蜜糖直播

Dynamics of quasiperiodic and quasicrystalline elastic metamaterials

Metamaterials are man-made artificial materials based on particular arrangements and combinations of known materials that produce unique properties not encountered in it鈥檚 individual constituents. While the vast majority of metamaterials are based on periodic designs based on a repeating unit cell, our group is currently investigating quasiperiodic and quasicrystalline metamaterials that break the periodicity paradigm. The first category is based on modulations of the properties of inclusions, such as point masses, springs, resonators or stiffeners, that are given by a deterministic non-periodic pattern. In the second case, quasicrystalline materials may exhibit symmetries which are not possible to obtain in periodic materials, such as 5,7 ,8 and 10-fold rotational symmetries. The investigation of the dynamics of such materials reveals intriguing properties such as topological bandgaps and localized vibration modes that can be manipulated by a few key parameters, and wave directionalities enabled by higher order rotational symmetries that expand the behavior known to be possible in periodic metamaterials.

Topological states in constant mean curvature surfaces

Surface structures with constant mean curvature (CMC) possess complex and highly symmetrical structures with optimized material properties, which gives the framework of CMC surfaces聽remarkable freedom in the design space for the properties of structural assemblies. Owing to their unique combination of light weight, high strength, and rich design space, periodic CMC surfaces provide new opportunities for novel metamaterial design of potential engineering relevance. The concepts of topological gapped/gapless phases combined with versatile CMC surfaces complement existing functionalities with wave isolation, impact mitigation, acoustic imaging, noise control, energy harvesting, and other capabilities. Our group is interested in exploring聽dynamic functionalities such as topological frequency response that provides novel and unconventional mechanical and acoustic functionalities in a single material platform.

Cranial Lamb waves for skull and brain diagnostics and therapy

Due to its morphological nature, the human skull exhibits a waveguide-like behavior that supports a Lamb wave motion similar to that observed in multilayered orthotropic plates. While the skull presents a barrier to pressure waves used in focused ultrasound (FUS) based treatments, which are usually limited to central regions of the brain, waves that exploit the quasi-bidimensional structure of the cranial bone can possibly create new treatment options for neurological conditions, especially at the brain periphery. In addition, they provide a non-invasive diagnostic tool for the skull that can overcome typical drawbacks of FUS such as local bone heating. Our research group theoretically and experimentally investigates the nature and characteristics of cranial Lamb waves with the aim to exploit their inherent dispersive features for various diagnostic and therapeutic applications. These include the mechanical characterization of the cranial bone and sutures, and the implementation of new transducer setups for enhanced intracranial ultrasound delivery which leverage Lamb mode conversion within the skull to achieve better spatial resolution and target small regions of the brain.聽

Acoustic communication through metallic plates by means of piezoelectric and magnetostrictive transduction

Communication across a wall of an enclosed metallic structure cannot be achieved by means of electromagnetic waves due to the Faraday effect. A solution consists in transmitting information through the barrier by means of mechanical waves actuated and received by piezoelectric or magnetostrictive transduction. Different challenges such as the transmission level and the usable bandwidth need to be addressed to improve the acoustic communication. Our group focuses on modeling the data transmisssion and improving the communication through transducer shaping and the addition of elements such as material layers and electrical components in the connected circuits.

Fundamental mechanisms of distributed bleed flow control over an aeroelastic wing

Flow-controlled, variable aerodynamic load distributions effected in flight by interactions between wing surfaces and the embedding flow that are regulated by surface-integrated distributed active bleed can enable a new class of adaptive, lightweight, agile, highly-deformable wings. The use of bleed actuation for aeroelastic control is new, and represents a significant departure from earlier approaches that have relied on direct mechanical deformation of the lifting surfaces or on moving control surfaces.聽 Our current efforts focus on the fundamental mechanisms of the coupled fluid-structure interactions between the bleed actuation and the flow over static and dynamic flexible wings. Additionally, applications of distributed bleed flow control are examined when applied to vibration control.聽