A
study was conducted
of
the
factors that cause anoma
lous
EHD
film shapes in 1
-
dodecanol lubricated contacts
–
i.e.
a thickened central plateau and an exaggerat
ed
outlet constriction. This
has
led
to the hypothesis
that,
in the region where
pressure
s
exceed
~0.44 GPa, dodecanol
experiences slip
, which reduce
s the average lubricant
velocity
and causes
an elevated film thickness in ord
er to maintain flow continuity.
The analysis suggests that slip must
be
occur
r
ing
at, or close
to, the faster moving
surface, since
a
discontinuit
y
in the
flow
midway through the
thickness
of the film
would
not
affect
the average
speed
of the lubricant
.
Based on this hypothesis, an
equation
has been
derived to predict the anomalous central film thickness as a function
of applied slide
-
roll ratio and this
has been
validated by com
parison with
experimentally measured central film thickness values.
Further support of this
hypothesis is provided by traction test results showing a discontinuity occurring
close
to
the onset of slip.