1,426 research outputs found
The 3D inelastic analysis methods for hot section components
The objective of this research is to develop an analytical tool capable of economically evaluating the cyclic time dependent plasticity which occurs in hot section engine components in areas of strain concentration resulting from the combination of both mechanical and thermal stresses. The techniques developed must be capable of accommodating large excursions in temperatures with the associated variations in material properties including plasticity and creep. The overall objective of this proposed program is to develop advanced 3-D inelastic structural/stress analysis methods and solution strategies for more accurate and yet more cost effective analysis of combustors, turbine blades, and vanes. The approach will be to develop four different theories, one linear and three higher order with increasing complexities including embedded singularities
The 3D inelastic analysis methods for hot section components
Advanced 3-D inelastic structural/stress analysis methods and solution strategies for more accurate and yet more cost-effective analysis of combustors, turbine blades, and vanes are being developed. The approach is to develop four different theories, one linear and three higher order with increasing complexities including embedded singularities. Progress in each area is reported
Constitutive modeling for isotropic materials
The unified constitutive theories for application to typical isotropic cast nickel base supperalloys used for air-cooled turbine blades were evaluated. The specific modeling aspects evaluated were: uniaxial, monotonic, cyclic, creep, relaxation, multiaxial, notch, and thermomechanical behavior. Further development of the constitutive theories to model thermal history effects, refinement of the material test procedures, evaluation of coating effects, and verification of the models in an alternate material will be accomplished in a follow-on for this base program
Coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures
Accomplishments are described for the first year effort of a 5-year program to develop a methodology for coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures. These accomplishments include: (1) the results of the selective literature survey; (2) 8-, 16-, and 20-noded isoparametric plate and shell elements; (3) large deformation structural analysis; (4) eigenanalysis; (5) anisotropic heat transfer analysis; and (6) anisotropic electromagnetic analysis
Molecular clouds and clumps in the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
The Boston University-Five College Radio Astronomy Observatory (BU-FCRAO)
Galactic Ring Survey (GRS) of 13 CO (1-0) emission covers Galactic longitudes
18 deg < l < 55.7 deg and Galactic latitudes |b| <= 1 deg. Using the SEQUOIA
array on the FCRAO 14m telescope, the GRS fully sampled the 13 CO Galactic
emission (46 arcsec angular resolution on a 22 arcsec grid) and achieved a
spectral resolution of 0.21 km/s. Because the GRS uses 13 CO, an optically thin
tracer, rather than 12 CO, an optically thick tracer, the GRS allows a much
better determination of column density and also a cleaner separation of
velocity components along a line of sight. With this homogeneous, fully-sampled
survey of 13 CO, emission, we have identified 829 molecular clouds and 6124
clumps throughout the inner Galaxy using the CLUMPFIND algorithm. Here we
present details of the catalog and a preliminary analysis of the properties of
the molecular clouds and their clumps. Moreover, we compare clouds inside and
outside of the 5 kpc ring and find that clouds within the ring typically have
warmer temperatures, higher column densities, larger areas, and more clumps
compared to clouds located outside the ring. This is expected if these clouds
are actively forming stars. This catalog provides a useful tool for the study
of molecular clouds and their embedded young stellar objects.Comment: 29 pages. ApJ in pres
Evidence for the Galactic X-ray Bulge II
A mosaic of 5 \ros~PSPC pointed observations in the Galactic plane
() reveals X-ray shadows in the keV band cast by
distant molecular clouds. The observed on-cloud and off-cloud X-ray fluxes
indicate that % and % of the diffuse X-ray background in this
direction in the \tq~keV and 1.5 keV bands, respectively, originates behind the
molecular gas which is located at 3 kpc from the Sun. The implication of
the derived background X-ray flux beyond the absorbing molecular cloud is
consistent with, and lends further support to recent observations of a Galactic
X-ray bulge.Comment: 19 pages, 5 figures, 2 table
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