High Velocity Impact

[Alex109610]

I am trying to simulate an Impact with 860 m/s with an armour piercing bullet and a steel plate. After the impact, it seems like there is no contact between the bullet and the plate. I defined the Contact as General Contact with All* with self as contact domain. Furthermore the friction is 0.05 and the normal behavior is defined as "Hard" Contact.

 

[FEA way]

You should also include damage criterion for the material so that element deletion can take place. This way damaged elements will be deleted from the mesh. Is your velocity defined as initial condition ? If not it should be this way. What are the boundary conditions ? Can you share the input file ?

 

[Alex109610]

i defined damage criterion for the material. The initial velocity is defined as field input. I put the input file in the attachement.

 

[FEA way]

First I would make sure that material damage works properly and elements are actually deleted. You can use STATUS variable for this purpose. If general contact doesn't work, try with surface-to-surface contact definition. And if there are still problems start with rigid bullet and see what happens before making it deformable.

 

[StefCon]

I believe that a set of internal element faces need to be added to the general contact for it to keep making contact.

Included pairs of general contact:

All* with Self

AND

All* with ElementInternalSurfaces

 

[FEA way]

Yes, this is an issue thoroughly discussed here:

https://www.eng-tips.com/viewthread.cfm?qid=338020

However I think that the result Alex109610 gets and shows in the picture is not due to the fact that contact with internal elements wasn’t defined but rather due to some issue with element deletion.

 

[Alex109610]

Thank you all for your answers!

The main problem was the contact definition. It was only defined for the surface elements and not the internal elements. I solved that problem for a rigid projectile. Now I am trying to validate the material properties. I got them from an article and I think they work fine, but I don´t know how to get the data for the damage evolution. Nobody mentions a value for the fracture energy or the displacement at failure. I assumed a value and the element deletion works well. I am trying now to vary the fracture energy to meet the results from the article.
Do you got any idea how i get a good value for the fracture energy? My material is SECURE 500.

 

[FEA way]

Good that it works now. I’m afraid that it will be hard to find such material data in the literature. In your case it should be completly fine to assume some value and then calibrate it running the analysis several times until the resulting material damage will look as close to reality as possible.

 

[Alex109610]

I found good parameters for the material. My last problem are the constraints. I uploaded a picture of the simulation. The bullet is divided in three parts. The core, the jacket and an lead filler (grey). I got no damage data for the lead. But the main Problem is, that the lead and the jacket should slide on the surface. What is the best constraint or interaction property for this?

 

[FEA way]

Are these separate parts or partitions on the same part ? In the latter case you should model them as separate parts because otherwise there won’t be any relative movement between their surfaces. Modeling them as separate parts will let you define surface to surface contact interactions that, as opposed to tie constraint, will allow for sliding.