Academic literature on the topic 'Coble creep'

The first week of September mostly feels like summer. The air on the dry terrace bordering the beaver meadow is richly scented with pine. Purple aster, blue harebells, and tall, yellow black-eyed Susan still bloom. Fungi are more abundant on the forest floor, and the tiny, purplish berries of kinnikinnick are sweet to the taste. The air is warm in the sunshine, but strong winds hurry rain showers through at intervals. Patches of last year’s snow linger on the surrounding peaks, even as the first light snows have already fallen in the high country. Down in the beaver meadow, the leaves of aspen, willow, birch, and alder are starting to assume their autumn colors. Here and there a small patch of yellow or orange appears among the green. Blades of grass have a pale orange tint and the strawberry leaves have gone scarlet, even as white asters, purple thistles, and a few other flowers continue to bloom. The creek is noticeably lower, its cobble bed slick with rust-brown algae. Exposed cobble and sandbars have grown wider as the water has shrunk back from the edge of the willows, and the main channel is easy to cross on foot. The clear water is chillingly cold in both the main channel and the side channels. The smaller side channels no longer flow, and a drape of mud mixed with bits of plants covers the cobbles. Wood deposited a year ago has weathered to pale gray. The older, marginal beaver ponds have shrunk noticeably, and the water is lower in the main ponds, where tall sedges now lie bent on the top of the declining water surface. The beavers remain active: following fresh moose tracks, I come on a newly built beaver dam on a small side channel. By the third week of September, autumn has clearly arrived in the mountains. The air remains quite warm during the day, but nights of frost are swiftly bringing out the autumn colors. Whole stands of willows and aspen now glow golden or pumpkin-orange.

We present simulations of the dynamic response of radio frequency micro-electro-mechanical-systems (RF-MEMS) switches undergoing creep deformation. The model includes a microscale-informed Coble creep formulation incorporated in a beam model of an electrostatically actuated RF-MEMS switch, and it is solved using a Ritz-Galerkin based modal expansion. The resulting effects on the long-term device behavior as well as the implications of uncertainty in the device geometry and material parameters are studied. We find that the addition of creep to the beam model results in an undesired degradation

This paper examines a potential microscale mechanism that contributes to rate-dependent creep of Sn3.9Ag0.6Cu Pb-free solders. The experimentally measured transient and steady-state creep constitutive properties are first presented. Empirical constitutive models are derived, based on this data. Finally, a microstructural model, based on thermally activated dislocation detachment, is explored as a possible source of the creep behavior. This approach explicitly includes microstructural features such as grain size, particle size, particle spacing, etc. The model is calibrated by using the steady-

Burst rupture properties of Zircaloy-4 and Nb-Modified Zircaloy-4 are investigated at temperatures ranging from 638K to 843K by internal pressurization of closed-end tubing samples. Various pressurization levels were imposed and rupture times were noted. The data enabled an evaluation of Larson-Miller parameter and the present experimental results on Zircaloy-4 were in excellent agreement with those reported in the literature. The effect of 1% Nb addition to Zircaloy-4 was studied since these materials are now known to resist long-time corrosion in water reactors and are thus considered for hi