MSC NASTRAN: NLSTEP for nonlinear problems (SOL 400)

[Mechaero2006]

Hello.

I was wondering if it is possible for someone to post his/her experience from the use of the NLSTEP solution stratery (-gies) for tackling nonlinear FEA problems that include composite materials (classic examples as the DCB or similar are welcome). Other types of problems that you might have come cross and captivated your interest in terms of the solution used are also welcome. In addition, one might add his/her experience in using multi-step strategies for a single loadcase etc.

I am aware (as most users I suppose) that there is no "universal" solution that guarantees convergence and that this topic can be a lenghty one in terms of the answers given (assuming that fellow users will find it interesting and contribute to it), however it would be a nice start up for those interested in NL FEA in MSC NASTRAN (especially SOL 400).

Please excuce me if this topic (or similar) has been answered before. In that case a link will be useful.

Thank you in advance.

 

[Sleight]

I have experience in using SOL 400 nonlinear static analyses for composite structures. For the multi-step analysis, you define multiple steps each with their own loads, BC's, and a NLPARM card that defines the nonlinear convergence parameters. If you have a load or BC in one step and then remove it in the next step, then the load or BC will be removed in that nonlinear load step. There is a bug in earlier versions than 2013 that you have to define a pressure load in the last step in the nonlinear analysis or the results will be incorrect. This is fixed in the latest version of Nastran 2013.