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  • 1990-1994  (725)
  • 1965-1969
  • 1992  (725)
  • Engineering General  (725)
  • 1
    Electronic Resource
    Electronic Resource
    Analytical elements of time domain bem for two-dimensional scalar wave problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1737-1754 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An accurate and efficient time domain BEM for 2-D scalar wave problems is presented. Emphasis is on developing analytical boundary elements (explicit solutions of the element matrices). The solutions are obtained under the condition of straight line elements and by bringing the problem to a simple and genral form of double convolution equation which is then solved by the Cagniard-De Hoop method. Six kinds of elements for any combination of the spatial interpolation functions of order 0, 1, 2 with the temporal interpolation functions of order 0, 1 are given in a compact form. It is pointed out that if the order of temporal interpolation function is higher than 1, or if the continuity of velocity or acceleration is required, the time-stepping technique will face difficulty. A method to solve this problem is also presented.Advantages of using the analytical elements instead of a numerical integral procedure are apparent. Problems with such things as singular integrals, accuracy and stability are solved. Methodology and solutions are demonstrated by a comparative study of two example problems. Numerical solutions reveal that the computation is efficient, accurate and stable.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330812
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  • 2
    Electronic Resource
    Electronic Resource
    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1771-1773 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330814
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  • 3
    Electronic Resource
    Electronic Resource
    Using domain decomposition to solve symmetric, positive-definite systems on the hypercube computer (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1941-1954 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A distributed method of solving sparse, positive-definite systems of equations, like those arising from many finite-element problems, on a hypercube computer is studied. A domain-decomposition method is introduced wherein the domain of the problem to be solved is physically split into several subdomains. Each of these subdomains is then distributed to a separate processor on the hypercube where the fill, factorization and solution of the system of equations proceeds. This physical split is based on a nodal ordering known as one-way dissection.4The method is applied to two-dimensional electrostatic problems which are governed by Laplace's equation. Since the finite-element method is used to discretize the problem, the algorithm is developed to take full advantage of the inherent sparsity in the system of equations by using an envelope storage scheme. The method is applied to several geometries, and results as well as performance data for the algorithm will be given.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330911
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  • 4
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620331001
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  • 5
    Electronic Resource
    Electronic Resource
    A finite element for variable order singularities based on the displacement formulation (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1955-1974 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An element for analysis of variable order one point singularities in plane problems has been proposed. The element meets all the convergence requirements, viz. the rigid body mode, the constant strain condition and the interelement compatibility. It can be easily incorporated in any package based on the displacement formulation. Four examples from fracture mechanics are presented to demonstrate its performance. The examples involve mechanical or thermal loadings. The accuracy of results in all the examples is very good.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330912
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  • 6
    Electronic Resource
    Electronic Resource
    Unconditionally convergent partitioned solution procedure for dynamic coupled mechanical systems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1975-1996 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new partitioned solution procedure for the direct time integration of second order coupled-field systems is presented and it is applied to the problem of soil-pore fluid interaction. The necessary convergence analysis for the iterative method is carried out and the fulfilment of the convergence condition is achieved with the introduction of two suitable auxiliary matrices in the basic equations governing the dynamic phenomena. Numerical examples are presented to demonstrate the effectiveness and the versatility of the proposed solution procedure.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330913
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of parameter estimation heat conduction problems with phase change using the finite element method (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 2015-2037 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A solution to a parameter estimation problem in heat conduction with phase change is presented. Specifically, the thermophysical properties of the material are estimated by using the temperature measurements of several sensors located inside the fixed domain.In the parameter estimation problem the error is minimized between given and modelled temperatures at sensor locations over the time interval where the experiment involved variation of the material parameters. The methods are illustrated with several examples. The effects on the solution of the locations of the sensors, the number of the sensors, the time step and the number of time steps are examined.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620331003
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  • 8
    Electronic Resource
    Electronic Resource
    A three-dimensional BEM solution for plasticity using regression interpolation within the plastic field (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1997-2014 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents an improved solution of three-dimensional plasticity problems using the boundary element method (BEM). The BEM formulation for plasticity requires volume as well as boundary discretizations. An initial stress formulation is used to satisfy the material non-linearity. Conventionally, the plastic field in the volume element (or cell) is interpolated based on the value of plastic stress at the nodes of the cell. In this paper, the distribution of the plastic field in the cell is based on a number of points interior to the cell. The plastic field is described using regression interpolation polynomials through these interior points. The constitutive relation is satisfied at each interior point. The number of points can be varied in each cell, thus allowing for adaptive volume cells. The plastic stresses are computed at the interior points only, therefore, the need for surface stress computation (which uses numerical derivatives at the surface) is completely eliminated. Three-dimensional applications are used to compare the present regression interpolation procedure with the conventional method for elasto-plasticity problems. In all variations of the applications studied regression interpolation based on interior points provided superior results to those determined via the conventional nodal interpolation method.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620331002
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  • 9
    Electronic Resource
    Electronic Resource
    An inverse method for determining elastic material properties and a material interface (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 2039-2057 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical procedure which integrates optimization, finite element analysis and automatic finite element mesh generation is developed for solving a two-dimensional inverse/parameter estimation problem in solid mechanics. The problem consists of determining the location and size of a circular inclusion in a finite matrix and the elastic material properties of the inclusion and the matrix. Traction and displacement boundary conditions sufficient for solving a direct problem are applied to the boundary of the domain. In addition, displacements are measured at discrete points on the part of the boundary where the tractions are prescribed. The inverse problem is solved using a modified Levenberg-Marquardt method to match the measured displacements to a finite element model solution which depends on the unknown parameters. Numerical experiments are presented to show how different factors in the problem and the solution procedure influence the accuracy of the estimated parameters.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620331004
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  • 10
    Electronic Resource
    Electronic Resource
    Postbuckling analysis of layered composites using p- version finite strips (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 2091-2107 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents the results of a study on the buckling and postbuckling analyses of layered shear-deformable composite plates using p-version finite strips. The plates are considered to be sufficiently long so that the effect of boundary conditions along the shorter edges is of little significance; this makes it possible to use the ‘exact’ trigonometric functions in the longitudinal direction. The displacement field in the transverse direction is discretized by p-version finite strips and convergence is studied by p-extension, i.e. keeping the number of strips relatively small whilst increasing the polynomial order till convergence of the buckling load or the postbuckling stiffness is achieved.Detailed convergence studies are presented and comparison with results of earlier investigations are shown wherever appropriate. The results demonstrate the superior convergence characteristics of the p-version approach.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620331007
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  • 11
    Electronic Resource
    Electronic Resource
    A simple class of finite elements for plate and shell problems. I: Elements for beams and thin flat plates (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 955-977 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This 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.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350502
