On Tue, 21 Apr 2015 14:02:23 -0500, Tim Wescott
wrote:

On Mon, 20 Apr 2015 07:06:27 -0400, Ed Huntress wrote:

On Sun, 19 Apr 2015 23:04:42 -0500, Ignoramus25660
wrote:

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated whatever is most effective. 3/8" OD and a length of 4'. I
need to know what kind of steel (1144, Stressproff, 4140 TGPHT would
have the least amount of sagging, twisting, and flexing (wasn't sure
on the scientific terms for these). Can you help me out with that
one? Or maybe point me to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?

What Carl said. If you mean what is the physics behind it, no, you'd
have to look that up.

AFAIK the physics behind it is that the Young's modulus is about how the
atoms interact wherever they may be in the crystals, and the ultimate
strength is about how readily the individual crystals (or perhaps planes
within the crystals) can slip -- and carbon atoms tend to "pin" the
crystals (or crystal planes -- see how little I know?) to one another.

Thank you, Tim. That's a *big* help. g

As for strength, yes, you're on the right track. The martensitic
crystal phase creates a pre-strain between the crystals, and that
keeps them from slipping as easily.

But I have no clue about stiffness. It's something going on deeper
than any materials discussion I've read, or that I recall, anyway. I
read a ton of this stuff when I was materials editor at American
Machinist, but that was 34 years ago.

--
Ed Huntress