This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
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Seed awns (Erodium and Pelargonium) bury themselves into ground for germination usinghygroscopic coiling and uncoilingmovements. Similarly,wormlizards (Amphisbaenia) create
tunnels for habitation by oscillating their heads along the long axis of the trunks. Inspired by
these burrowing strategies, this research aims to understand these mechanisms from a soil
mechanics perspective, investigate the factors influencing…
Seed awns (Erodium and Pelargonium) bury themselves into ground for germination usinghygroscopic coiling and uncoilingmovements. Similarly,wormlizards (Amphisbaenia) create
tunnels for habitation by oscillating their heads along the long axis of the trunks. Inspired by
these burrowing strategies, this research aims to understand these mechanisms from a soil
mechanics perspective, investigate the factors influencing penetration resistance, and develop
a self-burrowing technology for subterranean explorations. The rotational movements of
seed awns, specifically their coiling and uncoiling movements, were initially examined
using the Discrete Element Method (DEM) under shallow and dry conditions. The findings
suggest that rotation reduces penetration resistance by decreasing penetrator-particle contact
number and the force exerted, and by shifting the contact force away from vertical direction.
The effects of rotation were illustrated through the force chain network, displacement field,
and particle trajectories, supporting the "force chain breakage" hypothesis and challenging
the assumptions of previous analytical models. The factors reducing penetration resistance
were subsequently examined, both numerically and experimentally. The experimental results
link the reduction of horizontal penetration resistance to embedment depth and penetrator
geometry. Notably, both numerical and experimental results confirm that the reduction of
penetration resistance is determined by the relative slip velocity, not by the absolute values.
The reduction initially spikes sharply with the relative slip velocity, then increases at a slower
rate, leveling off at higher relative slip velocities. Additional findings revealed a minimal
impact of relative density, particle shape, and inertial number on penetration resistance
reduction. Conversely, interface friction angle appeared to increase the reduction, while
penetrator roundness and confining pressure decreased it. The investigation also extended
to the effect of rotational modes on the reduction of penetration resistance. Reductions
between cone-continuous rotation (CCR) and cone-oscillatory rotation (COR) cases were
i
comparable. However, whole-body-continuous rotation (WCR) yielded a higher reduction
under the same relative slip velocities. Interestingly, the amplitude of oscillation movement
demonstrated a negligible effect on the reduction. Lastly, a self-burrowing soft robot was
constructed based on these insights. Preliminary findings indicate that the robot can move
horizontally, leveraging a combination of extensioncontraction and rotational movements.
