$\newcommand{\Dev}{\operatorname{Dev}}$ $\newcommand{\dev}{\operatorname{dev}}$ $\newcommand{\grad}{\operatorname{grad}}$ $\newcommand{\divg}{\operatorname{div}}$ $\newcommand{\Ei}{\operatorname{Ei}}$ $\newcommand{\tr}{\operatorname{tr}}$

The face_data class defines a set of surface variables. This item requires the surface attribute, which defines the surface that will be used to extract the data from. The surface must be defined in the Mesh section. The data is stored for each surface facet that is listed in the item list, or for all facets of the surface if no list is defined.

<logfile>
  <face_data data="contact gap;contact pressure" surface="FacetOnFacetSliding1_primary"/>
</logfile>