Questions about quasi-static simulation with PotentialBlocks
Hi, everyone,
I have some questions about quasi-static simulation with PotentialBlocks, which have been bothering me for a long time, and I've tried a lot. My target: A true triaxial test was simulated by PBs (PotentialBlocks). These are some steps:
(1) Step1: The formation of a loose collection of particles in a regular hexahedron, without any contact between the PBs at first, is generated by replacing the pell,ets. (Fig. 1.)
(2) Step2: The six faces of a regular hexahedron are six PBs that, by giving them a certain speed, make them move towards the middle while compressing the particles inside together. (Fig. 2.)
(3) Step3: Stop the movement of the six faces, and let the internal PBs gradually reach equilibrium, that is, fill the entire interior of the hexahedron, and the unbalancedForce()
reaches below 0.01 (or some other small enough threshold). (Fig. 3. shows one of my tests)
My Questions:
(1) I think this should be a quasi-static simulation, I use whether the unbalance force can be reduced to 0.01 to judge whether it is stable. However, no matter how I try, the unbalancedForce()
always fluctuates and decreases first, and then cannot reach 0.01 or so for a long time. And, the velosity and force of the PBs can't be close to 0.
(2) I have tried to use calm()
for every 20 steps, 50 steps and many other step interval. I also have tried to modify the movement speed of the six faces of a regular hexahedron. Moreover whether to use the numertial damping (damping = 0.2) is also irrelevant. I have tried O.dt = 1e-4, 1e-5, 1e-6, the unbalancedForce()
is also difficult to decrease. Also, I used gravity = (0,0,0)
and gravity = (0,0,-9.81)
in NewtonIntergrator, which both do nothing to reduce the unbalance force
I really don't know what's wrong with it. How to reduce the unbalancedForce()
and how to make PBs stable quickly. Looking forward to your reply and thank you in advance. My code is too long to cut down to MWE, but I will provide it if necessary.
cheers,
Yunzhu