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At least 379 records · Page 21

All sources NASA NTRS DOE OSTI

NASA NTRS1971

The NASTRAN computer program for structural analysis.

Discussion of a large NASA-sponsored digital computer program for static and dynamic analysis of structures with linear or nonlinear material properties. The program fits to perform buckling analysis, vibration mode analysis of conservative or damped systems, frequency response analysis, and transient response analysis on the IBM 360, UNIVAC 1108, and CDC 6600 computers. It also provides automatic generation of several types of loads such as gravity loads and thermal strain loads, plots of deformed and nondeformed structures, and the choice of alternate analysis methods such as direct or modal formulations of dynamic problems. The program is intended primarily for large problems involving hundreds of thousands of degrees of freedom. A flexible Executive System is provided to facilitate the addition of new functional capabilities to the program.

Macneal, R. H.↗

NASA NTRS2012

Hypersonic and Supersonic Static Aerodynamics of Mars Science Laboratory Entry Vehicle

This paper describes the analysis of continuum static aerodynamics of Mars Science Laboratory (MSL) entry vehicle (EV). The method is derived from earlier work for Mars Exploration Rover (MER) and Mars Path Finder (MPF) and the appropriate additions are made in the areas where physics are different from what the prior entry systems would encounter. These additions include the considerations for the high angle of attack of MSL EV, ablation of the heatshield during entry, turbulent boundary layer, and other aspects relevant to the flight performance of MSL. Details of the work, the supporting data and conclusions of the investigation are presented.

Dyakonov, Artem A.↗

NASA NTRS1992

SAPNEW: Parallel finite element code for thin shell structures on the Alliant FX/80

The results of a research activity aimed at providing a finite element capability for analyzing turbo-machinery bladed-disk assemblies in a vector/parallel processing environment are summarized. Analysis of aircraft turbofan engines is very computationally intensive. The performance limit of modern day computers with a single processing unit was estimated at 3 billions of floating point operations per second (3 gigaflops). In view of this limit of a sequential unit, performance rates higher than 3 gigaflops can be achieved only through vectorization and/or parallelization as on Alliant FX/80. Accordingly, the efforts of this critically needed research were geared towards developing and evaluating parallel finite element methods for static and vibration analysis. A special purpose code, named with the acronym SAPNEW, performs static and eigen analysis of multi-degree-of-freedom blade models built-up from flat thin shell elements.

Kamat, Manohar P.↗

NASA NTRS1969

Application of the NASA general purpose structural analysis program to large radio telescopes.

NASA structural analysis /NASTRAN/ program applied to large radio telescopes, discussing static and dynamic analysis, problem formulation, finite element method, etc

Mccormick, C. W.↗

NASA NTRS1992

SAPNEW: Parallel finite element code for thin shell structures on the Alliant FX-80

The finite element method has proven to be an invaluable tool for analysis and design of complex, high performance systems, such as bladed-disk assemblies in aircraft turbofan engines. However, as the problem size increase, the computation time required by conventional computers can be prohibitively high. Parallel processing computers provide the means to overcome these computation time limits. This report summarizes the results of a research activity aimed at providing a finite element capability for analyzing turbomachinery bladed-disk assemblies in a vector/parallel processing environment. A special purpose code, named with the acronym SAPNEW, has been developed to perform static and eigen analysis of multi-degree-of-freedom blade models built-up from flat thin shell elements. SAPNEW provides a stand alone capability for static and eigen analysis on the Alliant FX/80, a parallel processing computer. A preprocessor, named with the acronym NTOS, has been developed to accept NASTRAN input decks and convert them to the SAPNEW format to make SAPNEW more readily used by researchers at NASA Lewis Research Center.

Kamat, Manohar P.↗

NASA NTRS1996

Dynamic Analysis of Spur Gear Transmissions (DANST). PC Version 3.00 User Manual

DANST is a FORTRAN computer program for static and dynamic analysis of spur gear systems. The program can be used for parametric studies to predict the static transmission error, dynamic load, tooth bending stress and other properties of spur gears as they are influenced by operating speed, torque, stiffness, damping, inertia, and tooth profile. DANST performs geometric modeling and dynamic analysis for low- or high-contact-ratio spur gears. DANST can simulate gear systems with contact ratios ranging from one to three. It was designed to be easy to use and it is extensively documented in several previous reports and by comments in the source code. This report describes installing and using a new PC version of DANST, covers input data requirements and presents examples.

