Spring preload F=k*x+F_0

[coach32]

I need to modelize a system that inclued several springs in a preload position.
Objective is to run a dynamic analysis with NASTRAN sol700.

I planned to use a bar element with a spring material property, but I don't know how to define the preload status.

Thank you in advance for any tips.

 

[mburlone]

Hi Coach,

I too am looking to include springs with preload. In Nastran, you can define a CBUSH1D element, and then reference a table for force vs. displacement. If in the table zero displacement equals non-zero force, then you have a preload.

Only problem is, I can't figure out how to make Patran write a CBUSH1D card in the NASTRAN input instead of the regular CBUSH. If anyone knows the answer to this, you'd be helping both me and coach!

Thanks!

 

[coach32]

Hi mburlone,

Thank you for this tip.

I think that there is no way to define CBUSH1D with Patran, you have to do the modifications directly in your *.bdf file.

The only problem in my case is that I am not sure that the CBUSH1D element is available for NASTRAN sol700, due to translation to LSDYNA code.

 

[coach32]

Hi mburlone,

I have received a solution to modelize preload springs !

You can define a CSPR element (Spring with Offsets).
It use a PSPRMAT property and Material MATS01, and supports preload.

Small limitation is that the OFFSET option is not supported by PATRAN so you have to change it in the *.bdf file.
But there is no problem because you always have to change the *.bdf file before to run NASTRAN !!