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Solid bolt preload quirk

Genius
Genius

Hello, The solid bolt preload functionality is "tweaking" my bolt sometimes. It happened in 2/3 of my runs. Is there a cure for this? I don't want to have to use thermal tricks to get my bolts up to load.

 

UPDATE: The coaxiality of the two halves of the bolt is varying from loadcase to loadcase within the same analysis - it is as if the preloaded layer of nodes is extremely flexible or something. MODEL IS ATTACHED.

 

Unbenannt.pngUnbenannt1.png

6 REPLIES

Re: Solid bolt preload quirk

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear Kava,

Check that is not related with the graphic scale of deformed shape, plot at scale 1:1, this is the first time I see this behaviour in solid bolt preload.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: Solid bolt preload quirk

Genius
Genius

The scale is 100x actual deformation. But the effect is influencing my results, because the bolted joint is very free (basically only friction and some light springs holding it together), and sensitive to perturbations. The shearing effect seen in the first picture is totally dominating the displacement response.

 

I need clean displacements because I'm analysing joint stiffness. In any case I'm sure it is related to the high value of the preload (M30 bolt, 90% proof load = 323 kN).

Re: Solid bolt preload quirk

Genius
Genius

Hi Blas,

 

I've attached the model now - maybe I've done something wrong? Thanks!

Re: Solid bolt preload quirk

Siemens Phenom Siemens Phenom
Siemens Phenom

Although you are not required to have coincident nodes merged at the bolt region interface, I recommend that you merge the nodes.   That will eliminate the displacements you are experiencing.

 

The bolt region is used for applying the preload, it is not a contact region.

 

 

Best Regards,
Chip Fricke
Principal Applications Engineer - Femap Product Development

Re: Solid bolt preload quirk

Genius
Genius

You were right that there were free nodes there, but after I zipped all nodes it still happens.

Re: Solid bolt preload quirk

Solution Partner Experimenter Solution Partner Experimenter
Solution Partner Experimenter

I have experienced the same issue with a model build in Femap v11.4.

With my model the axial direction of the bolt is Global Z-axis. Within the bolt region definition I therefore selected the Basic rectangular CS and Z-axis. Pre-tension will result in movement of the bolthead in Z-direction (axial for the bolt). The results show mainly global X displacement, which is the cross direction for the bolt.

The bolt is one Hex meshed solid, so no coincident nodes.