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  • STRUCTURAL MECHANICS  (277)
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  • 1983  (277)
  • 1
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    Publikationsdatum: 2011-08-19
    Beschreibung: A constitutive theory is presented for representing the anisotropic viscoplastic behavior of high-temperature alloys that possess directional properties resulting from controlled grain growth or solidification. The theory is an extension of a viscoplastic model that has been applied in structural analyses involving isotropic metals. Anisotropy is introduced through the definition of a vector field that identifies a preferential (solidification) direction at each material point. Following the development of a full multiaxial theory, application is made to homogeneously stressed elements in pure shear and to a uniaxially stressed rectangular block in plane stress with the stress direction oriented at an arbitrary angle with the material direction. It is shown that an additional material parameter introduced to characterize the degree of anisotropy can be determined on the basis of simple creep tests.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Nuclear Engineering and Design (ISSN 0029-5493); 83; 389-396
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  • 2
    Publikationsdatum: 2011-08-18
    Beschreibung: The force input mobility of an infinite elastic circular cylindrical shell filled with fluid is derived by using the spectral equations of motion. Mobilities are evaluated and their physical interpretations are discussed for a steel shell of thickness h/a = 0.05 filled with water and vibrating in the n = 0, 1 and 2 circumferential modes. The results are subsequently used to analyze the related situations of wave transmission through a radial ring constraint and the far field vibrational energy distributions between the contained fluid and the shell wall for line and point driving forces.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration (ISSN 0022-460X); 87; 409-427
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  • 3
    Publikationsdatum: 2011-08-18
    Beschreibung: The boundary collocation method was used to generate Mode 1 stress intensity and crack mouth opening displacement coefficients for externally radially cracked ring segments subjected to three point radial loading. Numerical results were obtained for ring segment outer-to-inner radius ratios (R sub o/R sub i) ranging from 1.10 to 2.50 and crack length to segment width ratios (a/W) ranging from 0.1 to 0.8. Stress intensity and crack mouth displacement coefficients were found to depend on the ratios R sub o/R sub i and a/W as well as the included angle between the directions of the reaction forces. Previously announced in STAR as N83-35413
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Testing and Evaluation (ISSN 0090-3973); 11; 357-359
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  • 4
    Publikationsdatum: 2011-08-18
    Beschreibung: Two methods for identifying the mass, damping and stiffness matrices of a linear vibrating system are presented. Both methods require the measurement of acceleration, velocity and displacement at various locations of the system. In the first method, the response of the system subjected to known forces is used while the second method employs the free vibration data. The unknown parameters are recovered through the standard least squares procedure. Numerical results are presented for several examples.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: JPL Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 511-520
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  • 5
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    Publikationsdatum: 2011-08-18
    Beschreibung: The problem of potential instability caused by actuator dynamics is examined. Two ways of overcoming it are discussed: rate feedback with compensation and position feedback with tuning filters.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: JPL Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 119-142
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  • 6
    Publikationsdatum: 2011-08-18
    Beschreibung: (Previously announced in STAR as N82-24501)
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 7
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    Publikationsdatum: 2011-08-18
    Beschreibung: Problems encountered by aerospace designers in attempting to optimize whole aircraft are discussed, along with possible solutions. Large scale optimization, as opposed to component-by-component optimization, is hindered by computational costs, software inflexibility, concentration on a single, rather than trade-off, design methodology and the incompatibility of large-scale optimization with single program, single computer methods. The software problem can be approached by placing the full analysis outside of the optimization loop. Full analysis is then performed only periodically. Problem-dependent software can be removed from the generic code using a systems programming technique, and then embody the definitions of design variables, objective function and design constraints. Trade-off algorithms can be used at the design points to obtain quantitative answers. Finally, decomposing the large-scale problem into independent subproblems allows systematic optimization of the problems by an organization of people and machines.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 8
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    Publikationsdatum: 2011-08-18
    Beschreibung: A simplified buckling analysis is presented for a family of periodic lattice structures such as those proposed for large space structures. A transcendental 6 x 6 matrix of eigenvalues is shown to be sufficient for modeling buckling behavior because member stiffnesses are based on an exact solution of the beam-column equation. Exact stiffnesses are derived for a curved member, thus allowing modeling of imperfect lattice structures. Comparisons of predictions of the lattice model with those available from shell and beam theory underscore the inaccuracies introduced by treating the lattice structure as a continuum. Sample calculations are provided for an isogrid cylinder and a three element double-laced truss.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 9
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    Publikationsdatum: 2011-08-18
    Beschreibung: Truss beams with members having viscous damping are modeled with a Timoshenko beam. Procedures for deriving the equivalent bending rigidity, transverse shear rigidity, and damping are presented. Explicit expressions for these equivalent beam properties are obtained for a specific truss beam. The beam model thus established is then used to investigate the effect of damping in free vibration. Finally, the beam is employed in the estimation of structural parameters in a simply-supported truss beam using a random search algorithm.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: JPL Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 531-545
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  • 10
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    Publikationsdatum: 2011-08-18
    Beschreibung: A general approach for distributed parameter modeling of complex dynamical systems is described. The method consists of dividing the system in parts which can be modeled by simple partial differential equations and coupling the equations thus obtained by applying Hamilton's variational formalism to the entire system. The modeling of a large, offset-fed, wrap-rib antenna is presented to illustrate the approach. Although such models are perhaps not as precise as finite element models, they can be useful for initial physical insight and parametric design.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 89-102
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  • 11
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    Publikationsdatum: 2011-08-18
    Beschreibung: The hybrid experimental-numerical stress-analysis technique, which saw limited applications during the 1950's, has been resurrected with the vastly improved numerical techniques of the 1970's. By inputing the experimental results as initial and boundary conditions, modern computer codes are executed in its generation and application modes to yield results which are unobtainable when only one of the two techniques is used. The hybrid technique thus exemplifies the complementary role of the experimental and numerical techniques.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: (ISSN 0014-4851)
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  • 12
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    Publikationsdatum: 2011-08-18
    Beschreibung: Fourier transforms and the Wiener-Hopf technique are used in conjunction with plane elastostatics to examine the singular crack tip stress field in the double cantilever beam (DCB) specimen. In place of the Dirac delta function, a family of functions which duplicates the important features of the concentrated forces without introducing unmanageable mathematical complexities is used as a loading function. With terms of order h-squared/a-squared retained in the series expansion, the dimensionless stress intensity factor is found to be K (h to the 1/2)/P = 12 to the 1/2 (a/h + 0.6728 + 0.0377 h-squared/a-squared), in which P is the magnitude of the concentrated forces per unit thickness, a is the distance from the crack tip to the points of load application, and h is the height of each cantilever beam. The result is similar to that obtained by Gross and Srawley by fitting a line to discrete results from their boundary collocation analysis.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Fracture (ISSN 0376-9429); 22; June 198
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  • 13
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    Publikationsdatum: 2011-08-18
    Beschreibung: A fracture mechanics approach to the well-known delamination problem in composite materials is presented. Based on the theory of anisotropic laminate elasticity and interlaminar fracture mechanics concepts, the composite delamination problem is formulated and solved. The exact order of the delamination crack-tip stress singularity is determined. Asymptotic stress and displacement fields for an interlaminar crack are obtained. Fracture mechanics parameters such as mixed-mode stress intensity factors, KI, KII, KIII, and the energy release rate, G, for composite delamination problems are defined. To illustrate the fundamental nature of the delamination crack behavior, solutions for edge-delaminated graphite-epoxy composites under uniform axial extension are presented. Effects of fiber orientation, ply thickness, and delamination length on the interlaminar fracture are examined.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Composite Materials (ISSN 0021-9983); 17; May 1983
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  • 14
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2112, Accession no. A82-30182
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: (ISSN 0001-1452)
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  • 15
    Publikationsdatum: 2011-08-18
    Beschreibung: Stress-intensity factors are obtained for point loaded equal length cracks emanating from a circular hole in an infinite plate. A series approach and the Muskhelishvili formulation in the two-dimensional theory of elasticity are used to derive the solution. The applicability of the solution is demonstrated by using it as a Green's function to obtain stress-intensity factors in the case of (1) biaxial tension and pure shear of an infinite plate and (2) tension and pin loading of a plate with cracks emanating from one hole in a row of holes.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Res Mechanica (ISSN 0143-0084); 9; 2, 19; 1983
