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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Nanomanipulation and Lithography for Carbon Nanotube Based Nondestructive Evaluation Sensor Development

Carbon nanotubes (CNTs) offer great potential for advanced sensor development due to the unique electronic transport properties of the material. However, a significant obstacle to the realization of practical CNT devices is the formation of reliable and reproducible CNT to metallic contacts. In this work, scanning probe techniques are explored for both fabrication of metallic junctions and positioning of singlewalled CNTs across these junctions. The use of a haptic force feedback interface to a scanning probe microscope is used to enable movement of nanotubes over micron length scales with nanometer precision. In this case, imaging of the surface is performed with light or intermittent contact to the surface. Increased tip-to-sample interaction forces are then applied to either create junctions or position CNTs. The effect of functionalization of substrate surfaces on the movement and tribology of the materials is also studied. The application of these techniques to the fabrication of CNT-based sensors for nondestructive evaluation applications is discussed.

Wincheski, Buzz↗
NASA NTRS2001

Rapid Prototyping Integrated With Nondestructive Evaluation and Finite Element Analysis

Most reverse engineering approaches involve imaging or digitizing an object then creating a computerized reconstruction that can be integrated, in three dimensions, into a particular design environment. Rapid prototyping (RP) refers to the practical ability to build high-quality physical prototypes directly from computer aided design (CAD) files. Using rapid prototyping, full-scale models or patterns can be built using a variety of materials in a fraction of the time required by more traditional prototyping techniques (refs. 1 and 2). Many software packages have been developed and are being designed to tackle the reverse engineering and rapid prototyping issues just mentioned. For example, image processing and three-dimensional reconstruction visualization software such as Velocity2 (ref. 3) are being used to carry out the construction process of three-dimensional volume models and the subsequent generation of a stereolithography file that is suitable for CAD applications. Producing three-dimensional models of objects from computed tomography (CT) scans is becoming a valuable nondestructive evaluation methodology (ref. 4). Real components can be rendered and subjected to temperature and stress tests using structural engineering software codes. For this to be achieved, accurate high-resolution images have to be obtained via CT scans and then processed, converted into a traditional file format, and translated into finite element models. Prototyping a three-dimensional volume of a composite structure by reading in a series of two-dimensional images generated via CT and by using and integrating commercial software (e.g. Velocity2, MSC/PATRAN (ref. 5), and Hypermesh (ref. 6)) is being applied successfully at the NASA Glenn Research Center. The building process from structural modeling to the analysis level is outlined in reference 7. Subsequently, a stress analysis of a composite cooling panel under combined thermomechanical loading conditions was performed to validate this process.

Abdul-Aziz, Ali↗
NASA NTRS2016

Ultrasonic Nondestructive Evaluation of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) During Large-Scale Load Testing and Rod Push-Out Testing

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is a structural concept developed by the Boeing Company to address the complex structural design aspects associated with a pressurized hybrid wing body (HWB) aircraft configuration. The HWB has long been a focus of NASA's environmentally responsible aviation (ERA) project, following a building block approach to structures development, culminating with the testing of a nearly full-scale multi-bay box (MBB), representing a segment of the pressurized, non-circular fuselage portion of the HWB. PRSEUS is an integral structural concept wherein skins, frames, stringers and tear straps made of variable number of layers of dry warp-knit carbon-fiber stacks are stitched together, then resin-infused and cured in an out-of-autoclave process. The PRSEUS concept has the potential for reducing the weight and cost and increasing the structural efficiency of transport aircraft structures. A key feature of PRSEUS is the damage-arresting nature of the stitches, which enables the use of fail-safe design principles. During the load testing of the MBB, ultrasonic nondestructive evaluation (NDE) was used to monitor several sites of intentional barely-visible impact damage (BVID) as well as to survey the areas surrounding the failure cracks after final loading to catastrophic failure. The damage-arresting ability of PRSEUS was confirmed by the results of NDE. In parallel with the large-scale structural testing of the MBB, mechanical tests were conducted of the PRSEUS rod-to-overwrap bonds, as measured by pushing the rod axially from a short length of stringer.

