plasticity induced fatigue crack closure

hi friends am doin my my project on" FEA of plasticity induced crack closure". my specimen size is 80*80 mm. by using symmetry condition i modelled 1/4th of model in ANSYS. therfore i created 40*40 mm plate. with initial crack length of 4mm.means its MT specimen of 80*80mm with 8 mm crack length, by symmetry condition i modelled 40*40 with 4mm crack lenth.