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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

A study of the stress wave factor technique for nondestructive evaluation of composite materials

The acousto-ultrasonic method of nondestructive evaluation is an extremely sensitive means of assessing material response. Efforts continue to complete the understanding of this method. In order to achieve the full sensitivity of the technique, extreme care must be taken in its performance. This report provides an update of the efforts to advance the understanding of this method and to increase its application to the nondestructive evaluation of composite materials. Included are descriptions of a novel optical system that is capable of measuring in-plane and out-of-plane displacements, an IBM PC-based data acquisition system, an extensive data analysis software package, the azimuthal variation of acousto-ultrasonic behavior in graphite/epoxy laminates, and preliminary examination of processing variation in graphite-aluminum tubes.

Sarrafzadeh-Khoee, A.↗
NASA NTRS1988

Nondestructive evaluation by acousto-ultrasonics

Acousto-ultrasonics is an ultrasonic technique that was originally devised to cope with the particular problems associated with nondestructive evaluation (NDE) of fiber/polymer composite structures. The fiber/polymer composites are more attenuating to ultrasound than any other material presently of interest. This limits the applicability of high-frequency ultrasonics. A common use of ultrasound is the imaging of flaws internal to a structure by scattering from the interface with the flaw. However, structural features of composites can scatter ultrasound internally, thus obscuring the flaws. A need relative to composites is to be able to nondestructively measure the strength of laminar boundaries in order to assess the integrity of a structure. Acousto-ultrasonics has exhibited the ability to use the internal scattering to provide information for determining the strength of laminar boundaries. Analysis of acousto-ultrasonic signals by the wave ray paths that compose it leads to waveform partitioning that enhances the sensitivity to mechanical strength parameters.

Kautz, Harold E.↗
NASA NTRS2000

A Bridge Health Monitoring Method Using the Hilbert-Huang Transform: A Case Study

We have developed a new method for nondestructive instrument method to monitor the health of a bridge. This new method is based on a transient test load and simple data collection. The nuclear of the method is the new invented nonstationary and nonlinear time series analysis method, the Empirical Mode Decomposition and Hilbert Spectral Analysis. The final decision on the health of the bridge structure is based on the nonlinear characteristic of the data, and on the comparison between the free and the forced vibration frequencies. Thus this alternative method enjoys many advantages: (1) no a priori data required, (2) simple data collection, and (3) minimum traffic disruption. Results from a case study of the Shing-Nan Bridge in Hou-Wei will be reported.

Huang, Norden E.↗
NASA NTRS2011

Seeding Cracks Using a Fatigue Tester for Accelerated Gear Tooth Breaking

This report describes fatigue-induced seeded cracks in spur gears and compares them to cracks created using a more traditional seeding method, notching. Finite element analysis (FEA) compares the effective compliance of a cracked tooth to the effective compliance of a notched tooth where the crack and the notch are of the same depth. In this analysis, cracks are propagated to the desired depth using FRANC2D and effective compliances are computed in ANSYS. A compliance-based feature for detecting cracks on the fatigue tester is described. The initiated cracks are examined using both nondestructive and destructive methods. The destructive examination reveals variability in the shape of crack surfaces.

Nenadic, Nenad G.↗
NASA NTRS2017

A Novel UAV Electric Propulsion Testbed for Diagnostics and Prognostics

This paper presents a novel hardware-in-the-loop (HIL) testbed for systems level diagnostics and prognostics of an electric propulsion system used in UAVs (unmanned aerial vehicle). Referencing the all electric, Edge 540T aircraft used in science and research by NASA Langley Flight Research Center, the HIL testbed includes an identical propulsion system, consisting of motors, speed controllers and batteries. Isolated under a controlled laboratory environment, the propulsion system has been instrumented for advanced diagnostics and prognostics. To produce flight like loading on the system a slave motor is coupled to the motor under test (MUT) and provides variable mechanical resistance, and the capability of introducing nondestructive mechanical wear-like frictional loads on the system. This testbed enables the verification of mathematical models of each component of the propulsion system, the repeatable generation of flight-like loads on the system for fault analysis, test-to-failure scenarios, and the development of advanced system level diagnostics and prognostics methods. The capabilities of the testbed are extended through the integration of a LabVIEW-based client for the Live Virtual Constructive Distributed Environment (LVCDC) Gateway which enables both the publishing of generated data for remotely located observers and prognosers and the synchronization the testbed propulsion system with vehicles in the air. The developed HIL testbed gives researchers easy access to a scientifically relevant portion of the aircraft without the overhead and dangers encountered during actual flight.

