilateral and triangular elements and three-dimensional (3-D) hexahedral and tetrahedral elements. Numerical examples, including those representative of soft tissue material testing and simple human joints, are used to validate the formulations and to illustrate their applications. A focus of this work is the comparison of the alternate formulations for nonlinear problems. While it is demonstrated that both formulations produce a range of converging elements, the velocity-pressure formulation is found to be more efficient computationally.
Padovan, Joe
1986-01-01
In a three part series of papers, a generalized finite element analysis scheme is developed to handle the steady and transient response of moving/rolling nonlinear viscoelastic structure. This paper considers the development of the moving/rolling element strategy, including the effects of large deformation kinematics and viscoelasticity modelled by fractional integro-differential operators. To improve the solution strategy, a special hierarchical constraint procedure is developed for the case of steady rolling/translating as well as a transient scheme involving the use of a Grunwaldian representation of the fractional operator. In the second and third parts of the paper, 3-D extensions are developed along with transient contact strategies enabling the handling of impacts with obstructions. Overall, the various developments are benchmarked via comprehensive 2- and 3-D simulations. These are correlated with experimental data to define modelling capabilities.
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Yong Zhao
1996-01-01
Full Text Available The large strain ratcheting in cyclic plasticity of a typical pressurized pipe elbow in a realistic nuclear piping system was investigated in a more quantitative manner than previously. The elbow was modeled using a fine mesh of shell elements that can provide the completed information of detailed time varying strain distributions in the whole elbow area. The nonlinear time history stress analyses performed were based on a pseudostatic concept using the vector-valued stochastic displacement response time series loaded at the elbow ends. The response time series were synthesized using a simulation approach based on the random vibration analyses of the piping system and its supporting building. After a finite element mesh convergence study, parametric analyses were conducted that included the effects due to the magnitude changes in excitation level, internal pressure, material yield stress, and material strain hardening.
The protective effects of trace elements against side effects induced by ionizing radiation
Energy Technology Data Exchange (ETDEWEB)
Hosseinimehr, Seyed Jaial [Dept. of Radiopharmacy, Faculty of Pharmacy, Pharmaceutical Sciences Research Center, Mazandaran University of Medical Sciences, Sari (Iran, Islamic Republic of)
2015-06-15
Trace elements play crucial role in the maintenance of genome stability in the cells. Many endogenous defense enzymes are containing trace elements such as superoxide dismutase and metalloproteins. These enzymes are contributing in the detoxification of reactive oxidative species (ROS) induced by ionizing radiation in the cells. Zinc, copper, manganese, and selenium are main trace elements that have protective roles against radiation-induced DNA damages. Trace elements in the free salt forms have protective effect against cell toxicity induced by oxidative stress, metal-complex are more active in the attenuation of ROS particularly through superoxide dismutase mimetic activity. Manganese-complexes in protection of normal cell against radiation without any protective effect on cancer cells are more interesting compounds in this topic. The aim of this paper to review the role of trace elements in protection cells against genotoxicity and side effects induced by ionizing radiation.
Analysis of Nonlinear Vibration of Hard Coating Thin Plate by Finite Element Iteration Method
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Hui Li
2014-01-01
Full Text Available This paper studies nonlinear vibration mechanism of hard coating thin plate based on macroscopic vibration theory and proposes finite element iteration method (FEIM to theoretically calculate its nature frequency and vibration response. First of all, strain dependent mechanical property of hard coating is briefly introduced and polynomial method is adopted to characterize the storage and loss modulus of coating material. Then, the principle formulas of inherent and dynamic response characteristics of the hard coating composite plate are derived. And consequently specific analysis procedure is proposed by combining ANSYS APDL and self-designed MATLAB program. Finally, a composite plate coated with MgO + Al2O3 is taken as a study object and both nonlinear vibration test and analysis are conducted on the plate specimen with considering strain dependent mechanical parameters of hard coating. Through comparing the resulting frequency and response results, the practicability and reliability of FEIM have been verified and the corresponding analysis results can provide an important reference for further study on nonlinear vibration mechanism of hard coating composite structure.
Computers, privacy and data protection an element of choice
Gutwirth, Serge; De Hert, Paul; Leenes, Ronald
2011-01-01
This timely volume presents current developments in ICT and privacy/data protection. Readers will find an alternative view of the Data Protection Directive, the contentious debates on data sharing with the USA (SWIFT, PNR), and the judicial and political resistance against data retention.
Directory of Open Access Journals (Sweden)
Haitao Che
2011-01-01
Full Text Available We investigate a H1-Galerkin mixed finite element method for nonlinear viscoelasticity equations based on H1-Galerkin method and expanded mixed element method. The existence and uniqueness of solutions to the numerical scheme are proved. A priori error estimation is derived for the unknown function, the gradient function, and the flux.
Institute of Scientific and Technical Information of China (English)
Zhiguang Xiong; Chuanmiao Chen
2007-01-01
In this paper,n-degree continuous finite element method with interpolated coefficients for nonlinear initial value problem of ordinary differential equation is introduced and analyzed. An optimal superconvergence u - uh = O(hn+2),n ≥ 2,at (n + 1)-order Lobatto points in each element respectively is proved. Finally the theoretical results are tested by a numerical example.
Analysis of Retrofitting Non-Linear Finite Element Of RCC Beam And Column Using Ansys
Directory of Open Access Journals (Sweden)
T. Subramani
2014-12-01
Full Text Available Many of the existing reinforced concrete structures throughout the world are in urgent need of strengthening, repair or reconstruction because of deterioration due to various factors like corrosion, lack of detailing, failure of bonding between beam-column joints, increase in service loads, etc., leading to cracking, spalling, loss of strength, deflection, etc., Direct observation of these damaged structures has shown that damage occurs usually at the beam-column joints, with failure in bending or shear, depending on geometry and reinforcement distribution type.A nonlinear finite element analysis that is a simulation technique is used in this work to evaluate the effectiveness of retrofitting technique called “wrapping technique” for using carbon fibres (FRP for strengthening of RC beam-column connections damaged due to various reasons. After carrying out a nonlinear finite element analysis of a reinforced concrete frame (Controlled Specimen and reinforced concrete frame where carbon fibres are attached to the beam column joint portion in different patterns ,the measured response histories of the original and strengthened specimens are then subsequently compared. It is seen that the strengthened specimens exhibit significant increase in strength, stiffness, and stability as compared to controlled specimens. It appears that the proposed simulation technique will have a significant impact in engineering practice in the near future.
Maquer, Ghislain; Laurent, Marc; Brandejsky, Vaclav; Pretterklieber, Michael L; Zysset, Philippe K
2014-06-01
Disc degeneration, usually associated with low back pain and changes of intervertebral stiffness, represents a major health issue. As the intervertebral disc (IVD) morphology influences its stiffness, the link between mechanical properties and degenerative grade is partially lost without an efficient normalization of the stiffness with respect to the morphology. Moreover, although the behavior of soft tissues is highly nonlinear, only linear normalization protocols have been defined so far for the disc stiffness. Thus, the aim of this work is to propose a nonlinear normalization based on finite elements (FE) simulations and evaluate its impact on the stiffness of human anatomical specimens of lumbar IVD. First, a parameter study involving simulations of biomechanical tests (compression, flexion/extension, bilateral torsion and bending) on 20 FE models of IVDs with various dimensions was carried out to evaluate the effect of the disc's geometry on its compliance and establish stiffness/morphology relations necessary to the nonlinear normalization. The computed stiffness was then normalized by height (H), cross-sectional area (CSA), polar moment of inertia (J) or moments of inertia (Ixx, Iyy) to quantify the effect of both linear and nonlinear normalizations. In the second part of the study, T1-weighted MRI images were acquired to determine H, CSA, J, Ixx and Iyy of 14 human lumbar IVDs. Based on the measured morphology and pre-established relation with stiffness, linear and nonlinear normalization routines were then applied to the compliance of the specimens for each quasi-static biomechanical test. The variability of the stiffness prior to and after normalization was assessed via coefficient of variation (CV). The FE study confirmed that larger and thinner IVDs were stiffer while the normalization strongly attenuated the effect of the disc geometry on its stiffness. Yet, notwithstanding the results of the FE study, the experimental stiffness showed consistently
DEFF Research Database (Denmark)
Palleti, Hara Naga Krishna Teja; Thomsen, Ole Thybo; Taher, Siavash Talebi;
In this paper, polymer foam cored sandwich structures with fibre reinforced composite face sheets subjected to combined mechanical and thermal loads will be analysed using the commercial FE code ABAQUS® incorporating both material and geometrical nonlinearity. Large displacements and rotations ar...... are included in the analysis. The full nonlinear stress-strain curves up to failure will be considered for the polymer foams at different temperatures to study the effect of material nonlinearity in detail....
Neurosurgery Simulation Using Non-linear Finite Element Modeling and Haptic Interaction.
Lee, Huai-Ping; Audette, Michel; Joldes, Grand Roman; Enquobahrie, Andinet
2012-02-23
Real-time surgical simulation is becoming an important component of surgical training. To meet the real-time 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.
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.
Hammerand, Daniel C.
Over the past several decades, the use of composite materials has grown considerably. Typically, fiber-reinforced polymer-matrix composites are modeled as being linear elastic. However, it is well-known that polymers are viscoelastic in nature. Furthermore, the analysis of complex structures requires a numerical approach such as the finite element method. In the present work, a triangular flat shell element for linear elastic composites is extended to model linear viscoelastic composites. Although polymers are usually modeled as being incompressible, here they are modeled as compressible. Furthermore, the macroscopic constitutive properties for fiber-reinforced composites are assumed to be known and are not determined using the matrix and fiber properties along with the fiber volume fraction. Hygrothermo-rheologically simple materials are considered for which a change in the hygrothermal environment results in a horizontal shifting of the relaxation moduli curves on a log time scale, in addition to the usual hygrothermal loads. Both the temperature and moisture are taken to be prescribed. Hence, the heat energy generated by the viscoelastic deformations is not considered. When the deformations and rotations are small under an applied load history, the usual engineering stress and strain measures can be used and the time history of a viscoelastic deformation process is determined using the original geometry of the structure. If, however, sufficiently large loads are applied, the deflections and rotations will be large leading to changes in the structural stiffness characteristics and possibly the internal loads carried throughout the structure. Hence, in such a case, nonlinear effects must be taken into account and the appropriate stress and strain measures must be used. Although a geometrically-nonlinear finite element code could always be used to compute geometrically-linear deformation processes, it is inefficient to use such a code for small deformations, due to
DEFF Research Database (Denmark)
Lu, Kaiyuan; Rasmussen, Peter Omand; Ritchie, Ewen
2011-01-01
This paper presents a new method for computation of the nonlinear flux linkage in 3-D finite-element models (FEMs) of electrical machines. Accurate computation of the nonlinear flux linkage in 3-D FEM is not an easy task. Compared to the existing energy-perturbation method, the new technique......-perturbation method. The new method proposed is validated using experimental results on two different permanent magnet machines....
Elements of Integration in Winter Wheat Protection Programs
Directory of Open Access Journals (Sweden)
Cecylia Jańczak
2012-12-01
Full Text Available In Poland winter wheat is grown on the area of 1.600.000 ha. Most of the plant protection treatments are being done without thorough analysis of real threats from pests and diseases. The aim of the research is to develop the optimal program of wheat protection against pests and diseases based on integration of various methods of plant protection. Two programs: conventional and integrated were compared. In integrated program the eventual needs and terms of treatments were estimated on the basis of detailed observations of plant infection, pest appearance, their natural enemies and thorough analysis of weather conditions and forecasts. The role of disease resistant wheat varietes and nitrogen fertilizers was also analysed. The research took into account beneficial entomofauna and its influence on pest numbers as well as influence of chemicals used in agriculture on their species. As the result the selective pesticides, safe to beneficial organisms, were selected. The quantity and quality of winter wheat yield was analysed, including protein and gluten contents. The economic effectiveness of various programs of wheat protection against pests and diseases was assessed. The results of research are important both in practical and scientific sense.
Institute of Scientific and Technical Information of China (English)
QIN Xin-qiang; MA Yi-chen; ZHANG Yin
2005-01-01
For two-dimension nonlinear convection diffusion equation, a two-grid method of characteristics finite-element solution was constructed. In this method the nonlinear iterations is only to execute on the coarse grid and the fine-grid solution can be obtained in a single linear step. For the nonlinear convection-dominated diffusion equation, this method can not only stabilize the numerical oscillation but also accelerate the convergence and improve the computational efficiency. The error analysis demonstrates if the mesh sizes between coarse-grid and fine-grid satisfy the certain relationship, the two-grid solution and the characteristics finite-element solution have the same order of accuracy. The numerical example confirms that the two-grid method is more efficient than that of characteristics finite-element method.
Directory of Open Access Journals (Sweden)
Woo-Young Jung
2013-01-01
Full Text Available An improved 8-node shell finite element applicable for the geometrically linear and nonlinear analyses of plates and shells is presented. Based on previous first-order shear deformation theory, the finite element model is further improved by the combined use of assumed natural strains and different sets of collocation points for the interpolation of the different strain components. The influence of the shell element with various conditions such as locations, number of enhanced membranes, and shear interpolation is also identified. By using assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. Furthermore, to characterize the efficiency of these modifications of the 8-node shell finite elements, numerical studies are carried out for the geometrically linear and non-linear analysis of plates and shells. In comparison to some other shell elements, numerical examples for the methodology indicate that the modified element described locking-free behavior and better performance. More specifically, the numerical examples of annular plate presented herein show good validity, efficiency, and accuracy to the developed nonlinear shell element.
Directory of Open Access Journals (Sweden)
M.J. Uddin
2016-06-01
Full Text Available A numerical investigation of two dimensional steady state laminar boundary layer flow of a viscous electrically-conducting nanofluid in the vicinity of a stretching/shrinking porous flat plate located in a Darcian porous medium is performed. The nonlinear Rosseland radiation effect is taken into account. Velocity slip and thermal slip at the boundary as well as the newly developed zero mass flux boundary conditions are also implemented to achieve physically applicable results. The governing transport equations are reduced to a system of nonlinear ordinary differential equations using appropriate similarity transformations and these are then solved numerically using a variational finite element method (FEM. The influence of the governing parameters (Darcy number, magnetic field, velocity and thermal slip, temperature ratio, transpiration, Brownian motion, thermophoresis, Lewis number and Reynolds number on the dimensionless velocity, temperature, nanoparticle volume fraction as well as the skin friction, the heat transfer rates and the mass transfer rates are examined and illustrated in detail. The FEM code is validated with earlier studies for non-magnetic non-slip flow demonstrating close correlation. The present study is relevant to high-temperature nano-materials processing operations.
Espath, L. F R
2015-02-03
A numerical model to deal with nonlinear elastodynamics involving large rotations within the framework of the finite element based on NURBS (Non-Uniform Rational B-Spline) basis is presented. A comprehensive kinematical description using a corotational approach and an orthogonal tensor given by the exact polar decomposition is adopted. The state equation is written in terms of corotational variables according to the hypoelastic theory, relating the Jaumann derivative of the Cauchy stress to the Eulerian strain rate.The generalized-α method (Gα) method and Generalized Energy-Momentum Method with an additional parameter (GEMM+ξ) are employed in order to obtain a stable and controllable dissipative time-stepping scheme with algorithmic conservative properties for nonlinear dynamic analyses.The main contribution is to show that the energy-momentum conservation properties and numerical stability may be improved once a NURBS-based FEM in the spatial discretization is used. Also it is shown that high continuity can postpone the numerical instability when GEMM+ξ with consistent mass is employed; likewise, increasing the continuity class yields a decrease in the numerical dissipation. A parametric study is carried out in order to show the stability and energy budget in terms of several properties such as continuity class, spectral radius and lumped as well as consistent mass matrices.
A Space-Time Finite Element Model for Design and Control Optimization of Nonlinear Dynamic Response
Directory of Open Access Journals (Sweden)
P.P. Moita
2008-01-01
Full Text Available A design and control sensitivity analysis and multicriteria optimization formulation is derived for flexible mechanical systems. This formulation is implemented in an optimum design code and it is applied to the nonlinear dynamic response. By extending the spatial domain to the space-time domain and treating the design variables as control variables that do not change with time, the design space is included in the control space. Thus, one can unify in one single formulation the problems of optimum design and optimal control. Structural dimensions as well as lumped damping and stiffness parameters plus control driven forces, are considered as decision variables. The dynamic response and its sensitivity with respect to the design and control variables are discretized via space-time finite elements, and are integrated at-once, as it is traditionally used for static response. The adjoint system approach is used to determine the design sensitivities. Design optimization numerical examples are performed. Nonlinear programming and optimality criteria may be used for the optimization process. A normalized weighted bound formulation is used to handle multicriteria problems.
A finite element perspective on non-linear FFT-based micromechanical simulations
Zeman, Jan; Vondřejc, Jaroslav; Peerlings, Ron H J; Geers, Marc G D
2016-01-01
Fourier solvers have become efficient tools to establish structure-property relations in heterogeneous materials. Introduced as an alternative to the Finite Element (FE) method, they are based on fixed-point solutions of the Lippmann-Schwinger type integral equation. Their computational efficiency results from handling the kernel of this equation by the Fast Fourier Transform (FFT). However, the kernel is derived from an auxiliary homogeneous linear problem, which renders the extension of FFT-based schemes to non-linear problems conceptually difficult. This paper aims to establish a link between FE- and FFT-based methods, in order to develop a solver applicable to general history- and time-dependent material models. For this purpose, we follow the standard steps of the FE method, starting from the weak form, proceeding to the Galerkin discretization and the numerical quadrature, up to the solution of non-linear equilibrium equations by an iterative Newton-Krylov solver. No auxiliary linear problem is thus nee...
Dyja, Robert; van der Zee, Kristoffer G
2016-01-01
We present an adaptive methodology for the solution of (linear and) non-linear time dependent problems that is especially tailored for massively parallel computations. The basic concept is to solve for large blocks of space-time unknowns instead of marching sequentially in time. The methodology is a combination of a computationally efficient implementation of a parallel-in-space-time finite element solver coupled with a posteriori space-time error estimates and a parallel mesh generator. This methodology enables, in principle, simultaneous adaptivity in both space and time (within the block) domains. We explore this basic concept in the context of a variety of time-steppers including $\\Theta$-schemes and Backward Differentiate Formulas. We specifically illustrate this framework with applications involving time dependent linear, quasi-linear and semi-linear diffusion equations. We focus on investigating how the coupled space-time refinement indicators for this class of problems affect spatial adaptivity. Final...
Stochastic Finite Element Analysis of Non-Linear Structures Modelled by Plasticity Theory
DEFF Research Database (Denmark)
Frier, Christian; Sørensen, John Dalsgaard
2003-01-01
to estimate the probability of exceeding a critical event, defined by a so-called limit state function. The limit state function is obtained implicitly by non-linear FEM analysis from a realization of random material properties. As the latter can be modeled as random fields varying continuously over......, the gradient of the limit state function with respect to the random material variables is needed, or equivalently, the design sensitivities of the output to the FEM analysis with respect to the input. To this end, the Conditional Derivative Method (CDM) is used, which is a specialized Direct Differentiation...... the structure, a discretisation into random elements/variables is introduced. To this purpose, both the Midpoint (MP) and the Spatial Average (SA) approach are considered. The failure probability is obtained iteratively based on a first order Taylor series expansion of the limit state function. Thus...
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.
Johnson, J. M.; Reale, D. V.; Krile, J. T.; Garcia, R. S.; Cravey, W. H.; Neuber, A. A.; Dickens, J. C.; Mankowski, J. J.
2016-05-01
In this paper, a solid-state four element array gyromagnetic nonlinear transmission line high power microwave system is presented as well as a detailed description of its subsystems and general output capabilities. This frequency agile S-band source is easily adjusted from 2-4 GHz by way of a DC driven biasing magnetic field and is capable of generating electric fields of 7.8 kV/m at 10 m correlating to 4.2 MW of RF power with pulse repetition frequencies up to 1 kHz. Beam steering of the array at angles of ±16.7° is also demonstrated, and the associated general radiation pattern is detailed.
Energy Technology Data Exchange (ETDEWEB)
Leng, Wei [Chinese Academy of Sciences; Ju, Lili [University of South Carolina; Gunzburger, Max [Florida State University; Price, Stephen [Los Alamos National Laboratory; Ringler, Todd [Los Alamos National Laboratory,
2012-01-01
The numerical modeling of glacier and ice sheet evolution is a subject of growing interest, in part because of the potential for models to inform estimates of global sea level change. This paper focuses on the development of a numerical model that determines the velocity and pressure fields within an ice sheet. Our numerical model features a high-fidelity mathematical model involving the nonlinear Stokes system and combinations of no-sliding and sliding basal boundary conditions, high-order accurate finite element discretizations based on variable resolution grids, and highly scalable parallel solution strategies, all of which contribute to a numerical model that can achieve accurate velocity and pressure approximations in a highly efficient manner. We demonstrate the accuracy and efficiency of our model by analytical solution tests, established ice sheet benchmark experiments, and comparisons with other well-established ice sheet models.
Giles, G. L.; Wallas, M.
1981-01-01
User documentation is presented for a computer program which considers the nonlinear properties of the strain isolator pad (SIP) in the static stress analysis of the shuttle thermal protection system. This program is generalized to handle an arbitrary SIP footprint including cutouts for instrumentation and filler bar. Multiple SIP surfaces are defined to model tiles in unique locations such as leading edges, intersections, and penetrations. The nonlinearity of the SIP is characterized by experimental stress displacement data for both normal and shear behavior. Stresses in the SIP are calculated using a Newton iteration procedure to determine the six rigid body displacements of the tile which develop reaction forces in the SIP to equilibrate the externally applied loads. This user documentation gives an overview of the analysis capabilities, a detailed description of required input data and an example to illustrate use of the program.
Institute of Scientific and Technical Information of China (English)
罗振东; 朱江; 王会军
2002-01-01
A nonlinear Galerkin/ Petrov- least squares mixed element (NGPLSME) method for the stationary Navier-Stokes equations is presented and analyzed. The scheme is that Petrov-least squares forms of residuals are added to the nonlinear Galerkin mixed element method so that it is stable for any combination of discrete velocity and pressure spaces without requiring the Babuska-Brezzi stability condition. The existence, uniqueness and convergence ( at optimal rate ) of the NGPLSME solution is proved in the case of sufficient viscosity ( or small data).
Segura, Christopher L.
Numerical simulation tools capable of modeling nonlinear material and geometric behavior are important to structural engineers concerned with approximating the strength and deformation capacity of a structure. While structures are typically designed to behave linear elastic when subjected to building code design loads, exceedance of the linear elastic range is often an important consideration, especially with regards to structural response during hazard level events (i.e. earthquakes, hurricanes, floods), where collapse prevention is the primary goal. This thesis addresses developments made to Mercury, a nonlinear finite element program developed in MATLAB for numerical simulation and in C++ for real time hybrid simulation. Developments include the addition of three new constitutive models to extend Mercury's lumped plasticity modeling capabilities, a constitutive driver tool for testing and implementing Mercury constitutive models, and Mercury pre and post-processing tools. Mercury has been developed as a tool for transient analysis of distributed plasticity models, offering accurate nonlinear results on the material level, element level, and structural level. When only structural level response is desired (collapse prevention), obtaining material level results leads to unnecessarily lengthy computational time. To address this issue in Mercury, lumped plasticity capabilities are developed by implementing two lumped plasticity flexural response constitutive models and a column shear failure constitutive model. The models are chosen for implementation to address two critical issues evident in structural testing: column shear failure and strength and stiffness degradation under reverse cyclic loading. These tools make it possible to model post-peak behavior, capture strength and stiffness degradation, and predict global collapse. During the implementation process, a need was identified to create a simple program, separate from Mercury, to simplify the process of
Optimization of elstomeric micro-fluidic valve dimensions using non-linear finite element methods
Directory of Open Access Journals (Sweden)
H Khawaja
2016-04-01
Full Text Available We use a nonlinear finite element (FE method model to compare,optimize and determine the limits for useful geometries of microfluidicvalves in elastomer polydimethylsiloxane (PDMS. Simulations havebeen performed with the aim of finding the optimal shape, size andlocation of pressurization that minimizes the pressure required to operatethe valve. One important constraint governing the design parameters isthat the stresses should be within elastic limits, so that the componentremains safe from any type of structural failure. To obtain reliable results,non-linear stress analysis was performed using the Mooney-Rivlin 9parameter approximation which is based on the Hyper Elastic MaterialModel. A 20 noded brick element was used for the development of FEmodel. Mesh sensitivity analysis was also performed to assess the qualityof the results. The simulations were performed with commerciallyavailable FE modeling software, developed by ANSYS Inc. to determinethe effect of varying different geometric parameters on the performanceof micro-fluidic valves.The aim of this work is to determine the geometry of the channel crosssectionthat would result in the largest deflection for the least appliedpressure, i.e. to minimize the pressure needed to operate the valve.
Solving nonlinear nonstationary problem of heat-conductivity by finite element method
Directory of Open Access Journals (Sweden)
Антон Янович Карвацький
2016-11-01
Full Text Available Methodology and effective solving algorithm of non-linear dynamic problems of thermal and electric conductivity with significant temperature dependence of thermal and physical properties are given on the basis of finite element method (FEM and Newton linearization method. Discrete equations system FEM was obtained with the use of Galerkin method, where the main function is the finite element form function. The methodology based on successive solving problems of thermal and electrical conductivity has been examined in the work in order to minimize the requirements for calculating resources (RAM. in particular. Having used Mathcad software original programming code was developed to solve the given problem. After investigation of the received results, comparative analyses of accurate solution data and results of numerical solutions, obtained with the use of Matlab programming products, was held. The geometry of one fourth part of the finite sized cylinder was used to test the given numerical model. The discretization of the calculation part was fulfilled using the open programming software for automated Gmsh nets with tetrahedral units, while ParaView, which is an open programming code as well, was used to visualize the calculation results. It was found out that the maximum value violation of potential and temperature determination doesn`t exceed 0,2-0,83% in the given work according to the problem conditions
Chin, Sanghooon; Gonzalez-Herraez, Miguel; Thévenaz, Luc
2009-11-23
We experimentally demonstrate complete compensation of pulse broadening in an amplifier-based slow light system. The configuration of the delay line basically consists of two stages: a conventional Brillouin slow light system and a nonlinear regeneration element. Signal pulses experienced both time delay and temporal broadening through the Brillouin delay line and then the delayed pulses were delivered into a nonlinear optical loop mirror. Due to the nonlinear response of the transmission of the fiber loop, the inevitably broadened pulses were moderately compressed in the output of the loop, without loss in the capacity to delay the pulses. The overall result is that, for the maximum delay, the width of the pulse could be kept below the input width while the time delays introduced by the slow light element were preserved. Using this delay line, a signal pulse with duration of 27 ns at full width at half maximum was delayed up to 1.3-bits without suffering from signal distortion.
Institute of Scientific and Technical Information of China (English)
SHI Dong-yang; WANG Hui-min; LI Zhi-yan
2009-01-01
A lumped mass approximation scheme of a low order Crouzeix-Raviart type nonconforming triangular finite element is proposed to a kind of nonlinear parabolic integro-differential equations. The L2 error estimate is derived on anisotropic meshes without referring to the traditional nonclassical elliptic projection.
Axisymmetric finite element (FE) method was developed using a commercial computer program to simulate cone penetration process in layered granular soil. Soil was considered as a non-linear elastic plastic material which was modeled using variable elastic parameters of Young’s Modulus and Poisson’s r...
Ebrahimian, Hamed; Astroza, Rodrigo; Conte, Joel P.; de Callafon, Raymond A.
2017-02-01
This paper presents a framework for structural health monitoring (SHM) and damage identification of civil structures. This framework integrates advanced mechanics-based nonlinear finite element (FE) modeling and analysis techniques with a batch Bayesian estimation approach to estimate time-invariant model parameters used in the FE model of the structure of interest. The framework uses input excitation and dynamic response of the structure and updates a nonlinear FE model of the structure to minimize the discrepancies between predicted and measured response time histories. The updated FE model can then be interrogated to detect, localize, classify, and quantify the state of damage and predict the remaining useful life of the structure. As opposed to recursive estimation methods, in the batch Bayesian estimation approach, the entire time history of the input excitation and output response of the structure are used as a batch of data to estimate the FE model parameters through a number of iterations. In the case of non-informative prior, the batch Bayesian method leads to an extended maximum likelihood (ML) estimation method to estimate jointly time-invariant model parameters and the measurement noise amplitude. The extended ML estimation problem is solved efficiently using a gradient-based interior-point optimization algorithm. Gradient-based optimization algorithms require the FE response sensitivities with respect to the model parameters to be identified. The FE response sensitivities are computed accurately and efficiently using the direct differentiation method (DDM). The estimation uncertainties are evaluated based on the Cramer-Rao lower bound (CRLB) theorem by computing the exact Fisher Information matrix using the FE response sensitivities with respect to the model parameters. The accuracy of the proposed uncertainty quantification approach is verified using a sampling approach based on the unscented transformation. Two validation studies, based on realistic
Energy Technology Data Exchange (ETDEWEB)
Maker, B.N.
1995-04-14
This report provides a user`s manual for NIKE3D, a fully implicit three-dimensional finite element code for analyzing the finite strain static and dynamic response of inelastic solids, shells, and beams. Spatial discretization is achieved by the use of 8-node solid elements, 2-node truss and beam elements, and 4-node membrane and shell elements. Over twenty constitutive models are available for representing a wide range of elastic, plastic, viscous, and thermally dependent material behavior. Contact-impact algorithms permit gaps, frictional sliding, and mesh discontinuities along material interfaces. Several nonlinear solution strategies are available, including Full-, Modified-, and Quasi-Newton methods. The resulting system of simultaneous linear equations is either solved iteratively by an element-by-element method, or directly by a factorization method, for which case bandwidth minimization is optional. Data may be stored either in or out of core memory to allow for large analyses.
Stevanella, Marco; Votta, Emiliano; Redaelli, Alberto
2009-12-01
Finite element modeling represents an established method for the comprehension of the mitral function and for the simulation of interesting clinical scenarios. However, current models still do not include all the key aspects of the real system. We implemented a new structural finite element model that considers (i) an accurate morphological description of the valve, (ii) a description of the tissues' mechanical properties that accounts for anisotropy and nonlinearity, and (iii) dynamic boundary conditions that mimic annulus and papillary muscles' contraction. The influence of such contraction on valve biomechanics was assessed by comparing the computed results with the ones obtained through an auxiliary model with fixed annulus and papillary muscles. At the systolic peak, the leaflets' maximum principal stress contour showed peak values in the anterior leaflet at the strut chordae insertion zone (300 kPa) and near the annulus (200-250 kPa), while much lower values were detected in the posterior leaflet. Both leaflets underwent larger tensile strains in the longitudinal direction, while in the circumferential one the anterior leaflet experienced nominal tensile strains up to 18% and the posterior one experienced compressive strains up to 23% associated with the folding of commissures and paracommissures, consistently with tissue redundancy. The force exerted by papillary muscles at the systolic peak was equal to 4.11 N, mainly borne by marginal chordae (76% of the force). Local reaction forces up to 45 mN were calculated on the annulus, leading to tensions of 89 N/m and 54 N/m for its anterior and posterior tracts, respectively. The comparison with the results of the auxiliary model showed that annular contraction mainly affects the leaflets' circumferential strains. When it was suppressed, no more compressive strains could be observed and peak strain values were located in the belly of the anterior leaflet. Computational results agree to a great extent with
Mei, Chuh; Shen, Mo-How
1987-01-01
Multiple-mode nonlinear forced vibration of a beam was analyzed by the finite element method. Inplane (longitudinal) displacement and inertia (IDI) are considered in the formulation. By combining the finite element method and nonlinear theory, more realistic models of structural response are obtained more easily and faster.
Salama, M.; Trubert, M.
1979-01-01
A formulation is given for the second order nonlinear equations of motion for spinning line-elements having little or no intrinsic structural stiffness. Such elements have been employed in recent studies of structural concepts for future large space structures such as the Heliogyro solar sailer. The derivation is based on Hamilton's variational principle and includes the effect of initial geometric imperfections (axial, curvature, and twist) on the line-element dynamics. For comparison with previous work, the nonlinear equations are reduced to a linearized form frequently found in the literature. The comparison has revealed several new spin-stiffening terms that have not been previously identified and/or retained. They combine geometric imperfections, rotary inertia, Coriolis, and gyroscopic terms.
Assessment of the non-linear behaviour of plastic ankle foot orthoses by the finite element method.
Syngellakis, S; Arnold, M A; Rassoulian, H
2000-01-01
The stiffness characteristics of plastic ankle foot orthoses (AFOs) are studied through finite element modelling and stress analysis. Particular attention is given to the modelling and prediction of non-linear AFO behaviour, which has been frequently observed in previous experimental studies but not fully addressed analytically. Both large deformation effects and material non-linearity are included in the formulation and their individual influence on results assessed. The finite element program is subsequently applied to the simulation of a series of tests designed to investigate the relation between AFO trimline location and stiffness for moderate and large rotations. Through careful consideration and identification of key modelling parameters, the developed finite element solution proves to be a reliable and effective alternative means of assessing variations of a typical plastic AFO design so that particular patient requirements could be met, in the long term.
Explicit Nonlinear Finite Element Geometric Analysis of Parabolic Leaf Springs under Various Loads
Kong, Y. S.; Omar, M. Z.; Chua, L. B.; Abdullah, S.
2013-01-01
This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE) method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability. PMID:24298209
Energy Technology Data Exchange (ETDEWEB)
HAMMERAND,DANIEL C.; KAPANIA,RAKESH K.
2000-05-01
A triangular flat shell element for large deformation analysis of linear viscoelastic laminated composites is presented. Hygrothermorheologically simple materials are considered for which a change in the hygrothermal environment results in a horizontal shifting of the relaxation moduli curves on a log time scale, in addition to the usual hygrothermal loads. Recurrence relations are developed and implemented for the evaluation of the viscoelastic memory loads. The nonlinear deformation process is computed using an incremental/iterative approach with the Newton-Raphson Method used to find the incremental displacements in each step. The presented numerical examples consider the large deformation and stability of linear viscoelastic structures under deformation-independent mechanical loads, deformation-dependent pressure loads, and thermal loads. Unlike elastic structures that have a single critical load value associated with a given snapping of buckling instability phenomenon, viscoelastic structures will usually exhibit a particular instability for a range of applied loads over a range of critical times. Both creep buckling and snap-through examples are presented here. In some cases, viscoelastic results are also obtained using the quasielastic method in which load-history effects are ignored, and time-varying viscoelastic properties are simply used in a series of elastic problems. The presented numerical examples demonstrate the capability and accuracy of the formulation.
Nonlinear visco-elastic finite element analysis of different porcelain veneers configuration.
Sorrentino, Roberto; Apicella, Davide; Riccio, Carlo; Gherlone, Enrico; Zarone, Fernando; Aversa, Raffaella; Garcia-Godoy, Franklin; Ferrari, Marco; Apicella, Antonio
2009-11-01
This study is aimed at evaluating the biomechanical behavior of feldspathic versus alumina porcelain veneers. A 3D numerical model of a maxillary central incisor, with the periodontal ligament (PDL) and the alveolar bone was generated. Such model was made up of four main volumes: dentin, enamel, cement layer and veneer. Incisors restored with alumina and feldspathic porcelain veneers were compared with a natural sound tooth (control). Enamel, cementum, cancellous and cortical bone were considered as isotropic elastic materials; on the contrary, the tubular structure of dentin was designed as elastic orthotropic. The nonlinear visco-elatic behavior of the PDL was considered. The veneer volumes were coupled with alumina and feldspathic porcelain mechanical properties. The adhesive layers were modeled in the FE environment using spring elements. A 50N load applied at 60 degrees angle with tooth longitudinal axis was applied and validated. Compressive stresses were concentrated on the external surface of the buccal side of the veneer close to the incisal margin; such phenomenon was more evident in the presence of alumina. Tensile stresses were negligible when compared to compressive ones. Alumina and feldspathic ceramic were characterized by a different biomechanical behavior in terms of elastic deformations and stress distributions. The ultimate strength of both materials was not overcome in the performed analysis.
