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  • Inorganic Chemistry  (2,983)
  • Physics  (1,584)
  • STRUCTURAL MECHANICS
  • 1995-1999
  • 1980-1984  (2,887)
  • 1970-1974  (1,588)
  • 1925-1929  (825)
  • 1983  (1,517)
  • 1981  (1,370)
  • 1972  (1,588)
  • 1927  (825)
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  • 1995-1999
  • 1980-1984  (2,887)
  • 1970-1974  (1,588)
  • 1925-1929  (825)
Year
  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-03-13
    Description: Great advances have been made in fundamental scientific research in recent years. The new knowledge gathered, in addition to deepening our understanding of the physical universe, contributes a range of abilities and opportunities to society that would not otherwise be available. Much research that may be called applied because it addresses needs of society is quite fundamental in character, and support of such research at the National Science Foundation is to be handled in tandem by the research directorates. Other areas that require a refocusing of support are engineering science and education, at all levels, in science and engineering. Increasing our strength in these areas is essential to achieve our national economic, social, and political goals. Steps are being taken by the National Science Foundation to make its structure better able to deal with engineering and applied research and to provide greater mutual reinforcement between applied and basic research.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slaughter, J B -- New York, N.Y. -- Science. 1981 Mar 13;211(4487):1131-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7466384" target="_blank"〉PubMed〈/a〉
    Keywords: Cell Biology ; Chemical Phenomena ; Chemistry ; *Forecasting ; Geological Phenomena ; Geology ; *Government Agencies ; Molecular Biology ; Neurochemistry ; Physical Phenomena ; Physics ; Research Support as Topic ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2005-11-30
    Description: The latest technology for structural analysis in relation to the design tasks that lie ahead for the space shuttle is reviewed. For shell-of-revolution structures, the analysis can be formulated as a one-dimensional problem which is readily solved by using finite-difference or numerical-integration techniques. For more general asymmetric shells, a two-dimensional formulation is required. However, the governing equations are readily formulated and are amenable to solution by finite-difference techniques. For a completely general structural arrangement, such as structural frameworks, recourse is usually made to discretized formulations using finite elements. Of course, the finite-element programs could be used for shell structures, but at a loss in accuracy and increase in computer time compared with the special purpose programs.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA Space Shuttle Technol. Conf.; p 685-725
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  • 3
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    Publication Date: 2011-08-16
    Description: The finite element method is extended to a broad class of practical nonlinear problems, treating both theory and applications from a general and unifying point of view. The thermomechanical principles of continuous media and the properties of the finite element method are outlined, and are brought together to produce discrete physical models of nonlinear continua. The mathematical properties of the models are analyzed, and the numerical solution of the equations governing the discrete models is examined. The application of the models to nonlinear problems in finite elasticity, viscoelasticity, heat conduction, and thermoviscoelasticity is discussed. Other specific topics include the topological properties of finite element models, applications to linear and nonlinear boundary value problems, convergence, continuum thermodynamics, finite elasticity, solutions to nonlinear partial differential equations, and discrete models of the nonlinear thermomechanical behavior of dissipative media.
    Keywords: STRUCTURAL MECHANICS
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  • 4
    Publication Date: 2011-08-16
    Description: Description of an efficient digital computer method for the determination of the propagation of elastic stresses and deformations in certain geometrically nonlinear structures subjected to high impact loading. The finite-element matrix displacement approach utilizing curved quadrilateral shell elements in conjunction with a nodewise predictor-corrector method employing Runge-Kutta extrapolation techniques has been adopted for the present solution. The related computer program written in FORTRAN V for the UNIVAC 1108 computer has proved to be effective for the solution of a range of practical problems including rectangular and cylindrical panels. Numerical results are presented for a relevant structure, the cell container, and the negative electrode of an impact-resistant battery subjected to high impact, simulating its free landing on a planetary surface.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering; 4; Mar
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  • 5
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    Publication Date: 2011-08-16
    Description: The effect of slight meridional curvature on the buckling of shells subjected to an external constant directional lateral pressure is examined. A class of nearly cylindrical shells with constant meridional curvature, a central radius-to-thickness ratio of 500, and central rise-to-shell-length ratios varying from plus 5% to minus 5% is considered. A brief study is presented of the dependence of the critical lateral pressure on the meridional curvature and on the length and meridional edge restraint.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Feb. 197
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  • 6
    Publication Date: 2011-08-16
    Description: The results are discussed of a study of the effect of slots on the buckling of cylinders with circular holes of systematically varied circularity. The results obtained suggest that the substantial increase in the buckling loads of cylindrical shells resulting from increases in slot length is due to a relief of the bending stress field.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Feb. 197
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  • 7
    Publication Date: 2011-08-16
    Description: The paper defines the experimental phase of an objective to obtain the mechanical characteristics and coefficients required by the generalized form of Hooke's law for nylon-polyurethane-coated fabric. Test specimens were cylindrical fabric sleeves and were loaded in axial tension by an Instron, in hoop tension by pressurizing, and in shear by a torquing fixture. An extensive amount of strain data is included for a wide combination of the three membrane loads. The tests indicate highly nonlinear stress-strain characteristics of the fabric and a strong dependency on all three membrane loads.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Aircraft; 9; Jan. 197
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  • 8
    Publication Date: 2011-08-16
    Description: Concepts of sonic-boom pressure loading of building structures and the associated responses are reviewed, and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic-boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of such other phenomena as three-dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data from laboratory models and full-scale building tests are summarized, and these data are compared, where possible, with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic-boom-induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.
