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Title: Prediction and sensitivity of friction-induced vibration
Author: Butlin, T. S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2008
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A simplified system is studied analytically, numerically and experimentally. Predictions are based on a linear stability analysis of two subsystems coupled by friction at a sliding point contact. The model describes any two such linear subsystems, though is predominantly discussed in terms of vehicle brakes. As an example of its generality, it is shown to be equivalent to machine tool vibration. Representative uncertainties of the system dynamics are shown to be significant enough to affect whether or not the model predicts instability. The reliability of predictions are assessed systematically. The validity of limited bandwidth approximations to wide band-width models is tested: the convergence behaviour is non-trivial. While inclusion of sufficient bandwidth generally results in convergence, individual modes can sometimes be important. A first-order perturbation analysis is carried out in order to provide a practical estimate of error bounds for predictions. An extensive experiment was carried out using a pin-on-disc test rig to quantify uncertainty, assess repeatability and investigate whether high sensitivity could be experimentally observed. Repeated transfer function measurements of the uncoupled subsystems were made of two fundamentally different pin assemblies, symmetrical and asymmetrical, in the presence of different perturbation masses. Sliding contact tests were carried out with the aim of generating a large number of squeal initiations. Their growth rates and frequencies were estimated. This allowed a direct comparison of predictions with experimental results, enabling informed development of the modelling details. There was compelling evidence that both contact stiffness and a velocity-dependent coefficient of friction were essential features of the model to predict observed instabilities.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available