Hello, 

I need to restart an external load step from previous bolt pretension step. I want to increase friction for one contact pair, but all contact pairs have used the same interaction property. I try to use '*model change, activate, type=contact pair, ...' to activate one contact pair and then using '*change friction ...' to change its friction. See below: 

*STEP, INC=100

*STATIC

0.2, 1.,0.01,0.5

**************************************

*MODEL CHANGE, ACTIVATE, TYPE=CONTACT PAIR

xxx, xxx

*CHANGE FRICTION, INTERACTION=xxx

*FRICTION

0.3

*************************************************************************

But it seems that model change doesn't work when I checked .dat file, see below.  

*STEP, INC=100
*STATIC

***WARNING: TOO MANY DATA LINES HAVE BEEN SPECIFIED FOR *STATIC
*CHANGE FRICTION, INTERACTION=xxx
*FRICTION
*CONTROLS, ANALYSIS=DISCONTINUOUS
*CONTROLS, PARAMETERS=FIELD
*CONTACT CONTROLS, STABILIZE  

So, anyone has idea how to do this? Thanks :)

Abaqus ​​​​​​​