Engineering Applications of Non-smooth Dynamics Marian Wiercigroch and Ekaterina Pavlovskaia Abstract. This chapter introduces and discusses practically important concept of non-smooth dynamical systems, which are very common in engineering applica- tions. Mathematically, such systems can be considered as piecewise smooth and therefore their global solutions are obtained by stitching local solutions, which are easy to develop by standard methods. If a dynamical system is piecewise linear then an implicit global analytical solution can be given, however the times when non-smoothness occurs have to be determined first. This leads to a set of nonlin- ear algebraic equations. To illustrate the non-smooth dynamical systems and the methodology of solving them, three mechanical engineering problems were studied. Firstly, a vibro-impact system in a form of moling device was modelled and anal- ysed to understand how the progression rates can be maximised. For this system, periodic trajectories can be reconstructed as they go through three linear subspaces (no contact, contact with progression and contact without progression), and using combination of analytical and numerical methods the optimal range of the system parameters can be identified. In the second application the influence of opening and closing of a fatigue crack on the system dynamics was investigated. Specifically, a novel apparatus to induce aperiodic loading to a specimen with a fatigue crack was studied. It was shown experimentally that fatigue life can be reduced few times if the sample is loaded aperiodically. The analysis of the developed mathematical model shown that as a crack grows linearly before reaching its critical value, the response of the system remains periodic. When its size exceeds the critical value, the system behaviour becomes chaotic and then the crack growth increases exponentially. This phenomenon can be used in structural health monitoring. The last problem comes from rotordynamics, where nonlinear interactions between the rotor and the snubber Marian Wiercigroch · Ekaterina Pavlovskaia Centre for Applied Dynamics Research, School of Engineering, Aberdeen University, King’s College, AB24 3UE, Aberdeen, Scotland, UK e-mail: {m.wiercigroch,e.pavlovskaia}@abdn.ac.uk J. Warminski et al. (Eds.): Nonlinear Dynamic Phenomena in Mechanics, SMIA 181, pp. 211–273. springerlink.com © Springer-Verlag Berlin Heidelberg 2012