Dear all,

I am trying to carry out some impact damage and i need to do some element deletion. I ran my model using ABAQUS/Explicit and the *SHEAR FAILURE, ELEMENT DELETION = YES option and the model runs fine where by the elements which fail show zero stiffness and zero stress.

Now i need to run the model in standard since i have written a UEL describing a cohesive element. For this case i have written a UMAT to make the stress zero. The UMAT works fine when i do a uniaxial test on a single element to check my stress-strain behavior. Now when i run this material model with my impact simulation, the simulation stops prior to the element showing zero stress. I got the following error ***NOTE: THE RATE OF CONVERGENCE IS VERY SLOW. CONVERGENCE IS JUDGED UNLIKELY. Hence i reduced my time step to the minumum but i still get the error.

I am a little lost as to what are the aspects i should be checking in my simulation. In the UMAT i have gone through it wherein i know i am not dividing by any zeros. For this case i set my Jacobian as a very small value. I have written the code using the radial return method scheme and i am carrying out implicit integration.

I know the question i have posted is a little vague but i just need some guidance and some helpful tips which i should keep in mind.

Thanking you in advanced