Gorospe, George E., Jr.↗
NASA NTRS2005

Rotordynamic Analysis and Feasibility Study of a Disk Spin Test Facility for Rotor Health Monitoring

Recently, National Aeronautics and Space Administration (NASA) initiated a program to achieve the significant improvement in aviation safety. One of the technical challenges is the design and development of accelerated experiments that mimic critical damage cases encountered in engine components. The Nondestructive Evaluation (NDE) Group at the NASA Glenn Research Center (GRC) is currently addressing the goal concerning propulsion health management and the development of propulsion system specific technologies intended to detect potential failures prior to catastrophe. For this goal the unique disk spin simulation system was assembled at NASA GRC, which allows testing of rotors with the spinning speeds up to 10K RPM, and at the elevated temperature environment reaching 540 C (1000 F). It is anticipated that the facility can be employed for detection of Low Cycle Fatigue disk cracking and further High Cycle Fatigue blade vibration. The controlled crack growth studies at room and elevated temperatures can be conducted on the turbine wheels, and various NDE techniques can be integrated and assessed as in-situ damage monitoring tools. Critical rotating parts in advanced gas turbine engines such as turbine disks frequently operate at high temperature and stress for long periods of time. The integrity of these parts must be proven by non-destructive evaluation (NDE) during various machining steps ranging from forging blank to finished shape, and also during the systematic overhaul inspections. Conventional NDE methods, however, have unacceptable limits. Some of these techniques are time-consuming and inconvenient for service aircraft testing. Almost all of these techniques require that the vicinity of the damage is known in advance. These experimental techniques can provide only local information and no indication of the structural strength at a component and/or system level. The shortcomings of currently available NDE methods lead to the requirement of new damage detection techniques that can provide global information on the rotating components/system, and, in addition, they do not require direct human access to the operating system. During this period of research considerable effort was directed towards the further development of experimental facility and development of the vibration-based crack detection methodology for rotating disks and shafts. A collection of papers and reports were written to describe the results of this work. The attached captures that effort and represents the research output during the grant period.

Sawicki, Jerzy T.↗
NASA NTRS2005

Infrared On-Orbit Inspection of Shuttle Orbiter Reinforced Carbon-Carbon Using Solar Heating

Thermographic nondestructive inspection techniques have been shown to provide quantitative, large area damage detection capabilities for the ground inspection of the reinforced carbon-carbon (RCC) used for the wing leading edge of the Shuttle orbiter. The method is non-contacting and able to inspect large areas in a relatively short inspection time. Thermal nondestructive evaluation (NDE) inspections have been shown to be applicable for several applications to the Shuttle in preparation for return to flight, including for inspection of RCC panels during impact testing, and for between-flight orbiter inspections. The focus of this work is to expand the capabilities of the thermal NDE methodology to enable inspection by an astronaut during orbital conditions. The significant limitations of available resources, such as weight and power, and the impact of these limitations on the inspection technique are discussed, as well as the resultant impact on data analysis and processing algorithms. Of particular interest is the impact to the inspection technique resulting from the use of solar energy as a heat source, the effect on the measurements due to working in the vacuum of space, and the effect of changes in boundary conditions, such as radiation losses seen by the material, on the response of the RCC. The resultant effects on detectability limits are discussed. Keywords: Nondestructive Evaluation, Shuttle, on-orbit inspection, thermography, infrared

Howell, P. A.↗
NASA NTRS2001

Use of Computed Tomography for Characterizing Materials Grown Terrestrially and in Microgravity

The purpose behind this work is to provide NASA Principal Investigators (PIs) rapid information, nondestructively, about their samples. This information will be in the form of density values throughout the samples, especially within slices 1 mm high. With correct interpretation and good calibration, these values will enable the PI to obtain macro chemical compositional analysis for his/her samples. Alternatively, the technique will provide information about the porosity level and its distribution within the sample. Experience gained with a NASA Microgravity Research Division-sponsored Advanced Technology Development (ATD) project on this topic has brought the technique to a level of maturity at which it has become a viable characterization tool for many of the Materials Science Pls, but with equipment that could never be supported within their own facilities. The existing computed tomography (CT) facility at NASA's Kennedy Space Center (KSC) is ideally situated to furnish information rapidly and conveniently to PIs, particularly immediately before and after flight missions.