Valero, C.; Javierre, E.; García-Aznar, J. M.; Gómez-Benito, M. J.
2015-01-01
SUMMARY Wound healing is a process driven by biochemical and mechanical variables in which new tissue is synthesised to recover original tissue functionality. Wound morphology plays a crucial role in this process, as the skin behaviour is not uniform along different directions. In this work we simulate the contraction of surgical wounds, which can be characterised as elongated and deep wounds. Due to the regularity of this morphology, we approximate the evolution of the wound through its cross-section, adopting a plane strain hypothesis. This simplification reduces the complexity of the computational problem while maintaining allows for a thorough analysis of the role of wound depth in the healing process, an aspect of medical and computational relevance that has not yet been addressed. To reproduce wound contraction we consider the role of fibroblasts, myofibroblasts, collagen and a generic growth factor. The contraction phenomenon is driven by cell-generated forces. We postulate that these forces are adjusted to the mechanical environment of the tissue where cells are embedded through a mechanosensing and mechanotransduction mechanism. To solve the non-linear problem we use the Finite Element Method and an updated Lagrangian approach to represent the change in the geometry. To elucidate the role of wound depth and width on the contraction pattern and evolution of the involved species, we analyse different wound geometries with the same wound area. We find that deeper wounds contract less and reach a maximum contraction rate earlier than superficial wounds. PMID:24443355
Valero, C; Javierre, E; García-Aznar, J M; Gómez-Benito, M J
2014-06-01
Wound healing is a process driven by biochemical and mechanical variables in which a new tissue is synthesised to recover original tissue functionality. Wound morphology plays a crucial role in this process, as the skin behaviour is not uniform along different directions. In this work, we simulate the contraction of surgical wounds, which can be characterised as elongated and deep wounds. Because of the regularity of this morphology, we approximate the evolution of the wound through its cross section, adopting a plane strain hypothesis. This simplification reduces the complexity of the computational problem; while allows for a thorough analysis of the role of wound depth in the healing process, an aspect of medical and computational relevance that has not yet been addressed. To reproduce wound contraction, we consider the role of fibroblasts, myofibroblasts, collagen and a generic growth factor. The contraction phenomenon is driven by cell-generated forces. We postulate that these forces are adjusted to the mechanical environment of the tissue where cells are embedded through a mechanosensing and mechanotransduction mechanism. To solve the nonlinear problem, we use the finite element method (FEM) and an updated Lagrangian approach to represent the change in the geometry. To elucidate the role of wound depth and width on the contraction pattern and evolution of the involved species, we analyse different wound geometries with the same wound area. We find that deeper wounds contract less and reach a maximum contraction rate earlier than superficial wounds. Copyright © 2014 John Wiley & Sons, Ltd.
Explicit nonlinear finite element geometric analysis of parabolic leaf springs under various loads.
Kong, Y S; Omar, M Z; Chua, L B; Abdullah, S
2013-01-01
This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE) method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability.
Explicit Nonlinear Finite Element Geometric Analysis of Parabolic Leaf Springs under Various Loads
Directory of Open Access Journals (Sweden)
Y. S. Kong
2013-01-01
Full Text Available This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability.
Indian Academy of Sciences (India)
Gajbir Singh; G Venkateswara Rao
2000-08-01
The objective of the present paper is to investigate the large amplitude vibratory behaviour of unsymmetrically laminated plates. For this purpose, an efficient and accurate four-node shear flexible rectangular material finite element(MFE) with six degrees offreedom per node (three displacements $(u;v;w)$ along the $x, y$ and axes, two rotations ($\\theta_x$ and $\\theta_y$) about and axes and twist $(\\theta_{xy})$) is developed. The element assumes bi-cubic polynomial distribution with sixteen generalized undetermined coefficients for the transverse displacement. The fields for section rotations $\\theta_x$ and $\\theta_y$, and in-plane displacements and are derived using moment-shear equilibrium and in-plane equilibrium equations of composite strips along the - and -axes. The displacement field so derived not only depends on the element coordinates but is a function of extensional, bending-extensional coupling, bending and transverse shear stiffness as well. The element stiffness and mass matrices are computed numerically by employing 3 × 3 Gauss-Legendre product rules. The element is found to be free of shear locking and does not exhibit any spurious modes. In orderto compute the nonlinearfrequencies, linear mode shape corresponding to the fundamental frequency is assumed as the spatial distribution and nonlinear finite element equations are reduced to a single nonlinear second-order differential equation. This equation is solved by employing the direct numerical integration method. A series of numerical examples are solved to demonstrate the efficacy of the proposed element.
Directory of Open Access Journals (Sweden)
He-Ling Wang
2013-01-01
Full Text Available Magnetoelectric composite material is effective in transferring magnetic field into electric signal. In this paper, a nonlinear finite element method is present to model the magnetoelectric composite of ferroelectric and magnetostrictive material. In the method, the nonlinear and coupling behavior of magnetostrictive material such as Terfenol-D is considered. The nonuniform magnetic, electric, and mechanical field distributions are present. An interfacial transferring coefficient is defined to investigate the performance of interfacial mechanical coupling quantitatively, and the influence of the properties of interfacial bonding material and interfacial cracks on magnetoelectric coefficient is discussed. A new laminate ME composite of curved interface is proposed to overcome weak interfacial bonding.
Energy Technology Data Exchange (ETDEWEB)
Glass, Micheal W.; Hogan, Roy E., Jr.; Gartling, David K.
2010-03-01
The need for the engineering analysis of systems in which the transport of thermal energy occurs primarily through a conduction process is a common situation. For all but the simplest geometries and boundary conditions, analytic solutions to heat conduction problems are unavailable, thus forcing the analyst to call upon some type of approximate numerical procedure. A wide variety of numerical packages currently exist for such applications, ranging in sophistication from the large, general purpose, commercial codes, such as COMSOL, COSMOSWorks, ABAQUS and TSS to codes written by individuals for specific problem applications. The original purpose for developing the finite element code described here, COYOTE, was to bridge the gap between the complex commercial codes and the more simplistic, individual application programs. COYOTE was designed to treat most of the standard conduction problems of interest with a user-oriented input structure and format that was easily learned and remembered. Because of its architecture, the code has also proved useful for research in numerical algorithms and development of thermal analysis capabilities. This general philosophy has been retained in the current version of the program, COYOTE, Version 5.0, though the capabilities of the code have been significantly expanded. A major change in the code is its availability on parallel computer architectures and the increase in problem complexity and size that this implies. The present document describes the theoretical and numerical background for the COYOTE program. This volume is intended as a background document for the user's manual. Potential users of COYOTE are encouraged to become familiar with the present report and the simple example analyses reported in before using the program. The theoretical and numerical background for the finite element computer program, COYOTE, is presented in detail. COYOTE is designed for the multi-dimensional analysis of nonlinear heat conduction
Energy Technology Data Exchange (ETDEWEB)
Haverkort, J.W. [Centrum Wiskunde & Informatica, P.O. Box 94079, 1090 GB Amsterdam (Netherlands); Dutch Institute for Fundamental Energy Research, P.O. Box 6336, 5600 HH Eindhoven (Netherlands); Blank, H.J. de [Dutch Institute for Fundamental Energy Research, P.O. Box 6336, 5600 HH Eindhoven (Netherlands); Huysmans, G.T.A. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Pratt, J. [Dutch Institute for Fundamental Energy Research, P.O. Box 6336, 5600 HH Eindhoven (Netherlands); Koren, B., E-mail: b.koren@tue.nl [Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
2016-07-01
Numerical simulations form an indispensable tool to understand the behavior of a hot plasma that is created inside a tokamak for providing nuclear fusion energy. Various aspects of tokamak plasmas have been successfully studied through the reduced magnetohydrodynamic (MHD) model. The need for more complete modeling through the full MHD equations is addressed here. Our computational method is presented along with measures against possible problems regarding pollution, stability, and regularity. The problem of ensuring continuity of solutions in the center of a polar grid is addressed in the context of a finite element discretization of the full MHD equations. A rigorous and generally applicable solution is proposed here. Useful analytical test cases are devised to verify the correct implementation of the momentum and induction equation, the hyperdiffusive terms, and the accuracy with which highly anisotropic diffusion can be simulated. A striking observation is that highly anisotropic diffusion can be treated with the same order of accuracy as isotropic diffusion, even on non-aligned grids, as long as these grids are generated with sufficient care. This property is shown to be associated with our use of a magnetic vector potential to describe the magnetic field. Several well-known instabilities are simulated to demonstrate the capabilities of the new method. The linear growth rate of an internal kink mode and a tearing mode are benchmarked against the results of a linear MHD code. The evolution of a tearing mode and the resulting magnetic islands are simulated well into the nonlinear regime. The results are compared with predictions from the reduced MHD model. Finally, a simulation of a ballooning mode illustrates the possibility to use our method as an ideal MHD method without the need to add any physical dissipation.
Directory of Open Access Journals (Sweden)
L. F. Kong
2013-01-01
Full Text Available This paper presents a method to enhance computational efficiency of the nonlinear dynamic analysis of the large-scale deep-hole drilling machine. Based on finite element model, the drilling shaft system is constructed into Timoshenko beam element on the basis of flexible rotary shaft so as to increase the accuracy of numerical calculation. In order to save the calculation time and resources, modal synthesis technique is adopted to reduce the feature modal of linear freedom degrees of drilling shaft system. As a result, the accuracy required by the non-linear analysis will not be loss. On the basis of these, the whirling characteristics of drilling shaft system are studied under the conditions of different shaft lengths, and simultaneously, the stability patterns of drilling shaft motion and its stability region are obtained in the selected drilling depth and cutting speed parameters while drilling intersection holes.
Institute of Scientific and Technical Information of China (English)
Xingzhe Wang; Xiaojing Zheng
2009-01-01
Based on the generalized variational principle of magneto-thermo-elasticity of a ferromagnetic thin shell established (see, Analyses on nonlinear coupling of magneto-thermo-elasticity of ferromagnetic thin shell-Ⅰ), the present paper developed a finite element modeling for the mechanical-magneto-thermal multi-field coupling of a ferromagnetic thin shell. The numerical modeling composes of finite element equations for three sub-systems of magnetic, thermal and deformation fields, as well as iterative methods for nonlinearities of the geometrical large-deflection and the multi-field coupling of the ferromagnetic shell. As examples, the numerical simulations on magneto-elastic behaviors of a ferromagnetic cylindrical shell in an applied magnetic field, and magneto-thermo-elastic behaviors of the shell in applied magnetic and thermal fields are carried out. The results are in good agreement with the experimental ones.
Finite Element Solution: Nonlinear Flapping Beams for Use with Micro Air Vehicle Design
2007-03-01
used to approximate the nonlinearity in a beam is the SDOF Duffing Oscillator ӱ + C ẏ + ω0 2 y + βy3 = P sin(ωt...Hilbert Transform.......................................................................................................19 Duffing Equation...Amplitude vs Nonlinear Frequency: Fixed-Fixed Steel................................. 36 Figure 26. Duffing Equation Plot: Fixed-Fixed Steel Beam
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A numerical model is developed in this paper to calculate the bending moments of flexural members through integration in 3D solid finite element analyses according to the nonlinear constitutive model of concrete and the elastoplastic constitutive model of steel,utilizing the stress condition of the cross-section,considering the destruction characteristic of reinforced concrete members,and based on the plane cross-section assumption.The results of this model give good agreement with those of the classical me...
Payette, G. S.; Reddy, J. N.
2011-05-01
In this paper we examine the roles of minimization and linearization in the least-squares finite element formulations of nonlinear boundary-values problems. The least-squares principle is based upon the minimization of the least-squares functional constructed via the sum of the squares of appropriate norms of the residuals of the partial differential equations (in the present case we consider L2 norms). Since the least-squares method is independent of the discretization procedure and the solution scheme, the least-squares principle suggests that minimization should be performed prior to linearization, where linearization is employed in the context of either the Picard or Newton iterative solution procedures. However, in the least-squares finite element analysis of nonlinear boundary-value problems, it has become common practice in the literature to exchange the sequence of application of the minimization and linearization operations. The main purpose of this study is to provide a detailed assessment on how the finite element solution is affected when the order of application of these operators is interchanged. The assessment is performed mathematically, through an examination of the variational setting for the least-squares formulation of an abstract nonlinear boundary-value problem, and also computationally, through the numerical simulation of the least-squares finite element solutions of both a nonlinear form of the Poisson equation and also the incompressible Navier-Stokes equations. The assessment suggests that although the least-squares principle indicates that minimization should be performed prior to linearization, such an approach is often impractical and not necessary.
Directory of Open Access Journals (Sweden)
Yong Zhao
1997-01-01
Full Text Available A nonlinear three dimensional (3D single rack model and a nonlinear 3D whole pool multi-rack model are developed for the spent fuel storage racks of a nuclear power plant (NPP to determine impacts and frictional motion responses when subjected to 3D excitations from the supporting building floor. The submerged free standing rack system and surrounding water are coupled due to hydrodynamic fluid-structure interaction (FSI using potential theory. The models developed have features that allow consideration of geometric and material nonlinearities including (1 the impacts of fuel assemblies to rack cells, a rack to adjacent racks or pool walls, and rack support legs to the pool floor; (2 the hydrodynamic coupling of fuel assemblies with their storing racks, and of a rack with adjacent racks, pool walls, and the pool floor; and (3 the dynamic motion behavior of rocking, twisting, and frictional sliding of rack modules. Using these models 3D nonlinear time history dynamic analyses are performed per the U.S. Nuclear Regulatory Commission (USNRC criteria. Since few such modeling, analyses, and results using both the 3D single and whole pool multiple rack models are available in the literature, this paper emphasizes description of modeling and analysis techniques using the SOLVIA general purpose nonlinear finite element code. Typical response results with different Coulomb friction coefficients are presented and discussed.
Radiation Tolerance of Components Used in the Protection System of LHC Superconducting Elements
Denz, R
2002-01-01
A selection of electronic devices to be used for the protection of superconducting elements of the Large Hadron Collider LHC has been submitted to functional tests in the CERN TCC2 irradiation test facility. The results confirm the validity of the various designs, which are entirely based on COTS (Components-Off-The-Shelf).
Amanda E. Kowalski
2015-01-01
Insurance induces a well-known tradeoff between the welfare gains from risk protection and the welfare losses from moral hazard. Empirical work traditionally estimates each side of the tradeoff separately, potentially yielding mutually inconsistent results. I develop a nonlinear budget set model of health insurance that allows for the calculation of both sides of the tradeoff simultaneously, allowing for a relationship between moral hazard and risk protection. An important feature of this mod...
Directory of Open Access Journals (Sweden)
Hui Wang
2013-01-01
Full Text Available The boundary-type hybrid finite element formulation coupling the Kirchhoff transformation is proposed for the two-dimensional nonlinear heat conduction problems in solids with or without circular holes, and the thermal conductivity of material is assumed to be in terms of temperature change. The Kirchhoff transformation is firstly used to convert the nonlinear partial differential governing equation into a linear one by introducing the Kirchhoff variable, and then the new linear system is solved by the present hybrid finite element model, in which the proper fundamental solutions associated with some field points are used to approximate the element interior fields and the conventional shape functions are employed to approximate the element frame fields. The weak integral functional is developed to link these two fields and establish the stiffness equation with sparse and symmetric coefficient matrix. Finally, the algorithm is verified on several examples involving various expressions of thermal conductivity and existence of circular hole, and numerical results show good accuracy and stability.
Institute of Scientific and Technical Information of China (English)
Fan Yuxin; Xia Jian
2014-01-01
A fluid–structure interaction method combining a nonlinear finite element algorithm with a preconditioning finite volume method is proposed in this paper to simulate parachute tran-sient dynamics. This method uses a three-dimensional membrane–cable fabric model to represent a parachute system at a highly folded configuration. The large shape change during parachute infla-tion is computed by the nonlinear Newton–Raphson iteration and the linear system equation is solved by the generalized minimal residual (GMRES) method. A membrane wrinkling algorithm is also utilized to evaluate the special uniaxial tension state of membrane elements on the parachute canopy. In order to avoid large time expenses during structural nonlinear iteration, the implicit Hil-ber–Hughes–Taylor (HHT) time integration method is employed. For the fluid dynamic simula-tions, the Roe and HLLC (Harten–Lax–van Leer contact) scheme has been modified and extended to compute flow problems at all speeds. The lower–upper symmetric Gauss–Seidel (LU-SGS) approximate factorization is applied to accelerate the numerical convergence speed. Finally, the test model of a highly folded C-9 parachute is simulated at a prescribed speed and the results show similar characteristics compared with experimental results and previous literature.
Directory of Open Access Journals (Sweden)
Fan Yuxin
2014-12-01
Full Text Available A fluid–structure interaction method combining a nonlinear finite element algorithm with a preconditioning finite volume method is proposed in this paper to simulate parachute transient dynamics. This method uses a three-dimensional membrane–cable fabric model to represent a parachute system at a highly folded configuration. The large shape change during parachute inflation is computed by the nonlinear Newton–Raphson iteration and the linear system equation is solved by the generalized minimal residual (GMRES method. A membrane wrinkling algorithm is also utilized to evaluate the special uniaxial tension state of membrane elements on the parachute canopy. In order to avoid large time expenses during structural nonlinear iteration, the implicit Hilber–Hughes–Taylor (HHT time integration method is employed. For the fluid dynamic simulations, the Roe and HLLC (Harten–Lax–van Leer contact scheme has been modified and extended to compute flow problems at all speeds. The lower–upper symmetric Gauss–Seidel (LU-SGS approximate factorization is applied to accelerate the numerical convergence speed. Finally, the test model of a highly folded C-9 parachute is simulated at a prescribed speed and the results show similar characteristics compared with experimental results and previous literature.
Kang, Dong-Keun; Kim, Chang-Wan; Yang, Hyun-Ik
2017-01-01
In the present study we carried out a dynamic analysis of a CNT-based mass sensor by using a finite element method (FEM)-based nonlinear analysis model of the CNT resonator to elucidate the combined effects of thermal effects and nonlinear oscillation behavior upon the overall mass detection sensitivity. Mass sensors using carbon nanotube (CNT) resonators provide very high sensing performance. Because CNT-based resonators can have high aspect ratios, they can easily exhibit nonlinear oscillation behavior due to large displacements. Also, CNT-based devices may experience high temperatures during their manufacture and operation. These geometrical nonlinearities and temperature changes affect the sensing performance of CNT-based mass sensors. However, it is very hard to find previous literature addressing the detection sensitivity of CNT-based mass sensors including considerations of both these nonlinear behaviors and thermal effects. We modeled the nonlinear equation of motion by using the von Karman nonlinear strain-displacement relation, taking into account the additional axial force associated with the thermal effect. The FEM was employed to solve the nonlinear equation of motion because it can effortlessly handle the more complex geometries and boundary conditions. A doubly clamped CNT resonator actuated by distributed electrostatic force was the configuration subjected to the numerical experiments. Thermal effects upon the fundamental resonance behavior and the shift of resonance frequency due to attached mass, i.e., the mass detection sensitivity, were examined in environments of both high and low (or room) temperature. The fundamental resonance frequency increased with decreasing temperature in the high temperature environment, and increased with increasing temperature in the low temperature environment. The magnitude of the shift in resonance frequency caused by an attached mass represents the sensing performance of a mass sensor, i.e., its mass detection
Output-only identification of civil structures using nonlinear finite element model updating
Ebrahimian, Hamed; Astroza, Rodrigo; Conte, Joel P.
2015-03-01
This paper presents a novel approach for output-only nonlinear system identification of structures using data recorded during earthquake events. In this approach, state-of-the-art nonlinear structural FE modeling and analysis techniques are combined with Bayesian Inference method to estimate (i) time-invariant parameters governing the nonlinear hysteretic material constitutive models used in the FE model of the structure, and (ii) the time history of the earthquake ground motion. To validate the performance of the proposed framework, the simulated responses of a bridge pier to an earthquake ground motion is polluted with artificial output measurement noise and used to jointly estimate the unknown material parameters and the time history of the earthquake ground motion. This proof-of-concept example illustrates the successful performance of the proposed approach even in the presence of high measurement noise.
Harmonic balance finite element method applications in nonlinear electromagnetics and power systems
Lu, Junwei; Yamada, Sotoshi
2016-01-01
The first book applying HBFEM to practical electronic nonlinear field and circuit problems * Examines and solves wide aspects of practical electrical and electronic nonlinear field and circuit problems presented by HBFEM * Combines the latest research work with essential background knowledge, providing an all-encompassing reference for researchers, power engineers and students of applied electromagnetics analysis * There are very few books dealing with the solution of nonlinear electric- power-related problems * The contents are based on the authors' many years' research and industry experience; they approach the subject in a well-designed and logical way * It is expected that HBFEM will become a more useful and practical technique over the next 5 years due to the HVDC power system, renewable energy system and Smart Grid, HF magnetic used in DC/DC converter, and Multi-pulse transformer for HVDC power supply * HBFEM can provide effective and economic solutions to R&D product development * Includes Matlab e...
A Symmetric Characteristic Finite Volume Element Scheme for Nonlinear Convection-Diffusion Problems
Institute of Scientific and Technical Information of China (English)
Min Yang; Yi-rang Yuan
2008-01-01
In this paper, we implement alternating direction strategy and construct a symmetric FVE scheme for nonlinear convection-diffusion problems. Comparing to general FVE methods, our method has two advantages. First, the coefficient matrices of the discrete schemes will be symmetric even for nonlinear problems.Second, since the solution of the algebraic equations at each time step can be inverted into the solution of several one-dimensional problems, the amount of computation work is smaller. We prove the optimal H1-norm error estimates of order O(△t2 + h) and present some numerical examples at the end of the paper.
Slope Safety Calculation With A Non-Linear Mohr Criterion Using Finite Element Method
DEFF Research Database (Denmark)
Clausen, Johan; Damkilde, Lars
2005-01-01
Safety factors for soil slopes are calculated using a non-linear Mohr envelope. The often used linear Mohr-Coulomb envelope tends to overestimate the safety as the material parameters are usually determined at much higher stress levels, than those present at slope failure. Experimental data...
Adaptive Kronrod-Patterson integration of non-linear finite-element matrices
DEFF Research Database (Denmark)
Janssen, Hans
2010-01-01
Efficient simulation of unsaturated moisture flow in porous media is of great importance in many engineering fields. The highly non-linear character of unsaturated flow typically gives sharp moving moisture fronts during wetting and drying of materials with strong local moisture permeability and ...
THE FINITE ELEMENT METHODS FOR A CLASS OF NONLINEAR PARABOLIC EQUATIONS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Error estimates are established for the finite dement methods to solve a class of second or der nonlinear parabolic equations. Optimal rates of convergence in L2-and H1-norms are derived. Meanwhile,the schenes are second order correct in time.
Nonlinear blade element-momentum analysis of Betz-Goldstein rotors
DEFF Research Database (Denmark)
Wood, D. H.; Okulov, Valery
2017-01-01
•We analyze Betz-Goldstein (BG) rotors for maximum power at any tip speed ratio and number of blades.•We prove that Glauert's incorporation of tip loss in the blade torque and thrust equation are correct.•We show the nonlinear angular momentum terms can contribute 12% of the total torque....
Slope Safety Calculation With A Non-Linear Mohr Criterion Using Finite Element Method
DEFF Research Database (Denmark)
Clausen, Johan; Damkilde, Lars
2005-01-01
Safety factors for soil slopes are calculated using a non-linear Mohr envelope. The often used linear Mohr-Coulomb envelope tends to overestimate the safety as the material parameters are usually determined at much higher stress levels, than those present at slope failure. Experimental data...
Review of Rover fuel element protective coating development at Los Alamos
Wallace, Terry C.
1991-01-01
The Los Alamos Scientific Laboratory (LASL) entered the nuclear propulsion field in 1955 and began work on all aspects of a nuclear propulsion program with a target exhaust temperature of about 2750 K. A very extensive chemical vapor deposition coating technology for preventing catastrophic corrosion of reactor core components by the high temperature, high pressure hydrogen propellant gas was developed. Over the 17-year term of the program, more than 50,000 fuel elements were coated and evaluated. Advances in performance were achieved only through closely coupled interaction between the developing fuel element fabrication and protective coating technologies. The endurance of fuel elements in high temperature, high pressure hydrogen environment increased from several minutes at 2000 K exit gas temperature to 2 hours at 2440 K exit gas temperature in a reactor test and 10 hours at 2350 K exit gas temperature in a hot gas test. The purpose of this paper is to highlight the rationale for selection of coating materials used (NbC and ZrC), identify critical fuel element-coat interactions that had to be modified to increase system performance, and review the evolution of protective coating technology.
Modification of radiobiological effects of 171 MeV protons by elements of physical protection
Bulinina, Taisia; Shurshakov, Vyacheslav; Ivanov, Alexander; Molokanov, Alexander
2016-07-01
Space radiation includes protons of various energies. Physical protection is effective in the case of low energy protons (50-100 MeV) and becomes insufficient for radiation with a high part of high-energy protons. In the experiment performed on outbred mice, the purpose of the study was to evaluate the radiobiological effect of 171 MeV protons and protons modified by elements of physical protection of the spacecraft, on a complex of indicators of the functional condition of the system hematopoiesis and the central nervous system in 24 hours after irradiation at 20 cGy dose. The spacecraft radiation protection elements used in the experiment were a construction of wet hygiene wipes called a «protective curtain», and a glass plate imitating an ISS window. Mass thickness of the " protective curtain" in terms of water equivalent was ̴ 6,2 g/cm2. Physical shielding along the path of 171 MeV protons increases their linear energy transfer leading to the absorbed dose elevation and strengthening of the radiobiological effect. In the experiment, the two types of shielding together raised the absorbed dose from 20 to 23.2 cGy. Chemically different materials (glass and water in the wipes) were found to exert unequal modifying effects on physical and biological parameters of the proton-irradiated mice. There was a distinct dose-dependent reduction of bone marrow cellularity within the dose range from 20 cGy to 23.2 cGy in 24 hours after exposure. No modifying effect of the radiation protection elements on spontaneous motor activity was discovered when compared with entrance protons. The group of animals protected by the glass plate exhibited normal orientative-trying reactions and weakened grip with the forelimbs. The effects observed in the experiment indicate the necessity to carry out comprehensive radiobiological researches (physical, biological and mathematical) in assessing the effects of physical protection, that are actual for ensuring radiation safety of crews in
Institute of Scientific and Technical Information of China (English)
Jin Wencheng; Zhou Xiaoyong; Li Na
2008-01-01
A numerical model is developed in this paper to calculate the bending moments of flexural members through integration in 3D solid finite element analyses according to the nonlinear constitutive model of concrete and the elastoplastic constitutive model of steel, utilizing the stress condition of the cross-section, considering the destruction characteristic of reinforced concrete members, and based on the plane cross-section assumption. The results of this model give good agreement with those of the classical method. Consequently, we can also deduce the corresponding numerical expression for eccentrically loaded members according to the analysis method.
Zhang, Shengyong
2017-07-01
Spot welding has been widely used for vehicle body construction due to its advantages of high speed and adaptability for automation. An effort to increase the stiffness-to-weight ratio of spot-welded structures is investigated based upon nonlinear finite element analysis. Topology optimization is conducted for reducing weight in the overlapping regions by choosing an appropriate topology. Three spot-welded models (lap, doubt-hat and T-shape) that approximate “typical” vehicle body components are studied for validating and illustrating the proposed method. It is concluded that removing underutilized material from overlapping regions can result in a significant increase in structural stiffness-to-weight ratio.
Stenvall, A.; Tarhasaari, T.
2010-07-01
Due to the rapid development of personal computers from the beginning of the 1990s, it has become a reality to simulate current penetration, and thus hysteresis losses, in superconductors with other than very simple one-dimensional (1D) Bean model computations or Norris formulae. Even though these older approaches are still usable, they do not consider, for example, multifilamentary conductors, local critical current dependency on magnetic field or varying n-values. Currently, many numerical methods employing different formulations are available. The problem of hysteresis losses can be scrutinized via an eddy current formulation of the classical theory of electromagnetism. The difficulty of the problem lies in the non-linear resistivity of the superconducting region. The steep transition between the superconducting and the normal states often causes convergence problems for the most common finite element method based programs. The integration methods suffer from full system matrices and, thus, restrict the number of elements to a few thousands at most. The so-called T - phiv formulation and the use of edge elements, or more precisely Whitney 1-forms, within the finite element method have proved to be a very suitable method for hysteresis loss simulations of different geometries. In this paper we consider making such finite element method software from first steps, employing differential geometry and forms.
Energy Technology Data Exchange (ETDEWEB)
Stenvall, A; Tarhasaari, T, E-mail: antti.stenvall@tut.f [Electromagnetics, Tampere University of Technology, PO Box 692, 33101 Tampere (Finland)
2010-07-15
Due to the rapid development of personal computers from the beginning of the 1990s, it has become a reality to simulate current penetration, and thus hysteresis losses, in superconductors with other than very simple one-dimensional (1D) Bean model computations or Norris formulae. Even though these older approaches are still usable, they do not consider, for example, multifilamentary conductors, local critical current dependency on magnetic field or varying n-values. Currently, many numerical methods employing different formulations are available. The problem of hysteresis losses can be scrutinized via an eddy current formulation of the classical theory of electromagnetism. The difficulty of the problem lies in the non-linear resistivity of the superconducting region. The steep transition between the superconducting and the normal states often causes convergence problems for the most common finite element method based programs. The integration methods suffer from full system matrices and, thus, restrict the number of elements to a few thousands at most. The so-called T - {psi} formulation and the use of edge elements, or more precisely Whitney 1-forms, within the finite element method have proved to be a very suitable method for hysteresis loss simulations of different geometries. In this paper we consider making such finite element method software from first steps, employing differential geometry and forms.
Gras, Laure-Lise; Mitton, David; Crevier-Denoix, Nathalie; Laporte, Sébastien
2012-01-01
Most recent finite element models that represent muscles are generic or subject-specific models that use complex, constitutive laws. Identification of the parameters of such complex, constitutive laws could be an important limit for subject-specific approaches. The aim of this study was to assess the possibility of modelling muscle behaviour in compression with a parametric model and a simple, constitutive law. A quasi-static compression test was performed on the muscles of dogs. A parametric finite element model was designed using a linear, elastic, constitutive law. A multi-variate analysis was performed to assess the effects of geometry on muscle response. An inverse method was used to define Young's modulus. The non-linear response of the muscles was obtained using a subject-specific geometry and a linear elastic law. Thus, a simple muscle model can be used to have a bio-faithful, biomechanical response.
Horowitz, A; Sheinman, I; Lanir, Y; Perl, M; Sideman, S
1988-02-01
A two-dimensional incompressible plane-stress finite element is formulated for the simulation of the passive-state mechanics of thin myocardial strips. The formulation employs a total Lagrangian and materially nonlinear approach, being based on a recently proposed structural material law, which is derived from the histological composition of the tissue. The ensuing finite element allows to demonstrate the mechanical properties of a single myocardial layer containing uniformly directed fibers by simulating various loading cases such as tension, compression and shear. The results of these cases show that the fiber direction is considerably stiffer than the cross-fiber direction, that there is significant coupling between these two directions, and that the shear stiffness of the tissue is lower than its tensile and compressive stiffness.
Krasilenko, Vladimir G.; Nikolsky, Alexander I.; Lazarev, Alexander A.; Lazareva, Maria V.
2008-03-01
In the paper the actuality of neurophysiologically motivated neuron arrays with flexibly programmable functions and operations with possibility to select required accuracy and type of nonlinear transformation and learning are shown. We consider neurons design and simulation results of multichannel spatio-time algebraic accumulation - integration of optical signals. Advantages for nonlinear transformation and summation - integration are shown. The offered circuits are simple and can have intellectual properties such as learning and adaptation. The integrator-neuron is based on CMOS current mirrors and comparators. The performance: consumable power - 100...500 μW, signal period- 0.1...1ms, input optical signals power - 0.2...20 μW time delays - less 1μs, the number of optical signals - 2...10, integration time - 10...100 of signal periods, accuracy or integration error - about 1%. Various modifications of the neuron-integrators with improved performance and for different applications are considered in the paper.
Tang, Henry H.; Orndoff, Evelyne S.; Thomas, Gretchen A.
2009-01-01
This paper discusses the effort in evaluating and selecting a light weight impact protection material for the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS) conceptual packaging study. A light weight material capable of holding and protecting the components inside the PLSS is required to demonstrate the viability of the flexible PLSS packaging concept. The material needs to distribute, dissipate, and absorb the impact energy of the PLSS falling on the lunar surface. It must also be very robust and function in the extreme lunar thermal vacuum environment for up to one hundred Extravehicular Activity (EVA) missions. This paper documents the performance requirements for selecting a foam protection material, and the methodologies for evaluating commercial off-the-shelf (COTS) foam protection materials. It also presents the materials properties test results and impact drop test results of the various foam materials evaluated in the study. The findings from this study suggest that a foam based flexible protection system is a viable solution for PLSS packaging. However, additional works are needed to optimize COTS foam properties or to develop a composite foam system that will meet all the performance requirements for the CSSE PLSS flexible packaging.
Ender, I A; Flegontova, E Yu; Gerasimenko, A B
2016-01-01
An algorithm for sequential calculation of non-isotropic matrix elements of the collision integral which are necessary for the solution of the non-linear Boltzmann equation by moment method is proposed. Isotropic matrix elements that we believe are known, are starting ones. The procedure is valid for any interaction law and any mass ratio of the colliding particles.
Atluri, S. N.; Nakagaki, M.; Kathiresan, K.
1980-01-01
In this paper, efficient numerical methods for the analysis of crack-closure effects on fatigue-crack-growth-rates, in plane stress situations, and for the solution of stress-intensity factors for arbitrary shaped surface flaws in pressure vessels, are presented. For the former problem, an elastic-plastic finite element procedure valid for the case of finite deformation gradients is developed and crack growth is simulated by the translation of near-crack-tip elements with embedded plastic singularities. For the latter problem, an embedded-elastic-singularity hybrid finite element method, which leads to a direct evaluation of K-factors, is employed.
Lu, Shijun; Wang, Zhendong; Ni, Xiaoyu; Wang, Lin
2013-02-01
To reconstruct a three-dimensional nonlinear finite element model of mandibular teeth with three-pieces segment arch, and analyze the mechanical properties of intrusive arch and the biomechanical characteristics of three-pieces segment arch. Three-dimensional nonlinear finite element model of mandible with three-pieces segment arch was reconstructed by multi-slice spiral CT scanning, Mimics, CATIA and Anasys software. Then, the mechanical properties of intrusive arch, the movement trend and stress distribution of three-pieces segment arch were calculated by Anasys software. In the range of 5 degrees-25 degrees, with the degree of intrusive arch increased, the force of intrusive arch also increased rapidly. The maximal force was 0.604 8 N in 30 degrees; the force was about 0.59 N in 30 degrees-65 degrees range. In condition of three-pieces segment arch mechanics, lateral incisor tipped labially and intruded; the first moral tipped distally and rotating; other teeth did not move clearly. The largest stress distribution in the whole arch was in the one-third labial cervical area of the lateral incisor root and the root bifurcations of first moral. Under an appropriate intrusive force, three-pieces segment arch can intrude incisors and control the extrusion of posterior teeth. It can be used to correct the deep overbite, especially with high mandibular planes, gummy smile or adult patients.
