Rotating systems are fundamental to modern technology, yet traditionally, rotordynamics has focused primarily on steady-state operation, treating transient dynamics as operational challenges to be minimized. This thesis challenges this paradigm by demonstrating that unsteady rotation, specifically controlled angular acceleration, can serve as a programmable mechanism for remote, contact-free actuation of bistable elastic beams. By employing precision experiments using custom-built rotating platforms, automated high-throughput testing protocols, and reduced-order models, we demonstrate the potential of unsteady rotations by investigating buckling instabilities of slender structures under rotation.
First, through experiments on cantilevered and pre-arched beams, we demonstrate that the Euler force, a non-conservative fictitious force proportional to angular acceleration, can tune the buckling threshold, select the buckling direction, and drive snap-through transitions. A reduced-order model based on the Euler elastic formulation provides quantitative predictions in excellent agreement with experimental observations.
Second, we develop a high-throughput methodology that enables the parallel testing of multiple specimens under programmable inertial loadings. By prescribing harmonic angular velocity profiles, we systematically explore the two-dimensional phase space of angular velocity and acceleration. Over 23,000 experiments across 65 distinct configurations construct comprehensive stability maps. We find that the interplay between multiple parameters (tilt angle, pre-compression, clamp angles) shapes the stability boundaries. We demonstrate how asymmetric clamps exhibit the richest dynamics by featuring snap-through inversion pathways that depend on the initial state and loading history.
Finally, we demonstrate independent control of multiple bistable elements on a single rotating platform. By rationally designing loading trajectories in the phase space of angular velocity and acceleration that exploit intersecting stability boundaries, we achieve selective actuation of individual beams. We experimentally demonstrate this strategy using arrays of up to five mechanical bits, which encode all uppercase letters in ASCII representation. This work establishes a framework for bistable arrays with access to individual bits through a single global drive, providing a foundation for multi-bit mechanical memory.
