Rowland M. Cannon

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The role of grain bridging in affecting the initial rising portion of the R-curve and the transient, non-steady-state behavior of short cracks during (cyclic) fatigue-crack propagation has been quantitatively examined in a 99.5% pure alumina. Fatigue-crack growth properties for both long and short (⌬a f < 2 mm) cracks emanating from machined notches (root(More)
Thick-film resistors are electrical composites containing ultrafine particles of ruthenate conductor (Pb,Ru,O, in the present materials) distributed in a highly modified silicate glass. We show that conductor particles remain flocced in the absence of any applied or capillary pressures, but are separated at equilibrium by a nanometer-thick film of glass.(More)
A thermodynamic diffuse interface analysis predicts that grain boundary transitions in solute absorption are coupled to localized structural order-disorder transitions. An example calculation of a planar grain boundary using a symmetric binary alloy shows that first-order boundary transitions can be predicted as a function of the crystallographic grain(More)
Abnormal grain growth without strong anisotropy or faceting of the grains has been observed in high-purity yttria-doped alumina specimens, often starting at the surface and spreading right through the bulk at higher sintering temperatures. This appears to occur because of an interaction between Si contamination from sintering and the yttria doping; no such(More)
The optimum direction of in-plane continuous crack advance in functionally graded materials (FGMs) is discussed. The FGM is modeled using ®nite element analysis as a linear elastic material with spatially varying YoungÕs modulus. The kink direction was determined as the angle at which either the energy release is maximized …G max † or at which the kink tip(More)
The role of moisture in affecting both intrinsic and extrinsic aspects of the fracture and fatigue-crack growth resistance of a polycrystalline alumina (99.5% pure, 25 lm grain size) has been examined in both moist and dry environments at ambient temperature. The intrinsic (crack-tip) toughness, deduced from measured crack-opening profiles, is found to be(More)
Stable, nanometer-thick films are observed to form at the {1120} facets of Bi(2)O(3)-doped ZnO in several bulk-phase stability fields. Electron microscopy shows these surficial films to exhibit some degree of partial order in quenched samples. The equilibrium film thickness, corresponding to the Gibbs excess solute, decreases monotonically with decreasing(More)
This paper describes research on the stress-corrosion crack growth (SCCG) behavior of a new series of bioactive glasses designed to fabricate coatings on Ti and Co-Cr-based implant alloys. These glasses should provide improved implant fixation between implant and exhibit good mechanical stability in vivo. It is then important to develop an understanding of(More)
Environmentally dependent subcritical crack growth, or stress-corrosion cracking, along ceramic-metal interfaces is studied for the silica glass-copper system. Tests were conducted in various gaseous and liquid environments in order to determine their relative effects on stress-corrosion cracking and to gain some insight into the mechanisms that control(More)
The mechanical behavior of four rare earth (RE)-Mg-doped Si 3 N 4 ceramics (RE 5 La, Lu, Y, Yb) with varying grain-boundary adhesion has been examined with emphasis on materials containing La and Lu (which represent the extremes of RE ionic radius). Fracture-resistance curves (R-curves) for all ceramics rose very steeply initially, giving them exceptional(More)