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  • 1
    Electronic Resource
    Electronic Resource
    The boundary contour method for two-dimensional linear elasticity with quadratic boundary elements (1997)
    Springer
    Computational mechanics 20 (1997), S. 310-319 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a further development of the Boundary Contour Method (BCM) for two-dimensional linear elasticity. The new developments are: (a) explicit use of the rigid body motion solution to regularize the BCM and avoid computation of the corner tensor, (b) quadratic boundary elements compared to linear elements in previous work and (c) evaluation of stresses both inside and on the boundary of a body. This method allows boundary stress computations at regular points (i.e. at points where the boundary is locally smooth) inside boundary elements without the need of any special algorithms for the numerical evaluation of hypersingular integrals. Numerical solutions for illustrative examples are compared with analytical ones. The numerical results are uniformly accurate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660050253
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  • 2
    Electronic Resource
    Electronic Resource
    A mapping method for numerical evaluation of two-dimensional integrals with 1/r singularity (1993)
    Springer
    Computational mechanics 12 (1993), S. 19-26 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Singular integrals occur commonly in applications of the boundary element method (BEM). A simple mapping method is presented here for the numerical evaluation of two-dimensional integrals in which the integrands, at worst, are O(1/r) (r being the distance from a source to a field point). This mapping transforms such integrals over general curved triangles into regular 2-D integrals. Over flat and curved quadratic triangles, regular line integrals are obtained, and these can be easily evaluated by standard Gaussian quadrature. Numerical tests on some typical singular integrals, encountered in BEM applications, demonstrate the accuracy and efficacy of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370482
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  • 3
    Electronic Resource
    Electronic Resource
    Leishmania donovani: Superoxide dismutase level in infected macrophages (1988)
    Springer
    Bioscience reports 8 (1988), S. 131-137 
    Details
    ISSN: 1573-4935
    Keywords: superoxide dismutase ; macrophage ; Leishmania donovani
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Superoxide dismutase (SOD), a metal containing enzyme is present in parasiteLeishmania donovani as well as in host macrophages both resident and activated in a detectable amount, although the level is much higher in the latter case. It is observed that at any particular protein concentration, the SOD activity is highest in the case of parasite infected macrophages and lowest in the case of normal resident macrophages; the SOD activity of thioglycolate activated macrophages lies in between the two. It is also noticed that formalin-killedLeishmania donovani neither attach to macrophages nor do they increase the SOD activity of the host. Thus, the processes, e.g. attachment of the parasite to the host membrane, subsequent membrane perturbation and thus activation of membrane bound enzyme NADPH oxidase leading to respiratory burst, may be responsible for an enormous increase in the SOD level in macrophages during infection. Moreover, the chemical nature of the SOD found in infected macrophages has been investigated by using an inhibitor, e.g. NaCN, which specifically inhibits Cu−Zn SOD but not Fe−SOD. A considerable inhibition of SOD activity by NaCN in infected macrophages confirms the chemical nature of the increased SOD to be of Cu−Zn type, usually found in host. Presumably, Cu−Zn SOD or host SOD plays a protective role at the time of parasite infection although the role of parasitic SOD or some other mechanisms for the survival of the parasite within the toxic phagolysosome environment, of the macrophage cannot be ruled out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01116457
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  • 4
    Electronic Resource
    Electronic Resource
    Numerical solutions for stresses near crack tips in time-dependent inelastic fracture mechanics (1982)
    Springer
    International journal of fracture 18 (1982), S. 293-310 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé Dans ce mémoire, on utilise la méthode des éléments aux limites pour calculer les contraintes dans un corps planaire fini au sein duquel est présente une fissure libre de contrainte de traction. On suppose que le corps est soumis à des déformations inélastiques dépendant du temps et qu'il est décrit par un modèle constitutif de fluage comportant une portion élastique et une portion parabolique. Une fissure stationaire est représentée par une ellipse très mince et les solutions numériques au problème complet des transitoires sont obtenues par une intégration par paliers dans le temps. Les résultats numériques pour les contraintes au voisinage de l'extrémité de la fissure sont comparés avec les résultats analytiques asymptotiques obtenus par d'autres chercheurs. Ces résultats asymptotiques correspondent à une plaque comportant une fissure linéique, pour laquelle on néglige les vitesses de déformation élastique par rapport aux vitesses de déformation non elastique au voisinage des extrémités de la fissure. On considère dans les calculs à la fois la déformation de mode I et de mode III sous des conditions de mise en charge extérieures dépendant ou ne dépendant pas du temps.
