Another Bolt Preload Question...

[Ld3Ake]

Hi guys,

I am sure there are many of you who have done a 3D bolted joint model. At the moment I am trying to validate my FE model, and so I am currently using this paper to benchmark my results:

http://www.sciencedirect.com/science/article/pii/S026382230400340X

Three-dimensional finite element analysis of single-bolt, single-lap composite bolted joints: part I—model development and validation, Mccarthy (2005)

My model has been defined with three nonlinear steps: the initial, one for the bolt preload only, and then the final one for the load I want to apply.

In the bolt preload step I have created a partition at the mid plane of the bolt, selected the interior surfaces, and then applied a force. During this step the model is clamped at both ends to prevent rigid body motions.

In the load step I apply a displacement to one end, leaving the other end fixed. The blot preload is propgated into this step. When I look at the results something has definitely gone wrong as I get excessive deformation in only the elements on the mid plane (where the bolt preload has applied). Has this happened to anybody else or do you know what may be going wrong?

Thanks

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1439288080/tips/Joint_force_preload_knfkfz.tiff[/url]

 

[StefCon]

Hello,
So the bolt becomes strange when you apply external load in your model?
Did you change the bolt load to "fix length"? If not, add a step for that. Fixing length in the same step as applying external load caused me to get wrong stress results.

Report back with your findings! Good luck!

 

[Ld3Ake]

Ah, I see. Thanks for that, I didn't know you had to modify the step and tell it to "fix at current length". That has got rid of the weird excessive deformation at the mid-plane elements. Naturally of course, my results still don't match that of the paper, but at least I can move on to diagnosing other areas which maybe causing the problem (wrong BCs, loads, mateial inputs etc).

Cheers