Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Static analysis”

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.

At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Climate Analytics as a Service

Exascale computing, big data, and cloud computing are driving the evolution of large-scale information systems toward a model of data-proximal analysis. In response, we are developing a concept of climate analytics as a service (CAaaS) that represents a convergence of data analytics and archive management. With this approach, high-performance compute-storage implemented as an analytic system is part of a dynamic archive comprising both static and computationally realized objects. It is a system whose capabilities are framed as behaviors over a static data collection, but where queries cause results to be created, not found and retrieved. Those results can be the product of a complex analysis, but, importantly, they also can be tailored responses to the simplest of requests. NASA's MERRA Analytic Service and associated Climate Data Services API provide a real-world example of climate analytics delivered as a service in this way. Our experiences reveal several advantages to this approach, not the least of which is orders-of-magnitude time reduction in the data assembly task common to many scientific workflows.

big data↗
NASA NTRS1994

JPL-ANTOPT antenna structure optimization program

New antenna path-length error and pointing-error structure optimization codes were recently added to the MSC/NASTRAN structural analysis computer program. Path-length and pointing errors are important measured of structure-related antenna performance. The path-length and pointing errors are treated as scalar displacements for statics loading cases. These scalar displacements can be subject to constraint during the optimization process. Path-length and pointing-error calculations supplement the other optimization and sensitivity capabilities of NASTRAN. The analysis and design functions were implemented as 'DMAP ALTERs' to the Design Optimization (SOL 200) Solution Sequence of MSC-NASTRAN, Version 67.5.

Strain, D. M.↗
NASA NTRS1976

NASTRAN: User's Experiences

The application of NASTRAN to a wide variety of static and dynamic structural problems is discussed. The following topics are focused upon: (1) methods of analysis; (2) hydroelastic methods; (3) complete analysis of structures; (4) elements and material studies; (5) critical comparisons with other programs; and (6) pre- and post-processor operations.

Source record↗
NASA NTRS1979

PARS: Programs for Analysis and Resizing of Structures, user manual

PARS processors and their use, flutter analysis, sensitivity analysis for stresses, and resizing are presented. Design variable definition and interface with finite element model, static constraints and their derivatives, flutter derivatives, and optimization are discussed.

Haftka, R. T.↗
NASA NTRS1985

Preliminary report on tests of tensile specimens with a part-through surface notch for a filament wound graphite/epoxy material

The behavior of tensile coupons with surface notches of various semi-elliptical shapes were evaluated for specimens obtained from a filament wound graphite/epoxy cylinder. The quasi-static test results, in some instances, are inadequate for defining complete trend curves and the interpretive analysis is considered to be preliminary. Specimens with very shallow notches were observed to be notch insensitive and the unnotched strength from these specimens was determined to be 54.97 Ksi. The failure strain of the laminate was found to be 1.328%. Specimens with deeper notches were sensitive to notch depth, notch aspect ratio, and specimen width. Using the unnotched strength of 54.97 Ksi and Poe's general toughness parameter, the fracture toughness was estimated to be 27.2 Ksi square root of In. Isotropic linear elastic fracture mechanics together with the estimated fracture toughness correctly predicted the influence of notch depth, aspect ratio, and specimen finitewidth.

Harris, C. E.↗
NASA NTRS1984

Design, Fabrication and Test of Composite Curved Frames for Helicopter Fuselage Structure

Aspects of curved beam effects and their importance in designing composite frame structures are discussed. The curved beam effect induces radial flange loadings which in turn causes flange curling. This curling increases the axial flange stresses and induces transverse bending. These effects are more important in composite structures due to their general inability to redistribute stresses by general yielding, such as in metal structures. A detailed finite element analysis was conducted and used in the design of composite curved frame specimens. Five specimens were statically tested and compared with predicted and test strains. The curved frame effects must be accurately accounted for to avoid premature fracture; finite element methods can accurately predict most of the stresses and no elastic relief from curved beam effects occurred in the composite frames tested. Finite element studies are presented for comparative curved beam effects on composite and metal frames.

Lowry, D. W.↗
NASA NTRS1985

Experimental measurements of hydrodynamic radial forces and stiffness matrices for a centrifugal pump-impeller

Measurements of the steady-state hydrodynamic forces on a centrifugal pump impeller are presented as a function of position within two geometrically different volutes. These correspond to the forces experienced by the impeller at zero whirl frequency. The hydrodynamic force matrices derived from these measurements exhibit both diagonal and off-diagonal terms of substantial magnitude. These terms are of the form which would tend to excite a whirl motion in a rotordynamic analysis of the pump; this may be the cause of 'rough running' reported in many pumps. Static pressure measurements in the impeller discharge flow show that the hydrodynamic force on the impeller contains a substantial component due to the nonisotropy of the net momentum flux leaving the impeller. A similar breakdown of the contributions to the stiffness matrices reveals that the major component of these matrices results from the nonisotropy of the momentum flux.

