Updated Lagrange formulation
I'm working on a finite element program and I find it to be a lot of fun. However, I have some questions that I would like to ask this excellent forum. When implementing a Updated Lagrange formulation for large strains, at what point should the coordinates be updated?? In the current implementation I update the coordinates in every Newton iteration. This works fine but I find it troublesome that a lot more information has to be saved during the analysis compared to a "standard" Lagrange formulation. The second option that I find is to update the coordinated when the Newton loop has converged, i.e just before a new load-step is to be done.
All comments are truly appreciated.
I would first want to clarify whether you mean coordinates as coordinate system (which changes due to large rotations, may be) or coordinates with reference to stress and strain.
I have worked with large deformations for quite some time and the way I do it is that I do not use updation scheme until I converge (i.e. get out of the Newtons iterations). However, within the iterations, you've gotto have some local variables being updated. This approach works pretty well for me.
One other thing I would like to know is how you take into account the large rotations ?