Johnston, Patrick H.↗
NASA NTRS2013

Application of Advanced Nondestructive Evaluation Techniques for Cylindrical Composite Test Samples

Two nondestructive methods were applied to composite cylinder samples pressurized to failure in order to determine manufacturing quality and monitor damage progression under load. A unique computed tomography (CT) image processing methodology developed at NASA Glenn Research was used to assess the condition of the as-received samples while acoustic emission (AE) monitoring was used to identify both the extent and location of damage within the samples up to failure. Results show the effectiveness of both of these methods in identifying potentially critical fabrication issues and their resulting impact on performance.

Martin, Richard E.↗
NASA NTRS2009

Capability Demonstrations for Penetrant Nondestructive Evaluation (NDE) of Metallic Tanks and Composite Overwrapped Pressure Vessel (COPV) Liners

As the desired crack detection size is decreased and approaches the physical limitations of liquid penetrant inspection techniques, the approach of performing a probability of detection (POD) validation test at a single aspect ratio, and then extending the results to other aspect ratios based on equivalent area predictions may not be valid. POD testing for penetrant inspection of metallic pressure vessels and COPV liners should be performed at the bounds of the required range of crack aspect ratios.

Metallic Tanks↗
NASA NTRS2021

Guidebook for Limited Sample Probability of Detection (LS-POD) Demonstration for Signal-Response Nondestructive Evaluation (NDE) Methods

This document provides guidance for performing limited sample probability of detection (LS-POD) demonstration testing with smaller numbers of flawed specimens than the 29 required for the Point Estimate POD method referenced in NASA Standard 5009B. This document is specifically applicable to NASA programs and projects where NASA Special NDE methods are used to inspect fracture critical human spaceflight metallic hardware when the minimum number of flawed specimens required for the Point Estimate POD method referenced in NASA Standard 5009B (2019) are not available.

Limited Sample Probability of Detection↗
NASA NTRSDate not supplied

Applications of Advanced Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM) Techniques to Address Safety of Flight Issues on NASA Spacecraft

Advanced NDE and SHM techniques are critical for ensuring the reliability and safety of NASA launch vehicles and spacecraft. NDE techniques such as infrared thermography, THz imaging, x-ray computed tomography and backscatter x-ray are used to detect indications of damage in spacecraft components and structures. Additionally, sensor and measurement systems are integrated into spacecraft to provide SHM to detect damaging events that occur during flight such as debris impacts during launch and assent or from micrometeoroid and orbital debris, or excessive loading due to anomalous flight conditions. A number of examples will be provided of how these NDE and SHM techniques have been applied to resolve safety critical inspection concerns for the Space Shuttle, International Space Station (ISS), and a variety of launch vehicles and unmanned spacecraft.

Advanced Nondestructive Evaluation (NDE)↗
NASA NTRS1998

Method Developed for the High-Temperature Nondestructive Evaluation of Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites

Ceramic matrix composites have emerged as candidate materials to allow higher operating temperatures (1000 to 1400 C) in gas turbine engines. A need, therefore, exists to develop nondestructive methods to evaluate material integrity at the material operating temperature by monitoring thermal and mechanical fatigue. These methods would also have potential as quality inspection tools. The goal of this investigation at the NASA Lewis Research Center is to survey and correlate the temperature-dependent damping and stiffness of advanced ceramic composite materials with imposed thermal and stress histories that simulate in-service turbine engine conditions. A typical sample size of 100 by 4 by 2 cubic millimeters, along with the specified stiffness and density, placed the fundamental vibration frequencies between 100 and 2000 Hz. A modified Forster apparatus seemed most applicable to simultaneously measure both damping and stiffness. Testing in vacuum reduced the effects of air on the measurements. In this method, a single composite sample is vibrated at its fundamental tone; then suddenly, the mechanical excitation is removed so that the sample's motion freely decays with time. Typical results are illlustrated in this paper.

Goldsby, Jon C.↗
NASA NTRS1971

A systems approach of the nondestructive evaluation techniques applied to Scout solid rocket motors.

Review and appraisal of the status of the nondestructive tests applied to Scout solid-propellant rocket motors, using analytical techniques to evaluate radiography for detecting internal discontinuities such as voids and unbonds. Information relating to selecting, performing, controlling, and evaluating the results of NDE tests was reduced to a common simplified format. With these data and the results of the analytical studies performed, it was possible to make the basic appraisals of the ability of a test to meet all pertinent acceptance criteria and, where necessary, provide suggestions to improve the situation.

Oaks, A. E.↗