Dear all,
I am coding a triaxial compression test using LIGGGHTS and want to apply the command: Fix mesh/surface/stress/servo. I set my servo wall as follows:
fix F_movetop all mesh/surface/stress/servo file topwall.stl type 2 wear finnie com 0. 0. 0.1 ctrlPV force axis 0. 0. -1. target_val 2000 vel_max 0.001 kp 1e-2. ki 0. kd 0.
fix F_movebottom all mesh/surface/stress/servo file bottomwall.stl type 2 wear finnie com 0. 0. 0. ctrlPV force axis 0. 0. 1. target_val 2000 vel_max 0.001 kp 1e-2. ki 0. kd 0.
fix F_moveleft all mesh/surface/stress/servo file leftwall.stl type 2 wear finnie com 0. -0.05 0.05 ctrlPV force axis 0. 1. 0. target_val 2000 vel_max 0.001 kp 1e-2. ki 0. kd 0.
fix F_moveright all mesh/surface/stress/servo file rightwall.stl type 2 wear finnie com 0. 0.05 0.05 ctrlPV force axis 0. -1. 0. target_val 2000 vel_max 0.001 kp 1e-2. ki 0. kd 0.
fix F_movefront all mesh/surface/stress/servo file frontwall.stl type 2 wear finnie com 0.05 0. 0.05 ctrlPV force axis -1. 0. 0. target_val 2000 vel_max 0.001 kp 1e-2. ki 0. kd 0.
fix F_moveback all mesh/surface/stress/servo file backwall.stl type 2 wear finnie com -0.05 0. 0.05 ctrlPV force axis 1. 0. 0. target_val 2000 vel_max 0.001 kp 1e-2. ki 0. kd 0.
The target force value is 2000N, while the results in Paraview show that the forces acting on the servo wall (All of these 6 servo wall) are very small and far away from the target value. Is there anything wrong with my parameters? How to make the real force on servo wall to be equal to the target value?
My timestep is 0.00001 and the solo particle size is 0.0025. Could anyone please help me? Many thanks!
Best regards,
Zheng
Zheng Hu | Thu, 10/12/2017 - 19:08
Thanks for your help
Dear Matej,
That's great, your suggestion really works fine and thank you very much. Also I may have another question. When I use the command "fix mesh/surface/stress" and "fix move mesh", I want to output (print) the location of the wall, the f_filename[7-9] seems not to be the location of the walls, which is different from "fix mesh/surface/stress/servo", do you know how to print the location of these walls?
Many thanks,
Zheng