    Keywords: STRUCTURAL MECHANICS
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  • 9
    Publication Date: 2011-08-16
    Description: Study of the failure of glass windows, which is probably the most severe problem confronting the SST program outside of the psychological and sociological aspects. The structural configuration most likely to suffer a window failure due to sonic boom excitation is one representable by a single large room, a single large window, and an open door. It is suggested that if the open door were replaced with another window the resultant stresses in both windows would be substantially reduced.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 21; Mar. 22
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  • 10
    Publication Date: 2011-08-19
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Nuclear Engineering and Design (ISSN 0029-5493); 83; 389-396
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  • 11
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 87; 409-427
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  • 12
    Publication Date: 2011-08-18
    Description: 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
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Testing and Evaluation (ISSN 0090-3973); 11; 357-359
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  • 13
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    Publication Date: 2011-08-16
    Description: Solutions are given for several plane elastostatic problems of plates having a V-notch on one edge, and subjected to a variety of boundary conditions. The effect of the magnitude of the V-notch angle and specimen geometry on stress intensity factors KI and KII are obtained for unloaded notch surfaces. There is less than one per cent difference in opening model stress intensity factor in going from a zero degree notch angle to a 30 degree notch angle. Notch opening displacements at the plate edge were measured experimentally, and the results obtained were in excellent agreement with the computed results.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture Mechanics; 8; Sept
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  • 14
    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 4; June 197
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  • 15
    Publication Date: 2011-08-16
    Description: Analysis of the panel flutter characteristics of a candidate thermal protection system (TPS) for the space shuttle, using piston theory aerodynamics and Lagrange equations. The results show the TPS candidate panel array to be deep in the 'no-flutter' region during launch and, therefore, safe from panel flutter.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Aug. 197
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  • 16
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    Publication Date: 2011-08-16
    Description: Consideration of Rayleigh wave effects in a homogeneous isotropic linearly elastic half-space subject to an impulsive uniform disk pressure loading. An approximate formula is obtained for the Rayleigh wave effects. It is shown that the Rayleigh waves near the center of loading arise from the portion of the dilatational and shear waves moving toward the axis, after they originate at the edge of the load disk. A study is made of the vertical displacement due to Rayleigh waves at points on the axis near the surface of the elastic half-space.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Aug. 197
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  • 17
    Publication Date: 2011-08-16
    Description: Consideration of coupled stress waves generated by an impulsive load applied at one end of a semiinfinite plate. For the field equations governing the one-dimensional coupled waves a hyperbolic system of equations is obtained in which a strong coupling in the second derivatives exists. The method of characteristics described by Chou and Mortimer (1967) is extended to cover the case of strong coupling, and a study is made of the transient stress waves in a semiinfinite plate subjected to an initial step input. Coupled discontinuity fronts are found to propagate at different velocities. The normal plate stress and the bending moment at different time regimes are illustrated by graphs.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Aug. 197
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  • 18
    Publication Date: 2011-08-16
    Description: The optical response to loading of a thin metallic film deposited on a low-modulus structural substrate is studied theoretically and experimentally. Two types of optical properties called total and central-image transmittance (or reflectance) are shown to be related to the mechanical state of the substrate. Empirical optical-mechanical relationships are proposed between these optical properties and the substrate strain field of a general plane-stress problem. A technique based on wrinkle and microfracture patterns is described for determining principal directions of strain. Experimental results for uniaxially loaded specimens show that it is possible to obtain a nearly linear relationship between transmittance and strain for certain materials combinations.
    Keywords: STRUCTURAL MECHANICS
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  • 19
    Publication Date: 2011-08-16
    Description: A lumped-parameter model of a rectangular plate is developed by assuming fundamental mode solutions and using Hamilton's Principle and the Euler equations to set up the differential equation of motion for the system. The plate theory used may be described as the dynamic analogue of the von Karman large-deflection theory. Four sets of symmetrical boundary conditions are considered with the restriction of uniform pressure dynamic loads. The model takes the form of a mass on a cubic-hardening spring with each term defined by algebraic expressions of the plate parameters. The results for some specific problems are compared with two previous solutions. This method is less accurate but simpler to develop and apply.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 21; Apr. 8
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  • 20
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    Publication Date: 2011-08-16
    Description: A generalized eigenvalue algorithm is presented herein along with the complete listing of the associated computer program, which may be conveniently utilized for the efficient solution of certain broad classes of eigenvalue problems. Extensive applications of the procedure are envisaged in the analysis of many important engineering problems, such as stability and natural frequency analysis of practical discrete structural systems, idealized by the finite element technique. The procedure based on the Sturm sequence method is accurate and fast, possessing several significant advantages over other known methods of such analysis. Numerical results are also presented for two representative structural engineering problems.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering; 4; May-June
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  • 21
    Publication Date: 2011-08-16
    Description: An experimental and analytical investigation of the effect of a circular hole on the buckling of thin cylindrical shells under axial compression was carried out. The experimental results were obtained from tests performed on seamless electroformed copper shells and Mylar shells with a lap joint seam. These results indicated that the character of the shell buckling was dependent on a parameter which is proportional to the hole radius divided by the square root of the product of the shell radius and thickness. For small values of this parameter, there was no apparent effect of the hole on the buckling load. For slightly larger values of the parameter, the shells still buckled into a general collapse configuration, but the buckling loads were sharply reduced as the parameter increased. For still larger values of the parameter, the buckling loads were further reduced, and the shells buckled into a stable local buckling configuration.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Nov. 197
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  • 22
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    Publication Date: 2011-08-16
    Description: A boron-aluminum structural component, representative of Space Shuttle fuselage structure, has been fabricated and tested as part of a program to demonstrate boron-aluminum feasibility for Shuttle applications. The 4- by 5-foot component consists of eleven 24-ply Z section stringers and a +45 degree 8-ply skin. It was tested at room temperature and at 500 F under combined compressive and shear loadings. The components for this program were fabricated in order to encounter and solve scale-up problems, and to obtain test data representative of production hardware. The data from this program are expected to allow more accurate prediction of weights and costs of boron-aluminum structures for the Space Shuttle.
    Keywords: STRUCTURAL MECHANICS
    Type: SAMPE Quarterly; 3; July 197
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  • 23
    Publication Date: 2011-08-16
    Description: An explicit formulation is developed to obtain the stored energy function, based on the Valanis-Landel separable symmetric stored energy function. This formulation is applicable to any multiaxial stress state, from simple tensile data alone, for those cases in which the stored energy function is a separable function of the stretch ratios. By direct comparison, it is also shown that styrene butadiene rubber, at least over a specific range, follows this postulated separable form.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Applied Physics; 43; July 197
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  • 24
    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Dec. 197
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  • 25
    Publication Date: 2011-08-16
    Description: This paper gives some examples of projects underway. The projects are grouped according to the primary parameter being studied: loads, configuration, environment, or material. Significant topics include the effect of truncated loads, the effect of proof-tests, interference fasteners, accelerated and real-time tests for supersonic aircraft materials, crack-growth rates in built-up structures, and a model method by which material can be selected for a particular set of operating conditions.
    Keywords: STRUCTURAL MECHANICS
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  • 26
    Publication Date: 2011-08-16
    Description: This paper deals with elastic stress intensity factors associated with stress fields near partially debonded interfaces in finite, bi-material plates. Bi-material stress intensity factors K1 and K2 are not associated, respectively, with symmetric and skew-symmetric loading and are functions of an arbitrary length parameter. Any fracture condition involving bi-material stress intensity factors must be independent of the arbitrary length parameter and must be consistent with experiment. We define a new parameter called the interfacial stress intensity factor which satisfies the former condition. A truncated Williams power series stress function for stresses in a cracked bi-material plate, as modified by Sih and Rice, is used with a modified boundary collocation procedure to generate interfacial stress intensity factors for finite bi-material plates.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 4; Dec. 197
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  • 27
    Publication Date: 2011-08-16
    Description: The results of an analytical study are presented on the use of boron polyimide filamentary composite material for the purpose of increasing the flutter speed of a simple titanium full depth sandwich wing structure designed for strength. The results clearly demonstrate that selective reinforcement of wing surfaces, using judiciously placed filamentary composites, promises sizable mass savings in the design of advanced aircraft structures.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Aircraft; 9; Nov. 197
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  • 28
    Publication Date: 2011-08-16
    Description: The problem of transient axisymmetric vibrations of thin circular elastic plates due to sonic boom excitation is investigated. The equation of motion for a solid circular plate is solved by applying the modified finite Hankel transform and the Laplace transform, and the numerical results are obtained with the help of the digital computer. From the analysis of the data, obtained for the dynamic deflections of the plates for the boom duration, it is concluded that for a normal flight the boom duration has a significant effect on the vibrations of plates as compared to the overpressure of the boom.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America; vol. 52
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  • 29
    Publication Date: 2011-08-18
    Description: Simple procedures are given for treating cumulative fatigue damage under complex loading history using either the damage curve concept or the double linear damage rule. A single equation is given for use with the damage curve approach; each loading event providing a fraction of damage until failure is presumed to occur when the damage sum becomes unity. For the double linear damage rule, analytical expressions are given for determining the two phases of life. The procedure comprises two steps, each similar to the conventional application of the commonly used linear damage rule. Once the sum of cycle ratios based on Phase I lives reaches unity, Phase I is presumed complete, and further loadings are summed as cycle ratios based on Phase II lives. When the Phase II sum attains unity, failure is presumed to occur. It is noted that no physical properties or material constants other than those normally used in a conventional linear damage rule analysis are required for application of either of the two cumulative damage methods described. Illustrations and comparisons are discussed for both methods.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 17; Apr. 198
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  • 30
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    Publication Date: 2011-08-18
    Description: Problems of elasticity associated with the behavior of free surfaces of elastic bodies are reviewed with particular reference to the propagation of characteristic waves and the criteria of wrinkling of free surfaces. All transformations are given for the case when a free surface of an elastic body is streamlined by the flow of inviscid fluid. The wrinkling phenomenon is illustrated by example.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Elasticity; 11; Apr. 198
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  • 31
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: 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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  • 32
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    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: 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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  • 33
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-24501)
    Keywords: STRUCTURAL MECHANICS
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  • 34
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    Publication Date: 2011-08-18
    Description: A methodology of formulating the optimum design problem for structural systems with random parameters and subjected to random vibration as a mathematical programming problem is presented. The proposed method is applied to the optimum design of a cantilever beam with a tip mass and a truss structure supporting a water tank. The excitations are assumed to be Gaussian processes and the geometric and material properties are taken to be normally distributed random variables. The probabilistic constraints are specified for individual failure modes since it is easier to specify the reliability level for each failure mode keeping in view the consequences of failure in that particular mode. The time parameter appearing in the random vibration based constraints is eliminated by replacing the probabilities of failure by suitable upper bounds. The numerical results demonstrate the feasibility and effectiveness of applying the reliability-based design concepts to structures with random parameters and operating in random vibration environment.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 14; 5-6,; 1981
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  • 35
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    Publication Date: 2011-08-18
    Description: This paper presents a structural dynamic modeling of the Long Duration Exposure Facility (LDEF), which is a Space Shuttle payload of passive scientific experiments contained in trays mounted on a large cylindrically shaped structure. Special detailed finite element modeling, using the SPAR system of computer programs was required to obtain good agreement between analytical and test vibrations modes. Experimental trays contributed significantly to overall LDEF stiffnesses, and these contributions were realistically represented for each tray by the stiffness matrix of an equivalent orthotropic panel in the overall LDEF SPAR model. Orthotropic stiffnesses for this panel were obtained from finely detailed statically loaded tray SPAR models in which stiffness coupling was accounted for along with partial relative sliding allowed by the tray clamping attachments. Joint boundary conditions were also significant in the structural dynamic modeling of LDEF, and static data proved valuable in assessing modeling of local end fittings.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 13; Aug. 198
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  • 36
    Publication Date: 2011-08-18
    Description: A necessary and sufficient condition is derived for the existence of the axisymmetric mode of cylindrical shells with a radial displacement having one half wave along the axis and axial displacement restrained at both ends. The condition is purely geometric and consists of an upper bound on the mean radius of thickness ratio for a given fixed value of the length to mean radius ratio, above which the mode with one half wave in radial displacement along the axis ceases to exist. The proof is based on enforcing two basic lemmas concerned with the simplicity of the eigenvalues of the shell and the uniform ordering of these eigenvalues with the number of nodes of their corresponding radial displacement eigenfunctions.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 74; Feb. 8
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  • 37
    Publication Date: 2011-08-18
    Description: The effect of elastic end rings on the eigenfrequencies of thin cylindrical shells is studied by using an exact solution of the linear eigenvalue problem. The out-of-plane and torsional rigidities of the rings are responsible for the overall shell stiffness. Considerable mode interaction exists for modes with low circumferential wave numbers when the mass of the ring is comparable with that of the shell. The hypothetical simply supported and clamped boundary conditions are practically impossible to realize with a finite-mass ring for relatively short and thin shells.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 74; Jan. 8
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  • 38
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    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
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  • 39
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    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
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  • 40
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: 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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  • 41
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 89-102
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  • 42
    Publication Date: 2011-08-18
    Description: An improved method of boundary collocation based on the complex variable analysis of Muskhelishvili (1953) is applied to the two-dimensional stress analysis of round compact specimens with pin-loaded holes. Stress intensity factors and crack opening displacements are calculated for various round compact specimens as a function of crack-length-to-specimen-width ratios. A wide-range equation for the stress intensity factors and equations for crack-surface displacements and load-point displacements are developed.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 17; Dec. 198
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  • 43
    Publication Date: 2011-08-18
    Description: A phenomenological load interaction model referred to as the Multi-Parameter Yield Zone model is presented which accounts for crack growth retardation caused by previous overloads, acceleration due to current overloads, and underload effects. In the present model, load interaction effects are calculated utilizing a residual stress intensity concept. Crack growth retardation and acceleration are accounted for by decreasing or increasing, respectively, the effective stress ratio used in a modified Forman's (1967) crack growth equation. Results of spectrum crack growth predictions for 2219-T851 aluminum are presented.
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  • 44
    Publication Date: 2011-08-18
    Description: The present paper is concerned with the development and application of an analytical model of cyclic crack growth that includes the effects of crack closure. The model was based on a concept like the Dugdale model, but was modified to leave plastically deformed material in the wake of the advancing crack tip. The model was used to correlate crack growth rates under constant-amplitude loading and to predict crack growth under aircraft spectrum loading on 2219-T851 aluminum alloy plate material. The predicted crack growth lives agreed well with experimental data. The ratio of predicted-to-experimental lives ranged from 0.66 to 1.48.
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  • 45
    Publication Date: 2011-08-18
    Description: A method for predicting fatigue crack growth under random loading which employs the concept of Barsom (1976) is presented. In accordance with this method, the loading history for each specimen is analyzed to determine the root-mean-square maximum and minimum stresses, and the predictions are made by assuming the tests have been conducted under constant-amplitude loading at the root-mean-square maximum and minimum levels. The procedure requires a simple computer program and a desk-top computer. For the eleven predictions made, the ratios of the predicted lives to the test lives ranged from 2.13 to 0.82, which is a good result, considering that the normal scatter in the fatigue-crack-growth rates may range from a factor of two to four under identical loading conditions.
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  • 46
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    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: (ISSN 0014-4851)
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  • 47
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    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture (ISSN 0376-9429); 22; June 198
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  • 48
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials (ISSN 0021-9983); 17; May 1983
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  • 49
    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2112, Accession no. A82-30182
    Keywords: STRUCTURAL MECHANICS
    Type: (ISSN 0001-1452)
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  • 50
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Res Mechanica (ISSN 0143-0084); 9; 2, 19; 1983
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  • 51
    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2111, Accession no. A82-30171
    Keywords: STRUCTURAL MECHANICS
    Type: (ISSN 0021-8669)
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  • 52
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2110, Accession no. A82-30166
    Keywords: STRUCTURAL MECHANICS
    Type: (ISSN 0001-1452)
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  • 53
    Publication Date: 2016-06-07
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Turbine Eng. Hot Sect. Technol. (HOST); p 181-193
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  • 54
    facet.materialart.
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    Publication Date: 2016-06-07
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Turbine Eng. Hot Sect. Technol. (HOST); p 195-204
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  • 55
    Publication Date: 2016-06-07
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 179-180
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  • 56
    Publication Date: 2016-06-07
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 175-177
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  • 57
    Publication Date: 2014-09-11
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 24 p
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  • 58
    Publication Date: 2014-09-11
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Alabama Univ. Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 34 p
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  • 59
    Publication Date: 2016-03-01
    Description: An algorithm is described for synthesizing the mass and stiffness matrices from experimentally derived modal data in a way that preserves the physical significance of the individual mass and stiffness elements. The mass and stiffness matrices are derived for a rollup solar array example, and are then used to define the modal response of a modified array.
    Keywords: STRUCTURAL MECHANICS
    Type: JPL Quart. Tech. Rev. ; Vol. 2; No. 3; p 12-21
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  • 60
    Publication Date: 2014-09-10
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: The Telecommun. and Data Acquisition Rept.; p 89-91
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  • 61
    Publication Date: 2011-08-18
    Description: Theoretical analysis is performed on the linear dynamic equations of thin cylindrical shells to find the error committed by making the Donnell assumption and the neglect of in-plane inertia. At first, the effect of these approximations is studied on a shell with classical simply supported boundary condition. The same approximations are then investigated for other boundary conditions from a consistent approximate solution of the eigenvalue problem. The Donnell assumption is valid at frequencies high compared with the ring frequencies, for finite length thin shells. The error in the eigenfrequencies from omitting tangential inertia is appreciable for modes with large circumferential and axial wavelengths, independent of shell thickness and boundary conditions.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 76; June 22
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  • 62
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    Publication Date: 2011-08-18
    Description: An analytical procedure for prediction of the cyclic plasticity effects on both the structural fatigue life to crack initiation and the rate of crack growth is presented. The crack initiation criterion is based on the Coffin-Manson formulae extended for multiaxial stress state and for inclusion of the mean stress effect. This criterion is also applied for the accumulated damage ahead of the existing crack tip which is assumed to be related to the crack growth rate. Three cyclic plasticity models, based on the concept of combination of several yield surfaces, are employed for computing the crack growth rate of a crack plane stress panel under several cyclic loading conditions.
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  • 63
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    Publication Date: 2011-08-18
    Description: An analysis method developed to calculate the wind loads on the nodes or joints of the truss type support structure of the 64 meter antenna is described. The method uses the CBAR element and GRID coordinate cards of the NASTRAN or IDEAS structural analysis programs as inputs to the computer model of the structure. Cross flow principles and vector analysis are also used in the analysis. The algorithms used are described and probable accuracy of the solution is discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: The Telecommun. and Data Acquisition; p 149-153
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  • 64
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    Publication Date: 2011-08-18
    Description: Time-dependent lateral deflection of flat rectangular plates is predicted by the Norton-Bailey (Norton 1929, Bailey 1935) power law for material creep. The plates have a through-thickness steady-state temperature distribution, and the effects are considered by using Maxwell's law to modify the power creep law. Equations are derived for creep exponents of 3 and 5, using the sandwich plate element to predict creep buckling of plates. Predictions of creep buckling with a temperature variation between the inner and outer plate surfaces are found to be somewhat dependent on the creep buckling relationship assumed. When significant scatter justifies a variation in the creep constants up to an order of magnitude, discrepancies in predictions using the two exponents are reasonable, and for one engineering material, the predictions have the same degree of agreement with experimental data as have the respective creep laws.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Thermal Stresses; 4; Apr. 198
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  • 65
    Publication Date: 2011-08-18
    Description: A general algorithm is developed to calculate the beam-type dynamic response of three dimensional multiplane finite length pipe systems, consisting of elbow and straight ducts with continuous interfaces. Emphasis is on secondary acoustic wave effects giving rise to coupling mechanisms; and the simulation accounts for one-dimensional elastoacoustic coupling from a plane acoustic wave and secondary loads resulting from wave asymmetries. The transfer matrix approach is adopted in modeling the elastodynamics of each duct, with allowance for distribution loads. Secondary loads from plane wave distortion are considered with a solution of the Helmholtz equation in an equivalent rigid waveguide, and effects of path imperfection are introduced as a perturbation from the hypothetical perfectly straight pipe. Computations indicate that the one-dimensional acoustic assumption is valid for frequencies below one-half the first cut-off frequency, and the three-dimensional acoustic effects produce an increase in response levels near and above cut-off.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 78; Sept. 8
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  • 66
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    Publication Date: 2011-08-18
    Description: An historical account is given of the development, from its conception in 1960, of the structural synthesis method. While synthesis techniques lag behind analytical ones in both sophistication and application, the structural design procedures created by combining finite element analysis and mathematical programming algorithms have progressed to the point of maturity. As in the case of finite element analysis, use and acceptance of structural synthesis methodology depends on the development and distribution of easily used and well-documented, production-quality computer programs. Attention is given such elementary applications of synthesis methods as the three-bar truss, an integrally stiffened waffle plate, a stiffened cylindrical shell, aircraft fuselage window panels, the structural efficiency of graphite-epoxy hat-stiffened panels, and an idealized delta wing.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 19; Oct. 198
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  • 67
    Publication Date: 2011-08-18
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 17; 3, 19; 1983
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  • 68
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2112, Accession no. A82-30186
    Keywords: STRUCTURAL MECHANICS
    Type: (ISSN 0001-1452)
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  • 69
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2108, Accession no. A82-30124
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1729-173
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  • 70
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 01, p. 60, Accession no. A83-10900
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 907-912
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  • 71
    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2109, Accession no. A82-30152
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 899-906
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  • 72
    Publication Date: 2011-08-18
    Description: Stress-intensity factors are obtained for twin collinear cracks emanating from a hole in an infinite plate. Point forces that tend to make the crack surfaces separate and slide are applied to one of the cracks. A conformal mapping and the Muskelishvili formulation involving series representation of the Kolosov stress functions are used to derive the solutions. The variation of stress-intensity factor with crack length and with point of application of the loads is presented for both crack tips.
    Keywords: STRUCTURAL MECHANICS
    Type: Res Mechanica Letters; 1; Dec. 198
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  • 73
    Publication Date: 2011-08-18
    Description: This paper presents an empirical stress-intensity factor equation for a surface crack as a function of parametric angle, crack depth, crack length, plate thickness and plate width for tension and bending loads. The stress-intensity factors used to develop the equation were obtained from a previous three-dimensional, finite-element analysis of semielliptical surface cracks in finite elastic plates subjected to tension or bending loads. A wide range of configuration parameters was included in the equation. The ratios of crack length to plate thickness and the ratios of crack depth to crack length ranged from 0 to 1.0. The effects of plate width on stress-intensity variations along the crack front were also included. The equation was used to predict patterns of surface-crack growth under tension or bending fatigue loads. The equation was also used to correlate surface-crack fracture data for a brittle epoxy material within + or - 10 percent for a wide range of crack shapes and crack sizes.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 15; 1-2,; 1981
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  • 74
    Publication Date: 2011-08-18
    Description: 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.
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  • 75
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    Publication Date: 2011-08-18
    Description: 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.
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  • 76
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The application of substructuring techniques are described for two example problems, a square plate and the static analysis of a frame-wall interaction problem in multistory structures. A DMAP routine for calculating the multipoint constraint forces is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences e; p 485-496
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  • 77
    Publication Date: 2016-06-07
    Description: A nuclear reactor vessel is supported by a Z-ring and a box ring girder. The two proposed structural configurations to transmit the loads from the Z-ring and the box ring girder to the foundation are shown. The cantilever concrete ledge transmitting the load from the Z-ring and the box girder via the cavity wall to the foundation is shown, along with the loads being transmitted through one of the six steel columns. Both of these two supporting systems were analyzed by using rigid format 9 of NASTRAN for dynamic loads, and the thermal stresses were analyzed by AXISOL. The six column configuration was modeled by a combination of plate and bar elements, and the concrete cantilever ledge configuration was modeled by plate elements. Both configurations were found structurally satisfactory; however, nonstructural considerations favored the concrete cantilever ledge.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experience; p 465-475
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  • 78
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    Publication Date: 2016-06-07
    Description: NASTRAN was chosen as the principal analytical tool for structural analysis of the Illinois Center Plaza Hotel Building in Chicago, Illinois. The building is a 40-story, reinforced concrete structure utilizing a monolithic slab-column system. The displacements, member stresses, and foundation loads due to wind load, live load, and dead load were obtained through a series of NASTRAN runs. These analyses and the input technique are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 421-427
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  • 79
    facet.materialart.
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The extent to which suitable solutions may be obtained for one physics problem and two engineering type problems is traced. NASTRAN appears to be a practical tool to solve one-group steady-state neutron diffusion equations. Transient diffusion analysis may be performed after new levels that allow time-dependent temperature calculations are developed. NASTRAN piecewise linear anlaysis may be applied to solve those plasticity problems for which a smooth stress-strain curve can be used to describe the nonlinear material behavior. The accuracy decreases when sharp transitions in the stress-strain relations are involved. Improved NASTRAN usefulness will be obtained when nonlinear material capabilities are extended to axisymmetric elements and to include provisions for time-dependent material properties and creep analysis. Rigid formats 3 and 5 proved to be very convenient for the buckling and normal-mode analysis of a nuclear fuel element.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 429-441
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  • 80
    Publication Date: 2016-06-07
    Description: The addition of discrete elements to NASTRAN poses significant interface problems with the level 15.1 assembly modules and geometry modules. Potential problems in designing new modules for higher-order parametric discrete elements are reviewed in both areas. An assembly procedure is suggested that separates grid point degrees of freedom on the basis of admissibility. New geometric input data are described that facilitate the definition of surfaces in parametric space.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 361-373
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  • 81
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The NASTRAN program output is discussed from a structural analysts point of view, and the simple modifications which were made to the program in order to improve it are also described. The convenience of the output for use in original design work is critically appraised and compared with the output from ASTRAL. It is shown that considerable hand calculation is necessary in order to extract useful load distribution data from the available NASTRAN output. For this reason, some effort was directed toward providing additional force output for the NASTRAN shear panel element.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 337-360
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  • 82
    Publication Date: 2016-06-07
    Description: The geometric and kinematic properties of the element are described, along with development of the matrices and vectors which characterize the element. The necessity for considering small deviations from element planeness is discussed, and the approach taken to account for these deviations is described. The improved accuracy over the existing quadrilateral membrane is indicated by a sample calculation for which an analytical solution is available from beam theory. For the same finite element idealization, the errors in maximum displacement and stress were significantly reduced.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences e; p 315-336
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  • 83
    Publication Date: 2016-06-07
    Description: Efforts to integrate NASTRAN into a complete structural analysis system for use by large airframe design projects are discussed. NASTRAN was implemented as a major finite element structural analysis program to determine the static and dynamic behavior of complete airframes, as well as structural components. This requires modifications and additions to NASTRAN, to communicate with an existing system, and to provide facilities needed to work within the integrated structural analysis. For this purpose, several special DMAP modules were developed and introduced into the CALAC version of the NASTRAN system.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 289-302
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  • 84
    Publication Date: 2016-06-07
    Description: A static and buckling analysis of the ATS-F&G spacecraft reflector support truss (RST) and bridge truss assembly using NASTRAN was conducted. The RST is fabricated from a new material, graphite fiber reinforced plastic. A comparison is made with the NASTRAN results and the results of a similar analysis conducted using the stardyne program. The results of an actual static load test are also compared.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences e; p 303-314
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  • 85
    Publication Date: 2016-06-07
    Description: Three finite element programs are compared to assess their capabilities as an analysis tool in a structural design process. Because of the need for repetitive analyses as an integral part of a design loop, a candidate program must be capable of handling large problems, operate efficiently, and be readily adaptable for use in computer-aided design. The three programs considered in the study, ELAS,SNAP, and NASTRAN, range from a relatively small finite element program limited to static structural analysis (ELAS) to a large complex general analysis system (NASTRAN). Results are given for comparative speeds and computer resources required for each program in the analysis of sample fuselage problems representative of practical aircraft design.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 277-287
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  • 86
    Publication Date: 2016-06-07
    Description: A static finite element stress analysis of an inflated radial car tire was carried out. The deformed shape of the sidewall presents outward bulging. The analysis of a homogeneous isotropic toroidal shell shows that the problem is common to all solids of this type. The study suggests that the geometric stiffness due to the inflation pressure has to be taken into account. Also, the resulting large displacements make it necessary for the geometry to be updated at each load step.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 263-276
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  • 87
    Publication Date: 2016-06-07
    Description: A composite element is presented which includes the effects of warping and offset shear centers. It is shown to be mathematically consistent with thin walled open beam theory and can be incorporated into any structural analysis program by use of NASTRAN'S standard elements. A numerical example analyzing the vibration of a channel beam is presented, and, by using the composite element, the numerical results agreed well with theoretical data.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 179-195
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  • 88
    Publication Date: 2016-06-07
    Description: A FORTRAN subroutine to NASTRAN which constructs coriolis and centripetal acceleration matrices, and a centrifugal load vector due to spin about a selected point or about the mass center of the structure is discussed. The rigid translational degrees of freedom can be removed by using a transformation matrix T and its explicitly given inverse. These matrices are generated in the subroutine and their explicit expressions are given.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 197-234
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  • 89
    Publication Date: 2016-06-07
    Description: The level 12 NASTRAN was used to support the NASA/LaRC advanced transport technology study, a predesign, short response time effort. Aeroelastic analyses were performed. NASTRAN calculated the vibration modes for the supported airfoil components and the entire unsupported vehicle. Other procedures were then used for the aeroelastic analysis, with procedure interfacing accomplished through use of the NASTRAN-produced restart tape. Stiffness matrices were used in static aeroelastic analyses; natural vibration modes were used for flutter and flight control system definition. Various level 12 NASTRAN characteristics were discovered and are discussed; e.g., the ability to solve singular matrices in rigid format 1, run times using multipoint constraints, restart tape problems, and the inaccurate stresses from the quad membrane when used with anisotropic materials.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 235-261
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  • 90
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    In:  CASI
    Publication Date: 2016-06-07
    Description: A lumped mass model was used to represent the impact condition between a fuel duct and an IVHM in-vessel fuel handling machine. The nonlinear effects of a Bellville spring and the free fall impact of the fuel duct on the IVHM were included. The purpose of the tests was to determine the loads on the fuel duct due to the impact. A comparison between experimental and theoretical results is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 161-178
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  • 91
    Publication Date: 2016-06-07
    Description: To evaluate the effectiveness of NASTRAN for predicting the vibration modes of panels with bending-membrane coupling, a cross-stiffened ship deck was analyzed. In correlation with experimental data, one NASTRAN finite element representation gave results slightly more accurate than a previous analytical solution. Computational time was excessively long, due to the Guyan method of reducing the eigenvalue problem. It is recommended that a more efficient method of matrix reduction be implemented for the lumped mass formulation.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 145-159
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  • 92
    Publication Date: 2016-06-07
    Description: Structural analysis applications of NASTRAN to the isogrid structure of the Delta launch vehicle are discussed. Isogrid is a method employed to stiffen the booster cylindrical shell surface by integrally machining ribs and skin from one piece of metal. The ribs are arranged in a repetitive equilateral triangular pattern; this results in a structural surface whose stiffness is orthogonally isotopic. For that structure, both static and general instability buckling analyses are described and the theoretical results are compared to test data. One of the parameters included in the analysis is the effect of pressure loadings on the buckling allowable load. In addition, a description of a supplementary computer program is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 121-143
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  • 93
    Publication Date: 2016-06-07
    Description: The coupling of NASTRAN to another finite element program developed for the static analysis of automotive structures is discussed. The two programs were coupled together to use the substructuring capability of the in-house program and the normal mode analysis capability of NASTRAN. Modifications were made to the NASTRAN program in order to make the coupling feasible.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 111-119
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  • 94
    Publication Date: 2016-06-07
    Description: For the improvement of rail service, the Department of Transportation, Federal Rail Administration, is sponsoring a test track on the Atchison, Topeka, and Santa Fe Railway. The test track will contain nine separate rail support structures, including one conventional section for control and three reinforced concrete structures on grade, one slab and two beam sections. The analysis and design of these latter structures was accomplished by means of the finite element method, NASTRAN, and is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 99-110
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  • 95
    Publication Date: 2016-06-07
    Description: An analytical study of a two-lobed circular arc pressure vessel (double-bubble tank) with a local perturbation from the cylindrical shape was made. It can be concluded that NASTRAN provides a good linear buckling analysis capability for structures that cannot be handled by other analysis techniques. However, solutions are relatively expensive from a computational standpoint. Two worthwhile additions to the NASTRAN program would be the inclusion of a new beam element that adequately represents the shear transfer when modeling stiffeners on a shell and the capability, in a rigid format, to keep certain prescribed loads constant during the eigenvalue extraction process.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 53-71
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  • 96
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The computer run time required for a buckling analysis using NASTRAN is considerably greater than for a linear static analysis of the same structure. It is very important to obtain an optimal model size for the structure being analyzed, such that the model is neither so large as to increase running time unnecessarily, nor so small as to hinder accuracy. The problem of critical load accuracy versus model complexity is considered for a thin walled cylinder, using both Level 12 and Level 15 NASTRAN releases.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 39-51
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  • 97
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The NASTRAN program was used to find the buckling location and the degradation factor due to a specified temperature field for an interstage of a typical three stage missile. The model was made up of 6332 independent degrees of freedom. This large size required the use of an IBM 370/195 for evaluation of the eigenvalues. The effect of elevated temperature was to lower the critical buckling load by 3%.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 29-38
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  • 98
    Publication Date: 2016-06-07
    Description: The buckling of isotropic and waffle-stiffened circular cylinders with and without cutouts was studied using NASTRAN's Rigid Format 5 for the case of axial compressive loading. The results obtained for the cylinders without cutouts are compared with available reference solutions. The results for the isotropic cylinders containing a single circular cutout with selected radii are compared with available experimental data. For the waffle-stiffened cyclinder, the effect of two diametrically opposed rectangular cutouts was studied. A DMAP alter sequence was used to permit the necessary application of different prebuckling and buckling boundary conditions. Advantage was taken of available symmetry planes to formulate equivalent NASTRAN model segments which reduced the associated computational cost of performing the analyses. Limitations of the applicability of NASTRAN for the solution of problems with nonlinear characteristics are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 73-97
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  • 99
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    In:  CASI
    Publication Date: 2016-06-07
    Description: Significant NASTRAN-related events since September, 1971 are reviewed. The present operation of the NASTRAN systems management office is described, as well as new capabilities and improvements incorporated in Level 15 of NASTRAN, and priorities for future levels of NASTRAN.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 1-11
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  • 100
    Publication Date: 2016-06-07
    Description: A summary of tests conducted on the Concorde aircraft nacelle structure is presented. The tests were conducted as a part of the structural development and certification program. The nacelle structural specimens are described. The problems associated with the intake testing and engine-bay and nozzle testing are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advanced Approaches to Fatigue Evaluations; p 649-665
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