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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

A Framework for Preliminary Design of Aircraft Structures Based on Process Information

This report discusses the general framework and development of a computational tool for preliminary design of aircraft structures based on process information. The described methodology is suitable for multidisciplinary design optimization (MDO) activities associated with integrated product and process development (IPPD). The framework consists of three parts: (1) product and process definitions; (2) engineering synthesis, and (3) optimization. The product and process definitions are part of input information provided by the design team. The backbone of the system is its ability to analyze a given structural design for performance as well as manufacturability and cost assessment. The system uses a database on material systems and manufacturing processes. Based on the identified set of design variables and an objective function, the system is capable of performing optimization subject to manufacturability, cost, and performance constraints. The accuracy of the manufacturability measures and cost models discussed here depend largely on the available data on specific methods of manufacture and assembly and associated labor requirements. As such, our focus in this research has been on the methodology itself and not so much on its accurate implementation in an industrial setting. A three-tier approach is presented for an IPPD-MDO based design of aircraft structures. The variable-complexity cost estimation methodology and an approach for integrating manufacturing cost assessment into design process are also discussed. This report is presented in two parts. In the first part, the design methodology is presented, and the computational design tool is described. In the second part, a prototype model of the preliminary design Tool for Aircraft Structures based on Process Information (TASPI) is described. Part two also contains an example problem that applies the methodology described here for evaluation of six different design concepts for a wing spar.

Rais-Rohani, Masoud↗
NASA NTRS2003

Probabilistic Evaluation of Blade Impact Damage

The response to high velocity impact of a composite blade is probabilistically evaluated. The evaluation is focused on quantifying probabilistically the effects of uncertainties (scatter) in the variables that describe the impact, the blade make-up (geometry and material), the blade response (displacements, strains, stresses, frequencies), the blade residual strength after impact, and the blade damage tolerance. The results of probabilistic evaluations results are in terms of probability cumulative distribution functions and probabilistic sensitivities. Results show that the blade has relatively low damage tolerance at 0.999 probability of structural failure and substantial at 0.01 probability.

Chamis, C. C.↗
NASA NTRS2004

Reliability Quantification of the Flexure: A Critical Stirling Convertor Component

Uncertainties in the manufacturing, fabrication process, material behavior, loads, and boundary conditions results in the variation of the stresses and strains induced in the flexures and its fatigue life. Past experience and the test data at material coupon levels revealed a significant amount of scatter of the fatigue life. Owing to these facts, the design of the flexure, using conventional approaches based on safety factor or traditional reliability based on similar equipment considerations does not provide a direct measure of reliability. Additionally, it may not be feasible to run actual long term fatigue tests due to cost and time constraints. Therefore it is difficult to ascertain material fatigue strength limit. The objective of the paper is to present a methodology and quantified results of numerical simulation for the reliability of flexures used in the Stirling convertor for their structural performance. The proposed approach is based on application of finite element analysis method in combination with the random fatigue limit model, which includes uncertainties in material fatigue life. Additionally, sensitivity of fatigue life reliability to the design variables is quantified and its use to develop guidelines to improve design, manufacturing, quality control and inspection design process is described.

Shah, Ashwin R.↗
NASA NTRS2011

Two-Dimensional Nonlinear Finite Element Analysis of CMC Microstructures

Detailed two-dimensional finite element analyses of the cross-sections of a model CVI (chemical vapor infiltrated) SiC/SiC (silicon carbide fiber in a silicon carbide matrix) ceramic matrix composites are performed. High resolution images of the cross-section of this composite material are generated using serial sectioning of the test specimens. These images are then used to develop very detailed finite element models of the cross-sections using the public domain software OOF2 (Object Oriented Analysis of Material Microstructures). Examination of these images shows that these microstructures have significant variability and irregularity. How these variabilities manifest themselves in the variability in effective properties as well as the stress distribution, damage initiation and damage progression is the overall objective of this work. Results indicate that even though the macroscopic stress-strain behavior of various sections analyzed is very similar, each section has a very distinct damage pattern when subjected to in-plane tensile loads and this damage pattern seems to follow the unique architectural and microstructural details of the analyzed sections.

