bluuebunny/crossref_metadata_2025_split huggingface dataset:
A penalty finite element analysis for nonlinear mechanics of biphasic hydrated soft tissue under large deformation
Authors: Suh J.‐K. , Spilker R. L. , Holmes M. H. 
Published: October 2005

AbstractThe non‐linear response of soft hydrated tissues under physiologically relevant levels of mechanical loading can be represented by a two‐phase continuum model based on the theory of mixtures. The governing equations for a biphasic soft tissue, consisting of an incompressible solid and an incompressible, inviscid fluid, under finite deformation are presented and a finite element formulation of this highly non‐linear problem is developed. The solid phase is assumed to be hyperelastic, and the stress‐strain relations for the solid phase are defined in terms of the free energy function. A finite element model is formulated via the Galerkin weighted residual method coupled with a penalty treatment of the continuity equation for the mixture. Using a total Lagrangian formulation, the non‐linear weighted residual statement, expressed with respect to the reference configuration, leads to a coupled non‐linear system of first order differential equations. The non‐linear constitutive equation for the solid phase elasticity is incrementally linearized in terms of the second Piola‐Kirchhoff stress and the corresponding Lagrangian strain. A tangent stiffness matrix is defined in terms of the free energy function; this matrix definition can be applied to any free energy function, and will yield a symmetric matrix when the free energy function is convex. An unconditionally stable implicit predictor‐corrector algorithm is used to obtain the temporal response histories. The confined compression mechanical test of soft tissue in stress relaxation is used as an example problem. Results are presented for moderate and rapid rates of loading, as well as small and large applied strains. Comparison of the finite element solution with an independent finite difference solution demonstrates the accuracy of the formulation.
A modular multibody analysis capability for high‐precision, active control and real‐time applications
Authors: Park K. C. , Downer J. D. , Chiou J. C. , Farhat C. 
Published: October 2005

AbstractA computationally oriented formulation and its solution procedures for the analysis of rigid‐flexible multibody dynamics systems are presented. The present formulation adopts a set of dual co‐ordinate systems, an inertially fixed one for the measure of translational motions and a body‐based one for rotational motions. The origins of these co‐ordinate systems are located at the centres of rigid bodies and at the nodal points of flexible bodies for implementation ease. The flexibility is modelled by an intrinsic spatial beam theory which is approximated by transverse‐shear deformable linear beam elements. The solution of the resulting equations of motion including system constraints is obtained by a partitioned procedure, which solves first for the constraint force vector, then the generalized co‐ordinates for the rigid and flexible components, and finally interaction quantities such as active control forces, manoeuvring space ranges and corrections due to state measurements, with each solution stage being processed by the corresponding separate module. A central feature of the present capability is its high accuracy of the analysis results by demanding the energy conservation throughout the various stages of response analyses. Several examples are included to demonstrate the capabilities of the present analysis software both on sequential and parallel machines.
Constrained motion of deformable bodies
Authors: Shabana A. A. 
Published: October 2005

AbstractIn this paper, issues related to the dynamic modelling of constrained deformable bodies that undergo large rigid body displacements are discussed. Particular attention is focused on finite element formulations. It is shown that the use of nodal co‐ordinates and shape functions to describe the finite rotation of some of the commonly used finite elements leads to a linearization of the kinematics and dynamic relationships. The structure of the non‐linear dynamic equations that govern the motion of deformable bodies that undergo large displacements is examined. Comments on the finite element formulation of the invariants of motion, the definition of the generalized forces and moments in flexible body dynamics and the computational strategy used for the automatic generation of the equations of motion are made. The computer formulation of the joint constraints between deformable bodies as well as the numerical algorithms currently used in many of the general purpose computer programs that are based on the augmented formulation are discussed. A decoupled joint‐elastic acceleration recursive formulation is also presented. This formulation leads to a small system of acceleration equations whose dimensions are independent of the number of the elastic degrees of freedom of the system. In this paper, the coupling between the displacements of the deformable bodies is classified as kinematic, inertia and elastic. In view of this classification, comments on the validity of using the updated finite element Lagrangian formulation and the 4 × 4 transformation matrix in the dynamic analysis of flexible multibody systems are made. The coupling between the finite rotation and the wave motion in constrained deformable bodies is also discussed.
Representation of geometric stiffening in multibody system simulation
Authors: Wallrapp Oskar , Schwertassek Richard 
Published: October 2005

