In this study the effects of surface texture on the fatigue life of a high-strength low-alloy steel were evaluated in terms of the apparent fatigue stress concentration. An abrasive waterjet was used to machine uniaxial dogbone fatigue specimens with specific surface quality from a rolled sheet of AISI 4130 CR steel. The surface texture resulting from machining was characterized using contact p...

We have designed, fabricated, and tested a new type of thermal shear-stress sensor. The sensor consists of a 2 m wide polysilicon thermistor (with a range of lengths, 80-200 m) on a 1.2 m thick silicon-nitride diaphragm, which is on top of a vacuum cavity 200 200 2 m in size. The vacuum cavity provides a good thermal isolation between the resistive element and the substrate; shear-stress sensit...

Controlled, uniform, peening has been used to impose precise cov onto mild steel plate specimens. This was achieved by using an the specimens under a single, precision-loaded, 2mm diameter studies have revealed a surprising relationship between percent surface residual stress. Stress increases almost linearly with low coverages but reaches a maximum at about 80% coverage. At 100% coverage the i...

We propose a model based on a Ginzburg-Landau approach to study a strain relief mechanism at a free interface of a nonhydrostatically stressed solid, commonly observed in thin-film growth. The evolving instability, known as the Grinfeld instability, is studied numerically in two and three dimensions. Inherent in the description is the proper treatment of nonlinearities. We find that these nonli...

We present a fully general derivation of the Laplace-Young formula and discuss the interplay between the intrinsic surface geometry and the extrinsic one ensuing from the immersion of the surface in the ordinary Euclidean three-dimensional space. We prove that the (reversible) work done in a general surface deformation can be expressed in terms of the surface stress tensor and the variation of ...

There are two major objectives to the present work. The first objective is to demonstrate that, in contrast to predictions from linear surface elastic theory, when nonlinear, finite deformation kinematics are considered, the residual surface stress does impact the resonant frequencies of silicon nanowires. The second objective of this work is to delineate, as a function of nanowire size, the re...

A canonical flow geometry was utilized for a fundamental study of the coupling between bulk flow and a Newtonian gas-liquid interface in the presence of an insoluble surfactant. We develop a Navier-Stokes numerical model of the flow in the deep-channel surface viscometer geometry, which consists of stationary inner and outer cylinders, a floor rotating at a constant angular velocity, and an int...

The fine-scale response of a subsurface stable stratified jet subject to the forcing of surface wind stress and surface cooling is investigated using direct numerical simulation. The initial velocity profile consists of a symmetric jet located below a surface layer driven by a constant wind stress. The initial density profile is well-mixed in the surface layer and linearly stratified in both up...

Accurate predictions of the sea state–dependent air–sea momentum flux require a thorough understanding of the wave boundary layer turbulence over surface waves. A set of momentum and energy equations is derived to formulate and analyze wave boundary layer turbulence. The equations are written in wavefollowing coordinates, and all variables are decomposed into horizontalmean, wave fluctuation, a...