Browsing Complex Rheology and Biomechanics Lab (CRAB LAB) by Type "Text"
Now showing items 1-20 of 37
-
Absence of inelastic collapse in a realistic three ball model
(Georgia Institute of TechnologyAmerican Physical Society, 1998-04)Inelastic collapse, the process in which a number of partially inelastic balls dissipate their energy through an infinite number of collisions in a finite amount of time, is studied for three balls on an infinite line and ... -
Biophysically inspired development of a sand-swimming robot
(Georgia Institute of TechnologyMIT Press, 2011)Previous study of a sand-swimming lizard, the sandfish, Scincus scincus, revealed that the animal swims within granular media at speeds up to 0:4 body-lengths/cycle using body undulation (approximately a single period ... -
Colloquium: Biophysical principles of undulatory self-propulsion in granular media
(Georgia Institute of Technology, 2014)Biological locomotion, movement within environments through self-deformation, encompasses a range of time and length scales in an organism. These include the electrophysiology of the nervous system, the dynamics of muscle ... -
Comparative studies reveal principles of movement on and within granular media
(Georgia Institute of TechnologySpringer Verlag, 2010-06)Terrestrial locomotion can take place on complex substrates such as leaf litter, debris, and soil that flow or solidify in response to stress. While principles of movement in air and water are revealed through study of the ... -
Continuum-type stability balloon in oscillated granular layers
(Georgia Institute of TechnologyAmerican Physical Society, 1998-08-17)The stability of convection rolls in a fluid heated from below is limited by secondary instabilities, including the skew-varicose and crossroll instabilities. We observe a stability boundary defined by these same instabilities ... -
Crucial role of sidewalls in velocity distributions in quasi-two-dimensional granular gases
(Georgia Institute of TechnologyAmerican Physical Society, 2004-10-19)Our experiments and three-dimensional molecular dynamics simulations of particles confined to a vertical monolayer by closely spaced frictional walls (sidewalls) yield velocity distributions with non-Gaussian tails and a ... -
Design of a Bio-inspired Dynamical Vertical Climbing Robot
(Georgia Institute of TechnologyMIT Press, 2008)This paper reviews a template for dynamical climbing originating in biology, explores its stability properties in a numerical model, and presents emperical data from a physical prototype as evidence of the feasibility of ... -
Drag induced lift in granular media
(Georgia Institute of TechnologyAmerican Physical Society, 2011-01-14)Laboratory experiments and numerical simulation reveal that a submerged intruder dragged horizontally at a constant velocity within a granular medium experiences a lift force whose sign and magnitude depend on the intruder ... -
Dynamics of drag and force distributions for projectile impact in a granular medium
(Georgia Institute of TechnologyAmerican Physical Society, 2004-05-14)Our experiments and molecular dynamics simulations on a projectile penetrating a two-dimensional granular medium reveal that the mean deceleration of the projectile is constant and proportional to the impact velocity. Thus, ... -
The Effect of limb kinematics on the speed of a legged robot on granular media
(Georgia Institute of TechnologySociety for Experimental Mechanics, 2010-04-22)Achieving effective locomotion on diverse terrestrial substrates can require subtle changes of limb kinematics. Biologically inspired legged robots (physical models of organisms) have shown impressive mobility on hard ... -
Effect of Volume Fraction on Granular Aavalanche Dynamics
(Georgia Institute of TechnologyAmerican Physical Society, 2014)We study the evolution and failure of a granular slope as a function of prepared volume fraction, φ0. We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45◦ angle while we monitor ... -
The Effectiveness of Resistive Force Theory in Granular Locomotion
(Georgia Institute of TechnologyAmerican Institute of Physics, 2014)Resistive force theory (RFT) is often used to analyze the movement of microscopic organisms swimming in fluids. In RFT, a body is partitioned into infinitesimal segments, each of which generates thrust and experiences ... -
Entangled granular media
(Georgia Institute of TechnologyAmerican Physical Society, 2012-05-17)We study the geometrically induced cohesion of ensembles of granular“u particles” that mechanically entangle through particle interpenetration. We vary the length-to-width ratio l/w of the u particles and form them into ... -
Force and flow at the onset of drag in plowed granular media
(Georgia Institute of TechnologyAmerican Physical Society, 2014)We study the transient drag force F[subscript D] on a localized intruder in a granular medium composed of spherical glass particles. A flat plate is translated horizontally from rest through the granular medium to observe ... -
Force and flow transition in plowed granular media
(Georgia Institute of TechnologyAmerican Physical Society, 2010-09-06)We use plate drag to study the response of granular media to localized forcing as a function of volume fractionϕ. A bifurcation in the force and flow occurs at the onset of dilatancy ϕ [subscript c]. Below ϕ [subscript ... -
Granular impact and the critical packing state
(Georgia Institute of TechnologyAmerican Physical Society, 2010-07-15)Impact dynamics during collisions of spheres with granular media reveal a pronounced and nontrivial dependence on volume fraction ϕ. Postimpact crater morphology identifies the critical packing state ϕcps, where sheared ... -
Integrating a Hierarchy of Simulation Tools for Legged Robot Locomotion
(Georgia Institute of TechnologyInstitute of Electrical and Electronics Engineers, 2008-09)We are interested in the development of a variety of legged robot platforms intended for operation in unstructured outdoor terrain. In such settings, the traditions of rational engineering design, driven by analytically ... -
Kink-induced transport and segregation in oscillated granular layers
(Georgia Institute of TechnologyAmerican Physical Society, 2003-09-26)We use experiments and molecular dynamics simulations of vertically oscillated granular layers to study horizontal particle segregation induced by a kink (a boundary between domains oscillating out of phase). Counterrotating ... -
Lattice dynamics and melting of a nonequilibrium pattern
(Georgia Institute of TechnologyAmerican Physical Society, 2003-03-14)We present a new description of nonequilibrium square patterns as a harmonically coupled crystal lattice. In a vertically oscillating granular layer, different transverse normal modes of the granular square-lattice pattern ... -
Lift-off dynamics in a simple jumping robot
(Georgia Institute of TechnologyAmerican Physical Society, 2012-10-26)We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but ...