000202843 001__ 202843
000202843 005__ 20180317092619.0
000202843 0247_ $$2doi$$a10.1073/pnas.0900804106
000202843 022__ $$a0027-8424
000202843 037__ $$aARTICLE
000202843 245__ $$aEngineering size-scaling of plastic deformation in nanoscale asperities
000202843 260__ $$c2009
000202843 269__ $$a2009
000202843 336__ $$aJournal Articles
000202843 520__ $$aSize-dependent plastic flow behavior is manifested in nanoindentation, microbending, and pillar-compression experiments and plays a key role in the contact mechanics and friction of rough surfaces. Recent experiments using a hard flat plate to compress single-crystal Au nano-pyramids and others using a Berkovich indenter to indent flat thin films show size scaling into the 100-nm range where existing mechanistic models are not expected to apply. To bridge the gap between single-dislocation nucleation at the 1-mu m scale and dislocation-ensemble plasticity at the 1-mu m scale, we use large-scale molecular dynamics (MD) simulations to predict the magnitude and scaling of hardness H versus contact size l(c) in nano-pyramids. Two major results emerge: a regime of near-power-law size scaling H approximate to l(c)(-eta) exists, with eta(MD) approximate to 0.32 compared with eta(expt) approximate to 0.75, and unprecedented quantitative and qualitative agreement between MD and experiments is achieved, with H(MD) approximate to 4 GPa at l(c) approximate to 36 nm and H(expt) approximate to 2.5 GPa at l(c) = 100 nm. An analytic model, incorporating the energy costs of forming the geometrically necessary dislocation structures that accommodate the deformation, is developed and captures the unique magnitude and size scaling of the hardness at larger MD sizes and up to experimental scales while rationalizing the transition in scaling between MD and experimental scales. The model suggests that dislocation-dislocation interactions dominate at larger scales, whereas the behavior at the smallest MD scales is controlled by nucleation over energy barriers. These results provide a basic framework for understanding and predicting size-dependent plasticity in nanoscale asperities under contact conditions in realistic engineered surfaces.
000202843 6531_ $$aatomistics
000202843 6531_ $$aatomistic simulation
000202843 6531_ $$acontact
000202843 6531_ $$acrystal plasticity
000202843 6531_ $$adislocation interactions
000202843 6531_ $$aenergy-balance criterion
000202843 6531_ $$alength
000202843 6531_ $$amechanical-properties
000202843 6531_ $$ananoindentation
000202843 6531_ $$aplasticity
000202843 6531_ $$ascales
000202843 6531_ $$asingle
000202843 6531_ $$asize-effects
000202843 6531_ $$astrain gradient plasticity
000202843 6531_ $$asurfaces
000202843 6531_ $$athin-films
000202843 700__ $$aWard, D. K.
000202843 700__ $$aFarkas, D.
000202843 700__ $$aLian, J.
000202843 700__ $$0246474$$aCurtin, W. A.$$g211624
000202843 700__ $$aWang, J.
000202843 700__ $$aKim, K. S.
000202843 700__ $$aQi, Y.
000202843 773__ $$j106$$q9580-9585$$tProceedings of the National Academy of Sciences of the United States of America
000202843 909CO $$ooai:infoscience.tind.io:202843$$particle$$pSTI
000202843 909C0 $$0252513$$pLAMMM$$xU12614
000202843 937__ $$aEPFL-ARTICLE-202843
000202843 970__ $$award_engineering_2009/LAMMM
000202843 973__ $$aOTHER$$rREVIEWED$$sPUBLISHED
000202843 980__ $$aARTICLE