Gillies, Donald C.↗
NASA NTRS1977

Probabilistic Fracture Mechanics and Optimum Fracture Control Analytical Procedures for a Reusable Solid Rocket Motor Case

A methodology for the reliability analysis of a reusable solid rocket motor case is discussed. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis is used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects of failure prevention plans such as nondestructive inspection and the material erosion between missions are also considered in the developed procedure for selection of design variables. The reliability-based procedure can be modified to consider other similar structures of reusable space vehicle systems with different failure prevention plans.

Hanagud, S.↗
NASA NTRS1961

Neutralization of Hydroxide Ion in Melt-Grown NaCl Crystals

Many recent studies of solid-state phenomena, particularly in the area of crystal imperfections, have involved the use of melt-grown NaCl single crystals. Quite often trace impurities in these materials have had a prominent effect on these phenomena. Trace amounts of hydroxide ion have been found in melt-grown NaCl crystals. This paper describes a nondestructive method of neutralizing the hydroxide ion in such crystals. Crystals of similar hydroxide content are maintained at an elevated temperature below the melting point of NaCl in a flowing atmosphere containing. dry hydrogen chloride. Heat treatment is continued until an analysis of the test specimens shows no excess hydroxide ion. A colorimetric method previously described4 is used for this analysis.

Otterson, Dumas A.↗
NASA NTRS1979

Reusable solid rocket motor case - Optimum probabilistic fracture control

A methodology for the reliability analysis of a reusable solid rocket motor case is discussed in this paper. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis can be used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects on failure prevention plans such as nondestructive inspection and the material erosion between missions can also be considered in the developed procedure for selection of design variables. The reliability-based procedure that has been discussed in this paper can easily be modified to consider other similar structures of reusable space vehicle systems with different fracture control plans.

Hanagud, S.↗
NASA NTRS1991

The effects of multiple repairs on Inconel 718 weld mechanical properties

Inconel 718 weldments were repaired 3, 6, 9, and 13 times using the gas tungsten arc welding process. The welded panels were machined into mechanical test specimens, postweld heat treated, and nondestructively tested. Tensile properties and high cycle fatigue life were evaluated and the results compared to unrepaired weld properties. Mechanical property data were analyzed using the statistical methods of difference in means for tensile properties and difference in log means and Weibull analysis for high cycle fatigue properties. Statistical analysis performed on the data did not show a significant decrease in tensile or high cycle fatigue properties due to the repeated repairs. Some degradation was observed in all properties, however, it was minimal.

Russell, C. K.↗
NASA NTRS2011

Materials and Nondestructive Evaluation Laboratoriers: User Test Planning Guide

The Materials and Nondestructive Evaluation Laboratory process, milestones and inputs are unknowns to first-time users. The Materials and Nondestructive Evaluation Laboratory Planning Guide aids in establishing expectations for both NASA and non- NASA facility customers. The potential audience for this guide includes both internal and commercial spaceflight hardware developers. It is intended to assist their project engineering personnel in materials analysis planning and execution. Material covered includes a roadmap of the analysis process, roles and responsibilities of facility and user, major milestones, facility capabilities, and inputs required by the facility. Samples of deliverables, products, and inputs necessary to define scope of analysis, cost, and schedule are included as an appendix to the guide.

Schaschl, Leslie↗
NASA NTRSDate not supplied

Transfer function models for using empirical and physics-based simulation signal response data

In many situations, real or induced flaws such as tight cracks with known morphology cannot be manufactured in part geometry specimens or in real parts. Typically, surface fatigue cracks are manufactured in simple geometry specimens such as flat plates, dog-bone shaped flat or cylindrical specimens. If a nondestructive evaluation (NDE)technique is required to provide a reliably detectable flaw size, denoted asa90/95, for induced flaws in a part, then a direct method for qualifying the NDE procedure is to use appropriate induced flaw specimens and perform NDE procedure demonstration on the specimens. Probability of detection (POD)analysis of the empirical data may provide estimation of a90/95. This approach is described as direct POD demonstration testing, which may follow guidelines of MIL-HDBK-1823. This paper considers a case, where embedded tight cracklike induced flaws are to be detected reliably using a signal response based NDE procedure. Here, it is assumed that it is not practical to make surface or embedded induced flaw specimens in part geometry or configuration. Therefore, a direct POD demonstration testing cannot be undertaken. It is also assumed that simulation of signal response is possible for both surface and embedded induced flaws in part geometry specimens using a physics-based model. The proposed approach for NDE procedure qualification uses artificial flaws in simple geometry and part geometry specimens, and induced flaws in the same type of simple geometry specimens. Signal response data is taken on all sets of artificial and induced flaws in simple geometry and part geometry specimens. Moreover, simulated signal response data is generated for surface and embedded flaws. Thus, a case of five signal response versus flaw size datasets is considered. Three of the datasets are empirical and two datasets are physics model-based simulation datasets. A method of devising and using transfer function calculation dataset blocks to estimate the either the reliably detectable flaw size or the demonstration flaw size is provided.

