Hi @marso1,
Moving this to the LS-Dyna help forum since your question is about the simulation itself.
I'll need more information to help with this. How are you keeping the dampers closed? You will need to model some sort of mechanism to represent a clamp at the end if you don't currently have anything.
Hi,@negativevolume.
Thanks for your help.
The damper down is fixed and the damper up has to sqeeze the bar.
On the damper up a force is applied.
At first the damper up squeeze the bar but after few millisecond it moves away, it doesn't keep the position.
I do not need to model anything.
My problem is just the damper up that doesn't remain stick to the bar
Regards
@marso1 Is the curve you are using to define the force terminating just after the simulation starts? Alternatively, if the force you are applying is too high and the clamps are just pushing the limits of your contact then the force could just keep going up until it learns to social distance properly.
(Or maybe the damper shell is substantially thiccer than you mean for it to be.)
As a personal question, how do you know how much force you need to use for the clamp, was it something you have already measured? I always have trouble with that.
Hi@samuelbas
The curve that I am using to define the force last for une second, but the test last 0.005 seconds.
I have to find the force that stops the wave.
To be honest I tried with a force of 200N.
I will try with a force that is less than the last one.
I am going to try very soon
I will let you know
Many Thanks for your interest on my problem
Regards
@marso1 you need to use a constant force curve over the duration of the simulation. For example:
Time Force
0 sec 200N
1 sec 200N
Are you using *Load_Node or *Load_body? And can you look at the contact force output between the top clamp and bar? I can help with any of this if you need it
@negativevolume, I did It,
At first the force curve is a ramp and than is constant.
- The force is "Load Node"
- The contact between the bar and the clamp is "Automatic surface to surface _ Mortar"
Yes I need an help
I can send you the model if you like
Regards
@marso1 have you checked the shell thickness of the damper like @samuelbas mentioned? Or do you have any defined thickness in the contact? (MST, SST)
Yes I have. Under the properties i put the shell thiknes (T1=2mm)
Under the groups I put both (MST and SST) = 0
Regards
@marso1 and what is the distance between the end of your dampers? Just checking that it is more than 4 mm.
The distance between the damper down and the bar is zero. (It must be so)
The distance between the damper up and the bar is 1 mm
@marso1 are damper up and damper down in contact with each other? And what is that distance? Also do you have *Control_contact? Make sure the Ignore option is set to 1 or 2. You should also read the section on penetration guidelines in this:
https://www.dynasupport.com/tutorial/ls-dyna-users-guide/contact-modeling-in-ls-dyna
I have a feeling your large penetrations may be causing your issue with you dampers not compressing.
@marso1 Also, try outputting (*Database_rcforc) and plotting the contact force between your dampers and the bar and damper to damper. This will help debug what is going on.
Hi!
I finally solved the problem was in a curve, I forgot to put "SIDR" equal to zero.
Many thanks
Regards
Marso1