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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A probabilistic approach to the evaluation of fatigue damage in a space propulsion system injector element

The fatigue damage of a space propulsion system component is computed using probabilistic structural analysis methods. The analysis takes into account the variations in static and dynamic loads, the uncertainty in structural damping, and the scatter in material fatigue resistance. The key elements of the probabilistic approach include: (1) a numerical engine model for describing the global component interface loads consistent with engine balance, (2) models for computing the local mode boundary conditions on the component, (3) a static structural analysis model that captures the strains at a damage critical location as a function of engine performance variables, (4) a finite element model for assessment of the random amplitude stress response due to random base and pressure excitations with uncertain power and correlation length, and (5) advanced first order reliability methods for computing the probabilities associated with the fatigue damage.

Rajagopal, K. R.↗
NASA NTRS1987

Nonlinear heat transfer and structural analyses of SSME turbine blades

Three-dimensional nonlinear finite-element heat transfer and structural analyses were performed for the first stage high-pressure fuel turbopump blade of the space shuttle main engine (SSME). Directionally solidified (DS) MAR-M 246 material properties were considered for the analyses. Analytical conditions were based on a typical test stand engine cycle. Blade temperature and stress-strain histories were calculated using MARC finite-element computer code. The study was undertaken to assess the structural response of an SSME turbine blade and to gain greater understanding of blade damage mechanisms, convective cooling effects, and the thermal-mechanical effects.

Abdul-Aziz, A.↗
NASA NTRS1990

New heterojunction LWIR detector options

Researchers investigate the heterojunction internal photoemission (HIP) approach that potentially offers long wavelength infrared (LWIR) photovoltaic detector performance (single pixel) that is competitive with the best of other approaches being considered. Most significantly, this approach offers a relatively simple device technology that promises producible and uniform FPA's. Researchers emphasize an exciting process based on intervalence band absorption. They investigate both III-V and Si-based heterojunctions grown by molecular beam epitaxy (MBE) in which the barrier can be tailored to the desired cutoff wavelength. In addition, MBE allows one to optimize the device structure with precise control of doping profiles and layer thicknesses, and perform band structure engineering by control of composition and heterojunction strain. Researchers also consider free carrier absorption in heterojunctions. Acceptable absorption coefficients can be achieved in very heavily n(exp +) doped semiconductor layers (approx. equals 10(exp 20)cm(exp -3). However, in this case the appreciable filling of conduction band states leads to a Schottky-like photoresponse with a gradual (quadratic) turn-on above threshold. A more satisfactory approach would be to use p(exp +) doping so that with the higher density of states in the heavy hole valence band there would be a narrow band of occupied states. This gives the desirable effect of a more rapid (linear) turn-on above threshold. Unfortunately, the higher hole effective mass also reduces (inversely) the free carrier absorption. For this and other reasons, the intervalence band absorption process looks much more promising.

Maserjian, Joseph↗
NASA NTRS1991

Hierarchic Extensions in the Static and Dynamic Analysis of Elastic Beams

Approximate solutions of static and dynamic beam problems by the p-version of the finite element method are investigated. Within a hierarchy of engineering beam idealizations, rigorous formulations of the strain and kinetic energies for straight and circular beam elements are presented. These formulations include rotating coordinate system effects and geometric nonlinearities to allow for the evaluation of vertical axis wind turbines, the motivating problem for this research. Hierarchic finite element spaces, based on extensions of the polynomial orders used to approximate the displacement variables, are constructed. The developed models are implemented into a general purpose computer program for evaluation. Quality control procedures are examined for a diverse set of sample problems. These procedures include estimating discretization errors in energy norm and natural frequencies, performing static and dynamic equilibrium checks, observing convergence for qualities of interest, and comparison with more exacting theories and experimental data. It is demonstrated that p-extensions produce exponential rates of convergence in the approximation of strain energy and natural frequencies for the class of problems investigated.

Watson, Robert A.↗
NASA NTRS1992

Creep fatigue life prediction for engine hot section materials (isotropic)

A series of high temperature strain controlled fatigue tests have been completed to study the effects of thermomechanical fatigue, multiaxial loading, reactive environments, and imposed mean stresses. The baseline alloy used in these tests was cast B1900+Hf (with and without coatings); a small number of tests of wrought INCO 718 are also included. A strong path dependence was demonstrated during the thermomechanical fatigue testing, using in-phase, out-phase, and non-proportional (elliptical and 'dogleg') strain-temperature cycles. The multiaxial tests also demonstrated cycle path to be a significant variable, using both proportional and non-proportional tension-torsion loading. Environmental screening tests were conducted in moderate pressure oxygen and purified argon; the oxygen reduced the specimen lives by two, while the argon testing produced ambiguous data. Both NiCoCrAlY overlay and diffusion aluminide coatings were evaluated under isothermal and TMF conditions; in general, the lives of the coated specimens were higher that those of uncoated specimens. Controlled mean stress TMF tests showed that small mean stress changes could change initiation lives by orders of magnitude; these results are not conservatively predicted using traditional linear damage summation rules. Microstructures were evaluated using optical, SEM and TEM methods.

