Tiaxiality in unit cell calculation

Hi 

There are no built-in features in abaqus that will halp you with this problem. I struggled with the same problem myself, and the solution was to use lienar elastic spring elements to control the deformation. Meaning, I put one spring in the top center of the axi-symmetric model (top left corner) and one spring in the bottom right corner. To maintain a constant triaxiality level, you have to write a user subroutine UEL, that will control the relative deformation of the springs. What the UEL is supposed to do is this: if you pull the top spring, the bottom right spring should be pulled according to the wanted triaxiality level. In order to avoid point loads where the springs are attached, you can use constraints that makes the all top nodes have the same deformation as the node attached to the top left spring, and one that makes all the right nodes (circumferential nodes) have the same deformation as the one attached to the bottom right spring.