Invited Speakers

Professor Marian Wiercigroch FRSE

University of Aberdeen, UK

Opening Plenary Lecture: Bifurcations and Stability in Machining Processes

Professor Marian Wiercigroch educated in Poland, US and UK holds a prestigious Sixth Century Chair in Applied Dynamics and he is a founding director of the Centre for Applied Dynamics Research at the University of Aberdeen.
His area of research is theoretical and experimental nonlinear dynamics, which he applies to various engineering problems. Wiercigroch has published extensively (over 500 journal and conference papers) and sits on a dozen editorial boards of peer review journals. He is a frequent keynote and plenary speaker at major international conferences and the Editor-In-Chief of International Journal of Mechanical Sciences, a premier journal in mechanics and mechanical engineering.
He is the inventor of new patented drilling technology called Resonance Enhanced Drilling and the Founder and Chief Technology Officer of a spinoff company iVDynamics Ltd. He has established in Aberdeen unique experimental laboratories allowing to investigate complex nonlinear dynamic interactions in mechanical systems with the focus on energy generation.
He has received many awards and distinctions including a Senior Fulbright Scholarship (1994), Fellowship of the Royal Society of Edinburgh (2009), DSc honoris causa from the Lodz University of Technology (2013), Distinguished Professorships at the Perm National Research Polytechnic University (2017), Balseiro Institute (2018) and Yanshan University (2021). Marian is a Scottish Champion of Knowledge Exchange (2020) and he served as a panelist in the Research Excellence Framework (2014, 2021), which assess the quality of research in the UK.

Abstract...

Comprehensive understanding of chatter, bifurcations and stability is essential for improving productivity, quality, and efficiency of manufacturing operations. Chatter manifests itself as undesired large amplitude self-excited vibration, whilst bifurcation and stability analysis hold the keys to its effective control and suppression. Bifurcations in manufacturing occur when processing and system parameters cross certain values and(or) they are results of complex interactions resulting predominantly in creating or disappearance of limits cycles. Bifurcations in manufacturing processes belong to the most complex ones, where nonlinearities are very strong and play the dominant role e.g. [1]. Process stability is vital to ensure high-quality surface finish, dimensional accuracy, and extended machine and tool life.
In this lecture, first I will define nonlinearity, chatter, bifurcations and stability in manufacturing processes with the focus on metal cutting. Then I will discuss on the frictional chatter, which was introduced and investigated with my group and collaborators (see e.g. [2,3,4]). Chatter in precision grinding has been a subject of many our investigations, where low dimensional strongly nonlinear models were used to undertaken in depth analytical and numerical studies, see for example [5,6]. Finally, examples of advanced nonlinear dynamics techniques such as path following bifurcation analysis, basins of attraction [7], Poincare maps and Lyapunov exponents will be discussed, which have been used to examine stability and determine a practically important measure so-called cutting safety [8,9].

  1. Wiercigroch, M., Budak, E. Nonlinearities, chatter generation and suppression in metal cutting. Philosophical Transactions of the Royal Society of London: Part A 359, 663-693, 2001.
  2. Wiercigroch, M., Krivtsov, A.M. Frictional chatter in orthogonal metal cutting. Philosophical Transactions of the Royal Society of London: Part A 359, 713-738, 2001.
  3. Rusinek, R., Wiercigroch, M., Wahi, P. Influence of tool flank forces on complex dynamics of cutting system process. International Journal of Bifurcation and Chaos 24(9) 1450115, 2014.
  4. Yan, Y., Xu. J, Wiercigroch, M. Modelling of regenerative and frictional cutting dynamics. International Journal of Mechanical Sciences 156, 86-93, 2019.
  5. Yan, Y., Xu, J., Wiercigroch, M. Chatter in transverse grinding process. Journal of Sound and Vibration 333, 937-953, 2014.
  6. Yan, Y., Xu, J., Wiercigroch, M. Regenerative and frictional chatter in plunge grinding. Nonlinear Dynamics 86, 283-307, 2016.
  7. Yan, Y., Xu, J., Wiercigroch, M. Basins of attraction of the bistable region of time-delayed cutting dynamics. Physical Review E 96(3), 032205, 2017.
  8. Yan, Y., Xu. J, Wiercigroch, M. Estimation and improvement of cutting safety. Nonlinear Dynamics 98(4), 2975-2988, 2019.
  9. Yan, Y., Liu, G., Wiercigroch, M., Xu, J. Safety estimation for a new model of regenerative and frictional cutting dynamics. International Journal of Mechanical Sciences 201, 106468, 2021.

