951 research outputs found
Porous LSCF/Dense 3YSZ Interface Fracture Toughness Measured by Single Cantilever Beam Wedge Test
Sandwich specimens were prepared by firing a thin inter-layer of porous
La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) to bond a thin tetragonal yttria-stabilised
zirconia (YSZ) beam to a thick YSZ substrate. Fracture of the joint was
evaluated by introducing a wedge between the two YSZ adherands so that the
stored energy in the thin YSZ cantilever beam drives a stable crack in the
adhesive bond and allows the critical energy release rate for crack extension
(fracture toughness) to be measured. The crack path in most specimens showed a
mixture of adhesive failure (at the YSZ-LSCF interface) and cohesive failure
(within the LSCF). It was found that the extent of adhesive fracture increased
with firing temperature and decreased with LSCF layer thickness. The adhesive
failures were mainly at the interface between the LSCF and the thin YSZ beam
and FEM modelling revealed that this is due to asymmetric stresses in the LSCF.
Within the firing temperature range of 1000-1150C, the bonding fracture
toughness appears to have a strong dependence on firing temperature. However,
the intrinsic adhesive fracture toughness of the LSCF/YSZ interface was
estimated to be 11 Jm2 and was not firing temperature dependent within the
temperature range investigated.Comment: 13 figures, 1 table, journal paper publishe
The Economics of a Centralized Judiciary: Uniformity, Forum Shopping and the Federal Circuit
In 1982, the US Congress established the Court of Appeals for the Federal Circuit (CAFC) as the sole appellate court for patent cases. Ostensibly, this court was created to eliminate inconsistencies in the application and interpretation of patent law across federal courts, and thereby mitigate the incentives of patentees and alleged infringers to "forum shop" for a preferred venue. We perform the first econometric study of the extent of non-uniformity and forum shopping in the pre-CAFC era and of the CAFC's impact on these phenomena. We find that in patentee-plaintiff cases the pre-CAFC era was indeed characterized by significant non-uniformity in patent validity rates across circuits and by forum shopping on the basis of validity rates. We find weak evidence that the CAFC has increased uniformity of validity rates and strong evidence that forum shopping on the basis of validity rates ceased several years prior to the CAFC's establishment. In patentee-defendant cases, we find that validity rates are lower on average, but do not find either significant non-uniformity of validity rates across circuits or significant forum shopping.
LDEF data: Comparisons with existing models
The relationship between the observed cratering impact damage on the Long Duration Exposure Facility (LDEF) versus the existing models for both the natural environment of micrometeoroids and the man-made debris was investigated. Experimental data was provided by several LDEF Principal Investigators, Meteoroid and Debris Special Investigation Group (M&D SIG) members, and by the Kennedy Space Center Analysis Team (KSC A-Team) members. These data were collected from various aluminum materials around the LDEF satellite. A PC (personal computer) computer program, SPENV, was written which incorporates the existing models of the Low Earth Orbit (LEO) environment. This program calculates the expected number of impacts per unit area as functions of altitude, orbital inclination, time in orbit, and direction of the spacecraft surface relative to the velocity vector, for both micrometeoroids and man-made debris. Since both particle models are couched in terms of impact fluxes versus impactor particle size, and much of the LDEF data is in the form of crater production rates, scaling laws have been used to relate the two. Also many hydrodynamic impact computer simulations were conducted, using CTH, of various impact events, that identified certain modes of response, including simple metallic target cratering, perforations and delamination effects of coatings
Dimensional scaling for impact cratering and perforation
POD Associates have revisited the issue of generic scaling laws able to adequately predict (within better than 20 percent) cratering in semi-infinite targets and perforations through finite thickness targets. The approach used was to apply physical logic for hydrodynamics in a consistent manner able to account for chunky-body impacts such that the only variables needed are those directly related to known material properties for both the impactor and target. The analyses were compared and verified versus CTH hydrodynamic code calculations and existing data. Comparisons with previous scaling laws were also performed to identify which (if any) were good for generic purposes. This paper is a short synopsis of the full report available through the NASA Langley Research Center, LDEF Science Office
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