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  • 12
    Electronic Resource
    Electronic Resource
    Numerical simulation of the separated fluid flows at large Reynolds numbers (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 469-472 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The variety of flow regimes (steady separated, periodically separated-‘Karman vortex street’, unsteady turbulent) and their characteristic peculiarities (separation and reattachment points, secondary separation, boundary layer, instability of the shear mixing layer, etc.) require the construction of effective numerical methods, which will be able to simulate adequately the considered flows.MERANGE ≡ SMIF-a splitting method for physical factors of incompressible fluids1-is used for calculations of the steady and unsteady fluid flows past a circular cylinder in a wide range of Reynolds numbers (10° 〈 Re 〈 lo6). The finite-difference scheme for this method is of second order accuracy in the space variables, has minimal numerical viscosity and is also monotonic. Use of the Navier-Stokes equations with the corresponding transformation of Cartesian co-ordinates allows the calculations to be made by one algorithm both in a boundary layer and out of it. The method allows calculations at Re = ∞ cc and simulation of d‘Alembert’s paradox. Some results on the classical problem of the flow around a circular cylinder for a wide range of Reynolds numbers are discussed. The crisis of the total drag coefficient and the sharp rise of the Strouhal number are simulated numerically (without any turbulence models) for the critical Reynolds numbers (Re ≈ 4 × 105), and are in a good agreement with experimental data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620340206
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  • 13
    Electronic Resource
    Electronic Resource
    Navier-Stokes simulation of flow through a highly contoured subsonic diffuser (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 473-483 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The flow through a highly offset subsonic diffuser with cross-sectional profiles that varied from rectangular at the duct entrance to circular a t the engine face was numerically simulated. A multizonal approach combined with a two-grid topology was used to represent both the internal and external flow fields, and an implicit, approximately-factored, partially flux-split finite-difference algorithm was used to solve the three-dimensional thin-layer Navier-Stokes equations. The computed static pressures along the inlet wall and total pressures on the engine face were compared with experimental data. In addition, the overall flow field within the duct was examined in detail. Good agreement is shown between experiment and computations, with the limiting factor being the lack of a reliable turbulence model for internal flow problems.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620340207
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  • 14
    Electronic Resource
    Electronic Resource
    Non-linear finite strip analysis of rectangular laminates under end shortening, using classical plate theory (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1087-1110 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The finite strip method is developed for predicting the geometrically non-linear response of rectangular composite laminates with simply supported ends when subjected to uniform end shortening in their plane. At the loaded ends lateral in-plane expansion may be allowed freely or may be prevented completely in different versions of the approach. The permitted laminate material properties are quite general, encompassing anisotropy and full coupling between in-plane and out-of-plane behaviour. The analysis is based on the use of the classical plate theory and the non-linearity is introduced in the strain-displacement equations in the manner of the von Karman assumptions. Three different types of finite strip are presented with either linear, quadratic or cubic interpolation of the membrane displacement components across a strip: in each case the bending displacement component varies cubically across a strip. Results are presented for isotropic plates and for unsymmetric cross-ply, angle-ply and arbitrary laminates.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350510
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  • 15
    Electronic Resource
    Electronic Resource
    A finite element method for the probabilistic creep of solids (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1171-1182 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350603
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  • 16
    Electronic Resource
    Electronic Resource
    Localized collapse of shells of revolution using a local-global strategy (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1153-1170 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The mode of collapse in many metallic shells is, oftentimes, one of localized collapse, wherein severe plastic deformation and high displacement gradients are localized within some region. The combined material and geometric non-linearity emanating from this local region is the predominant cause of instability in shells of revolution. In such a situation a local-global strategy is very useful for an efficient analysis. This strategy consists of employing two dimensional degenerated isoparametric shell elements with non-linear capability in a well defined 'local' zone where all the non-linearities are expected to be localized and which also contains some form of local deviation from axisymmetry such as a circumferential imperfection, cutouts, cracks, etc. Linear elastic ring type elements are employed in the remaining axisymmetric zone and the two zones are linked through a transformation between the degrees of freedom involved. The solution of the non-linear problem is achieved by appropriate condensation procedures to reduce the number of active degrees of freedom and the load incrementation is achieved by the well known 'arc length' iterative procedure. Numerical exampies are presented to demonstrate that this strategy is very efficient and accurate for problems with well defined non-linear local zones. The capability of this strategy for treating problems with local material discontinuities such as cracks, cutouts, etc. as an efficient alternative to a complete two dimensional discretization is pointed out.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350602
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  • 17
    Electronic Resource
    Electronic Resource
    Computational model for 3-D contact problems with friction based on the penalty method (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1289-1309 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A 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.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350609
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  • 18
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    Authors' reply (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1348-1349 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350613
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  • 19
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    A finite element method for domains with corners (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1329-1345 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A 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.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350611
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  • 20
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    Finite element asymptotic analysis of slender elastic structures: A simple approach (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1397-1426 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An asymptotic method directly derived from Koiter's theory and suitable for the solution of elastic buckling problems and its natural adaptation to a numerical solution by means of a finite element technique are presented here. The order of the extrapolation of the equilibrium equations has been intentionally kept very low because attention has been entirely devoted to all those features (theoretical definitions, eigenproblem numerical techniques, suitable FEM implementation) which make such an approach competitive with respect to the classic step-by-step methods. For plane frames and 3D pin-jointed trusses, the performances of the algorithm (numerical accuracy and computational cost) are compared with those of Riks' are-length method.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350703
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  • 21
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    A method for direct evaluation of singular integral in direct boundary element method (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1473-1485 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new method is presented for evaluating the Cauchy principal value integral and the free term in the three-dimensional elastic boundary element method. This method expresses the singular integral as the sum of a weakly singular integral and an integrable Cauchy principal value integral. The former can be computed by means of the usual standard Gaussian quadrature after a transformation suggested by Lachat and Watson,10 who correctly limited its use only to weakly singular integral. The latter can be calculated by direct integration in the Cauchy principal value sense. This paper also points out some limitations in the use of triangle polar co-ordinate suggested by Li et al.11 and later extended by Zhang and Xu.16 The general expression of the free term for a boundary point with arbitrary characteristic surface is also presented. Simple numerical examples which verify the efficiency and accuracy of the present method are given.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350706
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  • 22
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1925-1926 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350913
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  • 23
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351001
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  • 24
