Environmental Loss Characterization of an Advanced Stirling Convertor (ASC-E2) Insulation Package Using a Mock Heater
Test hardware used as pathfinder for Thermal Standard test materials and methods
Schifer, Nicholas A.↗
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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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A study of degradation of plates for nickel-cadmium spacecraft cells
The relative merits of coining and not coining of sintered nickel oxide and cadmium plates was investigated. Sample plate materials from most commercial cell suppliers were obtained and characterized for properties that may correlate with the tendency toward physical disintegration during handling and over long periods of time in the cell. Special test methods were developed to obtain comparative data in a short time. A wide range of physical properties and coining thickness was observed, resulting in a range of responses. The stronger materials resisted loss of sinter better than weaker materials whether or not coined. Coining improved handling and resistance to electrochemical cycling of weaker materials. The mechanism of break-down of positive plate edges under cycling appears to be the same as that of thickening and blistering. Brittle, nonadherent sinter, resulting from certain impregnation processes, is the most vulnerable to degradation. It is concluded that the latter type of materials should be coined, but coining of strong materials is optional.
Scott, W. R.↗
A study of degradation of plates for nickel-cadmium spacecraft cells
The relative merits of coining and not coining of sintered nickel-oxide and cadmium plates was investigated. A survey of the industry including cell manufactures and users was made and results summarized. Sample plate materials from most commercial cell suppliers were obtained and characterized for properties that may correlate with the tendency toward physical disintegration during handling and over long periods of time in the cell. Special test methods were developed to obtain comparative data in a short time. A wide range of physical properties and coining thicknesses was observed, resulting in a range of responses. The stronger, less brittle materials resisted loss of sinter better than weaker materials whether or not coined. Coining improved handling and resistance to electrochemical cycling in all materials tested. An apparent exception was found to be due to improper coining of a tapered edge.
Scott, W. R.↗
The mechanics of delamination in fiber-reinforced composite materials. Part 2: Delamination behavior and fracture mechanics parameters
Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extenstion. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined.
Wang, S. S.↗
The mechanics of delamination in fiber-reinforced composite materials. II - The delamination behavior and fracture mechanics parameters
Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extension. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined. Previously announced in STAR as N84-13222
Wang, S. S.↗
Mode I Cohesive Law Characterization of Through-Crack Propagation in a Multidirectional Laminate
A method is proposed and assessed for the experimental characterization of through-the-thickness crack propagation in multidirectional composite laminates with a cohesive law. The fracture toughness and crack opening displacement are measured and used to determine a cohesive law. Two methods of computing fracture toughness are assessed and compared. While previously proposed cohesive characterizations based on the R-curve exhibit size effects, the proposed approach results in a cohesive law that is a material property. The compact tension specimen configuration is used to propagate damage while load and full-field displacements are recorded. These measurements are used to compute the fracture toughness and crack opening displacement from which the cohesive law is characterized. The experimental results show that a steady-state fracture toughness is not reached. However, the proposed method extrapolates to steady-state and is demonstrated capable of predicting the structural behavior of geometrically-scaled specimens.
Bergan, Andrew C.↗
Technical evaluation report of the Specialists Meeting on Characterization of Low Cycle High Temperature Fatigue by the Strainrange Partitioning Method
The ability of the Strainrange Partitioning Method SRP was evaluated to correlate the creep-fatigue behavior of gas turbine materials and to predict the creep fatigue life of laboratory specimens subjected to complex cycling conditions. A reference body of high temperature creep fatigue data which can be used in the evaluation of other SRP and low cycle high temperature fatigue predictive techniques was provided.
Drapier, J. M.↗
Importance and Definition of Materials in Tribology. Status of Understanding
In general, tribological systems consist of three basic components: the material surfaces in contact, the lubricant, and the environment. The materials in contact and the influence of both bulk and surface properties, indicating the importance of material characterization, on tribological behavior are addressed. Since metals and metallic alloys are the most widely used class of materials in practical devices, attention is focused principally on them. With respect to surface behavior, the effect of contaminants both from within the material and from the environment on adhesive behavior is addressed. The various surface events that alter adhesion, friction, and wear are discussed. These include surface reconstruction, segregation, chemisorption, and compound formation. Examples of these events are presented. Minor nuances in the structure of the outermost layers of solids have a pronounced effect on tribological properties. The importance of characterizing the materials of solids in contact in order to achieve a fundamental understanding of adhesion, friction, and wear and accordingly of methods for their control are addressed.
