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# Margin of safety for separation, NASA-STD-5020

## Margin of safety for separation, NASA-STD-5020

(OP)
Hi,
I am trying to figure out the margin of safety for joint separation that I can allow in my structure.
The structure is a school-book example of a bolt connecting two flanges.

The standard (page 38, equation 6-23):

So far I've determined my minumum preload, FF (1.15) and FSsep (1.2).

What does PtL (limit tensile load) mean exactly? How is it calculated?

S

### RE: Margin of safety for separation, NASA-STD-5020

I only got 1/2 way through your attmt, but surprised I could see no discussion about prying loads; possibly assuming that if the joint faces are clamped then no moment, though it's better to show this with sums. This is important if you've got a typical tension fitting where the single bolt is offset from the far field loadpath (draw a FBD).

### RE: Margin of safety for separation, NASA-STD-5020

(OP)
What you write seems likely. Still, I would like to know how close I can be to contact separation and say fulfils the acceptance criteria.

Right not I'm leaning toward just using another general load factor.

The NASA way would be preferable since I believe that the load factor 1.5 is too conservative.

### RE: Margin of safety for separation, NASA-STD-5020

PL is the limit applied load ... the applied load from limit loadcases. They'd use ultimate load to size the joint, that is the 1.5 factor (ultimate FoS).

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