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    Three-dimensional fracture simulation with a single-domain, direct boundary element formulationThe implementation of this work was performed at the Program of Computer Graphics, Cornell University. The first author acknowledges the support of CNPq., a Brazilian Government agency, during his graduate studies at Cornell University. Thes research was sponsored by the IBM Bergen Scientific Centre, the National Science Foundation, NSF Grant No. 8351914, and the Applied Mathematical Sciences Research Program, Office of Energy Research, U.S. Department of Energy under contract DE-AC05-84OR214000 with the Martin Marietta Energy Systems, Inc. The authors gratefully acknowledge the assistance of Dr. E. D. Lutz, and wish to thank Professor T. A. Cruse for providing a copy of Reference [23] before publication. (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1907-1921 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An efficient hypersingular boundary integral equation method for three-dimensional fracture mechanics was presented in a previous paper. The details of the numerical implementation of this method are further discussed herein. In particular, an algorithm for achieving the required differentiability of the crack surface displacement function is discussed. To illustrate the utility of the method, computational results for several strongly interacting multiple-crack geometries are presented. The calculated stress intensity factors are in excellent agreement with those obtained by an approximate analytical method due to Kachanov and Laures.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350911
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    Adaptive finite difference methods for liquid membranes (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 823-836 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A domain-adaptive technique and an iterative, block bidiagonal method are used to analyse the unsteady dynamics of annular liquid membranes subject to fluctuations in the mass injected into the volume enclosed by the membranes. The domain-adaptive technique maps the unknown, time-dependent, curvilinear geometry of the liquid membrane into a unit interval. The condition that the membrane's radius is zero at the convergence point is used to determine the convergence length, which is governed by an ordinary differential equation. This equation is solved iteratively together with those which govern the fluid dynamics equations. A block bidiagonal technique is used to determine the mass per unit length, radius, and axial and radial velocity components of the membrane. It is shown that the pressure of the gases enclosed by the liquid membrane responds instantaneously to changes in and exhibits the same periodic behaviour as the mass injection rate. The convergence length takes a delay time to respond to the mass injection rate fluctuations. The magnitude of this delay time increases as the Froude and Weber numbers and the nozzle exit angle are increased. The amplitude of the oscillations of both the convergence length and the pressure coefficient increases as the pressure difference across the membrane and the amplitude of the mass injection rate fluctuations are increased.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340309
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    Multicriteria optimization of pin-jointed structures with overall stability constraints (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 893-900 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The optimization problem of elastic pin-jointed structures for overall stability conditions is presented in this paper. Two optimality criteria, the minimum of volume and the maximum of critical load, are taken into account. The optimization problem is presented as a non-linear multicriteria mathematical programming problem.Dimensional analysis enables natural division of the problem into two stages: optimization in space of non-dimensional variables with following specification of final dimensions.The sensitivity analysis and incremental solution scheme are used for the discription and solution of the optimization problem. Two sets of examples illustrate given models and a compromise solution. In the first sample of problems the optimization of the cross-sectional areas of the structure is considered while shape optimization is given in the second sample. Mathematical models of both examples are illustrated by numerical results. The shape optimization problem is characterized by a multiplicity of buckling modes and leads to complicated non-convex mathematical programming problems. Given examples are representative of complexities associated with practical problems.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340314
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    Numerical investigation of element-wise a posteriori error estimation in two and three dimensional elastic problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 969-977 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620340319
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    a posteriori Error estimation for triangular and tetrahedral quadratic elements using interior residuals (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 979-996 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A reliable and accurate a posteriori error estimator for quadratic triangular and tetrahedral elements is presented. Its application in an automated, adaptive finite element modelling system for elasticity problems demonstrates its ability to accurately estimate the error in the energy norm. A local version of this error estimator is also used to determine the multiple level h-refinement necessary to improve the finite element mesh.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340320
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    Design sensitivity coefficients for elasto-viscoplastic problems by boundary element methods (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 947-966 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with accurate and efficient determination of design sensitivity coefficients (DSCs) for solid mechanics problems with small strains and rotations, but with material non-linearities present (elasto-plastic or elasto-viscoplastic problems). This approach is based on direct differentiation (DDA) of the relevant derivative boundary element method (DBEM) formulation of the problem. Analytical differentiation of the DBEM equations leads to singular integral equations for the DSCs with weakly (logarithmically for 2-D) singular kernels which are easy to deal with. Also, stress components and their sensitivities are obtained on the boundary of a body with great accuracy. These quantities are typically difficult to obtain accurately from finite element methods (FEM).A computer program for general two-dimensional (plane strain and plane stress) problems has been developed based on the above formulation. Numerical results are presented for some sample problems and these are compared against direct solutions. The agreement between the DBEM and direct solutions is excellent for these examples.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340318
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    Supporting design decisions by Prolog database (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 941-946 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The 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.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340317
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    Optimal structural design with damping constraint limitations (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 21-35 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The algorithm optimization presented uses the optimality criteria method so as to minimize the total weight of the structure in the presence of a constraint of the damping type. The goal of this study is to increase the structural damping by optimizing the viscoelastic and elastic material distribution over the structure. The types of damping considered are hysteristic. The gradient of the constraint function in relation to the design variables is calculated with the aid of a complex variable sensitivity method. Several numerical results are presented to validate the algorithm proposed.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350103
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    A stabilized 9-node non-linear shell element (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 37-61 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A non-linear 9-node stress resultant shell finite element with six degrees of freedom per node is formulated. The material non-linearity is based on an implicit integration scheme using the von Mises yield criterion and linear isotropic bardening. The small strain geometric non-linearity is formulated using the polar decomposition theorem of continuum mechanics via a corotational updated Lagrangian method, which represents finite rotations with accuracy. Reduced integration is used to remove locking and calculate the stresses at their optimal stress accuracy points. A practical procedure is employed to stabilize the troublesome spurious zero energy modes. A number of tests covering the non-linear material and geometry ranges and buckling show the good performance of the new element.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350104
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    Genuinely resultant shell finite elements accounting for geometric and material non-linearity (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 63-94 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A general theoretical framework is presented for the fully non-linear analysis of shells by the finite element method. The governing equations are derived exclusively in terms of resulting quantities through a logical and straightforward descent from three-dimensional continuum mechanics without appealing to simplifying assumptions (hence the name genuinely resultant). As a result, the underlying theory is statically and geometrically exact, and it naturally includes small strain and finite strain problems of thin as well as thick shells. The underlying mathematical structure and the variational formulation of the theory are examined. This appears to be crucial for the development of computational procedures employing the Newton-Kantorovich linearization process and the Galerkin type discretization method. The treatment of finite rotations through an arbitrary parametrization of the rotation group and the interpolation procedure of SO(3)-valued functions underlying the construction of finite element basis are other issues studied in this paper. A numerical analysis is presented in order to assess the effectiveness of the proposed formulation. Small strain problems as well as finite strain deformation of rubber-like shells undergoing finite rotations are considered. Special attention is devoted to the assessment of the relevance of the drilling degree-of-freedom and highly non-uniform through-the-thickness deformation in the case of shells made of incompressible material.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350105
