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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.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Probabilistic structural analysis: Introductory remarks

The development of probabilistic structural analysis methodology consists of the following program elements: (1) composite load spectra models, (2) computational probabilistic structural analysis methods, and (3) probabilistic constitutive relationships. The development of the probabilistic structural analysis methodology is a joint program of NASA Lewis in-house and sponsored research. The objective of this session is to illustrate recent progress on the application of this methodology to determine the reliability of structural components for rocket propulsion systems. The session contains descriptions of and progress reports on the following specific activities: (1) The NESSUS computer code, (2) approximate methods, (3) advanced methods, (4) composite load spectra applications, (5) probabilistic fracture mechanisms, and (6) probability of failure and risk analysis. Collectively, the progress to date demonstrates that the structural durability of hot engine structural components can be effectively evaluated in a formal probabilistic/reliability framework.

Chamis, Christos C.↗
NASA NTRS1991

Structural design methodologies for ceramic-based material systems

One of the primary pacing items for realizing the full potential of ceramic-based structural components is the development of new design methods and protocols. The focus here is on low temperature, fast-fracture analysis of monolithic, whisker-toughened, laminated, and woven ceramic composites. A number of design models and criteria are highlighted. Public domain computer algorithms, which aid engineers in predicting the fast-fracture reliability of structural components, are mentioned. Emphasis is not placed on evaluating the models, but instead is focused on the issues relevant to the current state of the art.

Duffy, Stephen F.↗
NASA NTRS1992

Structural design methodologies for ceramic-based material systems

One of the primary pacing items for realizing the full potential of ceramic-based structural components is the development of new design methods and protocols. The focus here is on low temperature, fast-fracture analysis of monolithic, whisker-toughened, laminated, and woven ceramic composites. A number of design models and criteria are highlighted. Public domain computer algorithms, which aid engineers in predicting the fast-fracture reliability of structural components, are mentioned. Emphasis is not placed on evaluating the models, but instead is focused on the issues relevant to the current state of the art.

Duffy, Stephen F.↗
NASA NTRS1985

Analytical simulation of weld effects in creep range

The inelastic analysis procedure used to investigate the effect of welding on the creep rupture strength of a typical Liquid Metal Fast Breeder Reactor (LMFBR) nozzle is discussed. The current study is part of an overall experimental and analytical investigation to verify the inelastic analysis procedure now being used to design LMFBR structural components operating at elevated temperatures. Two important weld effects included in the numerical analysis are: (1) the residual stress introduced in the fabrication process; and (2) the time-independent and the time-dependent material property variations. Finite element inelastic analysis was performed on a CRAY-1S computer using the ABAQUS program with the constitutive equations developed for the design of LMFBR structural components. The predicted peak weld residual stresses relax by as much as 40% during elevated temperature operation, and their effect on creep-rupture cracking of the nozzle is considered of secondary importance.

Dhalla, A. K.↗
NASA NTRS1997

Testing for Random Limit Load Versus Static Limit Load

This document is an effort to report the basic test findings in an ongoing quest for understanding how random load factors should be applied to structural components in order to verify the strength of space flight hardware. A Spacelab experiment known as the Atmospheric Emission Photometric Imager (AEPI) was subjected to both an expected flight random environment and the associated Miles' equation equivalent static load. During each of these tests, the fiberglass pedestal was instrumented with 16 triaxial strain gauges around its base. Component strains and invariant stresses were compared. As seen previously in other hardware tests, the stress distribution from the random environment was an order of magnitude below the comparable static stresses. With a proposed data acquisition system, a strain database will be developed that will quantify an empirical relationship between dynamic and static limit stresses. This event will allow a more accurate estimate of launch environment effects on new technology structural components.

Lee, H. M.↗
NASA NTRS1985

Automatic assembly of space stations

A problem in the automatic assembly of space stations is the determination of guidance laws for the terminal rendezvous and docking of two structural components or modules. The problem involves the feedback control of both the relative attitude and translational motion of the modules. A suitable mathematical model based on rigid body dynamics was used. The basic requirements, physical constraints and difficulties associated with the control problem are discussed. An approach which bypasses some of the difficulties is proposed. A nonlinear guidance law satisfying the basic requirements is derived. The implementation requirements is discussed. The performance of the resulting feedback control system with rigid and flexible structural components is studied by computer simulation.

