Learning Forum

[Nicolas Fontaine]

Hello,

I am pretty new with Ls-Dyna. I have a simulation working in two steps: a tube is plastically compressed, then it is compressed again but in another direction. The displacements of the compressing objects are defined with the function "Curve".

I would like first to simulate only the first compression, verify if it works, then simulate with the 2nd compression. Like this, I can avoid simulating the whole thing just to find out that there is a problem in the very first steps. It is a multiple hours simulation...

Is there an easy way to do that? A step-by-step simulation?

 

Thank you very much for reading me!

Nicolas

 

[Prasad Reddi]

Hi Nicolas,

You can try like this using Static or Transient Dynamic state considering that the load application is Displacement approach:

1. Using *BOUNDARY_PRESCRIBED_MOTION_SET if Displacement apporach (input load as Displacement vs Time). In this approach, you can extract the REACTION FORCES for either a set of nodes or if using an Impactor, you can extract the contact force to see the output FORCE needed for that APPLIED DISPLACEMENT
2. Using *LOAD_NODE_SET if Force approach (input load as Force vs Time)

In both cases, you can assign a load curve which you are defining using *DEFINE_CURVE.

Once the model is stable and working as you require, you can further model another load step using both the options.

Please let me know once you tried these options. Hope this will help you.

~Prasad

[Armin_A]

Hi Nicolas,

You can also check the forum thread below where this topic is discussed:

https://forum.ansys.com/forums/topic/error-using-dynain-file-for-sequential-simulations-with-beams-runaway-velocity/ 

[Nicolas Fontaine]

Thank you, both! I will try it and come back to you :) 

[Nicolas Fontaine]

Hi,

Sorry for my late answer. 

@Armin_A I checked your link but it didn't really help me with my problem. But thank you!

@Prasad How do I extract the reactions forces and what do I do with them then (sorry, I am still a beginner with Ls-Dyna)? Which functions should I use to do this? I am using Displacement vs time approach and *Boundary_Prescibed_motion_rigid by the way.

Thank you for your time.

~Nicolas