Abstract
An EQ-4B Global Hawk, one of the United States’ most advanced and expensive unmanned aerial vehicles, lost stability and crashed in 2011 because a single screw loosened. In 2016, a Union Pacific train derailed in Mosier, Oregon due to a single loose bolt, releasing 42,000 gallons of crude oil into the local environment. These two events (and many others) highlight our lack of knowledge pertaining to the long-term evolution of nonlinearities and their effect on the structure’s health and dynamics. This talk will cover recent progress towards understanding the dynamics of strongly nonlinear structures through system identification and physics-based reduced order modeling. This necessitates the synergistic implementation of diverse theoretical, computational, and experimental techniques, e.g., nonlinear normal modes, wavelet transforms, and experimental modal analysis. The first portion introduces a new energy-based methodology for identifying the dynamics of strongly nonlinear structures directly from experimental measurements. The methodology is applied to identify mathematical models for Duffing oscillators with hardening and softening-hardening nonlinearities. Second, we introduce a physics-based reduced-order model for the dynamics of bolted joint loosening with an application to an axially aligned threaded joint undergoing shock excitation. The final portion presents a novel two-dimensional nonlinear vibration absorber designed to mitigate motion in next-generation commercial aircraft with ultra-high-aspect-ratio wings.
About the Speaker
Keegan J. Moore is an Associate Professor in Aerospace Engineering at the Georgia Institute of Technology where he leads the Moore Dynamics and Analytics Laboratory (MoDAL). He received his Ph.D. from the University of Illinois in 2018 and his B.Sc. from the University of Akron in 2014. He is an expert in nonlinear dynamics and vibrations and his research lies at intersection of theory, simulation, and measurements. His recent work focuses on novel system identification methods, non-reciprocity and energy guiding in nonlinear structures, the mechanics of loosening of bolts, autonomous vibration testing, and autonomous model updating. He is the recipient of the 2022 AFOSR Young Investigator Program Award and a 2023 NSF CAREER Award.
Host: Professor Alex Vakakis