nonlinear static analysis (601) convergence problems

[nacho890]

Hi!! I’m trying to do a nonlinear static analysis (601) with NX Nastran but it doesn’t converge. It’s a sandwich beam subjected to pure bending load. Pure bending is modeled using an enforced rotation constrain applied to the ends. Grabbing the ends of the sandwich there are both steel parts. Both clamps are putting pressure on the end parts. The enforced rotation constrain is applied to the clamps.
Elastic materials: GFRP orthotropic, foam isotropic, steel.
Contact between beam & end part :
• Coefficient of static friction: 0.2
• Advanced nonlinear parameters (BCTPARA): initial penetration (INIPENE) eliminated; consistent contact stiffness (CSTIFF) used
Contact between end part and clamp:
• Coefficient of static friction: 0.2
• Advanced nonlinear parameters (BCTPARA): initial penetration (INIPENE) overridden; constant gap distance (GAPVAL) -0.02mm* ; consistent contact stiffness (CSTIFF) used.
* I would like to put pressure on the ends not by a force but using an initial penetration.
I am using symmetry conditions so I’m only modeling half.
DOF 1= same as bending vector. DOF 2=along the beam. DOF 3=vertical.
Constrain at the end: DOF 1 fixed; DOF 2 free; DOF 3 fixed; DOF 4 enforced 40 degrees; DOF 5 fixed; DOF 6 fixed. I use these restrictions deliberately to allow the ends to approach.
Constrain at the half: all free except vertical displacement, DOF 3 fixed.
Parameters of the solution: incrementation scheme TLA-S. Others parameters have the default value.
Thanks in advanced