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  • 16
    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2111, Accession no. A82-30171
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: (ISSN 0021-8669)
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  • 17
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2110, Accession no. A82-30166
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: (ISSN 0001-1452)
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  • 18
    Publikationsdatum: 2016-06-07
    Beschreibung: The objectives of the hot section technology (HOST) burner liner cyclic rig test program are basically threefold: (1) to assist in developing predictive tools needed to improve design analyses and procedures for the efficient and accurate prediction of burner liner structural response; (2) to calibrate, evaluate and validate these predictive tools by comparing the predicted results with the experimental data generated in the tests; and (3) to evaluate existing as well as advanced temperature and strain measurement instrumentation, both contact and noncontact, in a simulated engine cycle environment. The data generated will include measurements of the thermal environment (metal surface temperatures) as well as structural (strain) and life (fatigue) responses of simulated burner liners and specimens under controlled boundary and operating conditions. These data will be used to calibrate, compare and validate analytical theories, methodologies and design procedures, as well as improvements in them, for predicting liner temperatures, stress-strain responses and cycles to failure. Comparison of predicted results with experimental data will be used to show where the predictive theories, etc. need improvements. In addition, as the predictive tools, as well as the tests, test methods, and data acquisition and reduction techniques, are developed and validated, a proven, integrated analysis/experiment method will be developed to determine the cyclic life of a simulated burner liner.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Turbine Eng. Hot Sect. Technol. (HOST); p 181-193
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  • 19
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The HOST Liner Cyclic Program is utilizing two types of test apparatus, rectangular box rigs and a full annular rig. To date two quartz lamp cyclic box rigs have been tested and a third is to begin testing in late October 1983. The box rigs are used to evaluate 5x8 inch rectangular linear samples. A 21 inch diameter outer liner simulator is also being built up for testing beginning in April 1984. All rigs are atmospheric rigs. The first box rig, a three 6-kVA lamp installation, was operated under adverse conditions to determine feasibility of using quartz lamps for cyclic testing. This work was done in December 1981 and looked promising. The second box rig, again using three 6-kVA lamps, was operated to obtain instrumentation durability information and initial data input to a Finite Element Model. This limited test program was conducted in August 1983. Five test plates were run. Instrumentation consisted of strain gages, thermocouples and thermal paint. The strain gages were found to fail at 1200 F as expected though plates were heated to 1700 F. The third box rig, containing four 6-kVA lamps, is in build up for testing to begin in late October 1983. In addition to 33 percent greater power input, this rig has provision for 400 F backside line cooling air and a viewing port suitable for IR camera viewing. The casing is also water cooled for extended durability.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Turbine Eng. Hot Sect. Technol. (HOST); p 195-204
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  • 20
    Publikationsdatum: 2016-06-07
    Beschreibung: The objective of this program is to produce a series of new computer codes that permit more accurate and efficient three dimensional inelastic analysis of selected hot section components - 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.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 179-180
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  • 21
    Publikationsdatum: 2016-06-07
    Beschreibung: The objective of this research is to develop an analytical tool capable of economically evaluating the cyclic time dependent plasticity which occurs in hot section engine components in areas of strain concentration resulting from the combination of both mechanical and thermal stresses. The techniques developed must be capable of accommodating large excursions in temperatures with the associated variations in material properties including plasticity and creep. The overall objective of this proposed program is to develop advanced 3-D inelastic structural/stress analysis methods and solution strategies for more accurate and yet more cost effective analysis of combustors, turbine blades, and vanes. The approach will be to develop four different theories, one linear and three higher order with increasing complexities including embedded singularities.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 175-177
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  • 22
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    In:  CASI
    Publikationsdatum: 2014-09-11
    Beschreibung: The dynamic characteristics of the Solar Array Flight Experiment (SAFE) structure during deployment and retraction are investigated. The SAFE structure consists of a deployable mast with an attached solar blanket designed with accordion type folds to permit packaging in a small volume. The planar form of the blanket geometry during deployment is maintained by a blanket tension/guidewire system. Structurally, the mast is modeled as an Euler beam column with inplane and out of plane bending and finite torsional stiffness. For out of plane motion, the blanket is modeled as a distributed mass uniformly supported by the three guidewires. For inplane motion the blanket displacements are assumed to vary linearly from the mast base to the mast tip. The mathematical model uses a virtual work formulation, required because the axial loading on the mast is nonconservative, combined with assumed beam modes to derive the differential equations of motion. Consideration of the time dependent boundary conditions results in an infinite set of ODE with time dependent coefficients. Finally, correlation of mast tip accelerations to mast base bending moments for specified modal motions are indicated.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 24 p
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  • 23
    Publikationsdatum: 2014-09-11
    Beschreibung: Traditional composite lamination theory was used to predict composite graphite-epoxy laminate stiffnesses for comparison to quasi-experimental stiffnesses developed from cylindrical bottle pressure testing. Stiffness sensitivities were examined for variations in constituent materials and geometric properties. The material component interactions examined were the fiber longitudinal and transverse Young's modulus, the fiber shear modulus and primary Poisson's ratio, the resin Young's modulus, shear modulus, and Poisson's ratio. The geometric variation of the helical winding angle was also examined. Two computer programs were written to generate the data used to demonstrate the stiffness variations.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Alabama Univ. Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 34 p
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  • 24
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    In:  CASI
    Publikationsdatum: 2014-09-10
    Beschreibung: An experiment to measure the elastic deflection of the DSS 14 concrete pedestal under the weight of the antenna was conducted in February 1983 and is compared to a similiar experiment made in 1968. Comparison of the results confirms the decrease in elastic modulus measured on core samples recently taken from the pedestal.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The Telecommun. and Data Acquisition Rept.; p 89-91
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  • 25
    Publikationsdatum: 2011-08-18
    Beschreibung: An unconditionally stable implicit-explicit method is proposed for the analysis of transient coupled thermal stress waves, and the computer-implementation aspects of the method are discussed. In the method proposed here, the mechanical displacement and temperature are used as independent variables. The resulting coupled finite element matrix equations are symmetric.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures (ISSN 0045-7949); 17; 3, 19; 1983
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  • 26
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2112, Accession no. A82-30186
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: (ISSN 0001-1452)
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  • 27
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2108, Accession no. A82-30124
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 21; 1729-173
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  • 28
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 01, p. 60, Accession no. A83-10900
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 20; 907-912
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  • 29
    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2109, Accession no. A82-30152
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 20; 899-906
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  • 30
    Publikationsdatum: 2011-08-18
    Beschreibung: A fracture mechanics analysis has been developed that describes the progress of delamination damage in composite plates struck by a hard spherical object. The analysis is based on large deflection plate mechanics for circular isotropic plates wherein multiple axisymmetric delaminations grow. Test data show that the analysis predicts the influence of plate thickness, support conditions, and matrix toughness on the onset and propagation of delamination.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 31
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    Publikationsdatum: 2011-08-18
    Beschreibung: A three-dimensional element based on the total Lagrangian description of large deformations of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 32
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: One of the primary drivers that prompted the initiation of the hot section technology (HOST) program was the recognized need for improved cyclic durability of costly hot section components. All too frequently, fatigue in one form or another was directly responsible for the less than desired durability, and prospects for the future weren't going to improve unless a significant effort was mounted to increase our knowledge and understanding of the elements governing cyclic crack initiation and propagation lifetime. Certainly one of the important factors is the ability to perform accurate structural stress-strain analyses on a routine basis to determine the magnitudes of the localized stresses and strains since it is these localized conditions that govern the initiation and crack growth processes. Developing the ability to more accurately predict crack initiation lifetimes and cyclic crack growth rates for the complex loading conditions found in turbine engine hot sections is of course the ultimate goal of the life prediction research efforts. It has been found convenient to divide the research efforts into those dealing with nominally isotropic and anisotropic alloys; the latter for application to directionally solidified and single crystal turbine blades.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Turbine Eng. Hot Sect. Technol. (HOST); p 205-207
