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Results for “test effectiveness”

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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Resonant shattering flares as asteroseismic tests of chiral effective field theory

Chiral effective field theory (𝜒⁢EFT) has proved to be a powerful microscopic framework for predicting the properties of neutron-rich nuclear matter with quantified theoretical uncertainties up to about twice the nuclear saturation density. Tests of 𝜒⁢EFT predictions are typically performed at low densities using nuclear experiments, with neutron star (NS) constraints only being considered at high densities. In this work, we discuss how asteroseismic quasinormal modes within NSs could be used to constrain specific matter properties at particular densities not just the integrated quantities to which bulk NS observables are sensitive. We focus on the crust-core interface mode, showing that measuring this mode's frequency would provide a meaningful test of 𝜒⁢EFT at densities around half the saturation density. Conversely, we use nuclear matter properties predicted by 𝜒⁢EFT to estimate that this mode's frequency is around 185 ± 50Hz. Asteroseismic observables such as resonant phase shifts in gravitational-wave signals and multimessenger resonant shattering flare timings, therefore, have the potential to provide useful tests of 𝜒⁢EFT.

effective field theory↗
NASA NTRS2007

A Study to Estimate the Effectiveness of Visual Testing Training for Aviation Maintenance Management

The Air Commerce Act of 1926 set the beginning for standards in aviation maintenance. Even after deregulation in the late l970s, maintenance standards and requirements still have not changed far from their initial criteria. After a potential candidate completes Federal Aviation Administration training prerequisites, they may test for their Airframe and Powerplant (A&P) certificate. Performing maintenance in the aviation industry for a minimum of three years, the technician may then test for their Inspection Authorization (IA). After receiving their Airframe and Powerplant certificate, a technician is said to have a license to perform. At no time within the three years to eligibility for Inspection Authorization are they required to attend higher-level inspection training. What a technician learns in the aviation maintenance industry is handed down from a seasoned technician to the new hire or is developed from lessons learned on the job. Only in Europe has the Joint Aviation Authorities (JAA) required higher-level training for their aviation maintenance technicians in order to control maintenance related accidents (Lu, 2005). Throughout the 1990s both the General Accounting Office (GAO) and the National Transportation Safety Board (NTSB) made public that the FAA is historically understaffed (GAO, 1996). In a safety recommendation the NTSB stated "The Safety Board continues to lack confidence in the FAA's commitment to provide effective quality assurance and safety oversight of the ATC system (NTSB, 1990)." The Federal Aviation Administration (FAA) has been known to be proactive in creating safer skies. With such reports you would suspect the FAA to also be proactive in developing more stringent inspection training for aviation maintenance technicians. The purpose of this study is to estimate the effectiveness of higher-level inspection training, such as Visual Testing (VT) for aviation maintenance technicians, to improve the safety of aircraft and to make recommendations to management with regard to the value of such training.

Law, Lewis Lyle↗
NASA NTRS1985

Longitudinal compressive failure modes in fiber composites End attachment effects on IITRI type test specimens

The end-attachment effects on longitudinal compressive strength of IITRI type specimen unidirectional fiber composites are formally assessed using finite-element analysis (FEA) in conjunction with composite mechanics. Sixteen different cases were analyzed to evaluate end-attachment effects (such as degree of misalignment, type of misalignment, progressive end-tab debonding, and specimen thickness) on stress distribution, peak stresses, buckling loads, and buckling mode shapes. The results obtained from the FEA and comparisons with fractured specimens show that eccentricities induce bending-type stresses which peak near the end-tabs and cause flexural type fracture. Also, guidelines are included for placing back-to-back strain gages to measure the presence/absence of possible end-attachment and eccentricity effects.

Chamis, C. C.↗
NASA NTRS1972

Correcting for nonlinear effects in fracture toughness testing.

Expressions for fracture toughness, which include nonlinear effects due to crack front plastic yield and possible small crack extension prior to fracture instability, are obtained for several test specimen configurations. Inclusion of such effects is based on a simple compliance type determination of the total energy rate at onset of fast fracture.

