SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The symmetrical problem of two transverse cracks in an elastic strip with reinforced surfaces is formulated in terms of a singular integral equation. The special cases of one central crack or two edge cracks are discussed. Numerical methods for solving the problems with internal cracks are outlined and stress intensity factors are presented for various geometries and degrees of surface reinforcement.
Argon L1 fluorescence yields have been calculated for the individual multiplet states of ions containing from three to six M-shell vacancies. Effective fluorescence yields for these charge states are computed for statistically distributed states and for distributions that would arise in sequential stripping. For Ar L1M6, the latter result is about 430 times smaller than the former.
The author has identified the following significant results. Large areas covered by orbital photography allows the user to estimate the acreage of strip mining activity from a few frames. Infrared photography both in color and in black and white transparencies was found to be the best suited for this purpose.
This paper evaluates satellite imagery as a means of monitoring coal strip mines and their environmental effects. The satellite imagery employed is Skylab EREP S-190A and S-190B from SL-2, SL-3 and SL-4 missions; a large variety of camera/film/filter combinations has been reviewed. The investigation includes determining the applicability of satellite imagery for detection of disturbed acreage in areas of coal surface mining as well as the much more detailed monitoring of specific surface-mining operations, including: active mines, inactive mines, highwalls, ramp roads, pits, water impoundments and their associated acidity, graded areas and types of grading, and reclamed areas. Techniques have been developed to enable mining personnel to utilize this imagery in a practical and economic manner, requiring no previous photo-interpretation background and no purchases of expensive viewing or data-analysis equipment. To corroborate the photo-interpretation results, on-site observations were made in the very active mining area near Madisonville, Kentucky.
Molybdenum and niobium are often electroplated and subsequently stripped of copper. Since general standard plating techniques produce poor quality coatings, general procedures have been optimized and specified to give good results.
The fracture problem of laminated plates which consist of bonded orthotropic layers is studied. The fields equations for an elastic orthotropic body are transformed to give the displacement and stress expressions for each layer or strip. The unknown functions in these expressions are found by satisfying the remaining boundary and continuity conditions. A system of singular integral equations is obtained from the mixed boundary conditions. The singular behavior around the crack tip and at the bimaterial interface is studied. The stress intensity factors are computed for various material combinations and various crack geometries. The results are discussed and are compared with those for isotropic materials.
A flexible solar array strip is formed by providing printed circuitry between flexible layers of a nonconductive material, depositing solder pads on the printed circuitry, and storing the resulting substrate on a drum from which it is then withdrawn and advanced along a linear path. Solderless solar cells are serially transported into engagement with the pads and are infrared radiation to melt the solder and attach the cells to the circuitry. Excess flux is cleaned from the solar cells which are then encapsulated in a protective coating. The resulting array is then wound on a drum.
A machine is described for attaching solar cells to a flexable substrate on which printed circuitry has been deposited. The strip is fed through: (1) a station in which solar cells are elevated into engagement with solder pads for the printed circuitry and thereafter heated by an infrared lamp; (2) a station at which flux and solder residue is removed; (3) a station at which electrical performance of the soldered cells is determined; (4) a station at which an encapsulating resin is deposited on the cells; (5) a station at which the encapsulated solar cells are examined for electrical performance; and (6) a final station at which the resulting array is wound on a takeup drum.
Several three dimensional surface panel methods coupled on a streamwise strip basis to two dimensional boundary layer methods were compared to experimental data. Several different boundary layer simulations were investigated. Comparable boundary layer effects which converge to the expected two dimensional result wind increasing aspect ratio were indicated by either a transpiration or camber line displacement simulation. The method was applied to several varied configurations. The lift predictions agreed well with an approximate method based on correcting the inviscid lift using the two dimensional section viscous characteristics. The wing pressures and the effect of the boundary layer on the wing pressures were predicted accurately.
A flexible solar array strip is formed by a method which lends itself to automatic production techniques. Solder pads are deposited on printed circuitry deposited on a flexible structure. The resultant substrate is stored on a drum from which it is withdrawn and incrementally advanced along a linear path. Solderless solar cells are serially transported into engagement with the pads which are then heated in order to attach the cells to the circuitry. Excess flux is cleaned from the cells which are encapsulated in a protective coating. The resultant array is then spirally wound on a drum.
