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SUMMARY:Dynamic Response of Coatings on Substrates Subjected to Impulse Lo
 ading - Professor Matthew Begley\, Mechanical Engineering Materials Univer
 sity of California\, Santa Barbara
DTSTART:20140814T130000Z
DTEND:20140814T140000Z
UID:TALK53784@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:Femtosecond laser pulses with low energy can be used to precis
 ely debond the interface between oxide films and substrates\, which create
 s novel opportunities to characterize the properties of the film and the i
 nterface between the film and substrate.  This talk will describe theory a
 nd experiments that establish a framework that relates laser pulse paramet
 ers to film deformation\, which can be used to infer coating/interface pro
 perties from experiments\, or design experimental protocols that produce w
 ell defined interface flaws for subsequent testing.  First\, an analytical
  model will be used to highlight two (apparently) underappreciated aspects
  of the problem: (i) the time-scale of the laser pulse is much shorter tha
 n that of the inertial time-scale of the film\, such that the details of t
 he pressure generated by the pulse are largely immaterial (greatly simplif
 ying the problem) and (ii) the inertial contribution to the energy release
  rate can be substantial\, with important implications for reliability in 
 this and other dynamic scenarios (e.g. foreign object damage). The model w
 ill be used to generate regime maps that indicate failure modes as a funct
 ion of pulse characteristics and film properties\, which will be shown to 
 be in good agreement with experiments. Second\, the talk will present a br
 ief discussion of several facets of dynamic debonding that can only be cap
 tured numerically\, notably those relating to crack arrest after dynamic i
 nitiation. Illustrative simulations will be presented of such phenomena\, 
 which were generated using an explicit discrete element method with widely
  embedded cohesive zones.  The simulations demonstrate that it is possible
  to trigger dynamic kinking out of the interface (thus leading to a spalle
 d section of film)\, even when quasi-static calculations suggest otherwise
 .
LOCATION:Oatley Seminar Room\, Department of Engineering
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