Mital, Subodh K.↗
NASA NTRS2011

Geochemical Mapping of 4 Vesta Begins

By December, the NASA Dawn spacecraft will have descended to a low altitude mapping orbit (LAMO), where the Gamma Ray and Neutron Detector (GRaND) will acquire global mapping data for up to four months. Measurements by GRaND will help answer elusive questions about how Vesta differentiated and the nature of processes that shaped Vesta s surface. The data will be analyzed to determine the abundances of Mg, Si, Fe, K, Th, and H at a spatial resolution of roughly 300 km full-width-at-half-maximum from a 465 km radius orbit. Thermal and fast neutron counting data will be analyzed to determine the neutron macroscopic absorption cross section and average atomic mass, providing constraints on additional elements, such as Ca and Al. GRaND will quantify the elemental composition of coarse spatial units identified by Dawn s Framing Camera (FC) and the Visible & Infrared Spectrometer (VIR). In addition, GRaND will map the mixing ratio of compositional end members selected from the howardite, eucrite and diogenite (HED) meteorites, determine the relative proportions of plagioclase and mafic minerals, and search for compositions that are absent or under-represented in the meteorite collection. While it is generally thought that Vesta s crust on a regional scale should be well-represented by linear mixing of HED whole-rock compositions, there are hints that Vesta may be more diverse than implied by this model. For example, the discovery of K-rich impact glasses in howardites suggests that K-rich rocks may be present on a portion of Vesta s surface, and the analysis of diogenites indicates considerable variability in the magmatic processes that formed them. The chemical composition of materials within Vesta s south polar structure may provide further clues to how it formed. An impact might have exposed mantle and lower crustal materials, which should have a distinctive compositional signature. We present the analysis of data acquired by GRaND from cruise through the descent to LAMO, including GRaND s sensitivity to different elements and geochemical processes.

Prettyman, Thomas H.↗
NASA NTRS1989

Prediction of fatigue-crack growth in a high-strength aluminum alloy under variable-amplitude loading

The present paper is concerned with the application of an analytical crack-closure model to study crack growth under various load histories. The model was based on a crack-tip plasticity concept like the Dugdale model, but modified to leave plastically deformed material in the wake of the advancing crack tip. The effect of material thickness on plasticity was accounted for by using a constraint factor on tensile yielding at the crack tip. The model was used to correlate crack-growth rates under constant-amplitude loading, and to predict crack growth under variable-amplitude loading on a high-strength aluminum alloy (7475-T7351) sheet material. The experimental data were obtained from Zhang et al. Predicted crack-growth lives agreed well with experimental data. For ten crack-growth tests subjected to various variable-amplitude load histories, the ratio of predicted-to-experimental lives ranged from 0.54 to 1.19. The mean value of the ratio of predicted-to-experimental lives was 0.95 and the standard error was 0.2 using a constraint factor of 1.9 in the model. Crack-opening stresses calculated from the model were significantly different from those determined by Zhang et al. using a striation-based experimental method.

Newman, J. C., Jr.↗
NASA NTRS2010

Stable Chlorine Isotope Study: Application to Early Solar System Materials

A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the Cl-37/Cl-35 ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For example, almost no differences of Cl isotope composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl isotope variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl isotope analyses are now required to confirm real chlorine isotope variations for planetary materials including carbonaceous chondrites [5]. A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the 37Cl/35Cl ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For eample, almost no differences of Cl isotope composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl isotope variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl isotope analyses are now required to confirm real chlorine isotope variations for planetary materials including carbonaceous chondrites [5]. In order to clarify the stable chlorine isotope features of early solar system materials, we have initiated development of the TIMS technique at NASA JSC applicable to analysis of small amounts of meteoritic and planetary materials. We report here the current status of chlorine isotope analysis at NASA JSC.

