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  • Other Sources  (2)
  • 2020-2022  (2)
  • 1
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    Optimized reconstruction of the crystallographic orientation density function based on a reduced set of orientations (2021)
    Details
    Publication Date: 2021-10-12
    Description: Crystallographic textures, as they develop for example during cold forming, can have a significant influence on the mechanical properties of metals, such as plastic anisotropy. Textures are typically characterized by a non-uniform distribution of crystallographic orientations that can be measured by diffraction experiments like electron backscatter diffraction (EBSD). Such experimental data usually contain a large number of data points, which must be significantly reduced to be used for numerical modeling. However, the challenge in such data reduction is to preserve the important characteristics of the experimental data, while reducing the volume and preserving the computational efficiency of the numerical model. For example, in micromechanical modeling, representative volume elements (RVEs) of the real microstructure are generated and the mechanical properties of these RVEs are studied by the crystal plasticity finite element method. In this work, a new method is developed for extracting a reduced set of orientations from EBSD data containing a large number of orientations. This approach is based on the established integer approximation method and it minimizes its shortcomings. Furthermore, the L1 norm is applied as an error function; this is commonly used in texture analysis for quantitative assessment of the degree of approximation and can be used to control the convergence behavior. The method is tested on four experimental data sets to demonstrate its capabilities. This new method for the purposeful reduction of a set of orientations into equally weighted orientations is not only suitable for numerical simulation but also shows improvement in results in comparison with other available methods.
    Keywords: 548 ; texture reconstruction ; integer approximation ; crystal plasticity ; micromechanical modeling
    Language: English
    Type: map
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    CITATION GEO-LEO
  • 2
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    Geophysical Retrievals During OLYMPEX/RADEX Using the Advanced Microwave Precipitation Radiometer (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-23
    Description: The Olympic Mountains Experiment and Radar Definition Experiment (OLYMPEX/RADEX) took place Fall 2015 Spring 2016 in Washington, United States. The Advanced Microwave Precipitation Radiometer (AMPR) was flown on NASA ER-2 aircraft during science flights. This poster summarizes advancements in geophysical retrievals using AMPR data from OLYMPEX/RADEX. Calm ocean has low emissivity at microwave frequencies; wind creates foam increases emissivity. Liquid hydrometeors in atmosphere generally yield higher brightness temperature (T(sub b)) due to their higher reflectance. Effect of liquid hydrometeors depends highly on frequency resonance increases with increasing frequency, as does absorption (e.g., due to water vapor). Retrieve cloud liquid water (CLW), water vapor (WV), and 10-m wind speed (WS) using multiple T(sub b).
    Keywords: Geosciences (General)
    Type: MSFC-E-DAA-TN76718 , AMS Annual Meeting; Jan 12, 2020 - Jan 16, 2020; Boston, MA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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