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Results for “cryogenic temperature”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Deformation and fracture of thin sheet aluminum-lithium alloys: The effect of cryogenic temperatures

The objective is to characterize the fracture behavior and to define the fracture mechanisms for new Al-Li-Cu alloys, with emphasis on the role of indium additions and cryogenic temperatures. Three alloys were investigated in rolled product form: 2090 baseline and 2090 + indium produced by Reynolds Metals, and commercial AA 2090-T81 produced by Alcoa. The experimental 2090 + In alloy exhibited increases in hardness and ultimate strength, but no change in tensile yield strength, compared to the baseline 2090 composition in the unstretched T6 condition. The reason for this behavior is not understood. Based on hardness and preliminary Kahn Tear fracture experiments, a nominally peak-aged condition was employed for detailed fracture studies. Crack initiation and growth fracture toughness were examined as a function of stress state and microstructure using J(delta a) methods applied to precracked compact tension specimens in the LT orientation. To date, J(delta a) experiments have been limited to 23 C. Alcoa 2090-T81 exhibited the highest toughness regardless of stress state. Fracture was accompanied by extensive delamination associated with high angle grain boundaries normal to the fatigue precrack surface and progressed microscopically by a transgranular shear mechanism. In contrast the two peak-aged Reynolds alloys had lower toughness and fracture was intersubgranular without substantial delamination. The influences of cryogenic temperature, microstructure, boundary precipitate structure, and deformation mode in governing the competing fracture mechanisms will be determined in future experiments. Results contribute to the development of predictive micromechanical models for fracture modes in Al-Li alloys, and to fracture resistant materials.

Wagner, John A.↗
NASA NTRS1970

Preparation of fine-particles at cryogenic temperatures

Flash freezing process yields gelling agent for use at cryogenic temperatures. Vaporized material, diluted with an inert gas, is injected below the surface of an agitated cryogenic liquid. This method disperses particles of chlorine trifluoride in liquid oxygen difluoride.

Globus, H.↗
NASA NTRS1990

X-ray thin foil filters at cryogenic temperatures

The X-Ray Spectrometer (XRS), which is being developed for one of the focal plane instruments of the Advanced X-Ray Astrophysics Facility, requires filters with high X-ray transmittance, high background rejection, and operation at cryogenic temperatures. Thin foil filters can provide high X-ray transmittance and the required rejection for low-energy radiation. The results of the test program demonstrate that these filters are fully successful at cryogenic temperatures and, therefore, can provide blocking filters for the XRS with the required performance.

Keski-Kuha, Ritva A. M.↗
DOE OSTI2024

Cryogenic temperatures promote the pressure-induced polymorphic transition in CoCrFeMnNi high entropy alloy

Pressure-induced polymorphism has recently been demonstrated in several high entropy alloys. This offers a new window into the much-debated issue of phase selection and stability in these systems. Here, we examine the effect of cryogenic temperatures on the pressure-induced transition from face centered cubic to hexagonal close-packed structures of the prototype CoCrFeMnNi (Cantor) alloy. We observe a reduction in the critical pressure for the onset of the polymorphic transition as the temperature decreases, confirming the progressive stabilization of the hexagonal phase with decreasing temperature previously predicted by ab initio calculations accounting for magnetic interactions. We argue that in situ high-pressure experiments at cryogenic temperatures, which suppress time-dependent transformation triggered at higher temperatures, present a unique opportunity to significantly improve our understanding of these complex alloys.

alloys↗
NASA NTRS1993

Techniques for improving the accuracy of cryogenic temperature measurement in ground test programs

The performance of a sensor is often evaluated by determining to what degree of accuracy a measurement can be made using this sensor. The absolute accuracy of a sensor is an important parameter considered when choosing the type of sensor to use in research experiments. Tests were performed to improve the accuracy of cryogenic temperature measurements by calibration of the temperature sensors when installed in their experimental operating environment. The calibration information was then used to correct for temperature sensor measurement errors by adjusting the data acquisition system software. This paper describes a method to improve the accuracy of cryogenic temperature measurements using corrections in the data acquisition system software such that the uncertainty of an individual temperature sensor is improved from plus or minus 0.90 deg R to plus or minus 0.20 deg R over a specified range.

Dempsey, Paula J.↗
NASA NTRS1972

Use of thin plastic films at cryogenic temperatures

Commercially available plastic film materials that remain flexible at cryogenic temperatures and resist failures caused by folds and wrinkles created during expulsion were investigated for use in expulsion bladders for liquefied gases. Compatible adhesive systems, fabrication techniques, and results of impact and dynamic loading tests are summarized.

Lark, R. F.↗