How to simulation dogbone tensile specimen in ANSYS

[Riyada]

Hello!
I am using Ansys workbench to simulate polypropylene tensile specimen. I choose Transient mode link with Explicit dynamics mode to simulate it. i set fix support to surface and velocity 0.8333 mm/s on opposity surface. I meet necking of specimen but I didn't see colddrawing. In general tensile testing of plastic specimen, We always meet colddrawing in middle. How to simulate colddrawing in middle of polypropylene tensile specimen?

What Engineering data?
What Element type?

Thanks for your time!

 

[fuzzdoug]

what type of material model are you using?
open the ansys help and look up the path:

// Mechanical User's Guide // Appendices :: 0 // E. Material Models Used in Explicit Dynamics Analysis