AbstractGeometric, rotational or dynamic stiffening is a well and long known phenomenon in the analysis of flexible bodies. In multibody dynamics the effect has attracted attention only recently. The objective of this paper is to contribute to the understanding of the modelling of geometric stiffening in multibody system simulation. Today's methods for modelling the effect assume that the (applied) stresses in a flexible system body are zero in its reference configuration, in which it performs large overall motions. The corresponding inertial loads are shown to be balanced by constraint stresses. This can be seen easily when formulating the system equations of motion for non‐zero reference stresses. As a result one obtains an efficient alternative to compute the geometric stiffening terms. The method increases the generality of flexible body models for multibody system simulation.
Strain localization in multipotential elastoplasticity
Authors: Aubry Denis , Modaressi Arezou 
Published: October 2005

AbstractConditions of strain localization in multipotential elastoplasticity are studied in this paper for a strain discontinuity mode. The formulation is specialized to the case of a general anisotropic Mohr‐Coulomb model, where plastic shear deformations are envisaged as the contribution of microstrains in several planes. Some finite element simulations with strain projection show the relationship between the predicted direction of localization and the post bifurcation modes.
Structural analysis and optimization modelling including fracture conditions
Authors: Eschenauer H. A. , Kobelev V. V. 
Published: October 2005

AbstractThis paper introduces a model of a woven monolayer composed of two orthogonal fibres and describes an optimization technique including a fracture condition. The first fracture behaviour of the material containing a local break is analysed. The description of the stress‐state in the local break vicinity is reduced to the determination of a special form of the Green function for simultaneous finite‐difference equations. The problem allows the analytical solution for unknown functions in terms of Fourier series. The solution of the problem shows that the fracture behaviour of the material depends on the presence of stabilizing tension of fibres parallel to the crack direction. The model is used for establishing an optimization model and for applying an optimization procedure including strength conditions.
Fracture mechanics and optimal design
Authors: Pitukhin A. V. 
Published: October 2005

AbstractThe purpose of this paper is to present a mechanical fracture method for the optimal design of machine components. A single criterion design is used. Mean annual cost expenses are the objective function. They depend on the survival function. Statistical fracture mechanics methods are able to estimate machine components reliability dependence on crack‐like defect length. A numerical example is given to demonstrate the application of this method. It is recommended to evaluate the reliability of spiral cylindrical springs too.
Supporting design decisions by Prolog database
Authors: Borkowski Adam , Danicka Stanislaw Jóźwiak Małgorzata 
Published: October 2005

AbstractThe paper presents an effort to develop an ‘intelligent drawing desk’: a computer program that incorporates CAD, structural analysis and optimization, database query and automatic choice of the initial design. The advantages of such an integrated software are demonstrated on the testbed of plane steel trusses.After a brief presentation of the conventional part of the package, its expert module is discussed more thoroughly. Implemented in ‘Prolog’, that module aids the user in choosing the initial layout of the truss. It checks and supplements, if necessary, the values of the structural attributes given by the designer. After a complete set of attributes has been established, the module searches for similar solutions in the database. The latter represents the experience, i.e. all solutions accepted by the user in the past. An initial design is obtained without strength analysis by matching the current values of the attributes against those stored in the database. Provided the latter is exhaustive enough, one obtains in this way quite reasonable initial values of the design variables. The final design can be found then by using conventional analysis, optimization and sizing procedures that belong to the procedural part of the package.
Automated adaptive analysis of the biphasic equations for soft tissue mechanics using a posteriori error indicators
Authors: Donzelli P. S. , Spilker R. L. , Baehmann P. L. , Niu Q. , Shephard M. S. 
Published: October 2005

AbstractHydrated soft tissues of the human musculoskeletal system, such as articular cartilage in diarthrodial joints or the annulus fibrosis of the inter vertebral disk, are accurately represented by a biphasic continuum model consisting of an incompressible solid phase (collagen and proteoglycan) and incompressible, inviscid fluid (interstitial fluid) and derive from the continuum theory of mixtures. These tissues exhibit a viscoelastic‐type response which is caused by the diffusive drag of the fluid phase as it flows past the solid phase. In this study an automated, adaptive, finite element solution of the governing biphasic equations is presented. The finite element formulation is based on a mixed‐penalty approach in which the penalty form of the continuity equation for the mixture is included in the weak form. Pressure, solid and fluid velocities are interpolated independently, and the coefficients of the C−1 pressure field are eliminated at the element level. The resulting matrix form is a system of first order differential equations which is solved via standard finite difference methods. Mesh generation and updating, including both refinement and coarsening, for the two‐dimensional examples examined in this study are performed using Finite Quadtree. The adaptive analysis is based on an error indicator which is the L2 norm of the difference between the finite element solution and a projected finite element solution. Total stress, calculated as the sum of the solid and fluid phase stresses, is used in the error indicator. Rezoning is accomplished by transferring the finite element solution for the primary variables onto the locally updated mesh using a projected field. These projected values allow the finite difference algorithm to proceed in time using the updated mesh. The accuracy and effectiveness of this adaptive finite element analysis is demonstrated using two‐dimensional axisymmetric problems corresponding to the uncomined compression of a cylindrical disk of soft tissue and the indentation of a thin sheet of soft tissue. The method is shown to effectively capture the steep gradients in both problems and to produce solutions in good agreement with independent, converged, numerical solutions.
Characteristic, local grid refinement techniques for reservoir flow problems
Authors: Dahle Helge K. , Espedal Magne S. , Sævareid Ove 
Published: October 2005