Energy Technology Data Exchange (ETDEWEB)
Esfandiar, Habib; KoraYem, Moharam Habibnejad [Islamic Azad University, Tehran (Iran, Islamic Republic of)
2015-09-15
In this study, the researchers try to examine nonlinear dynamic analysis and determine Dynamic load carrying capacity (DLCC) in flexible manipulators. Manipulator modeling is based on Timoshenko beam theory (TBT) considering the effects of shear and rotational inertia. To get rid of the risk of shear locking, a new procedure is presented based on mixed finite element formulation. In the method proposed, shear deformation is free from the risk of shear locking and independent of the number of integration points along the element axis. Dynamic modeling of manipulators will be done by taking into account small and large deformation models and using extended Hamilton method. System motion equations are obtained by using nonlinear relationship between displacements-strain and 2nd PiolaKirchoff stress tensor. In addition, a comprehensive formulation will be developed to calculate DLCC of the flexible manipulators during the path determined considering the constraints end effector accuracy, maximum torque in motors and maximum stress in manipulators. Simulation studies are conducted to evaluate the efficiency of the method proposed taking two-link flexible and fixed base manipulators for linear and circular paths into consideration. Experimental results are also provided to validate the theoretical model. The findings represent the efficiency and appropriate performance of the method proposed.
Joglekar, D. M.; Mitra, M.
2015-11-01
A breathing crack, due to its bilinear stiffness characteristics, modifies the frequency spectrum of a propagating dual-frequency elastic wave, and gives rise to sidebands around the probing frequency. This paper presents an analytical-numerical method to investigate such nonlinear frequency mixing resulting from the modulation effects induced by a breathing crack in 1D waveguides, such as axial rods and the Euler-Bernoulli beams. A transverse edge-crack is assumed to be present in both the waveguides, and the local flexibility caused by the crack is modeled using an equivalent spring approach. A simultaneous treatment of both the waveguides, in the framework of the Fourier transform based spectral finite element method, is presented for analyzing their response to a dual frequency excitation applied in the form of a tone-burst signal. The intermittent contact between the crack surfaces is accounted for by introducing bilinear contact forces acting at the nodes of the damage spectral element. Subsequently, an iterative approach is outlined for solving the resulting system of nonlinear simultaneous equations. Applicability of the proposed method is demonstrated by considering several test cases. The existence of sidebands and the higher order harmonics is confirmed in the frequency domain response of both the waveguides under investigation. A qualitative comparison with the previous experimental observations accentuates the utility of the proposed solution method. Additionally, the influence of the two constituent frequencies in the dual frequency excitation is assessed by varying the relative strengths of their amplitudes. A brief parametric study is performed for bringing out the effects of the relative crack depth and crack location on the degree of modulation, which is quantified in terms of the modulation parameter. Results of the present investigation can find their potential use in providing an analytical-numerical support to the studies geared towards the
Directory of Open Access Journals (Sweden)
S.C. Chin
2012-05-01
Full Text Available This study presents the experimental study and numerical analysis of Reinforced Concrete (RC beams with large square openings placed in the shear region, at a distance 0.5d and d away from the support, strengthened by Carbon Fiber Reinforced Polymer (CFRP laminates. This research aims to investigate the strength losses in RC beam due to the presence of large square openings placed at two different locations in shear region. Also, in order to re-gain the beam structural capacity loss due to the openings, strengthening by CFRP laminates around the openings were studied. A total of six RC beams were tested to failure under four point loading including control beams, un-strengthened and strengthened RC beams with large square openings in shear region at a distance 0.5d and d away from the support. The CFRP strengthening configuration considered in this study was a full wrapping system around the square openings. A nonlinear finite element program, ATENA was used to validate the results of the tested beams. Comparisons between the finite element predictions and experimental results in terms of crack patterns and load deflection relationships are presented. The crack pattern results of the finite element model show good agreement with the experimental data. The load midspan deflection curves of the finite element models exhibited a stiffer result compared to the experimental beams. The possible reason may be due to the perfect bond assumption between the concrete and steel reinforcement.
Development of a non-linear finite element modelling of the below-knee prosthetic socket interface.
Zhang, M; Lord, M; Turner-Smith, A R; Roberts, V C
1995-12-01
A non-linear finite element model has been established to predict the pressure and shear stress distribution at the limb-socket interface in below-knee amputees with consideration of the skin-liner interface friction and slip. In this model, the limb tissue and socket liner were respectively meshed into 954 and 450 three-dimensional eight-node isoparametric brick elements, based on measurements of an individual's amputated limb surface; the bone was meshed into three-dimensional six-node triangular prism elements, based on radiographic measurements of the individual's residual limb. The socket shell was assumed to be a rigid boundary. An important feature of this model is the use of 450 interface elements (ABAQUS INTER4) which mimic the interface friction condition. The results indicate that a maximum pressure of 226 kPa, shear stress of 53 kPa and less than 4 mm slip exist at the skin-liner interface when the full body weight of 800 N is applied to the limb. The results also show that the coefficient of friction is a very sensitive parameter in determining the interface pressures, shear stresses and slip. With the growth of coefficient of friction, the shear stresses will increase, while the pressure and slip will decrease.
Matsuura, Yusuke; Kuniyoshi, Kazuki; Suzuki, Takane; Ogawa, Yasufumi; Sukegawa, Koji; Rokkaku, Tomoyuki; Thoreson, Andrew Ryan; An, Kai-Nan; Takahashi, Kazuhisa
2015-01-01
The feasibility of a user-specific finite element model for predicting the in situ strength of the radius after implantation of bone plates for open fracture reduction was established. The effect of metal artifact in CT imaging was characterized. The results were verified against biomechanical test data. Fourteen cadaveric radii were divided into two groups: (1) intact radii for evaluating the accuracy of radial diaphysis strength predictions with finite element analysis and (2) radii with a locking plate affixed for evaluating metal artifact. All bones were imaged with CT. In the plated group, radii were first imaged with the plates affixed (for simulating digital plate removal). They were then subsequently imaged with the locking plates and screws removed (actual plate removal). Fracture strength of the radius diaphysis under axial compression was predicted with a three-dimensional, specimen-specific, nonlinear finite element analysis for both the intact and plated bones (bones with and without the plate captured in the scan). Specimens were then loaded to failure using a universal testing machine to verify the actual fracture load. In the intact group, the physical and predicted fracture loads were strongly correlated. For radii with plates affixed, the physical and predicted (simulated plate removal and actual plate removal) fracture loads were strongly correlated. This study demonstrates that our specimen-specific finite element analysis can accurately predict the strength of the radial diaphysis. The metal artifact from CT imaging was shown to produce an overestimate of strength.
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.
Nonlinear solid finite element analysis of mitral valves with heterogeneous leaflet layers
Prot, V.; Skallerud, B.
2009-02-01
An incompressible transversely isotropic hyperelastic material for solid finite element analysis of a porcine mitral valve response is described. The material model implementation is checked in single element tests and compared with a membrane implementation in an out-of-plane loading test to study how the layered structures modify the stress response for a simple geometry. Three different collagen layer arrangements are used in finite element analysis of the mitral valve. When the leaflets are arranged in two layers with the collagen on the ventricular side, the stress in the fibre direction through the thickness in the central part of the anterior leaflet is homogenized and the peak stress is reduced. A simulation using membrane elements is also carried out for comparison with the solid finite element results. Compared to echocardiographic measurements, the finite element models bulge too much in the left atrium. This may be due to evidence of active muscle fibres in some parts of the anterior leaflet, whereas our constitutive modelling is based on passive material.
Gu, Zhiping
This paper extends Riccati transfer matrix method to the transient and stability analysis of large scale rotor-bearing systems with strong nonlinear elements, and proposes a mode summation-transfer matrix method, in which the field transfer matrix of a distributed mass uniform shaft segment is obtained with the aid of the idea of mode summation and Newmark beta formulation, and the Riccati transfer matrix method is adopted to stablize the boundary value problem of the nonlinear systems. In this investigation, the real nonlinearity of the strong nonlinear elements is considered, not linearized, and the advantages of the Riccati transfer matrix are retained. So, this method is especially applicable to analyze the transient response and stability of large-scale rotor-bear systems with strong nonlinear elements. One example, a single-spool rotating system with strong nonlinear elements, is given. The obtained results show that this method is superior to that of Gu and Chen (1990) in accuracy, stability, and economy.
Short-circuit protection of LLC resonant converter using voltages across resonant tank elements
Directory of Open Access Journals (Sweden)
Denys Igorovych Zaikin
2015-06-01
Full Text Available This paper describes two methods for the short-circuit protection of the LLC resonant converter. One of them uses the voltage across the capacitor and the other uses the voltage across the inductor of the resonant tank. These voltages can be processed (integrated or differentiated to recover the resonant tank current. The two circuits illustrated in the described methods make it possible to develop a robust LLC converter design and to avoid using lossy current measurement elements, such as a shunt resistor or current transformer. The methods also allow measuring resonant tank current without breaking high-current paths and connecting the measuring circuit in parallel with the inductor or capacitor of the resonant tank. Practical implementations of these indirect current measurements have been experimentally tested for the short-circuit protection of the 1600 W LLC converter.
Finley, John W
2003-07-01
Research supports the hypothesis that one's diet has a great impact on his or her risk of cancer. Many studies have found that increased fruit and vegetable intake decreases the risk of cancer. Cruciferous vegetables such as broccoli and cauliflower seem to be especially protective against cancer. Most studies show that phytochemicals in crucifers up-regulate many detoxification enzyme systems in the animal that consumes them. Recent reports of the molecular events involved in the activation of a gene promoter called the antioxidant responsive element have begun to provide clues as to how a single substance may induce a battery of many genes.
Sobota, Paul; Dornisch, Wolfgang; Klinkel, Sven
2016-08-01
The present approach deals with the dynamical analysis of thin structures using an isogeometric Reissner-Mindlin shell formulation. Here, a consistent and a lumped mass matrix are employed for the implicit time integration method. The formulation allows for large displacements and finite rotations. The Rodrigues formula, which incorporates the axial vector is used for the rotational description. It necessitates an interpolation of the director vector in the current configuration. Two concept for the interpolation of the director vector are presented. They are denoted as continuous interpolation method and discrete interpolation method. The shell formulation is based on the assumption of zero stress in thickness direction. In the present formulation an interface to 3D nonlinear material laws is used. It leads to an iterative procedure at each integration point. Here, a J2 plasticity material law is implemented. The suitability of the developed shell formulation for natural frequency analysis is demonstrated in numerical examples. Transient problems undergoing large deformations in combination with nonlinear material behavior are analyzed. The effectiveness, robustness and superior accuracy of the two interpolation methods of the shell director vector are investigated and are compared to numerical reference solutions.
Saito, Shinji; Miyoshi, Yoshizumi; Seki, Kanako
2016-07-01
Wave-particle interactions with whistler chorus waves are believed to provide a primary acceleration for electrons in the outer radiation belt. Previous models for flux enhancement of the radiation belt have assumed the stochastic process as a diffusion manner of successive random-phase interactions, but physical mechanisms for the acceleration are not fully incorporated in these models because of the lack of a nonlinear scattering process. Here we report rapid increase in relativistic electron flux by using an innovative computer simulation model that incorporates not only diffusive process but also nonlinear scattering processes. The simulations show that three types of scattering simultaneously occur, which are diffusive, phase trapping, and phase bunching. It is found that the phase trapping is the most efficient mechanism to produce the MeV electrons rapidly in the scattering processes. The electrons are accelerated from 400 keV to over 1 MeV in time scale less than 60 s. On the other hand, as the phase trapping is suppressed by the breaking of relative phase angle between waves and gyrating electrons during the interaction, the increase of electron flux at MeV energy is clearly reduced. Our simulations conclude that the phase-trapping process causes a significant effect for the increase in relativistic electron flux and suggest that a quasi-linear diffusion model is not always valid to fully describe the relativistic electron acceleration.
DEFF Research Database (Denmark)
Yoon, Gil Ho; Joung, Young Soo; Kim, Yoon Young
2005-01-01
The topology design optimization of “three-dimensional geometrically-nonlinear” continuum structures is still a difficult problem not only because of its problem size but also the occurrence of unstable continuum finite elements during the design optimization. To overcome this difficulty...
Czachor, Marek
1994-01-01
A new version of NLQM is formulated in terms of the generalized Nambu dynamics. The generalization is free from the difficulties of earlier approaches. The paper is a second part of "Elements of NLQM (I): NL Schrodinger equation and two-level atoms".
Looking-Free Mixed hp Finite Element Methods for Linear and Geometrically Nonlinear Elasticity
1997-06-09
hp mixed methods has been addressed by Stenberg and Suri[20]. They identify sufficient conditions for selecting mixed method spaces on parallelogram...spaces of piecewise polynomials. Math. Modeling Num. Anal., 19:111-143, 1985. [20] R. Stenberg and M. Suri. Mixed hp finite element methods for
Arteaga, Santiago Egido
1998-12-01
The steady-state Navier-Stokes equations are of considerable interest because they are used to model numerous common physical phenomena. The applications encountered in practice often involve small viscosities and complicated domain geometries, and they result in challenging problems in spite of the vast attention that has been dedicated to them. In this thesis we examine methods for computing the numerical solution of the primitive variable formulation of the incompressible equations on distributed memory parallel computers. We use the Galerkin method to discretize the differential equations, although most results are stated so that they apply also to stabilized methods. We also reformulate some classical results in a single framework and discuss some issues frequently dismissed in the literature, such as the implementation of pressure space basis and non- homogeneous boundary values. We consider three nonlinear methods: Newton's method, Oseen's (or Picard) iteration, and sequences of Stokes problems. All these iterative nonlinear methods require solving a linear system at every step. Newton's method has quadratic convergence while that of the others is only linear; however, we obtain theoretical bounds showing that Oseen's iteration is more robust, and we confirm it experimentally. In addition, although Oseen's iteration usually requires more iterations than Newton's method, the linear systems it generates tend to be simpler and its overall costs (in CPU time) are lower. The Stokes problems result in linear systems which are easier to solve, but its convergence is much slower, so that it is competitive only for large viscosities. Inexact versions of these methods are studied, and we explain why the best timings are obtained using relatively modest error tolerances in solving the corresponding linear systems. We also present a new damping optimization strategy based on the quadratic nature of the Navier-Stokes equations, which improves the robustness of all the
Directory of Open Access Journals (Sweden)
Mrkša Milutin
2007-01-01
Full Text Available The aim of this article is presentation a realistic status of environment elements in specific reservation of nature Stari Begej - Carska Bara. This article is present exchanged status of elements whose after effect operated the tourism activity. Principles of protection is present, too. Specific reservation of nature is area which comprehend one or more extra value of nature. Principles of protection are necessary for route, control and following.
Modeling of Nonlinear Elements During Lightning Overvoltage Simulations%雷电过电压仿真中非线性元件的建模
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The paper presents some problems of lightning overvoltage modeling in transmission lines with nonlinear elements. The presented results were obtained mostly for fast front transients of subsequent lightning return stroke currents. The effectiveness of numerical algorithms of nonlinear models and possibilities of their development for such transients are analyzed. Computer simulations carried out by application of EMTP show that nonlinear models of back-flashover and ZnO arresters work properly, while the implemented corona model can not be used for relatively large peak values of subsequent lightning return-stroke currents.
Shih, Kao-Shang; Hsu, Ching-Chi; Hsu, Tzu-Pin; Hou, Sheng-Mou; Liaw, Chen-Kun
2014-02-01
Femoral shaft fractures can be treated using retrograde interlocking nailing systems; however, fracture nonunion still occurs. Dynamic fixation techniques, which remove either the proximal or distal locking screws, have been used to solve the problem of nonunion. In addition, a surgical rule for dynamic fixation techniques has been defined based on past clinical reports. However, the biomechanical performance of the retrograde interlocking nailing systems with either the traditional static fixation technique or the dynamic fixation techniques has not been investigated by using nonlinear numerical modeling. Three-dimensional nonlinear finite element models were developed, and the implant strength, fixation stability, and contact area of the fracture surfaces were evaluated. Three types of femoral shaft fractures (a proximal femoral shaft fracture, a middle femoral shaft fracture, and a distal femoral shaft fracture) fixed by three fixation techniques (insertion of all the locking screws, removal of the proximal locking screws, or removal of the distal locking screws) were analyzed. The results showed that the static fixation technique resulted in sufficient fixation stability and that the dynamic fixation techniques decreased the failure risk of the implant and produced a larger contact area of the fracture surfaces. The outcomes of the current study could assist orthopedic surgeons in comprehending the biomechanical performances of both static and dynamic fixation techniques. In addition, the surgeons could also select a fixation technique based on the specific patient situation using the numerical outcomes of this study.
Nonlinear ion-acoustic waves in a degenerate plasma with nuclei of heavy elements
Energy Technology Data Exchange (ETDEWEB)
Hossen, M. A., E-mail: armanplasma@gmail.com; Mamun, A. A., E-mail: mamun-phys@yahoo.co.uk [Department of Physics, Jahangirnagar University, Savar, Dhaka-1342 (Bangladesh)
2015-10-15
The ion-acoustic (IA) solitary waves propagating in a fully relativistic degenerate dense plasma (containing relativistic degenerate electron and ion fluids, and immobile nuclei of heavy elements) have been theoretically investigated. The relativistic hydrodynamic model is used to derive the Korteweg-de Vries (K-dV) equation by the reductive perturbation method. The stationary solitary wave solution of this K-dV equation is obtained to characterize the basic features of the IA solitary structures that are found to exist in such a degenerate plasma. It is found that the effects of electron dynamics, relativistic degeneracy of the plasma fluids, stationary nuclei of heavy elements, etc., significantly modify the basic properties of the IA solitary structures. The implications of this results in astrophysical compact objects like white dwarfs are briefly discussed.
Lafontaine, N. M.; Rossi, R.; Cervera, M.; Chiumenti, M.
2015-03-01
Low-order finite elements face inherent limitations related to their poor convergence properties. Such difficulties typically manifest as mesh-dependent or excessively stiff behaviour when dealing with complex problems. A recent proposal to address such limitations is the adoption of mixed displacement-strain technologies which were shown to satisfactorily address both problems. Unfortunately, although appealing, the use of such element technology puts a large burden on the linear algebra, as the solution of larger linear systems is needed. In this paper, the use of an explicit time integration scheme for the solution of the mixed strain-displacement problem is explored as an alternative. An algorithm is devised to allow the effective time integration of the mixed problem. The developed method retains second order accuracy in time and is competitive in terms of computational cost with the standard irreducible formulation.
Al-Rousan, R. Z.
2015-09-01
The main objective of this study was to assess the effect of the number and schemes of carbon-fiber-reinforced polymer (CFRP) sheets on the capacity of bending moment, the ultimate displacement, the ultimate tensile strain of CFRP, the yielding moment, concrete compression strain, and the energy absorption of RC beams and to provide useful relationships that can be effectively utilized to determine the required number of CFRP sheets for a necessary increase in the flexural strength of the beams without a major loss in their ductility. To accomplish this, various RC beams, identical in their geometric and reinforcement details and having different number and configurations of CFRP sheets, are modeled and analyzed using the ANSYS software and a nonlinear finite-element analysis.
Townsend, Molly T; Sarigul-Klijn, Nesrin
2016-01-01
Simplified material models are commonly used in computational simulation of biological soft tissue as an approximation of the complicated material response and to minimize computational resources. However, the simulation of complex loadings, such as long-duration tissue swelling, necessitates complex models that are not easy to formulate. This paper strives to offer the updated Lagrangian formulation comprehensive procedure of various non-linear material models for the application of finite element analysis of biological soft tissues including a definition of the Cauchy stress and the spatial tangential stiffness. The relationships between water content, osmotic pressure, ionic concentration and the pore pressure stress of the tissue are discussed with the merits of these models and their applications.
DEFF Research Database (Denmark)
Larsen, Jon Steffen; Santos, Ilmar
2015-01-01
An efficient finite element scheme for solving the non-linear Reynolds equation for compressible fluid coupled to compliant structures is presented. The method is general and fast and can be used in the analysis of airfoil bearings with simplified or complex foil structure models. To illustrate...... the computational performance, it is applied to the analysis of a compliant foil bearing modelled using the simple elastic foundation model. The model is derived and perturbed using complex notation. Top foil sagging effect is added to the bump foil compliance in terms of a close-form periodic function. For a foil...... bearing utilized in an industrial turbo compressor, the influence of boundary conditions and sagging on the pressure profile, shaft equilibrium position and dynamic coefficients is numerically simulated. The proposed scheme is faster, leading to the conclusion that it is suitable, not only for steady...
Directory of Open Access Journals (Sweden)
E. D. Resende
2007-09-01
Full Text Available The freezing process is considered as a propagation problem and mathematically classified as an "initial value problem." The mathematical formulation involves a complex situation of heat transfer with simultaneous changes of phase and abrupt variation in thermal properties. The objective of the present work is to solve the non-linear heat transfer equation for food freezing processes using orthogonal collocation on finite elements. This technique has not yet been applied to freezing processes and represents an alternative numerical approach in this area. The results obtained confirmed the good capability of the numerical method, which allows the simulation of the freezing process in approximately one minute of computer time, qualifying its application in a mathematical optimising procedure. The influence of the latent heat released during the crystallisation phenomena was identified by the significant increase in heat load in the early stages of the freezing process.
Vertical slice modelling of nonlinear Eady waves using a compatible finite element method
Yamazaki, Hiroe; Shipton, Jemma; Cullen, Michael J. P.; Mitchell, Lawrence; Cotter, Colin J.
2017-08-01
A vertical slice model is developed for the Euler-Boussinesq equations with a constant temperature gradient in the direction normal to the slice (the Eady-Boussinesq model). The model is a solution of the full three-dimensional equations with no variation normal to the slice, which is an idealised problem used to study the formation and subsequent evolution of weather fronts. A compatible finite element method is used to discretise the governing equations. To extend the Charney-Phillips grid staggering in the compatible finite element framework, we use the same node locations for buoyancy as the vertical part of velocity and apply a transport scheme for a partially continuous finite element space. For the time discretisation, we solve the semi-implicit equations together with an explicit strong-stability-preserving Runge-Kutta scheme to all of the advection terms. The model reproduces several quasi-periodic lifecycles of fronts despite the presence of strong discontinuities. An asymptotic limit analysis based on the semi-geostrophic theory shows that the model solutions are converging to a solution in cross-front geostrophic balance. The results are consistent with the previous results using finite difference methods, indicating that the compatible finite element method is performing as well as finite difference methods for this test problem. We observe dissipation of kinetic energy of the cross-front velocity in the model due to the lack of resolution at the fronts, even though the energy loss is not likely to account for the large gap on the strength of the fronts between the model result and the semi-geostrophic limit solution.
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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.
Wood, Chris C; Gross, Mart R
2008-02-01
Conservation biologists mostly agree on the need to identify and protect biodiversity below the species level but have not yet resolved the best approach. We addressed 2 issues relevant to this debate. First, we distinguished between the abstract goal of preserving the maximum amount of unique biodiversity and the pragmatic goal of minimizing the loss of ecological goods and services given that further loss of biodiversity seems inevitable. Second, we distinguished between the scientific task of assessing extinction risk and the normative task of choosing targets for protection. We propose that scientific advice on extinction risk be given at the smallest meaningful scale: the elemental conservation unit (ECU). An ECU is a demographically isolated population whose probability of extinction over the time scale of interest (say 100 years) is not substantially affected by natural immigration from other populations. Within this time frame, the loss of an ECU would be irreversible without human intervention. Society's decision to protect an ECU ought to reflect human values that have social, economic, and political dimensions. Scientists can best inform this decision by providing advice about the probability that an ECU will be lost and the ecological and evolutionary consequences of that loss in a form that can be integrated into landscape planning. The ECU approach provides maximum flexibility to decision makers and ensures that the scientific task of assessing extinction risk informs, but remains distinct from, the normative social challenge of setting conservation targets.
Nonlinear Materials Characterization Facility
Federal Laboratory Consortium — The Nonlinear Materials Characterization Facility conducts photophysical research and development of nonlinear materials operating in the visible spectrum to protect...
Efficient Non-Linear Finite Element Implementation of Elasto-Plasticity for Geotechnical Problems
DEFF Research Database (Denmark)
Clausen, Johan
of foundations, mainly due to its simplicity which allows simple solutions with simple geometries. But for complex geometries a numerical solution is needed. It turns out that the apparently simple Mohr-Coulomb model is non-trivial to implement in the finite-element method. This is due to the fact that the Mohr...... with the safety factors obtained with a linear Mohr envelope, with which they are directly comparable, when the presented method is used. The classical problem of yield surfaces with corners and apexes is elaborated upon. A small modification to the formulation of the constitutive matrices on corners and apexes...
Parametric nonlinear lumped element model for circular CMUTs in collapsed mode.
Aydoğdu, Elif; Ozgurluk, Alper; Atalar, Abdullah; Köymen, Hayrettin
2014-01-01
We present a parametric equivalent circuit model for a circular CMUT in collapsed mode. First, we calculate the collapsed membrane deflection, utilizing the exact electrical force distribution in the analytical formulation of membrane deflection. Then we develop a lumped element model of collapsed membrane operation. The radiation impedance for collapsed mode is also included in the model. The model is merged with the uncollapsed mode model to obtain a simulation tool that handles all CMUT behavior, in transmit or receive. Large- and small-signal operation of a single CMUT can be fully simulated for any excitation regime. The results are in good agreement with FEM simulations.
Almeida, EDGARD S.; Spilker, ROBERT L.
1997-01-01
This paper addresses finite element-based computational models for the three-dimensional, (3-D) nonlinear analysis of soft hydrated tissues, such as the articular cartilage in diarthrodial joints, under physiologically relevant loading conditions. A biphasic continuum description is used to represent the soft tissue as a two-phase mixture of incompressible, inviscid fluid and a hyperelastic solid. Alternate mixed-penalty and velocity-pressure finite element formulations are used to solve the nonlinear biphasic governing equations, including the effects of a strain-dependent permeability and a hyperelastic solid phase under finite deformation. The resulting first-order nonlinear system of equations is discretized in time using an implicit finite difference scheme, and solved using the Newton-Raphson method. Using a discrete divergence operator, an equivalence is shown between the mixed-penalty method and a penalty method previously derived by Suh et al. [1]. In Part II [2], the mixed-penalty and velocity-pressure formulations are used to develop two-dimensional (2-D) quadrilateral and triangular elements and 3-D hexahedral and tetrahedral elements. Numerical examples, including those representative of soft tissue material testing and simple human joints, are used to validate the formulations and to illustrate their applications. A focus of this work is the comparison of alternate formulations for nonlinear problems. While it is demonstrated that both formulations produce a range of converging elements, the velocity-pressure formulation is found to be more efficient computationally.
Directory of Open Access Journals (Sweden)
Binyamin Binyamin
2016-12-01
Full Text Available Traffic accidents are terrible scourge that occur in many countries, specially for developing countries where transportation affairs like tangled yarn. Besides functioning as an engine compartment cover, the hood of modern compact SUV can also help to manage the impact energy of a pedestrian’s head in a vehicle-pedestrian impact. This paper presents outer hood design of Esemka R2 that has a potential to improve hood’s ability and also to absorb the impact energy of a pedestrian’s head. The developed method for the design of an outer hood configuration aims to provide a robust design and homogeneous of Head Injury Criterion (HIC for impact position at WAD 1000 and three different thicknesses (1.25 mm, 1.35 mm & 1.50 mm of outer hood panel of Esemka R2 compact SUV, taking into consideration the limited space available for deformation. The non-linear Finite Element Analysis (FEA software (Explicit Dynamics was used in this research to simulate the testing procedurs of head impact for child pedestrian. The results show that the average of comparison dimensional of outer hood panel of Esemka R2 was 4.89 mm. The minimum of deformation space meet the requirement for HIC value which required obtaining robust and homogeneous head impact performance. Outer hood thickness and materials were identified as the factors to influence the stress and HIC value of the hood. By comparing all outer hood panels, aluminium alloy as the best selected material which has the lowest value is 32.78% for the pedestrian protection.
Indian Academy of Sciences (India)
Pankaj Kumar; S Narayanan
2006-08-01
The response of a structural system to white noise excitation (delta-correlated) constitutes a Markov vector process whose transitional probability density function (TPDF) is governed by both the forward Fokker–Planck and backward Kolmogorov equations. Numerical solution of these equations by ﬁnite element and ﬁnite difference methods for dynamical systems of engineering interest has been hindered by the problem of dimensionality. In this paper numerical solution of the stationary and transient form of the Fokker–Planck (FP) equation corresponding to two state nonlinear systems is obtained by standard sequential ﬁnite element method (FEM) using C° shape function and Crank–Nicholson time integration scheme. The method is applied to Van-der-Pol and Dufﬁng oscillators providing good agreement between results obtained by it and exact results. An extension of the ﬁnite difference discretization scheme developed by Spencer, Bergman and Wojtkiewicz is also presented. This paper presents an extension of the ﬁnite difference method for the solution of FP equation up to four dimensions. The difﬁculties associated in extending these methods to higher dimensional systems are discussed.
Institute of Scientific and Technical Information of China (English)
朱卫平; 黄黔
2002-01-01
The finite-element-displacement-perturbation method (FEDPM)for thegeometric nonlinear behaviors of shells of revolution subjected to pure bending moments orlateral forces in one of their meridional planes ( Ⅰ ) was employed to calculate the stressdistributions and the stiffness of the bellows. Firstly, by applying the first-orderperturbation solution ( the linear solution ) of the FEDPM to the bellows, the obtainedresults were compared with those of the general solution and the initial parameter integrationsolution proposed by the present authors earlier, as well as of the experiments and the FEAby others. It is shown that the FEDPM is with good precision and reliability, and as it waspointed out in ( Ⅰ ) the abrupt changes of the meridian curvature of bellows would not affectthe use of the usual straight element. Then the nonlinear behaviors of the bellows werediscussed. As expected, the nonlinear effects mainly come from the bellows ring plate, andthe wider the ring plate is, the stronger the nonlinear effects are. Contrarily, the vanishingof the ring plate, like the C-shaped bellows, the nonlinear effects almost vanish. Inaddition, when the pure bending moments act on the bellows, each convolution has thesame stress distributions calculated by the linear solution and other linear theories, but bythe present nonlinear solution they vary with respect to the convolutions of the bellows. Yetfor most bellows, the linear solutions are valid in practice.
Karimi, Hossein; Nikmehr, Saeid; Khodapanah, Ehsan
2016-09-01
In this paper, we develop a B-spline finite-element method (FEM) based on a locally modal wave propagation with anisotropic perfectly matched layers (PMLs), for the first time, to simulate nonlinear and lossy plasmonic waveguides. Conventional approaches like beam propagation method, inherently omit the wave spectrum and do not provide physical insight into nonlinear modes especially in the plasmonic applications, where nonlinear modes are constructed by linear modes with very close propagation constant quantities. Our locally modal B-spline finite element method (LMBS-FEM) does not suffer from the weakness of the conventional approaches. To validate our method, first, propagation of wave for various kinds of linear, nonlinear, lossless and lossy materials of metal-insulator plasmonic structures are simulated using LMBS-FEM in MATLAB and the comparisons are made with FEM-BPM module of COMSOL Multiphysics simulator and B-spline finite-element finite-difference wide angle beam propagation method (BSFEFD-WABPM). The comparisons show that not only our developed numerical approach is computationally more accurate and efficient than conventional approaches but also it provides physical insight into the nonlinear nature of the propagation modes.
How simple can nonlinear finite element modelling be for structural concrete?
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Argirova, G.
2014-12-01
Full Text Available This paper discusses on the required level of simplicity for suitable modelling of structural concrete. Traditional equilibrium- based approaches (as strut-and-tie models are too coarse in some cases, as they account for the cracking state of concrete in a sometimes excessively simplified manner. The alternative of complex nonlinear numerical modelling is also not always satisfactory for design as the number of parameters required, their definition and the sensitivity of the structural response to them is complex and requires a high level of experience. Contrary to these approaches, this paper introduces the elastic plastic stress field method. This method is grounded on the theory of plasticity but allows considering deformation compatibility. The results are consistent both in terms of the strength and deformation field of the member. It also has the advantage of requiring only two physical material properties (modulus of elasticity and plastic strength which can be easily determined by designers.Este artículo discute sobre el nivel de sencillez ideal para un análisis no lineal de elementos de hormigón estructural. Los métodos de cálculo basados únicamente en condiciones de equilibrio (como los modelos de bielas-y-tirantes no son siempre adecuados ya que el estado de fisuración del hormigón se considera a veces de una manera excesivamente simplificada. Los análisis no lineales complejos tampoco son siempre adecuados, ya que el número de parámetros requeridos, su definición y la sensibilidad de la respuesta del elemento a sus variaciones requieren una gran experiencia. Como alternativa, se presenta el método de los campos de tensiones elasto-plásticos. Este método se basa en la teoría de la plasticidad pero incorporando condiciones de compatibilidad. Los resultados son coherentes en términos de resistencia y de deformaciones. Además, sólo necesita la definición de dos parámetros mecánicos (módulo de elasticidad y
Abd El Baky, Hussien
This research work is devoted to theoretical and numerical studies on the flexural behaviour of FRP-strengthened concrete beams. The objectives of this research are to extend and generalize the results of simple experiments, to recommend new design guidelines based on accurate numerical tools, and to enhance our comprehension of the bond performance of such beams. These numerical tools can be exploited to bridge the existing gaps in the development of analysis and modelling approaches that can predict the behaviour of FRP-strengthened concrete beams. The research effort here begins with the formulation of a concrete model and development of FRP/concrete interface constitutive laws, followed by finite element simulations for beams strengthened in flexure. Finally, a statistical analysis is carried out taking the advantage of the aforesaid numerical tools to propose design guidelines. In this dissertation, an alternative incremental formulation of the M4 microplane model is proposed to overcome the computational complexities associated with the original formulation. Through a number of numerical applications, this incremental formulation is shown to be equivalent to the original M4 model. To assess the computational efficiency of the incremental formulation, the "arc-length" numerical technique is also considered and implemented in the original Bazant et al. [2000] M4 formulation. Finally, the M4 microplane concrete model is coded in FORTRAN and implemented as a user-defined subroutine into the commercial software package ADINA, Version 8.4. Then this subroutine is used with the finite element package to analyze various applications involving FRP strengthening. In the first application a nonlinear micromechanics-based finite element analysis is performed to investigate the interfacial behaviour of FRP/concrete joints subjected to direct shear loadings. The intention of this part is to develop a reliable bond--slip model for the FRP/concrete interface. The bond
Analysis of noncoplanar pressurized laminations in X2 steel pipes by non-linear finite element
Energy Technology Data Exchange (ETDEWEB)
Morales, Alfredo [Instituto Tecnologico de Puebla (Mexico). Dept. de Posgrado; Gonzalez, Jorge L.; Hallen, Jose M. [Instituto Politecnico Nacional (Mexico). Escuela Superior de Ingenieria Quimica e Industrias Extractivas (ESIQIE). Dept. de Ingenieria Metalurgica
2005-07-01
Hydrogen induced cracking is of great interest in the mechanical integrity assessment of sour gas pipelines. Multiple stepwise cracks with internal pressure called laminations are often observed in pipelines and their interaction and coalescence may significantly affect the residual strength of the pipes. In this work, the interacting fields of non coplanar pressurized laminations in the wall of a pipe under pressure are analyzed by non-lineal finite element, considering an isotropic hardening law and the real tensile properties of the X52 steel. The results are presented as the evolution of the stress fields in the interlaminar region as a function of the pressure inside the laminations. It is found that for two approaching stepwise laminations the critical pressure follows a hyperbolic type law, thus the effect of the lamination length is principal for greater lengths and for shorter lengths the effect is minimum. The critical pressure is defined as pressure inside the lamination that causes plastification of the interlaminar region. (author)
Coarse-grained molecular dynamics: Nonlinear finite elements and finite temperature
Energy Technology Data Exchange (ETDEWEB)
Rudd, R E; Broughton, J Q
2005-05-30
Coarse-grained molecular dynamics (CGMD) is a technique developed as a concurrent multiscale model that couples conventional molecular dynamics (MD) to a more coarse-grained description of the periphery. The coarse-grained regions are modeled on a mesh in a formulation that generalizes conventional finite element modeling (FEM) of continuum elasticity. CGMD is derived solely from the MD model, however, and has no continuum parameters. As a result, it provides a coupling that is smooth and provides control of errors that arise at the coupling between the atomistic and coarse-grained regions. In this article, we elaborate on the formulation of CGMD, describing in detail how CGMD is applied to anharmonic solids and finite temperature simulations. As tests of CGMD, we present in detail the calculation of the phonon spectra for solid argon and tantalum in 3D, demonstrating how CGMD provides a better description of the elastic waves than that provided by FEM. We also present elastic wave scattering calculations that show the elastic wave scattering is more benign in CGMD than FEM. We also discuss the dependence of scattering on the properties of the mesh. We introduce a rigid approximation to CGMD that eliminates internal relaxation, similar to the Quasicontinuum technique, and compare it to the full CGMD.