Chamieh, D. S.↗
NASA NTRS1985

A note on finite-dimensional estimators for infinite-dimensional systems

In this note two theorems are proved regarding finite-dimensional estimators for infinite-dimensional systems. The first concerns the finite dimensionality of the model and the second concerns the finite dimensionality of the observation space. The analysis applies to very general systems, but appears to be most useful for the estimation of static systems from point sensing.

Milman, M. H.↗
NASA NTRS1986

Static shape control for flexible structures

An integrated methodology is described for defining static shape control laws for large flexible structures. The techniques include modeling, identifying and estimating the control laws of distributed systems characterized in terms of infinite dimensional state and parameter spaces. The models are expressed as interconnected elliptic partial differential equations governing a range of static loads, with the capability of analyzing electromagnetic fields around antenna systems. A second-order analysis is carried out for statistical errors, and model parameters are determined by maximizing an appropriate defined likelihood functional which adjusts the model to observational data. The parameter estimates are derived from the conditional mean of the observational data, resulting in a least squares superposition of shape functions obtained from the structural model.

Rodriguez, G.↗
NASA NTRS1992

Classical and adaptive control algorithms for the solar array pointing system of the Space Station Freedom

Classical and adaptive control algorithms for the solar array pointing system of the Space Station Freedom are designed using a continuous rigid body model of the solar array gimbal assembly containing both linear and nonlinear dynamics due to various friction components. The robustness of the design solution is examined by performing a series of sensitivity analysis studies. Adaptive control strategies are examined in order to compensate for the unfavorable effect of static nonlinearities, such as dead-zone uncertainties.

Ianculescu, G. D.↗
NASA NTRS1946

Comparison of Several Methods of Predicting the Pressure Loss at Altitude Across a Baffled Aircraft-Engine Cylinder

Several methods of predicting the compressible-flow pressure loss across a baffled aircraft-engine cylinder were analytically related and were experimentally investigated on a typical air-cooled aircraft-engine cylinder. Tests with and without heat transfer covered a wide range of cooling-air flows and simulated altitudes from sea level to 40,000 feet. Both the analysis and the test results showed that the method based on the density determined by the static pressure and the stagnation temperature at the baffle exit gave results comparable with those obtained from methods derived by one-dimensional-flow theory. The method based on a characteristic Mach number, although related analytically to one-dimensional-flow theory, was found impractical in the present tests because of the difficulty encountered in defining the proper characteristic state of the cooling air. Accurate predictions of altitude pressure loss can apparently be made by these methods, provided that they are based on the results of sea-level tests with heat transfer.

Neustein, Joseph↗
NASA NTRS1959

Low-Speed Measurements of Static and Oscillatory Lateral Stability Derivatives of a 1/5 Scale Model of a Jet-Powered Vertical-Attitude VTOL Research Airplane

Force tests of the static and dynamic lateral stability characteristics of a VTOL airplane having a triangular wing mounted high on the fuselage with a triangular vertical tail on top of the wing and no horizontal tail have been made in the Langley free-flight tunnel. The static lateral stability parameters and the rolling, yawing, and sideslipping dynamic stability derivatives are presented without analysis.

Shanks, Robert E.↗
NASA NTRS1960

Applications of a General Finite-Difference Method for Calculating Bending Deformations of Solid Plates

This paper reports the findings of an investigation of a finite - difference method directly applicable to calculating static or simple harmonic flexures of solid plates and potentially useful in other problems of structural analysis. The method, which was proposed in doctoral thesis by John C. Houbolt, is based on linear theory and incorporates the principle of minimum potential energy. Full realization of its advantages requires use of high-speed computing equipment. After a review of Houbolt's method, results of some applications are presented and discussed. The applications consisted of calculations of the natural modes and frequencies of several uniform-thickness cantilever plates and, as a special case of interest, calculations of the modes and frequencies of the uniform free-free beam. Computed frequencies and nodal patterns for the first five or six modes of each plate are compared with existing experiments, and those for one plate are compared with another approximate theory. Beam computations are compared with exact theory. On the basis of the comparisons it is concluded that the method is accurate and general in predicting plate flexures, and additional applications are suggested. An appendix is devoted t o computing procedures which evolved in the progress of the applications and which facilitate use of the method in conjunction with high-speed computing equipment.

