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Title:Wave tailoring in elastic and elastoplastic granular systems
Author(s):Pal, Raj Kumar
Director of Research:Geubelle, Philippe H.
Doctoral Committee Chair(s):Vakakis, Alexander F.
Doctoral Committee Member(s):Lambros, John; Ostoja-Starzewski, Martin
Department / Program:Mechanical Sci & Engineering
Discipline:Theoretical & Applied Mechans
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):contact mechanics
wave tailoring
wave propagation
Granular Media
Abstract:This dissertation studies wave propagation in granular media with the objective of developing stress wave tailoring applications. Two mechanisms for wave tailoring are investigated: the first part focuses on energy dissipation in elasto-plastic granules and the second studies tunable wave propagation in elastic granular lattices. We start by developing a unified contact law for elasto-plastic granules of distinct sizes and material properties using quasistatic finite element simulations. Extensive numerical studies are then conducted on the dynamics of elastic and elasto-plastic granular chains under a wide range of loading conditions and models are developed for predicting the key quantities. Compared to their elastic counterparts, elasto-plastic chains exhibited distinct features like rapid decay of waves, formation and merging of wave trains, yielding of contact points, etc. Then we quantify key impact properties of 3D granular packings and compare with 3D continuum media. Scaling laws for dissipation are derived from first principles and verified numerically for both the media. In the second part of this dissertation, we develop systems for tunable wave propagation by exploiting the intrinsic nonlinearity of Hertzian contact in elastic granular lattices. We design a granular lattice of spheres packed in a cylindrical tube whose response can be varied from near solitary waves to rapidly decaying waves by applying external precompression. The designs are demonstrated using numerical simulations and the trends are explained by an asymptotic analysis. We also designed energy filters and band gap systems tunable by external control using lattices of spheres and cylinders subjected to impact and harmonic loadings. Finally, we introduce the concept of wave tailoring by altering the network topology in granular lattices. The designs are demonstrated using a combination of modeling, numerical simulations and experiments. Good agreement is obtained between them, illustrating the feasibility of our designs for practical applications.
Issue Date:2015-01-13
Rights Information:Copyright 2015 Raj Kumar Pal
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015

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