AbstractUsing a sequential time‐marching approach, we describe and implement effective solution strategies for the equations governing immiscible displacement in a porous medium. By combining adaptive grid refinement with an operator‐splitting technique based on the modified method of characteristics, the saturation equation is treated in a consistent and accurate way. For the pressure equation we construct accurate piecewise linear velocity components from a piecewise linear pressure approximation.
Accelerated bisection techniques for tri‐ and quindiagonal matrices
Authors: Baker Graham 
Published: October 2005

AbstractThis paper considers accelerated bisection methods for calculating the eigenvalues of symmetric tridiagonal and quindiagonal matrices using cubic polynomial interpolation, as well as first and second order Newton iteration. Recursive relations based on the Sturm sequences are presented for the Newton type methods. The relations use a convenient scaling which retains the relative magnitudes in the iterative schemes but which avoids numerical overflow. Numerical examples show a significant increase in convergence rate.
A multicorner variable order singularity triangle to model neighbouring singularities
Authors: Maiti S. K. 
Published: October 2005

AbstractA six noded triangular finite element has been proposed to model variable order singularities in the first derivatives of field variables occurring at multiple locations (up to three) lying in close proximity. The element satisfies the convergence requirements fully. The element will be very useful in the analysis of neighbouring cracks, zig‐zag cracks, kinked cracks, etc., involving mechanical and/or thermal loadings. The first degenerate form, which is a two point variable order singularity element, can be used, for example, to cover the distance between two adjacent crack tips. The second degenerate form, which is a one point variable order singularity element, can be used around a crack tip like any other crack tip elements. Six case studies have been reported, three involving mechanical loadings and the other three thermal loadings. These have helped to check the performance of the element and its two degenerate forms. The accuracy of the results in all the examples is good.
A finite element approach for modelling metal flow and pressurised solidification in the squeeze casting process
Authors: Gethin D. T. , Lewis R. W. , Tadayon M. R. 
Published: October 2005

AbstractA finite element numerical modelling procedure for simulating combined flow and heat transfer in a squeeze casting process is developed where the flow model is based on simple mass conservation. The coincident node method is used to model the thermal interface with metal advancement over the relatively colder die surface. The effect of pressure on the solidus and liquidus temperatures is built in based on the Clausius‐Clapeyron equation and the thermophysical properties of enthalpy and thermal conductivity are affected by this pressure. For the casting material concerned, the effect of pressure on thermophysical properties was found to be small, having only a marginal effect on the part solidification.
Direct formulation of a hybrid 4‐node shell element with drilling degrees of freedom
Authors: Aminpour M. A. 
Published: October 2005

AbstractA simple 4‐node assumed‐stress hybrid quadrilateral shell element with rotational or 'drilling' degrees of freedom is formulated. The element formulation is based directly on a 4‐node element. This direct formulation requires fewer computations than a similar element that is derived from an 'internal' 8‐node isoparametric element in which the midside degrees of freedom are eliminated by expressing them in terms of displacements and rotations at corner nodes. The formulation is based on the principle of minimum complementary energy. The membrane part of the element has 12 degrees of freedom, including the drilling degrees of freedom. The bending part of the element also has 12 degrees of freedom. The bending part of the element uses the Reissner‐Mindlin plate theory which takes into account the transverse shear effects. Quadratic variations for both in‐plane and out‐of‐plane displacement fields and linear variations for both in‐plane and out‐of‐plane rotation fields are assumed along the edges of the element. The element Cartesian‐co‐ordinate system is selected such as to make the stress field invariant with respect to node numbering. The membrane part of the stress field is based on a 9‐parameter equilibrating stress field, while the bending part is based on a 13‐parameter equilibrating stress field. The element passes the patch test, is nearly insensitive to mesh distortion, alleviates the 'locking' phenomenon, is invariant with respect to node numbering, has no hidden spurious modes, and produces accurate and reliable results.
A stabilization procedure by line‐search computation for first order approximation strategies in structural optimization
Authors: Mahnken R. , Stein E. , Bischoff D. 
Published: October 2005

