12,816 research outputs found
A parametric study on the buckling of functionally graded material plates with internal discontinuities using the partition of unity method
In this paper, the effect of local defects, viz., cracks and cutouts on the
buckling behaviour of functionally graded material plates subjected to
mechanical and thermal load is numerically studied. The internal
discontinuities, viz., cracks and cutouts are represented independent of the
mesh within the framework of the extended finite element method and an enriched
shear flexible 4-noded quadrilateral element is used for the spatial
discretization. The properties are assumed to vary only in the thickness
direction and the effective properties are estimated using the Mori-Tanaka
homogenization scheme. The plate kinematics is based on the first order shear
deformation theory. The influence of various parameters, viz., the crack length
and its location, the cutout radius and its position, the plate aspect ratio
and the plate thickness on the critical buckling load is studied. The effect of
various boundary conditions is also studied. The numerical results obtained
reveal that the critical buckling load decreases with increase in the crack
length, the cutout radius and the material gradient index. This is attributed
to the degradation in the stiffness either due to the presence of local defects
or due to the change in the material composition.Comment: arXiv admin note: text overlap with arXiv:1301.2003, arXiv:1107.390
Muon spin rotation studies of niobium for superconducting RF applications
In this work we investigate superconducting properties of niobium samples via
application of the muon spin rotation/relaxation (muSR) technique. We employ
for the first time the muSR technique to study samples that are cutout from
large and small grain 1.5 GHz radio frequency (RF) single cell niobium
cavities. The RF test of these cavities was accompanied by full temperature
mapping to characterize the RF losses in each of the samples. Results of the
muSR measurements show that standard cavity surface treatments like mild baking
and buffered chemical polishing (BCP) performed on the studied samples affect
their surface pinning strength. We find an interesting correlation between high
field RF losses and field dependence of the sample magnetic volume fraction
measured via muSR. The muSR line width observed in ZF-muSR measurements matches
the behavior of Nb samples doped with minute amounts of Ta or N impurities. An
upper bound for the upper critical field Hc2 of these cutouts is found.Comment: 20 pages, 14 figure
A Rayleigh-Ritz analysis methodology for cutouts in composite structures
A new Rayleigh-Ritz stress analysis methodology that was developed for composite panels containing cutouts is described. The procedure, which makes use of a general assumed displacement field, accommodates circular and elliptical cutouts in biaxially loaded rectangular composite panels. Symmetric integral padups around the cutout can be included in the analysis. Benchmark results are presented to demonstrate the accuracy of the technique. Strength predictions based on the average stress criterion are generated and compared with experimental data. Finally, the stress analysis methodology is integrated into a design procedure for sizing integral padups around circular cutouts, and a sample problem is solved to illustrate its use
The compressive failure of graphite/epoxy plates with circular holes
The behavior of fiber reinforced composite plates containing a circular cutout was characterized in terms of geometry (thickness, width, hole diameter), and material properties (bending/extensional stiffness). Results were incorporated in a data base for use by designers in determining the ultimate strength of such a structure. Two thicknesses, 24 plies and 48 plies were chosen to differentiate between buckling and strength failures due to the presence of a cutout. Consistent post-buckling strength was exhibited by both laminate configurations
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