Commonly known Power Law Creep model, depends on the equivalent Mises Stress (q), the problem is that in a rock (shale), initial Mises stress is non zero however rock is not creeping at this stress. Hence, it is necessary a higher equivalent mises stress to generate creep strain, but in Abaqus it is assumed that creep strain will be generated for any Mises Stress above zero.
Does anyone know if there is a way in Abaqus to set that creep will be only generated aboved certain stress?
Thanks
Abaqus uses power law creep expression to calculate the creep strain . Hence, as long as there is equivalent or von-Mises stress , there will be creep strain addition in each step. One solution is to write UMAT in which you can define the triggering von-Mises stress condition for creep strain to occur.
Good Luck
There is no need to go full UMAT. You can use the user subroutine creep to define your own creep law; see the user subroutine manual. If you simply need power law with a threshold, that should be easy to do.
The creep strain is evaluated through the power-law creep equation. Then, you can use subroutine creep to characterize a creep law according to what you want. This link may be helpful
https://abaqus-ocs.mit.edu/2017/English/SIMACAESUBRefMap/simasub-c-creep.htm
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