Mesoscopic Nonlinear Elastic Modulus of Thermal Barrier Coatings Determined by Cylindrical Punch Indentation

Cylindrical punch indentations are performed to determine the effective modulus of a plasma-sprayed ZrO₂–8 wt% Y₂O₃ thermal barrier coating (TBC) as a function of coating depth. Cylindrical punch indentations offer significant advantages over pointed (Vickers, Berkovich, or Knoop) indentations for materials that do not exhibit linear elastic behavior. Cyclic loading with a cylindrical punch clearly shows the TBCs to exhibit nonlinear elastic behavior with significant hysteresis that is related to the compaction and internal sliding within the plasma-spray splat microstructure. Also, the effect of a high-heat-flux laser treatment is shown to produce a gradient both in the effective TBC modulus and degree of loading/unloading hysteresis with depth.     

Effects of cutting conditions on drilling of aluminum 380

The major purpose of this project was to determine the effects of cutting conditions on drilling of aluminum alloy 380. Measurements of tool wear and surface finish were taken for two cutting speeds and feed rates, respectively. In each of the four tests, a high-helix, high-speed steel drill, 1/4 in. (6.35 mm) in diameter, was used to produce 460 holes 1.00 in. (25.4 mm) deep. The speeds used were 195 and 390 ftJmin (99 and 198 cmJs), and the feeds were 0.016 and 0.032 in.Jrev (0.406 and 0.812 mmJrev). Cutting speed had a greater influence on tool wear than feed rate. However, mean surface roughness increased approximately the same amount when the speed was doubled, as it did when the feed rate was doubled.     

Traumatic incarceration of the small bowel: case report

While bowel injuries associated with blunt abdominal trauma are a well recognized entity, entrapment of bowel between vertebral bodies has seldom been described. The unusual case of traumatic jejunal incarceration between two lumbar vertebrae is presented.     

Depth-penetrating temperature measurements of thermal barrier coatings incorporating thermographic phosphors

Thermographic phosphors have been previously demonstrated to provide effective non-contact, emissivity-independent surface temperature measurements. Due to the translucent nature of thermal barrier coatings (TBCs), thermographic-phosphor-based temperature measurements can be extended beyond the surface to provide depth-selective temperature measurements by incorporating the thermographic phosphor layer at the depth where the temperature measurement is desired. In this paper, thermographic phosphor (Y₂O₃:Eu) fluorescence decay time measurements are demonstrated to provide through-the-coating-thickness temperature readings up to 1100 °C with the phosphor layer residing beneath a 100-μm-thick TBC (plasmasprayed 8 wt.% yttria-stabilized zirconia). With an appropriately chosen excitation wavelength and detection configuration, it is shown that sufficient phosphor emission is generated to provide effective temperature measurements, despite the attenuation of both the excitation and emission intensities by the overlying TBC. This depth-penetrating temperature measurement capability should prove particularly useful for TBC diagnostics where a large thermal gradient is typically present across the TBC thickness. The fluorescence decay from the Y₂O₃:Eu layer exhibited both an initial short-term exponential rise and a longer-term exponential decay. The rise time constant was demonstrated to provide better temperature indication below 500 °C while the decay time constant was a better indicator at higher temperatures.     

The infrared properties of magnetron-sputtered diamond-like thin films

We have measured the infrared reflectance, R, and the transmittance, T, of several amorphous and diamond-like carbon films deposited on GaAs substrates by d.c. magnetron sputtering in an Argon atmosphere. The thickness, d, and the refractive index, n, were found from the fringes in the near-infrared reflectance, which were due to the interference in the film, using an appropriate model for the absorption. The mid-infrared absorption coefficient , obtained from 1-R-T, was then fitted to a model of the absorption involving both vibrations and electronic transitions, using d and n. The electronic absorption was found to decrease with increasing pressure, along with an increase in the intensity of the hydrogen vibrational features. We associate the transparency with the presence of hydrogen and present support for this view by measuring a film in which hydrogen was deliberately introduced.     

A study of Cu(I)‐ethylene complexation for olefin–paraffin separation

The current cryogenic distillation technology used for olefin–paraffin separation incurs extensive capital and operating costs. An alternative olefin–paraffin separation process, based on reactive absorption, could yield significant cost reductions. The research efforts described herein explored the structural characteristics of an NMP‐CuCl‐aniline absorption solution with ethylene to aid future development of olefin–paraffin separation systems. Solution IR and ¹H NMR spectroscopy suggested weak and labile Cu(I)‐ethylene and Cu(I)‐aniline coordination, which point to the coexistence of multiple structures in solution. Experiments also revealed solvent‐dependent and temperature‐dependent coordination. The agreement of the collected spectral data with literature implied single ethylene coordination, whereas the Cl^? ion likely remained coordinated with Cu(I). Solvent interference prohibited detailed investigation of IR spectra, but ¹H NMR spectroscopy showed more promise as an analytical technique for the NMP‐CuCl‐aniline‐ethylene system. Finally, a tradeoff appears to exist between ethylene capacity and complex stability, and thus, an optimal ligand must be found that balances these two competing needs. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Auger and ellipsometric studies of ultra-thin PbO growth on lead

The interaction of oxygen with initially-clean lead surfaces was studied using Auger electron spectroscopy to determine the oxygen uptake and ellipsometric measurements to monitor the resultant oxide fila thickness. The results from both techniques were in very close agreement and indicated that a true oxidation process was operative over the pressure range investigated (5 × 10^?8 to 5 × 10^?6 Torr O₂) at room temperature. The thickness of the growing oxide was closely proportional to the oxygen exposure (i.e., the pressure-time product) until a limiting value of 6.3 ± 0.2Å was reached, regardless of pressure. The refractive index of the film was 2.8 at gl = 5461Å, characteristic of the orthorhombic PbO crystal structure. The oxidation apparently proceeds via a place exchange mechanism wherein the activation energy barrier is markedly lowered by image force effects until a critical thickness is reached, dependent on the Pb-O single bond energy; from the dissociation energy of PbO and the atomic jump distance in orthorhombic PbO, this thickness was estimated as 6.5Å in good agreement with the experimental value. Analysis on the basis of chem-isorption did not yield satisfactory agreement.     

Waveforn Analysis of Doppler Ultrasound Signals by a Microcomputer

We discuss the algorithms used in the analysis of pulsed Doppler blood velocity (BV) signals. The discussion mainly concerns the method used for removing artifact from the BVsignal. Thisselection procedure considerably reduces the variability of the calculated waveform characteristics. As an example, two methods for the calculation of cardiac output from the BV signal were compared and one was found to be considerably superior. The approach used here is fairly general and can be used in other situations involving almost periodic signals.