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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Shear rupture of a directionally solidified eutectic gamma/gamma prime - alpha (Mo) alloy

Directionally solidified Mo alloys are evaluated to determine the shear rupture strength and to possibly improve it by microstructural and heat treatment variations. Bars of the alloy containing nominally 5.7% Al and 33.5% Mo by weight with balance Ni were directionally solidified at rates between 10 and 100 mm per hour in furnaces with thermal gradients at the liquid-solid interface of 250 or 100 C per cm. A limited number of longitudinal shear rupture tests were conducted at 760 C and 207 MPa in the as - solidified and in several heat treated conditions. It is shown that shear rupture failures are partly transgranular and that resistance to failure is prompted by good fiber alignment and a matrix structure consisting mainly of gamma prime. Well aligned as - solidified specimens sustained the shear stress for an average of 81 hours. A simulated coating heat treatment appeared to increase the transformation of gamma to gamma prime and raised the average shear life of aligned specimens to 111 hours. However, heat treatments at 1245 C and especially at 1190 C appeared to be detrimental by causing partial solutioning of the gamma prime, and reducing lives to 47 and 10 hours, respectively.

Harf, F. H.↗
NASA NTRS1982

Space Shuttle Wireless Crew Communications

The design, development, and performance characteristics of the Space Shuttle's Wireless Crew Communications System are discussed. This system allows Space Shuttle crews to interface with the onboard audio distribution system without the need for communications umbilicals, and has been designed through the adaptation of commercially available hardware in order to minimize development time. Testing aboard the Space Shuttle Orbiter Columbia has revealed no failures or design deficiencies.

Armstrong, R. W.↗
NASA NTRS1997

X-Ray Transmission Microscope Development

We have succeeded in meeting the goals set out in the proposal. A cadre of detector technologies is available to suit the requirements of the experiment. Resolutions of both real-time and absolute limits to resolution exceed the initial aspirations. Obtaining sufficient contrast is still a significant limitation but can be overcome by Judicious selection of the specimen composition. This can only take time and trial and error for a successful result. The 4th generation furnace provides the capability of real-time in-situ observations of composite alloy development. A low detection sensitivity however, has still made it difficult to observe dendritic growth, although it has been 'seen' in raw video; it was not a recordable signal. We have examined flight ampoules with XTM to observe particle and thermocouple placement, crucible flaws and cracks in collaboration with the Particle Pushing and Engulfment flight experiment (Dr. Stefanescu, UA, P.I.). The value of an in flight XTM to guard against experiment failure and safety assurance is obvious. Although not attributable to equipment limitations, a quest to observe particle pushing was not successful. We tried at length to prepare specimens that would demonstrate particle pushing. Instead, we were successful in imaging the interface deformation due to the thermal field distortion of a ceramic particle or void and to compare to calculated shapes. In theory, we should have been able to make major inroads to this field if the particles could be pushed and the velocities adjusted to make critical measurements. On the other hand, critical issues of sample preparation for the PEP flight experiment were established, particularly the clustering of particles and trapped voids. In this regard, the XTM did prove very useful so that flight specimens would work as expected and to perform post flight analysis. Although not a clear result, particle pushing of precipitates was observed in an Al-Si-Mn alloy. It may be that to be pushed, the particles need to be small and have clean surfaces like one might obtain from in-situ precipitation. The ability to image features in real time skill enable more fundamental and detailed understanding of solidification dynamics in microgravity than had previously been possible, thus, allowing the full benefits of microgravity experiments be applied towards rigorous testing of critical solidification models. The XTM is also a valuable tool for post solidification metallography. The 3-dimensional distribution of solute and solidification features within the specimen volume can be viewed without sectioning or other treatment when the solute has sufficiently higher atomic mass than the solvent. Thus the XTM could provide the first practical method for on orbit microstructural (metallographic) analysis by the astronauts or by telescience.

Kaukler, William F.↗
NASA NTRS2008

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However, adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for thermal barrier coatings (TBCs), culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Smialek, James L.↗
NASA NTRS2008

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for TBC s, culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Smialek, James L.↗
NASA NTRS2012

