Modelling Crack propagation in a viscoelastic material using cohesive zone modelling in abaqus.

Hello everyone,

I need to validate crack propagation in a viscoelastic material using Cohesive Zone Modelling. I have given following properties as  fracture criterion. 

Damage initiation= MAXS damage, Normalstress=Shear1=Shear2=3.4MPa.

Damage Propagation:

Type: Energy,

Softening: Exponential

Degradation: Maximum

Mixed mode behaviour: Power Law

Mode mix ratio: Energy

Power:1

Fracture energy(Normal)=Shear1=Shear2=274J/m2.

My results are comparable till the peak point in load vs CMOD curve. But program is getting aborted once it reaches peak. I am not able to get the softening behaviour in the curve. Can anybody suggest me about this problem. Thanks in advance.

Regards

Prashanthi