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SUMMARY:Multi-scale computational-experimental analysis of the mechanics o
 f interfaces - Prof Marc Geers\, TU Eindhoven
DTSTART:20120210T140000Z
DTEND:20120210T150000Z
UID:TALK32959@talks.cam.ac.uk
CONTACT:Anna Walczyk
DESCRIPTION:Interfaces are omnipresent in most engineering materials and s
 tructures across the scales\, and\nthey have a major impact on the resulti
 ng mechanical properties\, both in the positive and the\nnegative sense. C
 onsiderable research efforts are nowadays focused on the adequate computat
 ional\ndescription of the interface\, which has to account for its differe
 nt constitutive behaviour modes\nat each of the scales. At the level of mi
 cro-scale deformation mechanisms these modes typically\nare: constraining 
 deformation (hard surface coatings\, interfaces in precipitation strengthe
 ned alloys)\,\nabsorbing deformation (decohesion and delamination)\, trans
 mitting deformation (plastic slip\nthrough grain boundaries). The role of 
 external and internal boundaries is even more dominant in\nmicromechanical
  systems\, where the surface-to-volume ratio changes drastically. Ample re
 search\nefforts are being initiated in the field to reveal the mechanical 
 behaviour of interfaces and surfaces\nacross the scales\, whereby the expe
 rimental analysis and the computational modelling thereof is\na prime goal
 .\nThis presentation addresses trends and challenges in the computational-
 experimental analysis\nof the mechanics of interfaces\, from different per
 spectives:\n-Cohesive interfaces: Cohesive zones are by now a classical to
 ol to describe one of the particular\nbehaviour modes of interfaces\, domi
 nated by decohesion and delamination. In the\ncontext of this wide spread 
 field of interface mechanics\, emphasis is put on a few particular\nissues
 :\n   - Large deformation aspects\n   - Numerical-experimental identificat
 ion of cohesive zone parameters\n   - Quasi-brittle interfaces\, involving
  an extreme discretization sensitivity\n- Intrinsic multi-scale aspects: T
 he cohesive zone concept lumps all deformation in the interfacial\ndecohes
 ion plane. The limitations thereof are not always properly understood\, an
 d will\nbe illustrated with a particular example. These limitations call f
 or an extended interfacial\ndescription\, in which novel multi-scale metho
 ds play an important role.\nMulti-scale characterization of delaminating p
 olymer-metal interfaces [image]\n- Constraining interfaces: Compatible int
 erfaces will naturally induce a constraint through\nthe coarse-scale elast
 ic fields. Less obvious are the resulting constraints acting on the micros
 cale\ncarriers of deformation and the resulting coarse grained impact ther
 eof. This holds\nparticularly for plastic slip in metals\, as occurring at
  grain boundaries\, phase boundaries\,\noxide layers\, coatings\, etc. Thi
 s problem reveals the intrinsic role of discreteness and shows a\nrigorous
  link with strain gradient plasticity models\, whereby its physical justif
 ication becomes\nmore natural.\n- Transmitting interfaces: In some particu
 lar cases\, fine scale deformation carriers are able\nto cross the interfa
 ce. This is particularly relevant for interfaces joining materials with\ns
 imilar atomic or microstructures and similar deformation carriers\, e.g. d
 islocation-based\nslip in single phase or multi-phase polycrystals. A simp
 le grain boundary is the most typical\nexample\, and proper constitutive e
 quations to describe the physical phenomena accurately\nare still lacking.
 \n- Size effects resulting from interfaces and surfaces: Interfaces and bo
 undaries in microelectronics\nand miniaturized systems are intrinsically i
 mportant\, for which the typical size\nof the material’s microstructure 
 is no longer negligible with respect to the component or\nstructural size.
  As a result\, characteristic size effects emerge.
LOCATION:Department of Engineering - LR6
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