In article
,
"Bob's my cat" wrote:

On Mar 31, 9:53 pm, John Doe wrote:
The metal I'm most used to working with is the soft aluminum flat
bar from the local hardware Borg.

Using a 1/8" (thick) x 3/4" (wide) x 3" (long) piece of that soft
aluminum. Make a U shape out of it. If that U shaped piece of
aluminum flat bar is turned upside down and the ends glued to a hard
surface, I know approximately how much weight I could put on it
before it buckled.

Glued? The glue joint will break first, I would think. I'm not sure I
visualize the setup.


What would be the equivalent approximate thickness of 301/304
stainless steel to 1/8" thick soft aluminum flat bar? Any idea will
help.

Thanks.

Assuming that you are working in the elastic range, Steel is roughly 3
times as stiff as aluminum, however, when you start reducing the
thickness, the strength in bending, and stiffness of the bar decreases
rapidly. like with the square of the thickness I think, e.g. bar half
as thick is one quarter as strong, with steel being about 3 times as
stiff, 1/16" SS will still not be as stiff as the 1/8 Al. so
somewhere between 1/16 and 1/8.

By "strength" it sounds like you are talking about rigidity (stiffness),
which varies as the cube (not the square) of the thickness in the
dimension being bent, and linearly with the modulus of elasticity of the
material.

The modulus of elasticity of steel is about three times that of aluminum
alloys, and probably four times that of borg extrusions.


On the other hand if you are talking about the yield point, not
elastic deflection, then it gets trickier, 301 can be work hardened to
a much higher yield strength than your hardware store aluminum, but
you'd have to know how hard it is, still, I'm not sure it is going to
have much more than three times the yield strength. maybe 4x but I'm
not sure. so the thickness guess above still applies.
Also steel is about three times as dense, and while plain low carbon
steel is much cheaper (by weight) than Al. I don't know that SS is, so
your SS part, while slightly thinner will be heavier and probably more
expensive.

Borg metal will be far softer than say 6061 alloy.


I don't know that I would worry about elasticity before I figured out
the load capacity of the glued joint. From the above description, it
sounds like the ends are making epoxy butt joints to perpendicular flat
plates. Even if the metal is strong enough, the bays will deflect,
prying at the glue joints. The leverage is quite large, far exceeding
the strength of any available epoxy.

What is meant by "buckle"? Deflect visibly, or completely collapse,
dropping the load onto the floor? What is the application here?

Joe Gwinn