Wang, P. K. C.↗
NASA NTRS1998

A Long-Term Space Astrophysics Research Program. An X-Ray Perspective of the Components and Structure of Galaxies

We present optical and archival X-ray data on the disturbed morphology radio elliptical NGC 1316 (Fornax A) that displays numerous low surface brightness shells, loops and tails. An extended (81x27 min or 9x3 kpc) emission line region (EELR) at a projected distance of 35 kpc from the nucleus has been discovered in a approximately 9Ox35 kpc, approximately 3.Ox1O(solar luminosity(B)) tidal tail. The position and extreme size of the EELR suggest it is related to the merger process. We suggest that the ionization mechanism of the EELR is shock excitation, and the gas is remnant from the merger progenitor. X-ray emission is detected near two tidal tails. Hot, approximately 5 x 10(exp 6)K gas is probably the predominant gas component in the tidal tail ISM. However based on the current tidal tail (cold + warm + hot) gas mass, a large fraction of the tidal tail progenitor gas may already reside in the nucleus of NGC 1316. The numerous and varied tidal tail system suggests that a disk-disk or disk-E merger could have taken place greater than or equal to 1 Gyr ago, whilst a low mass, gas rich galaxy started to merge approximately 0.5 Gyr ago.

Fabbiano, G.↗
NASA NTRS1997

Dynamic Analysis With Stress Mode Animation by the Integrated Force Method

Dynamic animation of stresses and displacements, which complement each other, can be a useful tool in the analysis and design of structural components. At the present time only displacement-mode animation is available through the popular stiffness formulation. This paper attempts to complete this valuable visualization tool by augmenting the existing art with stress mode animation. The reformulated method of forces, which in the literature is known as the integrated force method (IFM), became the analyzer of choice for the development of stress mode animation because stresses are the primary unknowns of its dynamic analysis. Animation of stresses and displacements, which have been developed successfully through the IFM analyzers, is illustrated in several examples along with a brief introduction to IFM dynamic analysis. The usefulness of animation in design optimization is illustrated considering the spacer structure component of the International Space Station as an example. An overview of the integrated force method analysis code (IFM/ANALYZERS) is provided in the appendix.

Patnaik, Surya N.↗
NASA NTRS1975

Description of a computerized method for predicting thermal fatigue life of metals

A computer program called TFLIFE is described which can be used to predict the thermal fatigue life of metals and structural components from conventional metal properties. This program is used as a subroutine with a main program supplied by the user. The main program calculates input cycles of temperature and total strain for TFLIFE which then calculates a stress cycle, creep and plastic strain damage, and cyclic life. A unique feature of TFLIFE is that it calculates lives according to several different failure criteria for the same input data. These criteria are surface crack initiation, interior crack initiation, and complete fracture of both unnotched and notched fatigue specimens. Results are presented for two typical problems: thermal-mechanical fatigue of bar specimens of the tantalum alloy T-111 and thermal-stress fatigue of wedge specimens of the nickel alloy B-1900. The computer program is now ready for more extensive evaluation on structural components and additional laboratory specimens.

Spera, D. A.↗
DOE OSTI2021

Draft Rules for Alloy 617 Creep-Fatigue Design Using an EPP+SMT Approach

The report describes an improved new creep-fatigue design method for structural components in high temperature nuclear service. The new method uses an integrated elastic-perfectly plastic (EPP) analysis and Simplified Model Test (SMT) approach that greatly simplifies the design process by avoiding the separate evaluation of creep and fatigue damages and eliminating the requirement of stress classification. The report includes draft design rules, presented in a format compatible with an ASME nuclear Code Case, as well as a commentary on the rules and the validation of the rules using pressurized SMT (p-SMT) test data. Areas of potential improvement have been identified for further evaluation. The report also develops EPP+SMT design charts for Alloy 617 at temperatures between 800°C and 950°C by extrapolating high strain range, short hold test data to low strain range and long hold times, typical for structural components in high temperature nuclear service. The design charts are currently limited to 10,000 cycles to avoid excessive extrapolation outside the test database. More robust alternate extrapolation procedures will be considered in future work. The report includes several verification problems comparing the new EPP+SMT design method with current ASME creep-fatigue design methods. The comparison demonstrates that the EPP+SMT method significantly reduces the over-conservatism in current methods. Finally, the report includes a fully-documented sample problem with multiple load cases detailing the application of proposed EPP+SMT design rules.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Advanced Metal Foam Structures for Outer Space

A document discusses a proposal to use advanced materials especially bulk metallic glass (BMG) foams in structural components of spacecraft, lunar habitats, and the like. BMG foams, which are already used on Earth in some consumer products, are superior to conventional metal foams: BMG foams have exceptionally low mass densities and high strength-to-weight ratios and are more readily processable into strong, lightweight objects of various sizes and shapes. These and other attractive properties of BMG foams would be exploited, according to the proposal, to enable in situ processing of BMG foams for erecting and repairing panels, shells, containers, and other objects. The in situ processing could include (1) generation of BMG foams inside prefabricated deployable skins that would define the sizes and shapes of the objects thus formed and (2) thermoplastic deformation of BMG foams. Typically, the generation of BMG foams would involve mixtures of precursor chemicals that would be subjected to suitable pressure and temperature schedules. In addition to serving as structural components, objects containing or consisting of BMG foams could perform such functions as thermal management, shielding against radiation, and shielding against hypervelocity impacts of micrometeors and small debris particles.

