In SSDSL, we conduct theoretical and experimental research at the intersection of smart structures and dynamical systems. Some examples are given below.
One of our primary research interests is exploiting nonlinear dynamic phenomena in emerging fields. For instance, we employ bistable and monostable nonlinear electromechanical structures (e.g. beams and plates with piezoelectric laminates) for frequency bandwidth enhancement and also to exploit secondary resonances as well as modal interactions in vibration energy harvesting (figure a). The goal in the field of vibration-based energy harvesting is to convert ambient vibration into electricity for enabling self-powered electronic components such as wireless sensor networks used in monitoring applications. Nonlinear energy harvesters developed in our lab offer orders of magnitude larger frequency bandwidth as compared to their linear counterparts, yielding efficient energy conversion over a wide range of excitation frequencies. In this context we are interested not only in the prototype design, development, and fabrication, but also in understanding complex dynamic interactions of intentionally designed and inherently present nonlinearities, as well as intrinsic and extrinsic nonlinear dissipative effects through rigorous experiments and high-fidelity modeling.
Broadband vibration attenuation (figure b) is of interest for a wide range of engineering applications, spanning from industrial machines to aerospace and civil engineering structures. We explore broadband vibration damping using metamaterials with locally resonating components. For an effective use of metamaterial concepts in low-frequency dynamics of finite structures, research is needed to bridge the gap between the dispersion characteristics and modal behavior of the finite host structure with its resonator attachments. Both linear and nonlinear structures are investigated for amplitude dependent damping applications. Other than purely mechanical vibration absorber design architectures, piezoelectric shunt damping with nonlinear switching circuits is applied to flexible nonlinear structures for bifurcation suppression and vibration attenuation (figure b).
Bio-inspired aquatic and aerial structures with smart materials are also investigated as scalable and effective research platforms to explore other multiphysics problems, such as aquatic locomotion (figure c). A novel untethered piezoelectric robotic fish platform was developed and tested in our lab and proven to outperform its smart material-based swimmer counterparts, offering a geometrically scalable alternative to motor-based robotic fish without compromising the swimming speed. The fundamental research problem in underwater nonlinear actuation is to understand the dynamics of fluid-loaded fiber-based flexible piezoelectric structures for broad range of actuation levels. Combination of elastic, coupling, electric field, and dissipative nonlinear effects in piezoelectric actuation with geometric nonlinearities and aspect ratio-dependent fluid loading effects constitutes the main challenge in this research topic. Fluid-loaded piezoelectric structures are of interest also for contactless acoustic power transfer research in our lab. As compared to well-explored inductive coupling, acoustic power transfer offers several advantages such as long transmission distances and elimination of magnetic fields. Acoustic-structure interaction modeling of contactless power transfer for bridging the transmitter and receiver electroelastic dynamics through the propagation medium as well as performance enhancement are of interest in this research (figure c).
Wave propagation in adaptive structures is another intriguing research topic especially for energy harvesting (figure d). In many cases structural energy is in the form of propagating waves rather than standing waves. Collaborative research efforts we lead explore elastic mirror and lens concepts for wave focusing and thereby enhanced structure-borne wave energy harvesting. Beyond the energy harvesting concepts, adaptive electroelastic components inserted to waveguides are also investigated for establishing tunable and selective narrowband-broadband reflection and transmission characteristics toward enabling next-generation multifunctional wave devices.
Our research has been funded by various agencies including the National Science Foundation, the National Institute of Standards and Technology, and the Air Force Office of Scientific Research.