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    Shape functions and integration formulas for three-dimensional finite element analysis (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 95-108 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Shape functions and numerical integration formulas for three-dimensional finite element analysis as found in most finite element reference books are incomplete. For example, shape functions and integration formulas for a pyramid with a quadrilateral base are missing. It is also difficult to find symmetric higher-order integration formulas for triangular and tetrahedral elements. In general, these shape functions and integration formulas cannot be satisfactorily derived as degenerate cases of shape functions and integration formulas for hexahedral (brick) elements. In this paper we present C°-continuous quadrilateral pyramid elements and integration formulas for two- and three-dimensional elements.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350106
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    Design and Optimization of airfoils in non-stalling incompressible flow with a prescribed range of the angle of attack (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 121-132 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple and reliable method of aerodynamic design of airfoils is proposed for a given range of the angle of attack. The method is based on the solution of a new inverse boundary-value problem of aerohydrodynamics. In the problem the initial velocity distributions are given along the contour of the required airfoil as a function of the are co-ordinate for extreme values of the angle of attack from a fixed range. We justify a method of choice of these distributions which guarantees a non-stalling flow around the airfoil. The problem of airfoil optimization is also considered. Results of numerical calculations are presented.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350108
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    Elastostatic analysis of infinite solids using finite elements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 109-120 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A novel technique is developed to simulate the effects of an infinite elastic solid by using multiple springs having spatially varying stiffnesses. The spring constants are computed by numerical integration of classical solutions for point or line loads in an infinite or semi-infinite elastic mass. Under certain conditions, even the 'exact' values of spring constants may become negative at some nodes. A simple and highly effective algorithm is proposed to remove this computational difficulty. The technique is applied to the computation of displacements and stresses around underground openings. For a circular opening subjected to different stress conditions, spring constants computed by the proposed numerical integration technique are found to be 'identical' to their 'exact' values. Results obtained by the proposed technique for displacements and stresses around circular and non-circular openings are found to be in an excellent agreement with classical and boundary element solutions. The principal advantages of the proposed technique are that an unbounded solid may be simulated by a relatively very small finite model and a standard finite element code requires no modification for its implementation.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350107
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    A finite element formulation of the large sliding contact (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 133-143 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element formulation for the large sliding contact problem is discussed. With respect to a set of two material points the free and contacting state are distinguished. Because of the possibly occurring large slidings, the two points contact conditions are transformed to contact conditions with respect to larger sets of points, the so-called contact units. An incremental solution strategy is presented which calculates the equilibrium solution that obeys these contact conditions using an iterative procedure. Part of this strategy is the identification of actual sets of contacting material points. The performance of the algorithm is demonstrated by some case-studies.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350109
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    Fracture mechanics weight functions in three dimensions: Subtraction of fundamental fields (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 179-202 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new procedure is presented for the determination of the fracture mechanics weight functions that are required for the evaluation of stress intensity factors in cracked solids. The procedure can be used with a standard three-dimensional boundary element code. The weight functions are proportional to the displacements on the boundary of the solid when the only loading is a pair of self-equilibrated point forces at the crack front. In previous work, the highly singular crack-tip fields that this loading produces have been modelled by replacing the crack front by a cylindrical cavity with appropriate displacement boundary conditions on the cavity walls. It is shown here that results are dependent on the cavity radius and that convergence of the results cannot be guaranteed.An alternative procedure, based on the substraction of fundamental fields (SFF), is demonstrated herein. The high-order singularities are removed from the field before the reduced problem is solved numerically using a standard boundary element method. Since the reduced problem is equivalent to an unloaded crack in a solìd subjected to boundary tractions, the usual quarter-point displacement elements and quarter-point traction singular elements can be used to improve the accuracy. Weight functions, so obtained, are used to evaluate stress intensity factors as a function of position on the crack front for a straight-fronted crack in a rectangular bar subjected to various loadings. Both edge and central cracks are considered and the validity of the technique is demonstrated by comparing the results with previously published values.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350112
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    Creep deformation structural analysis using an efficient numerical algorithm (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1427-1442 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a fast numerical algorithm for the implementation of material models for creep into finite element codes. First, an overview of existing algorithms for transient and steady-state creep is given. Next, a new formulation is presented which reduces the constitutive integration to the solution of a scalar non-linear algebraic equation. A solution is shown to exist without the need for subincrementation. Details of the numerical algorithm are then discussed. The paper closes with several numerical examples which illustrate the speed, robustness and accuracy of the proposed procedure as implemented in the Lawrence Livermore National Laboratory finite element codes NIKE2D and NIKE3D.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350704
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    How to recognize the order of infinitesimal mechanisms: A numerical approach (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1351-1395 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Structures presenting kinematical inderterminacy are usually called mechanisms. This paper is entirely concerned with assemblies which reveal themselves to be mechanisms at a null value of the load. Among them a first distinction is made between infinitesimal and finite ones, the former being characterized by one or several directions of lower (but not zero) stiffness, whereas the latter show at least one finite admissible displacement for which none of the bars undergoes any elongation. Moreover, there exists the possibility to make a further distinction among the infinitesimal mechanisms, according to which is the order of the stiffness along the direction considered above. The way of evaluating this order is to perform a local analysis of the strain energy of the assembly, once the displacement field is parametrized in terms of a suitable parameter. By means of a finite element technique, this analysis can be easily performed through the numerical approach presented in this report.
    Additional Material: 25 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350702
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    Solutions to shape and topology eigenvalue optimization problems using a homogenization method (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1487-1502 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A 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.
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    URL: http://dx.doi.org/10.1002/nme.1620350707
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    Announcements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1541-1542 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350710
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    An explicit unconditionally stable variable time-step method for one-dimensional stefan problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1503-1520 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Modelling of heat conduction processes with phase changes benefits from the application of variable time-step methods when the behaviour of the moving boundary is not known a prioiri. Due to convergence and stability constraints only implicit difference equations have been used with these methods. Implicit methods show a significant loss of accuracy and exhibit convergence difficulties when used for relatively slow or rapid moving-boundary problems. To overcome these problems an improved explicit variable time-step method which combines the explicit exponential difference equation and a variable time-step grid network with virtual subspace increments around the moving boundary is presented and tested for both a solidification and a melting problem. A virtual subinterval time-step elimination technique is incorporated to ensure that stability is automatically maintained for any mesh size. Unlike the implicit variable time-step methods, the accuracy of the resulting method is not affected by the velocity of the moving boundary. For both test problems numerical results are in better agreement with known analytical solutions than results predicted by other numerical methods.
    Additional Material: 6 Ill.
