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SUMMARY:Friction damping in structural dynamics: from fundamental understa
 nding to physics-based machine learning identification - Dr Luca Marino\, 
 TU Delft\, Netherlands
DTSTART:20241115T160000Z
DTEND:20241115T170000Z
UID:TALK219850@talks.cam.ac.uk
CONTACT:46601
DESCRIPTION:Structural joints characterised by moving surfaces are present
  in most engineering structures. Idenfying the nonlinear forces generated 
 by friconal interfaces\, as well as understanding how their damping effect
 s can be exploited to achieve vibraon reducon and energy dissipaon\, are a
 mong the present crical challenges in structural dynamics. Moreover\, the 
 unpredicted nonlinear behaviour induced by fricon can lead to undesirable 
 effects\, such as stuck contacts\, sck-slip\, excessive oscillaons and eve
 n unexpected failures. Predicng the nonlinear response of fricon damped sy
 stems is therefore essenal to develop robust designs and efficient monitor
 ing strategies. Nonetheless\, the analysis and idenficaon of these systems
  is complicated by the nonlinear and nonsmooth nature of the friconal forc
 es\, which is responsible for the generang sharp variaons and mulple moon 
 regimes in their dynamic response. \n\nThis contribuon deals with three ma
 jor challenges: (i) the derivaon of analycal soluons for the response of d
 iscrete mechanical systems with Coulomb fricon\, and the predicon of their
  moon regimes\; (ii) the development of an experimental framework for repr
 oducing and validang the proposed mathemacal soluons\; (iii) the formulaon
  of a physics-based machine learning approach for the idenficaon of fricon
 al systems. \n\nMathemacal soluons are obtained for the steady-state respo
 nse of single- and mul-degree-offreedom (DOF) systems with a fricon contac
 t to harmonic excitaon. The derived formulaons also enable the invesgaon o
 f the dynamic behaviour of systems with oscillang contacng parts and/or di
 fferent forms of damping. The results include the analycal predicon of the
  moon regimes (connuous\, sck-slip\, permanent scking) and the displacemen
 t transmissibility curves resulng from varying system parameters.\n \nThe 
 experimental invesgaon is performed on shear-frame setup with a brass-to-s
 teel contact\, able to reproduce the behaviour of single- and 2-DOF system
 s in contact with a fixed or oscillang wall. Tests run at different excing
  frequencies and fricon force amplitudes were able to closely reproduce th
 e theorecal results\, showing that Coulomb model can be used\, in most con
 dions\, for describing the dynamic behaviour of structures with a metal-to
 -metal contact. \nThe proposed idenficaon method combines a parally-known 
 physics-based model of the system with noisy measurements of its response 
 in a switching Gaussian process (GP) latent force model\, where mulple GPs
  are used to model the nonlinear force across different moon regimes and a
  reseng model to generate disconnuies. Regime transions and disconnuies ar
 e inferred in a Bayesian manner\, along with the nonlinear force\, and can
  be used to implement forward models able to make reliable response predic
 ons. \n
LOCATION:JDB Seminar Room\, CUED
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