Trouble with PFM fracture in Abaqus 2021

[swahlgren]

I am running simulations with phase-field modeling (PFM) of fracture in Abaqus 2021. When I run a test model without cracks - a simple square in displacement control - the PFM user material behaves as intended, i.e. the damage parameter (temperature) changes with the stress.

Then, if I copy that model and introduce a crack; there's a stress singularity at the crack tip and stresses are thus very high here. However, the damage parameter does not change, so it basically behaves like an elastic model with no fracture.

I have also tried copying that model and removing the crack to test the tensile behavior of the material yet again and presto; it works like it should.

I have tried running models with PFM fracture from other people without luck; no fracture - just super high stress at crack tips and no damage to the material.

An idea could be that something is wrong with the umat file since I am supplying that but A) I have not changed the file and B) according to my own tests with tensile behavior of my simple model it (umat file) does what it's supposed to.

Ideas?

 

[FEA way]

Have you seen the article "A simple yet general ABAQUS phase field fracture implementation using a UMAT subroutine" by Y. Navidtehrani and E. Martinez-Paneda ? It mentions a website of the second author where multiple open-source subroutines are shared, including even a plug-in for PFM in Abaqus.

 

[swahlgren]

It's exactly that approach and umat I am using. I'll give their examples a try, thanks.