Strength..

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mivey

Senior Member
I have a UBS of 336.9 lbs for hard drawn #12 copper.

add:
261.6 lbs for medium hard drawn
197.5 lbs for soft or annealed
 
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Ponchik

Senior Member
Location
CA
Occupation
Electronologist
according to this site www.southwire.com

0.008 lbs per cmil
so, a 12awg copper has 6530 cmil
6530 x .008 = 52.24 lbs

but is way different than what MIVEY has.

Mivey,
what is UBS?
 

mivey

Senior Member
according to this site www.southwire.com

0.008 lbs per cmil
so, a 12awg copper has 6530 cmil
6530 x .008 = 52.24 lbs

but is way different than what MIVEY has.

Mivey,
what is UBS?
Ultimate Breaking Strength. It is what we use to determing maximum pulling tensions. Maybe I misunderstood what the OP was after.
 

Ponchik

Senior Member
Location
CA
Occupation
Electronologist
Mivey,
I like to know where you got the UBS info? Thanks
this is good info.
 

mivey

Senior Member
Mivey,
I like to know where you got the UBS info? Thanks
this is good info.
From my pulling calculator. Not that the allowable pulling tension is lower than the UBS (we use 60% for the smaller wire).

add: There is a table in the American Electrican's Handbook.
 
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mivey

Senior Member
according to this site www.southwire.com

0.008 lbs per cmil
so, a 12awg copper has 6530 cmil
6530 x .008 = 52.24 lbs

but is way different than what MIVEY has.

Mivey,
what is UBS?
My values were the breaking strength. The values in the southwire bulletin:
http://www.southwire.com/documents/SIMpullTHHNInstallationandApplicationGuide8-15-07.pdf

are the allowable pulling tensions for their insulated wire (well below the breaking strength). We use about 60% of the UBS when pulling small bare wire.

At any rate, the OP did not say he was after maximum allowable pulling tension.

Add: I will note that Southwire states the tensile strength of the copper used for conductor is 62,000 psi
 
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Ponchik

Senior Member
Location
CA
Occupation
Electronologist
MIVEY,
Thanks for your info.
I am still trying to understand the difference between the two:

I will read through my American Electricians' handbook.
 

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
MIVEY,
Thanks for your info.
I am still trying to understand the difference between the two:

I will read through my American Electricians' handbook.

IMHO, UBS or ultimate breaking strength, is the point in which the cooper will snap or break. Ultimate pulling tension would probably be the calculated force one can safely exert on a conductor without deformation or elongation of the conductor, insulation or both.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110526-1327 EDT

From my Engineering Materials book by White --- "the terms elastic limit, proportional limit, and yield strength will be considered to be practically synonymous". These refer to a stress level beyond which the material will not return to its original unstressed length.

Tensile strength is the peak stress that the material can support. When this is exceeded the material progresses toward rupture.

Once you pass the elastic limit and go toward the tensile strength limit there is no return to the original length. The diameter of the wire is smaller and it is harder from the work hardening that took place.

See http://www.hcrosscompany.com/metals/copper.htm
for data on pure copper, and some alloys.

So for pure annealed copper the elastic limit is 10,000 PSI and the tensile strength (ultimate strength) is 35,000 PSI. Work hardened these values are higher at 53,000 and 57,000 PSI.

For #12 copper annealed the area is 0.005129 sq-in. Thus, elastic limit is 51.29 #, and tensile strength is 179.5 #. Normally the wire you work with is cold drawn and therefore work hardened. So the corresponding values will be towards 271.8 # and 292.4 #.

By alloying other materials with the copper the strength can be increased, but conductivity decreases. Thus, you should use the wire manufacturer's values for your calculations.

.
 
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