Exploring and exploiting complex nonlinear dynamical states in friction-excited mechanical systems

从汽车到航空航天工程，FIV在不同的工业应用中都是一个主要问题。尽管在最近几年投入了巨大的努力，FIV仍然被定义为“随机的”、“低重复的”、“反复无常的”。FIV数值模拟和理论模拟的最新进展表明，摩擦影响的动力系统可能经历多种动力学状态，特别是空间局域振动态、粘滑/全滑移传播前沿和粘滑脉冲。这些过渡状态在FIV发展中的作用在文献中往往被忽视，相反，文献主要集中在摩擦系统的静止的、全球的行为上。我们建议详细研究FIV的空间局域化现象及其作为粘滑前沿或脉冲在界面上的传播。实验中观察到的“随机性”，实际上可能是因为我们缺乏对摩擦系统在不同过渡状态的瞬变过程中如何演变的理解。我们将集中讨论摩擦激励下的离散规则结构。前两个目标和工作包旨在研究和表征局域态和传播态的存在范围、稳定性、传播速度、对系统参数的敏感性和对摩擦定律的敏感性。第三个目标和相应的工作包旨在利用观察到的非线性状态。我们将重点研究选择适当的动力学状态以获得所需的摩擦系数和耗散行为的可能性。对于申请者来说，这是一个独一无二的机会，可以开始一项更独立的研究，并拓宽他在TUHH动力学组工作的摩擦激励动力系统方面的知识。他在接触力学和非线性动力学方面的背景将对面对这一具有挑战性的项目至关重要。

FIV represent a major problem in different industrial applications, from the automotive to the aerospace engineering. Despite the great effort that has been invested in the recent years FIV are still defined "random", "low repeatable", "capricious". The recent advances in numerical and theoretical modelling of FIV show that friction affected dynamical systems may experience a multitude of dynamical states, in particular spatially localized vibrating states, stick-slip/full-slip propagating fronts and stick-slip pulses. The role that those transitory states play in the development of FIV has been often neglected in the literature, which, instead, has focused mostly on the stationary, global behaviour of frictional systems. We propose to study in detail the phenomenon of spatial localization of FIV and their propagation at the interface as stick-slip fronts or pulses. The experimental observed “randomness”, in fact, may be caused by our lack of understanding of how frictional systems evolve during the transients through different transitory states. We will focus on friction-excited discrete regular structures. The first two objectives and workpackages aim at studying and characterizing the localized and the propagating states in terms of region of existence, stability, velocity of propagation, sensitivity to system parameters and to the friction law. The third objective and corresponding workpackage aim at exploiting the observed nonlinear states. We will focus on the possibility of selecting the proper dynamical state to obtain the desired friction coefficient and dissipative behaviour. This "first-time" proposal is for the applicant a unique opportunity to start a more independent research and broaden his knowledge in friction-excited dynamical systems working in the Dynamics Group at TUHH. His background in contact mechanics and non-linear dynamics will be of crucial importance to face this challenging project.