> Anyone that owns a "Machinery's Handbook" has the needed data. It is
> also available from pipe and tubing manubactures.
> The "Machinery' Handbook" is a very common industrial bible.
>
> Would you mind looking them up and letting us know? My Central
> Steel materials handbook doesn't list anything for pipe yield strengths
> in its 272 pages. Lots of data on SAE grade tubing but nothing for
> pipe. Tnx.
The questions about the strength of water pipe came up while I was on
vacation. I think I can help a little with this one.
The yield strength of a material is the stress, expressed in pounds per
square inch (psi), at which a material begins to deform permanently,
resulting in some sort of lasting change of shape after the stress is
removed.
The ultimate strength, usually somewhat higher, is that where the
material has already yielded, and stetched or bent, and finally breaks.
You generally want to design things to stay below 50-67% of the yield
strength of the material (safety factor between 1.5 to 2). The translation
of the stress level to the actual allowable loads on the part in question,
and vice-versa, is the tricky part that requires an analysis of the
geometry and math. Those calculation can get hairy!
The strength of metals varies greatly with the method of their manufacture
and composition.
1) Quenching, cooling very rapidly from a glowing hot temperature, can
dramatically increase the hardness, but introduces brittleness.
2) Tempering, reheating to a lower temperature followed by a slow cooling,
'draws' the hardness back down, reducing the brittleness and adding some
toughness.
3) Annealing, heating to a high (glowing) temperature and allowing to cool
slowly, softens a metal, reducing hardness and adding considerable
ductility (ability to be bent and formed).
4) Cold working, when parts are bent, mashed, drawn, hammered (wrought),
flattened, etc, by machine or by hand, causes the hardness and strength to
go up somewhat.
5) Repetetive bending causes fatigue and drastic strength loss. This, in
turn, can further cause your wallet and credibility to vaporize if you
have not accounted for it!
Different metals, and alloys of the same metal respond very differently to
these treatments. It gets complicated!
It depends on the alloy *and* the treatment.
The point to remember is that identifying the type of metal is *far*
different from knowing its actual strength. The advice of not using a pipe
or tube of unknown origin for a mast is good because even though you may
know that it is steel or aluminum, you still don't know it's properties
unless you bought it from a manufacturer or reseller or have it tested.
Of course, you can always count on minimum strength values for types of
metals, with the knowledge that it may still be much stronger.
Hardness has an excellent correlation with the strength of the metal.
The harder it is to prick with a center punch, the higher its yield
strength.
Again, It depends on the alloy *and* the treatment.
It just so happens that I keep a copy of Machinery's Handbook on my desk
for reference, so without any further ado, some data:
SOME REPRESENTATIVE YIELD STRENGTHS
Aluminum, 6061-O (fully annealed) - 8,000 (surprise!)
Copper, annealed (soft) - 10,000 psi
Brass, cast - 12-15,000
Aluminum, 6061-T4 - 24,000 (surprise!)
Wrought iron - 23,000 to 32,000 psi
Wrought Steel (water pipe) - 23,000-32,000
Steel, common structural (I-beams, etc) - at least 33,000
Aluminum, 6061-T6 - 40,000 (surprise! - it's the treatment)
Copper, wrought, up to 53,000 (what the book says!)
Brass, wrought - up to 62,000 (what the book says)
Steel, 1025 low carbon (cheap fasteners) - 50,000
Steel, 1050, quenched and tempered "typical" - 95,000
Tool steel, 4140, quenched, tempered to 1200F - 95,000 (tough)
Tool steel, 4140, quenched, tempered to 400F - 238,000 (!) (brittle)
Ok, you see that the alloy and the treatment affect the properties.
Be very careful to know what the alloy is and what the heat treatment is.
The little "T6" behind the 6061 aluminum is easy to overlook but is SOOOO
important.
By the way, 6061-T6 is one of the most common structural aluminums.
4140 is but one of many, many tool steel alloys.
SIZE DATA FOR WATER PIPE (INCHES) (count on about 20,000 psi yield)
SIZE, SCHEDULE, ID, OD, WALL THK
1.25, 40, 1.380, 1.660, .140
1.25, 80, 1.278, 1.660, .191
1.50, 40, 1.610, 1.900, .145
1.50, 80, 1.500, 1.900, .200
2.00, 40, 2.067, 2.375, .154
2.00, 80, 1.939, 2.375, .218
I don't know if the MARC program accepts input of yield strength
information for materials and independent sizes in the calculation of mast
strengths, but this data along with the size data will tell you
*approximately* what a mast will take, provided you *know the alloy and
the treatment*
If in doubt, go and buy something of known properties.
Hope I helped someone half as much as this reflector has helped me!
- - ... MARK_N1LO...- -
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