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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Detection of fatigue cracks by nondestructive testing methods

The effectiveness was assessed of various NDT methods to detect small tight cracks by randomly introducing fatigue cracks into aluminum sheets. The study included optimizing NDT methods calibrating NDT equipment with fatigue cracked standards, and evaluating a number of cracked specimens by the optimized NDT methods. The evaluations were conducted by highly trained personnel, provided with detailed procedures, in order to minimize the effects of human variability. These personnel performed the NDT on the test specimens without knowledge of the flaw locations and reported on the flaws detected. The performance of these tests was measured by comparing the flaws detected against the flaws present. The principal NDT methods utilized were radiographic, ultrasonic, penetrant, and eddy current. Holographic interferometry, acoustic emission monitoring, and replication methods were also applied on a reduced number of specimens. Generally, the best performance was shown by eddy current, ultrasonic, penetrant and holographic tests. Etching provided no measurable improvement, while proof loading improved flaw detectability. Data are shown that quantify the performances of the NDT methods applied.

Anderson, R. T.↗
NASA NTRS1976

Flight-test experience of a helicopter encountering an airplane trailing vortex

This paper presents results of a flight-test experiment of a UH-1H helicopter encountering the vortex wake of a C-54 airplane. The helicopter was instrumented to record the pilot control inputs, determine the upset experience, and measure critical loads within the rotor system. During the flight-test program 132 penetrations of the vortex wake were made by the helicopter at separation distances from 3/8 to 6-1/2 nautical miles. Test results indicated that the helicopter upsets and the vortex induced blade loads experienced were minimal and well within safe limits. The upsets were very mild when compared to a typical response of a small airplane to the vortex wake of the C-54 airplane.

Dunham, R. E., Jr.↗
NASA NTRS1992

External tank space debris considerations

Orbital debris issues associated with maintaining a Space Shuttle External Tank (ET) on orbit are presented. The first issue is to ensure that the ET does not become a danger to other spacecraft by generating space debris, and the second is to protect the pressurized ET from penetration by space debris or meteoroids. Tests on shield designs for penetration resistance showed that when utilized with an adequate bumper, thermal protection system foam on the ET is effective in preventing penetration.

Elfer, N.↗
NASA NTRS2024

Mapping Ice Buried by the 1875 and 1961 Tephra of Askja Volcano, Northern Iceland using Ground-Penetrating Radar: Implications for Askja Caldera as a Geophysical Testbed for In-Situ Resource Utilization

Eruptions of the Askja Volcano in Northern Iceland in 1875 and 1961 blanketed the caldera with rhyolitic and basaltic tephra deposits, respectively, which preserved layers of seasonal snowpack as massive ice. Askja serves as an operational and geophysical analog to test ground-penetrating radar field and analysis techniques for in-situ resource utilization objectives relevant to the martian and lunar environments. We conducted ground-penetrating radar surveys at center frequencies of 200, 400, and 900 MHz to map the thickness and extent of tephra deposits and underlying massive ice at three caldera sites. We identified up to 1 meter of tephra preserving up to 4.5 meters of massive ice. We measured the real dielectric permittivity of the overlying tephra and the total attenuation at each frequency of the tephra and ice. A key objective of our investigation was to determine if this attenuation (or loss) could be used as an additional, identifying characteristic of massive ice preserved at depth when compared to ice-free stratigraphy. Loss rates of the ice-rich subsurface decreases with increasing ice thickness relative to the overburden which may constitute a possible signature. Attenuation also increased with increasing frequency. The tephra, ice, and other volcanic deposits at each of our three caldera sites and the ice-free pumice-mantled 1961 Vikrahraun lava flow exhibited a characteristically low loss rate at all frequencies. This result highlights the ambiguity associated with identifying the unique signature of ice within low-loss stratigraphies, a possible challenge for its identification in the martian or lunar subsurface using radar.

Emileigh S. Shoemaker↗
NASA NTRS1974

The detection of fatigue cracks by nondestructive test methods

X-radiographic, penetrant, ultrasonic, and eddy current techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens. One hundred eighteen specimens containing a total of 328 fatigue cracks were evaluated. The cracks ranged in length from 1.27 to 0.018 cm and in depth from 0.451 to 0.003 cm. Specimen thicknesses were nominally 0.152 and 0.532 cm. Specimens were evaluated in the 'as-milled' surface condition, in the etched surface condition, and, after proof loading, in a randomized inspection sequence. Results of the nondestructive test evaluations were compared with actual crack size obtained by analysis of the fractured specimens. Inspection data were then analyzed to provide a statistical basis for determining the threshold crack detection sensitivity for each of the inspection techniques at a 95% probability and 95% confidence level.

