Countersunk joint analysis

[CoryPad]

For aircraft joints with preloaded countersunk fasteners (like Hi-Lok, etc.), what equation(s) are used to match joint bearing area with fastener preload? I am not interested in analyzing the joint's resistance to shear forces, only analyzing the bearing stress generated during assembly.

For example, for conical nuts used to attach automobile wheels, SAE International recommends calculating bearing area with a combination of bolt tension + torque induced shear stress divided by wheel yield stress.

Hi-Lok's have anti-rotation features on the point, so only axial force is present. Is the preferred equation simply bearing area must equal or exceed fastener tension divided by conical surface area?

Regards,

Cory

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[Lcubed]

Cory,
As a first try, I would suggest that you contact Hi-Lok. I assume that in setting the fracture point of their products they needed to consider possible damage to soft materials. They should have some very good data on loads and stresses in the countersunk sheet.