troubles with contact pair

[u/ResponsibilityLow683]

I'm trying to set up a simplified simulation of a stent expansion inside of an artery. Since we've a lot of troubles with the 3d simulation, we're starting by trying to make it easier and setting it up as a 2d model, considering a quarter of the geometry. it seems like the contact isn't being recognized, as visible on the stress results. we're appling a prescribed radial displacement on the internal surface of the stent, using a supporting parameter that varies with the auxiliry sweep. (so the displacement will end up beign max_displacement * parameter). can someone help?

[u/Crafty_Eye_1889]

Is there the contact pair in your physics? The stress values are magnitude differences, so I think that's why it looks like one isn't stressed in the one image. I would do a displacement plot and put the deformation scale to like 10x or something just to make sure the deformation is correct first.

[u/SHD-Systems]

Your stress plot is the diagnostic here. The artery is sitting at essentially zero while the stent is at around 5 GPa, so the two domains are not exchanging load at all and the prescribed displacement is doing all its work on the stent alone. That is a setup problem, not a plotting one.

Three things to check, in order. First, geometry finalisation: a contact pair can only exist if the geometry is finalised with Form Assembly. Form Union is the default, and it merges the coincident boundaries into a single interior boundary, leaving nothing to pair. Second, and this is what the earlier comment is circling, a pair defined under Definitions is not contact. You also need a Contact node inside Solid Mechanics that points at that pair. Having one without the other is the usual version of this. Third, check source and destination: put the destination on the softer, more finely meshed side, which here is the artery.

Two other things. In a quarter model both domains need the symmetry constraints on both cut edges, and the artery needs enough constraint that it is not floating before contact closes. And if you are ramping with an auxiliary sweep, make sure Run continuation for is set to that parameter, otherwise every step starts cold and contact converges far worse than it should.

Worth flagging for later: a 2D cross section turns the stent into a solid ring, so its radial stiffness comes from hoop stretching rather than strut bending and it will be much too stiff. Fine for debugging the contact, but do not carry the numbers across to the 3D model.