Session: VIB-04-01

Paper Number: 147648

147648 - Vibration Reduction of a Frame by Pendant Phononic Crystals 

Space structures, such as satellites, telescopes (e.g., Hubble, James Webb space telescopes), or the international space station (ISS) are all built on some type of frame structures. Many space structures fall into three classes; (1) automatically manufactured in space by special machinery, (2) deployable post launch, and (3) erected post launch from smaller strut and frame elements. The stiffnesses and losses in all three classes vary widely, and consequently so does their vibrational response to excitations. Vibrational excitations of space structures can come from forces imposed during manufacturing, unintended interaction with objects, solar heating, or gravitational forces. A major structural integrity problem is posed by the fact that these structures are in free vibration and thus will not be able to exhaust energy by emitting elastic waves into a support (e.g., a bridge abutment). This leaves only internal exhaustion mechanisms to reduce the vibratory response amplitude. With the long-term movement towards automatic manufacturing (e.g., Grumman beam builder bays, or the more recent Archinaut space-borne additive manufacturing system), joints are rigid and thus the associated frictional loss mechanisms are practically nonexistent. In this work, the addition of pendant structures to beams and beam-based frames is studied for their ability to exhaust vibrational energy. Placing any sort of additional hole pattern or attached pendant structure along the length of the frame elements will cause them to become one-dimensional phononic crystals, thereby opening bandgaps that block elastic wave propagation along them. Additional bandgaps are opened if the periodically placed structures are resonant, making each frame element into a one-dimensional resonant metamaterial (RMM). Each unit cell of the RMM exhausts energy through localized vibrations due to its structural design rather than material or frictional losses, making them an ideal companion for automatic manufacturing solutions. Here, both beam-mass and coiled phononic crystals are studied as pendant structures to modify the response.

Presenting Author: Carson Willey AFRL/UES

Presenting Author Biography: Carson L. Willey obtained his B.S. of mechanical engineering and M.S. of computational mechanics from Miami University in 2008 and 2011 respectively. He went on to pursue a Ph.D. in engineering mechanics at the University of Cincinnati, completing a research program in nondestructive testing and evaluation. Specifically, this work sought to improve guided wave tomography, a means of ultrasonic imaging which can be used to reconstruct a quantitative map of wall thickness in a structure. Currently, Carson works as a contractor at the Air Force Research Laboratory at WPAFB, OH. In this role, he pursues the development of phononic crystals and resonant metamaterials to better understand how their unique mechanical qualities can be applied to solve problems pertinent to the Air Force.

Authors:

Carson Willey AFRL/UES
Vincent Chen AFRL/UES
Madeline Lowry Dept. of Mechanical & Aerospace Engineering, University at Buffalo
Mostafa Nouh Dept. of Civil, Structural and Environmental Engineering, University at Buffalo
Abigail Juhl AFRL