Hi, I am working on a ballistic impact study on a hybrid kevlar metal armor optimization using data from published literature. Currently, I'm building a baseline model consisting of only kevlar material with 7.62 ball bullet as impactor to observe the output velocity and kevlar deformation result . However, compared to the published literature, the output velocity are quite different.

In the referenced literature, the kevlar managed to reduce the bullet velocity from 430 mps to about 390 mps, while in my simulation the bullet speed is reduced only to about 425 mps.

From the d3plot images, the bullet seems doesn't undergo any significant deformation. where I suspect the contact definition has a problem (i dont know exactly which one, or even caused by other modelling problem)

I have also uploaded my keyword (.k) file. Would appreciate if anyone can take a look and advice me on what to do.

Thank you.