Nonlinear Periodic Phononic Structures and Granular Crystals

We develop a framework for wave tailoring by altering the lattice network topology of a granular crystal consisting of spherical granules in contact. The lattice topology can alternate between two stable configurations, with the spherical granules of the lattice held in stable equilibrium in each configuration by gravity. Under impact, the first configuration results in a wave with rapidly decaying amplitude as it propagates along a primary chain, while the second configuration results in a solitary wave propagating along the primary chain with no decay. The mechanism to achieve such tunability is by having energy diverted to the granules adjacent to the primary chain in the first case but not the second. The tunable design of the proposed network is validated using both numerical simulations and experiments. In terms of potential applications, the proposed bistable lattice network can be viewed either as a wave attenuator or as a device that allows higher amplitude wave propagation in one direction than in the opposite direction. The lattice is analogous to a crystal phase transformation due to the change in atomic configurations, leading to the change in properties at the macroscale.

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Microporosity of BIF hosted massive hematite ore, Iron Quadrangle, Brazil

Anais da Academia Brasileira de Ciências ◽

10.1590/s0001-37652002000100008 ◽

2002 ◽

Vol 74 (1) ◽

pp. 113-126 ◽

Cited By ~ 7

Author(s):

CÉSAR A.C. VARAJÃO ◽

ARY BRUAND ◽

ERICK R. RAMANAIDOU ◽

ROBERT J. GILKES

Keyword(s):

Direct Reduction ◽

Total Porosity ◽

Nitrogen Adsorption ◽

Open Pit ◽

Granular Crystals ◽

Iron Quadrangle ◽

Hematite Ore ◽

Electron Microscopes ◽

Main Component ◽

Scanning Electron Microscopes

Massive hematite ore (MHO) is a special high-grade iron ore, used as lump ore in the process of obtaining direct reduction iron (DRI). The influence of porosity on the reducibility of MHO from the Capitão do Mato Mine (Iron Quadrangle, Brazil) was investigated using optical and scanning electron microscopes on drill core and open pit samples. Hematite is the main component of the samples and occurs as granular crystals (10 mum), microplates (1 mum) and euhedral martite (10 to 30 mum). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (Å to 1 mum) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (Å to 5 mum) related to euhedral martite crystals, are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 11%, whereas unweathered samples have a porosity less than 2.5%. Reducibility is strongly enhanced by porosity, but inhibited by structure (bedding).

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