Pretension analysis

Question

Hii everyone,

I have this confusion. I performed pretension analysis in a bolted joint. The bolt is modelled as 1D Beam element, a 18kN Pretension force is applied.

The thing is when I simulate that, the displacement and stress are 1500 mm and 1000 MPa, the components joined together by the bolt, went directly inside into each other. Shouldn't they stop each other at their surface interaction, I mean collide. I even tried using contacts between them, still they went inside each other.

It is okay or any error in the simulation. Is the pretension force too big, But in reality we apply upto 400 N-m, which may generate upto 160kN of force.

Because I need to call that pretension subcase in another subcase.

For the above situation when i called the above subcase in another subcase using STATSUB(PRETENS) the displacement i got is 5mm, which is good and realistic.

Rajashri_Saha · Answer

When you have contact defined in your model it is no more linear. you have to add non-linear parameters like NLPARM/NLCTRL. You should add frictional contact with PCONT card.

Mintu · Answer

Isn't CNTNLSUB for non linear, This is a linear static analysis.

In contacts we have SLIDE, FREEZE and STICK contact, but we also have Static Fric contact also in optistruct linear static. If we enter mue as 0.1 or 0.3 will there be any difference in simulation results. Will the mue act as friction contact in simulation or its just a FREEZE contact.

because i dont see any difference in my results.

Rajashri_Saha · Answer

There must some issue with contact definition which you need to verify. 18KN load looks reasonable.

Once the pretension load is acting, the bolt length should shorten which confirms the pretension is acting properly.

For the 2nd subcase I assume you have used CNTNLSUB along with STATSUB(PRETENS).

You can check some reference video or tutorial available online for setting up 1D pretension.

Thanks

Rajashri