A 3D inviscid transonic analysis code was combined with a 2D strip integral boundary layer technique to form an approximate interaction procedure for analyzing the flow over a high aspect ratio wing near cruise conditions. Converged results obtained using the procedure for an aspect ratio 10.3 supercritical wing are discussed. Angle of attack adjustments were made during the iterative procedure in order to compensate for the viscous lift loss. A comparison of the calculations with experimental data is presented.
Friction measurement results obtained on the gypsum surface runways at Northrup Strip, White Sands Missile Range, N. M., using an instrumented tire test vehicle and a diagonal braked vehicle, are presented. These runways were prepared to serve as backup landing and retrieval sites to the primary sites located at Dryden Flight Research Center for shuttle orbiter during initial test flights. Similar friction data obtained on paved and other unpaved surfaces was shown for comparison and to indicate that the friction capability measured on the dry gypsum surface runways is sufficient for operations with the shuttle orbiter and the Boeing 747 aircraft. Based on these ground vehicle friction measurements, estimates of shuttle orbiter and aircraft tire friction performance are presented and discussed. General observations concerning the gypsum surface characteristics are also included and several recommendations are made for improving and maintaining adequate surface friction capabilities prior to the first shuttle orbiter landing.
The nonlinear behavior of a wave like deformed metal strip during the levelling process were calculated. Elastic-plastic material behavior as well as nonlinearities due to large deformations were considered. The considered problem lead to a combined stability and contact problem. It is shown that, despite the initially concentrated loading, neglecting the change of loading conditions due to altered contact domains may lead to a significant error in the evaluation of the nonlinear behavior and particularly to an underestimation of the stability limit load. The stability was examined by considering the load deflection path and the behavior of a load-dependent current stiffness parameter in combination with the determinant of the current stiffness matrix.
This paper addresses the steady, incompressible, two-dimensional flow past a flat plate with suction through porous strips. Closed-form solutions for each flow quantity are developed in the context of linearized triple-deck theory using Fourier transforms. To demonstrate the validity of these closed-form solutions, we compare the wall shear stress and pressure coefficients and the streamwise velocity profiles from the linearized theory with those obtained by the numerical integration of both interacting and nonsimilar boundary-layer equations. The agreement between the linearized triple-deck and interacting boundary-layer equations is good; however, the nonsimilar boundary layers, which fail to account for upstream influence, are shown to be in poor agreement with both interacting boundary layers and the linearized triple deck. The linearized closed-form solutions will therefore be very useful in future stability calculations.
Simple technique for designing strip-line or microstrip power dividers can be used for unequal, but inphase power split. Technique allows power splits ranging from equal to as large as required, with advantage of using same line impedances and line spacings for all splits. Output power ratio is determined by selecting location of input port in manner analogous to tap point for electric-power transformer.
The general plane problem for an infinite strip containing multiple cracks perpendicular to its boundaries is considered. The problem is reduced to a system of singular integral equations. Two specific problems of practical interest are then studied in detail. The first problem explores the interaction effect of multiple edge cracks in a plate or beam under tension or bending. The second problem is that of a rectangular plate containing an arbitrarily oriented crack in the plane of symmetry. Particular emphasis is placed on the problem of a plate containing an edge crack and subjected to concentrated forces.
Use of a supercritical airfoil can adversely affect wing flutter speeds in the transonic range. As adequate theories for three dimensional unsteady transonic flow are not yet available, the modified strip analysis was used to predict the transonic flutter boundary for the supercritical wing. The steady state spanwise distributions of section lift curve slope and aerodynamic center, required as input for the flutter calculations, were obtained from pressure distributions. The calculated flutter boundary is in agreement with experiment in the subsonic range. In the transonic range, a transonic bucket is calculated which closely resembles the experimental one with regard to both shape and depth, but it occurs at about 0.04 Mach number lower than the experimental one.
The experiments of Farmer, Hanson, and Wynne (1976) showed that use of a supercritical airfoil can adversely affect wing flutter speeds in the transonic range. Inasmuch as adequate theories for three-dimensional unsteady transonic flow are not yet available, the modified strip analysis published by Yates in 1958 has been used to predict the transonic flutter boundary for the supercritical wing tested by Farmer, Hanson, and Wynne. The steady-state spanwise distributions of section lift-curve slope and aerodynamic center, required as input for the flutter calculations, were obtained from pressure distributions measured by Harris (1972). The calculated flutter boundary is in excellent agreement with experiment in the subsonic range. In the transonic range a 'transonic bucket' is calculated which closely resembles the experimental one with regard to both shape and depth, but it occurs at about 0.04 Mach number lower than the experimental one.