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Engineered, nonlinear material systems for controllable propagation of shock, vibration, and sound

Numerous applications demand lightweight materials to absorb and govern shock, vibration, and acoustic energies but an adverse trade-off often exists in balancing energy dissipation and guidance capabilities with the material mass employed. We are leveraging fundamental principles of structural mechanics to create and assess lightweight engineered nonlinear material systems that cultivate extreme vibroacoustic damping properties by virtue of strategic internal architectures and constraints. The efforts within this LSVR research initiative are supported by several organizations, including the Ford Motor Company, Owens Corning Science and Technology, and Honda R&D Americas Inc.

Foldable, origami-inspired acoustic arrays for large, simple, and real-time guidance of wave energy

Conventionally, acoustic wave guiding is achieved by virtual repositioning of transducer elements via digital beamforming techniques. Computational burden, cost, and complex implementation may be exacerbated because a sufficiently great number of elements is needed to authoritatively guide wave energy by digital methods. Yet, for acoustic elements that are reconfigured according to a folding, tessellated structure, the repositioning is genuine and not prone to growing burdens since a single drive or receive signal may be employed. Inspired by the technical analogies, we are exploring origami-inspired acoustic arrays to steer and focus acoustic waves using the low-dimensional reconfiguration of origami tessellations upon which array elements are placed. The folding architectures also cultivate portable acoustic radiators for transport and deployment, a quality of importance in applications with extreme space or mass constraints, such as for deployable medical ultrasonic probes and underwater sonar monitoring systems. The efforts within this LSVR research initiative are supported in part by the Acoustical Society of America.

Vibration and wave energy transfer, capture, and dissipation in multistable systems

The transitions among stable states in structural, mechanical, or material systems can be both a source of potential and a concern. For instance, applications of vibration energy harvesting may be propelled by exploiting such dynamic transitions for large mechanical-to-electrical energy capture, while slender aerostructures may be greatly harmed should such dynamic behaviors fatigue airframe components. Yet, the strong nonlinearities exhibited in multistable structural dynamics makes them difficult to understand and faithfully predict.

To address this challenge, we are creating analytical approaches to accurately predict and explore the steady-state, transient, and stochastic dynamics of multistable systems. The approaches enable new insight on susceptibility and robustness of such structural systems by way of energy-based quantifiers. The efforts within this LSVR research initiative are supported by several organizations, including the National Science Foundation, The Ohio State University Center for Automotive Research, Mide Technology Corp., the Defense Advanced Research Projects Agency (DARPA), the U.S. Air Force Research Laboratory, and the American Society of Mechanical Engineers Haythornthwaite Young Investigator Award.

Muscle-inspired, modular metastable architectures for adaptive, energetic engineering systems

Skeletal muscle is a prime inspiration towards the development of adaptive engineered structural/material systems. All at once, muscle is a super-structure, an energy coordinator, and generator of force. Recent studies have shown that the fundamental, passive constituents of skeletal muscle are analogous to strategically developed modular systems of metastable oscillators. We are developing and exploring such architectures on meso- and macroscale platforms to elucidate methods by which engineered systems may be invested with the desirable properties of skeletal muscle, such as its intriguing passive force enhancement, self-stabilization, and robustness to perturbation. Moreover, through the muscle-inspired structural dynamic studies, the research may provide new opportunities to interpret the multiscale spectrum of mechanical principles underlying muscle energetics. This research is supported in part by the U.S. Army Research Office.

Leveraging instabilities for high sensitivity detection and monitoring

Traditional vibration-based structural monitoring approaches rely on small shifts in frequency information to identify that change has occurred in the system, whether the shift is representative of damage to an aircraft panel or an infinitesimal mass accumulation upon a microelectromechanical resonator. Such techniques are often prone to error in damped systems where measurements are difficult to process and separate from noise. We are overcoming these limitations by leveraging the instabilities of nonlinear sensing systems, such as bistability in circuits or in post-buckled sensing beams. The sudden transitions between the stable states require new approaches to be accurately predicted, but result in significant sensing enhancement and sensitivity when compared to tradition monitoring methods.