strain-life method fatigue properties for A286 fasteners

[ThereAre4Lights]

Hello,

I have been looking into the fatigue life and strength of bolts and have come across NAS6704, who's spec states that it is made of A286 UNS 66286 material. I've looked into finding cycles to failures using a developed S-N curve and also looked into the strain-life approach per guidance provided by Shigley (Basquin & Coffin-Manson). However, Shigley references SAE fatigue material properties for the fatigue ductility coefficients, fatigue strengths component, etc. These are some of the components of the strain-life equations. Doing research it seems that SAE never incorporated A286 steel so I don't think there is an equivalent grade I can use to obtain this type of fatigue data.

(Further research suggests that A286 bolt material is different from ASTM A286 but the inclusion of the UNS number seems to suggest they are the same material)

I've read and it seems that someone else addressed a similar topic before here: thread2-437640
However it is unclear whether the original poster found a solution with respect to fatigue properties of this bolt material.

Do you guys know any more information regarding this bolt material and how best to get these types of properties to get a sense of fatigue life of the bolt? My other approach was to look at the Gerber failure criteria and at least see if my fastener is OK.

Also, another thread that proved insightful (thread31-421686) mentions "Fatigue Analysis of Aircraft Bolts" by Brilmyer and I cannot find this document at all--> search results just yield citations and a link back to the thread I found it in. Is this a proprietary document or simply extremely rare and not digitized?

Any information would be great and much appreciated!!

 

[WKTaylor]

Shear? Tension? Combination Shear-Tension?

Suggest You start with a detail look at NAS6703-to-6720 and NAS4003...

NOTE.
NAS6703-to-6720 procurement specification is per NAS4003... which includes mandatory fatigue tests.

Within NAS6703--6720 is the following statement...

PROCUREMENT SPECIFICATION: NAS4003, EXCEPT AS NOTED. COLD WORK OF HEAD TO SHANK FILLET RADIUS AND
FATIGUE TESTING ARE NOT REQUIRED FOR NAS6703 BOLTS. LOCKING ... ... SEPARATELY.

NAS4003 FASTENER, A286 CORROSION RESISTANT ALLOY, EXTERNALLY THREADED, 160 KSI Ftu, 95 KSI Fsu, 1000 °F

Within NAS4003 is the following fatigue-test requirement...

TABLE I – BASIC REQUIREMENTS
FATIGUE TEST
Fasteners shall be capable of passing test
cycle requirements per TABLE X when
subjected to the loads per TABLE IV.
Test per MIL-STD-1312-11 in
accordance with NASM1312-11 TABLE X.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[ThereAre4Lights]

Thanks for the information Wil. Focusing on tension at the moment but I suppose combined tension-shear is where I'm heading towards for some locations. I am interested in finding theoretical methods for estimation of life,not necessarily actual testing methods since I'm working on something new with no actual fatigue test data as of yet. What I found was that for evaluating LCF and employing strain-life methods, I need a series of constants that SAE provides for a number of metals. However I could not find data for A286 =/ I'll keep looking but I will also focus on stress-life (S-N) methods and failure criteria methods (Gerber, Goodman diagrams) to get a sense of life for the bolts I am working with.

So yeah, is "Fatigue Analysis of Aircraft Bolts" by Brilmyer a unicorn document?

 

[WKTaylor]

TA4L... hmmmmm... do you have relationship to Heinemann's Hot-Rod [Scooter?]....

Rarely have I seen aircraft fasteners disassociated with fastening practices and the materials they fasten to/thru... Since all-types of aircraft fasteners have made leaps in quality, strength/durability, mass-saving, etc... even since I started-working in the late 1970s.

The hole tolerance/quality and the material being fastened [IE: tensile/shear modulus, shear/bearing/tensile/compression strengths, fracture toughness, corrosion durability, etc] are usually equally/more critical to the fastened-joint relative-to the fastener doing the fastening.

Never heard of "Fatigue Analysis of Aircraft Bolts" by Brilmyer ... couldn't even ID it by Google or the Corporate library... none-the-less the title 'sounds' makes this document sound fairly ancient, IE: 1950s era[?]. A similar titled doc [DTIC} 'Fatigue Analysis of Aircraft Structure' was ~1966. IF the author is 'HG Brilmyer', then their work was 1940s era... about the time that male fastener quality/design/fab was beginning to get real attention due to wartime urgencies.

Try Googling 'Fatigue Analysis of Aircraft Bolts' several good articles are listed

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[crackman]

ThereAre4Lights

I am the one who posted the reference to the Fatigue of Aircraft Bolts by Brilmyer, it was published in 1995 in the Aeronautical Engineering Review, just need to search a bit more. You can certainly find it if you are an AIAA member. It is a very good summary of some testing which is still valid today. Very little structural test data looses its value over time just may not represent your current needs. In particular, this paper details the benefits of the huck bolt and its swaged collar, something alot of folks today lose sight of. Due to the swaged collar, a Huck has a much better fatigue performance for vibration areas than any standard nut or collar. Anyways, paper also compares to Sn curves for standard AN bolts in fatigue as well. Just as a note on currency, the test fixture used in this "old" paper is the very same used in the standard fatigue tests of current day Hi-Loks.

Anyways, there is a wealth of literature on fatigue of bolts, just need to research a bit harder, something you will hopefully learn with gaining experience. The first place to look is ESDU. There are several: 67020 Fatigue Strength of Steel Screws; 80028 Fatigue of Tension Bolts; 85021 Fatigue of Tension Bolts Fittings to name a few. In addition, the Hi-Shear Specification 342 will give what various Hi-Loks are qualified to in terms of fatigue cycles.

Lots of data out there, just need to learn how to find it and what your actual application is.

Good Luck

 

[ThereAre4Lights]

Thanks everyone! I'll keep digging!

 

[rb1957]

worst case is do your own testing. Better for you, specifically tailored to your design, but costs you more !

It shouldn't be extremely expensive to test … off the cuff I'd run maybe 5 specimens at 4 different loadings (2 different preloads, 2 different shears).
Aim to have unfactored fatigue life about 10x your design goal.

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

Crackman... Please advise...

NOTE
"I am the one who posted the reference to the Fatigue of Aircraft Bolts by Brilmyer, it was published in 1995 in the Aeronautical Engineering Review, just need to search a bit more. You can certainly find it if you are an AIAA member..."

I just checked AIAA ARC

https://arc.aiaa.org/action/showPublications

for the cited document title... not a single hit. When I queried on the phrase "Fatigue of Aircraft Bolts" found lots of great fastener documents [thanks!!]... but nothing close to the document You cited.

NOTE.
"...Anyways, paper also compares to Sn curves for standard AN bolts in fatigue as well...".

Other than IPB [parts manual] listings for AN bolts [in low performance applications], I haven't specified 'AN's' for any application since late 1980s.

NOTE. Pin-pull swaged-collar lockbolts are superior to most HL installs... especially on a cost-performance basis up-to their diameter limits [D 0.375+OS]. The obvious advantage to threaded pins is that the HLs can be procured in a far wider diameter/head-style/OS ranges... up-to the limits of most LA steel, A286 and Ti bolts.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[WKTaylor]

This might be useful…

NASA/TM—2012–217454 Aerospace Threaded Fastener Strength in Combined Shear and Tension Loading

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[crackman]

WKTaylor

Sorry, the date of the issue is 1955, not 1995. As soon as I have a chance I will dig it out and let you know exactly which issue that year. Sorry for mix up.