Professor Matthew P. Cartmell Aerospace Centre of Excellence, Department of Mechanical & Aerospace Engineering, University of Strathclyde, Glasgow, G1 1XJ, Scotland, UK
Opening Plenary Lecture: Motorised momentum exchange space tethers: modelling of the three dimensional dynamics of asymmetrical motorised tethers
Prof. Cartmell worked as a research fellow at Edinburgh University from 1984-1986, after graduating with a PhD from there in 1984. He then held a series of permanent academic posts at Aberdeen, Swansea and Edinburgh Universities, before taking up the Chair of Applied Dynamics at Glasgow University in 1998. He then took up the James Watt Chair of Mechanical Engineering at Glasgow University in 2006 and, in September 2012, the Chair of Nonlinear Mechanics at the University of Sheffield. He is now the Professor of Nonlinear Dynamics at the University of Strathclyde. Matthew Cartmell is currently the Editor-in-Chief of the Journal of Sound and Vibration and former Editor-in-Chief of the Journal of Mechanical Engineering Science, Part C. Matthew Cartmell's research covers six main areas: Momentum exchange space tethers, Novel Propulsion concepts, Symbolic computational dynamics, Dynamics of smart systems, Mechanical energy harvesting and transmission, and the dynamics of parametric and nonlinear oscillating systems.
A large amount of work has been successfully carried out to date by the author and others on the modelling of symmetrical momentum exchange space tethers, and this has allowed some important insights into on-orbit propulsion performance. The incorporation of a prime mover such as a solar-electric drive motor into a momentum exchange tether introduces the potential for greatly enhanced performance over passive tethers. But so far the work done has concentrated solely on tethers which are symmetrical in the distribution of mass about the assumed geometrical centre, the point at which the motor drive location has been defined. This has operational relevance in that symmetry issues can be powerfully exploited for two-way interplanetary payload exchange, and so a tether that carries two payloads with identical mass properties, or one that has divested itself of both payloads simultaneously, can be readily applied to an ongoing continuous mission programme. However, there are occasions when a motorised momentum exchange tether may be forced to operate in an asymmetrical mode, where one of the two payloads is detached but the other remains attached. From a mission architecture and logistics point of view this scenario has already been accommodated, and a solution proposed, but from the perspective of the three dimensional orbital dynamics it has remained an unsolved problem until very recently. The work to be presented in this lecture will summarise the modelling of a symmetrical motorised tether and will also summarise the logistics of a two-way interplanetary freight mission on which this depends. It will then go on to examine those scenarios when asymmetry can occur and will show how very recent work has led to new models of the three dimensional orbital dynamics of tethers operating under these conditions. It will be shown that such tethers can indeed continue to be operated and that steps for mission recovery can be defined and proposed as a consequence of this further modelling.
Professor Anindya Chatterjee
Indian Institute of Technology (IIT) at Kanpur, India
Plenary lecture: A two-state hysteresis model obtained from a high-dimensional frictional system.
Anindya Chatterjee got his bachelor's degree in mechanical engineering from the Indian Institute of Technology (IIT) at Kharagpur, and his PhD from Cornell University. He has taught at the Indian Institute of Science at Bangalore and also at IIT Kharagpur and IIT Kanpur. Chatterjee's research interests are in the areas of dynamics, applied mechanics and applied mathematics. His prior research has included rigid body impact models, walking machines, rotors, vehicle dynamics, fatigue damage modeling, delay differential equations, parametrically forced systems including ion dynamics in Paul traps, fractional order derivatives, various linear and nonlinear vibration problems, material damping, and hysteresis models.