Buckley, D. H.↗
Thermoviscoplastic response of thin plates subjected to intense local heating
A finite element method is employed to investigate the thermoviscoplastic response of a half-cylinder to intense localized transient heating. Thermoviscoplastic material behavior is characterized by the Bodner-Partom constitutive model. Structure geometry is modeled with a three-dimensional assembly of CST-DKT plate elements incorporating the large deflection von Karman assumptions. The paper compares the results of a dynamic analysis with a quasi-static analysis for the half-cylinder structure with a step-function transient temperature loading similar to that which may be encountered with shock wave interference on a hypersonic leading edge.
Byrom, Ted G.↗
Some Challenges in the Design of Human-Automation Interaction for Safety-Critical Systems
Increasing amounts of automation are being introduced to safety-critical domains. While the introduction of automation has led to an overall increase in reliability and improved safety, it has also introduced a class of failure modes, and new challenges in risk assessment for the new systems, particularly in the assessment of rare events resulting from complex inter-related factors. Designing successful human-automation systems is challenging, and the challenges go beyond good interface development (e.g., Roth, Malin, & Schreckenghost 1997; Christoffersen & Woods, 2002). Human-automation design is particularly challenging when the underlying automation technology generates behavior that is difficult for the user to anticipate or understand. These challenges have been recognized in several safety-critical domains, and have resulted in increased efforts to develop training, procedures, regulations and guidance material (CAST, 2008, IAEA, 2001, FAA, 2013, ICAO, 2012). This paper points to the continuing need for new methods to describe and characterize the operational environment within which new automation concepts are being presented. We will describe challenges to the successful development and evaluation of human-automation systems in safety-critical domains, and describe some approaches that could be used to address these challenges. We will draw from experience with the aviation, spaceflight and nuclear power domains.
systems engineering↗
Particulate Filtration from Emissions of a Plasma Pyrolysis Assembly Reactor Using Regenerable Porous Metal Filters
Microwave-based plasma pyrolysis technology is being studied as a means of supporting oxygen recovery in future spacecraft life support systems. The process involves the conversion of methane produced from a Sabatier reactor to acetylene and hydrogen, with a small amount of solid carbon particulates generated as a side product. The particles must be filtered before the acetylene is removed and the hydrogen-rich gas stream is recycled back to the CRA. We discuss developmental work on porous metal media filters for removing the carbon particulate emissions from the PPA exit gas stream and to provide in situ media regeneration capability. Because of the high temperatures involved in oxidizing the deposited carbon during regeneration, there was particular focus in this development on the materials that could be used, the housing design, and heating methods. This paper describes the design and operation of the filter and characterizes their performance from integrated testing at the Environmental Chamber (E-Chamber) at MSFC.
Agui, Juan H.↗
Chemical and spectroscopic characterization of a suite of Mars soil analogs
The National Aeronautics and Space Administration has begun preparations for the flight of the Mars Observer Mission in the early 1990s. An advanced ground-based study is being conducted on a usefully limited suite of Mars Soil Analog Materials (MarSAM) intended to simulate the aeolian material covering the surface of Mars. A series of variably proportioned iron/calcium smectite clays were prepared from a typical montmorillonite clay using the Banin method. The effect of increasing iron on a diverse set of chemical and spectroscopic properties of the suite of clays is discussed. In order to chemically characterize the MarSAM and compare them with the Martian soil studied by Viking, the clays were analyzed for their major and minor elemental compositions by X-ray fluorescence and ion-coupled plasma techniques. It was concluded that the surface iron has a complex and hitherto uninvestigated impact on the catalytic and spectroscopic properties of clays and on the ability of these material to store energy.