Mala,ira. M/↗
NASA NTRS1946

Correlation between strength properties in standard test specimens and molded phenolic parts

This report describes an investigation of the tensile, flexural, and impact properties of 10 selected types of phenolic molding materials. The materials were studied to see in what ways and to what extent their properties satisfy some assumptions on which the theory of strength of materials is based: namely, (a) isotropy, (b) linear stress-strain relationship for small strains, and (c) homogeneity. The effect of changing the dimensions of tensile and flexural specimens and the span-depth ratio in flexural tests were studied. The strengths of molded boxes and flexural specimens cut from the boxes were compared with results of tests on standard test specimens molded from the respective materials. The nonuniformity of a material, which is indicated by the coefficient of variation, affects the results of tests made with specimens of different sizes and tests with different methods of loading. The strength values were found to depend on the relationship between size and shape of the molded specimen and size and shape of the fillers. The most significant variations observed within a diversified group of materials were found to depend on the orientation of fibrous fillers. Of secondary importance was the dependence of the variability of test results on the pieces of filler incorporated into the molding powder as well as on the size of the piece. Static breaking strength tests on boxes molded from six representative phenolic materials correlated well with falling-ball impact tests on specimens cut from molded flat sheets. Good correlation was obtained with Izod impact tests on standard test specimens prepared from the molding materials. The static breaking strengths of the boxes do not correlate with the results of tensile or flexural tests on standard specimens.

MATERIALS, MONSANTO RESINOX↗
NASA NTRS1990

Automation software for a materials testing laboratory

The software environment in use at the NASA-Lewis Research Center's High Temperature Fatigue and Structures Laboratory is reviewed. This software environment is aimed at supporting the tasks involved in performing materials behavior research. The features and capabilities of the approach to specifying a materials test include static and dynamic control mode switching, enabling multimode test control; dynamic alteration of the control waveform based upon events occurring in the response variables; precise control over the nature of both command waveform generation and data acquisition; and the nesting of waveform/data acquisition strategies so that material history dependencies may be explored. To eliminate repetitive tasks in the coventional research process, a communications network software system is established which provides file interchange and remote console capabilities.

Mcgaw, Michael A.↗
NASA NTRS1995

Wear Measurement System

Lewis Research Center developed a tribometer for in-house wear tests. Implant Sciences Corporation (ISC), working on a NASA contract to develop coatings to enhance the wear capabilities of materials, adapted the tribometer for its own use and developed a commercial line of user-friendly systems. The ISC-200 is a pin-on-disk type of tribometer, functioning like a record player and creating a wear groove on the disk, with variables of speed and load. The system can measure the coefficient of friction, the wear behavior between materials, and the integrity of thin films or coatings. Applications include measuring wear on contact lenses and engine parts and testing disk drives.

Source record↗
NASA NTRS2010

Micromechanics Modeling of Composites Subjected to Multiaxial Progressive Damage in the Constituents

The high-fidelity generalized method of cells composite micromechanics model is extended to include constituent-scale progressive damage via a proposed damage model. The damage model assumes that all material nonlinearity is due to damage in the form of reduced stiffness, and it uses six scalar damage variables (three for tension and three for compression) to track the damage. Damage strains are introduced that account for interaction among the strain components and that also allow the development of the damage evolution equations based on the constituent material uniaxial stress strain response. Local final-failure criteria are also proposed based on mode-specific strain energy release rates and total dissipated strain energy. The coupled micromechanics-damage model described herein is applied to a unidirectional E-glass/epoxy composite and a proprietary polymer matrix composite. Results illustrate the capability of the coupled model to capture the vastly different character of the monolithic (neat) resin matrix and the composite in response to far-field tension, compression, and shear loading.

Bednarcyk, Brett A.↗
NASA NTRS1989

Prediction of fatigue-crack growth in a high-strength aluminum alloy under variable-amplitude loading

The present paper is concerned with the application of an analytical crack-closure model to study crack growth under various load histories. The model was based on a concept like the Dugdale model, but modified to leave plastically deformed material in the wake of the advancing crack tip. The thickness effect was accounted for by using a 'constraint' factor on tensile yielding at the crack tip. The model was used to correlate crack-growth rates under constant-amplitude loading, and to predict crack growth under variable-amplitude loading on a high-strength aluminum alloy (7475-T7351) sheet material. The experimental data was obtained from Zhang et al. Predicted crack-growth lives agreed well with experimental data. For ten crack-growth tests subjected to various variable-amplitude load histories, the ratio of predicted-to-experimental lives ranged from 0.54 to 1.19. The mean value of predicted-to-experimental lives was 0.95 with a standard error of 0.2 for a constraint factor of 1.9.

