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Letter 11042
Yield strength of metals
I need to weld a plate in a "T" shape, one piece is 6"x8" the
other is 6"x6" this plate is welded to the 6x8 piece. I need to know
how thick the material should be wether it is stainless steel or mild
steel or hardened steel to have a yield strength of 55,000 psi. Also
could you give me a formula to use to figure it out, thank you.
The 6x8 would be mounted to a surface with 2 anchors the 6x6 is
mounted on center with a 2" hole on center, the force would be up and
out.
THANKS AGAIN.
John G

- Ramsey, MN, USA
John:
Your terminology is wrong. 'psi' is a measure of the stress on, or
strength of, a material per unit area.Are you trying to say that the
load on this weldment is 55,000 lbs. tension? Engineers ALWAYS apply
a 'factor of safety' as well, they never design to the yield strength
of a material.This weldment will likely fail at the welds rather than
within a member anyway, and designing tension welds is a very tricky
business indeed. In fact, it is prohibited to design many structures
(like cranes) with tension welds. There are other factors to consider
like L/r ratio as well. Call in a local engineer: it is illegal to do
engineering without a license, and for an engineer to try to do it by
'remote control' over the internet would be just as bad and probably
just as illegal :-)
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Ted Mooney, P.E.
finishing.com
Brick, New Jersey
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I'm designing a rectangle frame made from 1/4" x 2" angle iron.
The dimension of the frame is 34"w x 30"l and the angle iron joints
meet at a 45 deg angle and they have a 1/4 weld joint on each side. I
have 4 - 1" x .045" square tubing that will set inside the frame and
will welded to the frame equally spaced out. A 3/4" piece of plywood
sits on top that acts as a base. How much weight can this hold?
Thanks,
HARRY S

- Spring, TX, US of A
I realize that skilled mechanics sometimes just piece things
together non critical weldments based on experience and judgement,
Harry, and I'd be wasting my breath trying to condemn something that
is so widely practiced. But you simply can't proceed to engineer a
load-carrying device via internet advice. It's no different than
asking for internet advice on how long to make the incision for an
appendectomy. An engineer or architect spends 2 years in engineering
school just in "analyzing the forces" before he can take his first
beginning course in structures or design of machine elements. Even in
a simple device there are many potential modes of mechanical failure,
just as there are many ways the patient can die during or because of
an operation :-)
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Ted Mooney
finishing.com
Brick, New Jersey |
Dear Reader, please --
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question on a different subject.
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- Answer or follow-up on this subject (in non-commercial
fashion).
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