A shock wave study of Coconino sandstone
Hugoniot equation of state measurements from shock wave loading study of Coconino sandstone
Gregson, V. G.↗
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Nonlinear analysis of rotor-bearing systems using component mode synthesis
The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems, has been written and results are presented for transient system response associated with blade loss dynamics with squeeze film dampers, and with interference rubs.
Nelson, H. D.↗
X-ray diffraction from high pressure Ge using synchrotron radiation
The high pressure structural phase transition in Ge has been studied using the energy dispersive X-ray diffraction technique and a synchrotron radiation source. Ge was observed to transform to the beta-Sn tetragonal structure in agreement with the earlier results of Jamieson, but the phase transition began at 80 + or - 5 kilobars, a somewhat lower value than generally reported. These experimental diffraction results are compared with the recent self-consistent pseudopotential calculations of Yin and Cohen (1981) and with the observed transition pressure for shock wave loaded Ge.
Baublitz, M., Jr.↗
Spacecraft observations of the interaction of active comets with the solar wind
Six spacecraft encountered two comets during 1985 and 1986, obtaining a wealth of data relative to the plasma processes at work in the interaction of an active comet with the solar wind. A review of what space plasma scientists have learned from these data and of their interpretations is presented. The interaction process begins millions of kilometers from the nucleus where the solar wind first picks up cometary ions that slow down the wind and causes the interplanetary magnetic field to pile up and drape around the comet's ionosphere. Thus the geometry of a comet's plasma tail is defined by this draped field. At Halley the Giotto spacecraft noted a well-defined boundary separating the mixture of solar wind and cometary plasmas and the interplanetary magnetic field from the free-field, almost pure cometary plasma in the inner coma. Additional unexpected features in the inner coma were a flux of fast 'granddaughter' ions and high densities of negative ions. Further details covering pickup ions and plasma waves, mass loading, bow shock, energetic particles, the cometosheath, the ionopause, the plasma tail, and the field-free region are provided.
Neugebauer, M.↗
Calculation of unsteady linearized Euler flows in cascades using harmonically deforming grids
A method for calculating unsteady, inviscid, compressible flows in cascades is presented. Using the linearized Euler technique, the flow is decomposed into a steady or mean flow plus a harmonically varying small disturbance flow. The equations that describe the small disturbance flow are linear variable coefficient equations, and are solved using a pseudo-time time marching Lax-Wendroff technique. Unlike previous linearized methods, however, the solution is computed on a harmonically deforming computational grid that conforms to the motion of the vibrating airfoils. The mean flow and perturbation flow solutions are defined in the deforming coordinate system rather than in a coordinate system fixed in space. Hence, no extrapolation terms are required to implement the upwash boundary conditions at the airfoil surfaces, significantly improving the accuracy of the method. For transonic flow calculations, unsteady shock motions are modelled using shock capturing. The unsteady loads due to the shock motion are then seen as pressure impulses. Representative computational results are presented for transonic channel flows and subsonic and transonic cascade flows.
Hall, Kenneth C.↗
A Comparative Study of Three Methodologies for Modeling Dynamic Stall
During the past two decades, there has been an increased reliance on the use of computational fluid dynamics methods for modeling rotors in high speed forward flight. Computational methods are being developed for modeling the shock induced loads on the advancing side, first-principles based modeling of the trailing wake evolution, and for retreating blade stall. The retreating blade dynamic stall problem has received particular attention, because the large variations in lift and pitching moments encountered in dynamic stall can lead to blade vibrations and pitch link fatigue. Restricting to aerodynamics, the numerical prediction of dynamic stall is still a complex and challenging CFD problem, that, even in two dimensions at low speed, gathers the major difficulties of aerodynamics, such as the grid resolution requirements for the viscous phenomena at leading-edge bubbles or in mixing-layers, the bias of the numerical viscosity, and the major difficulties of the physical modeling, such as the turbulence models, the transition models, whose both determinant influences, already present in static maximal-lift or stall computations, are emphasized by the dynamic aspect of the phenomena.
Sankar, L.↗
Rocket Engine Nozzle Side Load Transient Analysis Methodology: A Practical Approach
At the sea level, a phenomenon common with all rocket engines, especially for a highly over-expanded nozzle, during ignition and shutdown is that of flow separation as the plume fills and empties the nozzle, Since the flow will be separated randomly. it will generate side loads, i.e. non-axial forces. Since rocket engines are designed to produce axial thrust to power the vehicles, it is not desirable to be excited by non-axial input forcing functions, In the past, several engine failures were attributed to side loads. During the development stage, in order to design/size the rocket engine components and to reduce the risks, the local dynamic environments as well as dynamic interface loads have to be defined. The methodology developed here is the way to determine the peak loads and shock environments for new engine components. In the past it is not feasible to predict the shock environments, e.g. shock response spectra, from one engine to the other, because it is not scaleable. Therefore, the problem has been resolved and the shock environments can be defined in the early stage of new engine development. Additional information is included in the original extended abstract.
