An elastic-plastic asperity model for analyzing the contact of rough surfaces is presented. The model is based on volume conservation of an asperity control volume during plastic deformation. Numerical results obtained from this model are compared with other existing models that are either purely elastic or purely plastic. It is shown that these models are limiting cases of the more general elastic-plastic model presented here. Some of the results obtained deviate appreciably from previous analyses which do not consider asperity volume conservation.

The elastostatic problem of two materially dissimilar wedges of arbitrary angles that are bonded together along a common edge and subjected to surface tractions on the boundary of the configuration is treated. Emphasis is placed on the investigation of the dependence of the order of the singularity in the stress field at the apex on the wedge angles and material constants. Numerical results for several special wedge geometries are included for all physically relevant material combinations. In particular the families of (a) equal angle wedges, (b) composite half planes, (c) composite full-planes, as well as the single geometry of a (d) half-plane bonded to a quarter-plane, are studied in detail.

The commercialization of nanoscale devices requires the development of high-throughput nanofabrication technologies that allow frequent design changes. Maskless nanolithography, including electron-beam and scanning-probe lithography, offers the desired flexibility but is limited by low throughput. Here, we report a new low-cost, high-throughput approach to maskless nanolithography that uses an array of plasmonic lenses that 'flies' above the surface to be patterned, concentrating short-wavelength surface plasmons into sub-100 nm spots. However, these nanoscale spots are only formed in the near field, which makes it very difficult to scan the array above the surface at high speed. To overcome this problem we have designed a self-spacing air bearing that can fly the array just 20 nm above a disk that is spinning at speeds of between 4 and 12 m s(-1), and have experimentally demonstrated patterning with a linewidth of 80 nm. This low-cost nanofabrication scheme has the potential to achieve throughputs that are two to five orders of magnitude higher than other maskless techniques.

This paper presents experimental observations and a theoretical analysis of the operation of drop-on-demand piezoelectric ink jet devices. By studying experimentally the dependence of several operating characteristics on the length of the cavity in the nozzle of an ink jet device, we have gained insight into the physical phenomena underlying the operation of such a device. It is concluded that drop-on-demand ink jet phenomena are related to the propagation and reflection of acoustic waves within the ink jet cavity. A simple analysis is carried out on the basis of linear acoustics which is in good agreement with the experimental observations.

The plane-strain and generalized plane stress problems of two materially dissimilar orthogonal elastic wedges, which are bonded together on one of their faces while arbitrary normal and shearing tractions are prescribed on their remaining faces, are treated within the theory of classical elastostatics. The asymptotic behavior of the solution in the vicinity of the intersection of the bonded and loaded planes is investigated. The stress fields are found to be singular there with singularities of the type r−α, where α depends on the ratio of the two shear moduli and on the two Poisson’s ratios. This dependence is shown graphically for physically relevant values of the elastic constants. The largest value of α for the range of constants considered is 0.311 and occurs when one material is rigid and the other is incompressible.