Friction Coefficient when using rivets

[6060842]

Hi,

Is is appropriate to consider the the joint friction coefficient when the joint is held together with rivets?

I use it when talking about bolted connections and would have thought it would not be too dissimilar in riveted connections

While I am on the subject what coefficient would be used if both parts are painted

Regards

Tom

 

[CoryPad]

In general, rivets are hole filling fasteners, so lateral forces induce shear in the fastener. Bolts usually are installed in clearance holes, so the joint members react lateral forces by friction.

For paint-on-paint, the friction coefficient likely is between 0.1 and 0.2.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[csd72]

no pretension in rivets therefore no friction.

 

[Tmoose]

hot riveted joints are sometimes described as applying lots of tension, perhaps up to the yield strength of the rivet. Makes sense to me with all that cooling.

http://www.roymech.co.uk/Useful_Tables/Rivets.html

pop or blind rivets, probably minimal tension. Cherry and Pop don't make any claims I saw.

 

[dimjim]

I think that since theoretically the rivet expands or
fills the hole when they are assembled, you do not need
to consider friction of the plates as the rivets act
as pins.

 

[6060842]

Thanks All,

If friction is not a consideration, then assuming that there are tension and shear forces applied to the joint, then only the shear component needs to be taken into account (Total shear/#Rivets)?

 

[BATman2]

6060842,

Huck fasteners (pin and collar and BOM types) apply significant tension to the assembly. In fact, the tension is designed into the fasteners.

http://www.alcoa.com/fastening_systems/commercial/en/product_category.asp?cat_id=739

Yes, combined loading needs to be considered. Tension will act to separate,compress, or pry the joint regardless of friction. For shear, I would ignore friction.

If you have tension loading on the joint, the type of rivets you use must be capable of carrying the load. Note that the tension load could be acting to "pry" the joint. Be sure to check that when sizing the rivet. Rivet pull out also needs to be checked.

Batman 2

 

[Tmoose]

"If friction is not a consideration, then assuming that there are tension and shear forces applied to the joint, then only the shear component needs to be taken into account (Total shear/#Rivets)?"

OK for first cut.
I'd look at the geometry of the material around the joint.
Sometimes the load sharing is vastly uneven. Even loading is part of the reason for having the load pass thru the centroid. From the design perspective it gets hidden in a bigger safety factor, but as far as the parts are concerned a little local yielding is what really makes it work.