Coyne, L. M.↗
Testing the Predictive Capability of the High-Fidelity Generalized Method of Cells Using an Efficient Reformulation
The High-Fidelity Generalized Method of Cells is a new micromechanics model for unidirectionally reinforced periodic multiphase materials that was developed to overcome the original model's shortcomings. The high-fidelity version predicts the local stress and strain fields with dramatically greater accuracy relative to the original model through the use of a better displacement field representation. Herein, we test the high-fidelity model's predictive capability in estimating the elastic moduli of periodic composites characterized by repeating unit cells obtained by rotation of an infinite square fiber array through an angle about the fiber axis. Such repeating unit cells may contain a few or many fibers, depending on the rotation angle. In order to analyze such multi-inclusion repeating unit cells efficiently, the high-fidelity micromechanics model's framework is reformulated using the local/global stiffness matrix approach. The excellent agreement with the corresponding results obtained from the standard transformation equations confirms the new model's predictive capability for periodic composites characterized by multi-inclusion repeating unit cells lacking planes of material symmetry. Comparison of the effective moduli and local stress fields with the corresponding results obtained from the original Generalized Method of Cells dramatically highlights the original model's shortcomings for certain classes of unidirectional composites.
Arnold, Steven M.↗
Variable Pressure - Scanning Electron Microscopy (VP-SEM)
Variable Pressure (or Environmental) Scanning Electron Microscopy (VP-SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples. Terrestrially, VP-SEM is extensively used to non-destructively study geologic and manufactured materials with high spatial resolution (tens of nanometers) and large depth-of-field. An SEM offers a geologist a first survey of microscopic mineral phases via secondary electron imaging (SEI), which provides a topographic look at a sample, as well as backscattered electron (BEI) imaging, which contrasts the phases present based on their geochemistry (atomic number). A VP-SEM utilizes a gas in the sample chamber as a charge dissipation and signal amplification method, allowing analysis of a sample without preparation in the form of a conductive coating. A miniaturized VP-SEM operating in-situ on a lander or rover would be able to use the CO2-rich Martian atmosphere (e.g., Nier et al., 1976; Williams 2016) as an imaging medium for this purpose. Adaptation of a VP-SEM for in-situ Mars surface studies will provide a new imaging capability (via SEI) that is at least an order of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (Williams et al., 2015), and equal to or better than the achieved resolution of the Atomic Force Microscope on the Phoenix Mars lander (Pike et al., 2011). In addition, the MVP-SEM is capable of BSI and simultaneous chemical analysis of the imaged region. In this sense, the MVP-SEM can be regarded as an instrument suite that will provide a new set of information not achievable by any other instrument. The Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) was designed, built, and benchtop tested by a team at NASA’s Marshall Space Flight Center and Jet Propulsion Laboratory (JPL), Jacobs Space Exploration Group, Applied Physics Technologies, Inc. (AP-Tech), and Creare LLC, working with a team of technical and science collaborators. Benchtop testing was successful, proving concept feasibility. To date, the MVP-SEM has achieved an imaging resolution of <100 nm in the lab, and with continued optimization, even better performance (~50 nm resolution) is possible. Use in-situ on the lunar or other planetary surfaces would require some redesign to optimize instrument performance, but such an instrument would be equally useful.