Nelson, R. S.↗
NASA NTRS1984

Evaluation results of the 700 deg C Chinese strain gages

There is a continuing interest and need for resistance strain gages capable of making static strain measurements on components located in the hot section of gas turbine engines. A paper by Tsen-tai Wu describes the development and evaluation of high temperature gauges fabricated from specially developed Fe-Cr-Al-V-Ti-Y alloy wire. Several of these gages and a quantity of P12-2 ceramic adhesive were purchased for evaluation. Nine members of the aircraft turbine engine community were invited to participate in an evaluation of these gages. Each participant was sent one strain gage, a small amount of ceramic adhesive, instructions for mounting the gage on a test beam, and a set of suggestions for the experiment. Data on gage factor variation with temperature, apparent strain, and drift are discussed.

Hobart, H. F.↗
NASA NTRS2012

Can Terrestrial Microbes Grow on Mars?

The theme for AbSciCon 2012 is "Exploring Life: Past and Present, Near and Far." The conference will address our current understanding of life - from processes at the molecular level to those which operate at planetary scales. Studying these aspects of life on Earth provides an essential platform from which to examine the potential for life on other worlds, both within our solar system and beyond. Mars exhibits a variety of extreme environments characterized by high UV and ionizing radiation flux, low pressure anoxic atmosphere, scarce or absent liquid water, extreme low temperatures, etc. The ability of terrestrial microorganisms to survive and adapt to the Mars environment has profound implications for astrobiology, planetary protection, and Mars life detection missions. At the NASA Ames Synthetic Biology Initiative, we believe that synthetic biology has the potential to revolutionize human space exploration. As such, the initiative is dedicated to applying the tools and techniques of synthetic biology to space exploration and astrobiology. Biological solutions will be invaluable for space exploration because they are not resource intensive, and they are versatile and self-renewing. An understanding of how to work with DNA in an unfavorable environment is paramount to utilizing biological tools on space missions. Furthermore, the ability to adjust life to the parameters of Mars is vital both to discovering what life on Mars might look like, and to using biological tools under such conditions. As a first step, we need an energy-efficient, low cost means of transporting, storing, and protecting genomic DNA, DNA parts, and whole microbial strains. Our goal is to develop and demonstrate viable and superior alternatives to standard DNA storage methods, which can be optimized to the conditions of space exploration, using synthetic biology as a tool. This includes protocols and kit designs for easy and repeatable DNA and strain recovery from protective storage conditions. We are constructing newly engineered genetic parts for different valuable host organisms, designed to increased long-term survival and functional retention. These methods should be applied for DNA and strain storage and transportation. In parallel, we seek inspiration from natural organisms that have developed means for survival in extreme environmental conditions. We are utilizing novel techniques for analysis of lipid biomarkers in the Antarctic Dry Valleys in order to identify resident microbes in the Antarctic soil and permafrost, as well as biomarker fossils of organisms that survived in the valleys in ages past. Through the identification of these life forms, we hope to understand and draw on new biological tools and strategies for synthetic biological applications on Mars.

Rothschild, Lynn↗
NASA NTRS1983

HOST structural analysis program overview

Hot section components of aircraft gas turbine engines are subjected to severe thermal structural loading conditions, especially during the start up and take off portions of the engine cycle. The most severe and damaging stresses and strains are those induced by the steep thermal gradients induced during the start up transient. These transient stresses and strains are also the most difficult to predict, in part because of the temperature gradients and distributions are not well known or readily predictable, and also because the cyclic elastic viscoplastic behavior of the materials at these extremes of temperature and strain are not well known or readily predictable. A broad spectrum of structures related technology programs is underway to address these deficiencies. One element of the structures program is developing improved time varying thermal mechanical load models for the entire engine mission cycle from start up to shutdown. Another major part of the program is the development of new and improved nonlinear 3-D finite elements and associated structural analysis programs, including the development of temporal elements with time dependent properties to account for creep effects in the materials and components.

