Theory Manual Version 3.4
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Subsection 7.1.2: Weak Form of Two Body Contact Up Section 7.1: Sliding Interfaces Subsection 7.1.4: Discretization of the Contact Integral

### 7.1.3 Linearization of the Contact Integral

In a Newton-Raphson implementation the contact integral must be linearized with respect to the current configuration: Examining the normal contact term first, the directional derivative of is given (for the case of the penalty regularization) by: where is the penalty factor and is the Heaviside function. The quantity is given by
Subsection 7.1.2: Weak Form of Two Body Contact Up Section 7.1: Sliding Interfaces Subsection 7.1.4: Discretization of the Contact Integral