Oswald, Fred B.↗

NASA NTRS1993

Dynamic analysis of spur gears using computer program DANST

DANST is a computer program for static and dynamic analysis of spur gear systems. The program can be used for parametric studies to predict the effect on dynamic load and tooth bending stress of spur gears due to operating speed, torque, stiffness, damping, inertia, and tooth profile. DANST performs geometric modeling and dynamic analysis for low- or high-contact-ratio spur gears. DANST can simulate gear systems with contact ratio ranging from one to three. It was designed to be easy to use, and it is extensively documented by comments in the source code. This report describes the installation and use of DANST. It covers input data requirements and presents examples. The report also compares DANST predictions for gear tooth loads and bending stress to experimental and finite element results.

Oswald, Fred B.↗

NASA NTRS1993

Dynamic analysis of spur gears using computer program DANST

Oswald, Fred B.↗

NASA NTRS1993

Single Event Upset Behavior of CMOS Static RAM Cells

An improved state-space analysis of the CMOS static RAM cell is presented. Introducing theconcept of the dividing line, the critical charge for heavy-ion-induced upset of memory cells can becalculated considering symmetrical as well as asymmetrical capacitive loads. From the criticalcharge, the upset-rate per bit-day for static RAMs can be estimated.

Lieneweg, Udo↗

NASA NTRS2010

Architectural Analysis of Systems Based on the Publisher-Subscriber Style

Architectural styles impose constraints on both the topology and the interaction behavior of involved parties. In this paper, we propose an approach for analyzing implemented systems based on the publisher-subscriber architectural style. From the style definition, we derive a set of reusable questions and show that some of them can be answered statically whereas others are best answered using dynamic analysis. The paper explains how the results of static analysis can be used to orchestrate dynamic analysis. The proposed method was successfully applied on the NASA's Goddard Mission Services Evolution Center (GMSEC) software product line. The results show that the GMSEC has a) a novel reusable vendor-independent middleware abstraction layer that allows the NASA's missions to configure the middleware of interest without changing the publishers' or subscribers' source code, and b) some high priority bugs due to behavioral discrepancies, which were eluded during testing and code reviews, among different implementations of the same APIs for different vendors.

Ganesun, Dharmalingam↗

NASA NTRS2004

Automated Static Culture System Cell Module Mixing Protocol and Computational Fluid Dynamics Analysis

This report is a documentation of a fluid dynamic analysis of the proposed Automated Static Culture System (ASCS) cell module mixing protocol. The report consists of a review of some basic fluid dynamics principles appropriate for the mixing of a patch of high oxygen content media into the surrounding media which is initially depleted of oxygen, followed by a computational fluid dynamics (CFD) study of this process for the proposed protocol over a range of the governing parameters. The time histories of oxygen concentration distributions and mechanical shear levels generated are used to characterize the mixing process for different parameter values.

Kleis, Stanley J.↗

NASA NTRS1973

Aeroelastic effects on space shuttle dynamics

A simplified analysis procedure for determining static and dynamic aeroelastic loads for the space shuttle and space shuttle configuration is presented. A computer program, originally developed for the Atlas launch vehicle, was modified for simplifying the turbulence response analysis approach. This approach is compared with a more detailed and time consuming approach to space shuttle response to turbulence which was developed earlier. The simplification in going from interference to lumped aerodynamic data was found to give adequate results for preliminary design aeroelastic analysis. Gust loads were found to be approximately 50% of the maximum static aeroelastic loads. The autopilot became unstable when ten elastic modes were included. Elastic effects were found to be less than 3% in the static aeroelastic analysis.

Source record↗

NASA NTRS1982

Structures and Dynamics Division research and technology plans, FY 1982

Computational devices to improve efficiency for structural calculations are assessed. The potential of large arrays of microprocessors operating in parallel for finite element analysis is defined, and the impact of specialized computer hardware on static, dynamic, thermal analysis in the optimization of structural analysis and design calculations is determined. General aviation aircraft crashworthiness and occupant survivability is also considered. Mechanics technology required for design coefficient, fault tolerant advanced composite aircraft components subject to combined loads, impact, postbuckling effects and local discontinuities are developed.

Bales, K. S.↗

NASA NTRS1985

Use of statical indentation laws in the impact analysis of laminated composite plates

The low-velocity impact response of graphite/epoxy laminates was investigated theoretically and experimentally. A nine-node isoparametric plate finite element in conjunction with an empirical contact law was used for the theoretical investigation. Theoretical results are in good agreement with strain-gage experimental data. The results of the investigation indicate that the present theoretical procedure describes the impact response of laminate for low-impact velocities.

