  We study the mechanical contact between a deformable body with a wavy surface
and a rigid flat taking into account pressurized fluid trapped in the
interface. A finite element model is formulated for a general problem of
trapped fluid for frictionless and frictional contact. Using this model we
investigate the evolution of the real contact area, maximal frictional traction
and global coefficient of friction under increasing external pressure. Elastic
and elasto-plastic material models, compressible and incompressible fluid
models and different geometrical characteristics of the wavy surface are used.
We show that in case of incompressible fluid, due to its pressurization, the
real contact area and the global coefficient of friction decrease monotonically
with the increasing external pressure. Ultimately the contact opens and the
fluid occupies the entire interface resulting in vanishing of static friction.
In case of compressible fluids with pressure-dependent bulk modulus, we
demonstrate a non-monotonous behaviour of the global coefficient of friction
due to a competition between non-linear evolution of the contact area and of
the fluid pressure. However, for realistic compressibility of solids and
fluids, contact-opening cannot be reached at realistic pressures. An asymptotic
analytical result for the trap-opening pressure is found and shown to be
independent of the surface slope if it is small. On the other hand, in case of
elastic-perfectly plastic materials, we again observe fluid permeation into the
contact interface. Finally, we study the distribution of frictional tractions
during the depletion of the contact area under increasing pressure. This
process leads to emergence of singularity-like peaks in the tangential
tractions (bounded by the Coulomb's limit) near the contact edges. We point out
the similarity between the processes of trap opening and interfacial crack...
