Blind Rivet Use Cases 1

[EnginerdNate]

I'm currently looking into using flush head blind rivets on a simple system I'm designing. I have come across several different rivet specs and very little information on which rivets typically get used for specific applications. Specifically, I've seen a lot of references to the NAS1921, NAS1399, and MS90353 specs, the first two being true rivets and the last usually referred to as a blind bolt. I'm a bonded composites guy normally and the tribal knowledge at my current job is a little thin.

Can someone provide the cliffs notes for aerospace grade blind rivet types (If you like, including any you like that I've not found so far) and their applications? MMPDS-10 has no data for the NAS1399 for installed strengths, so my gut check says it may be falling out of favor if they aren't bothering to keep the data updated.

My application is a medium load (~2000 lbf shear limit load) single shear joint between two flat plates. I am constrained to using flush head fasteners due to space constraints and am looking at rivets to avoid the need for a complicated blind-fastener system.

I have some other features that make locating the part simple, so match drilling through an undersized pilot and pulling 4-8 blind rivets seems like the simplest solution to my problem.

Thanks,
Nathan

 

[WKTaylor]

RB... observations from field experience and 'documentation received' over many years...

I tend to be very conservative when installing rivets thru adhesive bonded structure... even a single/thin [0.007-nominal] adhesive-bondline can be damaged [crushed/delaminated] by 'excessive' tail-forming forces concentrated at/around hole-edges. This is why backside sheet strength/thickness is very critical for BRs and BBs.

Also, total adhesive-bonded stack-up depth is critical VS hole size VS solid rivet alloy/temper during bucking/squeezing due to radial forming/forging forces.

NOTE.
I 'have' a paper from one of the major GA companies stating that anytime a solid rivet was buck/squeeze-set in a hole of exact/known [measured] hole size, in a typical -T3/T42 sheet material... and was then drilled/punched-out 'by-the-book'... there was always a MEASUREABLE growth in hole diameter due to compressive 'yielding' by the expanded rivet-shank. YEP... I have actually seen this phenomena... including a slight thickening [pillowing, volcano-lipping] around hole edges, which can be delaminating [due to prying forces].

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]

 

[EnginerdNate]

We've got a ton of MS90354s here in 3/16" and 1/4" shank sizes, so my best bet is probably to find a scrap panel, cut a section out of it and do a few test pulls.

 

[rb1957]

the down side I see is the steel fasteners will take a lot more force to squeeze.

the up side is there would be much less swelling.

I think maybe you need a NAS spacer to reinforce the laminate hole.

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

 

[WKTaylor]

EN...

IF bound/determined to use MS90354s, then be wary of potential corrosion Issues.

Suggest coating drilled/csk holes with epoxy primer [allow-to-dry]; followed by 'wet-sealant' Assy [fay-surfaces and fastener install] to Isolate aluminum from the steel.

After install, over-coating PTH BB head with primer and/or sealant for total Isolation to prevent head 'rust'.

Any chance of installing MS21141 PTH SStl BBs [softer tail formation, Cd plated sleeve] instead?

Take a look at Cherry CR7773S titanium BBs...



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]

 

[EnginerdNate]

Thanks Wil, I'll check those out.

There's a lot of things I'd like to do differently on this program (fastener choices often being one of them) but there's a lot of institutional inertia going on here.

Aren't the MS90353s Cd coated as well?

We use an absolute ton of polysulfide sealant on this program. I wouldn't even be questioned if I specced that all of the rivet heads were to be covered in a blob of it.

 

[EnginerdNate]

Wil, were you recommending the MS21140 (Flush version of MS21141) in CRES vs the MS90353 in alloy steel?

This Cherry page has the two cross listed as the same product.

http://www.cherryaerospace.com/product/blindbolts

 

[WKTaylor]

EN...

OK... conflicted/confused... In Your '3 Jun 19 19:06' post You stated... "We've got a ton of MS90354s here in 3/16" and 1/4" shank sizes...".

SO went back to Your figure and realized that You really intend to use FTH BRs or BBs in this joint... Duhhhh..

MS21141 is the [A286] version of MS90354 [steel] Protruding Tension Head [PTH] BB.
MS21140 is the [A286] version of MS90353 [steel] [FTH] BB.
NOTE. The MS2114* A286 SStl BBs have a shear rating of ~95-KSI the MS9035* steel BBs have a shear rating of ~112-KSI

OH, BTW... one CAUTION regarding blind bolts VS blind rivets VS rivets VS bolts/nuts... BBs are ~5X harder to remove than BRs; which are ~5X harder to remove than solid rivets; which are ~5X harder to remove than a bolt into a nutplate [or blind nut].



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]

 

[EnginerdNate]

Sorry for the confusion. We use the protruding head version in a couple of different applications so we have those in stock. I'm not sure on the 90353 FTH versions. My thinking was that for checking for cracking or deformation during bulb formation the difference between the two would be minimal.

95 KSI Fsu is more than adequate. Every calc I have at the moment is pointing to the aluminum extrusion letting go long before the fastener shank.

With A286 CRES in aluminum I'm assuming install with a sealant is not optional due to galvanic mismatch. EDIT-Pulled up the actual spec. I'm not used to seeing Cd plate available on A286 fasteners. So theoretically as long as the Cd plate isn't damaged install in aluminum shouldn't be a problem. Install with a sealant is still probably preferable.