Hi all,
I am new to LS-Dyna and I'm simulating the impact between a shell plate and a rigid body ellipsoid projectile.
I don't know how I can obtain the RCFORC between the plate and the projectile and also the residual velocity of the projectile. I didn't find any option in the d3plot file to plot the residual velocity of the projectile and also the Resultant force after the impact (I activated RCFORC in ASCII before running the model but it shows zero force throughout the simulation)
you can use mat 024 or 03 for projectile with the following set up:
contact-automatic-single surface
SSID=shell plate, MSID=0
SSTYP=3 and MSTYP=0
@mahmoud, I tried your suggested contact_Automatic_Single_Surface, but it doesn't result in any contact between the plate and the projectile. Would you let me know why the reason for considering MSID=0 and MSTYP=0 is? Shouldn't we define a master?
For the projectile, do you mean that I cannot define it as a rigid body and have RCFORC other than zero?
Thank you,
@sheida In case of structural damage due to such impact, self-contact may occur, so set the self-contact condition on the target structure or on the projectile. For applying self-contact we can use the Contact_Automatic_single_surface keyword. If all master surfaces are set to 0, self contact occurs only on the slave surfaces(for your case slave surface is shell plate).
for the projectile you can use rigid material but I think RCFORC option can not capture the force.
@mahmoud Thank you for the explanation. I tried this contact but after running the model, the projectile passes through the plate without any impact.
So it seems that I should consider the projectile as a solid or non-rigid shell.
thanks,
@sheida I want to answer to your second question.
To see residual velocity it is very easy.
Follow this pic's steps:
Thank you @mass.
Is it the exit velocity of the projectile from the plate, right? I mean, I should find the moment of exiting the projectile first and interpret its velocity, correct?
Thanks,
first of all check the normal direction of shell parts and if inelastic response of shell part is expected set NIP to a minimum of 3 on section_shell keyword.
As my last suggestion :
You can use RCFORC data written for contact transducers (*CONTACT_FORCE_TRANSDUCER_PENALTY) to extract any contact forces. A contact transducer is defined like a single surface contact, i. e. you define the slave side only and supply 3 cards of input (cards 2 and 3 can be blank). If you wish, you can define a separate force transducer for each part. You can even break it down further and define a transducer for a set of segments or even a single segment.
Transducers are NOT implemented for 2D contact and should not be defined in a 2D model.
Good Luck
@mahmoud Thank you very much. I tried *CONTACT_FORCE_TRANSDUCER_PENALTY and it worked. I tried it besides two types of contact: 1)Automatic_Surface_to_Surface and 2)Nodes_to_Surface.
when I implemented it with the first one, it gives me the maximum Resultant forces in the first moments of the simulation after the impact, while with the second one, it happens at the end of the simulation.
As you suggested, I applied *CONTACT_FORCE_TRANSDUCER_PENALTY only for the plate as the slave part. Before running the model, I changed the projectile's material to a deformable material. However, I tried rigid body next and it gave me the nonzero RCFORC as well.
I will work on that to see which type of contact I should use with this *CONTACT_FORCE_TRANSDUCER_PENALTY to make an accurate impact model.
Thank you again,
@sheida
There is a projectile example available on the internet (dynaexamples.com perhaps?). I don't remember but I bet there are YouTube videos of such an example. Once you get the kinematics right, then you focus on getting the contact forces out.
@icebreakersours There is an example of "Projectile penetrates a plate" in LS-DYNA samples, but it also shows the contact force equal to zero throughout the simulation.
I saw a few videos on Youtube which all of them modeled Ballistic impact with *Contact_Eroding_Surface_to_Surface. I want to use their contact idea to see if it works as well. In this situation, I should define *MAT_ADD_EROSION beforehand. The problem is that there are some parameters that I need to define in this type of contact and MAT_ADD_EROSION that I don't know how to define.
Thank you,