Johns, R. H.↗
NASA NTRS2003

Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of hydrostatic stresses. An important discovery in the course of this work was that the hydrostatic stress effects varied during the loading process, which needed to be accounted for within the constitutive equations. The model is characterized primarily by shear data, with tensile data used to characterize the hydrostatic stress effects.

Goldberg, Robert K.↗
NASA NTRS1990

PdCr Based High Temperature Static Strain Gage

The program at NASA Lewis Research Center to develop a high temperature static strain gage system for the hypersonic vehicle and turbine engine research has emphasized a palladium- 13wt%chromium (PdCr) alloy. Gages made from this alloy are being developed in both fine wire and thin film form. The wire gage system had platinum wire as a temperature compensator and was coated with a special alumina and zirconia mixture overcoat. This PdCr compensated wire gage responded linearly to the imposed strain to at least i000 microstrain. The strain sensitivity of the gage did not vary much with temperature. The apparent strain of this compensated gage was significantly lower than that of the other gages. It varied within 300 microstrain from room temperature to 800 deg. C with a reproducibility within 50 microstrain between thermal cycles to 800 deg. C. This is a significant advance over the 400 deg. C barrier of previous techniques for resistance static strain gages. The sputtered thin film PdCr strain gage, whose size was 8x8 mm and 10 micron thick, has demonstrated the possibility of extending the use of the PdCr strain gage to a temperature of approximately 1000 deg. C.

Lei, Jih-Fen↗
NASA NTRS1990

PdCr based high temperature static strain gage

The program at NASA Lewis Research Center to develop a high temperature static strain gage system for the hypersonic vehicle and turbine engine research has emphasized a palladium-13 wt pct chromium (PdCr) alloy. Gages made from this alloy are being developed in both fine wire and thin film form. The wire gage system had platinum wire as a temperature compensator and was coated with a special alumina and zirconia mixture overcoat. This PdCr compensated wire gage responded linearly to the imposed strain to at least 1000 microstrain. The apparent strain varied within 300 microstrain from room temperature to 800 C with a reproducibility within 50 microstrain between thermal cycles to 800 C. The sputtered thin film PdCr strain gage, whose size was 8 x 8 mm and 10 microns thick, has demonstrated the possibility of extending the use of the PdCr strain gage to a temperature of approximately 1000 C.

Lei, Jih-Fen↗
NASA NTRS2005

Introduction to Flight Test Engineering [Introduction Aux Techniques Des Essais En Vol]

Flight test is at the core of what organizations must do in order to validate the operation and systems on an aircraft. While the AGARDograph series 300 and 160 series deal with aspects of this testing, this volume pulls it all together as an introduction to the process required to do effective flight test engineering. This volume was originally published in 1995. Its utility has been proven in that many flight test organizations and universities have requested copies for their engineers and students. It was felt that re-issuing it in a new format designed for electronic publication would be valuable to the community. This second printing changes none of the text, but rather reformats it. All the original references to AGARD (instead of RTO) are left in place so that none of the flavor of the original publication is lost. This is the Introductory Volume to the Flight Test Techniques Series. It is a general introduction to the various activities and aspects of Flight Test Engineering that must be considered when planning, conducting, and reporting a flight test program. Its main intent is to provide a broad overview to the novice engineer or to other people who have a need to interface with specialists within the flight test community. The first two Sections provide some insight into the question of why flight test and give a short history of flight test engineering. Sections 3 through 10 deal with the preparation for flight testing. They provide guidance on the preliminary factors that must be considered; the composition of the test team; the logistic support requirements; the instrumentation and data processing requirements; the flight test plan; the associated preliminary ground tests; and last, but by no means least, discuss safety aspects. Sections 11 through 27 describe the various types of flight tests that are usually conducted during the development and certification of a new or modified aircraft type. Each Section offers a brief introduction to the topic under consideration, and the nature and the objectives of the tests to be conducted. It lists the test instrumentation (and, where appropriate, other test equipment and facilities) required, describes the test maneuvers to be executed, and indicates the way in which the test data is selected, analyzed, and presented. The various activities that should take place between test flights are presented next. Items that are covered are: who to debrief; what type of reports to send where: types of data analysis required for next flight; review of test data to make a comparison to predicted data and some courses of action if there is not good agreement; and comments on selecting the next test flight. The activities that must take place upon completion of the test program are presented. The types of reports and briefings that should take place and a discussion of some of the uses of the flight test data are covered. A brief forecast is presented of where present trends may be leading.