Shi, John J.↗
Summary of Data from the Sixth AIAA CFD Drag Prediction Workshop: CRM Cases 2 to 5
Results from the Sixth AIAA CFD Drag Prediction Workshop Common Research Model Cases 2 to 5 are presented. As with past workshops, numerical calculations are performed using industry-relevant geometry, methodology, and test cases. Cases 2 to 5 focused on force/moment and pressure predictions for the NASA Common Research Model wing-body and wing-body-nacelle-pylon configurations, including Case 2 - a grid refinement study and nacelle-pylon drag increment prediction study; Case 3 - an angle-of-attack buffet study; Case 4 - an optional wing-body grid adaption study; and Case 5 - an optional wing-body coupled aero-structural simulation. The Common Research Model geometry differed from previous workshops in that it was deformed to the appropriate static aeroelastic twist and deflection at each specified angle-of-attack. The grid refinement study used a common set of overset and unstructured grids, as well as user created Multiblock structured, unstructured, and Cartesian based grids. For the supplied common grids, six levels of refinement were created resulting in grids ranging from 7x10(exp 6) to 208x10(exp 6) cells. This study (Case 2) showed further reduced scatter from previous workshops, and very good prediction of the nacelle-pylon drag increment. Case 3 studied buffet onset at M=0.85 using the Medium grid (20 to 40x10(exp 6) nodes) from the above described sequence. The prescribed alpha sweep used finely spaced intervals through the zone where wing separation was expected to begin. Although the use of the prescribed aeroelastic twist and deflection at each angle-of-attack greatly improved the wing pressure distribution agreement with test data, many solutions still exhibited premature flow separation. The remaining solutions exhibited a significant spread of lift and pitching moment at each angle-of-attack, much of which can be attributed to excessive aft pressure loading and shock location variation. Four Case 4 grid adaption solutions were submitted. Starting with grids less than 2x10(exp 6) grid points, two solutions showed a rapid convergence to an acceptable solution. Four Case 5 coupled aerostructural solutions were submitted. Both showed good agreement with experimental data. Results from this workshop highlight the continuing need for CFD improvement, particularly for conditions with significant flow separation. These comparisons also suggest the need for improved experimental diagnostics to guide future CFD development.
Tinoco, Edward N.↗
Environmental test program for the Mars Exploration Rover Project
This paper will present an overview of the test campaign that included vibration, pyro-shock, landing loads, acoustic noise, thermal vacuum and solar simulation testing at the Jet Propulsion Laboratory Environmental Test Laboratory facilities in Pasadena, California.
Van Velzer, Paul L.↗
DESIGN CRITERIA FOR ZERO-LEAKAGE CONNECTORS FOR LAUNCH VEHICLES, VOLUME 6 - ENVIRONMENTAL EFFECTS
Pressure pulses, shock and vibratory loading on launch vehicle connectors - heat environment, vacuum and radiation effects on connector gaskets
LAUNCH VEHICLE↗
Preliminary Investigation of the Heat Shock Resistant Properties of Molybdenum Disilicide Blades Under Centrifugal Load
An investigation to determine the heat-shock resistant properties of two molybdenum disilicide turbine blades under centrifugal loads imposed by turbine rotation is presented. Molybdenum disilicide turbine blades fabricated by hot-pressing techniques withstood heat-shock conditions under blade centrifugal stresses up to 5350 pounds per square inch. Additional development is required before the heat-shock resistant properties of molybdenum disilicide are satisfactory for turbine-blade application.
MATERIALS, PROPERTIES-THERMAL↗
Aerospace systems pyrotechnic shock data /ground test and flight/. Volume 7 - Investigation of mass loading effects Final report, 12 May - 12 Nov. 1970
Mass loading effects on pyrotechnic shock environment of aerospace systems
Engelsgjerd, I. K.↗
Low-Heat-Transfer Tank Mount
Supporting element adapts to high or low side loads. Passive Orbital Disconnect Strut (PODS) for cryogenic tank engages an extra-strong member only during peak side or axial loads like those from vibrations, accelerations, and shocks. When side loads are low, support provided by lower-strength, lower-thermal-conductance, passive disconnect.
Parmley, R. T.↗
A shock spectra and impedance method to determine a bound for spacecraft structural loads
This paper proposes a method for the determination of design loads of a spacecraft mounted on a launch vehicle when the significant frequency ranges of the two structures overlap. The derived loads are realistic upper bounds of the flight loads. The method utilizes shock spectra of the spacecraft/launch vehicle interface directional accelerations for each event separately and introduces a reduction factor for the shock spectra which is based on the relative impedance of the spacecraft and launch vehicle. The main advantages of the method are low cost of analysis and timeliness in the design. These advantages are attained with only a slight expense of structural weight compared to the more exact transient analysis method.
Bamford, R.↗
Experimental studies on the tripping behavior of narrow T-stiffened flat plates subjected to hydrostatic pressure and underwater shock
An experimental investigation was conducted to determine the static and dynamic responses of a specific stiffened flat plate design. The air-backed rectangular flat plates of 6061-T6 aluminum with an externally machined longitudinal narrow-flanged T-stiffener and clamped boundary conditions were subjected to static loading by water hydropump pressure and shock loading from an eight pound TNT charge detonated underwater. The dynamic test plate was instrumented to measure transient strains and free field pressure. The static test plate was instrumented to measure transient strains, plate deflection, and pressure. Emphasis was placed upon forcing static and dynamic stiffener tripping, obtaining relevant strain and pressure data, and studying the associated plate-stiffener behavior.
Budweg, H. L.↗
Improving the Mach number capabilities of arc driven shock tubes
New systematic trends in one of the performance parameters of pressure loaded arc driven shock tubes have been determined. For a given configuration, the Mach number increases with the cube root of capacitor energy; however, the initial driver gas pressure is relatively unimportant. A qualitative model based on the assumption of Joule-preheating by the arc discharge is discussed.
Johnson, J. A., III↗
Theoretical determination of water loads on pitching hulls and shock-mounted hydro-skis
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Schnitzer, Emanuel↗
Blast Loading of Epoxy Panels Using a Shock Tube
The high strain rate mechanical response of thin polymer plates has been studied using a modified shock tube. Diagnostics include the pressure-time history of the incident and reflected pulses and the use of digital image correlation (DIC) techniques to extract the time-history of the out-of-plane displacement distribution. Additionally, finite element models have been developed to understand the plate response and to validate and modify plate material constitutive models that have been proposed.
Pankow, Mark↗