Low Cycle Fatigue Analysis in ABAQUS

Hi friends,

Considering there are alot of people who are working on low cycle fatigue, i may need your help for one of my numerical model. I constructed a model in ABAQUS 6.10-2 and simulated a quarter model of a pipe that was subjected to a rigid indentor under zero pressure conditions. The indentor was then removed and elastic rebound was calculated. The pipe was then subjected to some pressure (65% SMSY) and then the pressure was ramped to zero and inelastic rebound was calculated. The model worked fine upto this point. After that, i applied 25,000 cycles to  the pipe ranging from 36 -72% SMYS followed by 32,000 cycles ranging from 6.5 - 78% SMYS. Accoridng to literature, the pipe should have generated a crack by now, but when i checked my SDEG (stifness degradation) values in output, it reports 0 at all time increments. Furthermore,i checked element status and it was 1(which means element was fully active). I am using an elastic-plastic material model (X-52 pipe)I am unsure what might be wrong with the model. If not failed, the model should have atleast reported some stiffness degradation values but it said 0 at all cases. I am unsure what to do now as i m stucked with this problem for quite a while. I would really appreciate if someone who has worked on LCF in ABAQUS can help me in this regard. It will be highly appreciated. Thanks alot

P.S Does this might have to do with the C1,C2,C3 and C4 material constants used in damage criteria of LCF in abaqus?

Waqas