报告题目1：Non-smooth Dynamics of a Vibroimpact Pair---Modeling and Applications

报告题目2：Non-smooth Dynamics of a Vibroimpact Pair---Theoretical analysis and Bifurcations

报告人：Daniil Iurchenko，University of Southampton，

照片：

邀请人：黄冬梅

报告时间：2023年4月3日，14:00-15:00(第一场)；15:00-16:00(第二场)

报告地点：信远楼II区206

报告人简介：Dr. Iurchenko is an expert in the area of Nonlinear Stochastic Dynamics and Control, Vibrations mitigation, mathematical and experimental modelling of complex dynamic system with application in railway and automotive engineering, renewable wave and tidal energy, as well as energy harvesting using soft electroactive polymers. He has published over 150 scientific publications including peer-reviewed journals and conference proceedings. He is an Editorial board member of Mechanical Systems and Signal Processing, Int. J. of Dynamics and Control, Vibrations. Currently he holds EPSRC grant on the development of soft materials vibroimpact energy harvesting device and the International Exchange Royal Society grant with China.

报告摘要1：This presentation is focused on the analysis of a VI impact pair, which is an illustrative representative of non-smooth dynamical systems. Such a system was proposed to be used as an energy harvesting device consisting of a ball travelling freely inside a harmonically excited capsule. Both sides of this capsule are covered by dielectric elastomer with compliant electrodes, organising a variable capacitance capacitor. Deformation of the elastomer leads to changes in capacitance and therefore ability to harvest energy. The considered vibroimpact system can be studied exactly analytically using maps. This allows to study smooth and non-smooth bifurcations and their interplay in a canonical model of an impact pair. While the sequences of bifurcations have been studied extensively in single-degree-of-freedom impacting models, there are limited results for two-degree-of-freedom impacting systems such as the impact pair.

报告摘要2：This presentation is using an exact analytical solution between the impacts and the stability analysis, we obtain sequences of period doubling and fold bifurcations together with grazing bifurcations. Using this analysis, we identify the bifurcations on unstable or unphysical solutions branches, which we term ghost bifurcations. The presentation addresses the mystery of why sometimes we observe grazing and sometimes PD transitions, and how the ghost bifurcations, not observed numerically or experimentally, can influence the birth or death of complex behaviours. We also discuss the influence of asymmetric values of the restitution coefficients and targeted energy transfer in such systems.