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This paper investigates the shock-induced instability of the interfaces between gases and dense granular media with finite length via the coarse-grained compressible computational fluid dynamics–discrete parcel method. Despite generating a typical spike-bubble structure reminiscent of the Richtmyer–Meshkov instability (RMI), the shock-driven granular instability (SDGI) is governed by fundamentally different mechanisms. Unlike the RMI arising from baroclinic vorticity deposition on the interface, the SDGI is closely associated with the interfacial and bulk granular dynamics, which evolve with the transient coupling between particles and gases. Consequently, the SDGI follows a growth law distinctly different from that of the RMI, namely a semilinear slow regime followed by an exponentially expedited regime and a quadratic asymptotic regime. We further establish the instability criteria of the SDGI for granular media with infinite and finite lengths, which do not exist in the RMI. A scaling growth law of the SDGI for dense granular media with finite length is derived by normalizing the time with the rarefaction propagation time, which successfully collapses the data from cases with varying shock strength, particle column length and particle volume fraction and ought to hold for granular media with varying particle parameters. The effect of the initial perturbation magnitude can be…
In common language ductility refers to the ability to be deformed without losing toughness; pliable, but not brittle. Malleable means the ability to be hammered or pressed into shape without breaking or cracking. These properties a great interest in selecting material for building things.
Ductility and malleability are two aspects of the plasticity of solid materials. In metals ductility and malleability is very high due to their ability sustain large amounts of plastic deformations within the crystal structure. Platinum is the most ductile material and gold is the most malleable material.
Ductility is the ability of a solid material to undergo tensile stress. This property of solid material can be measured and describes the extent to which the solid material can be plastically deformed without fracture. It is often depicted by the ability of the solid to stretch into a wire when pulled at the ends.
The mechanical property of ductility is quantified by the fracture strain〖 ε〗_f, which is the strain the material fractures when increasing tensile stresses are applied along a single axis. The reduction of the area from the initial point to the fracture during the test can also be considered as a measure.