Acoustic Metamaterial: From controlling the sound field to manipulating acoustic wave
|Dr. Jun Yang is the Distinguished Professor of Chinese Academy of Sciences (CAS), University of Chinese Academy of Sciences (UCAS) and the director of the Key Laboratory of Noise and Vibration Research at CAS. He obtained the Ph.D. degree in acoustics from Nanjing University, China in 1996. He served at Nanyang Technological University, Singapore, as an assistant professor, and an associate professor in 2003 and 2005, respectively. Since 2004, he has been a professor at the Institute of Acoustics, CAS. Dr. Jun Yang has completed over 30 projects for industries and the government and contributed significantly to acoustics research and education. He has published over 370 journal and proceeding papers, and has been granted more than 40 patents. Many of his research results have been used in practical applications. Recently, he obtained the Pollyanna Chu Outstanding Teacher Prize in 2014, Excellent Scientist Award by the Chinese Institute of Electronics in 2015, and Excellent Graduate Advisor Award by CAS in 2016.|
Dr. Jun Yang is a Fellow of the International Institute of Acoustics and Vibration (IIAV), Acoustic Society of China, and Chinese Institute of Electronics. He chaired the Local Organizing Committee for ICSV21 in 2014. He is an Executive Director of Acoustic Society of China, and chairs the Environmental Physics Society of China and the Audio Engineering Society of China.
Chinese Academy of Sciences (CAS), University of Chinese Academy of Sciences (UCAS)
|Acoustic metamaterials are artificial materials with periodic or pseudo-periodic unit cells. Acoustic metamaterials mainly derive their responses from their geometrical structures rather than their chemical components. By adjusting the structural parameters of acoustic metamaterials, it is possible to obtain some extraordinary acoustic parameters that cannot be realized using natural materials, including negative mass density and negative bulk modulus values, anisotropic mass density tensors and anisotropic elasticity tensors. These novel properties have great application prospect in noise control, acoustic high-resolution imaging, acoustic detection, and so on. This lecture presents the history and development trends of the acoustic metamaterials: from phononic crystals to acoustic cloak, people realized not only the control of the sound energy, but also the manipulation of the acoustic wave propagation path.|
Unique Vibration Phenomena in High-Speed, Lightweight, Compliant Gears
|From 2012 Prof. Parker is the L. S. Randolph Professor in the Department of Mechanical Engineering at Virginia Tech, where he also served as Department Head. Previously he was a University Distinguished Professor and the Executive Dean at the University of Michigan-Shanghai Jiao Tong University Joint Institute. He received his M.S. and Ph.D. degrees from the University of California, Berkeley.|
Prof. Parker’s research examines the vibration of high-speed mechanical systems. One major focus has been the vibration of gear and power transmission systems. He has consulted for several companies internationally where analyses based on his research have solved vibration problems in the automotive, helicopter, wind turbine, and aircraft engine industries. He has also worked on cyclically symmetric systems, axially moving media, centrifugal pendulum vibration absorbers, and disk-spindle systems. His publications have been cited roughly 6000 times.
Prof. Parker is a Fellow of the American Society of Mechanical Engineers (ASME) and the American Association for the Advancement of Science. He received the 2015 ASME N. O. Myklestad Award for “major innovation in vibration research and engineering.” The Chinese government selected him as an inaugural awardee for its 1000 Person Plan (千人计划). He has received the US Presidential Early Career Award for Scientists and Engineers (“…the highest honor awarded by the US government to scientists and engineers early in their independent research careers”), the National Science Foundation CAREER, and the US Army Young Investigator Awards, as well as the ASME Gustus Larson Award, Ford Chief Engineer Award, French government Poste Rouge Award, SAE Ralph Teetor Educational Award, ASEE’s Global Engineering Educator and Outstanding Faculty Awards, and the Journal of Sound and Vibration Doak Prize.
He serves on the Editorial Board of the Journal of Sound and Vibration and has been Associate Editor for Mechanism and Machine Theory and the ASME Journal of Vibration and Acoustics.
Prof. Parker has been a Visiting Researcher at Polytechnic University of Turin, Risoe National Lab (Denmark), the University of New South Wales, the University of Sydney, Tokyo University, NASA Glenn Research Center, and INSA Lyon.