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    Preface (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. iii 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350402
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    A note on the grid movement induced by MFEThis work has been carried out in connection with a joint CWI/Shell project on 'Adaptive Grids'. For this project Paul Zegeling has received support from the 'Netherlands Foundation for the Technical Sciences' (STW) (Contract No. CWI 59.0922) (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 623-636 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Moving-grid methods in one space dimension have become popular for solving several kinds of parabolic and hyperbolic partial differential equations (PDEs) involving fine scale structures such as steep moving fronts and emerging steep layers, pulses, shocks, etc. In two space dimensions, however, application of moving-grid methods is less trivial than in 1D. For some methods, e.g. those based on equidistributing principles, it is not even clear how to extend the underlying grid selection procedure to 2D. The moving-finite-element (MFE) method does not suffer from this drawback; its mathematical extension to 2D is trivial. However, because of the intrinsic coupling between the discretization of the PDE and the grid selection, the application of MFE, as for any other method, is not without difficulties. In this paper we describe the node movement induced by MFE for various PDEs and we indicate some problems concerning the grid structure that can result from this movement.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350312
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    Use of ‘simple solutions’ for boundary integral methods in elasticity and fracture analysis (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1737-1751 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The '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.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350902
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    Seismic response analysis of alluvial valley with two dipping layers by a boundary element-finite element coupling method (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1753-1769 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A coupling process of time-domain boundary element method and finite element method is constituted for analysis of the dynamic response of an alluvial valley. Since the characteristics of these two methods are different from each other, the time increment of the boundary element method is set to be an integer multiple of the finite element method, and a combination of a linear interpolation of boundary element equations at two successive time steps with a finite element equation is proposed. Using this procedure, responses of alluvial valleys with two dipping layers are analysed for a vertically incident SV wave, and influence of the lower layer on these responses is investigated. It is found that the presence of the additional lower layer affects not only the reflected waves but also the surface waves. Furthermore, when an outcropping lower layer exists at the basin edges, the valley suffers an amplification of motion and an extreme increase in strains. These results show that a small difference in the layer at the basin edge is significant in analysing dynamic responses of an alluvial valley.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350903
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    Boundary element analysis of thin plates internally bounded by rigid patches (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1771-1785 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Procedures are described for modelling a structural system consisting of thin Kirchhoff plates with internal patch areas capable of displacing as rigid flat surfaces. The physical prototype for these patches could be interconnection points for one-dimensional frame type elements of various shapes and layout, rigidly connected at these finite size 'joints' in the plate. The numerical procedure for modelling the thin plate is the Direct Boundary Element Method (DBEM) and a simple overview of this procedure is provided. Potential trouble spots, of which the user should be aware, are described.The paper will be of interest to structural engineers for analysis of frames having both plate and simple frame elements, for example, building frames; and also to researchers seeking the greater detail that this refined procedure can provide. As a practical tool, the methods described are computationally competitive with existing procedures, including the more rugged approaches used by building structural engineers for dynamic and torsional analysis.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350904
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  • 49
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    Implementation of mixed time integration techniques on a vectorized computer with shared memory (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1803-1828 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The implementation of subcycling in an explicit finite element program executed on a concurrent computer with shared memory is described. The effects of vectorization and parallelization on the speed-up and efficiency achieved with subcycling is discussed. Numerical studies are presented to illustrate the effects of the number of processors, the size of element blocks and problem size. Finally, an efficient allocation algorithm which minimizes the effects of processor idleness is presented.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350906
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    Polynomial particular solutions based boundary element analysis of acoustic eigenfrequency problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1787-1802 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The 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.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350905
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    A consistent co-rotational formulation for shells using the constant stress/constant moment triangle (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1829-1847 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The 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.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350907
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    Announcements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1923-1924 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: No Abstracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350912
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    Thermoelastic stability of trusses with temperature-dependent constitutive relations (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1891-1906 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with stability problems of spatial trusses due to thermal and mechanical loading. A fully coupled thermomechanical truss element is formulated which accounts also for the temperature dependence of the constitutive parameters. The formulation leads to a non-linear problem which is solved by the finite element method. The computation of critical points is based on the linearization of the coupled weak form which yields a non-symmetric tangent operator. The formulation and its associated algorithmic treatment is validated by means of examples.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350910
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    Three-dimensional 8-node and 20-node refined hybrid isoparametric elements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1871-1889 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper a new hybrid variational principle with independent variables of strain, stress and displacement and with a weaker constraint condition of interelement continuity is proposed. Based on this functional, a general formulation of a refined hybrid isoparametric element method has been established by the orthogonal approach.The present formulation is a rational approach to be adopted for deriving high-performance three-dimensional hybrid isoparametric elements even up to the higher-order 20-node element.Several numerical examples are presented to show that the present elements RGH8(8-node) and RGH20(20-node) have high accuracy, excellent computational efficiency and less sensitivity to mesh distortion.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350909
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  • 55
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350501
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 951-953 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350419
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620340201
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    Strain localization in multipotential elastoplasticity (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 349-363 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Conditions 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.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340121
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    A non-linearly stable implicit finite element algorithm for hypersonic aerodynamics (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 419-441 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A generalized curvilinear co-ordinate Taylor weak statement implicit finite element algorithm is developed for the two-dimensional and axisymmetric compressible Navier-Stokes equations for ideal and reacting gases. For accurate hypersonic simulation, air is modelled as a mixture of five perfect gases, i.e. molecular and atomic oxygen and nirogen as well as nitric oxide. The associated pressure is then determined via Newton solution of the classical chemical equilibrium equation system. The directional semi-discretization is achieved using an optimal metric data Galerkin finite element weak statement, on a developed ‘companion conservation law system’, permitting classical test and trial space definitions. Utilizing an implicit Runge-Kutta scheme, the terminal algorithm is then non-linearly stable, and second-order accurate in space and time on arbitrary curvilinear co-ordinates. Subsequently, a matrix tensor product factorization procedure permits an efficient numerical linear algebra handling for large Courant numbers. For ideal- and real-gas hypersonic flows, the algorithm generates essentially non-oscillatory numerical solutions in the presence of strong detached shocks and boundary layer inviscid flow interactions.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340203
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  • 60
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    Generation, optimization and adaptation of multiblock grids around complex configurations in computational fluid dynamics (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 443-454 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We present a method that has been developed for the construction of grids suitable for a large class of Computational Fluid Dynamics (CFD) solvers. Three independent steps are considered: a multidomain generation, an optimization and an adaptation. The first step handles the complexity of the three-dimensional domain to be meshed and is able to perform an algebraic construction of the grid points within a multidomain topology; any decomposition can be considered and analysed by the algorithm. The second step is able to optimize a mesh with respect to a quality measure defined in terms of cell deformation; a conjugate gradient algorithm drives the nodes up to an equilibrium position that realizes the minimum of a mesh energy quantity. The final step handles the physics of the problem and moves the nodes in order to refine the mesh where anything of interest takes place, while preserving its good metric quality. The three steps have been implemented independently and successfully, as shown by the examples presented.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340204
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    Time marching integral equation method for unsteady transonic flows around airfoils (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 455-467 
    Details
    ISSN: 0029-5981
    Keywords: transonic flow ; unsteady flow ; numerical method ; integral equation method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A time marching integral equation method has been proposed here which does not have the limitation of the time linearized integral equation method in that the latter method can not satisfactorily simulate the shock wave motions. Firstly, a model problem-one dimensional initial and boundary value wave problem is treated to clarify the basic idea of the new method. Then the method is implemented for two dimensional unsteady transonic flow problems. The introduction of the concept of a quasi-velocity-potential simplifies the time marching integral equations and the treatment of trailing vortex sheet condition. The numerical calculations show that the method is reasonable and reliable.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340205
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    Theory and finite element formulation of rubberlike membrane shells using principal stretches (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1111-1126 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A theory of rubberlike membrane shells undergoing large elastic deformations is derived. The stresses are deduced from Ogden's material law, which is formulated in terms of the principal values of the right stretch tensor. Incompressibility is fulfilled exactly using the plane stress constraint. Furthermore, a finite element formulation of the membrane theory is given. The use of the tangential stiffness matrix, derived analytically, provides a quadratically convergent solution process. Several numerical examples show the robustness of the developed finite element.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350511
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1151-1152 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350513
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  • 64
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    Transient natural convection from a horizontal cylinder confined between vertical walls - a finite element solution (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 621-635 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A general finite element computer code is developed for transient two dimensional natural convection heat transfer in a laminar regime. This code is used to study heat transfer from a horizontal isothermal cylinder confined between two vertical adiabatic walls. Results are presented for Ra = 1000, Pr = 0.7, and for different wall spacing to cylinder diameter ratios. The time variations of the local and average Nusselt numbers along with some transient and steady state velocity and temperature fields are demonstrated. The steady state results predict the existence of an optimum wall distance for the maximum average Nusselt number. The steady state and the transient Nusselt numbers are compared with the available experimental or theoretical results for a few cases. Their agreement is very good.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340214
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    On stable equal-order finite element formulations for incompressible flow problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 655-665 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this work we discuss stable equal-order finite element formulations for incompressible flow problems based on Petrov-Galerkin methods, constructed by adding to the classical Galerkin formulation least-squares of the governing equations. Continuous and discontinuous pressure interpolations are considered. Numerical results are presented reinforcing the numerical analysis.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340216
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    Some theoretical aspects in computational analysis of adhesive lap joints (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1237-1262 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is devoted to the numerical analysis of bidimensional bonded lap joints. For this purpose, the stress singularities occurring at the intersections of the adherend-adhesive interfaces with the free edges are first investigated and a method for computing both the order and the intensity factor of these singularities is described briefly. After that, a simplified model, in which the adhesive domain is reduced to a line, is derived by using an asymptotic expansion method. Then, assuming that the assembly debonding is produced by a macro-crack propagation in the adhesive, the associated energy release rate is computed. Finally, a homogenization technique is used in order to take into account a preliminary adhesive damage consisting of periodic micro-cracks. Some numerical results are presented.
