Fastener dia Vs fastener load
Fastener dia Vs fastener load
(OP)
Will fastener dia increase (oversize or nominal)from blueprint increase fastener load? For example, in Wing shear tie foot to skin joint there are usually 3 or 4 fasteners. If one of them is changed to next oversize (1st or 2nd)or next nominal will the fastener load change? From stiffness perspective, it should change. The question is how much? Is it D_new/D_bp, D_new^2/D_bp^2 or by Huth criteria? How will it be different for shear critical or bearing critical joint? Thank you
RE: Fastener dia Vs fastener load
So if you are working from a repair standpoint, which you may be if you are oversizing, the Swift model would be most conservative. I would simply do a comparative load transfer analysis to figure out the difference.
As for other effects, you may want to consider:
1. Change in the bypass and bearing stresses on the hole due to the increased diameter / bearing surface / new R/P. This will have an effect on the macroscopic crack growth.
2. Changes (if only slight) to the interfastener ligament. If you have to O/S several fasteners this is more of a concern.
3. The increase in diameter may actually reduce the hole severity factor (all other variables held constant) however:
4. Is the fastener countersunk? If so this would also affect No. 4
Keep em' Flying
//Fight Corrosion!
RE: Fastener dia Vs fastener load
There are a bunch of other things to consider, like edge distance, spacing, …
An important thing to note is avoid mixing fastener materials and types.
another day in paradise, or is paradise one day closer ?
RE: Fastener dia Vs fastener load
RE: Fastener dia Vs fastener load
another day in paradise, or is paradise one day closer ?
RE: Fastener dia Vs fastener load
In addition to rb1957's comments I would say this:
Your first step is to look at the SRM and figure out if this is actually FCBS. Since you say the "foot" to skin joint, I assume we are dealing with lower wing skin, so it probably is.
What is the context of this action? Is this a deviation from an approved repair?
As far as analysis, what we have described above figuring out the new load transfer is probably necessary either way, but you have a couple options. You can do an absolute analysis which will require you to conservatively estimate the stress in this piece of structure (not necessarily simple in this scenario).
Or you can do a comparative analysis with only a relative stress. So, if there is a Cat B SRM repair you could put here, or this is just a deviation from some approved configuration you could do a relative analysis.
Please also watch out for any SSI's or ALI's in the area. You haven't mentioned the A/C model so I'm not sure if there would be any.
Keep em' Flying
//Fight Corrosion!
RE: Fastener dia Vs fastener load
Can anybody shed some light on how non-deburred condition affect fatigue life of a joint?
If fastener installation calls for clecos or temporary fasteners, can burr be formed between plates?
RE: Fastener dia Vs fastener load
plenty of aircraft accidents have been caused by damage initiated by a burr.
you're not, I hope, working on your own; so there should be a "typical practices" book around … your standard manufacturing processes, your standard engineering design practice.
FAA AC43-13 is not a bad place to start. I'm sure there's lots of stuff out there (like "repair design" engineering courses) that'll let you.
"good" places will size up a doubler, temporarily install with clecos, then full size the rivet holes, remove the doubler, deburr, install dblr with fay seal and clecos, and rivet away.
But there are also plenty of places that'll fit with clecos, remove dblr, install with fay seal and clecos, and then full size the holes and install rivets.
No one can say either procedure is Right or Wrong.
What sort of structure are you dealing with ? 'cause if it's secondary structure, then it's game on !
another day in paradise, or is paradise one day closer ?
RE: Fastener dia Vs fastener load
IT IS MIND BOGGLING the degrading effect that retained burrs can have on aircraft structure.
Regards, Wil Taylor
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