May 7, 2023 at 8:11 pmminchunhSubscriber
I'm modeling a tension specimen under displacement control by applying prescribed displacement to the node set, while from the output data, the motion of the node set is not moving as I prescribed. I'm using solid element -1. I wonder if anyone faced this kind of problem before?
May 8, 2023 at 1:15 pmArmin_ASubscriber
Could you please provide more information regarding your model?
For example, what LS-DYNA card do you use to apply the motion? Do you use *BOUNDARY_PRESCRIBED_MOTION_SET?
Do you apply displacement to the specimen's end along the right direction? Do you constrain the other end of the specimen to resemble a fixed clamped condition?
May 8, 2023 at 5:10 pmminchunhSubscriber
Yes, I'm using *BOUNDARY_PRESCRIBED_MOTION_SET as well as applying fixed-clamped conditions to the other end. Also, at the end of applying the prescribed motion, Boundary_spc is also applied to constrain the DOFs other than the direction under displacement control. I tried applying other magnitudes of the cyclic displacements, but the problem only occurs when certain prescribed displacement curves are used (i.e., this issue does not always occur, which is weird).
May 8, 2023 at 5:57 pmArmin_ASubscriber
I see. As you indicated, it's odd that the issue does not always occur. I would suggest that you remove the BOUNDARY_SPC card for now to focus on ensuring the *BOUNDARY_PRESCRIBED_MOTION_SET is working properly. Once it's fixed, you can add more cards.
I don't think element type play any important role here as the problem seems to be more relevant to the prescribed boundary conditions.
May 8, 2023 at 6:04 pmminchunhSubscriber
I only applied *BOUNDARY_PRESCRIBED_MOTION_SET at first but the issue showed up so I added BOUNDARY_SPC. Thanks anyway, I will keep looking into it.
May 8, 2023 at 6:16 pmArmin_ASubscriber
No problem Min-Chun.
While you investigate the model, it is worth checking that the generated set includes all the nodes at the one end of the specimen. Also, try applying a velocity (instead of displacement) boundary condition by changing VAD from 2 to zero in the *BOUNDARY_PRESCRIBED_MOTION_SET card and providing a velocity curve to the model. I usually get better luck with velocity BCs for tensile test simulations.
May 8, 2023 at 6:43 pmAndreas KoutrasAnsys Employee
Some examples that may help with the modeling of coupon tests are available here:
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