Autonomous Cryogenic Load Operations: KSC Autonomous Test Engineer

The KSC Autonomous Test Engineer (KATE) program has a long history at KSC. Now a part of the Autonomous Cryogenic Load Operations (ACLO) mission, this software system has been sporadically developed over the past 20+ years. Originally designed to provide health and status monitoring for a simple water-based fluid system, it was proven to be a capable autonomous test engineer for determining sources of failure in. the system, As part.of a new goal to provide this same anomaly-detection capability for a complicated cryogenic fluid system, software engineers, physicists, interns and KATE experts are working to upgrade the software capabilities and graphical user interface. Much progress was made during this effort to improve KATE. A display ofthe entire cryogenic system's graph, with nodes for components and edges for their connections, was added to the KATE software. A searching functionality was added to the new graph display, so that users could easily center their screen on specific components. The GUI was also modified so that it displayed information relevant to the new project goals. In addition, work began on adding new pneumatic and electronic subsystems into the KATE knowledgebase, so that it could provide health and status monitoring for those systems. Finally, many fixes for bugs, memory leaks, and memory errors were implemented and the system was moved into a state in which it could be presented to stakeholders. Overall, the KATE system was improved and necessary additional features were added so that a presentation of the program and its functionality in the next few months would be a success.

Shrading, Nicholas J.↗
NASA NTRS2014

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↗
DOE OSTI2016

Pellet Cladding Mechanical Interaction Modeling Using the Extended Finite Element Method

As a brittle material, the ceramic UO2 used as light water reactor fuel experiences significant fracturing throughout its life, beginning with the first rise to power of fresh fuel. This has multiple effects on the thermal and mechanical response of the fuel/cladding system. One such effect that is particularly important is that when there is mechanical contact between the fuel and cladding, cracks that extending from the outer surface of the fuel into the volume of the fuel cause elevated stresses in the adjacent cladding, which can potentially lead to cladding failure. Modeling the thermal and mechanical response of the cladding in the vicinity of these surface-breaking cracks in the fuel can provide important insights into this behavior to help avoid operating conditions that could lead to cladding failure. Such modeling has traditionally been done in the context of finite-element-based fuel performance analysis by modifying the fuel mesh to introduce discrete cracks. While this approach is effective in capturing the important behavior at the fuel/cladding interface, there are multiple drawbacks to explicitly incorporating the cracks in the finite element mesh. Because the cracks are incorporated in the original mesh, the mesh must be modified for cracks of specified location and depth, so it is difficult to account for crack propagation and the formation of new cracks at other locations. The extended finite element method (XFEM) has emerged in recent years as a powerful method to represent arbitrary, evolving, discrete discontinuities within the context of the finite element method. Development work is underway by the authors to implement XFEM in the BISON fuel performance code, and this capability has previously been demonstrated in simulations of fracture propagation in ceramic nuclear fuel. These preliminary demonstrations have included only the fuel, and excluded the cladding for simplicity. This paper presents initial results of efforts to apply XFEM to model stress concentrations induced by fuel fractures at the fuel/cladding interface during pellet cladding mechanical interaction (PCMI). This is accomplished by enhancing the thermal and mechanical contact enforcement algorithms employed by BISON to permit their use in conjunction with XFEM. The results from this methodology are demonstrated to be equivalent to those from using meshed discrete cracks. While the results of the two methods are equivalent for the case of a stationary crack, it is demonstrated that XFEM provides the additional flexibility of allowing arbitrary crack initiation and propagation during the analysis, and minimizes model setup effort for cases with stationary cracks.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Resilience Design Patterns - A Structured Approach to Resilience at Extreme Scale (version 1.1)

Reliability is a serious concern for future extreme-scale high-performance computing (HPC) systems. Projections based on the current generation of HPC systems and technology roadmaps suggest the prevalence of very high fault rates in future systems. The errors resulting from these faults will propagate and generate various kinds of failures, which may result in outcomes ranging from result corruptions to catastrophic application crashes. Therefore the resilience challenge for extreme-scale HPC systems requires management of various hardware and software technologies that are capable of handling a broad set of fault models at accelerated fault rates. Also, due to practical limits on power consumption in HPC systems future systems are likely to embrace innovative architectures, increasing the levels of hardware and software complexities. As a result the techniques that seek to improve resilience must navigate the complex trade-off space between resilience and the overheads to power consumption and performance. While the HPC community has developed various resilience solutions, application-level techniques as well as system-based solutions, the solution space of HPC resilience techniques remains fragmented. There are no formal methods and metrics to investigate and evaluate resilience holistically in HPC systems that consider impact scope, handling coverage, and performance & power efficiency across the system stack. Additionally, few of the current approaches are portable to newer architectures and software environments that will be deployed on future systems. In this document, we develop a structured approach to the management of HPC resilience using the concept of resilience-based design patterns. A design pattern is a general repeatable solution to a commonly occurring problem. We identify the commonly occurring problems and solutions used to deal with faults, errors and failures in HPC systems. Each established solution is described in the form of a pattern that addresses concrete problems in the design of resilient systems. The complete catalog of resilience design patterns provides designers with reusable design elements. We also define a framework that enhances a designer's understanding of the important constraints and opportunities for the design patterns to be implemented and deployed at various layers of the system stack. This design framework may be used to establish mechanisms and interfaces to coordinate flexible fault management across hardware and software components. The framework also supports optimization of the cost-benefit trade-offs among performance, resilience, and power consumption. The overall goal of this work is to enable a systematic methodology for the design and evaluation of resilience technologies in extreme-scale HPC systems that keep scientific applications running to a correct solution in a timely and cost-efficient manner in spite of frequent faults, errors, and failures of various types.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