Directory of Open Access Journals (Sweden)
Ignat’ev Aleksandr Vladimirovich
2016-02-01
Full Text Available The most widely used numerical method used in linear calculation of building structures is finite element method in traditional form of displacements. Different software is developed on its basis. Though it is only possible to check the certainty of these numerical solutions, especially of non-linear tasks of engineering structures’ deformation by the coincidence of the results obtained by two different methods. The authors solved geometrically nonlinear task of the static deformation of a flat hinged-rod system consisting of five linear elastic rods undergoing great tension-compression strains. The solution was obtained basing on the finite element method in the form of classical mixed method developed by the authors. The set of all equilibrium states of the system, both stable and unstable, and all the limit points were found. The certainty of the solution was approved by the coincidence of the results obtained by other authors basing on traditional finite element method in displacements.
Zingan, Valentin Nikolaevich
This work develops a discontinuous Galerkin finite element discretization of non- linear hyperbolic conservation equations with efficient and robust high order stabilization built on an entropy-based artificial viscosity approximation. The solutions of equations are represented by elementwise polynomials of an arbitrary degree p > 0 which are continuous within each element but discontinuous on the boundaries. The discretization of equations in time is done by means of high order explicit Runge-Kutta methods identified with respective Butcher tableaux. To stabilize a numerical solution in the vicinity of shock waves and simultaneously preserve the smooth parts from smearing, we add some reasonable amount of artificial viscosity in accordance with the physical principle of entropy production in the interior of shock waves. The viscosity coefficient is proportional to the local size of the residual of an entropy equation and is bounded from above by the first-order artificial viscosity defined by a local wave speed. Since the residual of an entropy equation is supposed to be vanishingly small in smooth regions (of the order of the Local Truncation Error) and arbitrarily large in shocks, the entropy viscosity is almost zero everywhere except the shocks, where it reaches the first-order upper bound. One- and two-dimensional benchmark test cases are presented for nonlinear hyperbolic scalar conservation laws and the system of compressible Euler equations. These tests demonstrate the satisfactory stability properties of the method and optimal convergence rates as well. All numerical solutions to the test problems agree well with the reference solutions found in the literature. We conclude that the new method developed in the present work is a valuable alternative to currently existing techniques of viscous stabilization.
Directory of Open Access Journals (Sweden)
E. Çelebi
2012-11-01
Full Text Available The objective of this paper focuses primarily on the numerical approach based on two-dimensional (2-D finite element method for analysis of the seismic response of infinite soil-structure interaction (SSI system. This study is performed by a series of different scenarios that involved comprehensive parametric analyses including the effects of realistic material properties of the underlying soil on the structural response quantities. Viscous artificial boundaries, simulating the process of wave transmission along the truncated interface of the semi-infinite space, are adopted in the non-linear finite element formulation in the time domain along with Newmark's integration. The slenderness ratio of the superstructure and the local soil conditions as well as the characteristics of input excitations are important parameters for the numerical simulation in this research. The mechanical behavior of the underlying soil medium considered in this prediction model is simulated by an undrained elasto-plastic Mohr-Coulomb model under plane-strain conditions. To emphasize the important findings of this type of problems to civil engineers, systematic calculations with different controlling parameters are accomplished to evaluate directly the structural response of the vibrating soil-structure system. When the underlying soil becomes stiffer, the frequency content of the seismic motion has a major role in altering the seismic response. The sudden increase of the dynamic response is more pronounced for resonance case, when the frequency content of the seismic ground motion is close to that of the SSI system. The SSI effects under different seismic inputs are different for all considered soil conditions and structural types.
Asiminei, Aida Georgeta; Van der Perre, Georges; Verpoest, Ignace; Goffin, Jan
2009-01-01
This paper is focused on understanding the mechanism that gives the bicycle helmet the role of protecting the head during an impact. The finite element method is used here as a first step in the helmet optimisation and improvement process. The relation between different helmet mechanical parameters and the risk of head injury during the impact is described using MSC Marc Mentat finite element software. The reduction in resulting head linear acceleration by more than 80% and in resulting stres...
Non-linear finite element model to assess the effect of tendon forces on the foot-ankle complex.
Morales-Orcajo, Enrique; Souza, Thales R; Bayod, Javier; Barbosa de Las Casas, Estevam
2017-08-11
A three-dimensional foot finite element model with actual geometry and non-linear behavior of tendons is presented. The model is intended for analysis of the lower limb tendon forces effect in the inner foot structure. The geometry of the model was obtained from computational tomographies and magnetic resonance images. Tendon tissue was characterized with the first order Ogden material model based on experimental data from human foot tendons. Kinetic data was employed to set the load conditions. After model validation, a force sensitivity study of the five major foot extrinsic tendons was conducted to evaluate the function of each tendon. A synergic work of the inversion-eversion tendons was predicted. Pulling from a peroneus or tibialis tendon stressed the antagonist tendons while reducing the stress in the agonist. Similar paired action was predicted for the Achilles tendon with the tibialis anterior. This behavior explains the complex control motion performed by the foot. Furthermore, the stress state at the plantar fascia, the talocrural joint cartilage, the plantar soft tissue and the tendons were estimated in the early and late midstance phase of walking. These estimations will help in the understanding of the functional role of the extrinsic muscle-tendon-units in foot pronation-supination. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.
Thorvaldsen, Tom; Osnes, Harald; Sundnes, Joakim
2005-12-01
In this paper we present a mixed finite element method for modeling the passive properties of the myocardium. The passive properties are described by a non-linear, transversely isotropic, hyperelastic material model, and the myocardium is assumed to be almost incompressible. Single-field, pure displacement-based formulations are known to cause numerical difficulties when applied to incompressible or slightly compressible material cases. This paper presents an alternative approach in the form of a mixed formulation, where a separately interpolated pressure field is introduced as a primary unknown in addition to the displacement field. Moreover, a constraint term is included in the formulation to enforce (almost) incompressibility. Numerical results presented in the paper demonstrate the difficulties related to employing a pure displacement-based method, applying a set of physically relevant material parameter values for the cardiac tissue. The same problems are not experienced for the proposed mixed method. We show that the mixed formulation provides reasonable numerical results for compressible as well as nearly incompressible cases, also in situations of large fiber stretches. There is good agreement between the numerical results and the underlying analytical models.
Energy Technology Data Exchange (ETDEWEB)
Karimi, Alireza; Navidbakhsh, Mahdi, E-mail: mnavid@iust.ac.ir; Razaghi, Reza
2014-09-01
There have been intensive efforts to find a suitable kinetic energy absorbing material for helmet and bulletproof vest design. Polyvinyl alcohol (PVA) sponge is currently in extensive use as scaffolding material for tissue engineering applications. PVA can also be employed instead of commonly use kinetic energy absorbing materials to increase the kinetic energy absorption capacity of current helmet and bulletproof vest materials owing to its excellent mechanical properties. In this study, a combined hexahedral finite element (FE) model is established to determine the potential protection ability of PVA sponge in controlling the level of injury for gunshot wounds to the human mandible. Digital computed tomography data for the human mandible are used to establish a three-dimensional FE model of the human mandible. The mechanism by which a gunshot injures the protected mandible by PVA sponge is dynamically simulated using the LS-DYNA code under two different shot angles. The stress distributions in different parts of the mandible and sponge after injury are also simulated. The modeling results regardless of shot angle reveal that the substantial amount of kinetic energy of the steel ball (67%) is absorbed by the PVA sponge and, consequently, injury severity of the mandible is significantly decreased. The highest energy loss (170 J) is observed for the impact at entry angle of 70°. The results suggest the application of the PVA sponge as an alternative reinforcement material in helmet and bulletproof vest design to absorb most of the impact energy and reduce the transmitted load. - Highlights: • The ability of PVA sponge to control the injury to the human mandible is computed. • A hexahedral FE model for gunshot wounds to the human mandible is established. • The kinetic energy and injury severity of the mandible is minimized by the sponge. • The highest energy loss (170 J) is observed for the impact at entry angle of 70°. • PVA suggests as an alternative
Directory of Open Access Journals (Sweden)
WangPeng
2016-01-01
Full Text Available A family of prismatic and hexahedral solid‒shell (SHB elements with their linear and quadratic versions is presented in this paper to model thin 3D structures. Based on reduced integration and special treatments to eliminate locking effects and to control spurious zero-energy modes, the SHB solid‒shell elements are capable of modeling most thin 3D structural problems with only a single element layer, while describing accurately the various through-thickness phenomena. In this paper, the SHB elements are combined with fully 3D behavior models, including orthotropic elastic behavior for composite materials and anisotropic plastic behavior for metallic materials, which allows describing the strain/stress state in the thickness direction, in contrast to traditional shell elements. All SHB elements are implemented into ABAQUS using both standard/quasi-static and explicit/dynamic solvers. Several benchmark tests have been conducted, in order to first assess the performance of the SHB elements in quasi-static and dynamic analyses. Then, deep drawing of a hemispherical cup is performed to demonstrate the capabilities of the SHB elements in handling various types of nonlinearities (large displacements and rotations, anisotropic plasticity, and contact. Compared to classical ABAQUS solid and shell elements, the results given by the SHB elements show good agreement with the reference solutions.
Energy Technology Data Exchange (ETDEWEB)
Azadi, Mohammad [Sharif University of Technology, Tehran (Iran, Islamic Republic of); Azadi, Mahboobeh [Shiraz University, Shiraz (Iran, Islamic Republic of)
2009-10-15
Nonlinear transient heat transfer and thermoelastic stress analyses of a thick-walled FGM cylinder with temperature dependent materials are performed by using the Hermitian transfinite element method. Temperature-dependency of the material properties has not been taken into account in transient thermoelastic analysis, so far. Due to the mentioned dependency, the resulting governing FEM equations of transient heat transfer are highly nonlinear. Furthermore, in all finite element analysis performed so far in the field, Lagrangian elements have been used. To avoid an artificial local heat source at the mutual boundaries of the elements, Hermitian elements are used instead in the present research. Another novelty of the present paper is simultaneous use of the transfinite element method and updating technique. Time variations of the temperature, displacements, and stresses are obtained through a numerical Laplace inversion. Finally, results obtained considering the temperature-dependency of the material properties are compared with those derived based on temperature independency assumption. Furthermore, the temperature distribution and the radial and circumferential stresses are investigated versus time, geometrical parameters and index of power law. Results reveal that the temperature-dependency effect is significant
Horowitz, A; Sheinman, I; Lanir, Y
1988-02-01
A three dimensional incompressible and geometrically as well as materially nonlinear finite element is formulated for future implementation in models of cardiac mechanics. The stress-strain relations in the finite element are derived from a recently proposed constitutive law which is based on the histological composition of the myocardium. The finite element is formulated for large deformations and considers incompressibility by introducing the hydrostatic pressure as an additional variable. The results of passive loading cases simulated by this element allow to analyze the mechanical properties of ventricular wall segments, the main of which are that the circumferential direction is stiffer than the longitudinal one, that its shear stiffness is considerably lower than its tensile and compressive stiffness and that, due to its mechanically prominent role, the collagenous matrix may affect the myocardial perfusion.
Energy Technology Data Exchange (ETDEWEB)
Mohanty, Subhasish, E-mail: smohanty@anl.gov; Majumdar, Saurindranath
2015-10-15
Highlights: • High temperature gas cooled reactor. • Finite element based stress analysis. • H-451 graphite. • Irradiation creep model. • Graphite reflector stress analysis. - Abstract: Irradiation creep plays a major role in the structural integrity of the graphite components in high temperature gas cooled reactors. Finite element procedures combined with a suitable irradiation creep model can be used to simulate the time-integrated structural integrity of complex shapes, such as the reactor core graphite reflector and fuel bricks. In the present work a comparative study was undertaken to understand the effect of linear and nonlinear irradiation creep on results of finite element based stress analysis. Numerical results were generated through finite element simulations of a typical graphite reflector.
Energy Technology Data Exchange (ETDEWEB)
Belzile, Nelson [Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6 (Canada)]. E-mail: nbelzile@laurentian.ca; Wu Gaojun [Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6 (Canada); Chen, Yu-Wei [Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6 (Canada); Appanna, Vasu D. [Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6 (Canada)
2006-08-31
A study on the assimilation and detoxification of selenium and mercury and on the interaction between these two elements was conducted on Pseudomonas fluorescens. P. fluorescens was able to convert separately both elements to their elemental forms, which are less toxic and biologically less available. To study the converting mechanism of selenite to elemental Se, cells were grown in the presence of various selenite concentrations and several parameters such as extracellular protein concentrations, pH, carbohydrate concentrations, isocitrate dehydrogenase (ICDH) and malic enzyme were monitored. Transmission electron microscopy (TEM) and various analytical methods were applied to confirm the interaction between selenium and cell. The former appeared as a red precipitate localized predominantly in the consumed culture medium. P. fluorescens also resisted to the toxic effect of mercury by converting Hg{sup 2+} to the volatile and less toxic form Hg . Mercury reductase was likely responsible for the conversion of Hg{sup 2+} to Hg . More importantly, the interaction between mercury and selenium was also studied. The presence of selenite significantly reduced the accumulation of mercury in P. fluorescens. It was also interesting to note that mercury appeared to behave as a protecting agent against selenium intoxication as the bioaccumulation of Se was also inhibited by this metal. The formation of Se-Hg complexes could explain this mutual protective effect. No precipitate of elemental Se could be detected when Hg was present in the cultures.
2015-12-24
research apart from the FDTD method used in the past. After the spatial discretization issue is addressed, the four partial differential equations (PDEs...that govern the coupled electromagnetic-plasma system are converted into four ordinary differential equations (ODEs) which can be integrated...particle diffusion equation . The nonlinear dependence of the plasma parameters on the electromagnetic fields makes the entire system highly nonlinear
Novel Fabrication Approach for SiC/SiC Thermal Protection System Elements Project
National Aeronautics and Space Administration — Durable high temperature materials are required for structural thermal protection systems (TPS) that exhibit a structural load carrying capability at temperatures in...
He, Quanyuan; Kim, Hyeung; Huang, Rui; Lu, Weisi; Tang, Mengfan; Shi, Fengtao; Yang, Dong; Zhang, Xiya; Huang, Junjiu; Liu, Dan; Songyang, Zhou
2015-09-03
In mammals, DNA methylation is essential for protecting repetitive sequences from aberrant transcription and recombination. In some developmental contexts (e.g., preimplantation embryos) DNA is hypomethylated but repetitive elements are not dysregulated, suggesting that alternative protection mechanisms exist. Here we explore the processes involved by investigating the role of the chromatin factors Daxx and Atrx. Using genome-wide binding and transcriptome analysis, we found that Daxx and Atrx have distinct chromatin-binding profiles and are co-enriched at tandem repetitive elements in wild-type mouse ESCs. Global DNA hypomethylation further promoted recruitment of the Daxx/Atrx complex to tandem repeat sequences, including retrotransposons and telomeres. Knockdown of Daxx/Atrx in cells with hypomethylated genomes exacerbated aberrant transcriptional de-repression of repeat elements and telomere dysfunction. Mechanistically, Daxx/Atrx-mediated repression seems to involve Suv39h recruitment and H3K9 trimethylation. Our data therefore suggest that Daxx and Atrx safeguard the genome by silencing repetitive elements when DNA methylation levels are low.
Energy Technology Data Exchange (ETDEWEB)
Puso, M; Maker, B N; Ferencz, R M; Hallquist, J O
2000-03-24
This report provides the NIKE3D user's manual update summary for changes made from version 3.0.0 April 24, 1995 to version 3.3.6 March 24,2000. The updates are excerpted directly from the code printed output file (hence the Courier font and formatting), are presented in chronological order and delineated by NIKE3D version number. NIKE3D is a fully implicit three-dimensional finite element code for analyzing the finite strain static and dynamic response of inelastic solids, shells, and beams. Spatial discretization is achieved by the use of 8-node solid elements, 2-node truss and beam elements, and 4-node membrane and shell elements. Thirty constitutive models are available for representing a wide range of elastic, plastic, viscous, and thermally dependent material behavior. Contact-impact algorithms permit gaps, frictional sliding, and mesh discontinuities along material interfaces. Several nonlinear solution strategies are available, including Full-, Modified-, and Quasi-Newton methods. The resulting system of simultaneous linear equations is either solved iteratively by an element-by-element method, or directly by a direct factorization method.
Institute of Scientific and Technical Information of China (English)
朱卫平; 黄黔
2002-01-01
In order to analyze bellows effectively and practically, the finite-element-displacement-perturbation method (FEDPM) is proposed for the geometric nonlinearbehaviors of shells of revolution subjected to pure bending moments or lateral forces in one of their meridional planes. The formulations are mainly based upon the idea of perturba-tion that the nodal displacement vector and the nodal force vector of each finite elementare expanded by taking root-mean-square value of circumferential strains of the shells as aperturbation parameter. The load steps and the iteration times are not cs arbitrary andunpredictable as in usual nonlinear analysis. Instead, there are certain relations betweenthe load steps and the displacement increments, and no need of iteration for each loadstep. Besides, in the formulations, the shell is idealized into a series of conical frusta for the convenience of practice, Sander' s nonlinear geometric equations of moderate smallrotation are used, and the shell made of more than one material ply is also considered.
Energy Technology Data Exchange (ETDEWEB)
Shariyat, M. [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)], E-mail: m_shariyat@yahoo.com
2009-04-15
In the present paper, an algorithm for nonlinear transient behavior analysis of thick functionally graded cylindrical vessels or pipes with temperature-dependent material properties under thermo-mechanical loads is presented. In contrast to researches presented so far, a Hermitian transfinite element method is proposed to improve the accuracy and to prevent artificial interference or cohesion formation at the mutual boundaries of the elements. Time variations of the temperatures, displacements, and stresses are obtained through a numerical Laplace inversion. Another novelty of the present research is using the transfinite element method to solve nonlinear problems. A sensitivity analysis includes investigating effects of the volume fraction index, dimensions, and temperature-dependency of the material properties is performed. Results confirm the efficiency of the present algorithm and reveal the significant effects of the temperature-dependency of the material properties and the elastic wave reflections and interferences on the responses. In comparison to other techniques, the present technique may be used to obtain relatively accurate and stable results in a less computational time.
RESEARCH AND DEVELOPMENT OF THREE NONLINEAR BEAM-COLUMN ELEMENTS%三种非线性梁柱单元的研究及单元开发
Institute of Scientific and Technical Information of China (English)
陈学伟; 韩小雷; 孙思为
2011-01-01
Since the elastoplastic damages occur in concrete structures and components in plastic stage under a severe earthquake, precise prediction of nonlinear behavior of structures in the earthquake is important to assess the seismic safety of the structures. A structural elastoplastic analysis program MEASP which bases on macro elements is compiled with object oriented language and three kinds of nonlinear beam-column elements are implemented in MESAP: stiffness-based fiber element, flexibility-based fiber element and flexibility-based plastic hinge element. Differences between the elements are compared by case study. Four kinds of integration methods for obtaining the flexibility matrix of the plastic hinge element are studied. The results show that a flexibility-based plastic binge element is an accurate macro element with low computation cost. Only two integration points are required by the Gauss-Radau integration method handling a nonlinear analysis. It is accuracy and its computational efficiency is applicable in the entire structure nonlinear analysis and practical in engineering.%罕遇地震作用下混凝土梁柱构件易进入塑性阶段而发生弹塑性损伤,正确地模拟结构进入非线性状态后的力学行为对评价结构的抗震安全性具有重要的意义.通过面向对象语言编制了基于宏观单元的结构弹塑性分析软件平台MESAP,增加了三种非线性梁柱单元:基于刚度法纤维单元、基于柔度法纤维单元及基于柔度法的塑性铰单元.通过算例分析三种非线性梁柱单元之间的差异.基于柔度法塑性铰单元的柔度矩阵积分方法可分为四种,通过算例讨论四种积分方法的差异.算例分析结果表明基于柔度法的塑性铰单元是一种精度高具计算成本低的宏观单元.Gauss-Radau积分法要求进行塑性计算的积分点只有两个,该积分法计算效率较高且精度良好,适用于整体结构的非线性分析之中,具有实际工程应用意义.
Directory of Open Access Journals (Sweden)
Petrova Anna A.
2016-01-01
Full Text Available The theoretical rationale for the structural layout of a testing bench with zirconium dioxide heating elements on the basis of modelling radiative-conductive heat transfer are presented. The numerical simulation of radiative-conductive heat transfer for the two-dimensional scaled model of the testing segment with the finite-element analysis software package Ansys 15.0 are performed. The simulation results showed that for the selected layout of the heaters the temperature non-uniformity along the length of the sample over time will not exceed 3 % even at a temperature of 2000 K.
You, Yi-Zhuang; Bi, Zhen; Mao, Dan; Xu, Cenke
2016-03-01
We propose a series of simple two-dimensional (2D) lattice interacting fermion models that we demonstrate at low energy describe bosonic symmetry-protected topological (SPT) states and quantum phase transitions between them. This is because due to interaction, the fermions are gapped both at the boundary of the SPT states and at the bulk quantum phase transition, thus these models at low energy can be described completely by bosonic degrees of freedom. We show that the bulk of these models is described by a Sp (N ) principal chiral model with a topological Θ term, whose boundary is described by a Sp (N ) principal chiral model with a Wess-Zumino-Witten term at level 1. The quantum phase transition between SPT states in the bulk is tuned by a particular interaction term, which corresponds to tuning Θ in the field theory, and the phase transition occurs at Θ =π . The simplest version of these models with N =1 is equivalent to the familiar O(4) nonlinear sigma model (NLSM) with a topological term, whose boundary is a (1 +1 )D conformal field theory with central charge c =1 . After breaking the O(4) symmetry to its subgroups, this model can be viewed as bosonic SPT states with U(1), or Z2 symmetries, etc. All of these fermion models, including the bulk quantum phase transitions, can be simulated with the determinant quantum Monte Carlo method without the sign problem. Recent numerical results strongly suggest that the quantum disordered phase of the O(4) NLSM with precisely Θ =π is a stable (2 +1 )D conformal field theory with gapless bosonic modes.
Lapa, Matthew F.; Hughes, Taylor L.
2017-08-01
We canonically quantize O (D +2 ) nonlinear sigma models (NLSMs) with a theta term on arbitrary smooth, closed, connected, oriented D -dimensional spatial manifolds M , with the goal of proving the suitability of these models for describing symmetry-protected topological (SPT) phases of bosons in D spatial dimensions. We show that in the disordered phase of the NLSM, and when the coefficient θ of the theta term is an integer multiple of 2 π , the theory on M has a unique ground state and a finite energy gap to all excitations. We also construct the ground state wave functional of the NLSM in this parameter regime, and we show that it is independent of the metric on M and given by the exponential of a Wess-Zumino term for the NLSM field, in agreement with previous results on flat space. Our results show that the NLSM in the disordered phase and at θ =2 π k , k ∈Z , has a symmetry-preserving ground state but no topological order (i.e., no topology-dependent ground state degeneracy), making it an ideal model for describing SPT phases of bosons. Thus, our work places previous results on SPT phases derived using NLSMs on solid theoretical ground. To canonically quantize the NLSM on M , we use Dirac's method for the quantization of systems with second class constraints, suitably modified to account for the curvature of space. In a series of four Appendixes, we provide the technical background needed to follow the discussion in the main sections of the paper.
Jonker, J.B.; Meijaard, J.P.
2013-01-01
A beam finite element formulation for large deflection problems in the analysis of flexible multibody systems has been proposed. In this formulation, a set of independent discrete deformation modes are defined for each element which are related to conventional small deflection beam theory in a co-ro
Energy Technology Data Exchange (ETDEWEB)
Kulak, R. F.; Fiala, C.
1980-03-01
This report presents the formulations used in the NEPTUNE code. Specifically, it describes the finite-element formulation of a three-dimensional hexahedral element for simulating the behavior of either fluid or solid continua. Since the newly developed hexahedral element and the original triangular plate element are finite elements, they are compatible in the sense that they can be combined arbitrarily to simulate complex reactor components in three-dimensional space. Because rate-type constitutive relations are used in conjunction with a velocity-strain tensor, the formulation is applicable to large deformation problems. This development can be used to simulate (1) the fluid adjacent to reactor components and (2) the concrete fill found in large reactor head closures.
Directory of Open Access Journals (Sweden)
M. Bauwens
2010-07-01
Full Text Available A long standing problem in paleoceanography concerns the reconstruction of water temperature from δ^{18}O carbonate, which for freshwater influenced environments is hindered because the isotopic composition of the ambient water (related to salinity affects the reconstructed temperature. In this paper we argue for the use of a nonlinear multi-proxy method called Weight Determination by Manifold Regularization to develop a temperature reconstruction model that is less sensitive to salinity variations. The motivation for using this type of model is twofold: Firstly, observed nonlinear relations between specific proxies and water temperature motivate the use of nonlinear models. Secondly, the use of multi-proxy models enables salinity related variations of a given temperature proxy to be explained by salinity-related information carried by a separate proxy. Our findings confirm that Mg/Ca is a powerful paleothermometer and highlight that reconstruction performance based on this proxy is improved significantly by combining its information with the information of other trace elements in multi-proxy models. Using Mg/Ca, Sr/Ca, Ba/Ca and Pb/Ca the WDMR model enabled a temperature reconstruction with a root mean squared error of ±2.19 °C for a salinity range between 15 and 32.
Kravtsova, Alexandra V; Milchakova, Nataliya A; Frontasyeva, Marina V
2015-08-15
Levels of Al, Sc, V, Co, Ni, As, Br, Rb, Sr, Ag, Sb, I, Cs, Ba, Th and U that were rarely or never studied, as well as the concentrations of classically investigated Mn, Fe and Zn in brown algae Cystoseira barbata C. Ag. and Cystoseira crinita (Desf.) Bory from the coastal waters of marine protected areas (Crimea, Black Sea), were determined using neutron activation analysis. Spatial variation and compartmentalization were studied for all 19 trace elements (TE). Concentrations of most TE were higher in "branches" than in "stems". Spatial variations of V, Co, Ni and Zn can be related to anthropogenic activities while Al, Sc, Fe, Rb, Cs, Th and U varied depending on chemical peculiarities of the coastal zone rocks. TE concentrations in C. crinita from marine protected areas near Tarkhankut peninsula and Cape Fiolent, identified as the most clean water areas, are submitted as the background concentrations. Copyright © 2015 Elsevier Ltd. All rights reserved.
Institute of Scientific and Technical Information of China (English)
高夫征
2005-01-01
A finite volume element predictor-correetor method for a class of nonlinear parabolic system of equations is presented and analyzed. Suboptimal L2 error estimate for the finite volume element predictor-corrector method is derived. A numerical experiment shows that the numerical results are consistent with theoretical analysis.
2012-06-09
these formulations employ some form of either the Euler-Bernoulli or Timoshenko beam theories and are mostly restricted to small strain analysis. The...and Kadioglu [1], wherein a Timoshenko beam element is de- veloped using mixed variational principles. In their work, the finite element model...method in their analysis of cylindrical helical rods (based on the Timoshenko beam hypotheses). Additional numerical formulations for viscoelastic beams
Numerical Simulation of a Thermal-Protection Element of a Promising Reusable Capsule-Type Lander
Prosuntsov, P. V.; Shulyakovskii, A. V.; Taraskin, N. Yu.
2017-01-01
An indestructible multilayer thermal-barrier coating is proposed for a promising reusable capsule-type lander. This coating is based on a porous carbon-ceramic material. The thermal state of the coating proposed was simulated mathematically for different types of its reinforcement and different values of the porosity and the heat-conductivity coefficient of the carbon-ceramic material. Results of a numerical simulation of the temperature state of an element of the multilayer thermal-barrier coating are presented. On the basis of these data, the thickness and the weight efficiency of the coating were estimated.
Wit, de A.J.; Akcay Perdahcioglu, D.; Brink, van den W.M.; Boer, de A.
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 fidelit
Wit, de A.J.; Akcay-Perdahcioglu, D.; Brink, van den W.M.; Boer, de A.
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 fidelit
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
Institute of Scientific and Technical Information of China (English)
DUAN Huoyuan; LIANG Guoping
2001-01-01
Following Part I., we study the stabilized finite element method for the incom pressible Navier-Stokes equations. It is shown that this new methodology is stable and has an optimal error estimates for all mesh Peclet number, allowing any combination of velocity and pressure interpolation.
Metzger, Mario; Seifert, Thomas
2013-09-01
In this paper, an unconditionally stable algorithm for the numerical integration and finite-element implementation of a class of pressure dependent plasticity models with nonlinear isotropic and kinematic hardening is presented. Existing algorithms are improved in the sense that the number of equations to be solved iteratively is significantly reduced. This is achieved by exploitation of the structure of Armstrong-Frederik-type kinematic hardening laws. The consistent material tangent is derived analytically and compared to the numerically computed tangent in order to validate the implementation. The performance of the new algorithm is compared to an existing one that does not consider the possibility of reducing the number of unknowns to be iterated. The algorithm is used to implement a time and temperature dependent cast iron plasticity model, which is based on the pressure dependent Gurson model, in the finite-element program ABAQUS. The implementation is applied to compute stresses and strains in a large-scale finite-element model of a three cylinder engine block. This computation proofs the applicability of the algorithm in industrial practice that is of interest in applied sciences.
Varga, Peter; Schwiedrzik, Jakob; Zysset, Philippe K; Fliri-Hofmann, Ladina; Widmer, Daniel; Gueorguiev, Boyko; Blauth, Michael; Windolf, Markus
2016-04-01
Osteoporotic proximal femur fractures are caused by low energy trauma, typically when falling on the hip from standing height. Finite element simulations, widely used to predict the fracture load of femora in fall, usually include neither mass-related inertial effects, nor the viscous part of bone׳s material behavior. The aim of this study was to elucidate if quasi-static non-linear homogenized finite element analyses can predict in vitro mechanical properties of proximal femora assessed in dynamic drop tower experiments. The case-specific numerical models of 13 femora predicted the strength (R(2)=0.84, SEE=540N, 16.2%), stiffness (R(2)=0.82, SEE=233N/mm, 18.0%) and fracture energy (R(2)=0.72, SEE=3.85J, 39.6%); and provided fair qualitative matches with the fracture patterns. The influence of material anisotropy was negligible for all predictions. These results suggest that quasi-static homogenized finite element analysis may be used to predict mechanical properties of proximal femora in the dynamic sideways fall situation.
Directory of Open Access Journals (Sweden)
M. Bauwens
2010-11-01
Full Text Available A long standing problem in paleoceanography concerns the reconstruction of water temperature from δ^{18}O carbonate. It is problematic in the case of freshwater influenced environments because the δ^{18}O isotopic composition of the ambient water (related to salinity needs to be known. In this paper we argue for the use of a nonlinear multi-proxy method called Weight Determination by Manifold Regularization (WDMR to develop a temperature reconstruction model that is less sensitive to salinity variations. The motivation for using this type of model is twofold: firstly, observed nonlinear relations between specific proxies and water temperature motivate the use of nonlinear models. Secondly, the use of multi-proxy models enables salinity related variations of a given temperature proxy to be explained by salinity-related information carried by a separate proxy. Our findings confirm that Mg/Ca is a powerful paleothermometer and highlight that reconstruction performance based on this proxy is improved significantly by combining its information with the information for other trace elements in multi-proxy models. Although the models presented here are black-box models that do not use any prior knowledge about the proxies, the comparison of model reconstruction performances based on different proxy combinations do yield useful information about proxy characteristics. Using Mg/Ca, Sr/Ca, Ba/Ca and Pb/Ca the WDMR model enables a temperature reconstruction with a root mean squared error of ± 2.19 °C for a salinity range between 15 and 32.
Institute of Scientific and Technical Information of China (English)
DING Hai; ZHU Zhen-nan; DAI Ke-rong; YE Ming; WANG Cheng-tao
2008-01-01
The mechanical properties of the pelvic trabecular bone have been studied at the continuum level. However, nothing is known about the tissue-level damage in the trabecular bone of the healthy human acetabulum at apparent small strains characteristic of habitual. By a DAWING 4000 A supercomputer, nonlinear micro-finite element (μFE) analysis was performed to quantify tissue-level damage accumulation in trabecular bone at small strains. The data indicate that damage in trabecular bone commence at 0.2% apparent strain. The findings imply that tissue yielding can initiate at very low strains in the trabecular bone of the healthy acetabulum and that this local failure has negative consequences on the apparent mechanical properties of trabecular bone.
Vivek, P.; Murugakoothan, P.
2014-12-01
Nonlinear optical bulk single crystal of Imidazole-imidazolium picrate monohydrate (IIP) has been grown by Sankaranarayanan-Ramasamy (SR) method using acetonitrile as solvent. First time we report the bulk growth of IIP crystal by SR method. The transparent IIP single crystal of maximum diameter 21 mm and length 46 mm was obtained by employing SR method. The grown crystal was subjected to high resolution X-ray diffraction, UV-vis-NIR transmittance, refractive index, hardness, dielectric and laser damage threshold studies. The crystalline perfection of the grown crystal was analyzed using HRXRD. Cut off wavelength and optical transmission window of the crystal was assessed by UV-vis-NIR and the refractive index of the crystal was found. The mechanical property of the crystal was estimated by Vicker's hardness test. The dielectric property of the crystal was measured as a function of frequency. The laser damage threshold value was determined. The particle size dependent second harmonic generation efficiency for IIP was evaluated with standard reference material potassium dihydrogen phosphate (KDP) by Kurtz-Perry powder method using Nd:YAG laser, which established the existence of phase matching. The second harmonic generation (SHG) of IIP crystal was investigated by the SHG Maker fringes technique. The mechanism of growth is revealed by carrying out chemical etching using acetonitrile as etchant.
Directory of Open Access Journals (Sweden)
Mohamed H.E. Monged
2016-07-01
Full Text Available Concentrations of K, Ca, U, Th, Cs, Sr, I, Al, Cd, Cu, Mn, Pb, Ni, Zn and Cr were determined in common foodstuffs consumed by adult inhabitants of Greater Cairo Area (GCA. Some of these elements have chemical and biological similarity to some of the radionuclides abundantly encountered during nuclear power production and therefore data on these elements could provide important information on their biokinetic behavior. A total of 120 samples were analyzed using Neutron Activation Analysis (NAA and Atomic Absorption Spectrometry (AAS. Highest contributions for the intake of micronutrients (Cu, Mn, Ni and Zn arise from broad bean, rice and wheat flour consumption. Meat, milk, eggs and some vegetables are the major sources of K, Ca, U, Th, Cs, Al, Cd and Pb intake. The medium daily intakes for the adult inhabitants of GCA from the analyzed elements were reported. The lower daily intake of Ca, Th, Cs and I by adult inhabitants of GCA could be due to significantly lower consumption of milk and milk products. The significantly lower intake of calcium by adult inhabitants of GCA may lead to higher uptake of radiostrontium and could result in perhaps higher internal radiation dose. The lower intake values obtained for thorium and uranium, which suggests that radiation dose from their ingestion at natural background levels, is likely to be lower than what may be concluded from International Commission on Radiological Protection (ICRP data. Concerning micronutrients, the recommended values of daily intake of Cu and Mn are conveniently supplied by diet; however, for Cr and Zn they are lower than the recommended daily allowance. Due to high metals concentrations and consumption rates, broad bean is the foodstuff that provided the highest ingestion rates of Cu, Mn, Ni and Zn, being therefore a very important source of micronutrients.