Rate-independent hysteresis in energy dissipation within many materials and structures has been empirically observed by many researchers over more than a century. In such materials and structures the use of viscous damping in vibrations is therefore incorrect in principle, although it is analytically convenient. In hysteresis, the load-displacement or stress-strain curve is irreversible and changes slope whenever the direction of loading is changed, leading to loops with sharp corners. Small reversals of loading within larger loading paths lead to minor loops in the load-displacement curve. Under complex loading, the load-displacement curve can have many loops within loops. One can attempt to describe the load-displacement curve in terms of evolution equations. In structural mechanics, the famous Bouc-Wen model has been used for decades to describe hysteresis. This model is a differential equation with one internal state, captures single loops well, but cannot capture minor loops. One can show that, in order to capture minor loops within such larger loops, the hysteresis model should have at least two internal states. In this talk, I will describe our mechanistic approach toward purposefully constructing a simple two-state model that captures such hysteresis loops. Our approach differs from other conceivable empirical approaches where ad hoc relations are guessed and shown to produce hysteresis loops. Here, we start with a physically based micromechanical model with many springs and sliding elements, i.e., a high dimensional frictional system resembling smaller systems studied by Iwan half a century ago. We first solve the resulting equations incrementally via the linear complementarity problem. Then, using new approximation methods suitable for such a system, we are able to reduce the order of the system to the theoretical minimum requirement of two internal states. This reduction involves identification of shape functions, use of a work inequality, a simple fortuitous approximation of a complicated dissipation function, solution of a slightly offbeat minimization problem, reduction of the resulting equations to easily tractable form, elimination of superfluous fitted parameters through coordinate changes, and finally, separation of the roles of the remaining fitted parameters through a combination of further analytical simplification and approximation. In summary, I will start with initial motivation, present the high dimensional model, and trace the route of reduction, approximation and simplification leading to a final novel and simple two-state hysteresis model.
Professor John Mottershead
University of Liverpool, UK
Plenary lecture: Progress in Stochastic Model Updating
John Mottershead has BSc and PhD degrees in Mechanical Engineering and was awarded the DEng degree by the University of Liverpool, where he is the Alexander Elder Professor in Applied Mechanics and Director of the Liverpool Institute for Risk and Uncertainty. His research interests include FE model updating, image processing of full-field vibration and strain data, active vibration control and servoaeroelasticity. He has published several hundred papers in international journals and conference proceeding and his industrial collaborations include, from the motor industry BMW, Fiat, Ford and Peugot-Citroen, and from the aerospace industries AgustaWestland Helicopters, Airbus UK and Rolls-Royce. He is the Editor-in-Chief of Mechanical Systems and Signal Processing.
Keywords: Stochastic model updating, parameter selection, covariance and interval methods, Bayesian inference, AIRMOD database
Deterministic model updating is now regularly applied to large scale industrial structures. However, it is well known that different analysts produce different finite element (FE) models, make different physics-based assumptions, and parameterise their models differently. Also, tests carried out on the same structure, by different operatives, at different times, under different ambient conditions produce different results. This provides the motivation for the presented work. Interval, perturbation (covariance) and Bayesian methods are described and new results are presented on the selection of updating parameters. The practical application of these techniques is demonstrated using the DLR AIRMOD structure, which was disassembled, reassembled and tested 130 times to produce a database of modal-test variability. The Bayesian updating procedure gives a measure of the most probable model whereas the covariance updating method is predicated on the assumption of Gaussian distributions. Interval model updating is generally the more conservative of the 3 methods. Updating equations produced by the sensitivity method are generally ill-conditioned requiring regularisation, which is applied automatically in Bayesian model updating. Covariance model updating can be carried out on a standard desk-top PC in a few minutes whereas Bayesian updating requires parallelised code on multiple processors and errors in surrogate models can affect the updated distributions.
Professor Marcelo Savi
Federal University of Rio de Janeiro, Brazil
Plenary lecture: Nonlinear dynamics of smart bioinspired systems
Marcelo A. Savi is Ph.D. in Mechanical Engineering and Professor at Federal University of Rio de Janeiro (COPPE/Poli - Department of Mechanical Engineering) where develops research and teaching activities, being the Head of the Center for Nonlinear Mechanics. He has published over 350 journal and conference papers. He wrote and translated 20 books/book chapters, being 4 complete. Several awards and distinctions were received including: COPPE Award Giulio Massarani of the Academic Merit; CAPES Award for the best PhD Thesis; CNPq Researcher level 1A; Scientist of Rio de Janeiro. He is actively involved as advisor of graduate and undergraduate students, summing more than 100 works. He has administrative experience as head of department, graduate coordinator, and university committees. Research interests are related to nonlinear mechanics where it should be highlighted smart material and structures; nonlinear dynamics, chaos and control; biomechanics and environmental systems.