Newman, J. C., Jr.↗
NASA NTRS2001

Nonlinear Thermomechanical Response of Composite Panels with Continuous and Terminated Stiffeners

A two-phase approach and a computational procedure are used for predicting the variability of the response of stiffened composite panels associated with variations in the geometric and material parameters of the structures. In the first phase, hierarchical sensitivity analysis is used to identify the major parameters that have the most effect on the response quantities of interest. In the second phase, the major parameters are taken to be fuzzy parameters, and a fuzzy set analysis is used to determine the range of variation of the response, associated with preselected variations in the major parameters. Numerical results are presented showing the variability of the response of panels with both continuous and terminated stiffeners associated with variations in the micro mechanical and geometric parameters. Both flat and curved panels are considered.

Noor, Ahmed K.↗
NASA NTRS2010

Life Support with Failures and Variable Supply

The life support system for long duration missions will recycle oxygen and water to reduce the material resupply mass from Earth. The impact of life support failures was investigated by dynamic simulation of a lunar outpost habitat life support model. The model was modified to simulate resupply delays, power failures, recycling system failures, and storage failures. Many failures impact the lunar outpost water supply directly or indirectly, depending on the water balance and water storage. Failure effects on the water supply are reduced if Extra Vehicular Activity (EVA) water use is low and the water supply is ample. Additional oxygen can be supplied by scavenging unused propellant or by production from regolith, but the amounts obtained can vary significantly. The requirements for oxygen and water can also vary significantly, especially for EVA. Providing storage buffers can improve efficiency and reliability, and minimize the chance of supply failing to meet demand. Life support failures and supply variations can be survivable if effective solutions are provided by the system design

Jones, Harry↗
NASA NTRS1977

Evaluation of aircraft brake materials

A test program was carried out to evaluate several new high-temperature friction materials for use in aircraft disk brakes. A specially built test apparatus utilizing a disk brake and wheel half from a small jet aircraft was used. The apparatus enabled control of brake pressure, velocity and braking time. Tests were run under both constant and variable velocity conditions and covered a kinetic energy range similar to that encountered in aircraft brake service. The materials evaluation showed that two newly developed friction materials show potential for use in aircraft disk brakes. One of the materials is a nickel-based sintered composite, while the other is a molybdenum-based material. Both materials show much lower wear rates than conventional copper-based materials and are better able to withstand the high temperatures encountered during braking. Additional materials improvement is necessary, however, since both materials show a significant negative slope of the friction-velocity curve at low velocities.

Ho, T. L.↗
NASA NTRS2012

Radial Internal Material Handling System (RIMS) for Circular Habitat Volumes

A Radial Internal Material Handling System (RIMS) has been developed to service a circular floor area in variable gravity. On planetary surfaces, pressurized human habitable volumes will require a means to carry heavy equipment between various locations within the volume of the habitat, regardless of the partial gravity (Earth, moon, Mars, etc). On the NASA Habitat Demonstration Unit (HDU), a vertical cylindrical volume, it was determined that a variety of heavy items would need to be carried back and forth from deployed locations to the General Maintenance Work Station (GMWS) when in need of repair, and other equipment may need to be carried inside for repairs, such as rover parts and other external equipment. The vertical cylindrical volume of the HDU lent itself to a circular overhead track and hoist system that allows lifting of heavy objects from anywhere in the habitat to any other point in the habitat interior. In addition, the system is able to hand off lifted items to other material handling systems through the side hatches, such as through an airlock. This paper describes the RIMS system which is scalable for application in a variety of circular habitat volumes.

deep space habitats↗
NASA NTRS1977

A method to estimate weight and dimensions of aircraft gas turbine engines. Volume 1: Method of analysis

Weight and envelope dimensions of aircraft gas turbine engines are estimated within plus or minus 5% to 10% using a computer method based on correlations of component weight and design features of 29 data base engines. Rotating components are estimated by a preliminary design procedure where blade geometry, operating conditions, material properties, shaft speed, hub-tip ratio, etc., are the primary independent variables used. The development and justification of the method selected, the various methods of analysis, the use of the program, and a description of the input/output data are discussed.

Pera, R. J.↗