The traction excerted by the master face on the slave face at a slave integration point p can be written analogous to Equation (116):
| (190) | 
For simplicity, in the face-to-face contact formulation it is assumed that
within an increment the location 
![]() of the projection
of the slave integration points on the master face and the local Jacobian on the
master face do not change. Consequently (cf. the section 6.7.4):
 of the projection
of the slave integration points on the master face and the local Jacobian on the
master face do not change. Consequently (cf. the section 6.7.4):
|  | (191) | 
and
|  | (192) | 
which leads to
|  | (193) | 
This is the normal contact contribution to Equation (189).