A wide “one-way” street for elastic wave


Often, propagation of energy fluxes in conventional materials and structures is normally reciprocal and symmetric. Consequently, much effort has been devoted to exploring asymmetric acoustic/elastic-wave transmission in various structural designs. In addition, asymmetric manipulation of acoustic/elastic waves has attracted much attention due to the challenging one-way acoustic/elastic-wave transmission, as well as enormous application potential for various practical scenarios. As of now, various approaches have been proposed to realize asymmetric acoustic/elastic wave transmission. Based on whether an external energy is needed, these methods can be classified, in general, into two categories: active and passive designs.

A review of the existing plethora of literature shows that the propagation unidirectionality is normally confined to a narrow frequency band. Moreover, the frequency bandwidths for asymmetric transmission in such structures are normally confined to narrow frequency ranges, and the possibility to realize asymmetric elastic-wave transmission in multiple broadband frequency regions still needs more exploration.

A closer look on this topic reveals that very little has been published about the systematic study of damping effect on asymmetric wave transmission. In this view, Professor Bing Li at  Northwestern Polytechnical University together University of Akron scientists, Professor K.T. Tan, Dr. Sagr Alamri, Dr. Garrett Mchugh and Professor Nicholas Garafolo developed a dissipative diatomic acoustic metamaterial with dual resonators with the aim being to realize asymmetric elastic-wave transmission in multiple broadband ranges. To be specific, the researchers focused on developing a dissipative acoustic metamaterial with diatomic resonators for broadband asymmetric elastic-wave propagation. This work is currently published in the research journal, Journal of Sound and Vibration.

To begin with, the team theoretically, numerically, and experimentally investigated the effect of damping on the asymmetric wave transmission. Further, numerical verifications were conducted using both mass-spring-damper lattice system and continuum models, and excellent agreements were obtained. Eventually, transient wave responses in time and frequency domains were also investigated.

The researchers reported that a systematic analytical discussion revealed that the frequency bandwidths of asymmetric transmission regions could be significantly enlarged by the merging effect of dissipative dashpots. Moreover, they further observed the asymmetric elastic-wave transmission in the proposed dissipative metamaterial structure experimentally. Of much importance, they highlighted that the enlarged asymmetric transmission bands could be analytically predicted and mathematically controlled by carefully designing and deliberately selecting the unit size parameters and material properties.

In summary, the study presented the in-depth assessment of the proposed dissipative diatomic acoustic metamaterial with dual resonators. Generally, the researchers noted that there was a specific damping range over which the ATB bandwidths could be increased. Overall, in an interview with Advances in Engineering, Professor Bing Li emphasized on how their work could be beneficial for a slew of applications in elastic-wave control and directional transmission devices.

A wide “one-way” street for elastic wave - Advances in Engineering
Fig. 1. Schematic of the proposed dissipative diatomic metamaterial for asymmetric wave transmission.
[youtube https://youtu.be/bN-e76vIbTo&w=1019&h=573]

About the author

Dr. Bing Li is currently an associate professor in the School of Aeronautics at Northwestern Polytechnical University. He conducted his Post-Doctoral training in 2015-2018 at The University of Akron (Akron, US). He obtained his Ph.D. in the College of Engineering at Peking University (Beijing, China) in 2015. He received his Joint-Supervision Ph.D. training in the School of AMME at The University of Sydney (Sydney, Australia) in 2013-2014.

Dr. Li’s primary research interests lie in the field of dynamical responses of advanced composite structures and elastic/mechanical/acoustic metamaterials. Aim at addressing the challenges of designing macro-micro-nanoscale metamaterials that affect/manipulate/control wave propagation; and understanding the interaction mechanisms between structural dynamics and microstructures/inhomogeneity, his research work emphasizes impactful results for practical applications in aerospace, structural and defense engineering, especially including elastic wave control, vibration/wave attenuation, noise insulation and structural health monitoring, among others.

He has published over 50 research articles in top-tier peer-reviewed journals and major international conferences. He is an active journal reviewer for more than 10 international journals, is on the Editorial Board of Int. J. Mech. Eng. Appl. He was elected as the Oversea Young talents of Northwestern Polytechnical University (2018), also the Outstanding Reviewer for NDT and E International (2018) and Composite Structures (2017). He is a member of The Acoustical Society of America (ASA), American Society for Composites (ASC), American Institute of Aeronautics and Astronautics (AIAA), and International Phononic Society (IPS).

Email: [email protected]

About the author

Dr. Sagr M. Alamri is currently an assistant professor in Mechanical Engineering at King Khalid University (Abha, Saudi Arabia). He completed his doctoral studies under the supervision of Dr. K. T. Tan and Dr. Bing Li in 2018 in the Mechanical Engineering department at the University of Akron (Ohio, US). He was awarded his M.S. degree in 2011 from Mechanical Engineering department at University of Hartford (Connecticut, US), and B.S. Diploma in Mechanical Engineering in 2007 from King Khalid University (Abha, Saudi Arabia).

His primary research  interests are focused on impact mitigation and wave control based on elastic/acoustic metamaterial structures.

About the author

Dr. K.T. Tan has been an assistant professor in Mechanical Engineering at The University of Akron since Fall 2014. He was a Research Scientist at the Institute of Materials Research and Engineering, Singapore in 2013-2014. He received his Post-Doctoral training in 2011-2013 at the Purdue University School of Aeronautics and Astronautics, working with Prof. C.T. Sun in the area of acoustic composite metamaterials. Dr. Tan earned his Ph.D. in Aerospace Engineering at Tokyo Metropolitan University in 2011, and his B.Eng. and M.Eng. in Mechanical Engineering at the National University of Singapore in 2004 and 2006, respectively.

Dr. Tan’s primary research interests and expertise lie in the field of composite materials and metamaterials, targeting multi-disciplinary applications in defense, aerospace, energy production and biomedical device development.

He has published over 80 research articles in major international conferences and top-tier peer-reviewed journals. He is also the recipient of multiple awards, including the Firestone Research Initiative Fellowship (2018), the JSPS Invitational Fellowship (2016), ICA Young Scientist Grant (2013), the Metamaterials Young Researcher Travel Grant Award (2012), Best Poster Prize (6th International Conference on Fracture of Polymers, Composites and Adhesives in Les Diablerets, Switzerland, 2011), A*STAR International Fellowship (2011), Tokyo Metropolitan Government Scholarship (2008), and NUS Research Scholarship (2006).

Dr. Tan is an active journal reviewer (more than 50 international journals) and is presently on the Editorial Board of four international journals. He also is a member of The American Institute of Aeronautics and Astronautics (AIAA), American Society of Mechanical Engineers (ASME), American Society for Composites (ASC), Acoustical Society of America (ASA), American Society for Engineering Education (ASEE), and International Phononic Society (IPS).

About the author

Dr. Garafolo is an associate professor in the Mechanical Engineering department at the University of Akron. Before joining The University of Akron, Dr. Garafolo worked as a federal research contractor to NASA Glenn Research Center in Cleveland, Ohio under the umbrella of a multi-million dollar contract. His research interests are focused on thermo-fluid sciences, fluid-material interaction, advanced aerospace seals, near-hermetic fluid flows.



Sagr Alamri, Bing Li, Garrett Mchugh, Nicholas Garafolo, K.T. Tan. Dissipative diatomic acoustic metamaterials for broadband asymmetric elastic-wave transmission. Journal of Sound and Vibration, volume 451 (2019) page 120-137.

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