Professor Alexander Rachev,

Institute of Mechanics, BAS, Bulgaria

Plenary Lecture: ARTERIAL SOLID MECHANICS. A BRIEF REVIEW AND THE “BULGARIAN IMPRINT”

Alexander Rachev was born in Sofia in 1939. He graduated from the Faculty of Civil Engineering at the Higher Institute of Civil Engineering, Sofia in 1963. He received a Ph.D. from the Polish Academy of Sciences, Warsaw (Poland) in 1969 and a D.Sc. from the Bulgarian Academy of Sciences (BAS) in 1984.

Dr. Rachev began working as a research engineer at the Institute of Technical Mechanics (BAS) in 1963 and retired as a professor and head of the Department at the Institute of Mechanics BAS in 2004. From 1964 to 1973 his research activity was in the field of theoretical and applied mechanics (30+ papers), and then until now in vascular biomechanics (3 books in co-authorship, 200+ papers, 3400+ citations).

He was a visiting professor at the Swiss Federal Institute of Technology, (Lausanne), the University of Bologna, the University of Graz, the University of Osaka, the Georgia Institute of Technology in Atlanta (2000-2011), and the University of South Carolina in Columbia (2011-2012). He delivered postgraduate courses on vascular biomechanics organized by CISM (Udine), Politecnico di Milano, the University of Nottingham, and the Institute of Fundamental Technical Problems (Warsaw).

Dr. Rachev is a member of the Bulgarian Society of Biomechanics and ASME and a former member of the World Council of Biomechanics, the Scientific Council of the International Center of Biocybernetics (Warsaw), the Biomedical Engineering Society, and the European Mechanics Society. He is a member of the Editorial Board of the Bulgarian Journal Series of Biomechanics and a formal member of the Editorial Boards of two International, one Russian, and one Polish journal.

Dr. Rachev was included in the 2020 and 2021 ranking of Stanford University among "the first 2% of the most influential scientists in the world for overall scientific contribution.”

Abstract...

The talk is addressed mainly to this part of the audience that has never been engaged in research in arterial solid mechanics. The basic physiological function of arteries is to convey and distribute oxygenated blood to organs and tissues according to metabolic demands. A brief review of mechanical and biological processes that govern arterial performance is given. Special attention is paid to the constitutive formulation of arterial tissue in the framework of nonlinear continuum mechanics. Mathematical models that describe the passive, active, and remodeling response of arteries are presented. Some critical remarks express only the author’s personal opinion.

Each good research is unique and extends the boundaries of our knowledge. The “Bulgarian imprint” in the title refers to the results of Bulgarian scientists, in most cases in collaboration with foreign partners, that gained well-documented recognition and have a notable impact on the further development of specific topics of arterial biomechanics. 



Professor Jerzy Warminski
Department of Applied Mechanics, Lublin University of Technology, Lublin, POLAND
e-mail. J.warminski@pollub.pl,
www: https://j-warminski.pollub.pl/, ORCID:0000-0002-9062-1497

Plenary Lecture: Nonlinear Vibrations of Multi-Stable Mechanical Systems

Jerzy WarmiƄski is Professor and Head of Department of Applied Mechanics at Faculty of Mechanical Engineering, Lublin University of Technology, Poland. He obtained his PhD (1992) in mechanical engineering from Lublin University of Technology and DSc (2001) in mechanics from Cracow University of Science of Technology (AGH). In 2012 he earned the title of Professor from President of Poland. He is a member of the Committee on Mechanics of the Polish Academy of Sciences and a chairman of the Section of Dynamics.

He serves as an editorial or advisory board member in Nonlinear Dynamics (2010-2018), Journal of Sound and Vibration, Journal of Mechanical Engineering Science of Proc. of the Institution of Mechanical Engineers, Part C (associate editor 2008-2013), subject editor in Journal of Theoretical and Applied Mechanics, a member of the European Nonlinear Oscillations Conference Committee (ENOCC) and Technical Committee on Multibody Systems and Nonlinear Dynamics of the American Society of Mechanical Engineers (ASME).