The Roles of Interface, Adherend, and Adhesive in Plasma- and Other-treated Joints of Metals and FRP Materials Under Shear Deformation

This work investigated the role of interface, adherend, and adhesive in adhesively-bonded metal-metal, metal-CFRTP, and CFRTP-CFRTP combinations with plasma-treated surfaces under shear deformation. To this end, aluminum alloys (AA5052 and AA6061) and short-carbon-fiber-reinforced polyamide 66 (CFRPA66) were used as examples and performed through single lap shear testing. The results showed that air plasma surface treatment can improve the shear behavior of adhesively-bonded AA5052-CFRPA66 and CFRPA66-CFRPA66 joints with about 20% enhanced lap shear strength compared to non-treated cases. Failure surface morphology of plasma-treated CFRPA66 adherend confirmed this improvement by showing an increased amount of adhesive failure than interfacial failure between CFRPA66 and adhesive. But this is not true for AA5052-AA6061 joints with plasma-treated surfaces exhibiting almost no enhanced lap shear strength. This study also showed the importance of selecting a proper surface modification method for the enhancement of adhesive-bonded structures under shear deformation through the analysis of the results in this study and in the literature. For fiber-reinforced polymers (FRPs), improving FRP/adhesive interface may be prioritized via different surface modification methods (e.g., plasma, chemical coating, etc.) than adhesive modification methods. However, for surface-cleaned metals, toughening adhesive via different enhancement methods (e.g., nano-particles, chemical enhancement, etc.) may be more important than improving metal/adhesive interface. These insightful results are valuable in the area of multi-materials joining.

Qiao, Yao↗
DOE OSTI2020

Numerical Simulation and Experimental Validation of Joint Performance in Aluminum-Steel Lap Welds Formed by Friction Stir Dovetailing

Friction stir dovetailing (FSD) is a new dissimilar material joining process that simultaneously forms a mechanical interlock and metallurgical bond at the dissimilar material interface. This work presents development of a modeling and simulation approach to predict mechanical performance of FSD thick section aluminum to steel joints. A finite element analysis (FEA) was carried out in order to predict the load-carrying capacity and failure location for aluminum thicknesses between 12.7 mm and 50.8 mm with different numbers of dovetails. The numerical results and corresponding experimental investigation are in agreement and suggest that the developed methods can be used effectively for design and analysis of FSD joints using standard FEA tools.

Friction stir dovetailing, Friction stir welding, ↗
DOE OSTI2021

Mitigating ion migration in perovskite solar cells

The intrinsic ion migration in the metal halide perovskite absorber layer and its interfaces seriously limits the device stability of perovskite solar cells (PSCs). Despite considerable efforts to mitigate the ion migration issue, it remains a formidable challenge in the commercialization of PSCs. In this paper, we provide a short review of the device failure mechanisms induced by intrinsic ion migration and discuss the detrimental effects of ion migration on different component layers of PSCs. We outline the corresponding strategies to mitigate ion migration in PSCs and provide an insight on materials engineering to attain long-term stabilized perovskite photovoltaics.

14 SOLAR ENERGY↗
DOE OSTI2024

Statistical characterization of high voltage vacuum surface flashover with gapped and ungapped anodes

This manuscript reports the experimental study of a novel vacuum high-voltage (HV) feedthrough geometry with a recessed anode triple junction (ATJ) relevant to large-scale pulsed power systems. It is shown experimentally that introducing a vacuum gap between the insulator–anode interface and recessing the ATJ farther away from the cathode triple junction significantly enhances high voltage (HV) vacuum surface flashover hold-off. The results for “first pulse” and “consecutive pulse” tests are reported. The physical mechanisms contributing to the electrical failure of this feedthrough geometry appear to be unique to this geometry. These findings show the potential to allow for HV vacuum surface flashover geometries with significantly improved electrical characteristics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1989

Ultrasonic study of adhesive bond quality at a steel-to-rubber interface by using quadrature phase detection techniques

The quadrature phase detection technique was used to simultaneously monitor the phase and amplitude of a toneburst signal normally reflected from an adhesively bonded steel-to-rubber interface. The measured phase was found to show a positive shift for all bonded samples with respect to the disbonded state - the phase shift being larger for samples with weaker bonds, as manifested by smaller values of applied tensile loads at failure. A model calculation, which incorporates the concept of interfacial strength into the usual problem of wave propagation in multilayered media, was used to deduce a bond-quality parameter from an experimentally measured phase shift. This bond-quality parameter was found to be correlated with the tensile strength of the adhesive bonds at failure loads.