Rummel, W. D.↗
NASA NTRS1974

The detection of fatigue cracks by nondestructive testing methods

X-radiographic penetrant, ultrasonic, eddy current, holographic, and acoustic emission techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens. One hundred eighteen specimens containing a total of 328 fatigue cracks were evaluated. The cracks ranged in length from 0.500 inch (1.27 cm) to 0.007 inch (0.018 cm) and in depth from 0.178 inch (0.451 cm) and 0.001 inch (0.003 cm). Specimen thicknesses were nominally 0.060 inch (0.152 cm) and 0.210 inch (0.532 cm) and surface finishes were nominally 32 and 125 rms and 64 and 200 rms respectively. Specimens were evaluated in the as-milled surface condition, in the chemically milled surface condition and, after proof loading, in a randomized inspection sequence. Results of the nondestructive test (NDT) evaluations were compared with actual crack size obtained by measurement of the fractured specimens. Inspection data was then analyzed to provide a statistical basis for determinating the threshold crack detection sensitivity (the largest crack size that would be missed) for each of the inspection techniques at a 95% probability and 95% confidence level.

Rummel, W. D.↗
NASA NTRS2004

A Model for Shear Layer Effects on Engine Noise Radiation

Prediction of aircraft engine noise is an important aspect of addressing the issues of community noise and cabin noise control. The development of physics based methodologies for performing such predictions has been a focus of Computational Aeroacoustics (CAA). A recent example of code development in this area is the ducted fan noise propagation and radiation code CDUCT-LaRC. Included within the code is a duct radiation model that is based on the solution of FfowcsWilliams-Hawkings (FW-H) equation with a penetrable data surface. Testing of this equation for many acoustic problems has shown it to provide generally better results than the Kirchhoff formula for moving surfaces. Currently, the data surface is taken to be the inlet or exhaust plane for inlet or aft-fan cases, respectively. While this provides reasonable results in many situations, these choices of data surface location lead to a few limitations. For example, the shear layer between the bypass ow and external stream can refract the sound waves radiated to the far field. Radiation results can be improved by including this effect, as well as the rejection of the sound in the bypass region from the solid surface external to the bypass duct surrounding the core ow. This work describes the implementation, and possible approximation, of a shear layer boundary condition within CDUCT-LaRC. An example application also illustrates the improvements that this extension offers for predicting noise radiation from complex inlet and bypass duct geometries, thereby providing a means to evaluate external treatments in the vicinity of the bypass duct exhaust plane.

Nark, Douglas M.↗
NASA NTRS1973

Improved spatial uniformity of beam-plane interaction by means of inverse rastering

An analysis is presented that shows the desirability and feasibility of conducting irradiations of large test objects by beams of penetrating radiation, by the method of moving the test object back and forth through the beam, rather than by sweeping the beam across the object. An extension of this method of inverse rastering allows the generation of composite beams with any desired intensity-vs-energy spectrum, obviating the need to determine equivalent damage factors for every energy in the spectrum.

Miller, C. G.↗
NASA NTRS1974

Drag and distribution measurements of single-element fuel injectors for supersonic combustors

The drag caused by several vortex generating fuel injectors for scramjet combustors was measured in a Mach 2 to 3.5 airstream. Injector drag was found to be strongly dependent on injector thickness ratio. The distribution of helium injected into the stream was measured both in the near field and the far field of the injectors for a variety of pressure ratios. The far field results differed appreciably from measurements in the near field. Injection pressure ratio was found to profoundly influence the penetration. One of the aerowing configurations tested yielded low drag consistent with desirable penetration and spreading characteristics.

Povinelli, L. A.↗
NASA NTRS1973

Simulated meteoroid penetration of reusable surface insulation

Meteoroid impact simulation test results on insulation tiles were used to determine penetration resistance of reusable surface insulation attached to simulated shuttle structures. The probability of no meteoroid damage to a typical shuttle orbiter was determined. Specimens were plasma jet tested to determine effects of various size meteoroid cavities on their thermal performance. None of the tiles failed catastrophically, but large, egg-shaped craters did result from meteoroid penetration. The metallic side of a specimen that was completely penetrated showed a petalled hole typical for thin gage shielded structures.

Lehman, J. K.↗
DOE OSTI2026

Experimental and Computational Study of Weld Drop-Through Hydraulic Effects in Multi-Layer Concentric Pipes Servicing Cryogenic Liquid Hydrogen

