[SY-L2] Dislocations associated with stick-slip friction of lubricants in boundary lubrication
Improved understanding of squeezing and frictional behaviors of lubricant films under extreme confinement at nanometer scales can lead to strategies for preventing surface failure and efficient energy usage. Shearing of a solidified simple nonpolar film under nanoconfinement is studied by using a liquid-vapor molecular dynamics simulation method. We find that, in contrast with the shear melting and recrystallization behavior of the solidlike phase during the stick-slip motion, interlayer slips within the film and wall slips at the wall-film interface are often observed. The ordered solidified film is well maintained during the slip. However, repeated film dilation and collapse of the lubricant film during the stick-slip friction are observed, which is associated with the nucleation, propagation and annihilation of dislocations found in the solidlike film. These novel observations may provide new insights into the mechanical behaviors of lubricant films and thus improved lubricant design.