Directory of Open Access Journals (Sweden)
Mirić Filip
2012-01-01
Full Text Available The aging process is inevitable. It follows the individual from birth until death. Due to the inability of people to influence it, there is a greater obligation of society to provide the people in the „third age“ a dignified life, without any form of victimization. The author defines which people are considered old according to positive legal acts of the Republic of Serbia. The subject of this paper are the factors that increase the risk of victimization of the elderly within the family, taking into account the physical, psychological, sexual and economic violence against the elderly, as well as mechanisms for their legal protection from domestic violence, as one of the most effective tools of the state and society in general for protection of this particularly vulnerable social group. Relevant provisions of the Criminal Code and the Code of Criminal Procedure of the Republic of Serbia with a critical analysis of the incrimination of offenses with elements of domestic violence where the victim is usually an old person will be analyzed. From the subject defined in this manner, stems the paper‘ s mainly descriptive goal of describing the phenomenon through the analysis of the major forms of violence to which the elderly within the family are exposed (physical, psychological, economic and sexual violence. The purpose of the paper is also to analyze the factors that increase the risk of victimization of the elderly and the mechanisms for their legal protection from domestic violence, point out the harm of this type of violence and thus contribute to combating this negative social phenomenon.
Shih, Tsan-Hsing; Liu, Nan-Suey
2009-01-01
Very large eddy simulation (VLES) of the nonreacting turbulent flow in a single-element lean direct injection (LDI) combustor has been successfully performed via the approach known as the partially resolved numerical simulation (PRNS/VLES) using a nonlinear subscale model. The grid is the same as the one used in a previous RANS simulation, which was considered as too coarse for a traditional LES simulation. In this study, we first carry out a steady RANS simulation to provide the initial flow field for the subsequent PRNS/VLES simulation. We have also carried out an unsteady RANS (URANS) simulation for the purpose of comparing its results with that of the PRNS/VLES simulation. In addition, these calculated results are compared with the experimental data. The present effort has demonstrated that the PRNS/VLES approach, while using a RANS type of grid, is able to reveal the dynamically important, unsteady large-scale turbulent structures occurring in the flow field of a single-element LDI combustor. The interactions of these coherent structures play a critical role in the dispersion of the fuel, hence, the mixing between the fuel and the oxidizer in a combustor.
Angela Mihai, L.
2013-03-01
Finite element simulations of different shear deformations in non-linear elasticity are presented. We pay particular attention to the Poynting effects in hyperelastic materials, complementing recent theoretical findings by showing these effects manifested by specific models. As the finite element method computes uniform deformations exactly, for simple shear deformation and pure shear stress, the Poynting effect is represented exactly, while for the generalised shear and simple torsion, where the deformation is non-uniform, the solution is approximated efficiently and guaranteed computational bounds on the magnitude of the Poynting effect are obtained. The numerical results further indicate that, for a given elastic material, the same sign effect occurs under different shearing mechanisms, showing the genericity of the Poynting effect under a variety of shearing loads. In order to derive numerical models that exhibit either the positive or the negative Poynting effect, the so-called generalised empirical inequalities, which are less restrictive than the usual empirical inequalities involving material parameters, are assumed. © 2012 Elsevier Ltd.
Energy Technology Data Exchange (ETDEWEB)
Whirley, R.G.; Engelmann, B.E.
1993-11-01
This report is the User Manual for the 1993 version of DYNA3D, and also serves as a User Guide. DYNA3D is a nonlinear, explicit, finite element code for analyzing the transient dynamic response of three-dimensional solids and structures. The code is fully vectorized and is available on several computer platforms. DYNA3D includes solid, shell, beam, and truss elements to allow maximum flexibility in modeling physical problems. Many material models are available to represent a wide range of material behavior, including elasticity, plasticity, composites, thermal effects, and rate dependence. In addition, DYNA3D has a sophisticated contact interface capability, including frictional sliding and single surface contact. Rigid materials provide added modeling flexibility. A material model driver with interactive graphics display is incorporated into DYNA3D to permit accurate modeling of complex material response based on experimental data. Along with the DYNA3D Example Problem Manual, this document provides the information necessary to apply DYNA3D to solve a wide range of engineering analysis problems.
Energy Technology Data Exchange (ETDEWEB)
Biffle, J.H.
1993-02-01
JAC3D is a three-dimensional finite element program designed to solve quasi-static nonlinear mechanics problems. A set of continuum equations describes the nonlinear mechanics involving large rotation and strain. A nonlinear conjugate gradient method is used to solve the equation. The method is implemented in a three-dimensional setting with various methods for accelerating convergence. Sliding interface logic is also implemented. An eight-node Lagrangian uniform strain element is used with hourglass stiffness to control the zero-energy modes. This report documents the elastic and isothermal elastic-plastic material model. Other material models, documented elsewhere, are also available. The program is vectorized for efficient performance on Cray computers. Sample problems described are the bending of a thin beam, the rotation of a unit cube, and the pressurization and thermal loading of a hollow sphere.
Energy Technology Data Exchange (ETDEWEB)
Biffle, J.H.; Blanford, M.L.
1994-05-01
JAC2D is a two-dimensional finite element program designed to solve quasi-static nonlinear mechanics problems. A set of continuum equations describes the nonlinear mechanics involving large rotation and strain. A nonlinear conjugate gradient method is used to solve the equations. The method is implemented in a two-dimensional setting with various methods for accelerating convergence. Sliding interface logic is also implemented. A four-node Lagrangian uniform strain element is used with hourglass stiffness to control the zero-energy modes. This report documents the elastic and isothermal elastic/plastic material model. Other material models, documented elsewhere, are also available. The program is vectorized for efficient performance on Cray computers. Sample problems described are the bending of a thin beam, the rotation of a unit cube, and the pressurization and thermal loading of a hollow sphere.
In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio
2012-12-01
The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.
Institute of Scientific and Technical Information of China (English)
哲曼
2001-01-01
The effect of numerical integration in finite element methods applied to a class of nonlinear parabolic equations is considered and some sufficient conditions on the quadrature scheme to ensure that the order of convergence is unaltered in the presence of numerical integration are given. Optimal L2 and H1 estimates for the error and its time derivative are established.
Institute of Scientific and Technical Information of China (English)
彭丽
2002-01-01
The finite element solution of two points boundary value problem for nonlinear ordinary differential equation is studied by using the collocation-Galerkin method.The Jacobi points are introduced to establish high orders of accuracy for the approximate solution.Numerical results are presented for a sample problem.
Protected Nuclear Fuel Element
Kittel, J. H.; Schumar, J. F.
1962-12-01
A stainless steel-clad actinide metal fuel rod for use in fast reactors is reported. In order to prevert cladding failures due to alloy formation between the actinide metal and the stainless steel, a mesh-like sleeve of expanded metal is interposed between them, the sleeve metal being of niobium, tantalum, molybdenum, tungsten, zirconium, or vanadium. Liquid alkali metal is added as a heat transfer agent. (AEC)
Directory of Open Access Journals (Sweden)
DUMITRACHE Petru
2011-11-01
Full Text Available The objective of this paper is the highlighting of the main aspects that be considered in parametric modelling of the ROPS/FOPS protective structures in order to study of their behaviour using finite element method. In first part of the paper are presented, briefly, the main reference documents governing the mechanical protection of the human operator of machinery and equipment construction. Also, is presented the scheme of the optimization process of protective structures using CAD and FEA platforms. Next, is presented a parametric analysis of the protective structures geometry, in order to determine the main geometric parameters that define the geometry of these structures. These geometrical parameters are used in a case study where the geometry for a protective structure was generated using a CAD platform. In final part of the article are to present conclusions.
Shkurenko, V. M.
1993-06-01
This paper presents the production scheme for heat- and erosion-protective carbon plastic materials for heat shield elements of solid-propellant nozzles. Attention is also given the method of manufacturing adhesive joint assemblies, and the production scheme is included.
硼-铝强化板的非线性屈曲有限元分析%Nonlinear buckling finite element analysis of stiffened B-Al plates
Institute of Scientific and Technical Information of China (English)
Ezgi GUNAY; Cevdet AYGUN; Yunus Onur YILDIZ
2014-01-01
通过有限元方法（FEA）分析强化复合板的非线性屈曲行为。该模型中硼-铝复合材料由硼基体和嵌入其中的不同形态的Al纤维组成。对片层结构的B-Al矩形板施加横向压缩应力，发现强化纤维对具有不同几何形状板材的屈曲行为有明显影响。建模中采用单向、具有矩形截面的强化纤维。结果表明：加载过程中存在一重要的载荷范围，临界屈曲模式在稳态和非稳态之间反复转变。确定由不同的纤维形态和板材高宽比组成的分叉失稳区域。通过 ANSYS 有限元计算，研究简支边界条件下强化板材的失稳模式，分别得到压应力(σx)与平面收缩(u)以及压应力(σx)与面外挠度(δ)的关系曲线。通过非线性分析，在C1、 C2、 C3和 C4四种形态的纤维中，嵌入C2纤维的板材获得最安全的临界屈服应力。结果表明，FEA非线性屈曲分析可以得到精确的结果。%Nonlinear buckling behavior of stiffened composite B-Al plates was analyzed by means of finite element analysis (FEA) method. In the method, the composite material was taken as B matrix into which Al fibers were embedded in different configurations. The laminated B-Al material in the form of rectangular plates was subjected to lateral compressive loading. It is observed that stiffeners have significant effect on the buckling behavior of plates under compressive loading and for various geometrical configurations. The stiffeners used in the modeling are one-sided and have rectangular cross-sections. It is found that there are physically important loading intervals and the critical buckling modes make transitions back and forth between stable and unstable states. Bifurcation buckling regions resulting from various configurations of fiber orientations and different plate aspect ratios are determined. The whole analysis is performed by using ANSYS finite element computations. Only the buckling patterns of stiffened
AUTHOR|(CDS)2067087
In one of its acceptation, the word quench is synonym of destruction. And this is even more consistent with reality in the case of the Large Hadron Collider dipole magnets, whose magnetic field and stored energy are unprecedented: the uncontrolled transition from the superconducting to the resistive state can be the origin of dramatic events. This is why the protection of magnets is so important, and why so many studies and investigations have been carried out on quench origin. The production, cold testing and installation of the 1232 arc dipole magnets is completed. They have fulfilled all the requirements and the operation reliability of these magnets has already been partially confirmed. From an academic standpoint, nevertheless, the anomalous mechanical behaviour, which was sometimes observed during power tests, has not yet been given a clear explanation. The work presented in this thesis aims at providing an instrument to better understand the reasons for such anomalies, by means of finite element modell...
Directory of Open Access Journals (Sweden)
Wessam M. Abdel-Wahab
2013-10-01
Full Text Available Many active ingredients extracted from herbal and medicinal plants are extensively studied for their beneficial effects. Antioxidant activity and free radical scavenging properties of thymoquinone (TQ have been reported. The present study evaluated the possible protective effects of TQ against the toxicity and oxidative stress of sodium fluoride (NaF in the liver of rats. Rats were divided into four groups, the first group served as the control group and was administered distilled water whereas the NaF group received NaF orally at a dose of 10 mg/kg for 4 weeks, TQ group was administered TQ orally at a dose of 10 mg/kg for 5 weeks, and the NaF-TQ group was first given TQ for 1 week and was secondly administered 10 mg/kg/day NaF in association with 10 mg/kg TQ for 4 weeks. Rats intoxicated with NaF showed a significant increase in lipid peroxidation whereas the level of reduced glutathione (GSH and the activity of superoxide dismutase (SOD, catalase (CAT, glutathione S-transferase (GST and glutathione peroxidase (GPx were reduced in hepatic tissues. The proper functioning of the liver was also disrupted as indicated by alterations in the measured liver function indices and biochemical parameters. TQ supplementation counteracted the NaF-induced hepatotoxicity probably due to its strong antioxidant activity. In conclusion, the results obtained clearly indicated the role of oxidative stress in the induction of NaF toxicity and suggested hepatoprotective effects of TQ against the toxicity of fluoride compounds.
Linear and Nonlinear Finite Elements.
1983-12-01
Sm (b) aON cipasofa mesh of b~ow elemears as.i (at 71Thoesi(dan (e)iw for 5. mod S... reqecive y. for emada2x2Gaess scheme (brken ink ) and a 3 x 3...8217:I :111d C i rr,,r ! (yr(Itt I’:V il jilt I JI! 1-11 . IL curves iFj. 101 are for a prcsstire that ill~;-. t1-1 Cequal st PS rum. p t,,t tlc cr it
Harvey, Derek
Le degivrage au moyen d'actuateurs piezoelectriques est considere comme une avenue prometteuse pour le developpement de systemes a faible consommation d'energie applicables aux helicopteres legers. Ce type de systeme excite des frequences de resonances d'une structure pour produire des deformations suffisantes pour rompre l'adherence de la glace. Par contre, la conception de tel systeme demeure generalement mal comprise. Ce projet de maitrise etudie l'utilisation de methodes numeriques pour assister la conception des systemes de protection contre le givre a base d'elements piezoelectriques. La methodologie retenue pour ce projet a ete de modeliser differentes structures simples et de simuler l'excitation harmonique des frequences de resonance au moyen d'actuateurs piezoelectriques. Le calcul des frequences de resonances ainsi que la simulation de leur excitation a ensuite ete validee a l'aide de montages experimentaux. La procedure a ete realisee pour une poutre en porte-a-faux et pour une plaque plane a l'aide du logiciel de calcul par elements finis, Abaqus. De plus, le modele de la plaque plane a ete utilise afin de realiser une etude parametrique portant sur le positionnement des actuateurs, l'effet de la rigidite ainsi que de l'epaisseur de la plaque. Finalement, la plaque plane a ete degivree en chambre climatique. Des cas de degivrage ont ete simules numeriquement afin d'etudier la possibilite d'utiliser un critere base sur la deformation pour predire le succes du systeme. La validation experimentale a confirme la capacite du logiciel a calculer precisement a la fois les frequences et les modes de resonance d'une structure et a simuler leur excitation par des actuateurs piezoelectriques. L'etude revele que la definition de l'amortissement dans le modele numerique est essentiel pour l'obtention de resultats precis. Les resultats de l'etude parametrique ont demontre l'importance de minimiser l'epaisseur et la rigidite afin de reduire la valeur des frequences
Nonlinear model based on finite element analysis of SRM%基于非线性模型的开关磁阻电机有限元分析
Institute of Scientific and Technical Information of China (English)
谢培培; 陈青
2011-01-01
Study the magnetic field of switched reluctance motor by the finite element method. For the structure of switched reluctance motor is double saliency structure, the nonlinear magnetic field of switched reluctance motor is serious. The software Ansoft can get the magnetization curve clan of different rotor position, further seek inductance and torque characteristic curve. We combined the nonlinear simulation with finite element method and drew the simulation waveform. The result of our experiment proves the feasibility of nonlinear simulation and the rationality of finite element analysis data.%本文旨在运用有限元分析法研究开关磁阻电机磁场。开关磁阻电机具有双凸结构特性,所以其磁场呈非线性。Ansoft软件可得到不同转子位置下的磁化曲线族、电感及转矩特性曲线,再将有限元分析与非线性仿真有机结合,得出仿真波形。仿真结果可证明非线性仿真的可行性及有限元分析所得数据的合理性。
Goldman, Benjamin D.; Dowell, Earl H.; Scott, Robert C.
2015-01-01
Conical shell theory and a supersonic potential flow aerodynamic theory are used to study the nonlinear pressure buckling and aeroelastic limit cycle behavior of the thermal protection system for NASA's Hypersonic Inflatable Aerodynamic Decelerator. The structural model of the thermal protection system consists of an orthotropic conical shell of the Donnell type, resting on several circumferential elastic supports. Classical Piston Theory is used initially for the aerodynamic pressure, but was found to be insufficient at low supersonic Mach numbers. Transform methods are applied to the convected wave equation for potential flow, and a time-dependent aerodynamic pressure correction factor is obtained. The Lagrangian of the shell system is formulated in terms of the generalized coordinates for all displacements and the Rayleigh-Ritz method is used to derive the governing differential-algebraic equations of motion. Aeroelastic limit cycle oscillations and buckling deformations are calculated in the time domain using a Runge-Kutta method in MATLAB. Three conical shell geometries were considered in the present analysis: a 3-meter diameter 70 deg. cone, a 3.7-meter 70 deg. cone, and a 6-meter diameter 70 deg. cone. The 6-meter configuration was loaded statically and the results were compared with an experimental load test of a 6-meter HIAD. Though agreement between theoretical and experimental strains was poor, the circumferential wrinkling phenomena observed during the experiments was captured by the theory and axial deformations were qualitatively similar in shape. With Piston Theory aerodynamics, the nonlinear flutter dynamic pressures of the 3-meter configuration were in agreement with the values calculated using linear theory, and the limit cycle amplitudes were generally on the order of the shell thickness. The effect of axial tension was studied for this configuration, and increasing tension was found to decrease the limit cycle amplitudes when the circumferential
Cemek, Mustafa; Yılmaz, Fatma; Büyükokuroğlu, Mehmet Emin; Büyükben, Ahmet; Aymelek, Fatih; Ayaz, Ahmet
2012-08-01
The liver is a vital organ, and its function is generally impaired by chemicals. Some natural compounds have a protective role against liver diseases such as royal jelly (RJ). To our knowledge, there are no data available on the effect of RJ therapy on the levels of bio-element metabolisms and antioxidant enzyme activities in the carbon tetrachloride (CCl(4))-induced liver damage. Therefore, in the present study, we have investigated the role of RJ therapy in the trace and major elements and antioxidant enzymes in CCl(4)-induced hepatotoxicity in rats. Antioxidant enzyme activities decreased in the CCl(4)-treated group more than they did in the sham and RJ-administered groups. Many bio-element levels were also reduced in only the CCl(4)-treated group. This showed that the depletion of trace elements was related to erythrocyte antioxidant enzyme activities. RJ administration clearly increased the trace and major element levels and antioxidant enzyme activities in RJ groups. RJ may be used as functional foods because of their naturally high antioxidant potential and rich element content.
Energy Technology Data Exchange (ETDEWEB)
Costas-Rodriguez, M.; Lavilla, I. [Departamento de Quimica Analitica y Alimentaria, Area de Quimica Analitica, Facultad de Quimica, Universidad de Vigo, As Lagoas-Marcosende s/n, 36310 Vigo (Spain); Bendicho, C., E-mail: bendicho@uvigo.es [Departamento de Quimica Analitica y Alimentaria, Area de Quimica Analitica, Facultad de Quimica, Universidad de Vigo, As Lagoas-Marcosende s/n, 36310 Vigo (Spain)
2010-04-07
Inductively coupled plasma-mass spectrometry (ICP-MS) in combination with different supervised chemometric approaches has been used to classify cultivated mussels in Galicia (Northwest of Spain) under the European Protected Designation of Origin (PDO). 158 mussel samples, collected in the five rias on the basis of the production, along with minor and trace elements, including high field strength elements (HFSEs) and rare earth elements (REEs), were used with this aim. The classification of samples was achieved according to their origin: Galician vs. other regions (from Tarragona, Spain, and Ethang de Thau, France) and between the Galician Rias. The ability of linear discriminant analysis (LDA), soft independent modelling of class analogy (SIMCA) and artificial neural network (ANN) to classify the samples was investigated. Correct assignations for Galician and non-Galician samples were obtained when LDA and SIMCA were used. ANNs were more effective when a classification according to the ria of origin was to be applied.
Institute of Scientific and Technical Information of China (English)
王在峰; 侯保荣; 孙虎元; 宋积文; 陈胜利; 张大勇
2015-01-01
To supply a cathodic protection system for steel plates used to protect old wharfs, and find out distributions of e-lectrical field in cathodic protection system of steel plates in complex conditions, an ideal model of cathodic protection system of steel palates is established.Finite element simulation instead of traditional experiential estimate is used in calculation for cathodic protection system of steel plates under different conditions.Distributions of electrical field in cathodic protection system of steel plates in different corrosion medias are given, as well as the distributions of electrical field between two influenced steel plates.%为了给老式靠船码头的护堤钢板添加阴极保护系统，为护堤钢板阴极保护设计提供依据，建立护堤钢板阴极保护体系的理想模型，用有限元仿真代替传统经验估算法对不同情况下护堤钢板的阴极保护体系进行模拟计算，找到护堤钢板在不同的腐蚀介质及钢板之间相互影响时的阴极保护电场的分布规律。
Problems and solutions for microprocessor protection of series compensated lines
Energy Technology Data Exchange (ETDEWEB)
Novosel, D. [ABB Transmission Technology Inst., Raleigh, NC (United States); Phadke, A. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Chemistry; Saha, M.M.; Lindahl, S. [ABB Atom AB, Vaesteraas (Sweden)
1997-12-31
Protection of systems with series compensated lines is considered to be one of the most difficult tasks for relay manufacturers and utility engineers. Protection and control of surrounding circuit elements, particularly transmission line protection, needs to be adapted to the variations introduced by these devices. Fixed series capacitors and thyristor controlled devices introduce harmonics and non-linearities which adversely impact the protection function. To take full advantage of the series capacitor installation in a utility network, it is necessary to explore the impact of series capacitors on protection and implement appropriate schemes. (author)
Institute of Scientific and Technical Information of China (English)
杜宁
2001-01-01
Mixed finite element method is used to treat a kind of second-order nonlinear hyperbolic equations with absorbing boundary conditions. explicit-intime procedures are formulated and analyzed. Optimal L2-in-space error estimates are derived.
Directory of Open Access Journals (Sweden)
Vladimir Yakov
2015-02-01
Full Text Available This article presents a procedure for evaluation of the temperature of the steel element in a fire situation. The gas temperature in the fire compartment is given by the three nominal curves: ISO834, Hydrocarbon and Outer curve. The simple calculation model described in 4.2 of EN 1993-1-2 [1] is used. The proposed solution is based on the tables containing data for the temperature of the steel elements which are calculated with the VBA macros in MS Excel
CISM Advanced School on Crashworthiness : Energy Management and Occupant Protection
2001-01-01
From the fundamentals of impact mechanics and biomechanics to modern analysis and design techniques in impact energy management and occupant protection this book provides an overview of the application of nonlinear finite elements, conceptual modeling and multibody procedures, impact biomechanics, injury mechanisms, occupant mathematical modeling, and human surrogates in crashworthiness.
HPEM protection on HF transmission lines
Directory of Open Access Journals (Sweden)
R. Krzikalla
2004-01-01
Full Text Available Traditional protection concepts against electromagnetic interferences are combinations of nonlinear elements like spark gaps, varistors or suppressor diodes. Due to parasitic capacitances and inductivities and the general behavior of the elements, a trade off has to be made between the frequency bandwidth and the energy absorption capability of the protection circuit. For high frequency applications with signal frequencies above about 500MHz a sufficient protection can not be given without changing the transmitted signals itself. Additionally this kind of protection concept is designed and optimized against transient interferences with rise times down to some nanoseconds, for example the LEMP, the NEMP or the ESD. Current researches focus on transient interferences with rise times in the picosecond range and pulse widths of a few nanoseconds, the so called ultra wideband (UWB pulses, combined with a significant voltage amplitude of some kilovolts. In this paper investigations on nonlinear protection elements and linear filters against line-coupled UWB pulses with high voltage amplitudes will be done with special focus on the protection of high frequency data-lines.
Penjkin Roman V.; Doroškina Ljudmila A.; Smirnov Aleksej N.
2013-01-01
Early blight of potato (the agent is imperfect fungus Alternaria alternata (Fr.) Keissl.) is a serious disease of potatoes under hot conditions. This disease is important in the regions of Eastern and Southern Europe, Asia and Africa. It is controlled with intensive application of fungicides commonly used against late blight. However, currently fungicides cause undesirable damage to humans and the environment. Elements of forecasting the early blight have been developed in order to mini...
Polyakov, M.; Odinokov, S.
2017-05-01
The report focuses on special printing industry, which is called secure printing, which uses printing techniques to prevent forgery or falsification of security documents. The report considered the possibility of establishing a spectral device for determining the authenticity of certain documents that are protected by machine-readable luminophor labels. The device works in two spectral ranges - visible and near infrared that allows to register Stokes and anti-Stokes spectral components of protective tags. The proposed device allows verification of the authenticity of security documents based on multiple criteria in different spectral ranges. It may be used at enterprises related to the production of security printing products, expert units of law enforcement bodies at check of authenticity of banknotes and other structures.
Energy Technology Data Exchange (ETDEWEB)
Pereira, R.; Noronha, R.T.T.; Mattos, U. [Ceramica Safran, Betim, MG (Brazil); Pandolfelli, Victor Carlos [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais
1995-12-31
The conditions that should be input in a Finite Element Analysis for a suitable characterization of refractory bricks used for Bottom Pouring of Steel were investigated. The stiffness and thermal conductivity of the outside brick media (silica sand) were considered for the development of the model (which included silica sand properties). The stress components (shear, tensile or compressive stress) responsible for the spalling of the refractory bricks were identified through a transient nonlinear analysis. The thermomechanical spalling of the bricks is caused due to an increase in the shear stress inside the brick, in agreement with the observations at Steel Plants along steel leaks. (author) 5 figs., 1 tab.
Will Nonlinear Backcalculation Help?
DEFF Research Database (Denmark)
Ullidtz, Per
2000-01-01
demonstrates, that treating the subgrade as a nonlinear elastic material, can result in more realistic moduli and a much better agreement between measured and calculated stresses and strains.The response of nonlinear elastic materials can be calculated using the Finite Element Method (FEM). A much simpler...... approach is to use the Method of Equivalent Thicknesses (MET), modified for a nonlinear subgrade. The paper includes an example where moduli backcalculated using FEM, linear elastic theory and MET are compared. Stresses and strains predicted by the three methods are also compared to measured values...
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Akihiro; Ohtori, Yasuki; Yabana, Shuichi; Hirata, Kazuta [Central Research Inst. of Electric Power Industry, Abiko, Chiba (Japan). Abiko Research Lab
1999-04-01
The purpose of this research is to develop the evaluation method for mechanical properties of laminated rubber bearings by nonlinear finite element method (FEM) considering the volumetric deformation of natural rubber material. Relationship between pressure and volumetric strain of the natural rubber is obtained from the volumetric tests and is introduced into user-subroutine of the FEM code (ABAQUS). Finite element analyses of natural rubber bearings (NRB) and the natural rubber bearing with lead plug (LRB) are carried out. The results may be summarized as follows; 1) Horizontal, vertical stiffness and effect of shear deformation on vertical stiffness of natural rubber bearings that have various shape are simulated with enough accuracy. 2) Horizontal and vertical stiffness of LRB are also simulated well. (author)
Kardaś, Tomasz M.; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr
2017-01-01
Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media. PMID:28225007
Kardaś, Tomasz M; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr
2017-02-22
Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.
Pearson, Ian T.; Mottram, J. Toby
2012-01-01
A new modelling methodology is presented that enables the stiffness of adhesively bonded single lap-joints to be included in the finite element analysis of whole vehicle bodies. This work was driven by the need to significantly reduce computing resources for vehicle analysis. To achieve this goal the adhesive bond line and adherends are modelled by a relatively ‘small’ number of shell elements to replace the usual solid element mesh for a reliable analysis. Previous work in Part 1 has provide...
Topology optimization of nonlinear optical devices
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard
2011-01-01
This paper considers the design of nonlinear photonic devices. The nonlinearity stems from a nonlinear material model with a permittivity that depends on the local time-averaged intensity of the electric field. A finite element model is developed for time-harmonic wave propagation and an incremen......This paper considers the design of nonlinear photonic devices. The nonlinearity stems from a nonlinear material model with a permittivity that depends on the local time-averaged intensity of the electric field. A finite element model is developed for time-harmonic wave propagation...
Savelyev, Yu.; Rudenko, A.; Robota, L.; Koval, E.; Savelyeva, O.; Markovskaya, L.; Veselov, V.
2009-01-01
Novel polyurethanes, polyamidourethanes and polyurethane foams of stable to biocorrosion were synthesized. The polymers possess fungicidal/fungistatic and bactericidal/bacteriostatic activity. After the biological tests with using of mold fungi and yeasts, polymers totally keep their main exploitation characteristics: for most of polymers coefficients of strength and elasticity keeping are equal of 100%. Most of them possess the fungicidal properties of zero balls, according to the State Standard. Life-firmness investigation of the most aggressive extremophiles: mold fungi Penicillium and Aspergillus on the polymer surfaces showed that for some samples it made up from 3 to 10 days. Some polymers possess both anti-micotic and anti-bacterial action. Based on investigation results a special technological scheme of assured human protection against microorganisms attack in specific condition of his existence are to be elaborated.
Nonlinear observer design for a nonlinear string/cable FEM model using contraction theory
DEFF Research Database (Denmark)
Turkyilmaz, Yilmaz; Jouffroy, Jerome; Egeland, Olav
Contraction theory is a recently developed nonlinear analysis tool which may be useful for solving a variety of nonlinear control problems. In this paper, using Contraction theory, a nonlinear observer is designed for a general nonlinear cable/string FEM (Finite Element Method) model. The cable...
Nonlinear observer design for a nonlinear string/cable FEM model using contraction theory
DEFF Research Database (Denmark)
Turkyilmaz, Yilmaz; Jouffroy, Jerome; Egeland, Olav
Contraction theory is a recently developed nonlinear analysis tool which may be useful for solving a variety of nonlinear control problems. In this paper, using Contraction theory, a nonlinear observer is designed for a general nonlinear cable/string FEM (Finite Element Method) model. The cable...
Institute of Scientific and Technical Information of China (English)
石东洋; 王乐乐
2012-01-01
A new mixed finite element scheme was established, by applying a Crouzeix-Raviart type non-conforming linear triangular finite element to the nonlinear Sobolev equations, which had the advantages of simple structure, BB condition to be satisfied automatically and so on. At the same time, the optimal error estimates of related variables were obtained directly by utilizing the special properties of the interpolation on the element, instead of the general Ritz projection which was the essential tool in the traditional finite element analysis.%将Crouzeix-Raviart型非协调线性三角形元应用于非线性Sobolev方程,建立了一种新的混合元格式,它具有构造简单且BB条件自动满足等优势.同时,在摆脱传统有限元分析中广义Ritz投影这一必不可少工具的情形下,直接利用单元上插值的特殊性质,得到了相关变量的最优误差估计.
Energy Technology Data Exchange (ETDEWEB)
Apps, John A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wilkin, Richard T. [US Environmental Protection Agency (EPA), Cincinnati, OH (United States)
2015-09-30
This report contains a series of tables summarizing the thermodynamic properties of aqueous carbonate complexes and solid carbonate phases of the following elements: arsenic (As), barium (Ba), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni) thallium (Tl), uranium (U) and zinc (Zn). Most of these elements are potentially hazardous as defined by extant primary drinking water standards of the United States Environmental Protection Agency (EPA). The remainder are not considered hazardous, but are either listed by EPA under secondary standards, or because they can adversely affect drinking water quality. Additional tables are included giving the thermodynamic properties for carbonates of the alkali metal and alkali earth elements, sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and strontium (Sr), because of their value in developing correlative models to estimate the thermodynamic properties of carbonate minerals for which no such data currently exist. The purpose in creating the tables in this report is to provide future investigators with a convenient source for selecting and tracing the sources of thermodynamic data of the above listed elements for use in modeling their geochemical behavior in “underground sources of drinking water” (USDW). The incentive for doing so lies with a heightened concern over the potential consequences of the proposed capture and storage of carbon dioxide (CO2) generated by fossil fuel fired power plants in deep subsurface reservoirs. If CO2 were to leak from such reservoirs, it could migrate upward and contaminate USDWs with undesirable, but undetermined, consequences to water quality. The EPA, Office of Research and Development, through an Interagency Agreement with the U.S. Department of Energy at the Lawrence Berkeley National Laboratory, funded the preparation of this report.
Nonlinear Ultrasonic Phased Array Imaging
Potter, J. N.; Croxford, A. J.; Wilcox, P. D.
2014-10-01
This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.
Nonlinear ultrasonic phased array imaging
Potter, J N; Croxford, A.J.; Wilcox, P. D.
2014-01-01
This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging t...
Nonlinear ultrasonic phased array imaging.
Potter, J N; Croxford, A J; Wilcox, P D
2014-10-03
This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.
几何非线性新梁柱单元及结构程序设计%A geometric nonlinear new beam-column element and structure program design
Institute of Scientific and Technical Information of China (English)
张俊峰; 王利娟; 郝际平; 李天
2011-01-01
基于更新拉格朗日构形的增量虚位移原理,在其势能项中引入了全部6个应力分量,采用可计人单元剪切变形影响的三次多项式插值函数,详细推导了考虑剪切变形及翘曲的空间梁一柱单元几何非线性切线刚度矩阵.根据面向对象的程序设计思想,将整个有限元域划分为8个基本类,在单元基类的基础上派生了新的单元类,采用C++语言编制了面向对象的空间钢结构分析程序.几何非线性算例分析结果表明,本文提出的理论分析方法和计算程序是正确的和高效的.%According to the increment virtual displacement principle based on the updated Lagrange configuration,the potential energy associated with all six stress components was taken into account. The cubic interpolation function which can be used to consider the shear deformation effects has been applied to derive the geometrical nonlinear stiffness matrix of the space beam-column element considering the shear deformation and warping effects. Based on the object-oriented design conception, the finite element analysis domain is divided into eight classes. A new class is derived from the base element class. Using C+ + language,the spatial steel frame advanced analysis program is complied. Numerical examples including both geometric and material nonlinearities are used to demonstrate the accuracy and efficiency of the proposed analytical method and computer program.
Yasrebi, Ali; Rivera, Janelle A; Krumm, Elizabeth A; Yang, Jennifer A; Roepke, Troy A
2017-02-01
17β-estradiol (E2) regulates central and peripheral mechanisms that control energy and glucose homeostasis predominantly through estrogen receptor α (ERα) acting via receptor binding to estrogen response elements (EREs). ERα signaling is also involved in mediating the effects of E2 on diet-induced obesity (DIO), although the roles of ERE-dependent and -independent ERα signaling in reducing the effects of DIO remain largely unknown. We hypothesize that ERE-dependent ERα signaling is necessary to ameliorate the effects of DIO. We addressed this question using ERα knockout (KO) and ERα knockin/knockout (KIKO) female mice, the latter expressing an ERα that lacks a functional ERE binding domain. Female mice were ovariectomized, fed a low-fat diet (LFD) or a high-fat diet (HFD), and orally dosed with vehicle or estradiol benzoate (EB) (300 μg/kg). After 9 weeks, body composition, glucose and insulin tolerance, peptide hormone and inflammatory cytokine levels, and hypothalamic arcuate nucleus and liver gene expression were assessed. EB reduced body weight and body fat in wild-type (WT) female mice, regardless of diet, and in HFD-fed KIKO female mice, in part by reducing energy intake and feeding efficiency. EB reduced fasting glucose levels in KIKO mice fed both diets but augmented glucose tolerance only in HFD-fed KIKO female mice. Plasma insulin and interleukin 6 were elevated in KIKO and KO female mice compared with LFD-fed WT female mice. Expression of arcuate neuropeptide and receptor genes and liver fatty acid biosynthesis genes was altered by HFD and by EB through ERE-dependent and -independent mechanisms. Therefore, ERE-independent signaling mechanisms in both the brain and peripheral organs mediate, in part, the effects of E2 during DIO. Copyright © 2017 by the Endocrine Society.
