Theory Manual Version 3.4
$\newcommand{\lyxlock}{}$
Section 7.2: Biphasic Contact Up Section 7.2: Biphasic Contact Subsection 7.2.2: Gap Function

### 7.2.1 Contact Integral

See Section 2.5↑ for a review of biphasic materials, and [11] for additional details on biphasic contact. The contact interface is defined between surfaces and . Due to continuity requirements on the traction and fluxes, the external virtual work resulting from contact tractions and solvent fluxes (, may be combined into the contact integral In the current implementation, only frictionless contact is taken into consideration, so that the contact traction has only a normal component, . To evaluate and linearize , define the covariant basis vectors on each surface as where represents the spatial position of points on , and represent the parametric coordinates of that point. The unit outward normal on each surface is then given by Now the contact integral may be rewritten as and the linearization of has the form
Section 7.2: Biphasic Contact Up Section 7.2: Biphasic Contact Subsection 7.2.2: Gap Function