Test facilities↗
NASA NTRS2017

Strain Monitoring of Flexible Structures

One of the biggest challenges facing NASA's deep space exploration goals is structural mass. A long duration transit vehicle on a journey to Mars, for example, requires a large internal volume for cargo, supplies and crew support. As with all space structures, a large pressure vessel is not enough. The vehicle also requires thermal, micro-meteoroid, and radiation protection, a navigation and control system, a propulsion system, and a power system, etc. As vehicles get larger, their associated systems also get larger and more complex. These vehicles require larger lift capacities and force the mission to become extremely costly. In order to build large volume habitable vehicles, with only minimal increases in launch volume and mass, NASA is developing lightweight structures. Lightweight structures are made from non-metallic materials including graphite composites and high strength fabrics and could provide similar or better structural capability than metals, but with significant launch volume and mass savings. Fabric structures specifically, have been worked by NASA off and on since its inception, but most notably in the 1990's with the TransHAB program. These TransHAB developed structures use a layered material approach to form a pressure vessel with integrated thermal and micro-meteoroid and orbital debris (MMOD) protection. The flexible fabrics allow the vessel to be packed in a small volume during launch and expand into a much larger volume once in orbit. NASA and Bigelow Aerospace recently installed the first human-rated inflatable module on the International Space Station (ISS), known as the Bigelow Expandable Activity Module (BEAM) in May of 2016. The module provides a similar internal volume to that of an Orbital ATK Cygnus cargo vehicle, but with a 77% launch volume savings. As lightweight structures are developed, testing methods are vital to understanding their behavior and validating analytical models. Common techniques can be applied to fabric materials, such as tensile testing, fatigue testing, and shear testing, but common measurement techniques cannot be used on fabric. Measuring strain in a material and during a test is a critical parameter for an engineer to monitor the structure during the test and correlate to an analytical model. The ability to measure strain in fabric structures is a challenge for NASA. Foil strain gauges, for example, are commonplace on metallic structures testing, but are extremely difficult to interface with a fabric substrate. New strain measuring techniques need to be developed for use with fabric structures. This paper investigates options for measuring strain in fabric structures for both ground testing and in-space structural health monitoring. It evaluates current commercially available options and outlines development work underway to build custom measurement solutions for NASA's fabric structures.

Litteken, Douglas A.↗
NASA NTRS1982

Strain rate characterization of unidirectional graphite/epoxy composite

For an investigation of problems of composites at high strain rates with dominant wave propagation effects, such as dynamically loaded composite jet engine blades, the longitudinal, transverse, and in-plane shear properties of unidirectional SP 288/AS graphite/epoxy were measured at various strain rates ranging from quasi-static to over 500/s. The test specimens were rings 10.16 cm in diameter, 2.54 cm long, 6 to 8 plies thick, and with fibers at 0, 90, and 10 deg off-axis. Quasi-static testing was conducted in a fixture which applies hydraulic pressure to the ring specimens, and dynamic testing was conducted by applying an internal pressure pulse through a liquid in a special fixture. Dynamic stress-strain curves are presented. For the 0-deg specimens, the modulus increases with strain up to 20 percent of the static value. The modulus and strength increase sharply in the 90-deg rings with strain rate reaching values two to three times the corresponding static rate.

Daniel, I. M.↗
NASA NTRS1984

High temperature static strain gage program

Development of electrical resistance strain gages for static strain measurements of nickel or cobalt superalloy parts inside a gas turbine engine on a test stand was inititated. Measurements of this type are of great importance because without reliable knowledge of the stresses and strains which exist in specific components, it will be difficult to fully appreciate where improvements in design and materials can be implemented. The first part of this effort consists of a strain gage alloy development program which will be followed by an investigation of complete strain gage systems. Efforts to date are summarized.

Hulse, C.↗
NASA NTRS1970

Strain gage installation manual

Detailed specifications for installing laboratory strain gages are compiled into handy reference manual that provides laboratory technicians with ready source of instructions on techniques and procedures for cementing a wide variety of strain gages onto most of the commonly encountered engineering materials.

Nichols, D. W.↗
NASA NTRS1979

Space applications of superconductivity - High field magnets

The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

Fickett, F. R.↗
NASA NTRS1986

Thermomechanical design criteria for ceramic-coated surfaces

Some early history of ceramic applications is presented. Finite element modeling of components to determine service and fabrication loads found inelastic behavior and residual stresses to be significant to component life. Inelastic behavior mitigates peak strains but enhances residual strains. Results of furnace, Mach 0.3 burner, and engine tests are discussed and categorized into design criteria (loading, geometry, fabrication, materials, analysis, and testing). These design rules and finite element analyses are brought to bear on two test cases: turboshaft engine seals, and rocket thrust chambers.

Mullen, R. L.↗