Scattering of Surface Acoustic Waves from an Elastic Plate Attached to a Half-Space with a Viscous Couplant

The results presented here are part of a study of the interaction between an electro-mechanical transducer plate element and wavelengths in the test structure that are comparable to the plate dimensions. The steady time-harmonic problem is reduced to a system of singular integral equations for determining the tractions generated at the interface between the plate and half-space where a thin viscous couplant is applied. This system is solved numerically for various values of couplant viscosity and incident wavelength. Graphical results for interface tractions and reflected power are presented

Application of cathodic arc deposited amorphous hard carbon films to the head/disk tribology

Amorphous hard carbon films deposited by filtered cathodic arc deposition exhibit very high hardness and elastic modulus, high mass density, low coefficient of friction, and the films are very smooth. All these properties are beneficial to applications of these films for the head/disk interface tribology. The properties of cathodic arc deposited amorphous carbon films are summarized, and they are compared to sputter deposited, hydrogenated (CH{sub x}), and nitrogenated (CN{sub x}) carbon films which are the present choice for hard disk and slider coatings. New developments in cathodic arc coaters are discussed which are of interest to the disk drive industry. Experiments on the nanotribology, mass density and hardness, corrosion behavior, and tribochemical behavior of cathodic arc films are reported. A number of applications of cathodic arc deposited films to hard disk and slider coatings are described. It is shown that their tribological performance is considerably better compared to CH{sub x} and CN{sub x} films

Some consequences of the inequality conditions in contact and crack problems

The importance of the inequalities and related side conditions that must be incorporated in contact and crack problems is emphasized and the ensuing consequences explored. An asymptotic analysis of the transitions from slip to separation, stick to slip, and stick to separation is carried out. The inequalities in contact problems make the contact pressure continuous for all levels of friction. They also make a direct transition from stick to separation impossible, unless the combination of materials is special. The inequalities in crack problems are less stringent, but they preclude certain singularities that appear to have flourished in the literature previously. On appuie sur l'importance d'inéquations et d'autres conditions auxiliaires qui doivent être comprises dans les problèmes de contact et de fissure, et on en explore les conséquences. On emploie une analyse asympotique sur les transitions entre les zones glissement-décollement, adhérence-glussement et adhérence-décollement. Il s'ensuit que la contrainte normale du contact doit être continue pour toutes les valeurs du frottement. De plus, la transition directe adhérence-décollement est impossible, à moin que la combinaison des matériaux ne soit exceptionelle. Les inéquations dans les problèmes de fissure sont moins fortes, mais elles sont cependant suffisantes pour empêcher l'existence de certaines singularités qui apparaissent souvent dans les études précedentes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42689/1/10659_2004_Article_BF00040981.pd

Inkjet Metrology: High-Accuracy Mass Measurements of Microdroplets Produced by a Drop-on-Demand Dispenser

We describe gravimetric methods for measuring the mass of droplets generated by a drop-on-demand (DOD) microdispenser. Droplets are deposited, either continuously at a known frequency or as a burst of known number, into a cylinder positioned on a submicrogram balance. Mass measurements are acquired precisely by computer, and results are corrected for evaporation. Capabilities are demonstrated using isobutyl alcohol droplets. For ejection rates greater than 100 Hz, the repeatability of droplet mass measurements was 0.2%, while the combined relative standard uncertainty (uc) was 0.9%. When bursts of droplets were dispensed, the limit of quantitation was 72 μg (1490 droplets) with uc = 1.0%. Individual droplet size in a burst was evaluated by high-speed videography. Diameters were consistent from the tenth droplet onward, and the mass of an individual droplet was best estimated by the average droplet mass with a combined uncertainty of about 1%. Diameters of the first several droplets were anomalous, but their contribution was accounted for when dispensing bursts. Above the limits of quantitation, the gravimetric methods provided statistically equivalent results and permit detailed study of operational factors that influence droplet mass during dispensing, including the development of reliable microassays and standard materials using DOD technologies

The problem of sharp notch in microstructured solids governed by dipolar gradient elasticity

In this paper, we deal with the asymptotic problem of a body of infinite extent with a notch (re-entrant corner) under remotely applied plane-strain or anti-plane shear loadings. The problem is formulated within the framework of the Toupin-Mindlin theory of dipolar gradient elasticity. This generalized continuum theory is appropriate to model the response of materials with microstructure. A linear version of the theory results by considering a linear isotropic expression for the strain-energy density that depends on strain-gradient terms, in addition to the standard strain terms appearing in classical elasticity. Through this formulation, a microstructural material constant is introduced, in addition to the standard Lamé constants . The faces of the notch are considered to be traction-free and a boundary-layer approach is followed. The boundary value problem is attacked with the asymptotic Knein-Williams technique. Our analysis leads to an eigenvalue problem, which, along with the restriction of a bounded strain energy, provides the asymptotic fields. The cases of a crack and a half-space are analyzed in detail as limit cases of the general notch (infinite wedge) problem. The results show significant departure from the predictions of the standard fracture mechanics