Bolt bending formula in single shear joint 1

[kilbchoi]

Hi !

In single shear joint, I normally pick up the bending moment arm
with the half of assembled length. I've checked all references, but
I couldn't find a formula of the subject.

I blieve that moment arm is conservative. I need less conservative
but more practical formula especially for quite thin member joints,
Let say M6 bolt with two 2mm thick AL members.

Anybody who can help me ?

Sincerely,

Kilbchoi

 

[CoryPad]

I have never seen a mathematical treatment for this issue either. I suppose the reason why is that it hasn't been a big problem in the past. If the joint is a shear-friction type, then joint failure occurs when the joint slips. If the joint is a shear-bearing type, then the joint fails when the hole bearing stress is exceeded. If these occur but the parts are still fastened, then calculating the screw bending stress could be useful to determine final overload force. Perhaps you could do some work on this and publish in a technical journal. Good luck.

 

[KSshopper]

The effects of bending become apparent in shear critical joints, and even then only on thick stack ups. MIL-HDBK-5 has joint allowable tables for various fastener types, diameters, material thickness and types. For the bigger diameters and thicker stackups, you will find the max joint strength is less than the bolt shear strength. This is due to effects of bolt bending.

I believe the M6 bolts in a 2mm single shear stack up would fail in bearing, the effects of bending not being critical.