Theory Manual Version 3.4
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Subsection 7.6.2: Gap Function Up Section 7.6: Tied Biphasic Contact Subsection 7.6.4: Discretization

### 7.6.3 Penalty Method

Let the tied contact traction be described by the penalty function, where is a penalty factor associated with . Similarly, let where is a penalty factor associated with . It follows that Given these relations, it can be shown that the directional derivatives of the various terms appearing in the integrand of are where .
Subsection 7.6.2: Gap Function Up Section 7.6: Tied Biphasic Contact Subsection 7.6.4: Discretization