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  • 33
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The Hot Section Technology (HOST) Project is a NASA-sponsored endeavor to improve the durability of advanced gas turbine engines for commercial and military aircraft. Through improvements in the analytical models and life prediction systems, designs for future hot section components , the combustor and turbine, will be more accurately analyzed and will incorporate features required for longer life in the more hostile operating environment of high performance engines.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Turbine Eng. Hot Sect. Technol. (HOST); p 1-6
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  • 34
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    Publikationsdatum: 2018-12-01
    Beschreibung: A review of developments in structural optimization techniques and their interface with growing computer capabilities is presented. Structural design steps comprise functional definition of an object, an evaluation phase wherein external influences are quantified, selection of the design concept, material, object geometry, and the internal layout, and quantification of the physical characteristics. Optimization of a fully stressed design is facilitated by use of nonlinear mathematical programming which permits automated definition of the physics of a problem. Design iterations terminate when convergence is acquired between mathematical and physical criteria. A constrained minimum algorithm has been formulated using an Augmented Lagrangian approach and a generalized reduced gradient to obtain fast convergence. Various approximation techniques are mentioned. The synergistic application of all the methods surveyed requires multidisciplinary teamwork during a design effort.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 35
    Publikationsdatum: 2016-03-09
    Beschreibung: The mechanics of materials and material characterization are considered, taking into account micromechanics, the behavior of steel structures at elevated temperatures, and an anisotropic plasticity model for inelastic multiaxial cyclic deformation. Other topics explored are related to advances and trends in finite element technology, classical analytical techniques and their computer implementation, interactive computing and computational strategies for nonlinear problems, advances and trends in numerical analysis, database management systems and CAD/CAM, space structures and vehicle crashworthiness, beams, plates and fibrous composite structures, design-oriented analysis, artificial intelligence and optimization, contact problems, random waves, and lifetime prediction. Earthquake-resistant structures and other advanced structural applications are also discussed, giving attention to cumulative damage in steel structures subjected to earthquake ground motions, and a mixed domain analysis of nuclear containment structures using impulse functions.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 36
    Publikationsdatum: 2014-09-12
    Beschreibung: Static analysis and a computer structural model for the large 64-m antenna pedestal are developed using the MSC version of the NASTRAN program. This model was necessary to conduct a variety of hydrostatic bearing rehabilitation studies. The results obtained from the model show that the top surface deflections due to pad loads are in good agreement with the results previously obtained from a simplified "shortcut' analytical model, and also in agreement with field measurements. In addition, the displacement and force distributions as well as the state of stress and strain are obtained.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The Telecommun. and Data Acquisition Rept.; p 86-96
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  • 37
    Publikationsdatum: 2016-06-07
    Beschreibung: The empennage structure on the Learjet 55 aircraft was quite similar to the empennage structure on earlier Learjet models. However, due to an important structural change in the vertical fin along with the new loads environment on the 50 series aircraft, a structural test was required on the vertical fin, but the horizontal tail was substantiated by a comparative analysis with previous tests. NASTRAN analysis was used to investigate empennage deflections, stress levels, and control surface hinge forces. The hinge force calculations were made with the control surfaces in the deflected as well as undeflected configurations. A skin panel buckling analysis was also performed, and the non-linear effects of buckling were simulated in the NASTRAN model to more accurately define internal loads and stress levels. Comparisons were then made between the Model 55 and the Model 35/36 stresses and internal forces to determine which components were qualified by previous tests. Some of the methods and techniques used in this analysis are described.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 226-248
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  • 38
    Publikationsdatum: 2016-06-07
    Beschreibung: The J-4 Rocket Test Cell and its Thrust Measuring System (TMS) at Arnold Engineering Development Center were modified to provide multicomponent force measurement of large solid rocket motors having nozzle gimbaling capability. To verify the structural integrity of a combined TMS and motor system, a large finite element model of the TMS and motor was developed using the NASTRAN computer program. Due to the importance of obtaining accurate estimates for the dynamic force levels, it was necessary to certify that the model adequately simulated the physical system. This was accomplished by performing a modal analysis test on the TMS and motor combination. The objectives were to discuss the physical characteristics of the TMS and motor that influence the NASTRAN model; to compare the frequency response characteristics computed using the NASTRAN model to those obtained from the modal analysis test; to discuss the experiences gained in modal analysis testing; and to demonstrate how state-of-the-art experimental and analytical methods are used in the design of ground test facilities.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 207-225
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  • 39
    Publikationsdatum: 2016-06-07
    Beschreibung: Modeling of flexural and membrane type waves existing in various submerged (or in vacuo) plate and/or shell finite element models that are excited with steady state type harmonic loadings proportioned to e(i omega t) is discussed. Only thin walled plates and shells are treated wherein rotary inertia and shear correction factors are not included. More specifically, the issue of determining the shell or plate mesh size needed to represent the spatial distribution of the plate or shell response is of prime importance towards successfully representing the solution to the problem at hand. To this end, a procedure is presented for establishing guide lines for determining the mesh size based on a simple test model that can be used for a variety of plate and shell configurations such as, cylindrical shells with water loading, cylindrical shells in vacuo, plates with water loading, and plates in vacuo. The procedure for doing these four cases is given, with specific numerical examples present only for the cylindrical shell case.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 178-206
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  • 40
    Publikationsdatum: 2016-06-07
    Beschreibung: An analysis is given using finite element techniques which addresses the propagaton of a uniform incident pressure wave through a finite diameter axisymmetric tapered plate immersed in a fluid. The approach utilized in developing a finite element solution to this problem is based upon a technique for axisymmetric fluid structure interaction problems. The problem addressed is that of a 10 inch diameter axisymmetric fixed plate totally immersed in a fluid. The plate increases in thickness from approximately 0.01 inches thick at the center to 0.421 inches thick at a radius of 5 inches. Against each face of the tapered plate a cylindrical fluid volume was represented extending five wavelengths off the plate in the axial direction. The outer boundary of the fluid and plate regions were represented as a rigid encasement cylinder as was nearly the case in the physical problem. The primary objective of the analysis is to determine the form of the transmitted pressure distribution on the downstream side of the plate.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 161-177
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  • 41
    Publikationsdatum: 2016-06-07
    Beschreibung: This paper presents a technique for calculating the modal participation factors for base excitation problems using a DMAP alter to the NASTRAN real eigenvalue analysis Rigid Format. The DMAP program automates the generation of the seismic mass to add to the degrees of freedom representing the shaker input directions and calculates the modal participation factors. These are shown in the paper to be a good measure of the maximum acceleration expected at any point on the structure when the subsequent frequency response analysis is run.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 113-140
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  • 42
    Publikationsdatum: 2016-06-07
    Beschreibung: Two finite element procedures are described for predicting the dynamic response of general 3-D fluid-filled elastic piping systems. The first approach, a low frequency procedure, models each straight pipe or elbow as a sequence of beams. The contained fluid is modeled as a separate coincident sequence axial members (rods) which are tied to the pipe in the lateral direction. The model includes the pipe hoop strain correction to the fluid sound speed and the flexibility factor correction to the elbow flexibility. The second modeling approach, an intermediate frequency procedure, follows generally the original Zienkiewicz-Newton scheme for coupled fluid-structure problems except that the velocity potential is used as the fundamental fluid unknown to symmetrize the coefficient matrices. From comparisons of the beam model predictions to both experimental data and the 3-D model, the beam model is validated for frequencies up to about two-thirds of the lowest fluid-filled labor pipe mode. Accurate elbow flexibility factors are seen to be crucial for effective beam modeling of piping systems.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 141-160
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  • 43
    Publikationsdatum: 2016-06-07
    Beschreibung: An alternative method of analysis to determine the dynamic response of structures subjected to base accelerations is presented. The method is exact as opposed to the approximate technique of using unusually large masses and loads to enforce desired base accelerations. This paper presents the relevant equations to motion, ALTERs for direct and modal frequency-, random- and transient-response rigid formats, and illustrative examples.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 89-112
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  • 44
    Publikationsdatum: 2016-06-07
    Beschreibung: An equivalence between temperature and pressure, heat conduction and stiffness and heat capacity and mass is defined, enabling acoustical modal analysis of arbitrary three dimensional volumes. The transient heat transfer analysis rigid format in NASTRAN, RF9, has been altered providing the acoustical analysis capability. Examples and ALTERs are included.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 82-88
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  • 45
    facet.materialart.
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The NASTRAN TRAPRG and TRAPAX finite elements are very restrictive as to shape and grid point numbering. The elements must be trapezoidal with two sides parallel to the radial axis. In addition, the ordering of the grid points on the element connection card must follow strict rules. The paper describes the generalization of these elements so that these restrictions no longer apply.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 76-81
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  • 46
    Publikationsdatum: 2016-06-07
    Beschreibung: GPRIME, an interactive modeling system, runs on the CDC 6000 computers and the DEC VAX 11/780 minicomputer. This system includes three components: (1) GPRIME, a user friendly geometric language and a processor to translate that language into geometric entities, (2) GGEN, an interactive data generator for 2-D models; and (3) SOLIDGEN, a 3-D solid modeling program. Each component has a computer user interface of an extensive command set. All of these programs make use of a comprehensive B-spline mathematics subroutine library, which can be used for a wide variety of interpolation problems and other geometric calculations. Many other user aids, such as automatic saving of the geometric and finite element data bases and hidden line removal, are available. This interactive finite element modeling capability can produce a complete finite element model, producing an output file of grid and element data.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 33-45
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  • 47
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: A finite element was developed to adequately represent the state of stress in the region around a circular hole in orthotropic material experiencing reasonably general loading. This has been achieved through a complementary virtual work formulation of the stiffness and stress matrices for a square element with a center circular hole. The element has been incorporated into COSMIC/NASTRAN as a dummy element. Sample problems have been solved and these results are presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 46-75
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  • 48
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Since the initial installation of NASTRAN on the UNIVAC 1100/82 computer at the Marshall Space Flight Center (MSFC), a number of local codes have been incorporated as user routines. This paper describes four of these codes and how interested users may obtain additional information.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 6-20
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  • 49
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Programs for Automatic Finite Element Calculations (PAFEC) is a general purpose, three dimensional linear and nonlinear finite element program (ref. 1). PAFEC's features include free format input utilizing engineering keywords, powerful mesh generating facilities, sophisticated data base management procedures, and extensive data validation checks. Presented here is a description of a software interface that permits PAFEC to be used as a preprocessor for COSMIC/NASTRAN. This user friendly software, called PAFCOS, frees the stress analyst from the laborious and error prone procedure of creating and debugging a rigid format COSMIC/NASTRAN bulk data deck. By interactively creating and debugging a finite element model with PAFEC, thus taking full advantage of the free format engineering keyword oriented data structure of PAFEC, the amount of time spent during model generation can be drastically reduced. The PAFCOS software will automatically convert a PAFEC data structure into a COSMIC/NASTRAN bulk data deck. The capabilities and limitations of the PAFCOS software are fully discussed in the following report.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 21-32
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  • 50
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: BANDIT has been implemented into the NASTRAN April '83 release. It is now a permanent feature in NASTRAN and will be included in all future releases for all four computing machines (IBM, CDC, UNIVAC, and VAX). Originally BANDIT operated as a preprocessor of NASTRAN. It read the NASTRAN input cards and produced a set of resequencing (SEOGP) cards that would greatly reduce the computational time required by the matrix decomposition module of NASTRAN for a large structure. In the past, many computer centers had installed BANDIT in their systems together with the NASTRAN program. The user would run the BANDIT program and NASTRAN as if they were one program (or two separated programs depending on how the two programs were actually tied together in the computer systems). In some cases, the user was required to pass the input cards and the output SEQGP cards between the two programs, and n others, the data was manipulated through the use of cataloged disc files. Although there is nothing wrong with this BANDIT-NASTRAN arrangement, there are, however, several shortcomings which are mentioned in this paper. The BANDIT in the NASTRAN April '83 release has removed all the deficiencies, and it comes in one version applicable to the four computing machines.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 1-5
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  • 51
    Publikationsdatum: 2016-06-07
    Beschreibung: Static analysis and a computer structural model for the large 64-m antenna pedestal are developed using the MSC version of the NASTRAN program. This improved pedestal model includes the launch areas and the actual pressure pattern of the oil under the hydrostatic bearing pad. The results obtained from the new improved model have indicated that the deflections due to pad loads are in good agreement with field measurements. The top surface deflection of the pedestal obtained from the NASTRAN model is used as an input to the oil film computer program to determine the minimum oil film thickness under the pad.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The Telecommun. and Data Acquisition Rept.; p 105-113
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  • 52
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The need for describing materials under time or cycle dependent loading conditions has been emphasized in recent years by several investigators. In response to the need, various constitutive models describing the nonlinear behavior of materials under creep, fatigue, or other complex loading conditions were developed. The developed models for describing the fully dense (non-porous) materials were mostly based on uncoupled plasticity theory. The improved characterization of materials provides a better understanding of the structual response under complex loading conditions. The pesent studies demonstrate that the rate or time dependency of the response of a porous aggregate can be incorporated into the nonlinear constitutive behavior of a porous solid by appropriately modeling the incompressible matrix behavior. It is also sown that the yield function which wads determined by a continuum mechanics approach must be verified by appropriate experiments on void containing sintered materials in order to obtain meaningful numbers for the constants that appear in the yield function.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 267-282
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  • 53
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: A new uncoupled viscoplastic model has been proposed along with experiments and analysis to define the various material constraints. Distinguishing between rate sensitive and rate insensitive strain allows the rate sensitive strain to be modelled over a wide range of temperatures with very little variation in the stress component 'n'. Furthermore, it allows the rounded corners on stress-strain hysteresis loops to be achieved very naturally.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 217-234
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  • 54
    Publikationsdatum: 2016-06-07
    Beschreibung: A uniaxial, uncoupled constitutive model to predict the response of thermal and rate dependent elastic-plastic material behavior is presented. The model is based on an incremental classicial plasticity theory extended to account for thermal, creep, and transient temperature conditions. Revisions to he combined hardening rule of the theory allow for better representation of cyclic phenomenon including the high rate of strain hardening upon cyclic reyield and cyclic saturation. An alternative approach is taken to model the rate dependent inelastic deformation which utilizes hysteresis loops and stress relaxation test data at various temperatures. The model is evaluated and compared to experiments which involve various thermal and mechanical load histories on 5086 aluminum alloy, 304 stainless steel and Hastelloy-X.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 185-190
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  • 55
    Publikationsdatum: 2016-06-07
    Beschreibung: Constitutive equations with only two easily determined material constants predict the stress (strain) response of normalized mild steel to a variety of general strain (stress) histories, without a need for special unloading-reloading rules. The equations are derived from the endochronic theory of plasticity of isotropic materials with an intrinsic time scale defined in the plastic strain space. Agreement between theoretical predictions and experiments are are excellent quantitatively in cases of various uniaxial constant amplitude histories, variable uniaxial strain amplitude histories and cyclic relaxation. The cyclic ratcheting phenomenon is predicted by the present theory.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 191-216
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  • 56
    Publikationsdatum: 2016-06-07
    Beschreibung: A single phenomenological constitutive equation is derived theoretically from first principles and applied to aluminum, tin and lead. The theory is based on deformation kinetics of steady creep in which the fundamental mechanism is atomic transport over potential barriers whose conformation is distorted by the application of a stress field. The form of the functional dependence of barrier distortion and stress over the entire temperature range is found to be a sigmoidal curve which tends to straight lines of a unit slope in the small and high stress regions. With this form of barrier distortion, the constitutive equation prediction the steady creep behavior of aluminum, tin and lead over a wide range of temperature and stress.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 139-152
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  • 57
    Publikationsdatum: 2016-06-07
    Beschreibung: The influence of inelastic material models on computed stress-strain states, and therefore predicted lives, was studied for thermomechanically loaded structures. Nonlinear structural analyses were performed on a fatigue specimen which was subjected to thermal cycling in fluidized beds and on a mechanically load cycled benchmark notch specimen. Four incremental plasticity creep models (isotropic, kinematic, combined isotropic-kinematic, combined plus transient creep) were exercised. Of the plasticity models, kinematic hardening gave results most consistent with experimental observations. Life predictions using the computed strain histories at the critical location with a Strainrange Partitioning approach considerably overpredicted the crack initiation life of the thermal fatigue specimen.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Nonlinear Constitutive Relations for High Temp. Appl.; p 89-106
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  • 58
    Publikationsdatum: 2016-06-07
    Beschreibung: A modification was formulated to Besseling's Subvolume Method to allow it to use multilinear stress-strain curves which are temperature dependent to perform cyclic thermoplasticity analyses. This method automotically reproduces certain aspects of real material behavior important in the analysis of Aircraft Gas Turbine Engine (AGTE) components. These include the Bauschinger effect, cross-hardening, and memory. This constitutive equation was implemented in a finite element computer program called CYANIDE. Subsequently, classical time dependent plasticity (creep) was added to the program. Since its inception, this program was assessed against laboratory and component testing and engine experience. The ability of this program to simulate AGTE material response characteristics was verified by this experience and its utility in providing data for life analyses was demonstrated. In this area of life analysis, the multiaxial thermoplasticity capabilities of the method have proved a match for the actual AGTE life experience.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 69-88
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  • 59
    Publikationsdatum: 2016-06-07
    Beschreibung: The approach for the method development assumes that, for a thermally loaded structure, the overall strain history is defined by linear elastic analysis. The local stress history at a fatigue critical location is then determined from a one dimensional material behavior model and the local strain and temperature conditions. Three material models are currently being evaluated to assess their ability to predict relevant high temperature cyclic material response characteristics. They are: a time independent classical plasticity and creep representation, a time dependent viscoplastic model capable of predicting combined creep and plasticity effects, and an approximate elastic analysis approach that uses a series of stress-strain curves and a cyclic hardening model to determine reverse plasticity.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 43-46
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  • 60
    Publikationsdatum: 2016-06-07
    Beschreibung: The stress and temperature sensitivites of the rupture life and secondary creep rate were examined in detail for a single heat of type 304 stainless steel (9T2796). Assuming that the rupture life has a power law stress dependency, relatively small differences in the stress exponent were observed over a broad range of stress and temperature. In contrast, large changes were observed for equivalent parameter for secondary creep rate. As a result of these differences, the Monkman-Grant correlation was sensitive to stress and temperature below 650 C. Metallurgical studies based on light and transmission electron microscopy suggested that the temperature and stress sensitivities of secondary creep rate at temperatures below 650 C were related to features of the substructure not present at higher temperature. Specifically, the presence of a fine dislocation network stabilized by precipitates altered the stress and temperature sensitivities relative to what might be expected from high temperature studies.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 1-12
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  • 61
    Publikationsdatum: 2016-06-07
    Beschreibung: A new method for generating and updating Rigid Formats in NASTRAN is discussed. The heart of this method is a Rigid Format data base that is in card-image format and that can therefore be easily maintained by the use of standard text editors. Each Rigid Format entry in this data base will contain the Direct Matrix Abstraction Program (DMAP) for that Rigid Format along with the related restart, subset and substructure control tables. NASTRAN will read this data base directly in every NASTRAN run and perform the necessary transformations to allow the DMAP to be processed and compiled by the NASTRAN executive. This approach will permit Rigid Formats to be changed without unnecessary compilations and relinking of NASTRAN. Furthermore, this approach will also make it very easy for users to make permanent changes to existing Rigid Formats as well as to generate their own Rigid Formats. This new method will be incorporated in a future release of the public version of NASTRAN.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 249-254
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  • 62
    facet.materialart.
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The plate elements of the NASTRAN code are used to analyze two annular plate problems loaded beyond the elastic limit. The first problem is an elastic-plastic annular plate loaded externally by two concentrated forces. The second problem is stressed radially by uniform internal pressure for which an exact analytical solution is available. A comparison of the two approaches together with an assessment of the NASTRAN code is given.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 281-292
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  • 63
    Publikationsdatum: 2016-06-07
    Beschreibung: Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 255-280
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  • 64
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The factors that must be taken into consideration when applying NASTRAN's linear analysis to structures whose principle boundaries are formed by bolting, and for which localized stress peaking is important are discussed. An illustration is given in an application to a mounting bracket.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: COSMIC 11th NASTRAN User's Colloq.; p 293-303
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  • 65
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    In:  Other Sources
    Publikationsdatum: 2019-01-25
    Beschreibung: The low-velocity impact problem in graphite/epoxy composite sheets must be solved before large amounts of that material can be used in commercial aircraft. Many of the low-velocity impacts that affect aircraft parts occur during normal ground operations and maintenance. Service equipment and tools have masses above 1 kg, and at velocities of less than 3 m/s can impact structural parts with energies higher than composites can endure without degradation of stiffness or strength. Simple solutions were developed for large-mass, low-velocity impacts which can be modeled as quasi-static events. Static test data and impact data show that the fiber properties control the impact energy which can be absorbed before penetration. Matrix shear strength and peel resistance control the extent of delamination. Comparison of results from tough matrix and brittle matrix composites show that although tough matrices reduce the extent of delamination, they lead to more fiber damage in the contact area.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Delaware Univ. Abstr. of the 20th Ann. Meeting, Society of Engineering Science, Inc.; p 57
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  • 66
    Publikationsdatum: 2017-10-02
    Beschreibung: An analytical model of crack closure is used to study the crack growth and closure behavior of small cracks in plates and at notches. The calculated crack opening stresses for small and large cracks, together with elastic and elastic plastic fracture mechanics analyses, are used to correlate crack growth rate data. At equivalent elastic stress intensity factor levels, calculations predict that small cracks in plates and at notches should grow faster than large cracks because the applied stress needed to open a small crack is less than that needed to open a large crack. These predictions agree with observed trends in test data. The calculations from the model also imply that many of the stress intensity factor thresholds that are developed in tests with large cracks and with load reduction schemes do not apply to the growth of small cracks. The current calculations are based upon continuum mechanics principles and, thus, some crack size and grain structure exist where the underlying fracture mechanics assumptions become invalid because of material inhomogeneity (grains, inclusions, etc.). Admittedly, much more effort is needed to develop the mechanics of a noncontinuum. Nevertheless, these results indicate the importance of crack closure in predicting the growth of small cracks from large crack data.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AGARD Behaviour of Short Cracks in Airframe Components; 26 p
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  • 67
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The evolution of an electromechanical control actuation system from trade study results through breadboard test and high-g launch demonstration tests is summarized. Primary emphasis is on design, development, integration and test of the gear reduction system.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: JPL The 17th Aerospace Mech. Symp.; p 181-198
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  • 68
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Criteria for selection of optimal damper locations are presented. A damping synthesis problem was formulated and applied to a NASA grillage model.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Structual Dyn. and Control of Large Space Struct., 1982; p 249-262
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  • 69
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    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Because of inherent low damping and high flexibility, large space structures may require some form of active control of their dynamics. Because of the apparent inability to accurately model the dynamics of these structures, methods for parameter adaptive control are now being developed at Langley. This approach uses a digital computer to process discrete sensor data, identify modal parameters, calculate modal control gains, and then convert the modal forces to real forces. Some of the problems considered are: (1) the possibility that there may be modes to control with limited amounts of hardware, and (2) the required accuracy of identified structural parameters.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Structural Dyn. and Control of Large Space Struct., 1982; p 235-247
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  • 70
    facet.materialart.
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    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: A computer program for redesigning structural modes to reduce response has been initiated. The linear regulator approach in modal coordinates has been implemented. It is noted that the transformation of solution to physical structure is a major problem. It is concluded that the solution of stiffness equations and damping equations can be done separately as NXN set of (matrix Riccati) equations.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Structural Dyn. and Control of Large Space Struct., 1982; p 141-150
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  • 71
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: How the presence of nonlinearities in structural test data can be detected when using modern linear modal data analysis methods is discussed. The extent to which linear algorithms can provide useful information on nonlinear systems was discussed. The modal data analysis method successfully identified the frequency components (but not damping) of the true solution of a nonlinear systems. It was found that the approximate modal parameters of the linear system can be identified by the modal method when low levels of nonlinearities are present. The modal method successfully identified the modal parameters of a linear mode in the presence of a nonlinear response.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Structural Dyn. and Control of Large Space Struct., 1982; p 135-140
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  • 72
    Publikationsdatum: 2016-06-07
    Beschreibung: Techniques which use decoupling theory and state variable feedback to control the pitch attitude and the flexible mode amplitudes of a long, thin beam are discussed. An observer based on the steady state Kalman filter was incorporated into the control design procedure in order to estimate the values of the modal state variables required for the feedback control law.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Structural Dyn. and Control of Large Space Struct., 1982; p 9-38
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  • 73
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The development of an algorithm that will determine actuator and sensor locations on a flexible beam is discussed. Large space structures will have many locations where actuators can be placed. This research seeks to determine the optimum locations. In addition, the best locations are determined while certain constraints are satisfied which guarantee that mission performance requirements are achieved. The approach adopted is to consider actuators and sensors to be collocated so as to produce an equivalent viscous damper. Ultimately, the experimental results of measuring the log decrement during free decay will correlate with the analytical predictions.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Structural Dyn. and Control of Large Space Struct., 1982; p 1-8
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  • 74
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The testing technique and some results from an experimental study to determine tire temperature profiles to aid in defining the strength and fatigue limitations of the tire carcass structure are described. This effort is part of a program to explore analytically and through experiment the temperature distribution in an aircraft tire during free roll and braked and yawed rolling conditions.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Tire Modeling; p 211-222
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  • 75
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Adhesion testing appeared to offer a less burdensome alternative to replace some of the dynamometer tests. Accordingly, test results and data were requested from retreaders who had used adhesion testing.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 175-192
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  • 76
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: A method was developed for calculating the internal temperature distribution in an aircraft tire while free rolling under load. The method uses an approximate stress analysis of each point in the tire as it rolls through the contact patch, and from this stress change the mechanical work done on each volume element may be obtained and converted into a heat release rate through a knowledge of material characteristics. The tire cross-section is then considered as a body with internal heat generation, and the diffusion equation is solved numerically with appropriate boundary conditions of the wheel and runway surface. Comparison with data obtained with buried thermocouples in tires shows good agreement.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 193-210
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  • 77
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Ongoing aircraft tire experimental programs are reported. These programs are designed to measure profile growth due to inflation pressure and vertical loading, contact pressures in the tire footprint, and a number of tire mechanical properties including spring, damping, and relaxation characteristics.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Tire Modeling; p 163-174
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  • 78
    Publikationsdatum: 2016-06-07
    Beschreibung: The effect of a combined external load consisting of a normal component and a tangential braking force applied to an inflated torus is addressed. Experimental results obtained by photographic study of the contact area between the torus and load plate are presented as well as measurements of the vertical and horizontal displacement of the torus under load. A numerical procedure for displacement analysis is developed in which the finite element program STAGS (Structural Analysis of General Shells) is used in an iterative manner to produce a flat, horizontal footprint surface under force loading. The redistributed force distribution obtained by the iterative process is displayed along with computed meridional and circumferential stresses. Finally, an extension of the iterative method is introduced which eliminates the need to experimentally determine the footprint area.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 141-162
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  • 79
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: An efficient method for calculating the contact boundary and interfacial pressure distribution was developed. This solution technique utilizes the discrete Fourier transform to establish an influence coefficient matrix for the portion of the pressurized tire surface that may be in the contact region. This matrix is used in a linear algebra algorithm to determine the contact boundary and the array of forces within the boundary that are necessary to hold the tire in equilibrium against a specified contact surface. The algorithm also determines the normal and tangential displacements of those points on the tire surface that are included in the influence coefficient matrix. Displacements within and outside the contact region are calculated. The solution technique is implemented with a finite-element tire model that is based on orthotropic, nonlinear shell of revolution elements which can respond to nonaxisymmetric loads. A sample contact solution is presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 95-122
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  • 80
    Publikationsdatum: 2016-06-07
    Beschreibung: Finite element analysis is applied to study the large deflection and stress of a thin-walled pressurized torus loaded by normal contact with a plane. Experimentally determined stresses are compared to those resulting from finite element analysis at various meridional and circumferential coordinates of the torus, including the footprint area. Circumferential strains compare favorably while meridional strains are higher in the finite element analysis, probably due to slippage of the boundary at the rim. The STAGS finite element computer program was used. The purpose of the study was to evaluate the various program options for structural loading, for material modeling, for stress analysis, and for grid refinement. The experimental model, a thin-walled rubber tube mounted on a steel cylindrical rim, provided measured results to compare with various analytical trade-offs. It was found that there was almost no difference in predicted deflections or stress distributions between linear and nonlinear material description. However, the difference between linear analysis and that of geometric nonlinearities utilizing incremental loading was marked.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 123-140
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  • 81
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: The tire plays a key part in many analyses used for design of aircraft landing gear. Examples include structural design of wheels, landing gear shimmy, brake whirl, chatter and squeal, complex combination of chatter and shimmy on main landing gear (MLG) systems, anti-skid performance, gear walk, and rough terrain loads and performance. Tire parameters needed in the various analyses are discussed. Two tire models are discussed for shimmy analysis, the modified Moreland approach and the von Schlippe-Dietrich approach. It is shown that the Moreland model can be derived from the Von Schlippe-Dietrich model by certain approximations. The remaining analysis areas are discussed in general terms and the tire parameters needed for each are identified. Accurate tire data allows more accurate design analysis and the correct prediction of dynamic performance of aircraft landing gear.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 71-94
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  • 82
    Publikationsdatum: 2016-06-07
    Beschreibung: A number of finite element methods for the analysis of nonlinear problems in rubber elasticity are outlined. Several different finite element schemes are discussed. These include the augmented Lagrangian method, continuation or incremental loading methods, and associated Riks-type methods which have the capability of incorporating limit point behavior and bifurcations. Algorithms for the analysis of limit point behavior and bifurcations are described and the results of several numerical experiments are presented. In addition, a brief survey of some recent work on modelling contact and friction in elasticity problems is given. These results pertain to the use of new nonlocal and nonlinear friction laws.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 39-70
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  • 83
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Predicting the response of tires under various loading conditions using finite element technology is addressed. Some of the recent advances in finite element technology which have high potential for application to tire modeling problems are reviewed. The analysis and modeling needs for tires are identified. Reduction methods for large-scale nonlinear analysis, with particular emphasis on treatment of combined loads, displacement-dependent and nonconservative loadings; development of simple and efficient mixed finite element models for shell analysis, identification of equivalent mixed and purely displacement models, and determination of the advantages of using mixed models; and effective computational models for large-rotation nonlinear problems, based on a total Lagrangian description of the deformation are included.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Langley Research Center Tire Modeling; p 1-38
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  • 84
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2018-12-01
    Beschreibung: The inelastic deformation of engineering alloys was recently shown to be rate (time)-dependent at room temperature. Experiments reported herein demonstrate that inelastic strain path length is a suitable measure for the modeling of work hardening for these materials, whereas inelastic work is not appropriate. The measured deformation induced temperature change is well predicted by a previously proposed theory of thermomechanical coupling. It has been derived by neglecting the stored energy of cold work and by assuming tha the internal energy expression for thermoelasticity is valid even when the mechanical deformation is inelastic.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 85
    Publikationsdatum: 2019-06-28
    Beschreibung: Work is in progress to demonstrate two techniques for static strain measurements on a jet engine burner liner. Measurements are being made with a set of resistance strain gages made from Kanthal A-1 wire and via heterodyne speckle photogrammetry. The background of the program is presented along with current results.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 41-44
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  • 86
    Publikationsdatum: 2019-06-28
    Beschreibung: The planar transverse bending behavior of a uniform cantilevered beam with rigid tip body subject to constant axial base acceleration was analyzed. The beam is inextensible and capable of small elastic transverse bending deformations only. Two classes of tip bodies are recognized: (1) mass centers located along the beam tip tangent line; and (2) mass centers with arbitrary offset towards the beam attachment point. The steady state response is studied for the beam end condition cases: free, tip mass, tip body with restricted mass center offset, and tip body with arbitrary mass center offset. The first three cases constitute classical Euler buckling problems, and the characteristic equation for the critical loads/accelerations are determined. For the last case a unique steady state solution exists. The free vibration response is examined for the two classes of tip body. The characteristic equation, eigenfunctions and their orthogonality properties are obtained for the case of restricted mass center offset. The vibration problem is nonhomogeneous for the case of arbitrary mass center offset. The exact solution is obtained as a sum of the steady state solution and a superposition of simple harmonic motions.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-175567 , NAS 1.26:175567 , CSDL-R-1675
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  • 87
    Publikationsdatum: 2019-06-28
    Beschreibung: The planar dynamics of a uniform elastic beam subject to a variety of geometric and natural boundary conditions and external excitations were analyzed. The beams are inextensible and capable of small transverse bending deformations only. Classical beam vibration eigenvalue problems for a cantilever with tip mass, a cantilever with tip body and an unconstrained beam with rigid bodies at each are examined. The characteristic equations, eigenfunctions and orthogonality relations for each are derived. The forced vibration of a cantilever with tip body subject to base acceleration is analyzed. The exact solution of the governing nonhomogeneous partial differential equation with time dependent boundary conditions is presented and compared with a Rayleigh-Ritz approximate solution. The arbitrary planar motion of an elastic beam with rigid bodies at the ends is addressed. Equations of motion are derived for two modal expansions of the beam deflection. The motion equations are cast in a first order form suitable for numerical integration. Selected FORTRAN programs are provided.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-175566 , NAS 1.26:175566 , CSDL-R-1629
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  • 88
    Publikationsdatum: 2019-06-28
    Beschreibung: A new hybrid-stress finite element algorithm suitable for analyzing large quasistatic deformations of inelastic solids is presented and its feasibility and performance are demonstrated with examples. The algorithm provides extremely accurate bifurcation analysis which is stable with respect to variation in the finite element mesh, so long as the same type of element is used in every mesh. When the mesh element is varied, the result changes in a predictable manner. The method does not necessarily lead to an upper or lower bound for the critical load. An explicit forward gradient scheme is used to improve stability and is shown to be useful also for elongation-dominated deformations. The application of the method to the onset of necking in plane extension and to deformation and stress in plane extension of an elasticoviscous fluid with an array of cylindrical voids is given in detail.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 40; 171-198
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  • 89
    Publikationsdatum: 2019-06-28
    Beschreibung: A new hybrid-stress finite element algorithm, suitable for analyses of large, quasistatic, inelastic deformations, is presented. The algorithm is base upon a generalization of de Veubeke's complementary energy principle. The principal variables in the formulation are the nominal stress rate and spin, and thg resulting finite element equations are discrete versions of the equations of compatibility and angular momentum balance. The algorithm produces true rates, time derivatives, as opposed to 'increments'. There results a complete separation of the boundary value problem (for stress rate and velocity) and the initial value problem (for total stress and deformation); hence, their numerical treatments are essentially independent. After a fairly comprehensive discussion of the numerical treatment of the boundary value problem, we launch into a detailed examination of the numerical treatment of the initial value problem, covering the topics of efficiency, stability and objectivity. The paper is closed with a set of examples, finite homogeneous deformation problems, which serve to bring out important aspects of the algorithm.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 39; 245-295
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  • 90
    Publikationsdatum: 2019-06-28
    Beschreibung: In the finite element method for structural analysis, it is generally necessary to discretize the structural model into a very large number of elements to accurately evaluate displacements, strains, and stresses. As the complexity of the model increases, the number of degrees of freedom can easily exceed the capacity of present-day software system. Improvements of structural analysis software including more efficient use of existing hardware and improved structural modeling techniques are discussed. One modeling technique that is used successfully in static linear and nonlinear analysis is multilevel substructuring. This research extends the use of multilevel substructure modeling to include dynamic analysis and defines the requirements for a general purpose software system capable of efficient nonlinear dynamic analysis. The multilevel substructuring technique is presented, the analytical formulations and computational procedures for dynamic analysis and nonlinear mechanics are reviewed, and an approach to the design and implementation of a general purpose structural software system is presented.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-174504 , NAS 1.26:174504 , SM-8
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  • 91
    Publikationsdatum: 2019-06-28
    Beschreibung: The results of a 10-month research and development program for nonlinear structural modeling with advanced time-temperature constitutive relationships are presented. The implementation of the theory in the MARC nonlinear finite element code is discussed, and instructions for the computational application of the theory are provided.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-168191-VOL-2 , NAS 1.26:168191-VOL-2 , R83-956077-2
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  • 92
    Publikationsdatum: 2019-06-28
    Beschreibung: The results of a 10-month research and development program for the development of advanced time-temperature constitutive relationships are presented. The program included (1) the effect of rate of change of temperature, (2) the development of a term to include time independent effects, and (3) improvements in computational efficiency. It was shown that rate of change of temperature could have a substantial effect on the predicted material response. A modification to include time-independent effects, applicable to many viscoplastic constitutive theories, was shown to reduce to classical plasticity. The computation time can be reduced by a factor of two if self-adaptive integration is used when compared to an integration using ordinary forward differences. During the course of the investigation, it was demonstrated that the most important single factor affecting the theoretical accuracy was the choice of material parameters.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-168191-VOL-1 , NAS 1.26:168191-VOL-1 , R83-956077-1
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  • 93
    Publikationsdatum: 2019-06-28
    Beschreibung: Fatigue crack growth tests were performed on center crack panels and radial crack hole samples. The data were reduced and correlated with the elastic parameter K taking into account finite width and corner crack corrections. The anomalous behavior normally associated with short cracks was not observed. Total life estimates for notches were made by coupling an initiation life estimate with a propagation life estimate.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-168225 , NAS 1.26:168225 , UDR-TR-83-57
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  • 94
    Publikationsdatum: 2019-06-28
    Beschreibung: A Boeing 707 fuselage section was drop tested at the NASA Langley Research Center to measure structural, seat, and occupant response to vertical crack loads. Post-test inspection showed that the section bottom collapsed inward approximately 2 ft. Preliminary data traces indicated maximum normal accelerations of 20 g on the fuselage bottom, 10 to 12 g on the cabin floor, and 6.5 to 8 g in the pelvises of the anthropomorphic dummies.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TM-85679 , NAS 1.15:85679
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  • 95
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2019-06-28
    Beschreibung: The crack problem of a shallow shell with two nonzero curvatures is considered. It is assumed that the crack lies in one of the principal planes of curvature and the shell is under Mode I loading condition. The material is assumed to be specially orthotropic. After giving the general formulation of the problem the asymptotic behavior of the stress state around the crack tip is examined. The analysis is based on Reissner's transverse shear theory. Thus, as in the bending of cracked plates, the asymptotic results are shown to be consistent with that obtained from the plane elasticity solution of crack problems. Rather extensive numerical results are obtained which show the effect of material orthotropy on the stress intensity factors in cylindrical and spherical shells and in shells with double curvature. Other results include the stress intensity factors in isotropic toroidal shells with positive or negative curvature ratio, the distribution of the membrane stress resultant outside the crack, and the influence of the material orthotropy on the angular distribution of the stresses around the crack tip. Previously announced in STAR as N83-16782
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Engineering Fracture Mechanics (ISSN 0013-7944); 18; 3 19; 1983
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  • 96
    Publikationsdatum: 2019-06-28
    Beschreibung: A full asymptotic solution is presented for the fields in the neighborhood of the tip of a steadily advancing crack in an incompressible elastic-perfectly-plastic solid. There are four findings for mode I crack growth in the plane strain condition. The first is that the entire crack tip in steady crack growth is surrounded by a plastic region and that no elastic unloading is predicted by the complete dynamic asymptotic solution. The second is that, in contrast to the quasi-static solution, the dynamic solution yields strain fields with a logarithmic singularity everywhere near the crack tip. The third is that whereas the stress field varies throughout the entire crack tip neighborhood, it does not exhibit behavior that can be approximated by a constant field followed by an essentially centered-fan field and then by another constant field, especially for small crack growth speeds. The fourth finding is that there are two shock fronts emanating from the crack tip across which certain stress and strain components undergo jump discontinuities. After reviewing the mode III steady-state crack growth, it is concluded that ductile fracture criteria for nonstationary cracks must be based on solutions that include the inertia effects and that for this purpose quasi-static solutions may be inadequate.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Mechanics of Materials (ISSN 0167-6636); 2; April 19
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  • 97
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2019-06-28
    Beschreibung: The determination of the elastodynamic fields of an ellipsoidal inhomogeneity is studied in detail via the eigenstrain approach. A complete formulation and a treatment of both types of eigenstrains for equivalence between the inhomogeneity problem and the inclusion problem are given. This approach is shown to be mathematically identical to other approaches such as the direct volume integral formulation. Expanding the eigenstrains and applied strains in the polynomial form in the position vector and satisfying the equivalence conditions at every point, the governing simultaneous algebraic equations for the unknown coefficients in the eigenstrain expansion are derived. The elastodynamic field outside an ellipsoidal inhomogeneity in a linear elastic isotropic medium is given as an example. The angular and frequency dependence of the induced displacement field, as well as the differential and total cross sections are formally given in series expansion form for the case of uniformly distributed eigenstrains.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: ASME PAPER 83-APM-19 , (ISSN 0021-8936)
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  • 98
    Publikationsdatum: 2019-06-28
    Beschreibung: Free vibrations of cantilevered circular cylindrical shells having rectangular planforms are studied in this paper by means of the Ritz method. The deep shell theory of Novozhilov and Goldenveizer is used and compared with the usual shallow shell theory for a wide range of shell parameters. A thorough convergence study is presented along with comparisons to previously published finite element solutions and experimental results. Accurately computed frequency parameters and mode shapes for various shell configurations are presented. The present paper appears to be the first comprehensive study presenting rigorous comparisons between the two shell theories in dealing with free vibrations of cantilevered cylindrical shells.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Mechanical Sciences (ISSN 0020-7403); 25; 5 19; 1983
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  • 99
    Publikationsdatum: 2019-06-28
    Beschreibung: The globally convergent quasi-Newton minimization algorithm and the homotopy algorithms are discussed in detail and their effectiveness in solving certain classes of highly nonlinear problems of structural analysis is demonstrated. The application of the double dogleg strategy controls the directions and step-lengths of the quasi-Newtonian algorithm and overcomes the problem of nonpositive definite Hessians being produced during the iteration process. The algorithms are applied to a centrally loaded clamped beam, the snap-through of a shallow arch, and a shallow reticulated dome.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures (ISSN 0045-7949); 17; 4 19; 1983
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  • 100
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2019-06-28
    Beschreibung: Two of the more common procedures for analyzing the stability and forced response of equations with periodic coefficients are reviewed: the use of Floquet methods, and the use of multiblade coordinate and harmonic balance methods. The analysis procedures of these periodic coefficient systems are compared with those of the more familiar constant coefficient systems. Previously announced in STAR as N82-23702
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 21; June 198
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