Tan, T. M.↗

NASA NTRS1987

Efficient Ada multitasking on a RISC register window architecture

This work addresses the problem of reducing context switch overhead on a processor which supports a large register file - a register file much like that which is part of the Berkeley RISC processors and several other emerging architectures (which are not necessarily reduced instruction set machines in the purest sense). Such a reduction in overhead is particularly desirable in a real-time embedded application, in which task-to-task context switch overhead may result in failure to meet crucial deadlines. A storage management technique by which a context switch may be implemented as cheaply as a procedure call is presented. The essence of this technique is the avoidance of the save/restore of registers on the context switch. This is achieved through analysis of the static source text of an Ada tasking program. Information gained during that analysis directs the optimized storage management strategy for that program at run time. A formal verification of the technique in terms of an operational control model and an evaluation of the technique's performance via simulations driven by synthetic Ada program traces are presented.

Kearns, J. P.↗

NASA NTRS1995

Navier-Stokes analysis of a delta wing in static and dynamic roll

The three-dimensional, Reynolds-averaged, Navier-Stokes equations are used to numerically simulate non-steady high-incidence vortical flow about a 65 degree sweep delta wing under static roll and forced periodic roll motions. These computations have been previously reported in the literature, where emphasis was placed on validating the computational results with nonsteady experimental surface pressures, forces and moments. The emphasis of this research is to revisit these earlier computations and use nonsteady numerical flow visualization to analyze the nonlinear surface flow and vortex breakdown dynamics. Most notable are the periodic formation of surface-flow separation lines, and the periodic formation of vortex breakdown near the delta wing trailing edge.

Chaderjian, N.↗

NASA NTRS2016

Relating MBSE to Spacecraft Development: A NASA Pathfinder

The NASA Engineering and Safety Center (NESC) has sponsored a Pathfinder Study to investigate how Model Based Systems Engineering (MBSE) and Model Based Engineering (MBE) techniques can be applied by NASA spacecraft development projects. The objectives of this Pathfinder Study included analyzing both the products of the modeling activity, as well as the process and tool chain through which the spacecraft design activities are executed. Several aspects of MBSE methodology and process were explored. Adoption and consistent use of the MBSE methodology within an existing development environment can be difficult. The Pathfinder Team evaluated the possibility that an "MBSE Template" could be developed as both a teaching tool as well as a baseline from which future NASA projects could leverage. Elements of this template include spacecraft system component libraries, data dictionaries and ontology specifications, as well as software services that do work on the models themselves. The Pathfinder Study also evaluated the tool chain aspects of development. Two chains were considered: 1. The Development tool chain, through which SysML model development was performed and controlled, and 2. The Analysis tool chain, through which both static and dynamic system analysis is performed. Of particular interest was the ability to exchange data between SysML and other engineering tools such as CAD and Dynamic Simulation tools. For this study, the team selected a Mars Lander vehicle as the element to be designed. The paper will discuss what system models were developed, how data was captured and exchanged, and what analyses were conducted.

Othon, Bill↗

NASA NTRS2021

System Analysis and Generative Design for Icenode, a Buoyant Vehicle for Measuring Melt Rate Under Ice Shelves

Antarctic ice shelves buttress the Antarctic Ice Sheet from sliding into the ocean, and their collapse could trigger a meter or more of global sea level rise by the end of the century. Current state-of-the-art predictions for ice shelf behavior in a warming climate have large uncertainty, significantly hindered by a lack of in situ melt rate observations under ice shelves, especially near grounding zones. IceNode is a novel robotic vehicle under development at the NASA Jet Propulsion Laboratory to acquire such measurements, but presents a complex design problem owing to the large design space and conflicting performance requirements. Evaluating a preliminary design requires several types of tedious analysis which prevents rapid iteration and exploration of the design space. We present the implementation of a custom system analysis framework which was used to automate analysis such as resource budgeting, mission simulation, mass and buoyancy balancing, and static landing stability analysis of a given design configuration. Using this framework, we selected parameters which had the largest effects on design success and conducted a generative design study in which we programmatically varied a handful of parameters to generate 1540 different design candidates and test them across 160 different environmental scenarios. The custom built system analysis tool enabled rapid development of critical analysis and automated exploration of a large design space to guide preliminary design of the IceNode vehicle.

Gebara, Christine↗