    Additional Material: 21 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350606
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    Preconditioning techniques for non-symmetric matrices with application to temperature calculations of cooled concrete (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1311-1328 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Preconditioning 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.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350610
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    Announcement (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1350-1350 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350614
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    Letter to the editor (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1347-1348 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350612
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350701
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    A hybrid optimal synthesis method for truss structures considering shape, material and sizing variables (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 839-851 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A generalized hybrid optimal synthesis method is developed for truss structures in which the design variables are the co-ordinates of the panel points, cross-sectional areas and discrete material kinds of member elements. The primary design problem is formulated in terms of the shape, material and sizing variables and approximated to a sequence of convex and separable subproblems by using mixed direct/reciprocal design variables. Each subproblem is solved by a dual method in which the continuous shape and sizing variables are optimized by a Newton-type algorithm and the discrete material and continuous sizing variables are improved by a discrete sensitivity analysis. Using the proposed method, discrete material kinds, shape and sizing variables can be systematically improved to obtain an optimum solution. The rigourness, reliability and efficiency of the method are demonstrated by applying it to the minimum cost design of trusses subjected to stress and displacement constraints.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620340310
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    Effect of cross-sectional warping of anisotropic sandwich laminates due to dynamic loads using a refined theory and C° finite elements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2031-2047 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An 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.
    Additional Material: 10 Ill.
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    The modelling of aerodynamic flows by solution of the euler equations on mixed polyhedral grids (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2003-2029 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, an algorithm for obtaining solutions to the compressible Euler equations on mixed polyhedral grids is described. These grids, which are, in general, composed of hexahedral, pentahedral and tetrahedral elements, are used in the modelling of aerodynamic flows over complex three-dimensional geometries. The hexahedra are grouped into regular blocks, while the other elements are part of irregular grid regions, giving rise to the term “hybrid grid approach”. The interconnection of the grid elements is defined by an efficient data structure, which supplies the required information to drive the Euler algorithm. In fact, cell-vertex and cell-centre spatial discretization variants of this algorithm are detailed, along with an explicit time-marching scheme for obtaining steady-state solutions. Results on two geometrically simple configurations provide an evaluation of these solution techniques, whilst the focus on a third, complex configuration, demonstrates the potential of the method in addressing the flow over general aircraft geometries.
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620351006
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    Announcements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2101-2102 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351011
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2103-2104 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351012
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    Diffusion problems using transient discrete source superposition (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 165-178 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Discrete source superposition techniques seek sets of discrete, singular source strengths which satisfy the boundary conditions of a particular problem, and, necessarily, the governing differential equation. The sum of the fields produced by such sources thus provides an approximation to the required solution. In many respects these techniques are a special case of conventional boundary integral equation methods, where density distributions of smeared sources are sought. In this paper an attempt is made to extend the discrete source superposition technique to transient problems. The example addressed is the transient diffusion equation. The method developed does seem to have sòme promise. It is found that even coarse spatial discretization can yield quite accurate results, and that surprisingly large timesteps can be employed and accuracy maintained. Further, although no direct comparisons are made, the absence of spatial integrations indicates that the computational effort per timestep is likely to be less than for conventional BIE.
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    URL: http://dx.doi.org/10.1002/nme.1620350111
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    An adaptive h-refinement using transition element for plate bending problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 145-163 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An adaptive h-refinement procedure utilizing compatible 5- to 7-node quadrilateral transition elements together with 4-node elements is presented for Reissner-Mindlin plate bending problems. By introducing the transition elements which have physical midside nodes, some difficulties associated with imposing displacement constraints on irregular nodes to enforce interelement compatibility in common adaptive h-refinement on quadrilateral mesh are easily overcome. Numerical examples are presented to show the effectiveness of using the transition elements for the adaptive h-refinement.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350110
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    Newton-like methods with limited storage, for the solution of elasto-viscoplasticity problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 223-240 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Quasi-Newton and Secant-Newton methods have been successful in solving problems of elasto-plasticity. In this paper these methods are applied to elasto-viscoplastic analyses, in an algorithm coupling the global solution for displacement increments with local Newton-Raphson stress iteration at each sampling point. The familiar rank-two DFP and BFGS methods are generalized to the Broyden family of algorithms, and this generalization is also used to produce a Secant-Newton algorithm corresponding to Hoshino's method. Consideration is given to the most effective strategy when only a limited number of Quasi-Newton iterates may be stored; overwriting, re-start or continuation in Secant-Newton form. Results are presented for a tunnelling problem using both plane strain and axisymmetric formulations.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350202
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    The iterative solution of Taylor - Galerkin augmented mass matrix equations (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 241-253 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper investigates the convergence properties of iterative schemes for the solution of finite element mass matrix equations that arise through the application of a Taylor-Galerkin algorithm to solve instationary Navier-Stokes equations. This is a time-stepping algorithm that involves Galerkin mass matrix equations at fractional stages within each time-step. Plane Poiseuille flow and shear-driven cavity flow are selected as benchmark problems on which to investigate the effects of various choice of scheme and time-step dependency. The iterative convergence of each mass matrix equation for a single fractional stage is studied, both at the element and the system matrix level. The underlying theory is confirmed and it is shown how optimal iterative convergence rates may be achieved for a Jacobi scheme by employing an appropriate acceleration factor. Moreover, this factor is trivial to compute. The consequential effects on the convergence of the time-stepping procedure to reach steady-state are also considered where non-linear effects are present.
