Can I assign bolt pretension to soild bolt with MAT/LAW13 ( Rigid)

Naresh

Hello,

I have assigned pre-tension load to bunch of solid both with linear steel properties. I have assigned very high Y stress so bolt wont get in to plastic state. But do see unrealistic stretching of bolt sometime. But we know these bolt wont give up based on our physical test data. 

So, as a quick fix, can I assign rigid material to these bolt? does pretension still work if bolts are rigid ?

 

Regards,

Naresh Kini

PaulAltair

No, LAW13 is deprecated/obsolete, you shouldn't use it for anything!

You should establish why the bolt is stretching more than expected, if the cross section and material properties are correct then why is it seeing more load than you expect?

Naresh

Hello Paul,

Yes, cross section and solid element set and material properties are correct. Does Tstart and Tstop values have influence? I have kept both as zero. Referring one of the presentation on 3D bolt pretension PPT, were Tstop is assigned as 10. 

Does pretension will end at Tstop=10ms? if so, does that value much less then 10ms? 

Regards,

Naresh Kini

 

PaulAltair

Hi, yes, the Tstop is important:  default value of Tstop is 1e30, so your model is never going to reach the original stiffness if you leave it at 0: You should give it some appropriate value in your model (in order of 10 ms is typical)

From help:

The preloading occurs at T_start. The material stiffness of the elements defined by cross-section is reduced and a tensile stress is applied to the elements. The stress creates the preload force in the bolt. Next, the material stiffness of the preload elements is increased until it reaches its original values at T_stop time. Refer to Preload in the User Guide for more information.

Naresh

Hello Paul,

IT worked. Thanks for the insight!!