His main research areas are nonlinear dynamics, nonlinear oscillations, bifurcations and chaos theory, nonlinear normal modes, dynamics and control of active structures, time delay systems, analytical and numerical methods in mechanics. He published as author or co-author 4 books and above 150 peer-reviewed journal papers on the mentioned topics and he organised several special issues on nonlinear dynamics.

Abstract...

A specific future of nonlinear systems is an existence a few solutions for the same set of structural parameters. A classical Duffing’s oscillator may serve as an example where three different solutions, two stable and one unstable, may exist in a certain frequency domain. However, if the Duffing oscillator is excited parametrically and in the same time externally, a number of solutions may increase up to five, as presented in [1]. The additional self-excitation creates quasi-periodic solutions which occur after Neimark-Sacker bifurcation [2].

The models govern by classical Duffing’s equation have just one equilibrium position, which is stable and then its potential function has just one minimum. Systems with more than one equilibrium belong to another group of the multi-stable structures. The multi-stability can be created by specific devices, for example by repulsing magnetic force. Such nonlinear force enables to modify a shape of a potential function and to get two or more potential wells. Another option is to add axial force to the structure which moves the vibrating system close to a buckling point with two equilibria (two potential wells). Such axial compression may be caused by axial mechanical loading or by increased temperature for example [3].

The composite technology offers new possibilities to create multi-stable structures [4]. The bistability, with an associated rapid jump from one to another equilibrium (so called snap-through effect) is attractive for a design of efficient energy harvesters [5]. Most of the published papers on bistable laminates are devoted to symmetric or almost symmetric configurations with free boundaries. A special design of a laminate shell based on an unique pseudo-conical shape, with asymmetric configuration of lamina is proposed in [4,5]. Depending on the assumed geometry two or even five stable equilibria can be obtained. In the present paper the unique nonlinear properties of the shell are investigated for local in-well oscillations and as well as for large oscillations with global cross-well dynamics, with the snap-through effect.

The main goal of this paper is to present the untypical nonlinear effects of multi-stable systems and their application to energy harvesting [5], morphing and control.

Acknowledgment

This research was funded in part by National Science Centre, Poland 2021/41/B/ST8/03190.


References

  1. WARMINSKI J: Frequency locking in a nonlinear MEMS oscillator driven by harmonic force and time delay International Journal of Dynamics and Control 3 (2), 122-136, 2015.
  2. Warminski J.: Nonlinear dynamics of self-, parametric, and externally excited oscillator with time delay: van der Pol versus Rayleigh models. Nonlinear Dynamics 99, 35-56, 2020.
  3. Manoach E., Warminski J., Kloda L., Warminska A., Doneva S., Nonlinear vibrations of a bi-material beam under thermal and mechanical loadings, Mechanical Systems and Signal Processing, 177, 1-21, 2022.
  4. Brunetti M., Mitura A., Romeo F., Warminski, J.: Nonlinear dynamics of bistable composite cantilever shells: an experimental and modelling study. Journal of Sound and Vibration 526 (2), 116779, 2022.
  5. Mitura, A., Brunetti, M., Kloda, L., Romeo, F., Warminski, J.: Experimental nonlinear dynamic regimes for energy harvesting from cantilever bistable shells. Mechanical Systems and Signal Processing 206 (9), 110890, 2024.

Professor Dora Karagiozova,

Institute of Mechanics, BAS, Bulgaria

Plenary Lecture: Energy absorption of lightweight materials and structures under dynamic loading

Dora Karagiozova is a professor of solid mechanics at the Institute of Mechanics, Bulgarian Academy of Sciences. She has also served as honorary research professor at the University of Cape Town, South Africa (2008-2012) and at the Wuhan Technological University, China (2016-2018). Her research work is mainly focused on the mathematical modelling and numerical simulation of structures under blast and impact including the mechanical characterization of cellular materials under quasi-static and dynamic loading. D. Karagiozova is a member of the editorial boards of the International Journal of Mechanical Sciences, International Journal of Impact Engineering, Latin American Journal of Solids and Structures and Journal of Theoretical and Applied Mechanics – BAS.

 

Abstract...

Man-made cellular materials with a large range of different topologies - honeycombs, open and closed cell foams, metal hollow spheres, micro-lattices, stacked origami, etc. - are widely used in various engineering applications, especially in the automotive, aerospace and defense industries. While the cellular materials would not be a competitor for load-bearing structural parts on their own due to their relatively low strength, they offer significant advantages when combined with other materials into a sandwich construction as the cellular materials they possess good energy absorption properties for very little weight penalty and relatively small force transfer through the structure. In particular, the dynamic compressive behavior of cellular materials is crucial to their applications in energy absorption and blast/impact protection.

