bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and computation of slow‐burning pyrotechnical compositions using a fixed mesh finite element formulation
Authors: Loyd Dan , Andersson Gunnar , Karlsson Matts 
Published: November 2005

AbstractThe ignition of explosives and illuminants can be controlled and delayed by using a combination of different pyrotechnical compositions. For quick‐burning compositions the burning velocity is mostly determined by the properties of the compositions and by the geometry of the case: For low burning velocity, however, both the initial temperature and the heat transfer from the compositions are important factors. The influence of a phase transition process in the composition is here a factor important for the burning velocity.By a suitable design of the case containing the pyrotechnical compositions and a suitable choice of these compositions, performance, as well as safety, can be improved. The design work is complex and comprises numerical simulations, laboratory tests and full scale tests. Generally it is preferable to start with a numerical analysis of the problem. The number of laboratory and full scale tests must always be minimized as they are time‐consuming and expensive, and thus numerical models are essential as a cheap and reliable tool in the design work.Statistical design of experiments has been used to reduce the number of numerical calculations required for evaluating the influence of different parameters essential for the burning velocity. From these calculations a limited number of laboratory and full scale experiments are planned. The number of tests as well as the cost will be reduced.Special procedures based on the finite element method are used both for the phase transition process and for the combustion process. The latent heat of a region with phase change material is concentrated at the nodes of the elements in that region. A fixed finite element mesh is used. The temperature of a node with latent heat is kept at the melting temperature during the transition process.The heat of combustion is associated with the finite elements. The combustion starts when the mean temperature of such an element exceeds the ignition temperature of the composition and ceases when all the heat of combustion in the element is released or if the temperature of the element falls below the ignition temperature. The elements with ongoing combustion form a reaction zone, which propagates into the pyrotechnical composition.In the present study the method is applied to a test case in order to investigate the applicability of the method.
Development of a monte carlo method for numerical analysis on radiative energy transfer through non‐grey‐gas layer
Authors: Taniguchi Hiroshi , Kudo Kazuhiko , Otaka Maromu , Sumarsono Markus , Obata Masakazu 
Published: November 2005

AbstractAn analytical method is developed to study the radiative energy transfer in a non‐grey‐gas layer by using a Monte Carlo method. The gas is composed of water vapour, carbon dioxide and nitrogen. The profiles of the monochromatic absorption coefficient of each component gas are calculated by using the Elsasser model and wide band model parameters derived by Edwards. The validity of this method is confirmed by comparing the results of the gas emissivity with the ones obtained from Hottel's chart. By using this method, radiative energy transfer is analysed through a one dimensional gas layer between two parallel solid walls with different temperatures. From the analyses, it is shown that the temperature profile in the gas layer is not properly estimated by using Hottel's gas‐emissivity charts, though the net heat flux between the bounding walls is estimated properly.
A simple class of finite elements for plate and shell problems. I: Elements for beams and thin flat plates
Authors: Phaal R. , Calladine C. R. 
Published: November 2005

AbstractThis is the first paper of a pair which together discuss the development of a class of overlapping hinged bending finite elements which are suitable for the analysis of thin‐shell, plate and beam structures. These elements rely on a simple physical analogy, involving overlapping hinged facets. They are based on quadratic overlapping assumed displacement functions. Only translational nodal degrees of freedom are necessary, which is a significant simplification over most other currently available beam, plate and shell finite elements which employ translational, rotational and higher‐order nodal variables. In this paper the hinged bending element concept is introduced, and the hinged beam bending (HBB) and hinged plate bending (HPB) elements are formulated. In paper II these concepts are extended to develop a hinged shell bending (HSB) element. The HSB element can be readily combined with the constant strain triangular (CST) plane stress finite element for the modelling of thin‐shell structures.
A simple class of finite elements for plate and shell problems. II: An element for thin shells, with only translational degrees of freedom
Authors: Phaal R. , Calladine C. R. 
Published: November 2005

AbstractThis paper is the second of a pair which discuss the development of a class of overlapping hinged bending finite elements, which are suitable for the analysis of thin‐shell, plate and beam structures. These elements rely on a simple physically appealing analogy, in which overlapping hinged facets are used to represent bending effects. They are based on quadratic overlapping assumed displacement functions, which results in constant stress/strain representation. Only translational nodal degrees of freedom are necessary, which is a significant advantage over most other currently available beam, plate and shell finite elements which employ translational, rotational and higher‐order nodal variables. In paper I the hinged bending element concept has been introduced, and the hinged beam bending (HBB) and hinged plate bending (HPB) elements formulated. In the present paper these concepts are extended to develop a hinged shell bending (HSB) element. The HSB element can be readily combined with the constant strain triangular (CST) plane stress finite element for the modelling of thin‐shell structures; and the combined HSB‐CST element is tested against a number of 'standard' thin‐shell problems. The present paper, like paper I, is conducted entirely in the context of small‐displacement elastic behaviour.
Tabu search method with random moves for globally optimal design
Authors: Hu Nanfang 
Published: November 2005