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    URL: http://dx.doi.org/10.1002/nme.1620350203
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    A galerkin symmetric boundary-element method in elasticity: Formulation and implementation (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 255-282 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Static discontinuities (i.e. distributions of forces along a line or a surface, implying a jump of tractions across it) and kinematic (displacement) discontinuities are considered simultaneously as sources acting on the unbounded elastic space Ω∞ along the boundary Γ of a homogeneous elastic body Ω embedded in Ω∞. The auxiliary elastic state thus generated in the body is associated with the actual elastic state by a Betti reciprocity equation. Using suitable discretizations of actual and fictitious boundary variables, a symmetric Galerkin formulation of the direct boundary element method is generated.The following topics are addressed: reciprocity relations among kernels with particular attention to the role of singularities; conditions to be satisfied by the boundary field modelling in order to achieve the symmetry of the coefficient matrix; variational properties of the solution.With reference to two-dimensional problems, a technique based on a complex-variable formalism is proposed to perform the double integrations involved in this approach. An implementation of this technique for elastic analysis is described assuming straight elements, with continuous linear displacements and piecewise-constant tractions; all the double integrations are carried out analytically.Comparisons, from the computational standpoint, with the traditional non-symmetric method based on collocation and single integration, demonstrate the effectiveness of the present approach.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350204
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    Hybrid trefftz plane elasticity elements with p -method capabilities (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1443-1472 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A family of p-method plane elasticity elements is derived based on the hybrid Trefftz formulation.1 Exact solutions of the Lamé-Navier equations are used for the intra-element displacement field together with an independent displacement frame function field along the element boundary. The final unknowns are the parameters of the frame function field consisting of the usual degrees of freedom at corner nodes and an optional number of hierarchic degrees of freedom associated with the mid-side nodes. Since the element matrices do not involve integration over the element area, the elements have a polygonal contour with an optional number of curved sides. The quadrilateral element has the same external appearance as the conventional p-method plane elasticity element.2,3 But unlike in the conventional p-method approach, suitable special-purpose Trefftz functions are generally used to handle the singularity and/or stress concentration problems rather than a local mesh refinement. The practical efficiency of the new elements is assessed through a series of examples.
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    URL: http://dx.doi.org/10.1002/nme.1620350705
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1543-1545 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350711
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 439-441 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350215
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    Seismic crack propagation analysis of concrete structures using boundary elements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1547-1564 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The time-domain boundary element method is applied to study the propagation of discrete cracks under dynamic loadings. The principles of linear elastic fracture mechanics are employed to accurately represent the stress singularity in front of the crack tip. A fracture criterion suitable for brittle materials is employed to determine the time and direction of the propagating crack. Discrete crack closure under dynamic loadings is modelled and the response of a 2-D cracked body is obtained by direct integration of the equations of motion. Results are presented for three test problems wherein the accuracy and usefulness of the proposed formulation is established through comparisons with available data. 'It is expected that this formulation can be used to study the seismic cracking of mass concrete structures such as gravity dams.
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    URL: http://dx.doi.org/10.1002/nme.1620350802
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    A general explicit or semi-explicit algorithm for compressible and incompressible flows (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 457-479 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This note presents a rational basis for a unified finite element algorithm capable of dealing with a wide range of fluid flow in both steady and transient cases. It is hoped that empiricism inherent in many previous approaches can be avoided and a sound basis provided. The algorithm permits the use of equal interpolation for all variables by avoiding the need for the Babuska-Brezzi constraints in regions where the flow is nearly incompressible.The success of the algorithm, which here is written for the non-conservative equation form, is demonstrated on several examples ranging from (nearly) incompressible through transonic regions to supersonic flows. Up to mild shocks such as those occurring in the examples presented in this paper, no 'artificial' viscosity is added at any stage.The algorithm extends some concepts introduced in an earlier paper.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350303
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    New variational formulations for minimal surfaces (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 491-502 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Using curvilinear co-ordinates of the surface, a functional is developed for the classical formulation for minimum surfaces and is then utilized to obtain a complementary formulation. Unlike the classical formulation in Cartesian co-ordinates, these two formulations are applicable to multi-valued surfaces and give upper and lower bounds to the exact solution when used in an approximate analysis, e.g. finite elements. By means of Lagrange multipliers, a constraint on enclosed volume is incorporated into the basic functional.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350305
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    Efficient and reliable accelerated constant stiffness algorithms for the solution of non-linear problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 481-490 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper relates to a secant-relation-based acceleration method used to improve the modified Newton-Raphson scheme in which the constant stiffness matrix formed at the first iteration step is adopted to make incremental predictions for all iteration steps. An accelerator defined by minimizing a certain globally defined system error is used to scale the incremental response vector obtained by the modified Newton-Raphson prediction in iteratively updating the response vector. The performance of acceleration is dependent on the method used to evaluate the system error. A consistent approach of evaluating the system error leads to obtaining a consistent accelerator. Another approach evaluates the system error less consistently, which results in obtaining a less consistent accelerator. Numerical results of non-linear finite element analyses will be presented to show the effectiveness of this approach and to demonstrate the conclusion made by theoretical investigation regarding the convergency performances of the two accelerators proposed.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350304
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    Gradient-dependent plasticity: Formulation and algorithmic aspects (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 521-539 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A plasticity theory is proposed in which the yield strength not only depends on an equivalent plastic strain measure (hardening parameter), but also on the Laplacian thereof. The consistency condition now results in a differential equation instead of an algebraic equation as in conventional plasticity. To properly solve the set of non-linear differential equations the plastic multiplier is discretized in addition to the usual discretization of the displacements. For appropriate boundary conditions this formulation can also be derived from a variational principle. Accordingly, the theory is complete.The addition of gradient terms becomes significant when modelling strain-softening solids. Classical models then result in loss of ellipticity of the governing set of partial differential equations. The addition of the gradient terms preserves ellipticity after the strain-softening regime has been entered. As a result, pathological mesh dependence as obtained in finite element computations with conventional continuum models is no longer encountered. This is demonstrated by some numerical simulations.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350307
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    Analysis and evaluation of singular integrals by the invariant imbedding approach (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 563-587 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The invariant imbedding formulae for evaluating singular integrals on flat domains are used to analyse the singular integrals which arise in the Boundary Element Method.Although all orders of singularity are considered, the primary objective of the paper is the evaluation of Cauchy principal value integrals (CPV). Conditions for boundedness of the CPV aré derived, and evaluation techniques are presented for situations in which the singular point lies on, or is in close proximity to, an element boundary. Specific cases analysed include straight and curved element boundaries, and corners. Other numerical aspects of the formulae are also discussed.By way of example, the analysis techniques are applied to the volume integrals which arise in continuum, inelastic problems.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350309
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    The C° structural finite elements reformulated (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 541-561 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new formulation was recently proposed by the present author aimed at removing the shear and membrane locking mechanisms from the C° structural elements. The performance achieved was shown to be excellent, completely eliminating all locking problems. In some cases of C° plate and shell element applications; however, the proposed formulation was shown to yield flexible (softer than expected) models. Analysis of this behaviour revealed the presence of an internal moment redistribution mechanism with the classical formulation. The absence of this mechanism from the new formulation was found to be responsible for the potential introduction of softening effects in the elastic finite element models. In the present paper, the internal moment redistribution effect is examined analytically and the key component responsible for its development is isolated. The new formulation, as originally proposed for the C° structural elements, is modified so that the internal moment redistribution mechanism is retained, yet, with all locking mechanisms being rejected. The proposed formulation has been subjected recently to extensive numerical investigation with excellent results.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620350308
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    Error estimators using global-local methods (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 589-599 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Error estimators were derived using global-local and refined global-local finite element methods and an extrapolation technique. The proposed error estimators are to be used in estimating the global error energy norm, local error energy norm and nodal displacement error. These error estimators were applied to three numerical examples. The results clearly demonstrated that these error estimators are of high quality.
