Hi, I am trying to simulate this aluminum ring curling in on itself when a force in the negative y direction is applied. I am running a 2-D asymmetric simulation. My problem is that even though I specify a no penetration self contact, the ring penetrates itself as you can see in the image. Can anybody explain what I am doing wrong?

Below is the file if anyone wants to give it a go: https://drive.google.com/drive/folders/0B5FhmW6_LqMKTDRQQzFfQWVvaEk?usp=sharing