Walton, William C., Jr.↗
NASA NTRS2000

Limb congestion enhances the synchronization of sympathetic outflow with muscle contraction

In this report, we examined if the synchronization of muscle sympathetic nerve activity (MSNA) with muscle contraction is enhanced by limb congestion. To explore this relationship, we applied signal-averaging techniques to the MSNA signal obtained during short bouts of forearm contraction (2-s contraction/3-s rest cycle) at 40% maximal voluntary contraction for 5 min. We performed this analysis before and after forearm venous congestion; an intervention that augments the autonomic response to sustained static muscle contractions via a local effect on muscle afferents. There was an increased percentage of the MSNA noted during second 2 of the 5-s contraction/rest cycles. The percentage of total MSNA seen during this particular second increased from minute 1 to 5 of contraction and was increased further by limb congestion (control minute 1 = 25.6 +/- 2.0%, minute 5 = 32.8 +/- 2.2%; limb congestion minute 1 = 29.3 +/- 2.1%, minute 5 = 37.8 +/- 3.9%; exercise main effect <0.005; limb congestion main effect P = 0.054). These changes in the distribution of signal-averaged MSNA were seen despite the fact that the mean number of sympathetic discharges did not increase over baseline. We conclude that synchronization of contraction and MSNA is seen during short repetitive bouts of handgrip. The sensitizing effect of contraction time and limb congestion are apparently due to feedback from muscle afferents within the exercising muscle.

Non-NASA Center↗
NASA NTRS2008

Uncertainty and Sensitivity Analyses of Duct Propagation Models

This paper presents results of uncertainty and sensitivity analyses conducted to assess the relative merits of three duct propagation codes. Results from this study are intended to support identification of a "working envelope" within which to use the various approaches underlying these propagation codes. This investigation considers a segmented liner configuration that models the NASA Langley Grazing Incidence Tube, for which a large set of measured data was available. For the uncertainty analysis, the selected input parameters (source sound pressure level, average Mach number, liner impedance, exit impedance, static pressure and static temperature) are randomly varied over a range of values. Uncertainty limits (95% confidence levels) are computed for the predicted values from each code, and are compared with the corresponding 95% confidence intervals in the measured data. Generally, the mean values of the predicted attenuation are observed to track the mean values of the measured attenuation quite well and predicted confidence intervals tend to be larger in the presence of mean flow. A two-level, six factor sensitivity study is also conducted in which the six inputs are varied one at a time to assess their effect on the predicted attenuation. As expected, the results demonstrate the liner resistance and reactance to be the most important input parameters. They also indicate the exit impedance is a significant contributor to uncertainty in the predicted attenuation.

Nark, Douglas M.↗
NASA NTRS2013

Stability of Menisci in Detached Bridgman Growth

Detached growth, also referred to as dewetted growth, is a Bridgman crystal growth process in which the melt is in contact with the crucible wall but the crystal is not. A meniscus bridges the gap between the top of the crystal and the crucible wall. The meniscus shape depends on the contact angle of the melt with the crucible wall, the growth angle of the melt with respect to the solidifying crystal, the gas pressure differential, the Weber number describing the rotation rate of the crucible, and the Bond number. Only some of the meniscus shapes are stable and the stability criterion is the sign of the second variation of the potential energy upon admissible meniscus shape perturbations. The effects of confined gas volumes above and below the melt and crucible rotation are evaluated. The analysis is applicable to the non-stationary case where the crystal radius changes during growth. Static stability maps (crystal radius versus pressure differential) are obtained for a series of Bond numbers, growth angles and Weber numbers. Also, the specific cases of Ge and InSb, in both terrestrial and microgravity conditions, are analyzed. Stability was found to depend significantly on whether the interior surface was considered to be microscopically rough or smooth, corresponding to pinned or unpinned states. It was also found that all meniscus shapes are statically stable in a microgravity environment.

Mazuruk, K.↗
NASA NTRS2013

Stability of Menisci in Detached Bridgman Growth

Detached growth, also referred to as dewetted growth, is a Bridgman crystal growth process in which the melt is in contact with the crucible wall but the crystal is not. A meniscus bridges the gap between the top of the crystal and the crucible wall. The meniscus shape depends on the contact angle of the melt with the crucible wall, the growth angle of the melt with respect to the solidifying crystal, the gas pressure differential, the Weber number describing the rotation rate of the crucible, and the Bond number. Only some of the meniscus shapes are stable and the stability criterion is the sign of the second variation of the potential energy upon admissible meniscus shape perturbations. The effects of confined gas volumes above and below the melt and crucible rotation are evaluated. The analysis is applicable to the non-stationary case where the crystal radius changes during growth. Static stability maps (crystal radius versus pressure differential) are obtained for a series of Bond numbers, growth angles and Weber numbers. Also, the specific cases of Ge and InSb, in both terrestrial and microgravity conditions, are analyzed. Stability was found to depend significantly on whether the interior surface was considered to be microscopically rough or smooth, corresponding to pinned or unpinned states. It was also found that all meniscus shapes are statically stable in a microgravity environment.

Mazuruk, Konstantin↗
NASA NTRS1978

Analysis and Test of Deep Flaws in Thin Sheets of Aluminum and Titanium. Volume 2: Crack Opening Displacement and Stress-Strain Data

Static fracture tests were performed on surface flawed specimens of aluminum and titanium alloys. A simulated proof overload cycle was applied prior to all of the cyclic tests. Variables included in each test series were flaw shapes and thickness. Additionally, test temperature was a variable for the aluminum test series. The crack opening displacement and stress-strain data obtained are presented.

Finger, R. W.↗