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  • 1
    Electronic Resource
    Electronic Resource
    An overview of advances in heat conduction models and approaches for prediction of thermal conductivity in thin dielectric films (2004)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 14 (2004), S. 12-65 
    Details
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We first provide an overview of some predominant theoretical methods currently used for predicting thermal conductivity of thin dielectric films: the equation of radiative transfer, the temperature-dependent thermal conductivity theories based on the Callaway model, and the molecular dynamics simulation. This overview also highlights temporal and spatial scale issues by looking at a unified theory that bridges physical issues presented in the Fourier and Cattaneo models. This newly developed unified theory is the so-called C- and F-processes constitutive model. This model introduces the notion of a new dimensionless heat conduction model number, which is the ratio of the thermal conductivity of the fast heat carrier F-processes to the total thermal conductivity comprised of both the fast heat carriers F-processes and the slow heat carriers C-processes. Illustrative numerical examples for prediction of thermal conductivity in thin films are primarily presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/09615530410511621
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  • 2
    Electronic Resource
    Electronic Resource
    Towards a formal theory of development/evolution and characterization of time discretized operators for heat transfer (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 348-381 
    Details
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The time-discretization process of transient equation systems is an important concern in computational heat transfer applications. As such, the present paper describes a formal basis towards providing the theoretical concepts, evolution and development, and characterization of a wide class of time discretized operators for transient heat transfer computations. Therein, emanating from a common family tree and explained via a generalized time weighted philosophy, the paper addresses the development and evolution of time integral operators [IO], and leading to integration operators [InO] in time encompassing single-step integration operators [SSInO], multi-step integration operators [MSInO], and a class of finite element in time integration operators [FETInO] including the relationships and the resulting consequences. Also depicted are those termed as discrete numerically assigned [DNA] algorithmic markers essentially comprising of both: the weighted time fields, and the corresponding conditions imposed upon the dependent variable approximation, to uniquely characterize a wide class of transient algorithms. Thereby, providing a plausible standardized formal ideology when referring to and/or relating time discretized operators applicable to transient heat transfer computations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/09615539910260185
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  • 3
    Electronic Resource
    Electronic Resource
    Computer graphics aided geometric modeling and mesh generation schemes for preprocessing and finite element analysis (1988)
    Springer
    Engineering with computers 3 (1988), S. 157-165 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The paper describes automated generation and editing schemes together with the development of computer-aided geometric models for general applications. For the construction of general finite element models of complex shapes, conventional approaches typical of wireframe, surface, or solid modeling cannot be effectively utilized for generating continuum solid models as well as discrete models simultaneously. In view of these facts, features to generate and model two-dimensional as well as threedimensional continuum and discrete models by isoparametric mapping/solid geometrical modeling techniques via a common interactive processor are described. The proposed scheme is demonstrated for modeling structural, thermal, or flow networks that are commonly encountered in engineering applications. In a research environment, the techniques addressed in this paper should prove to be very useful in providing flexibility and thereby significantly reducing the work load of frequent CAD users.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01349627
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  • 4
    Electronic Resource
    Electronic Resource
    Recent advances towards an effective virtual-pulse (VIP) explicit time integral methodology for general multidimensional thermal analysis (1995)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 20 (1995), S. 523-539 
    Details
    ISSN: 0271-2091
    Keywords: virtual pulse ; thermal analysis ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Recent advances and progress towards the development of an effective Virtual-Pulse (VIP) explicit time integral methodology of computation for applicability to general multidimensional non-linear transient thermal analysis of structures and materials is overviewed. The computational methodology is derived from new and different perspectives and the theoretical basis as well as the practical applicability to multidimensional thermal analysis situations are detailed. The VIP methodology inherits improved accuracy and superior stability characteristics in comparison to the traditional approaches customarily employed by thermal analysts. With the notion of providing techniques for high-speed computing environments and parallel architectures, the present approach is developed for such computations and also ideally suited for personal workstation computing environments. Results of the numerical test models for multidimensional problems validate the overall concepts for general applicability to thermal analysis situations.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650200608
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  • 5
    Electronic Resource
    Electronic Resource
    A robust self-starting explicit computational methodology for structural dynamic applications: Architecture and representations (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 1441-1454 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Conventional approaches for computational structural dynamics (CSD) relevant to time-integration methods involve first employing the classical Galerkin formulations for the spatial discretization to yield a set of ordinary differential equations in time and then employing finite difference approximations for deriving the appropriate step-by-step algorithms. And, almost all of the widely advocated (existing) step-by-step schemes for structural dynamics require an initial acceleration vector to be specified (evaluated) in addition to displacement and velocity vectors for starting the schemes. Unlike the above, in this paper we introduce new representations and architecture towards providing not only direct self-starting features with the elimination of acceleration computations but also for enhancing the computational architecture itself via several other inherent distinguishing characteristics. Thereby, a robust and effective methodology of computation is presented which is an extension of our previous efforts (see Tamma and Namburu3). In particular, to illustrate the basic concepts, in this paper we focus attention on the development of explicit time-integration formulations. The methodology involves expressing the governing dynamic equations of motion in conservation form, and firstly temporal discretization is accomplished in the spirit of Lax-Wendroff-type formulations. Therein, discretization in space is accomplished by introducing stress-based representations and employing the classical Galerkin scheme, and, quite naturally, we advocate employing finite elements as the principal computational tool because of its several inherent advantages. The stability and accuracy of the proposed formulations and the several added distinguishing features are briefly highlighted. Considerations on the effects of damping are additionally included and the introduction of general boundary conditions in a natural setting permits an effective generalized architecture for general applications. Numerical test models are presented to validate the overall developments for computational structural dynamics.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620290705