Directory of Open Access Journals (Sweden)
Penjkin Roman V.
2013-01-01
Full Text Available Early blight of potato (the agent is imperfect fungus Alternaria alternata (Fr. Keissl. is a serious disease of potatoes under hot conditions. This disease is important in the regions of Eastern and Southern Europe, Asia and Africa. It is controlled with intensive application of fungicides commonly used against late blight. However, currently fungicides cause undesirable damage to humans and the environment. Elements of forecasting the early blight have been developed in order to minimize the dosage of fungicides. Primary symptoms (chloroses and necroses and the potential of pathogen natural inoculum (determination of disease severity, indexes of formation of conidia and aggressiveness; as well as the current weather conditions were registered and determined in the potato signal plots (no treatments or artificial inoculation near main potato cropping. Seed tubers of main potato cropping were preliminary treated with plant growth regulator Circon and micro-fertilizer Siliplant produced by the Russian Company NEST-M. These preparations proved to be effective in acceleration process of potato growth and in delaying the early blight onset by 5-10 days. The same potato cultivar must be planted both in signaling plots and in the fields. Well-timed determination of primary symptoms and potential of pathogen inoculum allowed us to understand the damage that early blight can cause to potato natural inoculation, and hence to provide well-timed application of fungicides with optimum dosages in mixture with Circon or Silipant. This forecasting method can be helpful for the adequate management of early blight and decrease of the environmental damages.
Nonlinear Metamaterials for Holography
Almeida, Euclides; Prior, Yehiam
2015-01-01
A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multi-layer metamaterial holograms where by the nonlinear process of Third Harmonic Generation, a background free image is formed at a new frequency which is the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analyzed and prospects for future device applications are discussed.
Fredriksson, Rikard; Shin, Jaeho; Untaroiu, Costin D
2011-08-01
To study the potential of active, passive, and integrated (combined active and passive) safety systems in reducing pedestrian upper body loading in typical impact configurations. Finite element simulations using models of generic sedan car fronts and the Polar II pedestrian dummy were performed for 3 impact configurations at 2 impact speeds. Chest contact force, head injury criterion (HIC(15)), head angular acceleration, and the cumulative strain damage measure (CSDM(0.25)) were employed as injury parameters. Further, 3 countermeasures were modeled: an active autonomous braking system, a passive deployable countermeasure, and an integrated system combining the active and passive systems. The auto-brake system was modeled by reducing impact speed by 10 km/h (equivalent to ideal full braking over 0.3 s) and introducing a pitch of 1 degree and in-crash deceleration of 1 g. The deployable system consisted of a deployable hood, lifting 100 mm in the rear, and a lower windshield air bag. All 3 countermeasures showed benefit in a majority of impact configurations in terms of injury prevention. The auto-brake system reduced chest force in a majority of the configurations and decreased HIC(15), head angular acceleration, and CSDM in all configurations. Averaging all impact configurations, the auto-brake system showed reductions of injury predictors from 20 percent (chest force) to 82 percent (HIC). The passive deployable countermeasure reduced chest force and HIC(15) in a majority of configurations and head angular acceleration and CSDM in all configurations, although the CSDM decrease in 2 configurations was minimal. On average a reduction from 20 percent (CSDM) to 58 percent (HIC) was recorded in the passive deployable countermeasures. Finally, the integrated system evaluated in this study reduced all injury assessment parameters in all configurations compared to the reference situations. The average reductions achieved by the integrated system ranged from 56 percent
Multipolar nonlinear nanophotonics
Smirnova, Daria
2016-01-01
Nonlinear nanophotonics is a rapidly developing field with many useful applications for a design of nonlinear nanoantennas, light sources, nanolasers, sensors, and ultrafast miniature metadevices. A tight confinement of the local electromagnetic fields in resonant photonic nanostructures can boost nonlinear optical effects, thus offering versatile opportunities for subwavelength control of light. To achieve the desired functionalities, it is essential to gain flexible control over the near- and far-field properties of nanostructures. Thus, both modal and multipolar analyses are widely exploited for engineering nonlinear scattering from resonant nanoscale elements, in particular for enhancing the near-field interaction, tailoring the far-field multipolar interference, and optimization of the radiation directionality. Here, we review the recent advances in this recently emerged research field ranging from metallic structures exhibiting localized plasmonic resonances to hybrid metal-dielectric and all-dielectric...
Directory of Open Access Journals (Sweden)
Shakeeb Bin Hasan
2014-12-01
Full Text Available Contrary to traditional optical elements, plasmonic antennas made from nanostructured metals permit the localization of electromagnetic fields on length scales much smaller than the wavelength of light. This results in huge amplitudes for the electromagnetic field close to the antenna being conducive for the observation of nonlinear effects already at moderate pump powers. Thus, these antennas exhibit a promising potential to achieve optical frequency conversion and all-optical control of light at the nano-scale. This opens unprecedented opportunities for ultrafast nonlinear spectroscopy, sensing devices, on-chip optical frequency conversion, nonlinear optical metamaterials, and novel photon sources. Here, we review some of the recent advances in exploiting the potential of plasmonic antennas to realize robust nonlinear applications.
Nonlinear Stokes Mueller Polarimetry
Samim, Masood; Barzda, Virginijus
2015-01-01
The Stokes Mueller polarimetry is generalized to include nonlinear optical processes such as second- and third-harmonic generation, sum- and difference-frequency generations. The overall algebraic form of the polarimetry is preserved, where the incoming and outgoing radiations are represented by column vectors and the intervening medium is represented by a matrix. Expressions for the generalized nonlinear Stokes vector and the Mueller matrix are provided in terms of coherency and correlation matrices, expanded by higher-dimensional analogues of Pauli matrices. In all cases, the outgoing radiation is represented by the conventional $4\\times 1$ Stokes vector, while dimensions of the incoming radiation Stokes vector and Mueller matrix depend on the order of the process being examined. In addition, relation between nonlinear susceptibilities and the measured Mueller matrices are explicitly provided. Finally, the approach of combining linear and nonlinear optical elements is discussed within the context of polarim...
Nonlinearities in Microwave Superconductivity
Ledenyov, Dimitri O.; Ledenyov, Viktor O.
2012-01-01
The research is focused on the modeling of nonlinear properties of High Temperature Superconducting (HTS) thin films, using Bardeen, Cooper, Schrieffer and Lumped Element Circuit theories, with purpose to enhance microwave power handling capabilities of microwave filters and optimize design of microwave circuits in micro- and nano- electronics.
Institute of Scientific and Technical Information of China (English)
苏栋
2012-01-01
The p-y curve method is one of the most commonly used approaches in the analysis and design of piles under horizontal loadings. A p-y model is proposed within the framework of bounding surface elasto-plastic theory. In comparison with the traditional p-y curves, the model can simulate p-y relationships with different degrees of nonlinearity by choosing appropriate values for the model parameters, and can also simulate the soil-pile interaction under cyclic loadings. By adopting the incremental finite element method for beams on nonlinear foundation incorporating the proposed elasto-plastic p-y model, a finite element program is formulated. Soil-pile systems in the field or in the laboratory tests under monotonic or cyclic horizontal loadings are analyzed by use of the finite element program. By comparing the calculated and measured results, the capacity of the method and the proposed elasto-plastic p-y model in modeling the nonlinear response of the piles is demonstrated.%在水平受荷桩基的分析与计算中，P—Y曲线法是应用较为广泛的方法之一。在边界面弹塑性理论的框架内，建立了一个P—Y模型。与传统的P—Y曲线比较，该模型能通过不同的参数取值，模拟不同非线性特性的P—Y关系，并能模拟往复荷载作用下的桩土相互作用。同时采用非线性地基梁的增量有限元法，结合提出的弹塑性P—Y模型，编制了有限元分析程序，对单调和往复水平荷载作用下的桩土系统进行实例分析，结果表明该方法能有效的模拟水平荷载作用下的桩基非线性响应。
RESEARCH AND DEVELOPMENT OF THE SHEAR WALL NONLINEAR MACRO-ELEMENT%剪力墙非线性宏观单元的研究与单元开发
Institute of Scientific and Technical Information of China (English)
陈学伟; 韩小雷
2011-01-01
Since the elastoplastic damage occurs in the plastic stage of shear walls under a severe earthquake,the accurate modeling of the inelastic response of shear walls is primary to assess the aseismic safety and performance-based aseismic design. A structural elastoplastic analysis program MEASP which bases on macro elements is developed with object oriented language and the multiple-vertical-line-element model (MVLEM) is implemented in MESAP. The nonlinear macro element MVLEM is adopted to simulate the nonlinear behavior of shear walls designed according to Chinese code under a cyclic reverse loading test, and according to incorporating material constitutive relations as well as the uniaxial spring constitutive relation proposed by Fischinge. The hysteretic curve agrees well with the test, which indicates that the MVLEM is suitable to simulate the strong nonlinear behavior of shear walls accurately.%罕遇地震作用下剪力墙构件易进入塑性阶段而发生弹塑性损伤,准确地模拟剪力墙构件进入非线性状态后的力学行为对评价剪力墙结构的抗震安全性及基于性能的抗震设计具有重要的意义.通过面向对象语言编制了基于宏观单元的结构弹塑性分析软件平台MESAP及多竖向弹簧剪力墙单元(MVLEM),采用材料本构及Fischinger学者提出的轴向弹簧本构对按我国规范设计的剪力墙低周往复荷载试验进行分析,其滞回曲线吻合程度较高,表明该单元能够反映剪力墙构件的强非线性行为,且精度较高.
Bloembergen, Nicolaas
1996-01-01
Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe
Data Element Registry Services
U.S. Environmental Protection Agency — Data Element Registry Services (DERS) is a resource for information about value lists (aka code sets / pick lists), data dictionaries, data elements, and EPA data...
Institute of Scientific and Technical Information of China (English)
曾至立; 程黎明; 朱睿; 王建杰; 于研
2011-01-01
Objective To build an effective nonlinear three-dimensional finite-element (FE) model of T11 - L3 segments for a further biomechanical study of thoracolumbar spine. Methods The CT ( computed tomography) scan images of healthy adult T11 - L3 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 (GL) was modeled with 3-node shell element. All surrounding ligaments were represented by envelops 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 T11 - L3 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. Results In this study, a 3-demensional, 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
Energy Technology Data Exchange (ETDEWEB)
Geniet, F; Leon, J [Physique Mathematique et Theorique, CNRS-UMR 5825, 34095 Montpellier (France)
2003-05-07
A nonlinear system possessing a natural forbidden band gap can transmit energy of a signal with a frequency in the gap, as recently shown for a nonlinear chain of coupled pendulums (Geniet and Leon 2002 Phys. Rev. Lett. 89 134102). This process of nonlinear supratransmission, occurring at a threshold that is exactly predictable in many cases, is shown to have a simple experimental realization with a mechanical chain of pendulums coupled by a coil spring. It is then analysed in more detail. First we go to different (nonintegrable) systems which do sustain nonlinear supratransmission. Then a Josephson transmission line (a one-dimensional array of short Josephson junctions coupled through superconducting wires) is shown to also sustain nonlinear supratransmission, though being related to a different class of boundary conditions, and despite the presence of damping, finiteness, and discreteness. Finally, the mechanism at the origin of nonlinear supratransmission is found to be a nonlinear instability, and this is briefly discussed here.
Institute of Scientific and Technical Information of China (English)
杜丽惠; 黄丽清
2001-01-01
本文采用轴对称非线性有限元方法分析竖洞开挖与混凝土的衬砌施工过程中围岩的应力应变，计算中引入破坏接近度的概念以判定材料的非线性及其破坏问题，分析了围岩的软化及其破坏形态，并进行了实际竖洞的蠕变分析.%In this paper, the nonlinear axisymmetric finite element method is adopted to analyze the stree-strain of surrounding rock of vertical tunnel in the process of excavation and lining. The failure approach concept is introduced in the discrimination of the non-linearity and failure of the rock. The softening of the rock and the types of failure are simulated and the creeping of the tunnel is analyzed.
Nonlinear Phase Control and Anomalous Phase Matching in Plasmonic Metasurfaces
Almeida, Euclides; Prior, Yehiam
2015-01-01
Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute a particularly attractive set of materials. By means of modern nanolithographic fabrication techniques, flat, ultrathin optical elements may be constructed. However, in spite of their strong optical nonlinearities, plasmonic metasurfaces have so far been investigated mostly in the linear regime. Here we introduce full nonlinear phase control over plasmonic elements in metasurfaces. We show that for nonlinear interactions in a phase-gradient nonlinear metasurface a new anomalous nonlinear phase matching condition prevails, which is the nonlinear analog of the generalized Snell law demonstrated for linear metasurfaces. This phase matching condition is very different from the other known phase matching schemes. The subwavelength phase control of optical nonlinearities provides a foundation for the design of flat nonlinear optical elements based on metasurfaces. Our demonstrated flat nonlinear elements (i.e. lenses) act...
Institute of Scientific and Technical Information of China (English)
袁志林; 段梦兰; 陈祥余; 钟超; 王建国
2012-01-01
导管架平台桩基础的控制荷载主要为风荷载、波浪荷载、地震荷载等水平荷载,为研究水平荷载下导管架平台桩基础的承载特性,采用非线性有限元分析方法对水平荷载下桩-土之间的相互作用进行研究,提出了有效模拟桩基水平承载特性的有限元模型,分析了模型桩的刚度、直径、土质参数中水平土压力系数、剪胀角对桩基承载特性的影响及水平荷载下群桩承载特性,并将有限元计算结果与API规范及模型试验结果进行对比.研究结果表明,非线性有限元分析方法分析水平荷载下桩-土相互作用是可行的,计算结果可为导管架平台的桩基设计提供参考.%The control loads of jacket platform pile foundations are the wind load, wave load, seismic load and other lateral loads. A fundamental study of the soil response of piles subjected to lateral loads is conducted using the nonlinear finite element analysis. A finite element model is established to simulate the response of a pile subjected to lateral loads effectively. The effects of pile properties, i.e. stiffness and diameter and soil properties, i.e., coefficient of horizontal earth pressure, dilation angle on the response of a pile subjected to lateral loads are investigated. In addition, the response of pile groups under lateral loads is also analyzed. Finally, the results of finite element analysis are compared with API recommendations and the model test results. The results of the study show that the nonlinear finite element analysis is accurate in analyzing soil response of piles subjected to lateral loads. The calculation results can provide reference for the pile foundation design of jacket platform.
Institute of Scientific and Technical Information of China (English)
李永献; 杨晓侠
2016-01-01
研究了非协调类Carey元对非线性伪双曲方程的Galerkin逼近.利用该元在能量模意义下非协调误差比插值误差高一阶的特殊性质,线性三角形元的高精度分析结果,平均值技巧和插值后处理技术,在抛弃传统的Ritz投影的情形下,得到了半离散格式能量模意义下的超逼近性质和整体超收敛结果.同时,针对方程中系数为线性的情形建立一个具有二阶精度的全离散逼近格式,导出了相应的超逼近和超收敛结果.%The Galerkin finite element mothed for nonlinear pseudo-hyperbolic equations with nonconforming quasi-Carey element is studied.Based on the special property of the element(i.e.the consistency error is one order higher than its interpolation error in the energy norm) and high accuracy analysis result of the linear triangular element,the superclose property and global superconvergence result in energy norm with order O(h2) for semi-discrete scheme are obtained employing the mean-value technique and interpolated postprocessing approach.At the same time,a second order fully-discrete scheme is established for quasi-linear case.The corresponding superclose property and superconvergence result of order O(h2 +r2) are deduced.Here,h and r are parameters of subdivision in space and time step respectively.
Analysis of Nonlinear Electromagnetic Metamaterials
Poutrina, Ekaterina; Smith, David R
2010-01-01
We analyze the properties of a nonlinear metamaterial formed by integrating nonlinear components or materials into the capacitive regions of metamaterial elements. A straightforward homogenization procedure leads to general expressions for the nonlinear susceptibilities of the composite metamaterial medium. The expressions are convenient, as they enable inhomogeneous system of scattering elements to be described as a continuous medium using the standard notation of nonlinear optics. We illustrate the validity and accuracy of our theoretical framework by performing measurements on a fabricated metamaterial sample composed of an array of split ring resonators (SRRs) with packaged varactors embedded in the capacitive gaps in a manner similar to that of Wang et al. [Opt. Express 16, 16058 (2008)]. Because the SRRs exhibit a predominant magnetic response to electromagnetic fields, the varactor-loaded SRR composite can be described as a magnetic material with nonlinear terms in its effective magnetic susceptibility...
2014-01-01
valid OMB control number. 1. REPORT DATE 2014 2. REPORT TYPE 3. DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE A Polynomial-Based...solve Eq. (2.5) is kept under control by a sufficiently effective preconditioner. The RTB test case is an example of a dynamical scenario that can be run...program element 121670. We also would like to thank Michal Kopera and several anonymous reviewers for their helpful sug- gestions for improving the
Nonlinear systems in medicine.
Higgins, John P
2002-01-01
Many achievements in medicine have come from applying linear theory to problems. Most current methods of data analysis use linear models, which are based on proportionality between two variables and/or relationships described by linear differential equations. However, nonlinear behavior commonly occurs within human systems due to their complex dynamic nature; this cannot be described adequately by linear models. Nonlinear thinking has grown among physiologists and physicians over the past century, and non-linear system theories are beginning to be applied to assist in interpreting, explaining, and predicting biological phenomena. Chaos theory describes elements manifesting behavior that is extremely sensitive to initial conditions, does not repeat itself and yet is deterministic. Complexity theory goes one step beyond chaos and is attempting to explain complex behavior that emerges within dynamic nonlinear systems. Nonlinear modeling still has not been able to explain all of the complexity present in human systems, and further models still need to be refined and developed. However, nonlinear modeling is helping to explain some system behaviors that linear systems cannot and thus will augment our understanding of the nature of complex dynamic systems within the human body in health and in disease states.
Tunable nonlinear graphene metasurfaces
Smirnova, Daria A; Kivshar, Yuri S; Khanikaev, Alexander B
2015-01-01
We introduce the concept of nonlinear graphene metasurfaces employing the controllable interaction between a graphene layer and a planar metamaterial. Such hybrid metasurfaces support two types of subradiant resonant modes, asymmetric modes of structured metamaterial elements ("metamolecules") and graphene plasmons exhibiting strong mutual coupling and avoided dispersion crossing. High tunability of graphene plasmons facilitates strong interaction between the subradiant modes, modifying the spectral position and lifetime of the associated Fano resonances. We demonstrate that strong resonant interaction, combined with the subwavelength localization of plasmons, leads to the enhanced nonlinear response and high efficiency of the second-harmonic generation.
2016-07-01
Advanced Research Projects Agency (DARPA) Dynamics-Enabled Frequency Sources (DEFYS) program is focused on the convergence of nonlinear dynamics and...Early work in this program has shown that nonlinear dynamics can provide performance advantages. However, the pathway from initial results to...dependent nonlinear stiffness observed in these devices. This work is ongoing, and will continue through the final period of this program . Reference 9
Nayfeh, Ali Hasan
1995-01-01
Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim
Yoshida, Zensho
2010-01-01
This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl
Nanda, Sudarsan
2013-01-01
"Nonlinear analysis" presents recent developments in calculus in Banach space, convex sets, convex functions, best approximation, fixed point theorems, nonlinear operators, variational inequality, complementary problem and semi-inner-product spaces. Nonlinear Analysis has become important and useful in the present days because many real world problems are nonlinear, nonconvex and nonsmooth in nature. Although basic concepts have been presented here but many results presented have not appeared in any book till now. The book could be used as a text for graduate students and also it will be useful for researchers working in this field.
Directory of Open Access Journals (Sweden)
Belyakov V.A.
2011-12-01
Full Text Available The object of research is frost-protected shallow foundations.The article focuses on a technique of solving the nonstationary and nonlinear problem of freezing/thawing of soil in a 2D target setting, using software based on the finite-element method. The COSMOS/M package from Structural Research & Analysis Corp. is used as an example. The article also mentions some peculiarities of data input, caused by the non-linearity and nonstationarity of the problem.
Igarashi, Kensuke; Kuwabara, Tomohiko
2014-03-01
Thermosipho globiformans (rod-shaped thermophilic fermenter) and Methanocaldococcus jannaschii (coccal hyperthermophilic hydrogenotrophic methanogen) established H2-mediated syntrophy at 68 °C, forming exopolysaccharide-based aggregates. Electron microscopy showed that the syntrophic partners connected to each other directly or via intercellular bridges made from flagella, which facilitated transfer of H2. Elemental sulfur (S(0)) interrupted syntrophy; polysulfides abiotically formed from S(0) intercepted electrons that were otherwise transferred to H(+) to produce H2, resulting in the generation of sulfide (sulfur respiration). However, Fe(III) oxides significantly reduced the interruption by S(0), accompanied by stiffening of Fe(II) sulfides produced by the reduction of Fe(III) oxides with the sulfur respiration-generated sulfide. Sea sand replacing Fe(III) oxides failed to generate stiffening or protect the syntrophy. Several experimental results indicated that the stiffening of Fe(II) sulfides shielded the liquid from S(0), resulting in methane production in the liquid. Field-emission scanning electron microscopy showed that the stiffened Fe(II) sulfides formed a network of spiny structures in which the microorganisms were buried. The individual fermenter rods likely produced Fe(II) sulfides on their surface and became local centers of a core of spiny structures, and the connection of these cores formed the network, which was macroscopically recognized as stiffening.
NONLINEAR FINITE ELEMENT ANALYSIS OF REINFORCED CONCRETE BEAMS IN FIRE%火灾下钢筋混凝土梁非线性有限元分析
Institute of Scientific and Technical Information of China (English)
廖艳芬; 漆雅庆; 马晓茜
2011-01-01
Through numerical simulation of the whole process of heat transfer and deformation on three different conditions groups of reinfored concrete beams,it is analysed the non-linear changing process of the temperature distribution and structural deformation of reinfored concrete beams in fire.Based on thermal characteristics and the temperature-strain-stress constitutive characteristics of reinforced concrete beams it is analysied the influences of the evolutionary processes of the reinfored concrete beams temperature distribution in fire,as well as reinforcement ratio,initial load and heating time on the fire resistance capacity of reinfored concrete beams.Results show that the overall instability of the beams is caused by the reduction of material strength,weight and the initial load,as well as the internal stress because of the uneven heating in fire.The influences of initial load on the residual bearing capacity is little,but increase the number of rebars can effectively improve the fire resistance capacity of reinforced concrete beams.%为分析钢筋混凝土梁在火灾过程中的温度分布、结构变形非线性变化过程,在三组不同条件下对火灾后钢筋混凝土梁构件内部传热及变形过程进行全过程仿真。基于钢筋混凝土热工特性、温度-应变-应力本构特性,分析钢筋混凝土梁在受火时的温度分布演化过程,以及配筋率、初始载荷和受火时间等参数对钢筋混凝土梁防火承载力的影响。结果表明：火灾中材料强度的降低,自重和初始载荷以及不均匀升温引起的内部应力共同作用引起了构件的整体失稳。初始载荷对梁剩余承载力的影响不大,提高混凝土中钢筋数量能有效地提高钢筋混凝土梁的防火承载力。
Nonlinear Analysis of Buckling
Directory of Open Access Journals (Sweden)
Psotný Martin
2014-06-01
Full Text Available The stability analysis of slender web loaded in compression was presented. To solve this problem, a specialized computer program based on FEM was created. The nonlinear finite element method equations were derived from the variational principle of minimum of potential energy. To obtain the nonlinear equilibrium paths, the Newton-Raphson iteration algorithm was used. Corresponding levels of the total potential energy were defined. The peculiarities of the effects of the initial imperfections were investigated. Special attention was focused on the influence of imperfections on the post-critical buckling mode. The stable and unstable paths of the nonlinear solution were separated. Obtained results were compared with those gained using ANSYS system.
Nonlinear phased array imaging
Croxford, Anthony J.; Cheng, Jingwei; Potter, Jack N.
2016-04-01
A technique is presented for imaging acoustic nonlinearity within a specimen using ultrasonic phased arrays. Acoustic nonlinearity is measured by evaluating the difference in energy of the transmission bandwidth within the diffuse field produced through different focusing modes. The two different modes being classical beam forming, where delays are applied to different element of a phased array to physically focus the energy at a single location (parallel firing) and focusing in post processing, whereby one element at a time is fired and a focused image produced in post processing (sequential firing). Although these two approaches are linearly equivalent the difference in physical displacement within the specimen leads to differences in nonlinear effects. These differences are localized to the areas where the amplitude is different, essentially confining the differences to the focal point. Direct measurement at the focal point are however difficult to make. In order to measure this the diffuse field is used. It is a statistical property of the diffuse field that it represents the total energy in the system. If the energy in the diffuse field for both the sequential and parallel firing case is measured then the difference between these, within the input signal bandwidth, is largely due to differences at the focal spot. This difference therefore gives a localized measurement of where energy is moving out of the transmission bandwidth due to nonlinear effects. This technique is used to image fatigue cracks and other damage types undetectable with conventional linear ultrasonic measurements.
Nonlinear metamaterials for holography
Almeida, Euclides; Bitton, Ora; Prior, Yehiam
2016-08-01
A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency--the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed.
Nonlinear metamaterials for holography
Almeida, Euclides; Bitton, Ora
2016-01-01
A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency—the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed. PMID:27545581
Indian Academy of Sciences (India)
Ramaswamy Jaganathan; Sudeshna Sinha
2005-03-01
Motivated by studies on -deformed physical systems related to quantum group structures, and by the elements of Tsallis statistical mechanics, the concept of -deformed nonlinear maps is introduced. As a specific example, a -deformation procedure is applied to the logistic map. Compared to the canonical logistic map, the resulting family of -logistic maps is shown to have a wider spectrum of interesting behaviours, including the co-existence of attractors – a phenomenon rare in one-dimensional maps.
Stochastic Nonlinear Aeroelasticity
2009-01-01
STOCHASTIC NONLINEAR AEROELASTICITY 5a. CONTRACT NUMBER In- house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 0601102 6. AUTHOR(S) Philip S...ABSTRACT This report documents the culmination of in- house work in the area of uncertainty quantification and probabilistic techniques for... coff U∞ cs ea lw cw Figure 6: Wing and store geometry (left), wing box structural model (middle), flutter distribution (right
Zhu, Hong-Ming; Pen, Ue-Li; Chen, Xuelei; Yu, Hao-Ran
2016-01-01
We present a direct approach to non-parametrically reconstruct the linear density field from an observed non-linear map. We solve for the unique displacement potential consistent with the non-linear density and positive definite coordinate transformation using a multigrid algorithm. We show that we recover the linear initial conditions up to $k\\sim 1\\ h/\\mathrm{Mpc}$ with minimal computational cost. This reconstruction approach generalizes the linear displacement theory to fully non-linear fields, potentially substantially expanding the BAO and RSD information content of dense large scale structure surveys, including for example SDSS main sample and 21cm intensity mapping.
Boyd, Robert W
2013-01-01
Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q
Bozek, Piotr; Janus, Jaroslaw; Taszakowski, Jaroslaw; Glowacka, Agnieszka
2016-10-01
Water erosion is one of the factors which have negative effect on soil productivity. It often leads to irreversible soil degradation, making soil worthless for agricultural activities. One way of preventing water erosion is making the direction of cultivation perpendicular to the direction of rainwater run-off. Matching the direction with the shape of parcels boundaries in small and extended ones is often possible only through changes in the configuration of property boundaries, which is possible only in the process of land consolidation. The article presents methodology of qualifying the areas for changes in boundaries configuration and cultivation direction in view of existing erosion risk. A computation process was suggested that uses, among others, LIDAR data to model the terrain shape precisely as well as cadastral data that defines the geometry of parcels and, resulting from it, the direction of cultivation and form of use. The suggested process includes also the information on the texture of soil upper horizons from soil agricultural maps. The RUSLE erosion model was applied and the computation process took place in ArcGIS environment with the use of dedicated algorithms suggested and implemented to solve the formulated problem. Computations were conducted for test area of several hundred hectares which was characterized by vast diversity of soil types and landforms. The results prove the usefulness of the suggested method as an element of systems that support decision-making processes used in the stage of determining objects chosen for the realization of consolidating processes (including local consolidation, which covers only chosen fragment of a village). They can also be used in the stage of completing detailed plans of parcels distribution in land consolidation process. The importance of the method is particularly seen in the analysis of areas where land fragmentation indices are unfavourable. Especially in these cases, without the reorganization of
Kotzka, Jorg; Knebel, Birgit; Haas, Jutta; Kremer, Lorena; Jacob, Sylvia; Hartwig, Sonja; Nitzgen, Ulrike; Muller-Wieland, Dirk
2012-01-01
The transcription factor sterol regulatory element binding protein (SREBP)-1a plays a pivotal role in lipid metabolism. Using the SREBP-1a expressing human hepatoma cell line HepG2 we have shown previously that human SREBP-1a is phosphorylated at serine 117 by ERK-mitogen-activated protein kinases (MAPK). Using a combination of cell biology and protein chemistry approach we show that SREBP-1a is also target of other MAPK-families, i.e. c-JUN N-terminal protein kinases (JNK) or p38 stress activated MAP kinases. Serine 117 is also the major phosphorylation site in SREBP-1a for JNK. In contrast to that the major phosphorylation sites of p38 MAPK family are serine 63 and threonine 426. Functional analyses reveal that phosphorylation of SREBP-1a does not alter protein/DNA interaction. The identified phosphorylation sites are specific for both kinase families also in cellular context. To provide direct evidence that phosphorylation of SREBP-1a is a regulatory principle of biological and clinical relevance, we generated transgenic mice expressing mature transcriptionally active N-terminal domain of human SREBP-1a variant lacking all identified phosphorylaton sites designed as alb-SREBP-1aΔP and wild type SREBP-1a designed as alb-SREBP-1a liver specific under control of the albumin promoter and a liver specific enhancer. In contrast to alb-SREBP-1a mice the phosphorylation-deficient mice develop no enlarged fatty livers under normocaloric conditions. Phenotypical examination reveales a massive accumulation of adipose tissue in alb-SREBP-1a but not in the phosphorylation deficient alb-SREBP-1aΔP mice. Moreover, preventing phosphorylation of SREBP-1a protects mice also from dyslipidemia. In conclusion, phosphorylation of SREBP-1a by ERK, JNK and p38 MAPK-families resembles a biological principle and plays a significant role, in vivo.
Directory of Open Access Journals (Sweden)
Jorg Kotzka
Full Text Available The transcription factor sterol regulatory element binding protein (SREBP-1a plays a pivotal role in lipid metabolism. Using the SREBP-1a expressing human hepatoma cell line HepG2 we have shown previously that human SREBP-1a is phosphorylated at serine 117 by ERK-mitogen-activated protein kinases (MAPK. Using a combination of cell biology and protein chemistry approach we show that SREBP-1a is also target of other MAPK-families, i.e. c-JUN N-terminal protein kinases (JNK or p38 stress activated MAP kinases. Serine 117 is also the major phosphorylation site in SREBP-1a for JNK. In contrast to that the major phosphorylation sites of p38 MAPK family are serine 63 and threonine 426. Functional analyses reveal that phosphorylation of SREBP-1a does not alter protein/DNA interaction. The identified phosphorylation sites are specific for both kinase families also in cellular context. To provide direct evidence that phosphorylation of SREBP-1a is a regulatory principle of biological and clinical relevance, we generated transgenic mice expressing mature transcriptionally active N-terminal domain of human SREBP-1a variant lacking all identified phosphorylaton sites designed as alb-SREBP-1aΔP and wild type SREBP-1a designed as alb-SREBP-1a liver specific under control of the albumin promoter and a liver specific enhancer. In contrast to alb-SREBP-1a mice the phosphorylation-deficient mice develop no enlarged fatty livers under normocaloric conditions. Phenotypical examination reveales a massive accumulation of adipose tissue in alb-SREBP-1a but not in the phosphorylation deficient alb-SREBP-1aΔP mice. Moreover, preventing phosphorylation of SREBP-1a protects mice also from dyslipidemia. In conclusion, phosphorylation of SREBP-1a by ERK, JNK and p38 MAPK-families resembles a biological principle and plays a significant role, in vivo.
Ruszczynski, Andrzej
2011-01-01
Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates t
Characterization of Non-Linearized Spacecraft Relative Motion using Nonlinear Normal Modes
2016-04-20
Non-Linearized Spacecraft Relative Motion using Nonlinear Normal Modes 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62601F...AFRL-RV-PS- AFRL-RV-PS- TR-2015-0182 TR-2015-0182 CHARACTERIZATION OF NON-LINEARIZED SPACECRAFT RELATIVE MOTION USING NONLINEAR NORMAL MODES Eric...STATEMENT. THOMAS LOVELL PAUL HAUSGEN, Ph.D. Program Manager Technical Advisor, Spacecraft Component Technology JOHN BEAUCHEMIN Chief Engineer
Predictive simulation of nonlinear ultrasonics
Shen, Yanfeng; Giurgiutiu, Victor
2012-04-01
Most of the nonlinear ultrasonic studies to date have been experimental, but few theoretical predictive studies exist, especially for Lamb wave ultrasonic. Compared with nonlinear bulk waves and Rayleigh waves, nonlinear Lamb waves for structural health monitoring become more challenging due to their multi-mode dispersive features. In this paper, predictive study of nonlinear Lamb waves is done with finite element simulation. A pitch-catch method is used to interrogate a plate with a "breathing crack" which opens and closes under tension and compression. Piezoelectric wafer active sensors (PWAS) used as transmitter and receiver are modeled with coupled field elements. The "breathing crack" is simulated via "element birth and death" technique. The ultrasonic waves generated by the transmitter PWAS propagate into the structure, interact with the "breathing crack", acquire nonlinear features, and are picked up by the receiver PWAS. The features of the wave packets at the receiver PWAS are studied and discussed. The received signal is processed with Fast Fourier Transform to show the higher harmonics nonlinear characteristics. A baseline free damage index is introduced to assess the presence and the severity of the crack. The paper finishes with summary, conclusions, and suggestions for future work.
Bathe, Klaus-Jürgen
2015-01-01
Finite element procedures are now an important and frequently indispensable part of engineering analyses and scientific investigations. This book focuses on finite element procedures that are very useful and are widely employed. Formulations for the linear and nonlinear analyses of solids and structures, fluids, and multiphysics problems are presented, appropriate finite elements are discussed, and solution techniques for the governing finite element equations are given. The book presents general, reliable, and effective procedures that are fundamental and can be expected to be in use for a long time. The given procedures form also the foundations of recent developments in the field.
Institute of Scientific and Technical Information of China (English)
王芬玲; 石东洋; 陈金环
2012-01-01
在半离散和全离散格式下讨论非线性抛物积分微分方程的类Wilson非协调有限元逼近.当问题的精确解u∈H3(Ω)/H4(Ω)时,利用该元的相容误差在能量模意义下可以达到O(h2 )/O(h3)比其插值误差高一阶和二阶的特殊性质,再结合协调部分的高精度分析及插值后处理技术,并借助于双线性插值代替传统有限元分析中不可缺少的Ritz-Volterra投影导出了半离散格式下的O(h2)阶超逼近和超收敛结果.同时分别得到了向后Euler全离散格式下的超逼近性和Crank-Nicolson全离散格式下的最优误差估计.%A nonconforming quasi-Wilson finite element approximation for nonlinear parabolic integro-differential equation is discussed under the semi-discrete and fully-discrete schemes. By use of the special property of the element,i. e. , the consistence error estimate in energy norm when the exact solution u of the problem belongs to H3(Ω)/ H4(Ω) can reach to O(h2)/O(h3), one/two order higher than the interpolation error, then combination it with the higher accuracy analysis of its conforming part and the interpolated postprocessing technique, the superclose and superconvergence results with order O(h2) are obtained for semi-discrete scheme through interpolation instead of the Ritz-Volterra projection which is an indispensable tool in traditional finite element analysis. The superclose property and the optimal error estimate for backward Euler and Crank-Nicolson fully-discrete schemes are derived , respectively.
