Meeting Abstract

P3-125   -   Lateral head movement reduces force required for penetration in damp granular media Edwards, CS*; Astley, HC; University of Akron; University of Akron cse18@uakron.edu

Locomotion through wet granular media requires an increased penetration force, but also provides the opportunity to create permanent or semi-permanent excavations to move through. Organisms display a variety of strategies to deal with these challenges. For example, Amphisbaenians are an often-limbless clade of burrowing squamates that use dorsoventral, lateral or a combination of head movements and forward penetration to move through soil. Here, a robophysical model was constructed to study the forces required for the penetration of a rigid intruder in damp granular media. The model includes a 3D-printed intruder with a moveable head, pushed by a hydraulic shaft powered by a stepper motor; forces are measured using a load cell located between the motor and hydraulic system. The head of the intruder is capable of lateral movement of variable frequency and amplitude. Following Sharpe et al. (2015), damp sand was prepared and deposited through a mesh screen to allow for a more homogenous deposition with a consistent compaction. The head was moved in a sweeping motion from side to side twice, after which the shaft was pushed a total of 34mm through the sand. Results indicate that the pre-clearance of wet granular media reduced the initial force required for penetration by 24%, but returned to a force requirement similar to that of an intruder with a stationary head after moving past the excavated area. When the head moved continuously throughout the experiment, the initial force reduction was similar (23%), while the energy reduction for the entire push was 24%. The mechanics of burrowing in wet granular media have been understudied, and this work addresses that knowledge gap. Moreover, the apparatus presented here will be useful in future studies of burrowing in both wet and dry granular media.