Rivet compression

Not strickly a SW question but it is likely that the expertise is
found in this list...

How would one calculate the diameter and thickness of the shop head of
a rivet?

I want to put together a model of MS20470 type rivets where I can
indicate the thickness of material to be fastened and have the model
generate the shop head automatically. This is important any time you
want to check if the shop head clears any other structures in the
design.

Can I just treat it as an incompressible fluid and simply figure out
that for a given shop head height the diameter would simply be that
which would give me the same solid volume that existed before the
rivet was clinched?

I've already created this by using a design table driven part that
encapsulates the incompressible fluid volume approach within the
underlying math in Excel. A simple form allows input of the desired
clamping thickness and rivet diameter. The design table then selects
the closest rivet length that allows for a head thickness of at least
that in published standards. With this in place, it is a simple
matter to calculate the volume of the portion of the rivet's shaft
that protrudes past the material to be clamped and "squeeze" it based
on the volume formula.

Because there are infinite combinations of shop head diameter and
thickness that result in the same volume I chose to lock the shop head
diameter to match the diameter of the rivet's factory head. With that
locked down the thickness of the shop head is easy math.

Any thoughts?


Thanks,

-Martin

 

Sounds like you have it licked. I used a similar approach for
designing reliefs under coined countersinks in stamped parts.

Re: choosing a diameter--gotta start somewhere. Too many variable
otherwise.

 

Cut rivets to a length in excess of the grip by 1.5 x rivet diameter

Is this practical for commercial (non military/aerospace) production
though? I haven't studied rivetting equipment. Are these tools setup
to make trimming the rivet to length a relatively simple process?

On a slightly different topic. The MS docs spec a #30 hole for a 1/8
in rivet. My fabricator likes to use a #29. The difference isn't
huge, but I am wondering if I should insist that they go with #30.
This is for electronic enclosure for commercial markets. I don't
think it matters for my application.


-Martin

 

Thanks for the help. email on the way.

-Martin