Liebowitz, H.↗
NASA NTRS1989

The effect of test-cell pressure on resistojet nozzle flow

Previous experimental work has shown that measured resistojet thrust decreases from that obtained at hard vacuum conditions as the test-cell pressure rises above 0.001 torr. Thrust losses have been observed for both cold and heated flow conditions, and the most significant losses have been experienced using thrusters with low Reynolds number flow and high area ratio nozzles. In order to further investigate nozzle flow characteristics, a pressure probe having four degrees of freedom has been used to obtain stagnation pressure surveys across the nozzle exit planes of four resistojets. The surveys show a change in the ratio of the supersonic core to the viscous boundary layer flow areas as the test-cell pressure increases. The surveys are also used for detecting whether an oblique shock is present in an overexpanded nozzle flow. Thruster temperature measurements and nozzle exit plane pressure surveys indicate that thrust losses are the combined result of convection heat losses and nozzle flow momentum effects.

Penko, Paul F.↗
DOE OSTI2025

The role of specimen size and grain boundary characteristics in the yield strength of tungsten in microtensile tests

To effectively use the measured properties from small-scale tensile tests for bulk material performance predictions, it is essential to understand the threshold of specimen size-effect strengthening and the interaction between dislocations and microstructures within miniaturized specimens. This study uses pure tungsten to investigate the size effect in terms of specimen size, grain size, and grain boundary characteristics relative to the yield strength of tungsten at room temperature. We evaluate the transition from miniaturized specimen properties to bulk properties and the deformation behavior through small-scale tensile tests of three specimen sizes (large: 80 × 100 × 233 µm³; medium: 7 × 7 × 18 µm³; and small: 2 × 2 × 5 µm³). The testing results reveal that the small and medium specimens exhibit high yield strength with ductile behavior, while the large specimens exhibit brittle failure, consistent with the room temperature strength of tungsten, indicating bulk behavior. We further explore the specimen size-effect sensitivity to yield stress and the scaling relationship between yield strength and the number of grains involved in the deformation. A power-law relationship with the exponent value of approximately -0.5 was found in the yield strength–grain number scaling, implying the Hall-Petch like behavior. A minimum of 7–17 effective grain boundaries across the tensile gauge dimension is required to accurately measure bulk properties.

36 - MATERIALS SCIENCE↗
NASA NTRS1988

F-15 SMTD low speed jet effects wind tunnel test results

Key results from low speed wind tunnel testing of the F-15 STOL and Maneuver Technology Demonstrator (SMDT) with thrust reversers are presented. Longitudinally, the largest induced increments in the stability and control occur at landing gear height. These generally reflect an induced lift loss and a nose-up pitching moment, and vary with sideslip. Directional stability is reduced at landing gear height with full reverse thrust. Nonlinearities in the horizontal tail effectiveness are found in free air and at landing gear height.

Blake, William B.↗
NASA NTRS1986

A summary of Reynolds number effects on some recent tests in the Langley 0.3-meter transonic cryogenic tunnel

Reynolds number effects noted from selected test programs conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT) are discussed. The tests, which cover a unit Reynolds number range from about 2.0 to 80.0 million per foot, summarize effects of Reynolds number on: (1) aerodynamic data from a supercritical airfoil, (2) results from several wall interference correction techniques, and (3) results obtained from advanced, cryogenic tests techniques. The test techniques include: (1) use of a cryogenic sidewall boundary layer removal system, (2) detailed pressure and hot wire measurements to determine test section flow quality, and (3) use of a new hot film system suitable for transition detection in a cryogenic wind tunnel. The results indicate that Reynolds number effects appear most significant when boundary layer transition effects are present and at high lift conditions when boundary layer separation exists on both the model and the tunnel sidewall.

Johnson, C. B.↗
NASA NTRS1975

The effect of sunshine testing on terrestrial solar cell system components

Samples of FEP encapsulated silicon solar cells and various potential encapsulation or cover materials were subjected to accelerated and real time testing. By measuring changes in solar cell output or optical transmission as a function of exposure the durability of the samples was evaluated. Results are presented.

Forestieri, A. F.↗