Smith, A. C.↗
NASA NTRS1993

Lunar surface operations. Volume 3: Robotic arm for lunar surface vehicle

A robotic arm for a lunar surface vehicle that can help in handling cargo and equipment, and remove obstacles from the path of the vehicle is defined as a support to NASA's intention to establish a lunar based colony by the year 2010. Its mission would include, but not limited to the following: exploration, lunar sampling, replace and remove equipment, and setup equipment (e.g. microwave repeater stations). Performance objectives for the robotic arm include a reach of 3 m, accuracy of 1 cm, arm mass of 100 kg, and lifting capability of 50 kg. The end effectors must grip various sizes and shapes of cargo; push, pull, turn, lift, or lower various types of equipment; and clear a path on the lunar surface by shoveling, sweeping aside, or gripping the obstacle present in the desired path. The arm can safely complete a task within a reasonable amount of time; the actual time is dependent upon the task to be performed. The positioning of the arm includes a manual backup system such that the arm can be safely stored in case of failure. Remote viewing and proximity and positioning sensors are incorporated in the design of the arm. The following specific topic are addressed in this report: mission and requirements, system design and integration, mechanical structure, modified wrist, structure-to-end-effector interface, end-effectors, and system controls.

Shields, William↗
NASA NTRS2013

Autonomous Cryogenic Load Operations: Knowledge-Based Autonomous Test Engineer

The Knowledge-Based Autonomous Test Engineer (KATE) program has a long history at KSC. Now a part of the Autonomous Cryogenic Load Operations (ACLO) mission, this software system has been sporadically developed over the past 20 years. Originally designed to provide health and status monitoring for a simple water-based fluid system, it was proven to be a capable autonomous test engineer for determining sources of failure in the system. As part of a new goal to provide this same anomaly-detection capability for a complicated cryogenic fluid system, software engineers, physicists, interns and KATE experts are working to upgrade the software capabilities and graphical user interface. Much progress was made during this effort to improve KATE. A display of the entire cryogenic system's graph, with nodes for components and edges for their connections, was added to the KATE software. A searching functionality was added to the new graph display, so that users could easily center their screen on specific components. The GUI was also modified so that it displayed information relevant to the new project goals. In addition, work began on adding new pneumatic and electronic subsystems into the KATE knowledge base, so that it could provide health and status monitoring for those systems. Finally, many fixes for bugs, memory leaks, and memory errors were implemented and the system was moved into a state in which it could be presented to stakeholders. Overall, the KATE system was improved and necessary additional features were added so that a presentation of the program and its functionality in the next few months would be a success.

Schrading, J. Nicolas↗
DOE OSTI2020

High Efficiency Silicon Module Degradation - From Atoms to Systems: Preprint

For PV to be cost competitive with traditional energy sources reliability is of critical importance. Historically, PV reliability has focused on the module packaging because degradation and failure modes were directly linked to the packaging. Today, in addition to module packaging cell related reliability issues can be observed. We show that silicon heterojunction (SHJ) degradation is directly linked to the re-distribution of hydrogen (H) near the interface between the amorphous-silicon (a-Si) and silicon bulk. PERC modules show a similar decline in carrier lifetime indicating that not the packaging but the cells are also changing during field exposure. Examination of a stressed PERC cell showed a similar H redistribution in the cell. Understanding the degradation mechanism at the atomic level is important in facilitating possible mitigating mechanisms and more accurately projecting performance.

degradation↗
NASA NTRS1987

Theoretical considerations in designing operator interfaces for automated systems

The domains most amenable to techniques based on artificial intelligence (AI) are those that are systematic or for which a systematic domain can be generated. In aerospace systems, many operational tasks are systematic owing to the highly procedural nature of the applications. However, aerospace applications can also be nonprocedural, particularly in the event of a failure or an unexpected event. Several techniques are discussed for designing automated systems for real-time, dynamic environments, particularly when a 'breakdown' occurs. A breakdown is defined as operation of an automated system outside its predetermined, conceptual domain.

Norman, Susan D.↗