Plastic response of surface asperities during contact loading
Lucia Nicola (Delft), R.-J. Dikken (TU Delft), F Sun (TU Delft)
Discrete Dislocation Plasticity
Tue 10:45 - 12:15
RI Hall 108
The importance of plasticity in rough surface contact and friction is not yet completely understood. Established statistical contact models, like Persson’s [1] and Mu ser’s [2], simply neglect plasticity. Yet they predict rather large pressures, which suggest that yield should have locally taken place. However, because of the size dependence of plasticity in small structures it is difficult to predict at which pressure the yield of surface asperities is expected to occur. This work aims at understanding what is the effect of size-dependent plasticity on single and multiasperity contacts during flattening and shearing. To this aim we perform two dimen- sional discrete dislocation plasticity simulations of the type proposed by Van der Giessen and Needleman [3]. Dislocations are modeled as line singularities in an otherwise isotropic linear elastic medium. Constitutive rules are supplied for the glide of dislocations as well as their generation, annihilation and pinning at point obstacles. Results highlight the effect on contact pressure and shear stress of asperity dimensions and of the spacing between neighboring asperities. Plasticity in the bulk region underneath the asperity is found to play an essential role in the mechanical response of both single and multi- asperities. [1] B.N.J. Persson, J. Chem. Phys. 115, 3840–3861 (2001) [2] M.H. Mueser, Phys. Rev. Lett. 100, 055504 (2008) [3] E. Van der Giessen and A. Needleman, Modelling Simul. Mater. Sci. Eng. 3 689-735 (1995)