Pull-Through of Fasteners in Thin Sheet

[GrimesFrank]

I've gotten what seemed a simple request;
What load is required to pull X size fastener through Y thick aluminum cladding?

I went to ever faithful Roark and no direct cook book. The issue is 'thin' sheet, the membrane stresses are substantial so anything I can analytically calculate ignores them, and as such calculates a force much too high.

Does anyone have a reference or direct formula to help me out?

I have a fastener (0.312dia shoulder / 0.187dia shank) through a 0.12 thick 5083-H32 aluminum sheet (S=36.3 ksi). Using Roark I get 905 lb.

If it took that much force to pull 1 nail through aluminum cladding Florida would never have to worry about hurricanes. ;P Please help.

Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel

 

[40818]

What were you using in roark?

You could take the circumference of the bolt head if it round (or inscribed if hex etc). Then you know the material shear allowable. So you have the P/A fastener shear out formula. The bolt head could pop-off if thats the way the joint was designed.

If your bolt head is 0.312" dia, then your shear-out circumference = pi x .312 = 0.98"
the thickness is 0.120" so the area = 0.118in^2
material Fsu = 36300psi so the pull-out force =
36300 x 0.118 = 4283lb

 

[GrimesFrank]

40818,
Failure wouldn't be by shear, do you believe it would take ~2 ton of force to pull an 3/16 screw head through a 1/8 thick aluminum sheet?

Failure would occur when bending stress of the hole is large enough to 'fail the hole' (ie open to slip the head through.

Like I said though, since its a thin sheet, you can't assume the midplane is stress-free, you get membrane stress that I can't figure to account for. My gut says you should be able to pull this thing with about 500 lb, I just can't prove it.

Even experiment data would help if anybody has any. Maybe I could correlate the data, etc. My whole assessment is based on the fact of proving that this will fail at a relatively low load. (~700 LB)

Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel

 

[dvd]

I vote for an experimental determination of the pull-out strength. I can picture running the screws into a piece of the sheet and then inverting the sheet/screw over a hole in a set-up block (screw head down) and determining "push-out" strength on an air-powered arbor press. If you have an air pressure gauge on the regulator you should get a fairly good idea of the forces.

 

[MintJulep]

I wonder if you could treat the problem along the lines of calculating the force required to stamp or draw sheet?

http://nsm

http://www.eng.ohio-state.edu/Sheet_Metal_Lab_Presentation.ppt

 

[csd72]

for self drilling screws have a look in the back of the hilti catalogue.

 

[PackerFan]

This is very close to what you have except it is for steel and the shank is a bit smaller.

 

[GrimesFrank]

MJ,
Thanks but no I don't think this applies. Its an empirical formula to bend the metal and overcome the holding force to draw. What it did though is re-enforce for me that this may be an FEA solution, as crazy as it may sound.

Is there maybe a correction fudge factor of membrane stress based on material thickness that people know about.

Just to clarify;
The fastener is a solid rivet. I think I may cross-reference this in the aeronautics forum.

Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel