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  • STRUCTURAL MECHANICS  (1.418)
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  • FLUID MECHANICS AND HEAT TRANSFER
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  • 1
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    The Capillary Pumped Loop (CPL) GAS experiment G-471 (1986)
    In:  CASI
    Details
    Publikationsdatum: 2009-11-16
    Beschreibung: The Capillary Pumped Loop (CPL) experiment, G-471 is a thermal control system with high density heat acquisition and transport capability. The CPL consists of two capillary pumped evaporators with integral heaters, a fluid loop charged with ammonia (NH3), a condenser plate (heat sink), and various control electronics. The purpose of the experiment is to demonstrate the capability of a capillary pumped system under zero gravity conditions for use in the thermal control of large scientific instruments, advanced orbiting spacecraft, and space station components.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: The 1985 Get Away Special Experimenter's Symposium; p 237-253
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  • 2
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    Thermocapillary flow and gaseous convection in microgravity: Results from GAS payload G-0518 (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-06-12
    Beschreibung: Thermocapillary flow and gaseous convection in microgravity were investigated in GAS payload G-0518 during Space Shuttle Mission 41-D. A cylinder of paraffin was supported and heated differentially from its ends to induce a melt from solid to liquid and drive thermocapillary flow in the resulting liquid phase. Laminar thermocapillary flow was observed in the liquid paraffin and found to show a transition to time-dependent oscillatory motion at a Marangoni number of about Ma = 34000 with a period of approximately T = 8 seconds. In addition, free convection in a gas in microgravity was observed for the first time. The gaseous convection was caused by the thermal and/or velocity boundary layers present at the heater-liquid interface. Oscillation occurred in the gaseous convection simultaneously with those in the liquid, implying the two are strongly coupled. The gaseous convection may be driven by coupled thermocapillary flow/thermal expansion convection or microgravity bouyancy convection.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Goddard Space Flight Center The 1985 Get Away Special Experimenter's Symposium; p 293-301
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  • 3
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    GAS payload no. G-025: Study of liquid sloshing behaviour in microgravity (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-06-12
    Beschreibung: The Get Away Special (GAS) G-025, which flew on shuttle Mission 51-G, examined the behavior of a liquid in a tank under microgravity conditions. The experiment is representative of phenomena occurring in satellite tanks with liquid propellants. A reference fluid in a hemispherical model tank will be subjected to linear acceleration inputs of known levels and frequencies, and the dynamic response of the tank liquid system was recorded. Preliminary analysis of the flight data indicates that the experiment functioned perfectly. The results will validate and refine mathematical models describing the dynamic characteristics of tank-fluid systems. This will in turn support the development of future spacecraft tanks, in particular the design of propellant management devices for surface tension tanks.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Goddard Space Flight Center The 1985 Get Away Special Experimenter's Symposium; p 165-176
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  • 4
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    Water ball collision (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-06-12
    Beschreibung: What happens if a stainless steel ball hits a water ball in the weightless space ot the Universe? In other words, it was the objective of our experiments in the Space to observe the surface tension of liquid by means of making a solid collide with a liquid. Place a small volume of water between 2 glass sheets to make a thin water membrane: the 2 glass sheets cannot be separated unless an enormous force is applied. It is obvious from this phenomenom that the surface tension of water is far greater than presumed. On Earth, however, it is impossible in most cases to observe only the surface tension of liquid, because gravity always acts on the surface tension. Water and stainless steel balls were chosen the liquid and solids for the experiments. Because water is the liquid most familiar to us, its properties are well known. And it is also of great interest to compare its properties on the Earth with those in the weightless space.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Goddard Space Flight Center The 1985 Get Away Special Experimenter's Symposium; p 81-84
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  • 5
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    Shuttle Continuous Open Wind Tunnel (SCOWT) (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The aerodynamic and heat transfer coefficients are studied within the range of thermo-fluid-dynamic conditions experienced by a satellite during Tethered Satellite System (TSS) atmospheric flights. The gasdynamic processes occuring downstream of the bow wave standing in front of the satellite are also studied. The knowledge of the chemistry and physics of the upper atmosphere related to satellite aerothermodynamics is furthered. The existence of an overshooting of the air drag coefficient of the sphere in the transition regime is validated. A complete set of measurements is performed in order to provide the data base to develop and validate theoretical models of free molecule transition flow fields.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA, Washington Applications of Tethers in Space. Workshop Proceedings, Vol. 2; p 225-249
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  • 6
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    Fluid behavior in microgravity (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-06-11
    Beschreibung: An experiment designed to study some fundamental aspects of microgravity fluid dynamics has been built and is scheduled for flight. The purpose of the experiment is to investigate differences in behavior of wetting and nonwetting fluid systems at low Bond numbers. Methods were developed to determine liquid quantity, estimate vapor contact area and measure liquid layer thickness. Both the responses of the fluid systems to external perturbations and the transfer of liquid through a connection between two containers can be studied.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Goddard Space Flight Center The 1985 Get Away Special Experimenter's Symposium; p 33-40
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  • 7
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    An analysis of ullage heat transfer in the orbital refueling system (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The Orbital Refueling System was an experiment flown on Shuttle Mission STS 41-G in October, 1984. Liquid hydrazine fuel was transferred back and forth from one spherical bladder tank to another using pressurized nitrogen as the driving force. Compressive heating of the ullage gas in the receiving tank could lead to a hazardous situation if any hydrazine leaked through to the ullage side of the bladder and was heated above about 175 F, where it can undergo spontaneous exothermic decomposition. Early analysis of the flight data indicated that the ullage compression process was much closer to an isothermal than an adiabatic one. In this study, a thorough review of the pertinent literature was used to make an a priori best-estimate for the ullage gas heat transfer coefficient (defining the Nusselt Number as a function of Reynolds and Rayleigh Numbers). Experimental data from the flight were analyzed in detail. It is evident that there is considerably more heat transfer than can be accounted for by conduction alone, but the observed increases do not correlate well with Reynolds Number, Rayleigh Number or vehicle acceleration. There are large gaps in the present understanding of convective heat transfer in closed containers with internal heat generation, especially in the presence of vibrations or other random disturbances. A program of experiments to fill in these gaps is suggested, covering both ground and orbital environments.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Johnson Space Center NASA/American Society for Engineering Educati; NASA. Johnson Space
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  • 8
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    Materials considerations in the design of a metal-hydride heat pump for an advanced extravehicular mobility unit (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: A metal-hydride heat pump (HHP) has been proposed to provide an advanced regenerable nonventing thermal sink for the liquid-cooled garment worn during an extravehicular activity (EVA). The conceptual design indicates that there is a potential for significant advantages over the one presently being used by shuttle crew personnel as well as those that have been proposed for future use with the space station. Compared to other heat pump designs, a HHP offers the potential for extended use with no electrical power requirements during the EVA. In addition, a reliable, compact design is possible due to the absence of moving parts other than high-reliability check valves. Because there are many subtleties in the properties of metal hydrides for heat pump applications, it is essential that a prototype hydride heat pump be constructed with the selected materials before a committment is made for the final design. Particular care must be given to the evaporator heat exchanger worn by the astronaut since the performance of hydride heat pumps is generally heat transfer limited.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Johnson Space Center NASA/American Society for Engineering Educati; NASA. Johnson Space
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  • 9
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    Condensation heat transfer under a microgravity environment (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: A description of the condensation heat transfer process in microgravity is given. A review of the literature is also reported. The most essential element of condensation heat transfer in microgravity is the condensate removal mechanism. Two mechanisms for condensate removal are analyzed by looking into two problems. The first problem is concerned with film condensation on a flat porous plate with the condensate being removed by suction at the wall. The second problem is an analytical prediction of the heat transfer coefficient for condensing annular flows with the condensate film driven by the vapor shear. It is concluded that both suction and vapor shear can effectively drain the condensate to ensure continuous operation of the condensers operated under a microgravity environment. It is recommended that zero-g flight experiments be carried out to verify the prediction made in the present report. The results contained in this report should also aid in the design of future space condensers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Johnson Space Center NASA/American Society for Engineering Educati; NASA. Johnson Space
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  • 10
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    Formulation of numerical procedures for dynamic analysis of spinning structures (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The paper presents the descriptions of recently developed numerical algorithms that prove to be useful for the solution of the free vibration problem of spinning structures. First, a generalized procedure for the computation of nodal centrifugal forces in a finite element owing to any specified spin rate is derived in detail. This is followed by a description of an improved eigenproblem solution procedure that proves to be economical for the free vibration analysis of spinning structures. Numerical results are also presented which indicate the efficacy of the currently developed procedures.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 23; 2347-235
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  • 11
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    Illustration of the use of modal assurance criterion to detect structural changes in an Orbiter test specimen (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The analysis of empirical modal models of structural components using techniques based on the modal assurance criterion (MAC) defined by Ewins (1984) is discussed and demonstrated for the case of the Space Shuttle Orbiter aft bulkhead. Modal models of the bulkhead are constructed before and after environmental acoustic tests equivalent to 30 or 100 missions and compared (by computing their MACs) to detect significant structural changes; subdivision of the modal vector followed by computation of the MAC for each part is used to localize the changes. Numerical data demonstrating the usefulness of the MAC approach are presented in tables and diagrams.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 12
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    Measurements of the cosmic background radiation (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Data on the cosmic microwave background radiation obtained with a maser at 12 mm and a Schottky diode mixer at 3 mm are presented. The dipole anisotropy, apparently due to our motion, has been measured sufficiently well to determine our direction of motion within two degrees. The results show that the Galaxy is moving in a direction that is about 44 deg from the center of the Virgo cluster.
    Schlagwort(e): SPACE RADIATION
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  • 13
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    Flow regimes in a shallow rotating cylindrical annulus with temperature gradients imposed on the horizontal boundaries (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Experimental flow regime diagrams are determined for a new rotating cylindrical annulus configuration which permits a measure of control over the internal vertical temperature gradient. The new annulus has radial temperature gradients imposed on plane horizontal thermally conducting endwalls (with the cylindrical sidewalls as insulators) and is considered to be more relevant to atmospheric dynamics studies than the classical cylindrical annulus. Observations have revealed that, in addition to the axisymmetric flow and nonaxisymmetric baroclinic wave flow which occur in the classical annulus, two additional nonaxisymmetric flow types occur in the new annulus: boundary-layer thermal convection and deep thermal convection. Flow regime diagrams for three different values of the imposed vertical temperature difference are presented, and explanations for the flow transitions are offered. The new annulus provides scientific backup for the proposed Atmospheric General Circulation Experiment for Spacelab. The apparatus diagram is included.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 172; 401-418
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  • 14
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    Global-local methodologies and their application to nonlinear analysis (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An assessment is made of the potential of different global-local analysis strategies for predicting the nonlinear and postbuckling responses of structures. Two postbuckling problems of composite panels are used as benchmarks and the application of different global-local methodologies to these benchmarks is outlined. The key elements of each of the global-local strategies are discussed and future research areas needed to realize the full potential of global-local methodologies are identified.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Finite Elements in Analysis and Design (ISSN 0168-874X); 2; 333-346
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  • 15
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    Design concepts/parameters assessment and sensitivity analyses of select composite structural components (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Formal approaches are summarized to evaluate design concepts and perform sensitivity analyses on design parameters of composite structural components for vehicles. The formal approaches include structural analyses coupled with composite micromechanics to assess the structural response of beams made from various intraply hybrids, finite element analysis in conjunction with composite mechanics to assess the structural response of panels made from strip hybrids, and sensitivity analysis through optimization to assess the effects of various design parameters on the optimum design of a panel made from angleplied composite laminates. Results obtained from these approaches are presented in graphical and tabular form to illustrate parametric studies and acceptable ranges of various design parameters.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Materials and Product Technology (ISSN 0268-1900); 1; 211-229
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  • 16
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    The special relativistic shock tube (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The shock-tube problem has served as a popular test for numerical hydrodynamics codes. The development of relativistic hydrodynamics codes has created a need for a similar test problem in relativistic hydrodynamics. The analytical solution to the special relativistic shock-tube problem is presented here. The relativistic shock-jump conditions and rarefaction solution which make up the shock tube are derived. The Newtonian limit of the calculations is given throughout.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 171; 365-375
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  • 17
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    Measurement and prediction of model-rotor flowfields (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 843-851
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  • 18
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    Scaling relations for heating during gliding entry at parabolic speed (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The scaling relations presently derived illustrate the influence of ballistic coefficient and L/D primary vehicle parameters on the peak heating rate and total heating/unit area for gliding entry of the earth atmosphere at parabolic speed. Comparisons with stagnation-point and windward centerline laminar and turbulent heating during three Space Shuttle flights are presented. It is found that total heat input/unit area is reduced by decreasing both of the primary vehicle parameters.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 2047-204
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  • 19
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    Damped response of shells by a constrained viscoelastic layer (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Vibration absorbers are introduced into an asymmetric configuration of thin cylinders and tori enclosing an acoustic medium. The absorbers consist of thin axial strips bonded to the cylinder with a thin viscoelastic layer. The constrained layer dissipates the energy of relative motions between strip and cylinder. The absorber is most effective on response modes with two or more circumferential waves. The use of transfer matrices is extended to the coupled cylinder-absorber system.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: ASME, Transactions, Journal of Applied Mechanics (ISSN 0021-8936); 53; 902-908
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  • 20
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    Arbitrarily laminated, anisotropic cylindrical shell under internal pressure (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An arbitrarily laminated, anisotropic cylindrical shell of finite length, under uniform internal pressure, is analyzed using Love-Timoshenko's kinematic relations and under the framework of classical lamination theory. The previously obtained solutions for asymmetrically laminated orthotropic (cross-ply) as well as unbalanced-symmetric and balanced-unsymmetric (angle-ply) cylindrical shells under the same loading conditions have been shown to be special cases of the present closed-form solution. Numerical results have been presented for a two-layer cylindrical shell and compared with those obtained using finite element solutions based on the layerwise constant shear-angle theory. These are expected to serve as benchmark solutions for future comparisons and to facilitate the use of unsymmetric lamination in design.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1851-185
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  • 21
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    Importance of anisotropy on buckling of compression-loaded symmetric composite plates (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1831-183
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  • 22
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    Nonlinear adhesive behavior effects in a cracked orthotropic sheet stiffened by a semi-infinite orthotropic sheet (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The stress-intensity factors are determined for a cracked orthotropic sheet adhesively bonded to an orthotropic stringer where the adhesive layer is modeled with a nonlinear stress-strain curve. By the use of Green's functions and the complex variable theory of orthotropic elasticity, a set of integral equations is obtained. The integral equations are replaced by an equivalent set of algebraic equations, which are solved to obtain the shear stress distribution in the adhesive layer, with which the crack-tip stress-intensity factors are found. When the adhesive was modeled with a nonlinear stress-strain curve, the peak shear stresses in the adhesive were considerably reduced in comparison to the solution for the linear elastic adhesive. This resulted in increases in the stress-intensity factors for the nonlinear adhesive solution compared to the linear adhesive solution. The nonlinear adhesive has no significant effect on the stress-intensity factor unless the near crack tip is beneath the stringer. It is assumed that the adhesive bond remains intact and it is predicted that onset of adhesive failure occurs at decreasing levels of applied stress as the crack propagates beneath the stringer.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Engineering Fracture Mechanics (ISSN 0013-7944); 25; 1, 19; 79-90
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  • 23
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    Quadratic resonance in the three-dimensional oscillations of inviscid drops with surface tension (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The moderate-amplitude, three-dimensional oscillations of an inviscid drop are described in terms of spherical harmonics. Specific oscillation modes are resonantly coupled by quadratic nonlinearities caused by inertia, capillarity, and drop deformation. The equations describing the interactions of these modes are derived from the variational principle for the appropriate Lagrangian by expressing the modal amplitudes to be functions of a slow time scale and by preaveraging the Lagrangian over the time scale of the primary oscillations. Stochastic motions are predicted for nonaxisymmetric deformations starting from most initial conditions, even those arbitrarily close to the axisymmetric shapes. The stochasticity is characterized by a redistribution of the energy contained in the initial deformation over all the degrees of freedom of the interacting modes.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 2788-279
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  • 24
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    Numerical experiments of axisymmetric flow in a nonuniform gravitational field (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1483-148
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  • 25
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    Is Navier-Stokes turbulence chaotic? (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Whether turbulent solutions of the Navier-Stokes equations are chaotic is considered. Initially neighboring solutions for a low-Reynolds-number fully developed turbulence are compared. The turbulence is sustained by a nonrandom time-independent external force. The solutions separate exponentially with time, having a positive Liapunov characteristic exponent. Thus the turbulence is characterized as chaotic.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 1453-145
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  • 26
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    Stress analysis method for a clearance-fit bolt under bearing loads (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1348-135
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  • 27
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    A theoretical model for the annular jet instability (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The instability of an annular gas-core liquid jet is modeled theoretically by treating the liquid layer as a membrane moving under the influences of its own inertia, surface tension, and the gaseous hydrostatic pressure difference between its two sides. Essential physical mechanisms are reconstructed without making any attempt to fit experimental data with model constants. The results compare favorably with those of experiment.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 2076-208
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  • 28
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    Experiments on annular liquid jet instability and on the formation of liquid shells (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An annular jet flow of liquid surrounding a flow of gas at its core is extremely unstable. Experiments are described in which such a flow is generated by an annular nozzle operated at fairly specific conditions. It is shown that periodic, axisymmetric oscillations arise spontaneously within the cylindrical sheet emerging from the nozzle and grow with such rapidity along the axial dimension that a sealing-off and encapsulation of the core gas occurs within a few jet diameters. This is closely followed by a pinchoff of the liquid between adjacent bubbles. The liquid shells set free thereby assume spherically symmetric form under capillary forces, and each contains a precisely uniform measure of gas and of liquid on account of the extremely high frequency-stability of the process. Description is given of the fluid dynamic processes by which the shells are formed, and mention is made of exploiting the instability for the production of rigid shells for technological applications.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 2086-209
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    Unified constitutive materials model development and evaluation for high-temperature structural analysis applications (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Unified constitutive material models were developed for structural analyses of aircraft gas turbine engine hot section components with particular application to an isotropic material used for combustor liners. Differential forms of models independently developed were considered in this study. These models combine the interactions of time-dependent (creep) and time-independent (plasticity) inelastic behavior of a material. Predicted stress-strain responses from these models were evaluated against cyclic isothermal and nonisothermal test results for uniaxial specimens of a nickel-base superalloy. The unified models were implemented in a nonlinear structural analysis code. Two unique NASA Lewis test facilities were used in the evaluation of the models for complex geometry specimens and evaluation of advanced temperature and high-temperature strain measurement instrumentation. Predicted nonlinear structural responses from one of the models for a flat plate and a segment of a conventional combustor liner are presented.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 30
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    Preliminary design of cracked-lap shear specimen thickness for determination of interlaminar fracture toughness (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper outlines a technique for preliminary sizing of the adherends for cracked-lap-shear specimen to assure delamination instead of adherend failure. The cracked-lap-shear specimen is a popular specimen used for determination of mixed mode interlaminar fracture toughness of composites. Thin adherends, on the order of three plies thick, have been used successfully in the past for determination of fracture toughness of rather brittle matrix systems. However, the tougher matrices now being considered for composite applications require thicker adherends in order to get composite delamination rather than adherend failure. The optimum thickness is obtained on the basis that the critical value of the strain energy release rate is reached at the delamination front before the ultimate strength is reached in the adherend. By proper design the specimen would delaminate and not use excessive material or load. A simple analysis for the optimum adherend thickness and experimental verification are included.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Composites Technology and Research (ISSN 0885-6804); 8; 58-60
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    Vibration of a large space beam under gravity effect (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Future space structures will have a low mass density and high flexibility, with ground test dynamic behavior differing significantly from that in zero-G orbit. Attention is presently given to the vibration behavior of a beam deformed by its own weight; the results obtained by the differential equations for both the static and dynamic responses of a large, simply supported beam, which are derived and solved analytically, allow ground test experiment measurements to be used for orbital dynamic characteristics verification efforts.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1213-121
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  • 32
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    Gravitino decay and the cosmic gamma-ray background (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is argued that the cosmic gamma-ray background (CGB) spectrum does not exhibit evidence for the decay of light gravitinos, in contradiction to the suggestion by Olive and Silk (1985), who observed a bump near 1 MeV in the CGB radiation spectrum. It is suggested that better fits to the CGB spectrum would be provided by mechanisms generating a power-law spectrum which is flattened below about 2 MeV. Olive and Silk maintain that the decays of a long-lived particle such as the gravitino may be responsible for features in the gamma-ray spectrum near 1 MeV.
    Schlagwort(e): SPACE RADIATION
    Materialart: Physical Review Letters (ISSN 0031-9007); 56; 2551; Au
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    Turbulent Reynolds analogy factors of stacked large-eddy breakup devices (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Direct measurements are made of turbulent Reynolds analogy factors, referenced to a flat plate, for turbulent boundary layer flows altered by stacked arrays of large eddy breakup devices (LEBUs). These are of interest as drag reducers when inserted into a boundary layer transverse to the flow. The data thus obtained furnish evidence that heat transfer, skin friction drag, and LEBU performance factors in low Reynolds number flows are sensitive to flow history. Attention is given to the apparatus and measurement procedures used.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 23; 348-350
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    Postbuckling analysis using a general-purpose code (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1013-102
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  • 35
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    Coupling conditions for integrating boundary layer and rotational inviscid flow (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The matching of a boundary layer and a rotational inviscid flow is reexamined by extending the Johnson and Sockol (1979) coupling conditions to include the case where the boundary layer solution includes the second-order effects of the freestream vorticity and the total temperature gradient. It is pointed out that two of the three conditions are not independent. If the boundary layer solution satisfies the appropriate momentum and energy integral equations, it follows that the imposition of the normal mass flux condition insures that the conditions on a normal flux of streamwise momentum and total enthalpy will also be satisfied.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1033-103
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    A new approach for solving the three-dimensional steady Euler equations. I - General theory (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The present iterative procedure combines the Clebsch potentials and the Munk-Prim (1947) substitution principle with an extension of a semidirect Cauchy-Riemann solver to three dimensions, in order to solve steady, inviscid three-dimensional rotational flow problems in either subsonic or incompressible flow regimes. This solution procedure can be used, upon discretization, to obtain inviscid subsonic flow solutions in a 180-deg turning channel. In addition to accurately predicting the behavior of weak secondary flows, the algorithm can generate solutions for strong secondary flows and will yield acceptable flow solutions after only 10-20 outer loop iterations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 60; 23-61
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  • 37
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    Numerical analysis of confined recirculating gas-solid turbulent flows (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Particle dispersion in confined recirculating turbulent flows has been investigated numerically. The present computational scheme utilizes Eulerian forms of the governing equations and allows two-way coupling between gas and solid phases. A recently developed two-phase closure model based on the multiple-scale turbulence model was used for the estimation of turbulent viscosities and diffusivities. For the particle size and loading considered in this study, the effect of particulate phase on the conveying gas is small, the nonequilibrium between the two phases is significant. Effects of recirculation, expanded chamber size and secondary annular jet momentum on the particle mixing rate are also investigated. In general, the present numerical results are in reasonably good agreement with the available experimental data.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 38
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    Fatigue delamination behavior of PEEK thermoplastic composite laminates (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The delamination resistance of graphite-reinforced PEEK composites was quantified by conducting static and cyclic edge delamination tests on (35n/-35n/0n/90n)s AS4/PEEK laminates, where n = 1, 2. The experimentally determined mechanical delamination onset strains were used to calculate the critical strain-energy release rate for delamination onset as a function of fatigue cycle. The delamination onset strains decreased dramatically with fatigue cycles and then began to level off to an endurance limit at 1 million cycles. Although the static interlaminar fracture toughness of the AS4/PEEK composite is much greater than the toughness of graphite epoxy composites, the delamination fatigue threshold, calculated from the cyclic strain endurance limit at 1 million cycles, was only slightly greater than the threshold for graphite epoxy composites. The contribution of residual thermal stresses to delamination in the AS4/PEEK is substantial due to the large temperature range between the manufacture and the room temperatures.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 39
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    Impact damage of composites (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A model is described for estimating the impact damage of fiber reinforced composite plates. The displacements and stresses are calculated by a three dimensional transient, finite element method of solution of the governing equations applicable to a linearly elastic body. The region in which damage occurs is estimated using the Tsai-Wu failure criterion. A computer code was developed which can be used to calculate the impact force, displacements and velocities of the plate and the impact body, stresses and strains in the plate, and the damage area. Sample numerical results are presented illustrating the type of information provided by the code. Comparisons between measured and calculated damage areas are also given.
    Schlagwort(e): STRUCTURAL MECHANICS
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    Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: In systems where the design inlet and outlet pressure P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Forced convection heat transfer to air/water vapor mixtures (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Heat transfer coefficients were measured using both dry air and air/water vapor mixtures in the same forced convection cooling test rig (jet array impingement configurations) with mass ratios of water vapor to air up to 0.23. The primary objective was to verify by direct experiment that selected existing methods for evaluation of viscosity and thermal conductivity of air/water vapor mixtures could be used with confidence to predict heat transfer coefficients for such mixtures using as a basis heat transfer data for dry air only. The property evaluation methods deemed most appropriate require as a basis a measured property value at one mixture composition in addition to the property values for the pure components.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Implicit solution methods in computational fluid dynamics (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A class of implicit finite difference schemes of the Beam and Warming approximate factorization type will be addressed. The development and analysis of various aspects of this class of schemes will be given along with the motivations behind many of the choices. Various acceleration and efficiency modifications such as matrix reduction, diagonalization and flux split schemes will be presented. The methods are demonstrated in fully vectorized codes for a CRAY type architecture. The emphasis will be on the Euler equations in generalized coordinates.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Applied Numerical Mathematics (ISSN 0168-9274); 2; 441-474
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    Distribution of resistive body-force in curved free-surface flow (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The customary procedure for including resistive effects in turbulent hydraulic and stratified atmospheric flows is to integrate the empirically-known boundary shears over the entire wetted boundary of a thin fluid slab. A resistive body-force is then assumed to exist everywhere in each slab to replace the boundary shearing force. For the classical Saint-Venant (1871) model, this body-force can be shown to have a constant distribution in the vertical direction, and therefore can be evaluated for use in the momentum differential equation. In the newer Dressler theory (1978), however, for unsteady flow over curved beds, it is proved here that a constant body-force distribution is not possible. Its variable distribution is determined as well as its magnitude for use in the curved-flow equations. This variable distribution acts to produce an equal resultant in every thin layer of fluid parallel to the bed in an angular wedge over the curved channel bed. The new curved-flow equations are therefore extended to include resistive effects.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Mathematical Methods in the Applied Sciences (ISSN 0170-4214); 8; 4, 19; 492-501
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    On the free vibrations of spinning paraboloids (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The dynamic behavior of a spinning linear-elastic paraboloid subject to nonaxisymmetric deformation is investigated analytically, applying the Rayleigh-Ritz procedure described by Utku et al. (1983). Energy-density, strain-displacement, and velocity-displacement expressions are generated; expressions for the generalized strain and position vector are derived; and the discretized dynamic equations are obtained. Numerical results obtained with a computer-program implementation of the method are presented in extensive tables and graphs. The effects of spin rate and bending rigidity and results for the special case of a spinning disk are included.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration (ISSN 0022-460X); 111; 279-296
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  • 45
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    Average transverse momentum and energy density in high-energy nucleus-nucleus collisions (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Emulsion chambers were used to measure the transverse momenta of photons or pi(0) mesons produced in high-energy cosmic-ray nucleus-nucleus collisions. A group of events having large average transverse momenta has been found which apparently exceeds the expected limiting values. Analysis of the events at early interaction times, of the order of 1 fm/c, indicates that the observed transverse momentum increases with both rapidity density and energy density.
    Schlagwort(e): SPACE RADIATION
    Materialart: Physical Review Letters (ISSN 0031-9007); 57; 3249-325
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  • 46
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    Numerical study of sink-flow boundary layers (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Direct numerical simulations of sink-flow boundary layers, with acceleration parameters K between 1.5 x 10 to the -6th and 3.0 x 10 to the -6th, are presented. The three-dimensional, time-dependent Navier-Stokes equations are solved numerically, using a spectral method, with about one million degrees of freedom. The flow is assumed to be statistically steady, and self-similar. A multiple-scale approximation and periodic conditions are applied to the fluctuations. The turbulence is studied using instantaneous and statistical results. Good agreement with the experiments of Jones and Launder (1972) is observed. The two effects of the favorable pressure gradient are to extend the logarithmic layer, and to alter the energy balance of the turbulence near the edge of the boundary layer. At low Reynolds number the logarithmic layer is shortened and slightly displaced, but wall-layer streaks are present even at the lowest values of R(theta) for which turbulence can be sustained. Large quiescent patches appear in the flow. Relaminarization occurs at K = 3.0 x 10 to the -6th, corresponding to a Reynolds number R(theta) of about 330.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 172; 307-328
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    Application of multiple objective optimization techniques to finite element model tuning (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This report examines tuning a finite element model using vector optimization techniques. Structural models using finite element theory often need to be adjusted so they can accurately simulate the real structure. The goal is to tune the model such that it will reproduce data derived from structural tests. First, the performance indices are extremized using multiple objective optimization theory, producing a set of possible solutions. Next, the solutions are rank ordered according to a decision maker's preferences to select the best answer. The tuning process was applied to a T-38 horizontal stabilizer. Numerous weighted solutions contained a best static deformation model, a best frequency model and three intermediate combinations of these two models. This automated procedure proved to be a versatile method capable of producing solutions for many types of tuning problems.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures (ISSN 0045-7949); 24; 5, 19
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    On the possibility of diffusionally driven oscillations in two component gas bubbles in fluids (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The problem of an isolated, stationary, two-component gas bubble in a fluid is analyzed. The appropriate governing equations, and an approximate version of these equations, for this model system are reviewed. The qualitative differences in bubble dissolution behavior between single- and two-component gas bubbles are elucidated. In particular, it is demonstrated that in the latter case the gas bubble radius may exhibit extrema as a function of time for certain values of the controlling parameters. The conditions under which these extrema may occur, and the maximum number of extrema which are permitted are elucidated.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Chemical Engineering Science (ISSN 0009-2509); 41; 9, 19; 2333-234
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    Re-examination of cumulative fatigue damage analysis - An engineering perspective (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A method which has evolved in the laboratories for the past 20 yr is re-examined with the intent of improving its accuracy and simplicity of application to engineering problems. Several modifications are introduced both to the analytical formulation of the Damage Curve Approach, and to the procedure for modifying this approach to achieve a Double Linear Damage Rule formulation which immensely simplifies the calculation. Improvements are also introduced in the treatment of mean stress for determining fatigue life of the individual events that enter into a complex loading history. While the procedure is completely consistent with the results of numerous two level tests that have been conducted on many materials, it is still necessary to verify applicability to complex loading histories. Caution is expressed that certain phenomenon can also influence the applicability - for example, unusual deformation and fracture modes inherent in complex loading especially if stresses are multiaxial. Residual stresses at crack tips, and metallurgical factors are also important in creating departures from the cumulative damage theories; examples of departures are provided.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Engineering Fracture Mechanics (ISSN 0013-7944); 25; 5-6,; 539-571
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    Oscillations of a viscous compound drop (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The effect of viscosity on normal mode oscillations of a compound drop is determined for a range of values of the viscosity, and the effect of a host medium is considered. The general form of the dispersion relation is derived, and numerical values are obtained for the case of an annular liquid region composed of silicon oil and with the core and host regions taken to be air. Results indicate that the sloshing mode of the compound drop is more damped than the bubble mode.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 3481-348
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    Exact Bernoulli-Euler static stiffness matrix for a range of tapered beam-columns (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The static stiffnesses for torsional and flexural deformation of a tapered beam under axial loading are determined analytically, extending the Bernoulli-Euler/Bessel-function approach of Banerjee and Williams (1985). The derivation of the expressions is explained in detail, and numerical results for sample problems are presented in tables and shown to be in excellent agreement with those obtained using stepped beams of 400 or 500 elements.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 23; 1615-162
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    Multiple-scale turbulence model in confined swirling jet predictions (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A recently developed multiple-scale turbulence model which attempts to circumvent the deficiencies of earlier models by taking nonequilibrium spectral energy transfer into account is presented. The model's validity is tested by predicting the confined swirling coaxial jet flow in a sudden expansion. It is noted that, in order to account for anisotropic turbulence, a full Reynolds stress model is required.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1717-171
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    Modeling of transition and surface roughness effects in boundary-layer flows (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Experiments were carried out to examine the influence of three-dimensional, stochastic roughness on the growth of incompressible turbulent boundary layers, as well as the effect of streamwise pressure gradients and freestream turbulence intensity on smooth-wall boundary-layer transition. The modeling of these effects in a two-dimensional boundary-layer computation program was examined with the help of the experiments. A model for surface roughness was developed that relates directly measurable statistical parameters quantifying the roughness geometry to the aerodynamic effects. This model should be valid for a limited class of surfaces found on turbomachinery blading and in other engineering applications. Commonly used criteria for the transition onset performed poorly and presumably need to be modified to account for other factors influencing the process.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1642-164
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    Criterion for mixed mode fracture in composite bonded joints (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A study was undertaken to characterize the debond growth mechanism of adhesively bonded composite joints under mode I, mixed mode I-II, and mode II static loadings. The bonded system consisted of graphite/epoxy (T300/5208) composite adherends bonded with a toughened epoxy (EC 3445) adhesive. The mode I, mode II and mixed-mode I-II fracture energies of the tested adhesive were found to be equal to each other. Furthermore, the criterion for mixed mode fracture in composite bonded joints was determined.
    Schlagwort(e): STRUCTURAL MECHANICS
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    Elastic analysis of a mode II fatigue crack test specimen (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Elastic displacements and stress intensity measurements for a mode II specimen have been obtained over a range of a/W values between 0.500 and 0.900 using the MARC general purpose finite element program. Stress intensity factors were experimentally determined using load point displacement values. Good general agreement between numerical and experimental results for crack mouth, crack surface, and load point displacements, and for stress intensity factors, demonstrates the accuracy of the present method.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Fracture (ISSN 0376-9429); 31; 151-157
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    On control of stresses in silicon web growth (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: It has been observed that the residual stresses and dislocations during the silicon crystal growth for photovoltaic applications are caused by thermal stresses. The temperatures along the boundaries of the silicon crystal ribbon are prescribed to meet the requirements of the crystal growth. It is shown that by allowing the temperatures to satisfy a second-order partial differential equation in the ribbon, all thermal stresses, and others induced by them, may be eliminated for the stress-free growth of the silicon crystal.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures (ISSN 0045-7949); 23; 5, 19; 657-664
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    Large volume water sprays for dispersing warm fogs (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A new method for dispersing of warm fogs which impede visibility and alter schedules is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray-induced air flow; the fog droplets are removed by coalescence/rainout. The efficiency of this fog droplet removal process depends on the size spectra of the spray drops and optimum spray drop size is calculated as between 0.3-1.0 mm in diameter. Water spray tests were conducted in order to determine the drop size spectra and temperature response of sprays produced by commercially available fire-fighting nozzles, and nozzle array tests were utilized to study air flow patterns and the thermal properties of the overall system. The initial test data reveal that the fog-dispersal procedure is effective.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Liquid fuel spray processes in high-pressure gas flow (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Atomization of single liquid jets injected downstream in high pressure and high velocity airflow was investigated to determine the effect of airstream pressure on mean drop size as measured with a scanning radiometer. For aerodynamic - wave breakup of liquid jets, the ratio of orifice diameter D sub o to measured mean drop diameter D sub m which is assumed equal to D sub 32 or Sauter mean diameter, was correlated with the product of the Weber and Reynolds numbers WeRe and the dimensionless group G1/square root of c, where G is the gravitational acceleration, 1 the mean free molecular path, and square root of C the root mean square velocity, as follows; D sub o/D sub 32 = 1.2 (WeRe) to the 0.4 (G1/square root of c) to the 0.15 for values of WeRe 1 million and an airstream pressure range of 0.10 to 2.10 MPa.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Application of the method of lines for solution of the Navier-Stokes equations using nonuniform grid distributions (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The method of lines is investigated for the numerical solution of the stream function and velocity form of the Navier-Stokes equations on nonuniform grids. Stiffness characteristics of a linear one-dimensional model equation are examined to establish the feasibility of applying the method to the volicity equation in two dimensions. It is observed that the transformed governing equations in computational domain become stiffer with increasing the number of grid points and the differencing technique affects the stiffness characteristics. The results demonstrate that the method of lines under certain circumstances is highly suitable for the numerical solution of physical problems on domains covered with variable grids.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    On mixed and displacement finite element models of a refined shear deformation theory for laminated anisotropic plates (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An improved plate theory that accounts for the transverse shear deformation is presented, and mixed and displacement finite element models of the theory are developed. The theory is based on an assumed displacement field in which the inplane displacements are expanded in terms of the thickness coordinate up to the cubic term and the transverse deflection is assumed to be independent of the thickness coordinate. The governing equations of motion for the theory are derived from the Hamilton's principle. The theory eliminates the need for shear correction factors because the transverse shear stresses are represented parabolically. A mixed finite element model that uses independent approximations of the displacements and moments, and a displacement model that uses only displacements as degrees of freedom are developed. A comparison of the numerical results for bending with the exact solutions of the new theory and the three-dimensional elasticity theory shows that the present theory (and hence the finite element models) is more accurate than other plate-theories of the same order.
    Schlagwort(e): STRUCTURAL MECHANICS
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    Computational solid mechanics (finite elements and boundary elements) - Present status and future directions (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Computational finite-element and boundary-element methods are reviewed, and their application to the mechanics of solids is discussed. Stability conditions for general FEMs are considered in addition to the use of least-order, stable, invariant, or hybrid/mixed isoparametric elements as alternatives to the displacement-based isoparametric elements. The use of symbolic manipulation, adaptive mesh refinement, transient dynamic response, and boundary-element methods for linear elaslticity and finite-strain problems of inelastic materials are also discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
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    Computation of nonstationary strong shock diffraction by curved surfaces (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A two-dimensional, high resolution shock-capturing algorithm was used on a supercomputer to solve Eulerian gasdynamic equations in order to simulate nonstationary strong shock diffraction by a circular arc model in a shock tube. The hypersonic Mach shock wave was assumed to arrive at a high angle of incidence, and attention was given to the effect of varying values of the ratio of specific heats on the shock diffraction process. Details of the conservation equations of the numerical algorithm, written in curvilinear coordinates, are provided, and model output is illustrated with the results generated for a Mach shock encountering a 15 deg circular arc. The sample graphics include isopycnics, a shock surface density profile, and pressure and Mach number contours.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Nonlinear critical layers eliminate the upper branch of spatially growing Tollmien-Schlichting waves (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This letter is concerned with the effect of nonlinear critical layers on spatially growing Tollmien-Schlichting waves in a Blasius boundary layer. It is shown that they effectively eliminate the upper branch of the neutral stability curve predicted by strictly linear theory.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 2344
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    The generation of capillary instabilities on a liquid jet (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The coupling between imposed disturbances and capillary instabilities on a liquid jet is examined. It is shown that in most physical situations the forcing produces neutral waves, which can then turn into growing waves as the profile relaxes or may be amplified nonlinearly by a mechanism of the type considered by Akylas and Benney (1980). The effectiveness of the coupling is expressed quantitatively by numerically computed values of the 'coupling coefficient'.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 168; 479-500
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    On symmetric and upwind TVD schemes (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The performance of the upwind and symmetric total variation diminishing (TVD) schemes in viscous and inviscid airfoil steady-state calculations is considered, and the extension of the implicit second-order-accurate TVD scheme for hyperbolic systems of conservative laws in curvilinear coordinates is discussed. For two-dimensional steady-state applications, schemes are implemented in a conservative noniterative alternating direction implicit form, and results illustrate that the algorithm produces a fairly good solution for an RAE2822 airfoil calculation. The study demonstrates that the symmetric TVD scheme is as accurate as the upwind TVD scheme, while requiring less computational effort than it.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Higher-order flux difference splitting schemes for the Euler equations using upstream interpolations (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A class of explicit two time-level, 2p + 1 space-point, (2p 1)-th order, upwind-biased flux difference splitting schemes are proposed for the numerical advection based on Lagrange's interpolation, and the method is an accord with the physical domain of dependence. A normalized Jacobian coefficient matrix is introduced to convert the schemes to hyperbolic systems of conservation laws, and approaches to make the higher-order schemes total variation stable are discussed. Accuracy and stability of the present schemes are examined, and implicit total variation diminishing schemes are developed for steady-state calculations.Application to gasdynamic problems for both steady and unsteady flows covering a wide range of Mach numbers is considered, and results for a blast wave passing a cylinder, and head-on collision of two blast waves over a circular arc, are presented. The flow patterns were found to be symmetric, and good resolution of flow structures was obtained.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Thermal response of integral, multicomponent composite thermal protection systems (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 23; 420-427
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    Enhancement of high-energy cosmic-ray spectrum by type-II supernovae (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The cosmic-ray spectrum has an intensity enhancement in the energy range 10 to the 14th to 10 to the 16th eV per nucleus. Recent observations of heavy cosmic rays in this energy range indicate that the Ca/Fe ratio may be as large as 10 times the solar value. It is suggested that pulsars in type-II supernova remnants are the origin of this component of the cosmic-ray spectrum.
    Schlagwort(e): SPACE RADIATION
    Materialart: Nature (ISSN 0028-0836); 321; 839-841
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    Sensitivity analysis of discrete structural systems (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Methods for calculating sensitivity derivatives for discrete structural systems are surveyed, primarily covering literature published during the past two decades. Methods are described for calculating derivatives of static displacements and stresses, eigenvalues and eigenvectors, transient structural response, and derivatives of optimum structural designs with respect to problem parameters. The survey is focused on publications developed in nonstructural fields such as electronics, controls, and physical chemistry which are directly applicable to structural problems. Most notable among the nonstructural-based methods are the adjoint variable technique from control theory, and the Green's function and FAST methods from physical chemistry.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 823-832
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    Convective and absolute instability of a viscous liquid jet (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The effect of viscosity on the capillary instability of a liquid jet is examined. The critical Weber number for convective instability is determined as a function of Reynolds number and comparison is made with the inviscid limit. It is shown that certain waves that are neutral in the inviscid case exhibit growth for finite Reynolds numbers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 952-954
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    The effect of the heliospheric current sheet on cosmic ray intensities at solar maximum - Two alternative hypotheses (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The capabilities of two alternative models for accounting for the reversal of the solar magnetic field polarity at the point of solar maximum and for the associated modulation of cosmic ray intensities at 1 AU are assessed. One model posits a continuous increase in the inclination of the heliospheric current sheet to a point of verticality at maximum, when it overturns and the reversal occurs. The alternative view is that the sun sheds the magnetic field of the previous cycle and generates a new field of opposite polarity. Some data do exist for a tilted current sheet which increases its tilt with proximity to the solar maximum. However, coronal data also support the presence of isolated regions of anomalous polarity which spread over the surface of the sun as maximum approaches, a condition commensurate with flux shedding. Both models predict heliospheric current sheet configurations which would produce some cosmic ray modulations observed over the course of the solar cycle.
    Schlagwort(e): SPACE RADIATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; 2889-289
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    Free boundary shape of a convectively cooled solidified region (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The two-dimensional steady-state shape of a solidified region, such as a frost layer, was determined analytically for formation on a plate that is convectively cooled. The nonuniform shape of the layer is produced by exposure to a spatially nonuniform distribution of radiant energy. For high convective cooling the cooled wall approaches a uniform temperature, and an exact solution is obtained for the free boundary shape. For a lesser amount of convective cooling, the variation in temperature along the cooled boundary is treated by a boundary perturbation method. Some illustrative examples are given that show the effects of nonuniform heating and the magnitude of convective heat transfer at the cooled wall. Only one boundary condition is approximated by the perturbation solution; all of the other boundary conditions are satisfied exactly. The calculated results given here were found to satisfy the approximate boundary condition within a very small error.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 29; 309-315
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    References and conference proceedings towards the understanding of fracture mechanics (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A list of books, reports, periodicals, and conference proceedings, as well as individual papers, centered on specific aspects of fracture phenomenon has been compiled by the ASTM Committee E-24 on Fracture Testing. A list of basic references includes the articles on the development of fracture toughness, evaluation of stress intensity factors, fatigue crack growth, fracture testing, fracture of brittle materials, and fractography. Special attention is given to the references on application of fracture mechanics to new designs and on reevaluation of failed designs, many of them concerned with naval and aircraft structures.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Testing and Evaluation (ISSN 0090-3973); 14; 61-75
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    Boundary perturbation method for free boundary problem in convectively cooled continuous casting (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Novel mathematical techniques are here used to treat general boundary conditions in convectively cooled continuous ingot casting problems, applying a constant convective heat transfer coefficient at the ingot sides (so that the temperature distribution along the sides is unknown). The problem is first inverted to treat the physical coordinates as dependent variables of temperature and heat flow, mapping the ingot into a region that is nearly rectangular. A boundary perturbation method is then used to obtain an analytical solution in this near-rectangular region. Solidification interface shapes depend on two dimensionless parameters: one is a function of the casting velocity, while the other is dependent on the convective heat transfer coefficient at the cooled wall.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 108; 230-234
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    Inclusion of elastically connected members in exact buckling and frequency calculations (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A standard stiffness matrix procedure which permits any combination of rigid, elastic, pinned or sliding connections of the degrees of freedom at the ends of a member to the nodes of its parent structure is described, in order to show how easily it can be extended to allow an existing algorithm to be used to ensure that no eigenvalues of the parent structure can be missed even when 'exact' member theory is used. The eigenvalues are the natural frequencies of undamped free vibration analyses or the critical load factors of buckling problems. The method preserves the exactness of the member theory and an efficient method for computer application is indicated. The theory also permits any combination of rigid, elastic, pinned or sliding connections between the freedoms of a substructure and those of its parent structure.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures (ISSN 0045-7949); 22; 3, 19
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    A simple rectangular element for two-dimensional analysis of laminated composites (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A simple rectangular finite element was developed for two-dimensional analysis of laminated composite materials. The rectangular laminated composite element eliminates the need to add elements to a model simply to account for the material properties of various laminae. This is particularly advantageous for thick laminates with many lamina. Explicit integration in terms of generalized displacements minimizes the algebraic effort required to derive the element stiffness and the thermal load vector. A substitute shape function technique is used to improve the performance of the element in modeling bending type deformation. Results for several example problems are discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures (ISSN 0045-7949); 22; 3, 19; 387-393
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    Secondary antiproton production in relativistic plasmas (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Angular and energy spectra of bremsstrahlung have been calculated from anisotropic electron distributions in solar flares. Results have been compared to observations of gamma-ray limb-brightening and the data on the variation of the gamma-ray spectrum with flare position on the sun.
    Schlagwort(e): SPACE RADIATION
    Materialart: Nature (ISSN 0028-0836); 319; 205
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    Observations of cosmic gamma-ray bursts (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Recent observational progress in gamma ray burst research is reviewed. Findings concerning burst temporal and spectral characteristics, source direction and size spectrum studies, and transient event classification are discussed. The theories concerning the origin of the bursts are examined in the light of the recent evidence.
    Schlagwort(e): SPACE RADIATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 6; 4, 19
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    Proton acceleration in gamma-ray bursts (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Proton acceleration and subsequent secondary electron production are proposed as the process responsible for the radiation emission in gamma-ray bursts. In this mechanism electrons are naturally injected at energies much larger than m(e) x c-squared and emission above 10 MeV is expected to be one of their common features, in agreement with observations showing that most of the luminosity of these events is emitted in gamma-rays. This mode of injection guarantees copious e(+)-e(-) pair production at the source and implies a relationship between the luminosity and the spectra of the bursts, the soft bursts being, in general, the most (intrinsically) luminous and hence the most distant. This, in turn, implies that bursts with soft spectra should show a galactic distribution, a fact consistent with the limited available data. It is also argued that the observed red-shift of the e(+)-e(-) annihilation feature may not always be gravitational.
    Schlagwort(e): SPACE RADIATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 6; 4, 19
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    An experimental study using flow visualization on the effect of an acoustic field on heat transfer from spheres (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The physical mechanisms responsible for the heat transfer process in a thermal-acoustic field were investigated using the technique of holographic interferometry for flow visualization. Experimental results were obtained with sound pressure levels in the range of 120 to 150 decibels, relative to a pressure of 0.0002 dynes/sq cm. Steady state laminar flow was observed when the vibrational Reynolds number was below 400; separated flow was observed when it was above 400. In the presence of a horizontal sound field, the data indicate that the relation between the vibrational Nusselt number, Nu(v) and the vibrational Reynolds number, Re(v) is given by Nu(v) = Re(v) exp 0.22. In the presence of a vertical sound field, the corresponding relation is Nu(v) = Re(v) exp 0.15.
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    A higher order theory of laminated composite cylindrical shells (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A new higher order theory has been proposed for the analysis of composite cylindrical shells. The formulation allows for arbitrary variation of inplane displacements. Governing equations are presented in the form of a hierarchy of sets of partial differential equations. Each set describes the shell behavior to a certain degree of approximation. The natural frequencies of simply-supported isotropic and laminated shells and stresses in a ring loaded composite shell have been determined to various orders of approximation and compared with three dimensional solutions. These numerical studies indicate the improvements achievable in estimating the natural frequencies and the interlaminar shear stresses in laminated composite cylinders.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Aeronautical Society of India, Journal (ISSN 0001-9267); 38; 161-171
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    Turbulence modeling (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A survey designed to provide an introduction to the subject of turbulence modeling, and to explain the need for such models is given. The subject is developed along chronological lines since this provides a logical development plan and also because it then moves from relatively simple phenomenological models through more complicated procedures and ultimately to the subject of large-eddy simulation.
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    Turbulent solutions of the Navier-Stokes equations (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Analytical and numerical approaches to the mechanics of turbulent flow are examined in a general introduction and illustrated with graphs. Topics discussed include the averaged and unaveraged basic equations, numerical solutions and methods, homogeneous fluctuations and turbulence with no mean flow, uniformly sheared fluctuations and turbulence, inhomogeneous fluctuations and turbulence in a developing shear layer, and steady-state homogeneous turbulence with a spatially periodic body force.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Volume-energy parameters for heat transfer to supercritical fluids (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Unsteady heat transfer and direct comparison to steady-state measurements in a rotor-wake experiment (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Circumferentially local and time-resolved heat transfer measurements were obtained for a circular cylinder in crossflow located downstream of a rotating spoked wheel wake generator in a steady flow tunnel. The unsteady heat transfer effects were obtained by developing an extension of a thin film gauge technique employed to date exclusively in short-duration facilities. The time-average thin film results and conventional steady-state heat transfer measurements were compared. Time-averaged wake-induced stagnation heat transfer enhancement levels above the nowake case were about 10 percent for the four cylinder Reynolds numbers. This enhancement level was nearly independent of bar passing frequency and was related directly to the time integral of the heat transfer spikes observed at the bar passing frequency. It is observed that the wake-induced heat transfer spikes have peak magnitudes averaging 30 to 40 percent above the interwake heat transfer level.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Calculation of confined swirling jets (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Computations of a confined coaxial swirling jet are carried out using a standard two-equation (k-epsilon) model and two modifications of this model based on Richardson-number corrections of the length-scale (epsilon) governing equation. To avoid any uncertainty involved in the setting up of inlet boundary conditions, actual measurements are used at the inlet plane of this calculation domain. The results of the numerical investigation indicate that the k-epsilon model is inadequate for the predictions of confined swirling flows. Although marginal improvement of the flow predictions can be achieved by these two corrections, neither can be judged satisfactory.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Communications in Applied Numerical Methods (ISSN 0748-8025); 2; 333-338
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  • 87
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    Anisotropy of the cosmic blackbody radiation (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation - bumpiness on the sky at angular scales of about 10 arc minutes. They have not been seen.
    Schlagwort(e): SPACE RADIATION
    Materialart: Science (ISSN 0036-8075); 232; 1517-152
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  • 88
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    Viscoplasticity based on overstress with a differential growth law for the equilibrium stress (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Two coupled, nonlinear differential equations are proposed for the modeling of the elastic and rate (time) dependent inelastic behavior of structural metals in the absence of recovery and aging. The structure of the model is close to the unified theories but contains essential differences. It is shown that the model reproduces almost elastic regions upon initial loading and in the unloading regions of the hysteresis loop. Under loading, unloading and reloading in strain control the model simulated the experimentally observed sharp transition from nearly elastic to inelastic behavior. When a formulation akin to existing unified theories is adopted the almost elastic regions reduce the points and the transition upon reloading is very gradual. For different formulations the behavior under sudden in(de)creases of the strain rate by two orders of magnitude is simulated by numerical experiments and differences are noted. The model represents cyclically neutral behavior and contains three constants and two positive, decreasing functions. The determination of constants and functions from monotonic loading with strain rate changes and relaxation periods is described.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Mechanics of Materials (ISSN 0167-6636); 5; 35-48
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  • 89
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    Initial conditions for parabolic calculation of reacting flows (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 2; 235-240
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  • 90
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    Equilibrium shapes of acoustically levitated drops (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The quantitative determination of the shape of liquid drops levitated in an ultrasonic standing wave has provided experimental data on the radiation pressure-induced deformations of freely suspended liquids. Within the limits of small deviations from the spherical shape and small drop diameter relative to the acoustic wavelength, an existing approximate theory yields a good agreement with experimental evidence. The data were obtained for millimeter and submillimeter drops levitated in air under 1 g, where g is the sea level gravitational acceleration.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Acoustical Society of America, Journal (ISSN 0001-4966); 79; 1335-133
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  • 91
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    Evolution of a curved vortex filament into a vortex ring (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The deformation of a hairpin-shaped vortex filament under self-induction and in the presence of shear is studied numerically using the Biot-Savart law. It is shown that the tip region of an elongated hairpin vortex evolves into a vortex ring and that the presence of mean shear impedes the process. Evolution of a finite-thickness vortex sheet under self-induction is also investigated using the Navier-Stokes equations. The layer evolves into a hairpin vortex which in turn produces a vortex ring of high Reynolds stress content. These results indicate a mechanism for the generation of ring vortices in turbulent shear flows, and a link between the experimental and numerical observation of hairpin vortices and the observation of ring vortices in the outer regions of turbulent boundary layers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 29; 955-963
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  • 92
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    Influence of interface ply orientation on fatigue damage of adhesively bonded composite joints (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An experimental study of cracked-lap-shear specimens was conducted to determine the influence of adherend stacking sequence on debond initiation and damage growth in a composite-to-composite bonded joint. Specimens consisted of quasi-isotropic graphite/epoxy adherends bonded together with either FM-300 or EC 3445 adhesives. The stacking sequence of the adherends was varied such that 0 deg, 45 deg, or 90 deg plies were present at the adherend-adhesive interfaces. Fatigue damage initiated in the adhesive layer in those specimens with 0 deg and 45 deg interface plies. Damaage initiated in the form of ply cracking in the strap adherend for the specimens with 90 deg interface plies. The fatigue-damage growth was in the form of delamination within the composite adherends for specimens with the 90 deg and 45 deg plies next to the adhesive, while debonding in the adhesive resulted for the specimens with 0 deg plies next to the adhesive. Those joints with the 0 deg and 45 deg plies next to either adhesive has essentially the same fatigue-damage-initiation stress levels. These stress levels were 13 and 71 percent higher, respectively, than those for specimens with 90 deg plies next to the EC 3445 and FM-300 adhesives.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Composites Technology and Research (ISSN 0885-6804); 8; 3-7
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  • 93
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    Latitudinal extent of the heliospheric current sheet and modulation of galactic cosmic rays (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Possible correlations were investigated between the modulation of galactic cosmic rays and changes in the maximum heliographic latitude of the heliospheric current sheet during solar maximum. Solar photospheric magnetic field data from 1976-82 were extrapolated by means of potential theory to obtain the maximum latitudinal extent of the current sheet in the northern and southern hemispheres. The latitudinal differences were compared with terrestrial neutron flux data and Pioneer 10 data on cosmic rays with energies below 200 MeV at heliocentric distances of 10-30 AU. Account was taken for the time delay for the solar wind to propagate out to the spacecraft location. The current sheet maxima were nearly symmetrical about the solar equator except during sunspot maxima, when the solar poles were reversing. Significant changes in the latitudinal symmetry were highly correlated with the neutron data and cosmic fluctuations at Pioneer 10. The sensitivity of cosmic rays to the polarity reversals is in accordance with predictions of the gradient drift model.
    Schlagwort(e): SPACE RADIATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; 2933-294
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  • 94
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    Turbulent boundary-layer wall pressure fluctuations downstream of a tandem LEBU (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An initial measurement of turbulent wall pressure fluctuations downstream of tandem large eddy breakup devices (LEBUs) indicates a significant reduction by comparison with the reference case of a flat plate; the average magnitude of the reduction is 12.5 percent. Peak reduction is at 7-8 kHz, and is of the order of the C(f) reduction due to the tandem LEBUs. These data indicate a secondary benefit derivable from LEBUs, in addition to their skin friction reduction effect.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 689-691
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  • 95
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    Phase propagation of the solar modulation of galactic cosmic rays (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The phase of the 11-yr galactic cosmic ray variation, due to a varying rate of emission of long-lived, propagating regions of enhanced scattering, travels faster than the scattering regions themselves. The radial speed of the 11-yr phase in the quasi-steady force field approximation is exactly twice the speed of the individual episodic decreases. A time-dependent numerical solution for 1-GeV protons at 1 and 30 AU gives a phase speed which is 1.85 times the propagation speed of the individual decreases.
    Schlagwort(e): SPACE RADIATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; 2914-291
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  • 96
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    Stress waves in isotropic elastic plate excited by circular transducer (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Steady state harmonic stress waves in an isotropic elastic plate excited on one face by a circular transducer are analyzed theoretically. The transmitting transducer transforms an electrical voltage into a uniform normal stress at the top of the plate. To solve the boundary value problem,the radiation into a half-space is considered. The receiving transducer produces an electrical voltage proportional to the average spatially integrated normal stress over its face due to an incident wave. A numerical procedure is given to evaluate the frequency response at a receiving point due to a multiply reflected wave in the near field. Its stability and convergence are discussed. Parameterization plots which determine the particular wave whose frequency response has maximum magnitude compared with other multiple reflected waves are given for a range of values of dimensionless parameters. The effects of changes in the values of the parameters are discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Materials Evaluation (ISSN 0025-5327); 44; 455-462
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  • 97
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    Discrete mechanism damping effects in the solar array flight experiment (1986)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Accelerometer data were collected during on-orbit structural dynamic testing of the Solar Array Flight Experiment aboard the Space Shuttle, and were analyzed at Lockheed Missile and Space Co. to determine the amount of damping present in the structure. The results of this analysis indicated that the damping present in the fundamental in-plane mode of the structure substantially exceeded that of the fundamental out-of-plane mode. In an effort to determine the source of the higher in-plane damping, a test was performed involving a small device known as a constant-force spring motor or constant-torque mechanism. Results from this test indicate that this discrete device is at least partially responsible for the increased in-plane modal damping of the Solar Array Flight Experiment structure.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA. Lewis Research Center The 20th Aerospace Mechanics Symposium; p 277-289
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  • 98
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    On 3-D inelastic analysis methods for hot section components (1986)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The objective of this program is to produce a series of new computer codes that permit more accurate and efficient three-dimensional inelastic structural analysis of combustor liners, turbine blades, and turbine vanes. Each code embodies a progression of mathematical models for increasingly comprehensive representation of the geometrical features, loading conditions, and forms of nonlinear material response that distinguish these three groups of hot section components.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA, Lewis Research Center, Turbine Engine Hot Section Technology 1986; p 255-256
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  • 99
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    Fatigue and fracture overview (1986)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The accomplishments achieved under the isotropic creep-fatigue crack initiation life prediction program are summarized. A sizeable creep-fatigue crack initiation data base was generated on the nickel-base superalloy, B-1900. Companion constitutive modeling programs have also generated extensive data bases on the same heat of material. The crack initiation results have formed the basis of a new approach to creep-fatigue life prediction. The term Cyclic Damage Accumulation (CDA) was coined for the method, which was evaluated under isothermal, uniaxial conditions. Stringent laboratory verification experiments were used to test the accuracy of the method. Considering the quite limited material property data needed to evaluate the constants in the approach, the prediction accuracy is acceptable. At the expense of the larger data base required, Lewis developed total strain- strainrange partitioning method (TS-SRP) is capable of a higher degree of accuracy.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Turbine Engine Hot Section Technology 1986; p 33-43
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    HOST structural analysis program overview (1986)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Hot-section components of aircraft gas turbine engines are subjected to severe thermal structural loading conditions, especially during the startup and takeoff portions of the engine cycle. The most severe and damaging stresses and strains are those induced by the steep thermal gradients induced during the startup transient. These transient stresses and strains are also the most difficult to predict, in part because the temperature gradients and distributions are not well known or readily predictable and, in part, because the cyclic elastic-viscoplastic behavior of the materials at these extremes of temperature and strain are not well known or readily predictable. A broad spectrum of structures related technology programs is underway to address these deficiencies at the basic as well as the applied level. The three key program elements in the HOST structural analysis program are computations, constitutive modeling, and experiments for each research activity. Also shown are tables summarizing each of the activities.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Turbine Engine Hot Section Technology 1986; p 19-31
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