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  • Engineering  (33)
  • FLUID MECHANICS AND HEAT TRANSFER  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Effects of geometrical and material properties on the vertical vibration of three-dimensional foundations by BEM (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 14 (1990), S. 49-70 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The dynamic response of foundation is influenced by various mechanical properties of soil as well as the geometrical properties of the foundation. In this paper, the effects of Poisson's ratio and material damping, as well as the influences of aspect ratio and embedment depth on the dynamic stiffness of rectangular foundations are studied. Studies are also conducted to investigate the influence of the type of contact at the soil-foundation interface and the soil layer overlaying a half-space. These studies were conducted using an advanced algorithm of the boundary element method incorporating isoparameteric quadratic boundary elements. Higher-order elements (quadratic) were used since they can model the wavy nature of the dynamic problem accurately.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610140104
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  • 2
    Electronic Resource
    Electronic Resource
    Advanced elastic and inelastic three-dimensional analysis of gas turbine engine structures by BEM (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 393-411 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The boundary element method (BEM) has been known for some time to be extremely useful for the solution of elastic stress analysis problems involving high stress/strain gradients. In particular, the method has been extensively used for the study of both two and three-dimensional fracture mechanics problems. Recent analytical and numerical developments coupled with the general availability of greatly increased computing capacity have made both elastic and inelastic three-dimensional stress analysis feasible for complex geometries such as those found in gas turbine engine components.This paper summarizes the features of an advanced stress analysis method based on BEM for elastic and inelastic analyses of multizone or substructured three-dimensional solids. The elastic analyses involve isotropic or cross anisotropic media with thermal and centrifugal loading. The inelastic analyses include isotropic plasticity with variable hardening and kinematic plasticity with multiple yield surfaces.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620260208
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  • 3
    Electronic Resource
    Electronic Resource
    A variable stiffness type boundary element formulation for axisymmetric elastoplastic media (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1005-1027 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new ‘direct’ elastoplastic boundary element formulation for axisymmetric bodies is developed. The procedure exploits certain features of the constitutive relationship to express the unknwon non-linear initial stress rate tensor as a scalar quantity which can then be eliminated from the boundary equation system though a back substitution of the (modified) stress rate equations.This formulation is implemented in a multi-region system that utilizes quadratic isoparametric shape functions to model the geometry and field variables of the boundary and domain of a body. The kernel functions are presented in Appendix I and the singularities associated with these kernels are discussed. New techniques are described to calculate the coefficients associated with the singular nodes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620260502
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  • 4
    Electronic Resource
    Electronic Resource
    Time-domain transient elastodynamic analysis of 3-D solids by BEM (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1709-1728 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The numerical implementation of the Direct Boundary Element formulation for time-domain transient analysis of three-dimensional solids is presented in a most general and complete manner. The present formulation employs the space and time dependent fundamental solution (Stokes' solution) and Graffi's dynamic reciprocal theorem to derive the boundary integral equations in the time domain. A time-stepping scheme is then used to solve the boundary initial value problem by marching forward in time. Higher order shape functions are used to approximate the field quantities in space as well as in time, and a combination of analytical (time-integration) and numerical (spatial-integration) integration is carried out to form a system of linear equations. At the end of each time step, these equations are solved to obtain the unknown field quantities at that time.Finally, the accuracy and reliability of this algorithm is demonstrated by solving a number of example problems and comparing the results against the available analytical and numerical solution.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620260804
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  • 5
    Electronic Resource
    Electronic Resource
    Advanced boundary element analysis of two- and three-dimensional problems of elasto-plasticity (1986)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 23 (1986), S. 985-1002 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An advanced formulation of the boundary element method has been developed for inelastic analysis based on an initial stress approach. The iterative solution algorithm makes use of an accelerated initial stress approach in which the past history of initial stresses are used to obtain an initial estimate for the current increment. In the present analysis the geometry and functions are represented by higher order (quadratic) shape functions to model complex geometries and rapid functional variations accurately. The methods of numerical integration of the kernels, particularly the singular type, are substantially improved by devising suitable automatic sub-segmentation routines that incorporate the recent developments in mapping procedures. The formulations have been implemented for two-dimensional plane stress, plane strain and three-dimensional elasto-plasticity problems.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620230602
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  • 6
    Electronic Resource
    Electronic Resource
