>>> Trevor Boicey <tboicey@brit.ca> 08/24 5:43 PM >>>
> I would VERY much disagree that rivets are stronger than welding. In
>fact, stronger than welding is not really a possible goal, because
>a proper weld seam is as strong as if the seam never existed, so if
>the seam is stronger than the surrounding metal, then you'll just
>tear the surrounding metal.
It's very simple matter to make a joint or seam stronger then the metal around
it by simply reinforcing it. Lapped
joints are a good example of this. And as you've pointed out, a strong seam
holds while the metal around it
fails. This is not necessarily a flaw.
The metal in and around a weld is inherently changed by the heating and melting
action of welding, as well
as the addition of the filler metal itself, if used. You can never achieve
identical properties, though you can
come relatively close in some cases.
Welded joints will fail at the interface of the weld seam and the panel. It's
inherent with welding, and must be
compensated for. The weld itself is often stronger then the base metal welded
due to increased thickness
and the filler material. This creates an abrupt change in the way strain is
distributed throughout the member
that was welded. Ie, it creates a hard spot. Welding also encourages stress
fracturing due to the erosion of the base metal at the edge of the puddle.
Even proper welds leave minute edges of erosion along the weld
seam. This does not need to be large to create the problem! This is inherent
with welding, having to
do with the wave action in the puddle.
Proper Riveting allows for better distribution of strain in the joined pieces.
There is not inherently an edge
like there is with a weld seam. The base metal is also not damaged the way it
is with welding by both
metalurgical changes and surface edges (erosion) that cause fractures.
Remember, I'm talking about
proper riveting, not just whacking some cheap pop rivets in place.
> However, more important than all of this, you can't use aluminum
>rivets in a steel body. The dissimilar metals will cause very
>rapid corrosion. Even if the corrosion isn't a visual or structural
>problem, the metal will rust away and the rivet will quickly
>become loose in it's hole.
Aluminum and steel can co-exist peacefully. Aluminum heads, held down by steel
fasteners, onto iron
engine blocks is a ready enough example. Of the two metals, aluminum is the
more reactive and is
the one that will corrode first, not steel. If the joints are properly
prepared and sealed, the water which is
vital for corrosion is excluded from the equation, and the joint will not be
damaged.
Cheap steel pop rivets are available at hardware stores.
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