Effect of Hill Potential on Creep Analysis

Question - Does the Hill potential affect creep analysis?

Answer - Yes, Hill potential can affect creep calculations since the "effective stress" (Norton) term in creep will use Hill potential ratios. By default, the yield ratios are applied for both plasticity and creep. This means that the effective stress in the creep equation is based on Hill. To define separated Hill potentials for the plastic yielding and the creep flow (TB,HILL,,,,PC), issue two TBDATA commands, one to set constants C1-C6 defining the Hill yield surface for plasticity, the other to set constants C7-C12 defining the Hill potential for the creep direction. Below is an example.

MP,EX,1,20.0E5 ! ELASTIC CONSTANTS
MP,NUXY,1,0.3

TB,HILL,1,1,,PC ! HILL data table for plasticity and creep
TBDATA,1,1.0,1.1,0.9,0.85,0.9,0.80 ! Plasticity Hill parameters
TBDATA,7,1.0,1.0,1.0,1.0 ,1.0,1.0 ! Creep Hill parameters