Heat flux per unit area due to frictional dissipation (ABAQUS)

Hi all

I have a 2D model containing 2 2-D blocks rubbing on each other, producing heat at the interface. (Coupled temperature-displacement analysis in ABAQUS 6.8-1). This works fine, as the temperature on the contact surfaces in increasing.

Now, I want to get the instantaneous the heat flux per unit area due to frictional dissipation as a field output. Is there any standard subroutine or any other way to achieve that? There is no such a variable included in the standard ones.

Thanks!
Andreas