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SUMMARY:MechE Colloquium: Toward a mechanistic understanding of adhesive w
 ear
DTSTART:20201117T121500
DTEND:20201117T131500
DTSTAMP:20260528T175105Z
UID:85178a724efba55ae3a1f808581bac1e60b43e8aaff37309ed1936d6
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Jean-François Molinari\, Computational Solid Mechanics 
 Laboratory\, EPFL School of Architecture\, Civil and Environmental Enginee
 ring (ENAC)\, Civil Engineering Institute (IIC)\nAbstract:\nWe discuss rec
 ent advances in developing a fundamental\, mechanistic\, understanding of 
 the evolution of surface roughness of solids during dry sliding. The time 
 evolution of surface roughness is little understood although it crucially 
 impacts friction and wear. Engineering wear models are for the most part e
 mpirical\, and the development of physics-based predictive models will req
 uire intensive experimental\, theoretical\, and numerical research at vari
 ous scales. This presentation focuses on atomistic and mesoscale numerical
  modeling of rough solids under sliding in the presence of adhesive wear m
 echanisms.\n\nIn the first part\, we summarize our attempts at capturing d
 ebris formation at micro contacts using atomistic potentials [1\,2]. We sh
 ow that\, in the simple situation of an isolated micro contact\, the final
  debris size scales with the maximum junction size attained upon shear. Th
 is permits to draw analogies with Archard adhesive wear model [3]. In the 
 second part\, this single-asperity understanding is incorporated in a meso
 scale model [4]\, which aims at estimating from first principles the wear 
 coefficient\, a notoriously little understood parameter in wear models. We
  estimate the amount of volume of debris formed for a given applied load\,
  using the probability density of micro contact sizes. A crucial element o
 f this mesoscale model is the distribution of surface heights\, which shou
 ld evolve as wear processes take place. This leads us\, in the final part\
 , to a discussion of recent simulations aiming at understanding the long-t
 erm evolution of surface roughness. These long time scales simulations rev
 eal the emergence of self-affine fractal surfaces irrespective of the init
 ial surfaces characteristics [5].\n\nReferences\n[1]          Agh
 ababaei\, R.\, Warner\, D.H.\, Molinari\, J.F.\, “On the debris-level or
 igins of adhesive wear”\, PNAS\, 114(30)\, pp. 7935-7940 \, 2017.\n[2] 
          Aghababaei\, R.\, Warner\, D.H.\, Molinari\, J.F.\, “Cr
 itical length scale controls adhesive wear mechanisms”\, Nature Comm.\, 
 11816\, 2016.\n[2]          Archard\, J.F.\, “Contact and rubbi
 ng of flat surfaces”\, J. of Applied Physics\, 24\, 981\, 1953.\n[4]  
         Frérot\, L.\, Aghababaei\, R.\, Molinari\, J.F.\, “On un
 derstanding the wear coefficient: from single to multiple asperities conta
 ct”\, J. Mech. Phys. Solids\,               114\, pp. 172-1
 84\, 2018.\n[5]          Milanese\, E. Brink\, T.\, Aghababaei\, 
 R.\, Molinari\, J.F.\, “Emergence of self-affine surfaces during adhesiv
 e wear”\, Nature Communications\, 10\, 1116\,              
  2019.\n\nBio:\nProfessor J.F. Molinari is the director of the Computation
 al Solid Mechanics Laboratory (http://lsms.epfl.ch) at EPFL\, Switzerland.
  He holds an appointment in the Civil Engineering Institute\, which he dir
 ected from 2013 to 2017\, and a joint appointment in the Materials Science
  Institute. He started his tenure at EPFL in 2007 and was promoted to Full
  Professor in 2012. \n \nJ.F. Molinari graduated from Caltech\, USA\, in
  2001\, with a M.S. and Ph.D. in Aeronautics. He held professorships in se
 veral countries besides Switzerland\, including the United States with a p
 osition in Mechanical Engineering at the Johns Hopkins University (2000-20
 06)\, and France at École Normale Supérieure Cachan in Mechanics (2005-2
 007)\, as well as a Teaching Associate position at the École Polytechniqu
 e de Paris (2006-2009). \n \nThe work conducted by Prof. Molinari and hi
 s collaborators takes place at the frontier between traditional discipline
 s and covers several length scales from atomistic to macroscopic scales. O
 ver the years\, Professor Molinari and his group have been developing nove
 l multiscale approaches for a seamless coupling across scales. The activit
 ies of the laboratory span the domains of damage mechanics of materials an
 d structures\, nano- and microstructural mechanical properties\, and tribo
 logy. Prof. Molinari was a recipient of an ERC Starting Grant award in 200
 9.
LOCATION:Zoom https://epfl.zoom.us/s/87688979401
STATUS:CONFIRMED
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