Modeling joint bearing+pulloff

[MBD26]

Hello all

I'm working a joint on an aircraft former flange that has some significant pull-off load, in addition to bearing/thru. I'd like to model this with a solid fem, using either NXCAE or stresscheck. I have detailed solid geometry of the former with the fastener hole modeled, and I'm wondering if it's a good approach to just apply the bearing/pulloff loads directly to the open hole (no fastener modeled).

I would apply the bearing load directly to the bore of the hole (simple enough), and then my thought is to apply the pull-off load to a circular region of element faces concentric with the hole where the bolt head is flush with the flange surface (load application surface dia. = bolt head d). You wouldn't capture filled-hole propping effects this way, but I'd think this is conservative (not sure if it would be too conservative or not...). Also, you could correct the stress for any peaking effects afterwards.

Do any of you have any thoughts or experience with this? The only other method I can think of is to take the same solid fem and add in an actual solid model of the bolt, spread the load throughout the bolt with an RBE3 and run a contact solution. I'd like to avoid this if possible, though.

 

[SWComposites]

So what are you going to do with the results of the FEM? And what material is the plates?

Without test data to validate the strength prediction it's just a research project.

 

[MBD26]

I'm correlating results to a finding on a fatigue test article. Need the KtS at the hole and the stress gradient for crack growth. Al 7050 plate.

 

[SWComposites]

Having been down a similar road before, I doubt that you will get good correlation unless you include the effects of fastener clamp-up and hole filling. Unfortunately this probably means including a 3d model of the fastener.