Random Vibrations with Impacts

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This research project deals with the development of methods and procedures for predicting response of vibroimpact systems to random excitation. Typical fields of applications include Engineering (response of moored bodies to ocean waves) and Power Engineering, particularly Nuclear (flow- induced vibrations of fuel bundles within channelling tubes; and of heat exchanger tubes impacting against support plates). Other potential applications include Railway Machinery (vehicle dynamics with impact-type wheel/rail interactions) and Rotating Machinery (gearboxes with reversals of motion). A quasiconservative stochastic averaging method is used together with a Fourier series expansion in a `rapid` time, within a response cycle. In addition, a new approximation procedure is developed and evaluated which is based on the dominating contribution of the impacts into overall spectral density of response acceleration for lightly damped systems. The model of a periodic excitation with random phase modulation is used to predict subharmonic response of moored offshore platforms to ocean waves, and to predict transitions between planar and whirling flow-induced vibrations of tubes in heat exchangers. Fundamental theory of nonlinear vibration and control would benefit through new analytical methods and procedures developed during the course of this research and some new specific solutions obtained for (strongly nonlinear) systems. Also, this research will assist in response prediction and control, as well as predicting and/or testing reliability and developing design guidelines for systems in offshore and power engineering.