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bullet penetration - contact trouble (type 7)

Hello Sir,

I'm working on bullet penetration into steel plate.
At first contact works beetwen bullet and plate, but next it doens't work so good (picture 1).
Finally, contact again work (picture 2) and I don't know where is a problem.
On top of that, the speed of the projectile doesn't decrease (picture 3).

Contact settings:
Type 7
Istf: 4
Igap: 2
Fric: 0.2
Gapmin: 0.1
Inacti: 6

I tried a lot of contact setting, among others:
Type 7
Istf: 4
Igap: 2
Idel: 2
Fpenmax: 0,8
Stmin: 1000
Fric: 0,1
Gapmin: 0,04
Inacti: 6
Iform: 2

but still doesn't work.

Thanks for helping me.

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Altair Forum User

Hi,

Can you remove the failure parameters for the bullet material and try running?. And normally we make the bullet rigid for such a simulation, you can also try this approach.

Altair Forum User

Hi Johnson,
I removed failure parameters, but elements deformed too much and I had error - zero or negative volume. What do you mean about make the bullet rigid? Do you want to change MAT model from Johnson Cook to Rigid for projectile?

Altair Forum User

Hi,

Make the bullet component rigid. For that create a component collector with no card image, no mat/prop and go to 1D panel>>rigids and select all the nodes of the bullet as dependent nodes and for master node choose option as calculate node. For bullet component assign an elastic material.

Altair Forum User

Hi Johnson,
I added symmetry contact on solid surfaces and now contact works better, but still projectile velocity doesn't decrease.

Altair Forum User

Hi,

You can check the failure parameters assigned to the steel plate. It could like the steel plate is failing very quickly, ie the plastic failure strain value is less and it fails easily without causing much resistance to the bullet.

There should be a drop in kinetic energy of the bullet. Plot the KE graph for the bullet in HyperGraph and observe whether there is any drop in KE after impact.

Altair Forum User

Hi,

I appreciate your help, my problem solved when I changed material and failure properties, but i'm still looking for accurate material model and properties for bullet. I chaned also bullet from solid to SPH definition. Do you recommend any material models in Hypermesh/Radioss to build lead and copper bullet model (LAW 'number')??? Maybe Should I use any bilinear model?

Altair Forum User

Hi @mkalisz

Did you check LAW 4 which supports Hydrodynamics?

Altair Forum User

Yes, I used LAW 4, but I should think that Johnson Cook isn't perfect choice to build lead core in projectile, because available of constans in articles isn't reliable enought.

Altair Forum User

@mkalisz

I think it will be easy if you can share what data you have for bullet material, Based on that I can check with experts for suitable material LAW

Altair Forum User

Recently, I tried this combination:

- Lead core: M1 Elastic
Rho: 1.127e-8
E: 17e3
v: 0.4

- copper jacket: M2 Plas Johns Zeril
Rho: 8.96e-9
E: 115e3
v: 0.31
a: 90
b: 292
n: 0.31
c: 0.025
epso: 1
m: 1
tmelt: 1250
thocp: 380
ti:293

It was look like better and I received decrease velocity of bullet, but I'm not sure if the results are correct because to build lead I used simple linear material model.

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Altair Forum User

Hi,

If I guess right lead behaves as a plastic material which is easily deformable. In such a case I don't think using Law 1 is good. You may to try with Law 2 or 36.