Seminar: Negative Stiffness: Vibration damping, impact isolation, and elastic wave control

Recent advances in micro-, nano-, and additive manufacturing technology have opened the door to the development of engineered materials and structures demonstrating exotic dynamic mechanical behavior that enable elastic wave cloaking, negative refraction, and super-resolution. The same research has also reinvigorated research addressing long-standing engineering challenges such as the ability to control unwanted noise and vibration. This work presents a novel class of engineered structures with significant promise to improve vibration damping and isolation treatments, impact isolation technology, and elastic wave manipulation: negative stiffness (NS) elements. A mechanical system displaying negative stiffness is characterized by a loading state that requires a decreasing force level to increase the deformation of the system. Systems displaying NS will possess regions of negative curvature in their strain energy response as a function of deformation, hence they are unstable when unconstrained. Analytical and experimental results will be presented demonstrating that NS systems comprised of buckled beams in parallel with positive stiffness springs can be used to construct quasi-zero stiffness vibration isolation systems which provide high static but low dynamic stiffness for compact base isolation design. Transmissibility measurements of these same systems show that the nonlinearity of NS systems constructed from buckled beam structures enable tunable vibration isolation behavior and isolation from impact. Modeling results will be presented demonstrating that sub-wavelength NS elements embedded in a viscoelastic material can be used to design vibration damping treatments with increased loss factor and minimally reduced stiffness to reduce the ring-down time for an impulsively loaded multi-layered beam. Finally, numerical investigations on the use of NS honeycomb structures as tunable elastic wave manipulation will be presented.

About the Speaker

Dr. Haberman is an Assistant Professor in the Department of Mechanical Engineering at the University of Texas (UT) at Austin with a joint appointment at the Applied Research Laboratories UT Austin. He received his Ph.D. and Master of Science degrees in Mechanical Engineering from the Georgia Institute of Technology in 2007 and 2001, respectively, and received a Diplôme de Doctorat in Engineering Mechanics from the Université de Lorraine in Metz, France in 2006. His undergraduate work in Mechanical Engineering was done at the University of Idaho, where he received a B.S. in 2000. Dr. Haberman's research interests are centered on elastic and acoustic wave propagation in complex media, acoustic metamaterials, new acoustic transduction materials, ultrasonic nondestructive testing, and vibro-acoustic transducers. He has worked extensively on the modeling and characterization of composite materials and the multi-objective design of acoustical materials. His current research focuses on modeling, design, and testing of composite materials, metamaterials, and structures for applications areas that include the absorption and isolation of acoustical, vibrational, and impulsive energy using negative stiffness structures, acoustic cloaking, and non-reciprocal acoustic and elastic wave phenomena. His work has been featured in Physics Today, Scientific American, NBC News, and National Public Radio.

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