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  • 1
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    Development of an integrated BEM for hot fluid-structure interaction (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: One of the most difficult problems in engine structural component durability analysis is the determination of the temperatures and fluxes in the structural components directly in contact with the hot gas flow path. Currently there exists no rational analytical or numerical technique which can effectively deal with this problem. Since the temperature distribution in the structural components are strongly influenced by both the fluid flow and the deformation as well as the cooling system in the structure, the only effective way to deal with this problem is to develop an integrated solid mechanics, fluid mechanics and heat transfer analysis for this problem. Herein, the Boundary Element Method (BEM) is chosen as the basic analysis tool principally because the definition of quantities like fluxes, temperatures, displacements, and velocities are very precise on a boundary based discretization scheme. One fundamental difficulty is that a BEM analysis requires a considerable amount of analytical work which is not present in other numerical methods. During the past year, all of this analytical work was completed and a two dimensional, general purpose code was written. A portion of the work is summarized.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Marshall Space Flight Center, Advanced Earth-to-Orbit Propulsion Technology 1988, Volume 1; p 69-86
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  • 2
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    Development of an integrated BEM for hot fluid-structure interaction (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Boundary Element Method (BEM) is chosen as a basic analysis tool principally because the definition of quantities like fluxes, temperature, displacements, and velocities is very precise on a boundary base discretization scheme. One fundamental difficulty is, of course, that the entire analysis requires a very considerable amount of analytical work which is not present in other numerical methods. During the last 18 months all of this analytical work was completed and a two-dimensional, general purpose code was written. Some of the early results are described. It is anticipated that within the next two to three months almost all two-dimensional idealizations will be examined. It should be noted that the analytical work for the three-dimensional case has also been done and numerical implementation will begin next year.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center, NASA Workshop on Computational Structural Mechanics 1987, Part 3; p 831-863
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  • 3
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    3-D inelastic analysis methods for hot section components. Volume 2: Advanced special functions models (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This Annual Status Report presents the results of work performed during the third year of the 3-D Inelastic Analysis Methods for Hot Sections Components program (NASA Contract NAS3-23697). The objective of the program is to produce a series of computer codes that permit more accurate and efficient three-dimensional analyses of selected hot section components, i.e., combustor liners, turbine blades, and turbine vanes. The computer codes embody a progression of mathematical models and are streamlined to take advantage of geometrical features, loading conditions, and forms of material response that distinguish each group of selected components.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-179517 , NAS 1.26:179517 , PWA-5940-46-VOL-2
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  • 4
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    On 3-D inelastic analysis methods for hot section components (base program) (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A 3-D Inelastic Analysis Method program is described. This program consists of a series of new computer codes embodying a progression of mathematical models (mechanics of materials, special finite element, boundary element) for streamlined analysis of: (1) combustor liners, (2) turbine blades, and (3) turbine vanes. These models address the effects of high temperatures and thermal/mechanical loadings on the local (stress/strain)and global (dynamics, buckling) structural behavior of the three selected components. Three computer codes, referred to as MOMM (Mechanics of Materials Model), MHOST (Marc-Hot Section Technology), and BEST (Boundary Element Stress Technology), have been developed and are briefly described in this report.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-175060 , NAS 1.26:175060 , ASR-2 , PWA-5940-36
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  • 5
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    Advanced three-dimensional dynamic analysis by boundary element methods (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Advanced formulations of boundary element method for periodic, transient transform domain and transient time domain solution of three-dimensional solids have been implemented using a family of isoparametric boundary elements. The necessary numerical integration techniques as well as the various solution algorithms are described. The developed analysis has been incorporated in a fully general purpose computer program BEST3D which can handle up to 10 subregions. A number of numerical examples are presented to demonstrate the accuracy of the dynamic analyses.
    Keywords: STRUCTURAL MECHANICS
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  • 6
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    Stress analysis of gas turbine engine structures using the boundary element method (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The theory of the boundary element method is briefly reviewed with particular reference to the feasibility of elastic and inelastic three-dimensional stress analysis of complex structures characteristic of gas turbine engine components. Particular requirements of gas turbine analysis are defined, and examples of the use of a boundary element code designed for the three-dimensional stress analysis of turbine components are presented. It is shown that the general-purpose boundary element code can accurately and efficiently analyze many of the gas turbine engine structures.
    Keywords: STRUCTURAL MECHANICS
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  • 7
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    Development of an integrated BEM approach for hot fluid structure interaction (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The development of a comprehensive fluid-structure interaction capability within a boundary element computer code is described. This new capability is implemented in a completely general manner, so that quite arbitrary geometry, material properties and boundary conditions may be specified. Thus, a single analysis code can be used to run structures-only problems, fluids-only problems, or the combined fluid-structure problem. In all three cases, steady or transient conditions can be selected, with or without thermal effects. Nonlinear analyses can be solved via direct iteration or by employing a modified Newton-Raphson approach. A number of detailed numerical examples are included at the end of these two sections to validate the formulations and to emphasize both the accuracy and generality of the computer code. A brief review of the recent applicable boundary element literature is included for completeness. The fluid-structure interaction facility is discussed. Once again, several examples are provided to highlight this unique capability. A collection of potential boundary element applications that have been uncovered as a result of work related to the present grant is given. For most of those problems, satisfactory analysis techniques do not currently exist.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-187236 , NAS 1.26:187236
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  • 8
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    Advanced development of BEM for elastic and inelastic dynamic analysis of solids (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Direct Boundary Element formulations and their numerical implementation for periodic and transient elastic as well as inelastic transient dynamic analyses of two-dimensional, axisymmetric and three-dimensional solids are presented. The inelastic formulation is based on an initial stress approach and is the first of its kind in the field of Boundary Element Methods. 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 the small displacement theory of elastoplasticity. The dynamic (periodic, transient as well as nonlinear transient) formulations have been applied to a range of problems. The numerical formulations presented here are included in the BEST3D and GPBEST systems.
    Keywords: STRUCTURAL MECHANICS
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  • 9
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    Advanced applications of BEM to inelastic analysis of solids (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Newly evolved boundary element solution algorithms are utilized for solving a range of elastoplastic and thermoplastic problems. The first algorithm is the typical iterative procedure in which the unknown boundary solution and the initial stress (or strain) rates are found together in an incremental iterative fashion. The second one is a variable stiffness type approach in which the incremental boundary solution is obtained in a direct (noniterative) manner. The third procedure differs from the two prior algorithms in that volume integration is not needed to incorporate the nonlinear effects in the analysis. Instead, initial stress rates are introduced in the boundary element system by way of particular integrals. The methodology is used in a general purpose, multiregion system that employs quadratic isoparametric shape functions to model the geometry and field variables of the body and can admit up to 15 substructured areas of different material properties.
    Keywords: STRUCTURAL MECHANICS
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  • 10
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    Micromechanical studies of composites by BEM (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Over the last five years BEM has been developed into a very effective tool for micromechanical studies of composites. The analyses developed range from static elastic analysis, steady state heat transfer, steady state and transient thermoelastic analysis, periodic and transient dynamic analysis. Currently some of these analyses are being extended to nonlinear micromechanical analyses involving viscoplasticity, elastoplasticity, combined plasticity fracture and creep. The paper describes some of the results for elastic analysis, heat transfer and thermoelastic analyses.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Enhancing analysis techniques for composite materials; Proceedings of the Symposium, ASME Winter Annual Meeting, Atlanta, GA, Dec. 1-6, 1991 (A93-31276 11-39); p. 221-228.
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