Holes mismatch fatigue effect 3

[GGU]

The practice of copying existing holes from structure to repair parts like doublers or splices is used as standard.
Although it is assumed that the holes are completely aligned if you use guide bushing to transfer them between parts, if you take into account clearance between bushings and hole and btw. drill bits and bushing it is clear that there could be some mismatch between existing and repair parts holes.
I´m trying to find any reference that could help me evaluate the effect of that mismatch in the behavior of the structure, specially from the fatigue POV.

 

[KENAT]

I'm not expert but the techniques you mention should give reasonable alignment. Then assuming rivet holes, the rivets tend to swell when installed so I'd think they'd largely address this though I'd be interested to hear what others more expert in the field have to say.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[GGU]

As you mention the alignment is reasonable for rivets, but we are more worried about circumstances where we are using blind fasteners or hi-lite, which do not swell on installation.

 

[rb1957]

if you're removing a Hi-Lok, common practice is to go up a size to clean out the holes ... possibly an over-size, but they tend to be expensive.

 

[GGU]

For a hi-lok is easy to find OS pins (except for 5/32") but if we talk about blind fasteners sometimes your only option is to go to next dash, and that could be a problem with edge distance.

If we consider a situation where we have to discard all other options and have to live with the same size fastener (our situation), up till now I haven't been able to find any reference to help me determine the fatigue effect of the mentioned mismatch.

 

[MNLiaison]

One document that may provide some insight is "The Influence of Hole Processing and Joint Variables on the Fracture Life of Shear Joints", AFML-TR-77-167 Volume 1. They performed fatigue testing on a myriad of different "anomilies" that are typically encountered during fastener installation. They tested "Fastener Removal" for which they performed fatigue cycling of a joint, then removed and reinstalled the fastener and continued with the fatigue testing. There is also "shank contact area" and "angled" fastener hole variables that they fatigued out to determine their affects.

I pulled the document from DTIC and its free compliments of the US tax payer. It's too big to post but I attached the cover page for your reference. You might have better luck searching by the ADA number

Regards

 

[MNLiaison]

Below is a url to the citation to the mentioned document, of which you can select the link to download the file in it's entirity (82MB).

Regards

 

[MNLiaison]

Below is a url to the citation to the mentioned document, of which you can select the link to download the file in it's entirity (82MB).

http://www.dtic.mil/srch/doc?collection=t3&id=ADA054770

Regards