Cumulative energy analysis of thermally-induced surface wrinkling of heterogeneously multilayered thin films

Polymer/metal multilayers are thermally treated to generate surface wrinkles, then interpreted with cumulative energy balance analysis to reflect the individual elastic contribution of each constituent layer.

Comparative investigation of strength and plastic instability in Cu/Au and Cu/Cr multilayers by indentation

The mechanical response to indentation (including nano- and microindentation) has been investigated in Cu/Au and Cu/Cr multilayers with respective layer thickness ratios of 1:1 and 2:1, and individual layer thickness ranging from nanometer to submicrometer scale. It was found that the Cu/Cr multilayer has higher strength than the Cu/Au multilayer, although both multilayers have close Hall–Petch slope. Examination of indentation-induced deformation behavior shows that the Cu/Cr multilayer exhibits higher resistance to plastic deformation instability than the Cu/Au multilayer. Theoretical analysis indicates that the significant difference in mechanical response originates from the constituent layer configuration and interface structures, which impose distinguishing confining effect on dislocation activity.

The Optical Properties of Plasma-Deposited SiO2 and Si3N4 Bragg Reflectors in the Spectral Range from 1.8 to 3.0 eV

ABSTRACTWe have prepared 19-layer Si3N4:SiO2/…‥Si3N4:SiO2/Si3N4 (HL/HL/…HL/H), Bragg reflectors by remote plasma-enhanced chemical-vapor deposition, and have adjusted the constituent layer thicknesses to generate highly reflecting films over the entire visible spectrum from approximately 1.8 eV (∼690 nm) to 3.0 eV (∼410 nm). Peak values of the reflectance, in spectral bands with half-widths of ∼0.4 to 0.5 eV, are in the range of 96 to 98 %. The spectral response functions of these stacks exhibit departures from the optical behavior as calculated for exactly periodic structures with λ/4 layer thicknesses, and can be accounted for by taking into account: i) dispersion and absorption in the optical properties of the constituent layers; and ii) departures from the idealized and constant layer thicknessses.

Anisotropy effects in P-wave and SH-wave stacking velocities contain information on lithology

Depths calculated from S-wave stacking velocities and event times almost always exceed actual depths, sometimes by as much as 25 percent. In contrast, depths from corresponding P-wave information are often within 10 percent of actual depths. Discrepancies in depths calculated from P- and S-wave data are attributed to velocity anisotropy, a property of sedimentary rocks that noticeably affects S-wave moveout curves but leaves the P-wave relatively unaffected. Two careful studies show that discrepancies in depths, and hence in constituent layer thicknesses, correlate with lithology. Discrepancies ranged from an average of 13 percent (Midland basin) to greater than 40 percent (Paloma field) in shales, but were within expected errors in massive sandstones or carbonates. Hence anisotropy effects are indicators of lithology. Analysis of seismic data involved determining interval velocities from stacking velocities, calculating layer thicknesses, and then comparing layer thicknesses from S-wave data with thicknesses from P-wave data. When the S-wave thicknesses were significantly greater than the P-wave (i.e., outside the range of expected errors), I concluded the layer was anisotropic. I illustrate the technique with data from the Paloma field project of the Conoco Shear Wave Group Shoot.

Analytical excavation

Antiquity in 1957, in the midst of an ‘Evolution Number’, published a bold article by Professor Richard Atkinson on ‘Worms and weathering’. Often quoted since, but all too little absorbed, its message at the time was clear: ‘All of us recognize . . . that a site consists of a sequence of deposits, some formed deliberately and usually rapidly by man, and others more slowly by nature; and that some of the processes of formation, such as erosion and filling by the plough, are still continuing today. But there seems to be a widespread assumption (though it is difficult to be sure of this, since such things are seldom discussed) that once a constituent layer of a site has been formed, and sealed by another layer above it, it becomes immediately fossilized . . .’ Professor Atkinson spoke of his own post-Darwinian observations as ‘shots in the dark’, which ‘may not always be very accurate; but at least they serve to wake sleepers from their beds’.

Microstructure Theory for a Composite Beam

A continuum model with microstructure is constructed for laminated beams. In deriving equations, each constituent layer is considered as a Timoshenko beam. With a certain kinematical assumption regarding the deformations of the composite beam the kinetic and strain energies, as well as the variation of the work done by external forces, are computed. The energy and work expressions are “smoothed out” by a smoothing operation, thus transforming the laminated structuring into microstructure of a macro-homogeneous beam. Subsequent application of Hamilton’s principle yields the equations of motion and the boundary conditions. The equations thus obtained are employed to investigate free flexural waves in a composite beam. It is found that the dispersion curves according to the present theory agree very well with the curves obtained according to an exact analysis. Results according to the effective modulus theory are presented for comparison. Two simplified versions of the microstructure beam theory are also developed and discussed.