In the lecture, the essential features of the response of metal-based cellular materials to impact loading based on an advanced theoretical description of the response of cellular materials with different configurations when using a continuum mechanics approach are highlighted. This approach relies on the one-dimensional stress wave propagation when using the actual experimentally derived stress-strain curve, characterizing a strain-hardening material, together with its Hugoniot representation. Examples are shown for the stress wave propagation in cellular materials with uniform density and gradient density when highlighting the difference between the continuous stress wave (a simple wave) and a wave of a strong discontinuity (shock wave). The application of the proposed theoretical approach is demonstrated on an experimentally tested structure under blast loading. The deformation mechanisms of materials which exhibit structural softening, such as out-of-plane loaded honeycomb, are discussed to reveal the importance of the materials topology for their dynamic compaction. It is shown that the dynamic out-of-plane compaction of honeycombs does not obey the law of shock wave propagation as the underpinning deformation mechanisms at the cell level govern the macroscopic response of the cellular materials.

Professor Giuseppe Rega,

Department of Structural and Geotechnical Engineering, Sapienza University of Rome, Italy

Closing Plenary Lecture:  Global Dynamics Perspective for the Analysis, Control and Safe Design in Macro- to Nano-Mechanics

Giuseppe Rega is Professor Emeritus, Sapienza University of Rome. Past Chairman of EUROMECH Nonlinear Oscillations Conference Committee and AIMETA (Italian Association Theoretical Applied Mechanics), Italian Representative at IUTAM General Assembly, Member of CISM Scientific Council. Was Chairman of Sapienza Ph.D. School in Structural and Geotechnical Engineering, and Committee of Italian Professors of Solid and Structural Mechanics.

Past Editor-in-Chief of Meccanica, has been/is Associate Editor/Advisor/Editorial Board Member of several Archival Journals. Organized many scientific events within EUROMECH, IUTAM, ASME, NNM, CISM, EURODYN and other societies. Plenary/Keynote Lecturer at a huge number of international conferences and many academic institutions.

First non-anglo-saxon recipient of ASME Lyapunov Award (2017). Birthday anniversaries honored with Special Issues of Nonlinear Dynamics (60th) and Int. J. Non-Linear Mech. (70th). Published more than 170 papers in 55 Archival Journals and nearly 85 Edited Volume Chapters. Edited 6 Books and 10 Archival Journals Special Issues.

Contributions to cable nonlinear dynamics, nonlinear oscillations, bifurcation and chaos in applied mechanics and structural dynamics, reduced-order modelling, control of oscillations and chaos, exploitation of global dynamics for engineering safety, smart materials, coupled oscillators, thermomechanical problems. Combined use of analytical, computational, geometrical and experimental techniques, to detect/characterize the variety of nonlinear/complex dynamic phenomena occurring in different engineering areas. Also active in structural architecture.

Abstract...

Global nonlinear dynamics has been evolving in a revolutionary way in the last two decades, with development of sophisticated techniques employing concepts/tools of dynamical systems, bifurcation, and chaos theory, and applications to a wide variety of mechanical/structural systems. Relevant achievements entail a substantial change of perspective in dealing with vibration problems, and are ready to affect meaningfully the analysis, control, and design of systems at different scales. After properly framing the subject within some main stages of developments of nonlinear dynamics in solid/structural mechanics, the lecture will focus on highlighting the role played by global analysis in unveiling the nonlinear response and actual safety of engineering systems in diverse environments. Reduced order models of macro/micro-structures will be considered, to address the following items.

  • Detecting effects induced in long-term dynamics by the coupling of mechanical (fast) and thermal (slow) fields.
  • Characterizing and quantifying main topological phenomena of global response in phase and parameter spaces.
  • Dynamical integrity to evaluate robustness and overall stability in mechanical/structural applications.
  • Exploiting global concepts/phenomena for control purposes.
  • Interpreting theoretical vs practical mismatches of global safety ensuing from real system disturbances.
  • Non-deterministic global framework: operator approaches to stochastic attractors and basins of attraction.
  • Enhanced load carrying capacity of systems/structures via a novel, global dynamics-informed, paradigm.
  • How facing the enormous complications of global dynamics for multidimensional systems.