Plenary

 Plenary Speakers

Retrospective and prospects in structural mechanics and nonlinear dynamics

Reflections of a life, with topics, scholars, communities

After nearly half a century of intense development, nonlinear dynamics in mechanics has evolved into a well-defined discipline, with a comprehensive methodological and phenomenological framework. This significant maturation provides a timely opportunity to reflect on the field’s historical evolution and to identify the innovations necessary to keep it aligned with the cultural and technological demands of a rapidly changing society. This lecture serves as a witness of the progressive growth of the nonlinear dynamics community, seen through the lens of a structural mechanics researcher who has had the privilege of maintaining close connections with numerous scholars and emerging researchers over the past forty years. Framing personal thematic lines within four general phases of the development of nonlinear dynamics in mechanics, it is also intended to provide a tribute to those who have been pivotal in shaping the field—and can thus be regarded as ‘fathers’ of the discipline—as well as to numerous esteemed colleagues and friends. The main research trajectories and key contributors are mapped against an evolutionary framework that spans from classical to hybridized topics. Delving into the need to move from concepts and methods to new developments in which nonlinear dynamics is called to show its enormous potential for achieving goals in targeted technological contexts by harnessing nonlinear/global features and phenomena for a reliable engineering design, the discussion addresses challenges and future directions based on two key criteria: (i) Establishing connections with the foundational work of previous generations, highlighting how contemporary advances build upon past accomplishments; (ii) differentiating between challenges of intrinsic mechanical significance and the broader contributions that nonlinear dynamics can offer in the reliable modeling and effective control of various evolutionary phenomena, also extending beyond mechanical systems. 

Bio-sketch: Giuseppe Rega is Professor Emeritus, Sapienza University of Rome. Past Chairman of EUROMECH Nonlinear Oscillations Conference Committee and Italian Association of Theoretical and Applied Mechanics, member of CISM Scientific Council. Past EiC of Meccanica has been/is Advisor/AE/EBM of several archival journals. Organized scientific events within EUROMECH, IUTAM, ASME, NNM, CISM, and EURODYN. Plenary/Keynote Lecturer at many international conferences and academic institutions. Recipient of ASME Lyapunov Award (2017) and Ali H. Nayfeh Senior Award (2025). Honored with special issues of Nonlinear Dynamics and International Journal of Non-Linear Mechanics at 60th and 70th birthday anniversaries. Contributions to cable nonlinear dynamics, nonlinear oscillations, bifurcation and chaos in applied mechanics and structural dynamics, reduced-order modeling, control of oscillations and chaos, exploitation of global dynamics for engineering safety, smart materials, coupled oscillators, thermomechanical problems, and structural architecture.

Green Energy: Technology and Perspectives based on Smart Materials

The increasing global energy demand and the environmental impacts associated with fossil fuel consumption emphasize the necessity of developing clean and renewable energy technologies. This lecture first outlines the urgency of sustainable energy utilization in response to energy shortages and ecological challenges. It then compares three primary energy conversion mechanisms—electrostatic, electromagnetic, and piezoelectric technologies—in terms of power density, transmission efficiency, structural integration, and economic cost, highlighting the advantages of piezoelectric materials in distributed energy harvesting. Finally, various smart-material-based structural designs for harvesting energy from ocean waves, wind, high-rise buildings, and vehicles are presented, demonstrating their effectiveness and application potential in sustainable and decentralized energy systems.

Bio-sketch: Professor Quan Wang currently serves as the executive president of Shantou University. In recognition of his outstanding academic contributions, he was elected to the Canadian Academy of Engineering and the Royal Society of Canada in 2015 and 2016, respectively. He was awarded the Blaise Pascal Medal from the European Academy of Sciences in 2019. Professor Wang is also a fellow of several leading international professional societies, including the American Society of Civil Engineers and the American Society of Mechanical Engineers. In addition, he has served as Deputy Editor-in-Chief of the International Journal of Mechanical Sciences. He is widely recognized as an influential scholar in the fields of energy harvesting, smart materials, and nanotechnology.

Nonlinear Dynamics and Chaos in Smart Systems

Bioinspiration is a paradigm that extracts design principles from biological and natural systems. Based on that, it is possible to create systems and structures with adaptive behavior according to its environment. Smart materials have an essential importance on this idea being used as sensors and actuators that define the remarkable system characteristics. Besides, natural rhythms are inspiring new situations and therefore, the investigation of nonlinear dynamics, chaos and control is establishing other design paradigms. The use of bioinspired smart systems is now evolving to create origami-inspired systems based on the ancient art of paper folding. Basically, the main idea of the origami is to create a three dimensional structure from a plane source. Adaptive origamis have been explored in order to produce foldable, adaptive structures that can be applied in several areas of the human knowledge. This presentation deals with the nonlinear mechanics of smart bioinspired systems. Smart system applications and their multiphysical behaviors are of concern, discussing the system modeling. Shape memory alloy systems, origami-inspired structures, mechanical energy harvesting, chaos and chaos control are some subjects presented to give a general idea of the research activities. The rich, complex dynamical response of these systems is of special concern.

