  Shearing transitions of multi-layer molecularly thin-film lubrication systems
in variations of the film-substrate coupling strength and the load are studied
by using a multiscale method. Three kinds of the interlayer slips found in
decreasing the coupling strength are in qualitative agreement with experimental
results. Although tribological behaviors are almost insensitive to the smaller
coupling strength, they and the effective film thickness are enlarged more and
more as the larger one increases. When the load increases, the tribological
behaviors are similar to those in increasing coupling strength, but the
effective film thickness is opposite.
