2 research outputs found
Snapping of elastic strips with controlled ends
Snapping mechanisms are investigated for an elastic strip with ends imposed
to move and rotate in time. Attacking the problem analytically via Euler's
elastica and the second variation of the total potential energy, the number of
stable equilibrium configurations is disclosed by varying the kinematics of the
strip ends. This result leads to the definition of a `universal snap surface',
collecting the sets of critical boundary conditions for which the system snaps.
The elastic energy release at snapping is also investigated, providing useful
insights for the optimization of impulsive motion. The theoretical predictions
are finally validated through comparisons with experimental results and finite
element simulations, both fully confirming the reliability of the introduced
universal surface. The presented analysis may find applications in a wide range
of technological fields, as for instance energy harvesting and jumping robots
Configurational forces and nonlinear structural dynamics
Configurational, or Eshelby-like, forces are shown to strongly influence the
nonlinear dynamics of an elastic rod constrained with a frictionless sliding
sleeve at one end and with an attached mass at the other end. The
configurational force, generated at the sliding sleeve constraint and
proportional to the square of the bending moment realized there, has been so
far investigated only under quasi-static setting and is now confirmed (through
a variational argument) to be present within a dynamic framework. The deep
influence of configurational forces on the dynamics is shown both theoretically
(through the development of a dynamic nonlinear model in which the rod is
treated as a nonlinear spring, obeying the Euler elastica, with negligible
inertia) and experimentally (through a specifically designed experimental
set-up). During the nonlinear dynamics, the elastic rod may slip alternatively
in and out from the sliding sleeve, becoming a sort of nonlinear oscillator
displaying a motion eventually ending with the rod completely injected into or
completely ejected from the sleeve. The present results may find applications
in the dynamics of compliant and extensible devices, for instance, to guide the
movement of a retractable and flexible robot arm