# Pre-stretch in calculix

Hi there,

I’m trying to apply pre-stretch to my model. I find the *PRE-TENSION card, but I didn’t see how to apply pre-stretch directly. Anyone can help? Thanks!

*PRE-TENSION SECTION is used to apply preload to bolts. In this case you should use *INITIAL CONDITIONS keyword. This way you can define, among others, initial displacements, stresses or plastic strains.

Thanks for your reply. I tried this card several times, but it doesn’t work.
In the manual, it says:
Following line for TYPE=PLASTIC STRAIN:
• Element number.
• Integration point number.
• Value of first plastic strain component (xx) in the GLOBAL coordinate system x-y-z.
• Value of second plastic strain component (yy) in the GLOBAL coordinate system x-y-z.
• Value of third plastic strain component (zz) in the GLOBAL coordinate system x-y-z.
• Value of fourth plastic strain component (xy) in the GLOBAL coordinate system x-y-z.
• Value of fifth plastic strain component (xz) in the GLOBAL coordinate system x-y-z.
• Value of sixth plastic strain component (yz) in the GLOBAL coordinate system x-y-z.

So I put following sentences in my inp file:

*INITIAL CONDITIONS,TYPE=PLASTIC STRAIN
S8R,5, 1.1,1.0,1.0,1.0,1.0,1.0
where s8r is my elset.It shows my following errors:

*ERROR reading *INITIAL CONDITIONS. Card image:
S8R,5,1.1,1.0,1.0,1.0,1.0,1.0

It seems that the element set is not supported in this syntax? May I ask how can I apply pre-strain on the whole element set? Besides, what number should I give for the integration point number? Thanks!

Unfortunately, you can’t use elset name for this keyword, it has to be an individual element number. So the definition has to be repeated for each element and integration point. Also, keep in mind that those are plastic strains.

For the numbering of integration points, check the description of a particular element type in the manual.

Thanks, are there ways to implement elastic pre-restrain? All I need is to apply a pre-stretch of my beam.

You can simulate the preloading by applying proper load in an additional step preceding the one with actual analysis. Just be sure to turn NLGEOM on.