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Old 11-24-2010, 11:02 AM
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What tensile stress unit is "ksi"?

The stress to make stainless steel bolts gain 1% in length over 10,000 hours at elevated temperatures like 1000 F is given in "ksi". What units are these?

I don't think it can be "kilograms (force) per square inch", because the numbers are typically around 20 and the temperatures are within recommended usage range. A stress of 20 kilograms (force) per square inch is probably what styrofoam could handle, not what stainless steel could handle.

Maybe the numbers are plausible if the "k" stands for "kilopounds", but I'm kinda grasping at straws here....
Old 11-24-2010, 11:05 AM
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ksi = thousands of pounds per square inch

1 ksi = 1,000 psi, 2 ksi = 2,000 psi, etc. 20 ksi is therefore 20,000 psi

k is also referred to as a kip

Last edited by Patch; 11-24-2010 at 11:05 AM.
Old 11-24-2010, 11:05 AM
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You may have been grasping at straws, but it is kilopounds per square inch.
Old 11-24-2010, 11:07 AM
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It's kilopounds. From Wiki:
The ksi ("kilo-pound[-force] per square inch") is 1000 psi, combining the prefix kilo with the psi abbreviation. It is occasionally used in materials science, civil and mechanical engineering to specify stress and Young's modulus.
(For the record, I just googled KSI and the article on pressure was the third result.)

Last edited by MikeS; 11-24-2010 at 11:08 AM.
Old 11-24-2010, 02:58 PM
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Damn, I use units of ksi every freakin' day, so I was hoping I'd be the first to answer this one.

But the others are correct, it's kips (or kilopounds) per square inch.
Old 11-24-2010, 10:32 PM
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Wow! I thought my guess was dumb!

Old 11-28-2010, 06:46 AM
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So did the kilo- prefix predate the metric system?
Old 11-28-2010, 09:37 AM
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I never thought about that before, but the bottom of this page has a list of prefix etymologies. Some of them are modified from their original languages; kilo-, for example, is derived from the Greek chiloi (says Wikipedia.)

Last edited by MikeS; 11-28-2010 at 09:38 AM.
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