    A comparison between isoparametric Lagrangian elements in 2D BEM (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 1539-1555 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A comparison between a family of isoparametric C°-continucus elements in the context of two-dimensional elastostatics using the direct boundary element method is presented. The elements studied use Lagrangian shape functions of orders quadratic, cubic and quartic. The relative efficiencies of these elements from the viewpoint of accuracy of solution as well as cost effectiveness are examined through certain selected problems. It emerges from the present study that the quartic element is more reliable in accuracy than the lower members of the family without being necessarily more expensive.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620280706
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  • 7
    Electronic Resource
    Electronic Resource
    Inelastic transient dynamic analysis of three-dimensional problems by BEM (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 371-390 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A direct Boundary Element formulation and its numerical implementation for inelastic transient dynamic analysis of three-dimensional solids is presented. The formulation is based on an initial stress approach and is the first ever of its kind in the field of the Boundary Element Method. This formulation employs the Navier-Cauchy equation of motion, Graffi's dynamic reciprocal theorem, Stokes' fundamental solution and the Divergence theorem, together with Kinematical and Constitutive equations to obtain the pertinent integral equations of the problem in the time domain within the context of small displacement theory of elastoplasticity. The boundary integral equations are cast in an incremental form, in which elastoplastic relations of the incremental type are used for the material description. These equations are then solved using a time-stepping algorithm in conjunction with an iterative solution scheme to satisfy the constitutive relations. Higher order shape functions are used to approximate the field quantities in space as well as in time. Finally, the applicability of this methodology is demonstrated by presenting a few example problems.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620290211
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  • 8
    Electronic Resource
    Electronic Resource
    Advanced time-domain formulation of BEM for two-dimensional transient elastodynamics (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 1421-1440 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, a new formulation for two-dimensional time-domain transient elastodynamic analysis by the Boundary Element Method (BEM) is presented. The traction kernel is derived by using the causality of the waves and the resulting kernel is explicit and much simpler than the ones that have appeared in the recent literature. An appropriate set of linear time interpolation functions together with quadratic spatial variations are incorporated. Moreover, the algorithm has a capability of handling problems with multiply connected regions. All of these advanced features have resulted in an efficient formulation capable of producing very accurate results and represent significant improvements over the present level of sophistication in this area. This above algorithm is now a part of the general purpose BEM code known as GPBEST.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620290704
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  • 9
    Electronic Resource
    Electronic Resource
    Free-vibration analysis of three-dimensional solids by BEM (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 1737-1757 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In practical applications, it is often necessary to determine the natural frequencies and mode shapes of a solid, in addition to the static response under a variety of loading conditions. This paper discusses the calculation of natural frequencies and mode shapes of three-dimensional solids using the boundary element method. The method developed is based on the use of particular integrals of the elastic equilibrium equations, and employs only real arithmetic. It represents an extension to three dimensions of work previously carried out for two-dimensional problems in References 1 and 15. The method has been incorporated, for multiregion analysis, in the BEST3D (Boundary Element Solution Technology - Three Dimensional) computer program.Much of the work described in this paper was carried out under the support of National Aeronautics and Space Administration Contract NAS3-23697, ‘3D Inelastic Analysis Methods for Hot Section Components’. The program managers at the NASA-Lewis Research Center are Dr C. C. Chamis and Mr Dale Hopkins. The program manager at Pratt & Whitney is Dr E. S. Todd Results of the boundary element calculations are compared with analytical, finite element and experimental results.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620290809
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  • 10
    Electronic Resource
    Electronic Resource
    Time dependent axisymmetric thermoelastic boundary element analysis (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 695-717 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A boundary element method is developed for problems of quasistatic axisymmetric thermoelasticity. Unlike previous approaches, this new time domain formulation is written exclusively in terms of surface quantities, thereby eliminating the need for volume discretization. Furthermore, since the exact three-dimensional infinite space fundamental solutions are employed, very accurate solutions are obtainable, including the determination of surface stresses.In the integral formulation, the fundamental solutions are separated into steady-state and transient components. The steady-state portion, which contains all of the singularities, is integrated analytically in the circumferential direction, yielding the familiar axisymmetric kernels. The remaining non-singular transient integrands are treated by a combination of analytical and numerical quadrature.The method is implemented in a general purpose boundary element code, which includes multiregion capability along with higher order conforming surface elements. Several numerical examples are provided to illustrate the validity of the formulation and the attractiveness of this approach for practical engineenring analysis.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330403
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