Gas-Mediated Impact Dynamics in Fine-Grained Granular Materials

Gas-mediated impact dynamics in fine-grained granular materials.

Noncohesive granular media exhibit complex responses to sudden impact that often differ from those of ordinary solids and liquids. We investigate how this response is mediated by the presence of interstitial gas between the grains. Using high-speed x-ray radiography we track the motion of a steel sphere through the interior of a bed of fine, loose granular material. We find a crossover from nea...

Spectroscopy of Fine - Grained Planetary Materials

Introduction: Dust is the basic building block of all larger bodies formed in the Solar System: planets, their satellites, comets and asteroids. Some of these dust grains have survived 4.56 Gyr of processing, and occur as interplanetary dust particles (IDPs), GEMS (Glass with embedded sulphides) within IDPs and presolar grains in meteorites. Primitive meteorites can also be regarded as aggregat...

Coarse-grained dynamics of the freely cooling granular gas in one dimension.

We study the dynamics and structure of clusters in the inhomogeneous clustered regime of a freely cooling granular gas of point particles in one dimension. The coefficient of restitution is modeled as r(0)<1 or 1, depending on whether the relative speed is greater or smaller than a velocity scale δ. The effective fragmentation rate of a cluster is shown to rise sharply beyond a δ-dependent time...

Dynamics of levitated granular materials

Intermittent ‘self-locking’ of Grain Growth in Fine-grained Materials

Grain boundary motion may be accompanied with vacancy generation [1–4]. A typical case where a moving grain boundary produces vacancies is in primary recrystallisation, when the growth of a recrystallised grain at the cost of a grain with a large dislocation density involves release of excess free volume. Vacancies are also generated during grain growth, when the total volume of the grain bound...