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    URL: http://dx.doi.org/10.1002/nme.1620350310
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    Conjugate direction methods for helmholtz problems with complex-valued wavenumbers (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 601-622 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The convergence behaviour of conjugate direction methods for Helmholtz problems with complex-valued wavenumbers is studied. The model problem is a Galerkin discretization of the scalar Helmholtz equation on square arrays of 2D and 3D, C° linear elements. A series of controlled experiments is performed which use the dimensionless wavenumber and the algebraic size of the system of equations to completely characterize the iterative performance of the solvers. The effects of algebraic size are examined as functions of both mesh refinement and mesh extension within the limits of present-day workstation computing environments. A comparison is drawn between the conjugate direction methods investigated and the equivalent time-domain solution obtained through explicit time-stepping.
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    URL: http://dx.doi.org/10.1002/nme.1620350311
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    Announcement (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 637-637 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350313
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    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 638-639 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350314
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992) 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350401
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    Spacecraft thermal modelling (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 641-653 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Thermal modelling of spacecraft requires approaches which can handle dominant radiative heat transfers and many special thermal control components. Present network-type thermal analysers allow simulation, especially for components with rectangular geometries, but at the expense of considerable awkwardness and much error-prone manual input. The user interfaces for pre- and postprocessing for these analysers are also very deficient. Finite element thermal analysers solve some of the analytical difficulties, but are not widely used because they lack the flexibility to simulate special operations. The Galerkin finite element method (GFEM) distributes the contributions within an element to the element nodal points. The assembly of the contributions from all elements yields a systems of energy balance equations for the nodal points of the system. Monte Carlo raytracing, in conjunction with a GFEM energy distribution to element nodal points, yields a procedure of consistent non-isothermal surface radiation exchange. This procedure reduces a source of simulation error caused by non-uniform element illumination and shading. Orbital heating, fluid flow and special analysis features are discussed. The main analysis program is interfaced to the preprocessing and postprocessing modules. Example results are given.
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    A finite element model for the simulations of mould filling in metal casting and the associated heat transfer (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 787-806 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The flow associated with the pouring of molten metal into moulds has been modelled based upon certain simplfying assumptions. A finite element based Navier-Stokes equation solver has been used to analyse the flow. The velocities obtained from the Navier-Stokes equation solver are used to advect a pseudo-concentration function for modelling the free fluid front. A simple problem with a known analytical solution is solved first to test the model. Subsequently, several more examples of varied geometrical configuration are modelled to demonstrate the applicability of the proposed model. The Taylor-Galerkin method has been used to model the heat transfer during filling due to its advection dominated nature.
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    URL: http://dx.doi.org/10.1002/nme.1620350410
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    A new unconditionally stable fractional step method for non-linear coupled thermomechanical problemsResearch supported by NSF under GRANT No. 2-DJA-544 with Stanford University (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 737-766 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new class of time-stepping algorithms for strongly coupled thermomechanical problems is presented which retains the computational convenience of traditional staggered algorithms without upsetting the unconditional stability property characteristic of fully implicit (monolithic) schemes.This class of methods was first introduced by the authors (in the general context of thermoplasticity) in the USCM held at Chicago, July 1991, and in the IUTAM symposium held at Hannover, Germany, September 1991 The proposed schemes are fractional step methods associated with a two phase operator split of the full non-linear system of thermoelasticity into an adiabatic elastodynamics phase, followed by a heat conduction phase at fixed configuration. This operator split is shown to inherit the contractivity property of the full problem of evolution, thus leading to unconditionally B-stable product formula algorithms. In sharp contrast with this stability result, traditional staggered algorithms based on an isothermal mechanical phase followed by a heat conduction phase with an effective heat source are shown to lead, at best, to conditionally stable schemes. It is further shown that the actual implementation of these two classes of schemes is essentially identical. The numerical simulations presented include both dynamic and quasi-static problems and are shown to closely replicate the stability estimates and non-linear stability results derived for these two classes of staggered schemes.
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    URL: http://dx.doi.org/10.1002/nme.1620350408
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    Inverse stefan problem: Tracking of the interface position from measurements on the solid phase (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 835-851 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This study presents a sequential algorithm for the identification of the position s of the moving boundary of a variable one-dimensional or two-dimensional domain from discrete measurements, temperatures and fluxes, collected at the fixed boundary. The inverse problem is solved by minimization, with respect to s, of a penalized output least square criterion defined on a sliding time horizon of length τ. At every time step, several iterations are performed to estimate the unknown s. Each iteration consists in a guess of s, a computation of the corresponding value of the output y (direct model) and the criterion J, and a step towards a new estimation of s. The impact of the different parameters, space and time discretization intervals, regularization coefficient, dimension of the unknown parameter s, length of the observation horizon, choice of the observed output (temperature or flux) and choice of the direct model is thoroughly analysed for an analytical test case.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350412
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    Electronic Resource
    Electronic Resource
    Numerical simulation of forming processes using a coupled fluid flow and heat transfer model (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 807-833 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Numerical simulation of forming processes is studied using the Navier-Stokes equations and the energy equation governing viscous, incompressible fluids. A review of various important aspects of forming processes is also reviewed for completeness. A penalty finite element model of the equations is developed. The finite element model is used to study the effectiveness of various constitutive models developed for metal forming and polymer processing. The element-by-element (EBE) data structure with efficient iterative solution methods is used to solve the large systems of equations that arise in the analysis of complex 3-D problems. Numerical results for problems representative of various forming processes (e.g. extrusion and solidification) are presented.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350411
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