Hi, All:
I am trying to apply a constant force on a moving mesh wall (circular), which command is the best implementation in LIGGGHTS? The problem I am trying to simulate is a piston pushing from the bottom of a cylindrical sandstone, I attempted to use a servo-controlled wall by using mesh/surface/stress/servo however it seems the servo-wall will need a certain amount of time to reach the target value, is there a way that the force can be applied as a constant value throughout the entire simulation? e.g. F=200N from t=0 to the end, I searched for commands like fix setforce or fix aveforce, however are those commands supposed to work on the moving mesh wall?
Thanks for any suggestions and forgive me if there is some basic conceptual error understanding of the servo wall.
Regards,
Roy
aaigner | Wed, 10/07/2015 - 13:38
Only servo-wall ...
Hi Roy,
To apply a force via a wall (stl-mesh) you can only use the servo-wall. The other way to move a wall is the fix move/mesh command, which only works with a prescribed trajectory (regardless of the required force).
Another point is the velocity of the servo wall:
If you are not familiar with PID- controller, I suggest to use the mode auto setting and a ratio in the range of 0.01 and 0.001 (higher is faster, but the force may oscillate more until instability). The auto-mode is a simple non-linear P-controller, thus you don't have to bother with the integrative and derivative gain-factor.
Bests
Andreas
dbxmcf | Thu, 10/08/2015 - 16:35
Hi, Andres:
Hi, Andres:
Thank you very much for the guidance, I will tweak those parameters and see the results!
Roy