Fatigue justification of a thread bolt

Claudio_F84 · Jun 16, 2025

Hello everybody,
for an urgent repair on an Airbus airplane, the designer creater a doubler of steel, connected to the aluminium fitting through two bolts.
I need to justify the threads for the bolt and the aluminium fitting taking in account shear and tension load simultenously.
Now, I do not find any method that takes in account both of them but only pure tension or pure shear and ISAMI as well does not have any module for that.

Do you have any method to suggest? I need to reach 2000 FC to start the repair action.

Thanks and best regards,

SWComposites · Jun 16, 2025

1) suggest you delete and repost in the Aircraft Engineering forum
2) can you show a sketch of the joint?
3) is the bolt threaded into the fitting? (I hope not) or a thru bolt with proper nut/collar on it?

rb1957 · Wednesday at 3:58 PM

yeah, I got nothing ! I assume you're repairing an Airbus beyond the SRM. Beyond the analysis and such, this'll require an approval (we'd call it a Repair Design Approval, but you may call it something else). That requires certification.

Where is this repair ? Pressure cabin, interiors, wing, landing gear ??

What fatigue load would be relevant ??

As above, I hope you're using a plain shank (not a fully threaded bolt).

Way more details needed !!

Ng2020 · Thursday at 11:44 AM

I am trying to understand your problem description and I can only imagine that you have threads in bearing. Can you not install a longer grip length bolt?

WKTaylor · Friday at 12:00 AM

I thought I was a 'fastener guy'... but this is unintelligible to me.

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Fatigue justification of a thread bolt

Claudio_F84

New member

SWComposites

Aerospace

rb1957

Aerospace

Ng2020

Aerospace

WKTaylor

Well-known member

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