Nondestructive evaluation↗
NASA NTRS1982

Graphite/polyimide technology overview and Space Shuttle Orbiter applications

The materials, production processes, testing procedures, and repair techniques for composite structures on the Orbiter are reviewed. The Orbiter currently features graphite/epoxy payload bay doors, as well as graphite/polyimide elevons, vertical tail, and aft body flap, which can withstand up to 600 F temperatures. Graphite/polyimide is also being considered for areas of the baseline aluminum structure and the thermal protection system in order to achieve a 20-30% weight reduction, i.e., over 7.5 tons. An analysis of the allowable stresses on FRC imide thermal protection system tiles bonded directly to the structure has shown satisfactory performances in high temperature and cryogenic conditions, although failure modes are yet to be determined. Ultrasonic emissions have been used for defect detection in nondestructive evaluations, together with tension, notch, shear, and compression tests. Field repairs have not been perfected, and require the evolution of high temperature adhesives that are curable under vacuum pressure and heat blankets.

Morita, W. H.↗
NASA NTRS2003

Aging Mechanisms and Control: Specialists' Meeting on Life Management Techniques for Aging Air Vehicles

The costs of maintaining ageing aircraft are draining the existing budgets. The Specialist Meeting provided guidance on strategies for the development and implementation of technologies and logistic management processes to reduce this economic burden. The emphasis was on military aircraft, but many of the principles could be applied to other defence systems. The papers covered the entire range of ageing problems including structural integrity, corrosion, avionics, mechanical subsystems, structures and wiring as well as the role of information management. Forty-two papers addressed the safety and economic implications such as fatigue cracking, corrosion, wear and material degradation. Key technologies were discussed, including non-destructive inspection, repair, modifications, prevention analysis, and health management. The shortcomings of current were highlighted and the investment required was identified. The need for research and development was clearly identified.

aging tests (materials)↗
NASA NTRS1983

Eddy-Current Damage Test for Carbon Composites

Nondestructive test method detects cracks in materials of low conductivity. Test setup includes eddycurrent unit with frequency of 2 to 20 MHz/ and storage oscilloscope. High frequency required to assure depth of penetration less than substrate thickness, to prevent thickness from influencing reading. Eddy-current analysis confirmed by visual inspection as damaged area was sectioned and evaluated.

Hamilton, A. B.↗
NASA NTRSDate not supplied

The Additive Manufacturing Moment Measure - A Parallel Computation Technique for Determining Build Variance in the Laser Powder Bed Fusion Process

Additive manufacturing (AM) has unique process attributes that facilitate the creation of optimized, complex, and unique parts for aerospace applications. However, the multi-scale and complicated building process for AM parts can cause unexpected build conditions that result in microstructural variability within the deposited material. The need for richer datasets and computational modeling capabilities to improve AM process reliability is a consequence of this microstructural variability. A computational approach, referred to as the Additive Manufacturing Moment Measure (AM3), addresses this need by leveraging the way AM processes fuse material in precise, incremental steps. During the layering sequence, each previous step contributes to the condition of the current step at the center of the heat source. The precise steps can be selected to systematically create a time-space point field with co-located machine input and in-situ sensor data. The sequential nature of the AM process, coupled with nearest neighbor calculations, allows for a fully parallel computation for part-scale build profile analysis. The AM3 concept introduced here enables part-scale assessment directly from build files and in-situ process monitoring sensors alike. The AM moment measures were calculated for build point fields and compared with co-located in-situ and ex-situ nondestructive evaluation and optical microscopy observations. These comparisons permit a better understanding of how the sequential process actions can affect the quality of a laser powder bed fusion (LPBF) build. Details of the AM3technique will be discussed and compared to measured LPBF part characteristics. The AM3 results indicate a strong potential to advance the qualification process for aerospace applications.

Additive Manufacturing↗