Physics of Granular Flows

Title

Memory of plastic fluid and its application to control pattern formation of dessication cracks

Abstract

When the mixture of powder particles and water has plasticity, it can remember the direction of the mechanical forces applied to it. For example, the plastic fluid can remember the direction of horizontal vibration and the direction of the flow motion. The memory inside the plastic fluid is hard to be detected directly, but we find that the memory inside it can be visualized as a morphology of dessication crack patterns which appear in the drying process. When the plastic fluid remembers the direction of the horizontal vibration, the dessication cracks run in the direction perpendicular to the direction of the initial horizontal vibration, while when the plastic fluid remembers the direction of the flow motion, the dessication cracks run in the direction parallel to the direction of the flow motion. Thus, using memory of horizontal vibration and/or flow, we can manage to produce various crack patterns, such as cellular lamellar, radial, ring, spiral and so on [1].
Recently we have vibrated the plastic fluid vertically and found that the pattern of Faraday waves can control not only the direction but also the position of dessication crack formation. Since the Faraday waves produce localized horizontal vibration at their node positions, we can imprint the morphology of Faraday waves into plastic fluid so as to enhance crack formation at the node positions. This method makes it possible to produce lattice-like structure of dessication cracks, which was impossible under the horizontal vibration and flow motion [2].

[1] Akio NAKAHARA and Yousuke MATSUO, "Transition in the pattern of cracks resulting from memory effects in paste", Phys. Rev. E, 74 (2006) 045102(R).
[2] Hiroshi NAKAYAMA, Yousuke MATSUO, OOSHIDA Takeshi and Akio NAKAHARA, "Position control of desiccation cracks by memory effect and Faraday waves", European Physical Journal E 36 (2013) 1.