Learning Forum

[RD2016]

Hey guys,

I'm running into issues with using the contacts in Transient Structural. I've used them in the past, and they've always modeled nice behavior. For whatever reason now, however this is no longer the case.

I'm trying to simulate a knee replacement assembly, shown below.

I want the knee to have some sort of kinematics,so I've set up a remote displacement on my femoral component, and have everything fixed except the translation in the z-direction (free), and rotation in the x-direction (input gait data). I've also placed a remote displacement on the bottom part, and fix it in all but one-direction (it can move up and down). I've put a force on the bottom of this, and have it set to push up (to simulate the force of someone walking).

I've instituted a frictional contact between the articulating surfaces.

Everything tends to run fine, I get articulation like I'm expecting, and then, all of a sudden, the contact points seem to disappear.

Physically, it's acting as if the assembly sees itself within one time step, and then it doesn't the next.

Obviously, I attempted many settings (tried all of the detection methods, adjusted the stiffness, played around the the interface treatment, etc.). Further, I double-checked to ensure that all of the articulating faces on each part were selected properly. I'm losing my mind here, this should be a simple problem. Does anyone have any recommendations?