CONVERGENCE PROBLEM ROTATION CORRECTION TOO LARGE

[gnappo]

Hi, I'm a new Abaqus user.
I'm modeling the aortic valve in the systole phase(opening) .I'm using S4r element, with application of a pressure on the bot surface of the valve leaflet.

I've a problem in the convergence of my model.
This is the end of msg file:

AVERAGE MOMENT 2.874E-04 TIME AVG. MOMENT 1.741E-04
LARGEST RESIDUAL MOMENT 4.489E-07 AT NODE 4281 DOF 6
LARGEST INCREMENT OF ROTATION 7.636E-04 AT NODE 4281 DOF 5
LARGEST CORRECTION TO ROTATION 2.157E-05 AT NODE 4281 DOF 5
ROTATION CORRECTION TOO LARGE COMPARED TO ROTATION INCREMENT


***NOTE: THE SOLUTION FAILS TO CONVERGE IN THE MAXIMUM NUMBER OF EQUILIBRIUM
ITERATIONS ALLOWED.


***ERROR: TOO MANY ATTEMPTS MADE FOR THIS INCREMENT

It is a nonlinear static analysis where I use:

*INITIAL CONDITIONS, TYPE=STRESS
PR_MOD,0.000002,
** Step 1, stat_nnlin
** LoadCase, Default
**
*STEP, AMPLITUDE=RAMP, INC=10000, NLGEOM
This load case is the default load case that always appears
*STATIC,STABILIZE,FACTOR=1.E-5
0.001, 1., 1.E-20

Has someone any tip?
Thanks.