Shear strength data

[ArunKumar Bala]

Can anybody tell me the shear strength of the NAS1669 Jo-Bolt fastener? I checked in the fastener specification I am not getting the value and I have gone through MMPDS-09 also. Nowhere I am to find the shear strength value.

 

[SWComposites]

Google and 3 minutes found these:

https://www.eng-tips.com/viewthread.cfm?qid=399202

https://trsaero.com/monogramaerospace/products/blind-bolts/visu-lok/

 

[ArunKumar Bala]

swcomposites thanks for your reply. But those websites are not standard ones to refer to in the design analysis.

 

[WKTaylor]

CAUTION1. Fastener shear testing has specific parameters... which may/may-not be applicable to your application.

Regards, Wil Taylor
o Trust - But Verify!
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", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[SWComposites]

the Monogram site lists shear stress values. Though WKT is correct, those values are based on specific fastener testing methods, typically double shear with high strength steel plates.
what exactly are you looking for if the Monogram data is not sufficient??
what is the specific application?
what is the specific joint details using this fastener?

 

[rb1957]

maybe the data isn't there and you need to test.

possibly the data is in earlier MMPDS (for some reason they dropped a lot of useful data around 06); or Mil HDBK 5

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[LiftDivergence]

My first question would be what type of design is this that would be using a shear critical joint application? I guess I can think of some, but overall it should be best practice to avoid shear critical joints. If the joint is not shear critical, the shear strength of the fastener won't really give you any useful information.

In most cases you need to have a transitional joint strength value based on either very specific analysis or testing.

Keep em' Flying
//Fight Corrosion!

 

[rb1957]

i think you need to know the shear strength of the fastener, to ensure that the bearing strength of the skins is less. no?

is this for a one off mod (where a limited number of tests would be reasonable) or a whole production run (where a statistically determined number of samples would be applicable) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[LiftDivergence]

Sure, but I think you're only going to be bearing critical for very thin layers.

For example, a typical steel or titanium hex drive bolt or lockbolt at ~95 ksi shear strength, in single shear... let's say 3/16" dia. in 2024-T3 sheet/plate...

The bolt shear strength is ~ 2690 lbf just based on (pi*r^2)*Fsu. Based on test data, the joint hits shear critical at ~0.140" layer thickness, so that's when the strength tops out at the upper limit of 2690.

Again, from the same test data the min strength is ~670 lbf when the layers get down to 0.036" and the joint is bearing critical (failure by simple P/(d*t)). Backing out that would be based on an Fbru of ~100 ksi which is about right, considering p/dt is a very crude approximation of the actual bearing area.

All sheet thicknesses between 0.036" and 0.140" will be NEITHER shear or bearing critical. This is the transitional strength regime where failure is a complex interaction of shear, bearing, and impingement based on fastener deflection. Calculating an estimated strength based on Fbru*(d*t) might get you fairly close but you stand a good chance of being unconservative because you won't necessarily be predicting the actual bearing area correctly.

There are some "advanced" ways of predicting these transitional joint strength values that might rely on secondary bending models or neutral line methods, etc. But in general, these values need to be determined by joint testing.


Keep em' Flying
//Fight Corrosion!

 

[WKTaylor]

FYI, ONLY...

FTI claims a 'better mouse trap' when it comes to Fasteners in composite holes...

https://fatiguetech.com/products/gromex-composite-liner

...or...

https://fatiguetech.com/products/tukloc-blind-fasteners

Regards, Wil Taylor
o Trust - But Verify!
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", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov