The most common cause of convergence problem in nonlinear
simulations is inadequate FE modeling.
Examples of inadequate FE modeling include:
- Defining conflicting constraints between boundary conditions, contact conditions, and /or multi point constraints
- Not adequately constraining the model-allowing rigid body motions
- Having incomplete (or inadequate) material data
- Using an inappropriate element for the problem
Another common cause of convergence problems is that the
physical system is very unstable, making it very difficult to find an equilibrium
solution.
Examples include:
- Buckling of thin-walled, cylindrical shell structure
- Snap-through with contact changes
- Compression of highly confined, incompressible materials (rubber)
- Development of local instabilities occur
In these cases it is important that the correct element type
and analysis techniques be used; otherwise, it can be very difficult to obtain
a solution.
