Lifting analysis

[izax1]

Does any of you have some good advice in doing a lifting analysis in NX/NASTRAN without getting into singularity problems. I use Gravity force and restrain the model in the gravity direction (Vertrical) I get singularities in the horisontal and rotatiobnal DOFs.

Thankful for any help.

 

[potrero]

Here's a good general article on dealing with singularities in NASTRAN:

http://www.endurasim.com.au/Content/pdf/EnDuraSim-Overcome-Singularities.pdf

 

[izax1]

Thank you, potrero, for the article. Appreciate that.

 

[BlasMolero]

Dear Izax1,
You need to restraint your model in the three directions X, Y and Z, then make your numbers. The best way is to define spiders using RBE2 elements in the lifting regions, then you have points (the core node of the RB2) in order to define clearly the BCs. You constrained the model in the vertical directions in the lifting points, lets suppose Z-axis, then TZ=0. You need to restraint the model in X & Y axis in two more points (core nodes of RBE2 elements), make the assumtion the most natural as possible, simulating followers. Do not over-constraint the model, do not define redundant constraints, make assumptions as soft as possible, run the analysis, and revise results of deformed shape & reactions, this will give you advice if things are done correctly, OK?.

Best regards,
Blas.

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Blas Molero Hidalgo
Ingeniero Industrial
Director

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