radial force stent crimping
radial force stent crimping
(OP)
thread799-356649: Stent Crimp & Expansion: Deformable vs. Rigid Parts vs. RSURFU
Hi to all,
I'm trying to reconstruct a numerical model of two Nitinol stents and I need information about the radial force they exibit.
I have meshed the stent frame models with C3D8R elements and I have considered the UMAT subroutine based on Auricchio and Taylor to reproduce the material properties. In addition, I have built a cylinder (SFM3D4R elements, rigid) around each stent. The diameter of the cylinder is reduced and then re-explanded. I have performed analyses with Abaqus\Explicit 6.13 and they run. Now I have a problem: I want to evaluate the radial force of the each entire stent but I don't know how it is possible to do this. Which is the best way to evaluate it? In several articles I have found force-diameter curves related to the entire model. At now I am only able to evaluate the force in a single point. Which parameters are necessary to trace during the whole simulation to reach my pourpose?
Best regards
Hi to all,
I'm trying to reconstruct a numerical model of two Nitinol stents and I need information about the radial force they exibit.
I have meshed the stent frame models with C3D8R elements and I have considered the UMAT subroutine based on Auricchio and Taylor to reproduce the material properties. In addition, I have built a cylinder (SFM3D4R elements, rigid) around each stent. The diameter of the cylinder is reduced and then re-explanded. I have performed analyses with Abaqus\Explicit 6.13 and they run. Now I have a problem: I want to evaluate the radial force of the each entire stent but I don't know how it is possible to do this. Which is the best way to evaluate it? In several articles I have found force-diameter curves related to the entire model. At now I am only able to evaluate the force in a single point. Which parameters are necessary to trace during the whole simulation to reach my pourpose?
Best regards





RE: radial force stent crimping
You need to sum the radial reaction force at each node on your rigid surface at each increment to obtain the force response over time. You can figure out the diameter values from the starting diameter of the rigid surface and the applied displacements. Alternatively, you can simplify this task significantly by using a reference point and *Equation to control the rigid surfaces. That way, you can just plot the radial reaction force for the reference point during the analysis (no summation required).
This type of analysis would also be a lot quicker to run in Abaqus/Standard.
Good Luck,
Dave
RE: radial force stent crimping
(I have selected
penalty technique: 'Normal behavior constraint enforcement method' = default; pressure-over closure: 'Hard contact';friction formulation='Penalty'; friction coefficient=0)
Thanks,
AliceF
RE: radial force stent crimping
RE: radial force stent crimping
FYI: I am not sure if having a friction coefficient of zero is very accurate. Since it is likely a small number (0.01, perhaps?), you will be better off keeping it zero until you get the rest of the model set-up correctly.
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RE: radial force stent crimping
my question is pretty similar. I'm using Abaqus/Explicit. The crimping tool in my case is octogonal in cross section. I used 3d deformable part and meshed it using SFM3D4R elements. One node on the stent is fixing it in the Z axial direction (cyl coord) and tool is crimped by inward radial displacement. Simulation seems to work fine and now I need to compute the radial force. How am I to do that? I looked at Reaction Force for the nodes on the tool, but they are far too small to what I'd expect. Any advice would be really appreciate it.
RE: radial force stent crimping
You need to follow the exact same instructions i gave AliceF. Sum the radial reaction force at each node on your SFM3D4R surface(s) at each increment to obtain the force response over time. Simplify this task significantly by using a reference point and *Equation.
Dave
RE: radial force stent crimping
RE: radial force stent crimping
Maybe throw up some images of your model or share your input deck if you still have problems.
RE: radial force stent crimping
RE: radial force stent crimping
RE: radial force stent crimping
RE: radial force stent crimping
RE: radial force stent crimping
RE: radial force stent crimping
RE: radial force stent crimping
RE: radial force stent crimping
For the other half, it's the same signature, but magnitude ~8N. The stent is not quite positioned centrally, so I suspect that's why the values are not identical.
RE: radial force stent crimping
Definitely an issue with your explicit analysis by the looks of it.
RE: radial force stent crimping
RE: radial force stent crimping
In Viewer you can go to "Tools -> Coordinate System -> Create" to create a polar coordinate system. Then go to "Result -> Options -> Transformation -> User-Specified" and select the new polar coordinate system to transform your data. Now you just extract the RF component corresponding to the radial direction.
RE: radial force stent crimping
RE: radial force stent crimping
In global Cartesian coordinates RF1 = RFX. In polar coordinates RF1 = sqrt(RFX^2+RFY^2) so should be different.
RE: radial force stent crimping