Hi All,
I was wondering if there is a way to activate a part at some point after the simulation has started. I am simulating a debris impact generated from a wave and ideally I would like to not include the debris in the calculations until after a few seconds as the wave has to propagate a large distance before reaching the debris. Does anyone have any idea how to do this or if this is possible?
Thanks!
This is a great question. I don't know of any way to do this specifically. I do know that some things in LS-Dyna have birth times, meaning they are applicable until that time in the simulation. I'll be on the lookout for any features that may help you.
Are you just wanting to do this for time-savings?
Yes I am trying to do this for time-savings, essentially I am running a 6-10s simulation with the explicit solver so its takes quite a bit of time and I don't believe my current version (v10) of LS-DYNA supports SPH implicit solvers.
I have found that the *SECTION_SPH card has a start and death time and then I just hold the particles in place using *BOUNDARY_SPC_SET however this only solves my problem if I model everything with SPH which is not ideal for the structure I want to model. I have yet to find a similar *SECTION card for solid elements.
Cheers!
Is the solid debris going to be analyzed in any way or are you just studying the wave response? Because you could just model the debris as rigid 2D shells which would have little to no impact on your computation time.
Currently I don't care about the response of the debris but we are trying to investigate the impact force it generates on a structure. Can't say I am familiar with 2D shell elements, do you know of any examples I can base this off of? I have found that modeling a rigid object that moves, impacted run times significantly with solid elements in the past.
Cheers!
The 3D elements should be fine as well to model as rigid since you already have them. Runtime is determined by the timestep of your simulation, and since rigid parts are undeformable, they have no impact on the timestep. I would try to make them *MAT_RIGID and see how it goes. You will still be able to retrieve the force of the waves to the rigid parts through RCFORC in your Database_ascii option.
If you want the force from individual pieces of debris, then you can make *Contact_force_transducers for the wave to each piece of debris using different segment sets.