.. _contact-log:

****************************
Log File Contact Information
****************************

When contact is included in the analysis, pertinent information is written to the log file. Information on the name and size of each contact surface will be included in a table as shown::

   -------- DASH SURFACES --------
    Contact Entity   Num Faces   Num Lofted   Num Points   MinCharLen   MaxCharLen
   ---------------- ----------- ------------ ------------ ------------ ------------
          pin_surf           0            0          287          0.0        0.012
           block_1         994            0            0         0.01         0.01
           block_2           0           24            0         0.02         0.03
      surface_1000           4            0            0         0.50         0.50

The above table will have one entry for each defined contact surface. The name of the contact surface is in the "Contact Entity" column. "Num Faces" is the number of non-lofted faces (such as triangles or quadrilaterals) contained in the surface. "Num Lofted" is the number of lofted objects (such as shells, beams, or particle elements) contained in the surface. "Num Points" is the number of nodes in the contact surface that are not part of any of the faces or lofted elements. ``MinCharLen`` and ``MaxCharLen`` are the minimum and maximum characteristic length of any face or lofted object in the contact surface.

The log file will also include a representation of the interaction matrix, for example, of the form::

   ------------- DASH INTERACTION WEIGHT MATRIX ------------
   0000
   1H00
   00HH
   00H0

The topmost row and leftmost column of the interaction matrix correspond to the first entry in the "Contact Entity" list. The bottom most row and the rightmost column of the interaction matrix corresponds to the last entry in the "Contact Entity" list. The entry at row I, column J of the matrix describes how contact surfaces I and J interact. 

A value of "1" indicates that contact surface I has interactions with contact surface J where surface I is the side B surface and surface J is the side A surface. For node-face contact this means that the nodes of surface I contact the faces of surface J. For face-face contact this means that the faces of surface I interact with the faces of surface J and that the gap integral is performed on faces of surface I. 

A value of "H" (short for half) indicates contact surface I interacts with contact surface J in symmetric contact. For node-face contact this means that the nodes of surface I contact the faces of surface J and also the nodes of surface J contact the faces of surface I. For face-face contact this means the faces of surface I contact the faces of surface J and the gap integral is performed simultaneously on both sides of the interface.

A value of "0" in both the IJ and JI position of the matrix indicates that surfaces I and J will not interact via contact.

Note that a surface can only interact with itself (the diagonal entries of the matrix) through self contact. If entry IJ of the matrix is "1" entry JI must be "0." If entry IJ of the matrix is "H" than entry JI must also be "H."
