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Wei, Z

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Wei

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Wei, Z

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2013 - 20153

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Author's Publications: search.filters.isAuthorOfPublication.244fa523-5002-4c97-93e9-be6acf49e54a

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Now showing 1 - 3 of 3
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    Studies in discrete and continuum mechanics
    (2014-06-06) Wei, Z; Mahadevan, Lakshminarayanan; Suo, Zhigang; Hutchinson, John; Aizenberg, Joanna
    We have used a combination of theory and computation to investigate collective aspects of discrete mechanical systems. The analysis involves considerations from geometry, elasticity and hydrodynamics. We have developed continuum theories to describe these systems, in the spirit of compressing information by mathematical abstraction from the discrete description.
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    Digital Instability of a Confined Elastic Meniscus
    (Proceedings of the National Academy of Sciences, 2013) Biggins, John S.; Saintyves, Baudouin; Wei, Z; Bouchaud, Elisabeth; Mahadevan, Lakshminarayanan
    Thin soft elastic layers serving as joints between relatively rigid bodies may function as sealants, thermal, electrical, or mechanical insulators, bearings, or adhesives. When such a joint is stressed, even though perfect adhesion is maintained, the exposed free meniscus in the thin elastic layer becomes unstable, leading to the formation of spatially periodic digits of air that invade the elastic layer, reminiscent of viscous fingering in a thin fluid layer. However, the elastic instability is reversible and rate-independent, disappearing when the joint is unstressed. We use theory, experiments, and numerical simulations to show that the transition to the digital state is sudden (first-order), the wavelength and amplitude of the fingers are proportional to the thickness of the elastic layer, and the required separation to trigger the instability is inversely proportional to the in-plane dimension of the layer. Our study reveals the energetic origin of this instability and has implications for the strength of polymeric adhesives; it also suggests a method for patterning thin films reversibly with any arrangement of localized fingers in a digital elastic memory, which we confirm experimentally.
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    Fluid-driven fingering instability of a confined elastic meniscus
    (IOP Publishing, 2015) Biggins, John S.; Wei, Z; Mahadevan, Lakshminarayanan
    When a fluid is pumped into a cavity in a confined elastic layer, at a critical pressure, destabilizing fingers of fluid invade the elastic solid along its meniscus (Saintyves B. et al., Phys. Rev. Lett., 111 (2013) 047801). These fingers occur without fracture or loss of adhesion and are reversible, disappearing when the pressure is decreased. We develop an asymptotic theory of pressurized highly elastic layers trapped between rigid bodies in both rectilinear and circular geometries, with predictions for the critical fluid pressure for fingering, and the finger wavelength. Our results are in good agreement with recent experimental observations of this elastic interfacial instability in a radial geometry. Our theory also shows that, perhaps surprisingly, this lateral-pressure–driven instability is analogous to a transverse-displacement–driven instability of the elastic layer. We verify these predictions by using non-linear finite-element simulations on the two systems which show that in both cases the fingering transition is first order (sudden) and hence has a region of bistability.