Inspired by nature, researchers are trying to create systems and structures that present adaptive behavior according to its environment. The use of nature as an inspiration has the objective to extract design principles from biological systems. Among many options of smart sensors and actuators, shape memory alloys (SMAs), piezoelectric and magnetostrictive materials are some interesting options. Due to their remarkable properties, smart materials have been used in many areas of human knowledge. This seminar presents some smart material system applications and their thermomechanical behaviors. It is discussed constitutive models that explore phenomenological features of the thermomechanical response of smart materials. This constitutive model is employed in order to describe some interesting behaviors and potential applications of smart devices involving dynamical behavior. Adaptive structures and origami systems are discussed. In this regard, it should be highlighted their rich response including chaos and attractor multistability. Chaos control is also employed showing situations where tiny perturbations can avoid undesirable behaviors.
Professor Tomasz Kapitaniak
Lodz University of Technology, Poland
Plenary lecture: Transitions between different ringing schemes of the church bell
Professor Tomasz Kapitaniak is professor of theoretical and applied mechanics and head of the Division of Dynamics at Lodz University of Technology since 1992.. He was invited to deliver more than 100 plenary/symposia lectures and over 250 seminars and other talks worldwide. He is the member of editorial boards of a few journals and honorary editor of the International Journal of Bifurcation and Chaos. He has published 200 research papers in the renowned journals from JCR list, cited over 2000 times. His research is concentrated on nonlinear dynamics. The development of nonfeedback methods for chaos control, identification and description of new types of bifurcations, identification of the synchronization mechanism in coupled mechanical oscillators and the explanation of the origin of randomness in mechanical system are among his most important scientific discoveries. In 2013 he has been elected the member of the Polish Academy of Sciences. He has got Doctor Honoris Causa degrees at the Saratov State University (Russia) and Lublin University of Technology (Poland) respectively in 2001 and 2014.
We present a hybrid model of church bell. The dynamical system of yoke-bell-clapper is nonlinear and discontinuous. We use the Lagrange equations of the second type to derive formulas that describe the system's motion. The energy between the bell and the clapper is transmitted via impacts, here modeled using a coefficient of energy restitution. The values of the system's parameters have been determined basing on the measurements of the biggest bell ‘‘The Heart of Lodz’’ in the Cathedral Basilica of St Stanislaus Kostka, Lodz, Poland. Using the same bell we also validate the model by comparing the results of numerical simulations with experimental data. The presented results show that the described model is a reliable predictive tool which can be used both to simulate the behavior of the existing yoke-bell-clapper systems as well as to design the yokes and predict the motion of new bells.
Professor Haiyan Hu
Beijing Institute of Technology, China
Closing Plenary Lecture: Recent Advances in Flutter Analysis and Control of Aircraft
Dr. Haiyan Hu is Professor of Applied Mechanics at Beijing Institute of Technology, China. He has made recognized contributions to the dynamics and control of aerospace systems, such as nonlinear vibration mountings, adaptive wings for active flutter suppression, tethered satellites and deployable space structures. He authored and co-authored two monographs and more than 200 papers, which have been cited over 6,000 times. Out of his achievements, Prof. Hu was elected the Fellow of Chinese Academy of Sciences (CAS) and the Fellow of the Third World Academy of Sciences (TWAS). In addition, He was conferred on the Honorary Doctor by Moscow State University, Russia and University of Reading, UK, respectively.
Active control has witnessed a great change in the design of aircraft structures, from the passive design of increasing structure stiffness to the active design in view of control configured aircraft. The idea of active design does not avoid the aeroelastic problem, but adjust the structural aeroelasticity via active control so as to reduce the structure weight and optimize the aircraft performance. The aeronautical community has made great efforts to study the corresponding aeroelastic problems and gain an insight into the coupling among aircraft structure, aerodynamics and active control. Most studies, however, have been based on the simplified models. As such, it is difficult to apply the research achievements to aeronautical industry.
This lecture presents the recent advances in the dynamic problems of aircraft aeroelasticity including the aerodynamic nonlinearity from supersonic flow, the backlash nonlinearity from multiple control surfaces, the instability induced by time delays in control loop, the active flutter suppression when the above nonlinearities and time delays appear, as well as the validation of wind tunnel tests. The lecture focuses on the new approaches proposed at the author’s lab, and the corresponding numerical simulations and wind tunnel tests over the past decade. Finally, the lecture addresses a number of open problems related to the aeroelastic analysis and control.