Hanan, Jay↗
NASA NTRS2010

Hardware-Based Non-Optimum Factors for Launch Vehicle Structural Design

During aerospace vehicle conceptual and preliminary design, empirical non-optimum factors are typically applied to predicted structural component weights to account for undefined manufacturing and design details. Non-optimum factors are developed here for 32 aluminum-lithium 2195 orthogrid panels comprising the liquid hydrogen tank barrel of the Space Shuttle External Tank using measured panel weights and manufacturing drawings. Minimum values for skin thickness, axial and circumferential blade stiffener thickness and spacing, and overall panel thickness are used to estimate individual panel weights. Panel non-optimum factors computed using a coarse weights model range from 1.21 to 1.77, and a refined weights model (including weld lands and skin and stiffener transition details) yields non-optimum factors of between 1.02 and 1.54. Acreage panels have an average 1.24 non-optimum factor using the coarse model, and 1.03 with the refined version. The observed consistency of these acreage non-optimum factors suggests that relatively simple models can be used to accurately predict large structural component weights for future launch vehicles.

Wu, K. Chauncey↗
NASA NTRS1972

Assessment of and standardization for quantitative nondestructive test

Present capabilities and limitations of nondestructive testing (NDT) as applied to aerospace structures during design, development, production, and operational phases are assessed. It will help determine what useful structural quantitative and qualitative data may be provided from raw materials to vehicle refurbishment. This assessment considers metal alloys systems and bonded composites presently applied in active NASA programs or strong contenders for future use. Quantitative and qualitative data has been summarized from recent literature, and in-house information, and presented along with a description of those structures or standards where the information was obtained. Examples, in tabular form, of NDT technique capabilities and limitations have been provided. NDT techniques discussed and assessed were radiography, ultrasonics, penetrants, thermal, acoustic, and electromagnetic. Quantitative data is sparse; therefore, obtaining statistically reliable flaw detection data must be strongly emphasized. The new requirements for reusable space vehicles have resulted in highly efficient design concepts operating in severe environments. This increases the need for quantitative NDT evaluation of selected structural components, the end item structure, and during refurbishment operations.

Neuschaefer, R. W.↗
NASA NTRS1983

Metallized coatings for corrosion control of Naval ship structures and components

In attempting to improve corrosion control, the U.S. Navy has undertaken a program of coating corrosion-susceptible shipboard components with thermally sprayed aluminum. In this report the program is reviewed in depth, including examination of processes, process controls, the nature and properties of the coatings, nondestructive examination, and possible hazards to personnel. The performance of alternative metallic coating materials is also discussed. It is concluded that thermally sprayed aluminum can provide effective long-term protection against corrosion, thereby obviating the need for chipping of rust and repainting by ship personnel. Such coatings are providing excellent protection to below-deck components such as steam valves, but improvements are needed to realize the full potential of coatings for above-deck service. Several recommendations are made regarding processes, materials, and research and development aimed at upgrading further the performance of these coatings.

Source record↗
NASA NTRS1984

Optimization of space structures

Computational methods for the design of structures for specified transient response, truss beam units with specified attached vibration absorbers, and laminates for structural components of large space structures are examined. Equations for the measurement of structural stiffness that are maximized for a specific total mass and that will reduce the structural weight are presented. A model for a cantilevered space truss beam of a specific mass and with a specified tip vibration absorber is explained. Design criteria of the laminates include minimizing the weight as well as frequency, buckling, and global stiffness constraints. Other variables include orientation of the lamina and the thickness of each layer.

Reiss, R.↗
NASA NTRS1985

SCARE: A post-processor program to MSC/NASTRAN for the reliability analysis of structural ceramic components

A computer program was developed for calculating the statistical fast fracture reliability and failure probability of ceramic components. The program includes the two-parameter Weibull material fracture strength distribution model, using the principle of independent action for polyaxial stress states and Batdorf's shear-sensitive as well as shear-insensitive crack theories, all for volume distributed flaws in macroscopically isotropic solids. Both penny-shaped cracks and Griffith cracks are included in the Batdorf shear-sensitive crack response calculations, using Griffith's maximum tensile stress or critical coplanar strain energy release rate criteria to predict mixed mode fracture. Weibull material parameters can also be calculated from modulus of rupture bar tests, using the least squares method with known specimen geometry and fracture data. The reliability prediction analysis uses MSC/NASTRAN stress, temperature and volume output, obtained from the use of three-dimensional, quadratic, isoparametric, or axisymmetric finite elements. The statistical fast fracture theories employed, along with selected input and output formats and options, are summarized. An example problem to demonstrate various features of the program is included.

Gyekenyesi, J. P.↗