Variable Pressure Scanning Electron Microscopy↗
Miniature Variable Pressure - Scanning Electron Microscopy (MVP-SEM)
Variable Pressure (or Environmental) Scanning Electron Microscopy (VP-SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples. Terrestrially, VP-SEM is extensively used to non-destructively study geologic and manufactured materials with high spatial resolution (tens of nanometers) and large depth-of-field. An SEM offers a geologist a first survey of microscopic mineral phases via secondary electron imaging (SEI), which provides a topographic look at a sample, as well as backscattered electron (BEI) imaging, which contrasts the phases present based on their geochemistry (atomic number). A VP-SEM utilizes a gas in the sample chamber as a charge dissipation and signal amplification method, allowing analysis of a sample without preparation in the form of a conductive coating. A miniaturized VP-SEM operating in-situ on a lander or rover would be able to use the CO2-rich Martian atmosphere (e.g., Nier et al., 1976; Williams 2016) as an imaging medium for this purpose. Adaptation of a VP-SEM for in-situ Mars surface studies will provide a new imaging capability (via SEI) that is at least an order of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (Williams et al., 2015), and equal to or better than the achieved resolution of the Atomic Force Microscope on the Phoenix Mars lander (Pike et al., 2011). In addition, the MVP-SEM is capable of BSI and simultaneous chemical analysis of the imaged region. In this sense, the MVP-SEM can be regarded as an instrument suite that will provide a new set of information not achievable by any other instrument. The Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) was designed, built, and benchtop tested by a team at NASA’s Marshall Space Flight Center and Jet Propulsion Laboratory (JPL), Jacobs Space Exploration Group, Applied Physics Technologies, Inc. (AP-Tech), and Creare LLC, working with a team of technical and science collaborators. Benchtop testing was successful, proving concept feasibility. To date, the MVP-SEM has achieved an imaging resolution of <100 nm in the lab, and with continued optimization, even better performance (~50 nm resolution) is possible. Use in-situ on the lunar or other planetary surfaces would require some redesign to optimize instrument performance, but such an instrument would be equally useful.
Variable Pressure Scanning Electron Microscopy↗
Probabilistic high cycle fatigue failure analysis with application to liquid propellant rocket engines
A probabilistic high cycle fatigue (HCF) failure analysis of a welded duct in a rocket engine of the Space Shuttle main engine class is described. A state-of-the-art HCF failure prediction method was used in a Monte Carlo simulation to generate a distribution of failure lives. A stochastic stress/life model is used for material characterization, and a composite stress history is generated for accurately deriving the stress cycles for the fatigue-damage calculations. The HCF failure model expresses fatigue life as a function of stochastic parameters including environment, loads, material properties, geometry, and model specification errors. A series of HCF failure life analyses were performed to study the impact of a fixed parameter and to assess the importance of each stochastic input parameter through marginal analyses.
Sutharshana, S.↗
Metallurgical coatings and thin films; Proceedings of the International Conference, 18th, San Diego, CA, Apr. 22-26, 1991. Vols. 1 & 2
A conference on metallurgical coatings and thin films produced papers in the areas of coatings for use at high temperatures; hard coatings and deposition technologies; diamonds and related materials; tribological coatings/surface modifications; thin films for microelectronics and high temperature superconductors; optical coatings, film characterization, magneto-optics, and guided waves; and methods for characterizing films and modified surfaces.
Mcguire, Gary E.↗
NASA's Ground-Based Observing Campaigns of Rocket Bodies with the UKIRT and NASA ES-MCAT Telescopes
Rocket bodies comprise a class of human-made space debris that are at the same time essential for launching every spacecraft from the Earth, but are also a significant source of debris both as intact objects, as well as fragmented debris. Unspent fuel has been long theorized as a potential cause of catastrophic rocket body break-ups. Given typical orbital speeds range from approximately 2-3 kilometers per second at Geosynchronous Orbit (GEO) and up to 15 kilometers per second in low Earth orbit (LEO), collisions with uncatalogued and undetected debris can also cause catastrophic breakups. Understanding break-ups is a necessary step in preventing them, and one key step in that process is to correlate and characterize daughter fragments with their parent bodies. Two very different methods include (1) conducting photometric surveys to correlate an object's motion and orbital elements to the parent body, and (2) characterizing what materials comprise the target to determine whether those materials are consistent with the parent body or like objects. With this in mind, photometric data were taken shortly after the breakup of one rocket body for short-term orbital studies, and a suite of spectral data were taken of rocket bodies that are fully intact to compare with debris, for characterization studies. Targets included Titan Transtage, Briz-M, and Ariane rocket bodies and debris. Spectra of each sub-class of rocket body were very similar within their rocket body type, but differed distinctly from one type to the next, supporting the effectiveness of this approach.
Lederer, Susan M.↗