Hi everyone, I'm performing a model in LS-DYNA, and I need to set up an input motion only at the base of the model; thus, I selected PRESCRIBED_MOTION because it gives the possibility to add any of the following variables: displacement, velocity or acceleration. However, with this selection, the model does not recognize any friction with the environment (walls of glass in this case). I checked if the contacts are working properly, and I made another example, but this time with INITIAL_VELOCITY applied at the base, and this time the friction works properly.
Can anyone tell me how to put a prescribed input of acc, vel, or disp. at a segment of nodes.
Thanks in advance!
Hi @hugo-s,
This is one of the biggest drawbacks to using *Boundary_prescribed_motion, external factors do not affect the applied motion.
You can use *Initial_velocity to prescribe a velocity to a node set. If you have acceleration or displacement, then you can integrate or differentiate the curves to get velocity and then apply it.
@negativevolume, thank you for your answer, I was expecting that about external factors, however, the INITIAL_VELOCITY only allows a constant factor for velocity and I need to load an acceleration curve.
Ah I see your question now. I assume that you are using a motion curve from experimental data. Is that correct?
If so, then the curve that you are using would have taken any friction with the environment into account already so you could use *Boundary_prescribed_motion. But are you trying to measure the friction of the glass for the simulation? That may be why you don't want to use *boundary.