Nonlinear airship aeroelasticity
Bessert, N.; Frederich, O.
2005-12-01
The aeroelastic derivatives for today's aircraft are calculated in the concept phase using a standard procedure. This scheme has to be extended for large airships, due to various nonlinearities in structural and aerodynamic behaviour. In general, the structural model of an airship is physically as well as geometrically nonlinear. The main sources of nonlinearity are large deformations and the nonlinear material behaviour of membranes. The aerodynamic solution is also included in the nonlinear problem, because the deformed airship influences the surrounding flow. Due to these nonlinearities, the aeroelastic problem for airships can only be solved by an iterative procedure. As one possibility, the coupled aerodynamic and structural dynamic problem was handled using linked standard solvers. On the structural side, the Finite-Element program package ABAQUS was extended with an interface to the aerodynamic solver VSAERO. VSAERO is based on the aerodynamic panel method using potential flow theory. The equilibrium of the internal structural and the external aerodynamic forces leads to the structural response and a trimmed flight state for the specified flight conditions (e.g. speed, altitude). The application of small perturbations around a trimmed state produces reaction forces and moments. These constraint forces are then transferred into translational and rotational acceleration fields by performing an inertia relief analysis of the disturbed structural model. The change between the trimmed flight state and the disturbed one yields the respective aeroelastic derivatives. By including the calculated derivatives in the linearised equation of motion system, it is possible to judge the stability and controllability of the investigated airship.
Meier-Augenstein, Wolfram; Kemp, Helen; Midwood, Andy
2013-04-01
Styrian Pumpkin Seed Oil is a premium single seed vegetable oil that is uniquely linked to the geographic region of Styria where it is grown and produced. In 1996, the strong regional ties of this typical Styrian speciality were recognised by the EU-Commission who declared "Styrian Pumpkin Seed Oil P.G.I." as a Protected Geographical Indication (article 5 VO(EWG) Nr. 2081/92). In 1998, more than 2,000 domestic pumpkin seed producers and 30 oil mills formed an association of Styrian pumpkin seed oil producers, which is now called the "Gemeinschaft Steirisches Kürbiskernöl g.g.A.". This producers' association was formed in order to protect the regionality and the high quality of Styrian Pumpkin Seed Oil P.G.I. Procedures implemented by this producers' association document every step in the process from pumpkin seeds to seed crushing in oil mills and finally bottling of Styrian Pumpkin Seed Oil P.G.I., keeping a contiguous record of all production steps including annual harvest amounts. This permits full traceability of every bottle of Styrian Pumpkin Seed Oil P.G.I from harvest to the finished, bottled products found on the shelf of delis and even supermarkets. Despite these efforts of the producers' association, there have been repeated claims of g.g.A. (P.G.I.) certified bottles of Styrian Pumpkin Seed Oil (PSO) having been analysed independently and shown to contain either mixtures of Styrian and non-Styrian PSO or no Styrian PSO at all. Since keeping records of annual harvest amounts of pumpkin seeds would make it very difficult for an "over-production" by mixing or substitution of alien PSO's to go unnoticed, we formed the hypothesis that the red-flagged bottles could have been counterfeits containing alien PSO with bottles sporting fake g.g.A. seals and fake serial numbers. An alternative hypothesis was that the chosen method of detection of allegedly misrepresented g.g.A. Styrian PSO resulted in a high number of false negatives thus incorrectly rejecting
Nonlinear and active RF metamaterial applications using embedded devices
Katko, Alexander R.; Hawkes, Allen M.; Cummer, Steven A.
Nonlinear metamaterials have received considerable attention in recent years. The inclusion of nonlinear and active effects in metamaterials expands the possibilities for engineering media with designer properties. We detail our recent efforts to create nonlinear and active metamaterials at RF with useful properties through the inclusion of embedded nonlinear or active elements. We demonstrate some of the possible applications of such nonlinear and active metamaterials experimentally, with properties including saturable absorption, phase conjugation, and power harvesting.
Energy Technology Data Exchange (ETDEWEB)
Turchetti, G. (Bologna Univ. (Italy). Dipt. di Fisica)
1989-01-01
Research in nonlinear dynamics is rapidly expanding and its range of applications is extending beyond the traditional areas of science where it was first developed. Indeed while linear analysis and modelling, which has been very successful in mathematical physics and engineering, has become a mature science, many elementary phenomena of intrinsic nonlinear nature were recently experimentally detected and investigated, suggesting new theoretical work. Complex systems, as turbulent fluids, were known to be governed by intrinsically nonlinear laws since a long time ago, but received purely phenomenological descriptions. The pioneering works of Boltzmann and Poincare, probably because of their intrinsic difficulty, did not have a revolutionary impact at their time; it is only very recently that their message is reaching a significant number of mathematicians and physicists. Certainly the development of computers and computer graphics played an important role in developing geometric intuition of complex phenomena through simple numerical experiments, while a new mathematical framework to understand them was being developed.
Institute of Scientific and Technical Information of China (English)
李国杰; 姬希娜; 匡海燕; 邓清闯
2011-01-01
针对某微机线路保护装置在某变电站运行一段时间后出现的遥信误报现象进行了分析,定位出现问题的保护元件——展宽元件.对问题展宽元件和修改后的展宽元件的程序逻辑进行了详细分析,找出问题发生的原因.介绍了windows平台下模拟保护模块功能测试的测试模型.在基于此模型开发的测试平台上,针对展宽元件进行软件测试.测试时用判定表法设计测试用例和运用对比测试法对问题进行验证.最后总结了保护模块测试方面的一些思路.%This paper analyses the misoperation of remote signaling in a certain microprocessor-based line protection equipment after running a period of time in one transformer substation, and locates the problematic element-extension element. This paper analyzes the program logic of the problematic element and the modified element in detail, and finds the cause of the problem. It also introduces the model of function test of protection module in windows. On the test platform which is developed according to the model above, we conduct software test on the extension element. In the testing phase, we use the decision table method to design the test case and use the contrast testing method to verify if the problem is solved. In the end, some ideas for protection modules testing is summarized.
Energy Technology Data Exchange (ETDEWEB)
Gellermann, Rainer [Nuclear Control and Consulting GmbH, Braunschweig (Germany)
2014-07-01
The international association for radiation protection (IRPA) adopted in May 2004 a Code of Ethics in order to allow their members to hold an adequate professional level of ethical line of action. Based on this code of ethics the professional body of radiation protection (Fachverband fuer Strahlenschutz) has developed its own ethical code and adopted in 2005.
Institute of Scientific and Technical Information of China (English)
熊春宇; 吴春梅; 王艳芹; 李欣欣
2012-01-01
For the nonlinear characteristics of switched reluctancemotorwith two protruding pole, this paper analyzed the entire filed of the switched reluctance motor with three dimensional finite element analyses by using three-dimensional modeling method. In three-dmi ension finite elementmethod, wholemodelingwas adopted and racetrack coilwas introduced while adding loads. The result indicates thatthree-dmi ension finite elementanalysis can reflectthemagnetic field ditribution ofmotorand getstate character curve to be ready fordeveloping control study ofswitched reluctancemotor. Magnetization curves, inductance and torque charactercan be connected with switched reluctance drive to validate the steady and dynamic performance ofmotor.%针对开关磁阻电机双凸极结构导致的磁场严重非线性,利用三维有限元分析法对开关磁阻电机的电磁场进行研究.在三维分析中,考虑了端部效应对电机电磁场分布的影响.采用整体建模的方法,并在施加载荷时引入跑道线圈这一概念.通过仿真表明,三维有限元分析能更好地反映电机实际的磁场分布,得出电机静态曲线,为电机的控制研究奠定了基础.将有限元分析所得磁化曲线及电感、转矩数据用于改进的开关磁阻电机调速系统的模型中,来验证电机的静态性能和动态性能.
Seider, Warren D.; Ungar, Lyle H.
1987-01-01
Describes a course in nonlinear mathematics courses offered at the University of Pennsylvania which provides an opportunity for students to examine the complex solution spaces that chemical engineers encounter. Topics include modeling many chemical processes, especially those involving reaction and diffusion, auto catalytic reactions, phase…
Hilbert complexes of nonlinear elasticity
Angoshtari, Arzhang; Yavari, Arash
2016-12-01
We introduce some Hilbert complexes involving second-order tensors on flat compact manifolds with boundary that describe the kinematics and the kinetics of motion in nonlinear elasticity. We then use the general framework of Hilbert complexes to write Hodge-type and Helmholtz-type orthogonal decompositions for second-order tensors. As some applications of these decompositions in nonlinear elasticity, we study the strain compatibility equations of linear and nonlinear elasticity in the presence of Dirichlet boundary conditions and the existence of stress functions on non-contractible bodies. As an application of these Hilbert complexes in computational mechanics, we briefly discuss the derivation of a new class of mixed finite element methods for nonlinear elasticity.
Nonlinear intravascular ultrasound contrast imaging
Goertz, David E.; Frijlink, Martijn E.; de Jong, N.; van der Steen, Antonius F.W.
2006-01-01
Nonlinear contrast agent imaging with intravascular ultrasound (IVUS) is investigated using a prototype IVUS system and an experimental small bubble contrast agent. The IVUS system employed a mechanically scanned single element transducer and was operated at a 20 MHz transmit frequency (F20) for
2015-01-01
From the Back Cover: The emphasis throughout the present volume is on the practical application of theoretical mathematical models helping to unravel the underlying mechanisms involved in processes from mathematical physics and biosciences. It has been conceived as a unique collection of abstract methods dealing especially with nonlinear partial differential equations (either stationary or evolutionary) that are applied to understand concrete processes involving some important applications re...
Directory of Open Access Journals (Sweden)
Latifi Mohammed
2012-04-01
Full Text Available Abstract Background Effective fixation of fracture requires careful selection of a suitable implant to provide stability and durability. Implant with a feature of locking plate (LP has been used widely for treating distal fractures in femur because of its favourable clinical outcome, but its potential in fixing proximal fractures in the subtrochancteric region has yet to be explored. Therefore, this comparative study was undertaken to demonstrate the merits of the LP implant in treating the subtrochancteric fracture by comparing its performance limits against those obtained with the more traditional implants; angle blade plate (ABP and dynamic condylar screw plate (DCSP. Materials and Methods Nine standard composite femurs were acquired, divided into three groups and fixed with LP (n = 3, ABP (n = 3 and DCSP (n = 3. The fracture was modeled by a 20 mm gap created at the subtrochanteric region to experimentally study the biomechanical response of each implant under both static and dynamic axial loading paradigms. To confirm the experimental findings and to understand the critical interactions at the boundaries, the synthetic femur/implant systems were numerically analyzed by constructing hierarchical finite element models with nonlinear hyperelastic properties. The predictions from the analyses were then compared against the experimental measurements to demonstrate the validity of each numeric model, and to characterize the internal load distribution in the femur and load bearing properties of each implant. Results The average measurements indicated that the constructs with ABP, DCPS and LP respectively had overall stiffness values of 70.9, 110.2 and 131.4 N/mm, and exhibited reversible deformations of 12.4, 4.9 and 4.1 mm when the applied dynamic load was 400 N and plastic deformations of 11.3, 2.4 and 1.4 mm when the load was 1000 N. The corresponding peak cyclic loads to failure were 1100, 1167 and 1600 N. The errors
Nonlinear structural analysis using integrated force method
Indian Academy of Sciences (India)
N R B Krishnam Raju; J Nagabhushanam
2000-08-01
Though the use of the integrated force method for linear investigations is well-recognised, no efforts were made to extend this method to nonlinear structural analysis. This paper presents the attempts to use this method for analysing nonlinear structures. General formulation of nonlinear structural analysis is given. Typically highly nonlinear bench-mark problems are considered. The characteristic matrices of the elements used in these problems are developed and later these structures are analysed. The results of the analysis are compared with the results of the displacement method. It has been demonstrated that the integrated force method is equally viable and efficient as compared to the displacement method.
Nonlinear optics quantum computing with circuit QED.
Adhikari, Prabin; Hafezi, Mohammad; Taylor, J M
2013-02-08
One approach to quantum information processing is to use photons as quantum bits and rely on linear optical elements for most operations. However, some optical nonlinearity is necessary to enable universal quantum computing. Here, we suggest a circuit-QED approach to nonlinear optics quantum computing in the microwave regime, including a deterministic two-photon phase gate. Our specific example uses a hybrid quantum system comprising a LC resonator coupled to a superconducting flux qubit to implement a nonlinear coupling. Compared to the self-Kerr nonlinearity, we find that our approach has improved tolerance to noise in the qubit while maintaining fast operation.
Wave equation with concentrated nonlinearities
Noja, Diego; Posilicano, Andrea
2004-01-01
In this paper we address the problem of wave dynamics in presence of concentrated nonlinearities. Given a vector field $V$ on an open subset of $\\CO^n$ and a discrete set $Y\\subset\\RE^3$ with $n$ elements, we define a nonlinear operator $\\Delta_{V,Y}$ on $L^2(\\RE^3)$ which coincides with the free Laplacian when restricted to regular functions vanishing at $Y$, and which reduces to the usual Laplacian with point interactions placed at $Y$ when $V$ is linear and is represented by an Hermitean m...
Institute of Scientific and Technical Information of China (English)
童晓阳; 王睿; 孙明蔚
2012-01-01
为了提高广域后备保护的准确性与容错性,提出了一种同时利用传统保护元件和相量测量单元（PMU）数据的广域后备保护算法。将实时获得的广域保护动作加权,得到综合判断值,然后采用高斯函数获得对应的故障概率。同时,根据统计数据,由正序电压幅值、线路两侧正序电流相角差,计算得到PMU数据对应的故障概率,再将两种故障概率加权综合。在理论上定量地分析了广域保护容错的极限位数。在IEEE 14节点系统上的多组案例实验结果表明,该算法对多个保护误动与拒动有较高的容错性,并且能够检测多重故障。%In order to improve the correctness and fault-tolerance of wide-area backup protection, a novel wide-area protection algorithm using traditional protection components and phasor measurement unit （PMU） data is proposed. Firstly, the online obtained protection components are weighed to get the comprehensive judgment value. Then a Gaussian function is used to get the fault probability. At the same time, using the amplitude of positive sequence voltage and phase angle difference of positive- sequence currents within a line, the probability from PMU is also obtained. These two probabilities are weighted comprehensive to find the fault component. The limit digit number of wide-area backup protection is analyzed theoretically. The simulation tests based on IEEE 14-bus system illustrate the effectiveness and high fault-tolerance capability of the algorithm with the mis-operation and refuse-operation of multiple protections, as well as the detection of multiple faults.
Nonlinearity of colloid systems oxyhydrate systems
Sucharev, Yuri I
2008-01-01
The present monograph is the first systematic study of the non-linear characteristic of gel oxy-hydrate systems involving d- and f- elements. These are the oxyhydrates of rare-earth elements and oxides - hydroxides of d- elements (zirconium, niobium, titanium, etc.) The non-linearity of these gel systems introduces fundamental peculiarities into their structure and, consequently, their properties. The polymer-conformational diversity of energetically congenial gel fragments, which continu-ously transform under the effect of, for instance, system dissipation heat, is central to the au-thor's hy
Ngim, Chunhan; Ngim, Allister Daquan
2013-12-01
The rules governing the use of metallic mercury, a toxic and hazardous chemical, is in most jurisdictions identical to widely accepted standards and practices for handling the same chemical in industry for the protection of humans and their work environment. There cannot be exceptions solely for the practitioner dentists and their patients. Any workplace must be safe for both workers and visitors. The latter being dental patients waiting in the dentist's work environment. We reviewed the literature for toxic health effects of elemental mercury upon humans and present information about the Minimata Convention convened by the United Nations Environment Programme. A study conducted among dentists in Singapore and their personal work environment almost 30 years ago contributed to the workplace standard for elemental mercury, which was reduced, and is still currently enforced as a global standard. We recommend that dentists, with a large alternative battery of restorative materials today, make selection of a restorative material a more seriously considered choice, and not to make use of amalgam without the proper use of personal protective equipment for themselves (members of the dental operating team) and their patients, (amalgam traps and judicious monitoring of their workplace air quality). Mercury is ubiquitous in our presence due to human activities; any reduction in the dentists' workplace contributes to a global reduction. © 2013 Published by Elsevier (Singapore) Pte Ltd.
Kalinowski, M W
2016-01-01
A method for solving a quasilinear nonelliptical equation of the second order is developed and we give classification and parametrization of simple elements of the equation.We find exact solutions of an equation for potential stationary flow of a compressible gas in a supersonic region as an example of the method.
Jorg Kotzka; Birgit Knebel; Jutta Haas; Lorena Kremer; Sylvia Jacob; Sonja Hartwig; Ulrike Nitzgen; Dirk Muller-Wieland
2012-01-01
The transcription factor sterol regulatory element binding protein (SREBP)-1a plays a pivotal role in lipid metabolism. Using the SREBP-1a expressing human hepatoma cell line HepG2 we have shown previously that human SREBP-1a is phosphorylated at serine 117 by ERK-mitogen-activated protein kinases (MAPK). Using a combination of cell biology and protein chemistry approach we show that SREBP-1a is also target of other MAPK-families, i.e. c-JUN N-terminal protein kinases (JNK) or p38 stress acti...
Rajasekar, Shanmuganathan
2016-01-01
This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...
Institute of Scientific and Technical Information of China (English)
1996-01-01
3.1 A Unified Nonlinear Feedback Functional Method for Study Both Control and Synchronization of Spatiotemporal Chaos Fang Jinqing Ali M. K. (Department of Physics, The University of Lethbridge,Lethbridge, Alberta T1K 3M4,Canada) Two fundamental questions dominate future chaos control theories.The first is the problem of controlling hyperchaos in higher dimensional systems.The second question has yet to be addressed:the problem of controlling spatiotemporal chaos in a spatiotemporal system.In recent years, control and synchronization of spatiotemporal chaos and hyperchaos have became a much more important and challenging subject. The reason for this is the control and synchronism of such behaviours have extensive and great potential of interdisciplinary applications, such as security communication, information processing, medicine and so on. However, this subject is not much known and remains an outstanding open.
Institute of Scientific and Technical Information of China (English)
张正旺; 李爱平; 刘雪梅; 谢楠
2013-01-01
视主轴-刀柄结合面的双面接触部为一个可以用系统状态变量描述的非线性单元,基于非参数化方法结合有限元分析技术对主轴-刀柄结合面的非线性动态特征参数进行了识别.在HyperMesh中建立主轴-刀柄系统的有限元分析模型,利用Radioss求解器对该模型进行非线性瞬态响应分析,得到结合面处位移、速度、加速度的瞬态响应,再根据牛顿第二运动定律推导得出结合面处非线性接触力的时间历程数据,基于最小二乘法采用切比雪夫多项式对样本数据进行回归分析,得到主轴-刀柄结合面之间非线性接触力的解析表达模型,并验证了该模型的正确性.%Based on nonparametric identification technique and finite element method,a nonlinear dynamic parameter identification method for spindle-holder interface is presented,in which the double contact parts between spindle and holder is considered as a nonlinear element descripting by system state variables.A finite element model of spindle holder system is constructed by HyperMesh,and its nonlinear transient response analysis is conducted using Radioss solver.With Newton's second law of motion,the time history data of nonlinear contact force of the interface are then deduced.Least square estimates with the Chebyshev polynomial basis are employed to approximate the sample data,and an analytic model of the nonlinear contact force of the interface is obtained.
Directory of Open Access Journals (Sweden)
L. Quarrie
2014-09-01
Full Text Available The lifetime of Diode-Pumped Alkali Lasers (DPALs is limited by damage initiated by reaction of the glass envelope of its gain medium with rubidium vapor. Rubidium is absorbed into the glass and the rubidium cations diffuse through the glass structure, breaking bridging Si-O bonds. A damage-resistant thin film was developed enhancing high-optical transmission at natural rubidium resonance input and output laser beam wavelengths of 780 nm and 795 nm, while protecting the optical windows of the gain cell in a DPAL. The methodology developed here can be readily modified for simulation of expected transmission performance at input pump and output laser wavelengths using different combination of thin film materials in a DPAL. High coupling efficiency of the light through the gas cell was accomplished by matching the air-glass and glass-gas interfaces at the appropriate wavelengths using a dielectric stack of high and low index of refraction materials selected to work at the laser energies and protected from the alkali metal vapor in the gain cell. Thin films as oxides of aluminum, zirconium, tantalum, and silicon were selected allowing the creation of Fabry-Perot optical filters on the optical windows achieving close to 100% laser transmission in a solid optic combination of window and highly reflective mirror. This approach allows for the development of a new whole solid optic laser.
Quarrie, L.
2014-09-01
The lifetime of Diode-Pumped Alkali Lasers (DPALs) is limited by damage initiated by reaction of the glass envelope of its gain medium with rubidium vapor. Rubidium is absorbed into the glass and the rubidium cations diffuse through the glass structure, breaking bridging Si-O bonds. A damage-resistant thin film was developed enhancing high-optical transmission at natural rubidium resonance input and output laser beam wavelengths of 780 nm and 795 nm, while protecting the optical windows of the gain cell in a DPAL. The methodology developed here can be readily modified for simulation of expected transmission performance at input pump and output laser wavelengths using different combination of thin film materials in a DPAL. High coupling efficiency of the light through the gas cell was accomplished by matching the air-glass and glass-gas interfaces at the appropriate wavelengths using a dielectric stack of high and low index of refraction materials selected to work at the laser energies and protected from the alkali metal vapor in the gain cell. Thin films as oxides of aluminum, zirconium, tantalum, and silicon were selected allowing the creation of Fabry-Perot optical filters on the optical windows achieving close to 100% laser transmission in a solid optic combination of window and highly reflective mirror. This approach allows for the development of a new whole solid optic laser.
Energy Technology Data Exchange (ETDEWEB)
Quarrie, L., E-mail: Lindsay.Quarrie@l-3com.com, E-mail: lindsay.o.quarrie@gmail.com [New Mexico Institute of Mining and Technology, Department of Materials Engineering, 801 LeRoy Place, Socorro, NM 87801 (United States); Air Force Research Laboratory, AFRL/RDLC Laser CoE, 3550 Aberdeen Avenue SE, Kirtland AFB, NM 87117-5776 (United States)
2014-09-15
The lifetime of Diode-Pumped Alkali Lasers (DPALs) is limited by damage initiated by reaction of the glass envelope of its gain medium with rubidium vapor. Rubidium is absorbed into the glass and the rubidium cations diffuse through the glass structure, breaking bridging Si-O bonds. A damage-resistant thin film was developed enhancing high-optical transmission at natural rubidium resonance input and output laser beam wavelengths of 780 nm and 795 nm, while protecting the optical windows of the gain cell in a DPAL. The methodology developed here can be readily modified for simulation of expected transmission performance at input pump and output laser wavelengths using different combination of thin film materials in a DPAL. High coupling efficiency of the light through the gas cell was accomplished by matching the air-glass and glass-gas interfaces at the appropriate wavelengths using a dielectric stack of high and low index of refraction materials selected to work at the laser energies and protected from the alkali metal vapor in the gain cell. Thin films as oxides of aluminum, zirconium, tantalum, and silicon were selected allowing the creation of Fabry-Perot optical filters on the optical windows achieving close to 100% laser transmission in a solid optic combination of window and highly reflective mirror. This approach allows for the development of a new whole solid optic laser.
Structural optimization for nonlinear dynamic response.
Dou, Suguang; Strachan, B Scott; Shaw, Steven W; Jensen, Jakob S
2015-09-28
Much is known about the nonlinear resonant response of mechanical systems, but methods for the systematic design of structures that optimize aspects of these responses have received little attention. Progress in this area is particularly important in the area of micro-systems, where nonlinear resonant behaviour is being used for a variety of applications in sensing and signal conditioning. In this work, we describe a computational method that provides a systematic means for manipulating and optimizing features of nonlinear resonant responses of mechanical structures that are described by a single vibrating mode, or by a pair of internally resonant modes. The approach combines techniques from nonlinear dynamics, computational mechanics and optimization, and it allows one to relate the geometric and material properties of structural elements to terms in the normal form for a given resonance condition, thereby providing a means for tailoring its nonlinear response. The method is applied to the fundamental nonlinear resonance of a clamped-clamped beam and to the coupled mode response of a frame structure, and the results show that one can modify essential normal form coefficients by an order of magnitude by relatively simple changes in the shape of these elements. We expect the proposed approach, and its extensions, to be useful for the design of systems used for fundamental studies of nonlinear behaviour as well as for the development of commercial devices that exploit nonlinear behaviour.
A Modal Model to Simulate Typical Structural Dynamic Nonlinearity
Energy Technology Data Exchange (ETDEWEB)
Pacini, Benjamin Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mayes, Randall L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Roettgen, Daniel R [Univ. of Wisconsin, Madison, WI (United States)
2015-10-01
Some initial investigations have been published which simulate nonlinear response with almost traditional modal models: instead of connecting the modal mass to ground through the traditional spring and damper, a nonlinear Iwan element was added. This assumes that the mode shapes do not change with amplitude and there are no interactions between modal degrees of freedom. This work expands on these previous studies. An impact experiment is performed on a structure which exhibits typical structural dynamic nonlinear response, i.e. weak frequency dependence and strong damping dependence on the amplitude of vibration. Use of low level modal test results in combination with high level impacts are processed using various combinations of modal filtering, the Hilbert Transform and band-pass filtering to develop response data that are then fit with various nonlinear elements to create a nonlinear pseudo-modal model. Simulations of forced response are compared with high level experimental data for various nonlinear element assumptions.
Nonlinearities in Behavioral Macroeconomics.
Gomes, Orlando
2017-07-01
This article undertakes a journey across the literature on behavioral macroeconomics, with attention concentrated on the nonlinearities that the behavioral approach typically suggests or implies. The emphasis is placed on thinking the macro economy as a living organism, composed of many interacting parts, each one having a will of its own, which is in sharp contrast with the mechanism of the orthodox view (well represented by the neoclassical or new Keynesian dynamic stochastic general equilibrium - DSGE - model). The paper advocates that a thorough understanding of individual behavior in collective contexts is the only possible avenue to further explore macroeconomic phenomena and the often observed 'anomalies' that the benchmark DSGE macro framework is unable to explain or justify. After a reflection on the role of behavioral traits as a fundamental component of a new way of thinking the economy, the article proceeds with a debate on some of the most relevant frameworks in the literature that somehow link macro behavior and nonlinearities; covered subjects include macro models with disequilibrium rules, agent-based models that highlight interaction and complexity, evolutionary switching frameworks, and inattention based decision problems. These subjects have, as a fundamental point in common, the use of behavioral elements to transform existing interpretations of the economic reality, making it more evident how irregular fluctuations emerge and unfold on the aggregate.
Nonlinear singular vectors and nonlinear singular values
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A novel concept of nonlinear singular vector and nonlinear singular value is introduced, which is a natural generalization of the classical linear singular vector and linear singular value to the nonlinear category. The optimization problem related to the determination of nonlinear singular vectors and singular values is formulated. The general idea of this approach is demonstrated by a simple two-dimensional quasigeostrophic model in the atmospheric and oceanic sciences. The advantage and its applications of the new method to the predictability, ensemble forecast and finite-time nonlinear instability are discussed. This paper makes a necessary preparation for further theoretical and numerical investigations.
Orczykowski, Tomasz; Tiukało, Andrzej
2016-03-01
Land use is considered as a non-structural, ecologically beneficial flood protection measure. Forest as one of the land use types has many useful applications which can be observed in detail on www.nwrm.eu website project. It is scientifically proved that afforestation influences flood events with high probability of occurrence. However, it is still to be argued how to measure land use impact on the hydrological response of watershed and how it should be measured in an efficient and quantifiable way. Having the tool for such an impact measurement, we can build efficient land management strategies. It is difficult to observe the impact of land use on flood events in the field.Therefore, one of the possible solutions is to observe this impact indirectly by means of hydrological rainfall-runoff models as a proxy for the reality. Such experiments were conducted in the past. Our study aims to work on the viability assessment, methodology and tools that allow to observe this impact with use of selected hydrological models and readily available data in Poland. Our first reaserch site is located within headwaters of the Kamienna river watershed. This watershed has been affected by ecological disaster, which resulted in loss of 65% of forest coverage. Our proposed methodology is to observe this transformation and its effect on the watershed response to heavy precipitation and therefore change in the flood risk.
Directory of Open Access Journals (Sweden)
Orczykowski Tomasz
2016-03-01
Full Text Available Land use is considered as a non-structural, ecologically beneficial flood protection measure. Forest as one of the land use types has many useful applications which can be observed in detail on www.nwrm.eu website project. It is scientifically proved that afforestation influences flood events with high probability of occurrence. However, it is still to be argued how to measure land use impact on the hydrological response of watershed and how it should be measured in an efficient and quantifiable way. Having the tool for such an impact measurement, we can build efficient land management strategies. It is difficult to observe the impact of land use on flood events in the field.Therefore, one of the possible solutions is to observe this impact indirectly by means of hydrological rainfall-runoff models as a proxy for the reality. Such experiments were conducted in the past. Our study aims to work on the viability assessment, methodology and tools that allow to observe this impact with use of selected hydrological models and readily available data in Poland. Our first reaserch site is located within headwaters of the Kamienna river watershed. This watershed has been affected by ecological disaster, which resulted in loss of 65% of forest coverage. Our proposed methodology is to observe this transformation and its effect on the watershed response to heavy precipitation and therefore change in the flood risk.
Directory of Open Access Journals (Sweden)
Jamil, Muhammad
2013-02-01
Full Text Available The exogenous application of plant derived smoke solution through seed pre treatment is consider to create tolerance in the plant against salinity, for this purpose different dilution of plant derived smoke solution as 1:5000 Buhania, 1:1000 Buhania, 1:1000 Cymbopogon, 1:500 Cymbopogon were used against 0 mM, 50, 100 and 150mM NaCl solution in the medium. The effect was observed on total proline accumulation, heavy metals uptake, photosynthetic pigments and protein polypeptide bands intensity in two rice varieties as Basmati 385 (B-385 and Shaheen Basmati (S. Basmati. Proline concentration increases while chlorophyll “a” chlorophyll “b” and carotene level decreases with increasing salinity. On other hand zinc concentration increases while cadmium and lead concentration decrease in the crop under saline conditions. Intensity of protein polypeptides bands decreases gradually with increasing salinity level but plants from the seeds soaked with smoke solution alleviate the drastic affect of salinity, and intensity of bands is quite good by comparing with non primed seeds. It is concluded that seed priming with plant derived smoke solution show beneficial effect on crop to protect them from salinity.
Nonlinear frequency conversion in fiber lasers
DEFF Research Database (Denmark)
Svane, Ask Sebastian
The concept of nonlinear frequency conversion entails generating light at new frequencies other than those of the source light. The emission wavelength of typical fiber laser systems, relying on rare-earth dopants, are constrained within specific bands of the infrared region. By exploiting...... nonlinear processes, light from these specific wavelength bands can be used to generate light at new frequencies otherwise not obtainable by rare-earth elements. This thesis describes work covering Raman fiber lasers (RFLs) and amplifiers for nonlinear frequency down-conversion, and also the method...
Advanced finite element technologies
Wriggers, Peter
2016-01-01
The book presents an overview of the state of research of advanced finite element technologies. Besides the mathematical analysis, the finite element development and their engineering applications are shown to the reader. The authors give a survey of the methods and technologies concerning efficiency, robustness and performance aspects. The book covers the topics of mathematical foundations for variational approaches and the mathematical understanding of the analytical requirements of modern finite element methods. Special attention is paid to finite deformations, adaptive strategies, incompressible, isotropic or anisotropic material behavior and the mathematical and numerical treatment of the well-known locking phenomenon. Beyond that new results for the introduced approaches are presented especially for challenging nonlinear problems.
National Research Council Canada - National Science Library
Carlos Andrés M Gaviria; Aydée Patricia Z Guerrero; Peter R Thomson
2013-01-01
... of the connections between elements. This model was updated for different coating materials using experimental results of lateral loads test conduced on full-scale prototypes for five different coating configurations...
DEFF Research Database (Denmark)
Hajeb, Parvaneh; Shakibazadeh, Shahram; Sloth, Jens Jørgen
2016-01-01
Food is considered the main source of toxic element (arsenic, cadmium, lead, and mercury) exposure to humans, and they can cause major public health effects. In this chapter, we discuss the most important sources for toxic element in food and the foodstuffs which are significant contributors...... to human exposure. The occurrence of each element in food classes from different regions is presented. Some of the current toxicological risk assessments on toxic elements, the human health effect of each toxic element, and their contents in the food legislations are presented. An overview of analytical...... techniques and challenges for determination of toxic elements in food is also given....
Theory and design of nonlinear metamaterials
Rose, Alec Daniel
If electronics are ever to be completely replaced by optics, a significant possibility in the wake of the fiber revolution, it is likely that nonlinear materials will play a central and enabling role. Indeed, nonlinear optics is the study of the mechanisms through which light can change the nature and properties of matter and, as a corollary, how one beam or color of light can manipulate another or even itself within such a material. However, of the many barriers preventing such a lofty goal, the narrow and limited range of properties supported by nonlinear materials, and natural materials in general, stands at the forefront. Many industries have turned instead to artificial and composite materials, with homogenizable metamaterials representing a recent extension of such composites into the electromagnetic domain. In particular, the inclusion of nonlinear elements has caused metamaterials research to spill over into the field of nonlinear optics. Through careful design of their constituent elements, nonlinear metamaterials are capable of supporting an unprecedented range of interactions, promising nonlinear devices of novel design and scale. In this context, I cast the basic properties of nonlinear metamaterials in the conventional formalism of nonlinear optics. Using alternately transfer matrices and coupled mode theory, I develop two complementary methods for characterizing and designing metamaterials with arbitrary nonlinear properties. Subsequently, I apply these methods in numerical studies of several canonical metamaterials, demonstrating enhanced electric and magnetic nonlinearities, as well as predicting the existence of nonlinear magnetoelectric and off-diagonal nonlinear tensors. I then introduce simultaneous design of the linear and nonlinear properties in the context of phase matching, outlining five different metamaterial phase matching methods, with special emphasis on the phase matching of counter propagating waves in mirrorless parametric amplifiers
LEE, C.-M.; GOVERDOVSKIY, V. N.
2002-01-01
The up-to-date level and a few of the prospects are considered in transport biomechanical vibration protection systems. An experimental estimation of the maximum capabilities of traditional vibration protecting mechanisms (VPMs) used in driver seats is given. Some of the points of synthesis and research for the adaptive VPMs, called mechanisms of elastic links with small stiffness (ELSS-mechanisms) are presented. They contain a novel object of control: non-linear elastic elements with variable torsion “negative” stiffness (TNS). These TNS-elements help to optimize VPMs according to certain criteria and give them invariant structural and functional properties. Some experimental results are presented, and they correspond well with theoretical predictions. An approach is demonstrated for grade of quality of vibration protection of the men-operators of land unsuspended machines and pilots of helicopters.
Entropy viscosity method for nonlinear conservation laws
Guermond, Jean-Luc
2011-05-01
A new class of high-order numerical methods for approximating nonlinear conservation laws is described (entropy viscosity method). The novelty is that a nonlinear viscosity based on the local size of an entropy production is added to the numerical discretization at hand. This new approach does not use any flux or slope limiters, applies to equations or systems supplemented with one or more entropy inequalities and does not depend on the mesh type and polynomial approximation. Various benchmark problems are solved with finite elements, spectral elements and Fourier series to illustrate the capability of the proposed method. © 2010 Elsevier Inc.
