FINAL VELOCITY OF A BULLET 1

[Oluwakay]

Hello Everyone,
I have a question. I ran an impact simulation of a bullet into a target. From the experiment, there was not any penetration and the bullet was stopped and stuck in the target. However, when I ran the simulation, the velocity time plot of the bullet does not reach zero. Does that mean the calculation is wrong? Must every bullet that stops have a final velocity of zero? what about the residual velocity? I think if the dissipated energy is not sufficient to make the bullet get back to zero then the final velocity might not get to zero.

Kindly share your thoughts please!
Thank you!

 

[FEA way]

Did you use initial velocity ? How do you measure the velocity ? Is the bullet rigid ? Some screenshots would be helpful.

 

[Oluwakay]

Yes, I used initial velocity of 350 m/s and it is deformable. I picked different nodes of the bullet and extract their velocities. I noticed if i increased the time, the bullet will eventually have a final velocity of zero. But is this correct in a real sense? since the time should correspond to the distance between the bullet and the target plus the thickness of the target. We can estimate the appropriate time if we relate those with the initial velocity. Am i correct?

 

[FEA way]

Such explicit dynamics impact analyses show very high speed events and with a short time frame you may notice that the part not yet fully decelerated/stopped. Check if this longer analysis where it actually stops makes sense. Apart from looking at the velocities, you should check other outputs as well. Especially energies but also make sure there’s no large noise which is a common problem in the case of Abaqus/Explicit.

 

[Oluwakay]

Thank you so much for your response. I tried to increase the time it required for the calculation and compared the results with the experimental results and both looks similar. Also, Played around the mesh size by refining it a bit. In all, the outcome looks really cool.
Thank you so much!