    Notes: Abstract The boundary element method is used in this paper to calculate the stresses in a finite planar body with a traction free crack present in it. The body is assumed to undergo time-dependent inelastic deformation and is described by an elastic-power law creep constitutive model. A stationary crack is modelled as a very thin ellipse and numerical solutions to the complete transient problem are obtained by step-wise integration in time. The numerical results for stresses near a crack tip are compared with the asymptotic analytical results obtained by other researchers. These asymptotic results are those for a plate with a line crack where the elastic strain rates are neglected relative to the nonelastic strain rates near the crack tips. Both Mode III and Mode I deformation, under time-independent and time-dependent remote loading, are considered in the calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015689
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  • 5
    Electronic Resource
    Electronic Resource
    BEM and FEM analysis of planar moving cracks in creeping solids (1985)
    Springer
    International journal of fracture 28 (1985), S. 83-101 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé Le sujet du mémoire est l'application de la méthode par valeurs aux limites (BEM) et de la méthode par éléments finis (FEM) à l'analyse de problèmes bidimensionnels de fissures en extension dans des composants soumis à fluage. En l'absence d'une loi d'extension de fissure qui soit applicable tant sous des conditions de fluage transitoire à petite échelle que de fluage stable généralisé, on procède aux simulations per calcul on considérant le développement d'une fissure à des vitesses constantes fixées. On montre que la méthode BEM est plus efficace pour analyser la croissance d'une fissure de fluage en régime transitoire à une petite échelle, tandis que la méthode FEM convient le mieux pour étudier la croissance d'une fissure dans des conditions de fluage s'étendant à l'ensemble du composant. Dès lors, les deux méthodes tendent à se compléter pour cette classe de problèmes. On estime que les méthodes numériques qui sont présentées ici, peuvent être très utiles, en association avec des essais, pour évaluer les lois existantes en matière de propagation de fissures, ainsi que pour en développer de nouvelles.
    Notes: Abstract Applications of the boundary element method (BEM) and the finite element method (FEM), to the analysis of two-dimensional problems of moving cracks in creeping bodies, is the subject of this paper. In the absence of an acceptable crack growth law valid under small scale transient as well as extended steady state creep conditions, the computer simulations are carried out here for crack extension at prescribed constant speeds. It is shown here that the BEM is most effective for the analysis of transient crack growth under small scale creep conditions while the FEM appears to be best suited for the study of crack growth under conditions of extensive creep throughout most of the structure. These two methods, therefore, tend to complement each other for this class of problems. It is felt that the numerical methods presented here can, in conjunction with experiments, be very useful for the evaluation of existing crack growth laws as well as for the development of new ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018586
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  • 6
    Electronic Resource
    Electronic Resource
    A new algorithm for finding a pseudoperipheral vertex or the endpoints of a pseudodiameter in a graph (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 913-926 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Based on the concept of the Laplacian matrix of a graph, this paper presents the SGPD (spectral graph pseudoperipheral and pseudodiameter) algorithm for finding a pseudoperipheral vertex or the end-points of a pseudodiameter in a graph. This algorithm is compared with the ones by Grimes et al. (1990), George and Liu (1979), and Gibbs et al. (1976). Numerical results from a collection of benchmark test problems show the effectiveness of the proposed algorithm. Moreover, it is shown that this algorithm can be efficiently used in conjunction with heuristic algorithms for ordering sparse matrix equations. Such heuristic algorithms, of course, must be the ones which use the pseudoperipheral vertex or pseudodiameter concepts.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640101107
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  • 7
    Electronic Resource
    Electronic Resource
    On the application of 2D potential theory to electrostatic simulation (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 691-701 
    Details
    ISSN: 1069-8299
    Keywords: electrostatic simulation ; charge density ; potential theory ; MEMS ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Computing the charge density on the surfaces of conductors is fundamental to many electrostatic applications. Difficulties arise in two-dimensional simulation due to the O(log|r|) potential. Fully understanding the 2D potential problem, and reasonably connecting the mathematical formulation with physical interpretation, are key to handling this difficulty properly. In the absence of these factors it is easy for one to propose an ill-posed problem. In this paper, a complete investigation of potential theory, from 3D to 2D, is made for computing charge density on the surfaces of conductors. Various integral formulations are derived - these are applicable in different situations. It is shown that, in general, the electrostatic potential need not be finite valued at infinity for 2D problems. Numerical examples for the 2D case are constructed to show that the formulations are consistent. Criteria for choosing the most appropriate formulation for a given problem are suggested.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640110808
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  • 8
    Electronic Resource
    Electronic Resource
    Vectorial and parallel processing in stress analysis with the boundary element method (1991)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 31 (1991), S. 307-317 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620310207
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  • 9
    Electronic Resource
    Electronic Resource
    Improved boundary-integral equation method for time-dependent inelastic deformation in metals (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 97-111 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Efficient solution of boundary value problems for time-dependent inelastic deformation in metallic structures is of great practical importance. These problems are generally solved by finite element methods and separate descriptions for time-independent plasticity and time-dependent creep are normally used. The boundary-integral equation method was recently applied for the first time to such problems. This paper presents a very efficient numerical implementation of the method with a linear description of the relevant variables over each boundary element and a newly developed Euler-type time-integration scheme with automatic time-step control for time integration. Numerical results for plates in plane stress with and without cutouts, under different loading histories, are presented. A combined creep-plasticity constitutive theory with state variables is used to model material behaviour. The results are more accurate and are obtained with much less computational effort compared to a previous attempt with an uniform description of variables over each boundary element and a predictor-corrector scheme for time integration. The computer program developed is quite general and can handle plane stress problems for plates of arbitrary shapes subjected to arbitrary time-histories of loadings. The numerical results presented in the paper are for certain illustrative problems.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150109
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of boundary element and finite element methods in the inelastic torsion of prismatic shafts (1981)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 17 (1981), S. 1576-1588 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The accuracy and computational efficiency of the boundary element and the finite element methods are compared in this paper for problems of time-dependent inelastic torsion of prismatic shafts. Several cross-sections and two types of twisting history are considered in the numerical examples. The shaft material is assumed to obey an elastic-time hardening creep constitutive model.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620171011
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