Department of Mechanical Engineering
|Gears have recently been aggressively adopted in large aircraft engines because they improve turbine and fan blade efficiency by better matching the optimal speeds of the associated shafts. The high operating speeds and extreme focus on weight reduction lead to gear vibration behaviors that are distinct from conventional gears. High speeds give high excitation frequencies, and lightweight, thin-walled gears have lower natural frequencies. This combination triggers resonance, gyroscopic effects, nonlinearity, vibration of the gears as elastically compliant bodies, and parametric instability. These behaviors are driving development of new models and analysis tools different than what is typical for conventional gears. This presentation will start with industrial examples motivating the work. Next, we describe modeling and analysis of gear vibration using analytical and finite element/contact mechanics methods, with special attention to planetary gears because they are the de facto standard in aerospace applications and because of their interesting dynamics arising from cyclic symmetry. These models, and their experimental validations, will be used to illustrate and explain, without emphasis on mathematical details, the unique vibration behaviors that occur and how the analytical/computational findings have powerful practical implications.|
Step forward in higher order signal processing for vibro-acoustical structural health monitoring and NDT: novel nonlinear higher order frequency response functions
|Len Gelman is PhD, Dr. of Sciences (habilitation) and an Academician.|
Len is a Professor and Chair in Signal Processing and Condition Monitoring, the Executive Director of the International Society for Condition Monitoring, the Past Immediate President of the International Institute of Acoustics and Vibration and the Editor-in-Chief of the International Journal of Condition Monitoring.
He has 30 years’ experience in vibro-acoustical condition monitoring and NDT of complex systems/materials/structures both in industry and academia.
Len is the Principal Investigator on numerous industrial and research grants, including from the USA National Academy of Sciences, USA National Research Council, USA International Science Foundation, USA Civilian Research and Development Foundation, USA MacArthur Foundation, Lady Davis (Israel), Centro Volta (Italy), UK EPSRC, UK Department of Trade and Industry, UK Royal Society, Rolls Royce, SKF, Scottish Southern Energy, Caterpillar (USA), Shell, London Underground, Boeing and three multi-disciplinary EU research grants.
Len is a Fellow of the British Institute of NDT, a Fellow of the Institution of Diagnostic Engineers and a Fellow of the International Association of Engineering.
Len is the author of over 250 publications (including 17 patents and 7 books) and more than 36 plenary keynote conference papers at the major international conferences.
Len is Chair of the 2007 World Congress on Engineering Asset Management, the Honorary Co-Chair of the 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 and 2017 World Congresses of Engineering, the General Chair of the 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, and 2018 International Condition Monitoring Conferences and the General Chair of the First World Congress on Condition Monitoring. He has participated in the scientific boards of numerous prestige international conferences and he is a member of editorial boards of numerous international journals.
Len is a Chief Designer of numerous technologies and prototypes for vibro-acoustical condition monitoring. He lectures, conducts training programs and consults industry and academia in all parts of the world and has held visiting professorships at 6 overseas universities.
Recently, he was awarded Rolls-Royce award for innovation, Oxford Academic Health Science Network Award, EC Fellowship Award and William Sweet Smith Prize for development of the novel vibro-acoustical technologies. In 2017, he was also awarded the COMADIT Prize by British Institute of NDT for significant contribution through research/development in condition monitoring to benefit of industry and society.
He is a member of the IIAV since 1997, a Director of the IIAV in 2007-2011 and the President of the IIAV in 2014-2016. Starting in 2003, Len has organised multiple structured sessions at the IIAV’s International Congresses. He is the Chair of the Honours and Awards Committee of the IIAV and the Chair of the Nominations and Election Committee of the IIAV and a member of the editorial board of the International Journal of Acoustics and Vibration (IJAV), published by the IIAV.
Cranfield University, UK
|Novel class of higher order signal processing technique, the nonlinear frequency response functions based on the higher order spectra, are proposed, developed and investigated for vibro-acoustical monitoring of structure/materials non-linearity and signal non-Gaussianity due to damage for cases of the phase coupled interferences of an excitation. The proposed techniques developed for stationary and non-stationary conditions of structure/material testing.|
The significance of the proposed techniques is that they provide a measure of the structure/material output HOS in response to the structure/material input HOS and eliminate the influence of the phase coupled interferences of structure/material excitation on non-linearity and non-Gaussianity detection/diagnosis.
The proposed techniques are novel generalisations of the classical frequency response functions for the higher order spectral analysis.
Validation of these novel techniques by simulation and experiments in laboratory and in field conditions will also be presented for testing turbomachinery blades and deep foundation concrete plies in stationary and non-stationary conditions.
It is shown that the proposed techniques provide an essential effectiveness gain for the detection of non-linearity due to fatigue damage in comparison with the classical HOS for the case of the phase coupled interferences of a structure excitation.