The Cryogenic Moderator System (CMS) at the Oak Ridge National Laboratory (ORNL)-Spallation Neutron Source (SNS) supplies liquid hydrogen, through vacuum insulated transfer lines to the moderators. The welding process used to make the transfer lines produces weld drop-through, which can constrict the flow of hydrogen and/or cause thermal bridges between adjacent layers. To ensure proper operation of the CMS it is therefore necessary to conduct a flow test to verify the pressure drop caused by the welds. Measurements in as-built piping sections intended to provide liquid hydrogen service to the SNS-CMS system were performed to test the effect of weld penetrations into the fluid flow area focusing on pressure drop effects. The reference test sections were designed using prototypical piping dimensions, materials and expected penetration welds. A numerical study using Computational Fluid Dynamics (CFD) tools in the transfer lines provided a conversion factor from the pressure drop measured in the lines with water to the expected pressure drop using liquid cryogenic hydrogen. The results show evidence of a maximum pressure drop modification in water of 78 KPa in the tested parts, which scales to liquid hydrogen as PHydrogen = 5.2 KPa. The maximum measured equivalent blockage area percentage was found in the as-built TDM transfer line spool 2 with a value of 31%. The measured values obtained in the as-built transfer lines provided accurate values to estimate the expected total pressure drop in the CMS system providing operational limits for the current recirculatory capacity. The effect of the weld drop-through in hydrogen evacuation capacity scenarios was better evaluated as a result of this study.

Dominguez-Ontiveros, Elvis [ORNL] (ORCID:000000018↗
NASA NTRS2012

Two Dimensional Heat Transfer around Penetrations in Multilayer Insulation

The objective of this task was to quantify thermal losses involving integrating MLI into real life situations. Testing specifically focused on the effects of penetrations (including structural attachments, electrical conduit/feedthroughs, and fluid lines) through MLI. While there have been attempts at quantifying these losses both analytically and experimentally, none have included a thorough investigation of the methods and materials that could be used in such applications. To attempt to quantify the excess heat load coming into the system due to the integration losses, a calorimeter was designed to study two dimensional heat transfer through penetrated MLI. The test matrix was designed to take as many variables into account as was possible with the limited test duration and system size. The parameters varied were the attachment mechanism, the buffer material (for buffer attachment mechanisms only), the thickness of the buffer, and the penetration material. The work done under this task is an attempt to measure the parasitic heat loads and affected insulation areas produced by system integration, to model the parasitic loads, and from the model produce engineering equations to allow for the determination of parasitic heat loads in future applications. The methods of integration investigated were no integration, using a buffer to thermally isolate the strut from the MLI, and temperature matching the MLI on the strut. Several materials were investigated as a buffer material including aerogel blankets, aerogel bead packages, cryolite, and even an evacuated vacuum space (in essence a no buffer condition).

Johnson, Wesley L.↗
NASA NTRS1973

Detection of lack of fusion using opaque additives, phase 2

Plasma-sprayed copper coatings were developed to protect the aluminum surfaces of spacecraft structures from oxidation, as well as to provide a means of reliable nondestructive X-ray inspection of possible incomplete weldment penetration. Sixty day storage tests of coated aluminum samples indicated the promise of long-term oxidation protection, but revealed no advantage in detecting penetration defects. Delta-scan techniques were used, and peen plating as a means of applying copper to the aluminum surface was investigated.

Cook, J. L.↗
NASA NTRS1990

Fluorescent penetrant inspection

The purpose of this experiment is to familiarize the student with fluorescent penetrant inspection and to relate it to classification of various defects. The penetrant method of nondestructive testing is a method for finding discontinuities open to the surface in solids and essentially nonporous bodies. The method employs a penetrating liquid which is applied over the surface and enters the discontinuity or crack. After the excess of penetrant has been cleaned from the surface, the penetrant which exudes or is drawn back out of the crack indicates the presence and location of a discontinuity. The experimental procedure is described.

Sastri, Sankar↗
NASA NTRS2011

Sharing of Tank Information

Test Rationale -- Attempt to Address 10% vs. 25+% effects of crater penetration on full scale titanium alloy tanks and comparison to plate tests Utilize Baseline Burst Pressure versus HVI impacted vessels as gauge of effects Examine craters (post test) to determine penetration characteristics on a fluid filled vessel versus plate tests. Examine crater effects leading to vessel failure (if any).

Tamminga, Joshua D.↗
NASA NTRS1963

IMPACT PHENOMENA

Results of hypervelocity impact tests are analyzed, determining the penetration depth and time as a function of impact velocity

IMPACT TEST↗
NASA NTRS2011

A Comparison of the Capability of Sensitivity Level 3 and Sensitivity Level 4 Fluorescent Penetrants to Detect Fatigue Cracks in Various Metals

In April 2008, NASA-STD-5009 established a requirement that only sensitivity level 4 penetrants are acceptable for NASA Standard Level liquid penetrant inspections. Having NASA contractors change existing processes or perform demonstration tests to certify sensitivity level 3 penetrants posed a potentially huge cost to the Agency. This study was conducted to directly compare the probability of detection (POD) of sensitivity level 3 and level 4 penetrants using both Method A and Method D inspection processes. POD demonstration tests were performed on 6061-Al, Haynes 188 and Ti-6Al-4V crack panel sets. The study results strongly support the conclusion that sensitivity level 3 penetrants are acceptable for NASA Standard Level inspections.

Parker, Bradford H.↗