Bio-sketch: Marcelo A. Savi is Ph.D. in Mechanical Engineering and Professor at Federal University of Rio de Janeiro (COPPE - Mechanical Engineering) being the Head of the Center for Nonlinear Mechanics. He has published over 550 journal and conference papers, 5 books and about 19 book chapters. Awards and distinctions were received including: FAPERJ Award of Outstanding Researcher in Exact Sciences, Earth Sciences, and Engineering; UFRJ solemn tribute to the most influential researchers in the world; COPPE Award Giulio Massarani of the Academic Merit; CNPq Researcher level 1A; Scientist of Rio de Janeiro. He is actively involved as advisor of graduate and undergraduate students, summing more than 150 works. Scientific exchanges with research centers in Brazil and all over the world should be highlighted. He has administrative experience as head of department, graduate coordinator, and university committees. He serves as Editor-in-Chief of the Journal of the Brazilian Society of Mechanical Sciences and Engineering (2024-present); Associate Editor of journals including International Journal of Mechanical Sciences (2018-present), Journal of Vibration and Control (2017-2026), ASME – Journal of Computational and Nonlinear Dynamics (2019-2025), Mathematical Problems in Engineering (2018-2024), Journal of the Brazilian Society of Mechanical Sciences and Engineering (2006-2016); and member of the Executive Editorial Board of Smart Materials and Structures (2025–present). He is member of academic societies including ASME, ABCM and SBF. Research interests are related to nonlinear mechanics where it should be highlighted smart material and structures; nonlinear dynamics, chaos and control; biomechanics and ecology.

CV: http://lattes.cnpq.br/1224532648969159

Maps, Stability and Control in Non-Smooth Dynamical Systems

Non-smooth dynamical systems provide a rigorous framework for describing complex topological evolutions of physical phenomena often encountered in science and engineering. While these systems have been researched extensively over recent decades, their potential for optimising engineering design is only now becoming widely recognised. This lecture focuses on the dynamics of non-smooth models used in engineering applications, emphasising the need for deeper theoretical understanding and experimental validation.

The lecture begins by presenting a general methodology for reducing multidimensional continuous flows to low-dimensional iterative maps, using a drifting impact oscillator [1] as a primary example. A global iterative map [2] is constructed by the composition of local maps as the trajectory traverses smooth sub-regions of the state space. By monitoring the intersections of the flow with a chosen switching manifold, a low-dimensional map is developed where the degree of dimensional reduction is directly linked to the dimension of the boundary. For the drifting impact oscillator, a five-dimensional flow is successfully reduced to a one-dimensional semi-analytical map.

In the second part, a recently developed mass-excited impact oscillator is introduced. In this archetypal setup [3], an electromagnetic excitation force acts directly on the mass, providing greater precision and a wider range of excitation patterns compared to traditional base-excited rigs. Evaluation of the stability of periodic orbits in the vicinity of grazing conditions for the impact oscillator is demonstrated using both analytical and experimental techniques [4].

New developments to the Time-Delayed Feedback (TDF) control method are then discussed, specifically designed for nonlinear systems featuring co-existing attractors [5,6]. These novel strategies maintain the low information requirements of original TDF but extend applicability to scenarios where standard methods fail to steer the system toward a desired stable response.

Finally, applicability of non-smooth models is demonstrated using the Anti-Stick-Slip Tool (ASST) as an example. ASST is designed to mitigate severe torsional vibration in drill-strings [7,8] which exhibit highly complex behaviour due to material and geometric nonlinearities. The ASST controls these vibrations by converting excessive external torque into axial bit movement, effectively eliminating the unwanted stick phases. By accounting for distinct non-smooth operational phases, the model facilitates a comprehensive evaluation of the tool's performance across diverse loading conditions, thereby enabling its optimisation.

References

1. Pavlovskaia, E. et al. (2001) Phys. Rev. E 64, 056224.

2. Pavlovskaia, E. & Wiercigroch, M. (2007) J. Sound Vib. 305, 750-771.

3. Wiercigroch, M. et al. (2020) Nonlinear Dyn. 99, 323–339.

4. Ing, J. et al. (2008) Phil. Trans. R. Soc. A 366, 679-704.

5. Costa, D. et al. (2020) Nonlinear Dyn. 102, 835–861.

6. Costa, D. et al. (2023) Physica D 443, 133587.

7. Osguei, A.T. et al. (2023) Physica D 443, 133525.

8. Khodadadi, M. et al. (2022) Int. J. Mech. Sci. 221, 107188.

Bio-sketch: Professor Ekaterina Pavlovskaia is the Head of the School of Engineering at the University of Aberdeen, where she holds a Personal Chair. A Chartered Engineer and Fellow of the Institution of Mechanical Engineers (FIMechE), she made history in 2021 as the first woman to lead the University's School of Engineering.

Ekaterina graduated with a first-class honours degree in Mechanical Engineering from St Petersburg State Polytechnical University in 1996. She went on to obtain a PhD in Applied Mathematics and Physics from the Russian Academy of Science in 1998. Following an academic post at St Petersburg State University and a research period at the Ford Research Laboratory in the USA, she joined the University of Aberdeen as a Research Fellow in 2000. She was appointed as a lecturer in 2003 and subsequently promoted through the ranks to a Personal Chair in 2013.

An expert in the physical and mathematical modeling of engineering systems, her research encompasses non-smooth dynamics, riser mechanics, drilling technologies, and rotordynamics. To date, Ekaterina has authored over 200 scientific publications, including more than 75 refereed journal papers, and she currently serves as a Subject Editor for the Journal of Sound and Vibration.