Design of a nonlinear torsional vibration absorber
Tahir, Ammaar Bin
larger than that in the latter. A nonlinear absorber design has been proposed comprising of thin beams as elastic elements. The geometric configuration of the proposed design has been shown to provide cubic stiffness nonlinearity in torsion. The values of design variables, namely the strength of nonlinearity alpha and torsional stiffness kalpha, were obtained by optimizing dimensions and material properties of the beams for a maximum vibration energy dissipation in the nonlinear absorber. A parametric study has also been conducted to analyze the effect of the magnitude of excitation provided to the system on the performance of a nonlinear absorber. It has been shown that the nonlinear absorber turns out to be more effective in terms of energy dissipation as compared to a linear absorber with an increase in the excitation level applied to the system.
Mitigation of Blast Effects on Aluminum Foam Protected Masonry Walls
Institute of Scientific and Technical Information of China (English)
SU Yu; WU Chengqing; GRIFFITH Mike
2008-01-01
Terrorist attacks using improvised explosive devices (lED) can result in unreinforced masonry (URM) wall collapse.Protecting URM wall from lED attack is very complicated.An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy.However,mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world.In this palaer,numerical models are used to simulate the performance of aluminum foam protected URM walls subjected to blast loads.A distinctive model,in which mortar and brick units of masonry are discritized individually,is used to model the performance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model.The aluminum foam is modelled by a nonlinear elastoplastic material model.The material models for masonry,aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads.Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.
NONLINEAR EXPECTATIONS AND NONLINEAR MARKOV CHAINS
Institute of Scientific and Technical Information of China (English)
PENG SHIGE
2005-01-01
This paper deals with nonlinear expectations. The author obtains a nonlinear generalization of the well-known Kolmogorov's consistent theorem and then use it to construct filtration-consistent nonlinear expectations via nonlinear Markov chains. Compared to the author's previous results, i.e., the theory of g-expectations introduced via BSDE on a probability space, the present framework is not based on a given probability measure. Many fully nonlinear and singular situations are covered. The induced topology is a natural generalization of Lp-norms and L∞-norm in linear situations.The author also obtains the existence and uniqueness result of BSDE under this new framework and develops a nonlinear type of von Neumann-Morgenstern representation theorem to utilities and present dynamic risk measures.
Energy Technology Data Exchange (ETDEWEB)
Nakamura, K.; Iidzima, K.
1983-03-30
An anode of a light metal is used in the element, along with an electrolyte which consists of an ether solvent and an ionogenic additive in the form of a salt of dithiocarbamic acid. The element has good discharge characteristics.
Methodology for nonlinear quantification of a flexible beam with a local, strong nonlinearity
Herrera, Christopher A.; McFarland, D. Michael; Bergman, Lawrence A.; Vakakis, Alexander F.
2017-02-01
This study presents a methodology for nonlinear quantification, i.e., the identification of the linear and nonlinear regimes and estimation of the degree of nonlinearity, for a cantilever beam with a local, strongly nonlinear stiffness element. The interesting feature of this system is that it behaves linearly in the limits of extreme values of the nonlinear stiffness. An Euler-Bernoulli cantilever beam with two nonlinear configurations is used to develop and demonstrate the methodology. One configuration considers a cubic spring attached at a distance from the beam root to achieve a smooth nonlinear effect. The other configuration considers a vibro-impact element that generates non-smooth effects. Both systems have the property that, in the limit of small and large values of a configuration parameter, the system is almost linear and can be modeled as such with negligible error. For the beam with a cubic spring attachment, the forcing amplitude is the varied parameter, while for the vibro-impact beam, this parameter is the clearance between the very stiff stops and the beam at static equilibrium. Proper orthogonal decomposition is employed to obtain an optimal orthogonal basis used to describe the nonlinear system dynamics for varying parameter values. The frequencies of the modes that compose the basis are then estimated using the Rayleigh quotient. The variations of these frequencies are studied to identify parameter values for which the system behaves approximately linearly and those for which the dynamical response is highly nonlinear. Moreover, a criterion based on the Betti-Maxwell reciprocity theorem is used to verify the existence of nonlinear behavior for the set of parameter values suggested by the described methodology. The developed methodology is general and applicable to discrete or continuous systems with smooth or nonsmooth nonlinearities.
A new, challenging benchmark for nonlinear system identification
Tiso, Paolo; Noël, Jean-Philippe
2017-02-01
The progress accomplished during the past decade in nonlinear system identification in structural dynamics is considerable. The objective of the present paper is to consolidate this progress by challenging the community through a new benchmark structure exhibiting complex nonlinear dynamics. The proposed structure consists of two offset cantilevered beams connected by a highly flexible element. For increasing forcing amplitudes, the system sequentially features linear behaviour, localised nonlinearity associated with the buckling of the connecting element, and distributed nonlinearity resulting from large elastic deformations across the structure. A finite element-based code with time integration capabilities is made available at https://sem.org/nonlinear-systems-imac-focus-group/. This code permits the numerical simulation of the benchmark dynamics in response to arbitrary excitation signals.
Finite element computational fluid mechanics
Baker, A. J.
1983-01-01
Finite element analysis as applied to the broad spectrum of computational fluid mechanics is analyzed. The finite element solution methodology is derived, developed, and applied directly to the differential equation systems governing classes of problems in fluid mechanics. The heat conduction equation is used to reveal the essence and elegance of finite element theory, including higher order accuracy and convergence. The algorithm is extended to the pervasive nonlinearity of the Navier-Stokes equations. A specific fluid mechanics problem class is analyzed with an even mix of theory and applications, including turbulence closure and the solution of turbulent flows.
Development of a Nonlinear Internal Wave Tactical Decision Aid
2016-06-07
of a Nonlinear Internal Wave Tactical Decision Aid 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER...Development of a Nonlinear Internal Wave Tactical Decision Aid Christopher R. Jackson Global Ocean Associates 6220 Jean Louise Way Alexandria...www.internalwaveatlas.com LONG-TERM GOALS The long term goal of the project is to develop a prediction methodology for the occurrence of nonlinear
Chaotic Dynamics and Application of LCR Oscillators Sharing Common Nonlinearity
Jeevarekha, A.; Paul Asir, M.; Philominathan, P.
2016-06-01
This paper addresses the problem of sharing common nonlinearity among nonautonomous and autonomous oscillators. By choosing a suitable common nonlinear element with the driving point characteristics capable of bringing out chaotic motion in a combined system, we obtain identical chaotic states. The dynamics of the coupled system is explored through numerical and experimental studies. Employing the concept of common nonlinearity, a simple chaotic communication system is modeled and its performance is verified through Multisim simulation.
Structural optimization for nonlinear dynamic response
DEFF Research Database (Denmark)
Dou, Suguang; Strachan, B. Scott; Shaw, Steven W.
2015-01-01
condition, thereby providing a means for tailoring its nonlinear response. The method is applied to the fundamental nonlinear resonance of a clamped–clamped beam and to the coupled mode response of a frame structure, and the results show that one can modify essential normal form coefficients by an order...... resonant behaviour is being used for a variety of applications in sensing and signal conditioning. In this work, we describe a computational method that provides a systematic means for manipulating and optimizing features of nonlinear resonant responses of mechanical structures that are described...... by a single vibrating mode, or by a pair of internally resonant modes. The approach combines techniques from nonlinear dynamics, computational mechanics and optimization, and it allows one to relate the geometric and material properties of structural elements to terms in the normal form for a given resonance...
Nonlinear amplitude dynamics in flagellar beating
Oriola, David; Casademunt, Jaume
2016-01-01
The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood. The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive crosslinkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves. Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme. Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity. This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models. The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatiotemporal dynamics of dynein populations and flagell...
Subwavelength nonlinear phase control and anomalous phase matching in plasmonic metasurfaces
Almeida, Euclides; Shalem, Guy; Prior, Yehiam
2016-01-01
Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute an attractive set of materials with a potential for replacing standard bulky optical elements. In recent years, increasing attention has been focused on their nonlinear optical properties, particularly in the context of second and third harmonic generation and beam steering by phase gratings. Here, we harness the full phase control enabled by subwavelength plasmonic elements to demonstrate a unique metasurface phase matching that is required for efficient nonlinear processes. We discuss the difference between scattering by a grating and by subwavelength phase-gradient elements. We show that for such interfaces an anomalous phase-matching condition prevails, which is the nonlinear analogue of the generalized Snell's law. The subwavelength phase control of optical nonlinearities paves the way for the design of ultrathin, flat nonlinear optical elements. We demonstrate nonlinear metasurface lenses, which act both as generators and as manipulators of the frequency-converted signal.
Key Elements of Protection for Military Textiles
2010-10-15
a ballistic vest system consisting of composite, high-strength para -aramid fi bers (Kevlar), and boron carbide ceramic plates wrap- ped in ultra...iridescence because they possess no physiological means to control the refl ected colors aside from changing the angle of the iridescent surface...armor plates, e.g. boron nitride, tungsten carbide, tungsten disulfi de, aluminum nitride, and so forth, coated or contained in high-mod- ulus organic
Planetary protection: Elements for cost minimization
Debus, Andre
2006-10-01
In line with the UN Outer Space Treaty (article IX of the Outer Space Treaty—London/Washington January 27, 1967) [United Nations Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (the “Outer Space Treaty”) referenced 610 UNTS 205—resolution 2222(XXI) of December 1966 [1
Chen, Xianfeng; Zeng, Heping; Guo, Qi; She, Weilong
2015-01-01
This book presents an overview of the state of the art of nonlinear optics from weak light nonlinear optics, ultrafast nonlinear optics to electro-optical theory and applications. Topics range from the fundamental studies of the interaction between matter and radiation to the development of devices, components, and systems of tremendous commercial interest for widespread applications in optical telecommunications, medicine, and biotechnology.
Distributed nonlinear optical response
DEFF Research Database (Denmark)
Nikolov, Nikola Ivanov
2005-01-01
The purpose of the research presented here is to investigate basic physical properties in nonlinear optical materials with delayed or nonlocal nonlinearity. Soliton propagation, spectral broadening and the influence of the nonlocality or delay of the nonlinearity are the main focusses in the work...
Noncommutative Nonlinear Supersymmetry
Nishino, H; Nishino, Hitoshi; Rajpoot, Subhash
2002-01-01
We present noncommutative nonlinear supersymmetric theories. The first example is a non-polynomial Akulov-Volkov-type lagrangian with noncommutative nonlinear global supersymmetry in arbitrary space-time dimensions. The second example is the generalization of this lagrangian to Dirac-Born-Infeld lagrangian with nonlinear supersymmetry realized in dimensions D=2,3,4 and 6 (mod 8).
Fiber Nonlinearities: A Tutorial
Institute of Scientific and Technical Information of China (English)
Govind P. Agrawal
2003-01-01
Fiber nonlinearities have long been regarded as being mostly harmful for fiber-optic communication systems. Over the last few years, however, the nonlinear effects are increasingly being used for practical telecommunications applications,the Raman amplification being only one of the recent examples. In this tutorial I review the vario us nonlinear effects occurring in optical fibers from both standpoints..
Fiber Nonlinearities: A Tutorial
Institute of Scientific and Technical Information of China (English)
Govind; P.; Agrawal
2003-01-01
Fiber nonlinearities have long been regarded as being mostly harmful for fiber-optic communication systems. Over the last few years, however, the nonlinear effects are increasingly being used for practical telecommunications applications, the Raman amplification being only one of the recent examples. In this tutorial I review the various nonlinear effects occurring in optical fibers from both standpoints..
Geometrically nonlinear behavior of piezoelectric laminated plates
Rabinovitch, Oded
2005-08-01
The geometrically nonlinear behavior of piezo-laminated plates actuated with isotropic or anisotropic piezoelectric layers is analytically investigated. The analytical model is derived using the variational principle of virtual work along with the lamination and plate theories, the von Karman large displacement and moderate rotation kinematic relations, and the anisotropic piezoelectric constitutive laws. A solution strategy that combines the approach of the method of lines, the advantages of the finite element concept, and the variational formulation is developed. This approach yields a set of nonlinear ordinary differential equations with nonlinear boundary conditions, which are solved using the multiple-shooting method. Convergence and verification of the model are examined through comparison with linear and nonlinear results of other approximation methods. The nonlinear response of two active plate structures is investigated numerically. The first plate is actuated in bending using monolithic piezoceramic layers and the second one is actuated in twist using macro-fiber composites. The results quantitatively reveal the complicated in-plane stress state associated with the piezoelectric actuation and the geometrically nonlinear coupling of the in-plane and out-of-plane responses of the plate. The influence of the nonlinear effects ranges from significant stiffening in certain combinations of electrical loads and boundary conditions to amplifications of the induced deflections in others. The paper closes with a summary and conclusions.
... EPA United States Environmental Protection Agency Search Search Radiation Protection Share Facebook Twitter Google+ Pinterest Contact Us Radiation Protection Document Library View and download EPA radiation ...
PBH tests for nonlinear systems
Kawano, Yu; Ohtsuka, Toshiyuki
2017-01-01
Recently, concepts of nonlinear eigenvalues and eigenvectors are introduced. In this paper, we establish connections between the nonlinear eigenvalues and nonlinear accessibility/observability. In particular, we provide a generalization of Popov- Belevitch-Hautus (PBH) test to nonlinear accessibilit
Nonlinear dynamics and complexity
Luo, Albert; Fu, Xilin
2014-01-01
This important collection presents recent advances in nonlinear dynamics including analytical solutions, chaos in Hamiltonian systems, time-delay, uncertainty, and bio-network dynamics. Nonlinear Dynamics and Complexity equips readers to appreciate this increasingly main-stream approach to understanding complex phenomena in nonlinear systems as they are examined in a broad array of disciplines. The book facilitates a better understanding of the mechanisms and phenomena in nonlinear dynamics and develops the corresponding mathematical theory to apply nonlinear design to practical engineering.
State-variable analysis of non-linear circuits with a desk computer
Cohen, E.
1981-01-01
State variable analysis was used to analyze the transient performance of non-linear circuits on a desk top computer. The non-linearities considered were not restricted to any circuit element. All that is required for analysis is the relationship defining each non-linearity be known in terms of points on a curve.
Energy Technology Data Exchange (ETDEWEB)
Nayfeh, A.H.; Burns, J.A.; Cliff, E.M.
1990-05-18
The report summarizes results of experimental and theoretical investigations into the nonlinear response and control of structural elements. Methods for the analysis and design of control procedures applicable to certain nonlinear distributed parameter systems were investigated. Analytical and computational techniques were developed for evaluating the nonlinear effects on control designs. Bench-type experiments were conducted for validating some of the theoretical results.
Optimization of nonlinear structural resonance using the incremental harmonic balance method
DEFF Research Database (Denmark)
Dou, Suguang; Jensen, Jakob Søndergaard
2015-01-01
We present an optimization procedure for tailoring the nonlinear structural resonant response with time-harmonic loads. A nonlinear finite element method is used for modeling beam structures with a geometric nonlinearity and the incremental harmonic balance method is applied for accurate nonlinea...
Vibration Analysis of Timoshenko Beams on a Nonlinear Elastic Foundation
Institute of Scientific and Technical Information of China (English)
MO Yihua; OU Li; ZHONG Hongzhi
2009-01-01
The vibrations of beams on a nonlinear elastic foundation were analyzed considering the effects of transverse shear deformation and the rotational inertia of beams. A weak form quadrature element method (QEM) is used for the vibration analysis. The fundamental frequencies of beams are presented for various slenderness ratios and nonlinear foundation parameters for both slender and short beams. The results for slender beams compare well with finite element results. The analysis shows that the transverse shear de-formation and the nonlinear foundation parameter significantly affect the fundamental frequency of the beams.
Light dynamics in nonlinear trimers ans twisted multicore fibers
Castro-Castro, Claudia; Srinivasan, Gowri; Aceves, Alejandro B; Kevrekidis, Panayotis G
2016-01-01
Novel photonic structures such as multi-core fibers and graphene based arrays present unique opportunities to manipulate and control the propagation of light. Here we discuss nonlinear dynamics for structures with a few (2 to 6) elements for which linear and nonlinear properties can be tuned. Specifically we show how nonlinearity, coupling, and parity-time PT symmetric gain/loss relate to existence, stability and in general, dynamical properties of nonlinear optical modes. The main emphasis of our presentation will be on systems with few degrees of freedom, most notably couplers, trimers and generalizations thereof to systems with 6 nodes.
Nonlinear Elliptic Differential Equations with Multivalued Nonlinearities
Indian Academy of Sciences (India)
Antonella Fiacca; Nikolaos Matzakos; Nikolaos S Papageorgiou; Raffaella Servadei
2001-11-01
In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities. First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is defined on all $\\mathbb{R}$. Assuming the existence of an upper and of a lower solution, we prove the existence of a solution between them. Also for a special version of the problem, we prove the existence of extremal solutions in the order interval formed by the upper and lower solutions. Then we drop the requirement that the monotone nonlinearity is defined on all of $\\mathbb{R}$. This case is important because it covers variational inequalities. Using the theory of operators of monotone type we show that the problem has a solution. Finally in the last part we consider an eigenvalue problem with a nonmonotone multivalued nonlinearity. Using the critical point theory for nonsmooth locally Lipschitz functionals we prove the existence of at least two nontrivial solutions (multiplicity theorem).
Model updating of nonlinear structures from measured FRFs
Canbaloğlu, Güvenç; Özgüven, H. Nevzat
2016-12-01
There are always certain discrepancies between modal and response data of a structure obtained from its mathematical model and experimentally measured ones. Therefore it is a general practice to update the theoretical model by using experimental measurements in order to have a more accurate model. Most of the model updating methods used in structural dynamics are for linear systems. However, in real life applications most of the structures have nonlinearities, which restrict us applying model updating techniques available for linear structures, unless they work in linear range. Well-established frequency response function (FRF) based model updating methods would easily be extended to a nonlinear system if the FRFs of the underlying linear system (linear FRFs) could be experimentally measured. When frictional type of nonlinearity co-exists with other types of nonlinearities, it is not possible to obtain linear FRFs experimentally by using low level forcing. In this study a method (named as Pseudo Receptance Difference (PRD) method) is presented to obtain linear FRFs of a nonlinear structure having multiple nonlinearities including friction type of nonlinearity. PRD method, calculates linear FRFs of a nonlinear structure by using FRFs measured at various forcing levels, and simultaneously identifies all nonlinearities in the system. Then, any model updating method can be used to update the linear part of the mathematical model. In this present work, PRD method is used to predict the linear FRFs from measured nonlinear FRFs, and the inverse eigensensitivity method is employed to update the linear finite element (FE) model of the nonlinear structure. The proposed method is validated with different case studies using nonlinear lumped single-degree of freedom system, as well as a continuous system. Finally, a real nonlinear T-beam test structure is used to show the application and the accuracy of the proposed method. The accuracy of the updated nonlinear model of the
Stability of dithered non-linear systems with backlash or hysteresis
Desoer, C. A.; Shahruz, S. M.
1986-01-01
A study is conducted of the effect of dither on the nonlinear element of a single-input single-outout feedback system. Nonlinearities are considered with memory (backlash, hysteresis), in the feedforward loop; a dither of a given amplitude is injected at the input of the nonlinearity. The nonlinearity is followed by a linear element with low-pass characteristic. The stability of the dithered system and an approximate equivalent system (in which the nonlinearity is a smooth function) are compared. Conditions on the input and on the dither frequency are obtained so that the approximate-system stability guarantees that of the given hysteretic system.
Utilizing nonlinearity of transistors for reconfigurable chaos computation
Ditto, William; Kia, Behnam
2014-03-01
A VLSI circuit design for chaos computing is presented that exploits the intrinsic nonlinearity of transistors to implement a novel approach for conventional and chaotic computing circuit design. In conventional digital circuit design and implementation, transistors are simply switched on or off. We argue that by using the full range of nonlinear dynamics of transistors, we can design and build more efficient computational elements and logic blocks. Furthermore, the nonlinearity of these transistor circuits can be used to program the logic block to implement different types of computational elements that can be reconfigured. Because the intrinsic nonlinear dynamics of the transistors are utilized the resulting circuits typically require fewer transistors compared to conventional digital circuits as we exploit the intrinsic nonlinearity of the transistors to realize computations. This work was done with support from ONR grant N00014-12-1-0026 and from an ONR STTR and First Pass Engineering.
Nonlinear frequency response analysis of structural vibrations
Weeger, Oliver; Wever, Utz; Simeon, Bernd
2014-12-01
In this paper we present a method for nonlinear frequency response analysis of mechanical vibrations of 3-dimensional solid structures. For computing nonlinear frequency response to periodic excitations, we employ the well-established harmonic balance method. A fundamental aspect for allowing a large-scale application of the method is model order reduction of the discretized equation of motion. Therefore we propose the utilization of a modal projection method enhanced with modal derivatives, providing second-order information. For an efficient spatial discretization of continuum mechanics nonlinear partial differential equations, including large deformations and hyperelastic material laws, we employ the concept of isogeometric analysis. Isogeometric finite element methods have already been shown to possess advantages over classical finite element discretizations in terms of higher accuracy of numerical approximations in the fields of linear vibration and static large deformation analysis. With several computational examples, we demonstrate the applicability and accuracy of the modal derivative reduction method for nonlinear static computations and vibration analysis. Thus, the presented method opens a promising perspective on application of nonlinear frequency analysis to large-scale industrial problems.
Locally optimum nonlinearities for DCT watermark detection.
Briassouli, Alexia; Strintzis, Michael G
2004-12-01
The issue of copyright protection of digital multimedia data has attracted a lot of attention during the last decade. An efficient copyright protection method that has been gaining popularity is watermarking, i.e., the embedding of a signature in a digital document that can be detected only by its rightful owner. Watermarks are usually blindly detected using correlating structures, which would be optimal in the case of Gaussian data. However, in the case of DCT-domain image watermarking, the data is more heavy-tailed and the correlator is clearly suboptimal. Nonlinear receivers have been shown to be particularly well suited for the detection of weak signals in heavy-tailed noise, as they are locally optimal. This motivates the use of the Gaussian-tailed zero-memory nonlinearity, as well as the locally optimal Cauchy nonlinearity for the detection of watermarks in DCT transformed images. We analyze the performance of these schemes theoretically and compare it to that of the traditionally used Gaussian correlator, but also to the recently proposed generalized Gaussian detector, which outperforms the correlator. The theoretical analysis and the actual performance of these systems is assessed through experiments, which verify the theoretical analysis and also justify the use of nonlinear structures for watermark detection. The performance of the correlator and the nonlinear detectors in the presence of quantization is also analyzed, using results from dither theory, and also verified experimentally.
Elsawy, Mahmoud M R
2016-01-01
Two distinct models are developed to investigate the transverse magnetic stationary solutions propagating in one-dimensional anisotropic nonlinear plasmonic structures made from a nonlinear metamaterial core of Kerr-type embedded between two semi-infinite metal claddings. The first model is semi-analytical, in which we assumed that the anisotropic nonlinearity depends only on the transverse component of the electric field and that the nonlinear refractive index modification is small compared to the linear one. This method allows us to derive analytically the field profiles and the nonlinear dispersion relations in terms of the Jacobi elliptical functions. The second model is fully numerical, it is based on the finite-element method in which all the components of the electric field are considered in the Kerr-type nonlinearity with no presumptions on the nonlinear refractive index change. Our finite-element based model is valid beyond weak nonlinearity regime and generalize the well-known single-component fixed...
Energy Technology Data Exchange (ETDEWEB)
Zuo, Peng; Fan, Zheng, E-mail: ZFAN@ntu.edu.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Zhou, Yu [Advanced Remanufacturing and Technology Center (ARTC), 3 Clean Tech Loop, CleanTech Two, Singapore 637143 (Singapore)
2016-07-15
Nonlinear guided waves have been investigated widely in simple geometries, such as plates, pipe and shells, where analytical solutions have been developed. This paper extends the application of nonlinear guided waves to waveguides with arbitrary cross sections. The criteria for the existence of nonlinear guided waves were summarized based on the finite deformation theory and nonlinear material properties. Numerical models were developed for the analysis of nonlinear guided waves in complex geometries, including nonlinear Semi-Analytical Finite Element (SAFE) method to identify internal resonant modes in complex waveguides, and Finite Element (FE) models to simulate the nonlinear wave propagation at resonant frequencies. Two examples, an aluminum plate and a steel rectangular bar, were studied using the proposed numerical model, demonstrating the existence of nonlinear guided waves in such structures and the energy transfer from primary to secondary modes.
Directory of Open Access Journals (Sweden)
Wei Khim Ng
2009-02-01
Full Text Available We construct nonlinear extensions of Dirac's relativistic electron equation that preserve its other desirable properties such as locality, separability, conservation of probability and Poincaré invariance. We determine the constraints that the nonlinear term must obey and classify the resultant non-polynomial nonlinearities in a double expansion in the degree of nonlinearity and number of derivatives. We give explicit examples of such nonlinear equations, studying their discrete symmetries and other properties. Motivated by some previously suggested applications we then consider nonlinear terms that simultaneously violate Lorentz covariance and again study various explicit examples. We contrast our equations and construction procedure with others in the literature and also show that our equations are not gauge equivalent to the linear Dirac equation. Finally we outline various physical applications for these equations.
Institute of Scientific and Technical Information of China (English)
李杨; 邱长军; 陈桂荣; 邹树梁; 李林生
2015-01-01
Because lead glass is one of the brittle materials,more fragile than common glass and has high specific density,a shock absorption device of lead glass in radiation protection cockpit was designed. And under 3 kinds of extreme cases which were violently bumping, emergency braking and slewing braking,the finite element analysis of windshield lead glass was proceeded by using ANSYS Workbench,and the equivalent stress and deformation dis-tribution of the lead glass were obtained. Results showed that all the indexes were within the allowance range of shock absorption design,made sure that it was safe and reliable to work for lead glass under those 3 kinds of extreme cases,and provided a basis for optimum design of shock absorption device and the selection of spring.%由于防辐射挖掘机视场铅玻璃是脆性材料，比普通玻璃易碎，且比重较大，本文设计了铅玻璃减震装置，并运用Ansys Workbench对铅玻璃在颠簸、行走刹车、回转制动的3种极限工况进行有限元分析，得到其等效应力、总变形。结果表明各指标均不超出减震设计的允许范围，保证了铅玻璃在这3种极限工况下作业的安全可靠性，为实际弹簧减震装置的优化设计及弹簧选型提供了依据。
2015-03-23
developed from the spectral finite element method (SFEM) in order to expand its high fidelity performance to study nonlinear wave propagation. Later...severe conditions. 15. SUBJECT TERMS Impact Response, Nonlinear Wave Propagation, Spectral Finite Element Method, Wavelets, Force Identification 16...subtitle with volume number and part number, if applicable. On classified documents, enter the title classification in parentheses. 5a. CONTRACT
Linear and Nonlinear Aspects of Rotordynamics
Day, W. B.
1983-01-01
Excessive vibrations of the liquid oxygen pump in the Space Shuttle's Main Engine have been recorded during hot firing ground testing. In order to determine mathematical explanations of this possibility, destructive phenomenon differential equations have been examined which describe the rotordynamics of the pump. Modeling the rotor as a random eigenvalue problem was considered. Analytical expressions were derived for the solution in the case of symmetric damping and stiffness. This enables one to determine accuracy estimates when testing numerical techniques to solve both asymmetric and nonlinear problems. Finally, the rotor model has had nonlinear elements incorporated to improve its simulation of the pump and to expand the corresponding mathematical theory.
An Improved Linear Tetrahedral Element for Plasticity
Energy Technology Data Exchange (ETDEWEB)
Puso, M
2005-04-25
A stabilized, nodally integrated linear tetrahedral is formulated and analyzed. It is well known that linear tetrahedral elements perform poorly in problems with plasticity, nearly incompressible materials, and acute bending. For a variety of reasons, linear tetrahedral elements are preferable to quadratic tetrahedral elements in most nonlinear problems. Whereas, mixed methods work well for linear hexahedral elements, they don't for linear tetrahedrals. On the other hand, automatic mesh generation is typically not feasible for building many 3D hexahedral meshes. A stabilized, nodally integrated linear tetrahedral is developed and shown to perform very well in problems with plasticity, nearly incompressible materials and acute bending. Furthermore, the formulation is analytically and numerically shown to be stable and optimally convergent. The element is demonstrated to perform well in several standard linear and nonlinear benchmarks.
Ionescu, Tudor C.; Scherpen, Jacquelien M. A.
We study the notion of cross Gramians for nonlinear gradient systems, using the characterization in terms of prolongation and gradient extension associated to the system. The cross Gramian is given for the variational system associated to the original nonlinear gradient system. We obtain linearization results that correspond to the notion of a cross Gramian for symmetric linear systems. Furthermore, first steps towards relations with the singular value functions of the nonlinear Hankel operator are studied and yield promising results.
Directory of Open Access Journals (Sweden)
W. L. Fouché
1983-03-01
Full Text Available In this article we discuss some aspects of nonlinear functional analysis. It included reviews of Banach’s contraction theorem, Schauder’s fixed point theorem, globalising techniques and applications of homotopy theory to nonlinear functional analysis. The author emphasises that fundamentally new ideas are required in order to achieve a better understanding of phenomena which contain both nonlinear and definite infinite dimensional features.
Nonlinear Electrodynamics and QED
2003-01-01
The limits of linear electrodynamics are reviewed, and possible directions of nonlinear extension are explored. The central theme is that the qualitative character of the empirical successes of quantum electrodynamics must be used as a guide for understanding the nature of the nonlinearity of electrodynamics at the subatomic level. Some established theories of nonlinear electrodynamics, namely, those of Mie, Born, and Infeld are presented in the language of the modern geometrical and topologi...
Kono, Mitsuo
2010-01-01
A nonlinearity is one of the most important notions in modern physics. A plasma is rich in nonlinearities and provides a variety of behaviors inherent to instabilities, coherent wave structures and turbulence. The book covers the basic concepts and mathematical methods, necessary to comprehend nonlinear problems widely encountered in contemporary plasmas, but also in other fields of physics and current research on self-organized structures and magnetized plasma turbulence. The analyses make use of strongly nonlinear models solved by analytical techniques backed by extensive simulations and available experiments. The text is written for senior undergraduates, graduate students, lecturers and researchers in laboratory, space and fusion plasmas.
Nonlinear magnetic metamaterials.
Shadrivov, Ilya V; Kozyrev, Alexander B; van der Weide, Daniel W; Kivshar, Yuri S
2008-12-08
We study experimentally nonlinear tunable magnetic metamaterials operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We demonstrate that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such metamaterial can demonstrate various nonlinear properties. In particular, we study experimentally the power-dependent shift of the transmission band and demonstrate nonlinearity-induced enhancement (or suppression) of wave transmission. (c) 2008 Optical Society of America
Organic nonlinear optical materials
Umegaki, S.
1987-01-01
Recently, it became clear that organic compounds with delocalized pi electrons show a great nonlinear optical response. Especially, secondary nonlinear optical constants of more than 2 digits were often seen in the molecular level compared to the existing inorganic crystals such as LiNbO3. The crystallization was continuously tried. Organic nonlinear optical crystals have a new future as materials for use in the applied physics such as photomodulation, optical frequency transformation, opto-bistabilization, and phase conjugation optics. Organic nonlinear optical materials, e.g., urea, O2NC6H4NH2, I, II, are reviewed with 50 references.
Nonlinearity-reduced interferometer
Wu, Chien-ming
2007-12-01
Periodic nonlinearity is a systematic error limiting the accuracy of displacement measurements at the nanometer level. It results from many causes such as the frequency mixing, polarization mixing, polarization-frequency mixing, and the ghost reflections. An interferometer having accuracy in displacement measurement of less than one-nanometer is necessary in nanometrology. To meet the requirement, the periodic nonlinearity should be less than deep sub-nanometer. In this paper, a nonlinearity-reduced interferometry has been proposed. Both the linear- and straightness-interferometer were tested. The developed interferometer demonstrated of a residual nonlinearity less than 25 pm.
Lower Bound Limit Analysis Of Slabs With Nonlinear Yield Criteria
DEFF Research Database (Denmark)
Krabbenhøft, Kristian; Damkilde, Lars
2002-01-01
A finite element formulation of the limit analysis of perfectly plastic slabs is given. An element with linear moment fields for which equilibrium is satisfied exactly is used in connection with an optimization algorithm taking into account the full nonlinearity of the yield criteria. Both load...
Non-linear Finite Element Analysis for Bus High-speed Crashing Performance%客车高速碰撞性能的非线性有限元研究
Institute of Scientific and Technical Information of China (English)
林繁国; 王昭均; 屈贤
2015-01-01
根据国家车辆高速碰撞法规要求，利用Hypermesh软件建立客车正面碰撞有限元模型，并基于Ls-Dyna求解器对客车正面撞击速度为50km/h进行数值仿真，得到了整车变形情况、碰撞力曲线、整车加速度曲线和前围板侵入量，这些数据对客车的结构设计具有重要参考价值。%According to the national vehicle speed collision regulations, this paper utilized Hypermesh software to establish a ifnite element model of the mini bus for crashing, and the ANSYS/Ls-Dyna solver was used for the numerical simulation of the bus under the velocity condition as 50 km/h, got the vehicle deformation , the curve of collision force , the curve of vehicle acceleration and the intrusion of dash panel,these data have important reference value for the structural design of passenger cars.
Institute of Scientific and Technical Information of China (English)
张延辉; 姜宏春; 李静; 张宝弟
2013-01-01
背景：MATLAB具有大型数值计算、数学绘图和简单有限元分析的能力，建模速度快，能够识别BMP和JPG格式的灰度图，并可将识别的数据直接转换为ANSYS三维有限元软件可识别的格式，避免了常规在Autocad软件中图像的重新定位和二次处理而产生的人为误差。 目的：寻求一种简便、快捷、准确的方法建立各种腰椎融合模型，对腰椎融合后腰椎活动节段的生物力学进行分析。 方法：利用薄层CT技术，结合Matlab(Matrix Laboratory即矩阵实验室)科学计算软件，辅助Ansys有限元分析软件建立各种腰椎融合模型。对所建立的模型施加各种载荷，分析其生物力学变化。 结果与结论：对所建立的融合模型施加轴向、屈曲及伸展载荷后，生物力学分析得出所有的融合模型中椎体间融合稳定性最好。和关节间融合相结合，椎体间，侧后方，后方融合模型的轴向位移较单独的椎体间，侧后方和后方融合模型分别减少5%、1%和4%。在伸展-屈曲载荷条件下旋转角度分别减少23%、11%和45%。应力向融合部位集中的现象表明融合块可增加载荷的转移。说明薄层CT和Matlab软件的辅助使得Ansys有限元软件建立腰椎融合模型的速度和精度提高。小关节融合和椎体间，侧后方，后方融合相结合，可使腰椎获得更好的稳定性，这种稳定性的增加在后方融合中更为显著。后方融合模型的应力分布更加合理。%BACKGROUND:MATLAB has capabilities of large numerical calculation, mathematical drawing and simple finite element analysis. It can establish models rapidly and can be able to identify the grayscale with BMP and JPG format, and it can directly transform the identified data into ANSYS finite element software-readable format, thus avoiding personal error produced by the repositioning and secondary treatment in the Autocad software
Aguirre-Ramirez, G.; Oden, J. T.
1969-01-01
Finite element method applied to heat conduction in solids with temperature dependent thermal conductivity, using nonlinear constitutive equation for heat ABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGH
40 CFR 721.10068 - Elemental mercury.
2010-07-01
... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Elemental mercury. 721.10068 Section... Substances § 721.10068 Elemental mercury. (a) Definitions. The definitions in § 721.3 apply to this section... elemental mercury (CAS. No. 7439-97-6) is subject to reporting under this section for the significant...