Learning Forum

[shahiupendra11]

Hi Everyone,

I'm trying to put bolt pretension to the given model. This setup has clearance hole as hole is bigger than the bolt thread radius. The bolt is connected to Stiffening Plate (Solid) by fixed joint, and the bolt is connected to the base by bonded contact.

When I put the bolt pretension to the bolt (solid) half without the thread, the convergence depends upon the material properties of Middle Plate (Shell). Let's say I have 3 materials A (Linear Structural Steel) ,B (Multilinear Grade 9 Bolt) ,C (Multilinear A36). The solution converges for material A and B but not for C. 

 

 

Why would the bolt pretension convergence depend upon the material used and how?
Any insight will be appreciated

Thank You
Upendra

[peteroznewman]

Hi Upenda,

Shell elements are constrained to have zero through-thickness stress so they are not recommended for models that have large through-thickess compression loads such as bolt pretension. I recommend you revise your model and use solid bodies for all three plates and the bolt.

Make sure you split the cylindrical bolt face to separate the length where the bonded contact holds onto the hole in the base plate so that the face you apply the bolt pretension load is not involved in a bonded contact.

[shahiupendra11]

Thank you for the suggestion Peter.
Can I ask why it converges for some materials but not for others?

Thank you

[peteroznewman]

Linear materials are less likely to cause convergence issues compared with nonlinear materials that have plasticity. The simple example is when the tangent modulus is zero which means the elements that have exceeded the yield strength have no ability to carry more load, they can only deform.  If the entire cross-section exceeds yield before the solution applies the full load, there is no static equilibrium at the next load increment and the solution fails to converge.  This YouTube video illustrates that behavior: https://www.youtube.com/watch?v=qMmEhZll0kI

[shahiupendra11]

Thank You so much for your suggestion and time Peter.