AbstractThe paper is concerned with first order approximation methods to solve non‐linear optimization problems as they arise in structural optimization. A modification of the original Method of Moving Asymptotes (MMA) is presented to prevent oscillation or divergence by incorporating a line‐search into the global iteration algorithm. In this line‐search a merit‐function of augmented Lagrangian type is decreased by using a backtracking strategy. A proof is presented to show the descent property of the proposed merit‐function for MMA. Numerical examples demonstrate how the new technique stabilizes the iteration process.
A finite element method for domains with corners
Authors: Givoli Dan , Rivkin Leonid , Keller Joseph B. 
Published: October 2005

AbstractA new finite element method is devised for the numerical solution of elliptic boundary value problems with geometrical singularities. In it, the singularity is eliminated form the computational domain in an exact fashion. This is in contrast to other common methods, such as those which use a refined mesh in the singularity region, or those which use special singular finite elements. In them, the singularity is treated as a part of the numerical scheme. The new method is illustrated on an elliptic differential equation in a domain containing a re‐entrant corner. Numerical experiments show that the new method yields result which are generally much more accurate than those obtained by using the standard finite element method with mesh refinement in the singularity region. Both methods require about the same computing time.
Polynomial particular solutions based boundary element analysis of acoustic eigenfrequency problems
Authors: Raveendra S. T. , Banerjee P. K. 
Published: October 2005

AbstractThe boundary element formulation for acoustic eigenfrequency analysis based on treating the forcing function, in the governing differential equation, as an initially unknown distributed source within the domain is presented. The volume integral due to this distributed source is eliminated by approximating the internal source by global interpolation and polynomial function representations and finding particular solutions for the governing, inhomogeneous equations. The resulting non‐symmetric system matrix is solved by using Arnoldi's algorithm, modified to take advantage of the special structure of the substructured boundary element method. The techniques described here are embedded in a computer program GPBEST, and the numerical results are obtained by using this computer code.
Evaluation of dust and hybrid mixture explosion potential in process plants
Authors: Dastidar Ashok Ghose , Nalda‐Reyes Bernadette , Dahn C. James 
Published: October 2005

AbstractDust explosions are a serious hazard in the process industries. They have resulted in the destruction of process plants and equipment, injury to workers, and loss of production. The five factors required for a dust explosion are: (1) fuel, (2) oxidant, (3) confinement, (4) dispersion, and (5) ignition source. These factors are often embodied in an “explosion pentagon.” Disruption of any one of these factors can prevent a dust explosion from occurring. Before mitigation of a dust explosion can take place, one has to realize the full extent of the explosion potential of the dust/powder material in the intended process environment. This can be achieved by focusing on the many ways that these five components can come together in a specific process condition to form a pentagon.This risk constitutes two components: the probability of the explosion and the severity of the consequences. Both factors have to be fully realized to evaluate the dust explosion risk. Currently, standard test protocols are followed to establish a relative measure of these two factors. However, these standard test methods may not reflect the true process environment and interpretation of the results are required.The purpose of this work is to review test methodologies for assessing the magnitude of an explosion in a process environment and the ease at which the dust explosion can be initiated. This article will also critique how they may be applied to “real‐world” process environments and potential mitigation steps to break the “explosion pentagon.” © 2005 American Institute of Chemical Engineers Process Saf Prog, 2005
Trace element determination in hair by synchrotron x‐ray fluorescence analysis: application to the hair of Napoleon I
Authors: Chevallier P. , Ricordel I. , Meyer G. 
Published: October 2005

AbstractSeveral hairs belonging to Napoleon I were analyzed through synchrotron induced x‐ray fluorescence analysis. This study revealed the presence of many toxic elements, often far above the lethal content, and with important concentration variations from one hair to another and even from one place to another in a same sample. This does not seem to favor the simple hypothesis of poisoning through arsenic ingestion. Copyright © 2005 John Wiley & Sons, Ltd.
Tramadol‐induced blockade of delayed rectifier potassium current in NG108‐15 neuronal cells
Authors: Tsai Tung‐Ying , Tsai Yu‐Chuan , Wu Sheng‐Nan , Liu Yen‐Chin 
Published: October 2005

AbstractTramadol is a centrally acting analgesic drug used mainly in the moderate to severe pain control. In this study, the effects of this agent on ion currents of NG108‐15 neuronal cells were investigated. This cell line expresses Kv3.1a mRNAs and exhibits the activity of delayed rectifier K+(KDR) channels. Tramadol suppressed the amplitude of delayed rectifier K+current (IK(DR)) in a concentration‐dependent manner with an IC50values of 25 μM. Tramadol (30 μM) also shifted the steady‐state inactivation ofIK(DR)to a more negative membrane potential by approximately −15 mV. The role of the KDRchannel, particularly as a member of the Kv3 superfamily, is to stabilize the resting potential and to reduce the width of action potentials in the time‐coding neurons. Tramadol‐induced block ofIK(DR)observed in this study could be partly responsible for its anti‐depressant action.