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Mass Damping

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Posts: 6
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(@kein_roboter)
Student
Joined: 1 year ago

Hello Everyone,

I want to perform a slow speed crush simulation using explicit solver in Ls dyna, the impactor crushed the target which is held constrained by a rigid wall. As per my understanding, since the impactor has a huge displacement, I shouldn't be including this in the *DAMPING PART MASS. But as I want the impactor to come into contact with the target at t=24 ms, so at that instant should I cncrease the load curve value to 1.0  and then decrease it again? or should I increase the value at the start of the simulation (as shown in the picture, where red point indicates the moment when the impactor comes into contact)?

 

VG

 mass damping
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Negative Volume
Posts: 639
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(@negativevolume)
CEO
Joined: 5 years ago

Hi @kein_roboter

Here's a good overview of damping:

https://www.dynasupport.com/howtos/general/damping

My suggestion is to first run your simulation without damping, so you can have a baseline to cross-check your results with damping. Damping is optional but if you decide to add it to your simulation, you might need to do some adjusting. Your target should be 10% critical damping.

Are you using boundary prescribed motion for your rigid walls? And what is the total displacement? If you simulation is a slow controlled crush of a vehicle, then these rigid parts will be undergoing rigid body motion the entire simulation, so your curve idea won't work. It would work if it were something like *Initial_velocity. I think the most simple implementation would be to use *Damping_global and just see what you get. Then you can try *Damping_part_mass_set and add all parts except your rigid walls. 

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1 Reply
(@kein_roboter)
Joined: 1 year ago

Student
Posts: 6

@negativevolume Thank you for the insight. I'll definately keep updating my findings here.

 

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