Wave tailoring in elastic and elastoplastic granular systems

contact mechanics;dynamics;wave tailoring;wave propagation;impact;Granular Media

Pal, Raj Kumar

关键词: contact mechanics;    dynamics;    wave tailoring;    wave propagation;    impact;    Granular Media;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/78292/Pal_Rajkumar12.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This dissertation studies wave propagation in granular media with the objectiveof developing stress wave tailoring applications. Two mechanisms forwave tailoring are investigated: the first part focuses on energy dissipationin elasto-plastic granules and the second studies tunable wave propagationin elastic granular lattices. We start by developing a unified contact law forelasto-plastic granules of distinct sizes and material properties using quasistaticfinite element simulations. Extensive numerical studies are then conductedon the dynamics of elastic and elasto-plastic granular chains under awide range of loading conditions and models are developed for predicting thekey quantities. Compared to their elastic counterparts, elasto-plastic chainsexhibited distinct features like rapid decay of waves, formation and mergingof wave trains, yielding of contact points, etc. Then we quantify key impactproperties of 3D granular packings and compare with 3D continuum media.Scaling laws for dissipation are derived from first principles and verifiednumerically for both the media.In the second part of this dissertation, we develop systems for tunablewave propagation by exploiting the intrinsic nonlinearity of Hertzian contactin elastic granular lattices. We design a granular lattice of spheres packed ina cylindrical tube whose response can be varied from near solitary waves torapidly decaying waves by applying external precompression. The designs aredemonstrated using numerical simulations and the trends are explained by anasymptotic analysis. We also designed energy filters and band gap systemstunable by external control using lattices of spheres and cylinders subjectedto impact and harmonic loadings. Finally, we introduce the concept of wavetailoring by altering the network topology in granular lattices. The designsare demonstrated using a combination of modeling, numerical simulationsand experiments. Good agreement is obtained between them, illustratingthe feasibility of our designs for practical applications.