Hi all. I am implementing a strain-gradient plasticity model as a UEL in Abaqus. My UEL only uses lflags(5)=0 (i.e current approximations to my unknowns(displacement and plastic strain) are based on Newton corrections) and doesn't change to lflags(5)=1 where the the approximations are extrapolated from previous increments. These causes my stiffness matrix(AMATRX), Nodal displacements matrix(U) and nodal displacements(DU) to be zero through out the analysis hence I get the "Illegal memory reference" (signal 11) error.
I noticed that at the beginning of the analysis(lflags(3)=4), lflags(5)=0, KSTEP=1 and KINC=1, but after initializing the AMATRX then I have lflags(3)=1(meaning the analysis is now using the normal implicit time incrementation procedure), however the flag doesnt change: lflags(5)=0 KSTEP=1, yet the current increment goes to zero: KINC=0.
Would appreciate help in regard to an explanation of why this could be happening.