UMAT subroutine in ABAQUS

Hello,

I am a new user of Abaqus and its libaray UMAT. Since I need to perform some CPFEM simulations, I used Huangs’s UMAT code. I tried to execute the example input file and to replicate the copper case study reported in: “A USER-MATERIAL SUBROUTINE INCORPORATING SINGLE CRYSTAL PLASTICITY IN THE ABAQUS FINITE ELEMENT PROGRAM“. The simulation exits with an error when using the example input file due to numerical singularities and when I create my own input file I’m not able to obtain plastic strain and I only have elastic response for any displacement and pressure value. Something is wrong but I can not figure it out.

Has someone encountered this problem?

Does anyone have any idea what the problem might be?

Thanks in advance for your help.