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  • 6
    Electronic Resource
    Electronic Resource
    Prediction of thermal stress and deformations due to phase change in solidifying objects via flux/stress based finite element representations (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 1473-1485 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents numerical simulations for the prediction of thermal-stress and deformation fields resulting from phase change in solidifying bodies employing new finite element representations. The formulations developed in this paper provide different perspectives and physical interpretation for the modelling/analysis of thermo-mechanical problems and possess several inherent advantages. In comparison to traditional approaches for solving similar problems, the paper employs new computational architectures in conjunction with flux/stress based representations to enhance the overall effectiveness. Comparative numerical applications validate applicability of the formulations for predicting the temperature induced deformations and stresses resulting from effects due to phase change.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620290707
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  • 7
    Electronic Resource
    Electronic Resource
    A new explicit variable time-integration self-starting methodology for computational structural dynamics (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1165-1180 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new explicit variable time-integration methodology and architecture which possesses self-starting attributes, eliminates the need to involve acceleration computations, and which has improved accuracy characteristics in comparison to the traditional central-difference-type formulations customarily advocated is described for applicability to computational structural dynamics. To sharpen the focus of the present study, an explicit variable time-integration architecture which is relatively simple, yet effective, is described. Unlike variable explicit time-integration formulations adopted in the past, the present self-starting variable time-integration architecture and implementation aspects facilitate a simplified representation and a straightforward and effective approach for combining finite element meshes requiring different time steps in a single analysis. Numerical test cases are provided which demonstrate the applicability of the proposed formulations.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330605
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  • 8
    Electronic Resource
    Electronic Resource
    Transfinite element methodology for non-liner/linear transient thermal modelling/analysis: Progress and recent advances (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 475-494 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Recent progress and advances in the development and applicability of a novel ‘transfinite element’ computational methodology is presented for general non-linear/linear transient thermal problems. The proposed methodology and concepts are new and unique, and demonstrate the applicability to general transient non-linear/linear thermal analysis situations by combining classical Galerkin schemes and transform approaches with contemporary finite element methods to preserve the modelling versatility and numerical features-thereby, a hybrid computational methodology is proposed. Characteristic features and pertinent details of the approach are described for non-linear/linear transient thermal problems, wherein non-linearities due temperature dependence of thermophysical properties and/or general non-linear bound ary conditions to include radiation, effects due to phase change, etc., are considered. In addition, the use of high-continuity formulations in conjuction with the proposed methodology to furnish accurate temperature distributions and temperature gradients making use of a relatively smaller number of degrees of freedom is also demonstrated. Numerical test cases are presented for a variety of problems to demonstrate the fundamental features and applicability of the proposed formulations. The proposed hybrid transfinite element methodology and concepts offer significant potential for extension to several areas of mathematical physics and engineering and to interdisciplinary research areas.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620250213
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  • 9
    Electronic Resource
    Electronic Resource
    Recent advances, trends and new perspectives via enthalpy-based finite element formulations for applications to solidification problems (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 30 (1990), S. 803-820 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The present paper describes recent advances and trends in finite element developments and applications for solidification problems. In particular, in comparison to traditional methods of approach, new enthalpy-based architectures based on a generalized trapezoidal family of representations are presented which provide different perspectives, physical interpretation and solution architectures for effective numerical simulation of phase change processes encountered in solidification problems. Various numerical test models are presented and the results support the proposition for employing such formulations for general phase change applications.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620300415
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Conjugate gradient based projection: A new explicit computational methodology for frictional contact problems (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 633-648 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: With special attention towards the applicability to parallel computation or vectorization, a new and effective explicit computational approach for linear complementary formulations involving a conjugate gradient based projection methodology is proposed in this study for contact problems with Coulomb friction. The overall objectives are focused towards providing an explicit methodology of computation for the complete contact problem with friction. In this regard, the primary idea for solving the linear complementary formulations stems from an established search direction which is projected to a feasible region determined by the non-negative constraint condition; this direction is then applied to the Fletcher-Reeves conjugate gradient method resulting in a powerful explicit methodology which possesses high accuracy, excellent convergence characteristics, fast computational speed and is relatively simple to implement for contact problems involving Coulomb friction. Numerical test cases are also included to demonstrate the proposed methodology for contact problems with friction.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100807
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