000202204 001__ 202204
000202204 005__ 20190509132514.0
000202204 0247_ $$2doi$$a10.5075/epfl-thesis-6443
000202204 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis6443-3
000202204 02471 $$2nebis$$a10256871
000202204 037__ $$aTHESIS
000202204 041__ $$aeng
000202204 088__ $$a6443
000202204 245__ $$aModelling Plasticity in Nanoscale Contact
000202204 269__ $$a2014
000202204 260__ $$bEPFL$$c2014$$aLausanne
000202204 336__ $$aTheses
000202204 502__ $$aProf. I. Botsis (président) ; Prof. J.-F. Molinari (directeur) ; Prof. W. Curtin,  Prof. N. Fillot,  Prof. D. Warner (rapporteurs)
000202204 520__ $$aThe problem of mechanical contact is a truly multiscale one. Atomistic effects that violate continuum theory dominate the deformations of contacting asperities, while the interactions between distant asperities occur through long-range elasticity. This thesis concentrates on the numerical modelling of nanoscale frictional contact between crystalline metals by using both single-scale atomistic methods and improving concurrent multiscale methods. A novel approach to quantify frictional work and the energy associated with plastic activity in \md simulations is presented. In combination with a statistical criterion to determine the significance of simulation box size, microstructure and sliding rate effects on the frictional quantities such as the friction coefficient and stored plastic energies, the method is used in a large parametric molecular dynamics study of single-asperity nanoscratch on monocrystalline and polycrystalline aluminium substrates. Some fundamental differences in the friction mechanisms between monocrystalline and polycrystalline substrates are presented. The study shows the limitations of single-scale modelling and highlights the importance of developing appropriate multiscale methods for nanoscale plasticity. One such method is the Coupled Atomistics and Discrete Dislocations (CADD), which previously only existed for two-dimensional problems. A three-dimensional version of the CADD method is presented theoretically as well as a detailed practical road map for its efficient implementation. The foundations of three-dimensional CADD are presented using practical test cases. CADD avoids ghost forces at the coupling interfaces through displacement-coupling. I reveal that such displacement-coupling methods generally exhibit an inherent dynamic instability which makes them particularly ill suited for finite temperature calculations, despite their wide use. The instability is analysed in detail. Multiple remedies to manage it are discussed and a fundamental solution to the underlying problem is presented in the form of a new coupling method.
000202204 6531_ $$aComputational Materials Science
000202204 6531_ $$aComputational Contact Mechanics
000202204 6531_ $$aNanotribology
000202204 6531_ $$aPlasticity
000202204 6531_ $$aConcurrent Multiscale Modelling
000202204 6531_ $$aMolecular Dynamics
000202204 6531_ $$aDiscrete Dislocation Dynamics
000202204 6531_ $$aFinite-Element method
000202204 700__ $$0243323$$g160169$$aJunge, Till
000202204 720_2 $$aMolinari, Jean-François$$edir.$$g178549$$0243317
000202204 8564_ $$uhttps://infoscience.epfl.ch/record/202204/files/EPFL_TH6443.pdf$$zn/a$$s12716396$$yn/a
000202204 909C0 $$xU10232$$0252179$$pLSMS
000202204 909CO $$pthesis-bn2018$$pDOI$$pENAC$$ooai:infoscience.tind.io:202204$$qDOI2$$qGLOBAL_SET$$pthesis
000202204 917Z8 $$x108898
000202204 917Z8 $$x108898
000202204 918__ $$dEDME$$cIIC$$aENAC
000202204 919__ $$aLSMS
000202204 920__ $$b2014$$a2014-10-31
000202204 970__ $$a6443/THESES
000202204 973__ $$sPUBLISHED$$aEPFL
000202204 980__ $$aTHESIS