AutoDyn Bullet Impact Analysis Help
AutoDyn Bullet Impact Analysis Help
(OP)
I am trying to analysis a bullet vs armor situation in AutoDyn and it comes out mostly correct although the bullet doesn't seem to be realistically simulated and I am concerned about it. Attached is the .MP4 file of the animation generated from the results. Notice how the entire bullet breaks down into particles, rather than holding together? The armor does fine and fragments at the end, which is realistic, but I am afraid the bullet itself isn't actually showing me what will happen in real life. All of my hand equations say it can penetrate this armor thickness, so I doubt I'll ever get a result showing it cannot.
The material for the armor is AR500 steel, the bullet has a copper jacket and a Molybdenum core. I had to use the same damage Johnson cook failure criteria (D1-D5) as tungsten carbide for it since there doesn't appear to be any damage models out there for Molybdenum and they are similar materials, in the same column of the periodic table.
Is this normal behavior? What exactly do all the red particles from the projectile mean? Is there a way I can get a more accurate simulation where the core doesn't just break into a node sized element? I was expecting something along the lines of this simulation: https://www.youtube.com/watch?v=XYuKWuyKXII. Granted, theirs are are against an angled armor, but everything correctly fragments in that simulation.
Any help on this is greatly appreciated!
The material for the armor is AR500 steel, the bullet has a copper jacket and a Molybdenum core. I had to use the same damage Johnson cook failure criteria (D1-D5) as tungsten carbide for it since there doesn't appear to be any damage models out there for Molybdenum and they are similar materials, in the same column of the periodic table.
Is this normal behavior? What exactly do all the red particles from the projectile mean? Is there a way I can get a more accurate simulation where the core doesn't just break into a node sized element? I was expecting something along the lines of this simulation: https://www.youtube.com/watch?v=XYuKWuyKXII. Granted, theirs are are against an angled armor, but everything correctly fragments in that simulation.
Any help on this is greatly appreciated!
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RE: AutoDyn Bullet Impact Analysis Help
Can you say more about those hand calculations ? What was your approach in this regard ?
RE: AutoDyn Bullet Impact Analysis Help
Attached is my document used to compute penetration depths. They mostly vary from one another, but even the ones that take into account more details say it can penetrate the depth I am looking at. The only formula I didn't use was Thompsons Formula (original, not F-Formula)because I couldn't find the values for which AR500 and Molybdenum under pressure begin behaving like a liquid rather than a solid.
RE: AutoDyn Bullet Impact Analysis Help
RE: AutoDyn Bullet Impact Analysis Help
The simulation (4.5 hours)I posted had the density cutoff option as "density limited" instead of "delete node". Upon changing to delete node, estimated times to solve for the full cycle (bullet exit after successful penetration) has steadily been climbing. I cut it at 135 hours estimated and 11% complete. Originally it predicted 22.6 hours. I tried messing with minimum and maximum density factors too but that didn't change anything. Guess I'm just gonna be stuck with having all these extra particles, because no way am I going to run a 135+ hour simulation without knowing if it will even work as intended. maybe there is another way to limit it that won't nuke the time to solve?
RE: AutoDyn Bullet Impact Analysis Help
To reduce the time required to complete the analysis you could use a proper level of mass scaling (but only for a small set of elements - those with the lowest stable time increment since it’s not a quasi-static simulation).