What tensile stress unit is "ksi"?

Factual Questions
1

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…

2

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

3

You may have been grasping at straws, but it is kilopounds per square inch.

4

It’s kilopounds. From Wiki:

(For the record, I just googled KSI and the article on pressure was the third result.)

5

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.

6

Wow! I thought my guess was dumb!

Thanks!

7

So did the kilo- prefix predate the metric system?

8

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.)