AbstractOptimum engineering design problems are usually formulated as non‐convex optimization problems of continuous variables. Because of the absence of convexity structure, they can have multiple minima, and global optimization becomes difficult. Traditional methods of optimization, such as penalty methods, can often be trapped at a local optimum. The tabu search method with random moves to solve approximately these problems is introduced. Its reliability and efficiency are examined with the help of standard test functions. By the analysis of the implementations, it is seen that this method is easy to use, and no derivative information is necessary. It outperforms the random search method and composite genetic algorithm. In particular, it is applied to minimum weight design examples of a three‐bar truss, coil springs, a Z‐section and a channel section. For the channel section, the optimal design using the tabu search method with random moves saved 26.14 per cent over the weight of the SUMT method.
A finite element method for the probabilistic creep of solids
Authors: Delph T. J. , Yukich J. E. 
Published: November 2005

AbstractWe outline here a finite element technique for the creep of solids whose constitutive equation contains one or more random parameters. In contrast to other finite element techniques for the prediction of random structural response, the present method is based upon exact relations from the theory of probability. It yields, at a given value of time, the probability density function for the field variable of interest, e.g. stress or displacement components. The method is illustrated by a simple creeping beam problem, using a power‐law creep constitutive equation. The calculated distributions are found to be highly skewed, and in excellent agreement with the results of Monte Carlo simulation.
Finite element dispersion analysis for the three‐dimensional second‐order scalar wave equation
Authors: Abboud Najib N. , Pinsky Peter M. 
Published: November 2005

AbstractThe dispersive properties of finite element semidiscretizations of the three‐dimensional second‐order scalar wave equation are examined for both plane and spherical waves. This analysis throws light on the performance and limitations of the finite element approximation over the entire spectrum of wavenumbers and provides guidance for optimal mesh discretization as well as mass representation. The 8‐node trilinear element, 20‐node serendipity element, 27‐node triquadratic element and the linear and quadratic spherically symmetric elements are considered.
Elastoplastic analysis using the 14‐node brick element family
Authors: Smith I. M. , Kidger D. J. 
Published: November 2005

AbstractTypical brick‐based finite elements in current use are the 8‐and 20‐node members of the serendipity group. For displacement analyses of solids the 8‐node element can be quite stiff in certain deformation modes, while the 20‐node element can be quite expensive to use, involving as it does 60 degrees of freedom and a fairly high order of quadrature to avoid spurious eigenmodes of the element stiffness. In this paper a family of intermediate 14‐node elements is investigated. Derivation of their properties can be considerably assisted by computer algebra. Performance is evaluated for elastic and elastoplastic problems.
Computational model for 3‐D contact problems with friction based on the penalty method
Authors: Perić Djordje , Owen D. R. J. 
Published: November 2005

AbstractA model based on the penalty method for 3‐D contact problems with friction is proposed. The friction forces are assumed to follow the Coulomb law, with a slip criterion treated in the context of a standard return mapping algorithm. Consistent linearization of the field equations is performed which leads to a fully implicit scheme with non‐symmetric tangent stiffness which preserves asymptotic quadratic convergence of the Newton‐Raphson method. Numerical results are obtained for some representative examples and compared with existing solutions.
Preconditioning techniques for non‐symmetric matrices with application to temperature calculations of cooled concrete
Authors: Van Der Ploeg Auke 
Published: November 2005

AbstractPreconditioning techniques based on incomplete LU‐decomposition are described for large, sparse, non‐symmetric matrix systems in which the largest part of the coefficient matrix is a symmetric M‐matrix with a very regular sparsity pattern. Some methods are described in which a small part of the matrix with an irregular sparsity pattern is treated very efficiently. The methods are combined with CGSTAB and tested on a non‐stationary diffusion problem in three dimensions. For this type of problems the modified incomplete decomposition as suggested by Gustafsson performs significantly better than the standard incomplete factorization.Also some methods are described to construct preconditioners for large, sparse, non‐symmetric matrices with arbitrary sparsity patterns. Methods in which the sparsity pattern of the preconditioning matrix is based on a drop tolerance are very effective and relatively cheap.
Solutions to shape and topology eigenvalue optimization problems using a homogenization method
Authors: Díaaz Alejandro R. , Kikuchi Noboru 
Published: November 2005

AbstractA solution strategy to find the shape and topology of structures that maximize a natural frequency is presented. The methodology is based on a homogenization method and the representation of the shape of the structure as a material property. The problem is formulated as a reinforcement problem in which a given structure is reinforced using a prescribed amount of material. Two dimensional, plane elasticity problems are considered. Examples are presented for illustration.
Partial mixed 3‐D element for the analysis of thick laminated composite structures
Authors: Liao Chung‐Li , Tsai J.‐ S. 
Published: November 2005

AbstractFor the analysis of thick laminated composite structures this paper proposes a partial mixed 3‐D element. The variational principle of this new element is obtained by modifying the Hellinger–Reissner principle. The functional of the present stationary principle is constructed by treating three displacements (u, v, w) and two transverse shear stresses (τxz, τyz) as independent of each other. Hence the nodal variables of the present mixed element contain three displacements and two transverse shear stresses. The other stresses (σx, σy, τxy, σz) are computed from the assumed displacement field and nodal displacement field and nodal displacements. The present element can satisfy the requirements of (1)transverse shear stress continuity between laminate layers and (2)boundary conditions of free transverse shear stresses on the top and bottom surfaces. These requirements are violated by conventional displacement finite elements. Since the stiffness matrix of the present element is formulated by combining a displacement model and a mixed model, it is definite, rather than indefinite as for the conventional mixed elements. Also, these two transverse shear stresses are part of the solution variables and are solved directly together with displacements. Examples are presented to demonstrate the accuracy and efficiency of this proposed partial mixed 3‐D element in the analysis of thick laminated composite structures.
A time integration algorithm for elasto‐viscoplastic cubic crystals applied to modelling polycrystalline deformation
Authors: Maniatty A. M. , Dawson P. R. , Lee Y. ‐S. 
Published: November 2005

AbstractAn algorithm for integrating the constitutive equations for an elasto‐viscoplastic cubic crystal is presented which is shown to be easily employed in a polycrystalliné analysis. Anisotropic elastic behaviour is incorporated into the standard constitutive equations for ductile single crystals. The algorithm is shown to be efficient, robust and general. The primary advantage of this algorithm is that is provides an implicit integration of the plastic deformation gradient while including the elastic response. This permits taking large time steps while maintaining accuracy and stability. Several polycrystalline examples are presented to demonstrate the effect of the time step on the solution. Examples also are presented which compare the algorithm described herein to an algorithm which neglects the elastic part of the deformation. In addition, the effect of the anisotropic component of the elasticity is investigated by comparing the results with those obtained assuming isotropic elasticity.
Use of ‘simple solutions’ for boundary integral methods in elasticity and fracture analysis
Authors: Lutz Earlin , Ingraffea Anthony R. , Gray Leonard J. 
Published: November 2005

AbstractThe 'simple solutions' or 'indirect' method of analysing Cauchy and hypersingular integrands in the gradient (flux or traction) boundary integral equation (BIE) is applied to linear elastic fracture analysis. Because of the geometric singularity of the crack surface, application of the simple solutions formulas on the crack face requires integration over a temporary 'closure surface' rather than the remainder of the body. Closure surface constructions are exhibited for crack surfaces, allowing the gradient BIE to be applied as a constraint equation on a crack surface where the primary BIE is degenerate. Computational results are given for two benchmark fracture problems.
A consistent co‐rotational formulation for shells using the constant stress/constant moment triangle
Authors: Peng X. , Crisfield M. A. 
Published: November 2005

AbstractThe simplest facet‐shell formulation involves the combination of the constant‐strain membrane triangle with a constant‐curvature bending triangle. The paper describes a technique whereby this facet‐formulation is extended to handle geometric non‐linearity by means of a co‐rotational procedure. Emphasis is placed on the derivation of a technique that is increment‐independent with both the internal force vector and tangent stiffness matrix being derived from the 'total strain measures' in a 'consistent manner'. Numerical examples are presented which demonstrate an excellent numerical performance.
Effect of cross‐sectional warping of anisotropic sandwich laminates due to dynamic loads using a refined theory and C° finite elements
Authors: Mallikarjuna  , Kant T. 
Published: November 2005

AbstractAn attempt has been made to study the effect of cross‐sectional warping in the symmetrically laminated anisotropic composite sandwich plates for transient loads. A higher‐order shear deformation theory (HOST) is used in conjunction with the simple displacement based C° finite element method (FEM). As is well‐known, the classical first‐order theories hitherto considered were inadequate to describe the propagation of waves in the highly orthotropic sandwich laminates. The present theory, which is more accurate than the Reissner‐Mindlin theory, is applied herein, for the evaluation of plate response to different types of dynamic loads. An explicit central difference scheme is employed for the integration of dynamic equations of equilibrium with a diagonalized mass matrix obtained by a special procedure applicable to quadrilateral isoparametric elements. The numerical results of the present investigation have been compared with the first‐order shear deformation theory (FOST) and the differences between HOST and FOST are examined. The results presented here should be useful in obtaining better correlation between theory and experiment, and to numerical analysts in verifying their results.
An infinite boundary element formulation for three‐dimensional potential problems
Authors: Kaljević Igor , Saigal Sunil , Ali Ashraf 
Published: November 2005

AbstractAn infinite boundary element (IBE) is presented for the analysis of three‐dimensional potential problems in an unbounded medium. The IBE formulations are done to allow their coupling with the finite element (FE) matrices for finite domains and to obtain the overall matrices without destroying the banded structure of the FE matrices. The infinite body is divided into a number of zones whose contributions are expressed in terms of the nodal quantities at FE nodes by employing suitable decay functions and performing mainly analytical integrations of the boundary element kernels. The continuity and compatibility conditions for the potential and the flux at the FE‐IBE interface are developed. The relationships for the contributions of the IBE flux vectors to the FE load vectors are given. The final equations for the IBE are obtained in the usual FE stiffness‐load vector form and are easily assembled with the FE matrices for the finite object. A series of numerical examples in heat transfer and electromagnetics were solved and compared with alternative solutions to demonstrate the validity of the present formulations.
Ionic liquids as novel solvents and catalysts for the direct polycondensation of N,N′‐(4,4′‐oxydiphthaloyl)‐bis‐L‐phenylalanine diacid with various aromatic diamines
Authors: Mallakpour Shadpour , Kowsari Elaheh 
Published: November 2005

AbstractIonic liquids (ILs) are often considered green solvents capable of replacing traditional organic solvents and have been extensively studied in materials chemistry and catalysis. In this study, the direct polycondensation of N,N′‐(4,4′‐oxydiphthaloyl)‐bis‐L‐phenylalanine diacid with various aromatic diamines was performed in IL media. The influence of various reaction parameters, including the nature of the IL cations and anions, the monomer structures, the reaction temperature, and the reaction time, on the yields and inherent viscosities of the resulting optically active poly(amide imide)s (PAIs) were investigated. Direct polycondensation successfully preceded in ILs and triphenyl phosphite (a condensing agent) without any additional extra components, such as LiCl and pyridine, which are used in similar reactions in ordinary molecular solvents. Therefore, ILs can act as both solvents and catalysts. Various high‐molecular‐weight, optically active PAIs were obtained in high yields with inherent viscosities ranging from 0.54 to 0.88 dL/g. This method was also compared with three other classical methods for the polycondensation of the aforementioned monomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6545–6553, 2005
Amphiphilic star‐block copolymers based on a hyperbranched core: Synthesis and supramolecular self‐assembly
Authors: Jia Zhifeng , Zhou Yongfeng , Yan Deyue 
Published: November 2005

AbstractNovel amphiphilic star‐block copolymers, star poly(caprolactone)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] and poly(caprolactone)‐block‐poly(methacrylic acid), with hyperbranched poly(2‐hydroxyethyl methacrylate) (PHEMA–OH) as a core moiety were synthesized and characterized. The star‐block copolymers were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA–OH with 18 hydroxyl end groups on average was used as an initiator for the ring‐opening polymerization of ε‐caprolactone to produce PHEMA–PCL star homopolymers [PHEMA = poly(2‐hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA–PCL were converted to 2‐bromoesters, and this gave rise to macroinitiator PHEMA–PCL–Br for ATRP. Then, 2‐dimethylaminoethyl methacrylate or tert‐butyl methacrylate was polymerized from the macroinitiators, and this afforded the star‐block copolymers PHEMA–PCL–PDMA [PDMA = poly(2‐dimethylaminoethyl methacrylate)] and PHEMA–PCL–PtBMA [PtBMA = poly(tert‐butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl methacrylate) blocks gave the star‐block copolymer PHEMA–PCL–PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star‐block copolymers could self‐assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534–6544, 2005
Block polymethacrylonitrile copolymers based on a central polyether or polyacetal block: A study of the salt/copolymer complexes
Authors: Saunier J. , Alloin F. 
Published: November 2005

AbstractSome block copolymers based on polymethacrylonitrile (PMAN) and polyethers or polyacetals were synthesized in an anionic way. To appreciate the salt/polymer interactions, polymer electrolytes were prepared by the dissolution of lithium imide or lithium perchlorate in PMAN homopolymer and copolymers. The investigation of the triblock copolymer complexes allowed the solvating competition between nitrile‐ and ether‐ or acetal‐functional groups to be highlighted. The polydioxolane solvating ability was equivalent to that of PMAN but lower than that of polyoxyethylene or polyoxypropylene. Moreover, we were interested in the salt effect as block compatibilization was concerned. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3665–3673, 2005