On Sat, 22 Nov 2014 10:09:21 -0800 (PST), Sandarpan Mukherjee
wrote:

On Saturday, 22 November 2014 22:12:46 UTC+5:30, Ed Huntress wrote:
On Sat, 22 Nov 2014 07:36:14 -0800 (PST), Sandarpan Mukherjee
wrote:

http://www.amazon.com/XMark-Commerci.../dp/B00JKM3BZU

The bar in the above link claims to have 240000 psi UTS and made out of a chrome-moly steel? Is it possible for such a high strength steel to be non-brittle enough for the application?

"Chrome-moly" usually means AISI 4340 steel or equivalent. 240 kpsi is
about the maximum, and elongation falls off sharply above 200 kpsi. At
225, it's down around 5/%.

Is that enough for your bar? I don't know. Maybe the real-world
application is no problem. At 5%, as a general matter in structural
applications, you begin to expect sudden failures. But maybe it's OK
for such a bar.

--
Ed Huntress

Also as far as I can tell from my decaying memories of Strength of Materials 101, thicker materials are more brittle than the same material when thinner? Especially high carbon steels. Is that correct?

Hmmm. I'm rusty on a lot of this (no pun intended g). "Brittleness"
is not a term that metallurgists ordinarily use. They look at
elongation, and the gap between yield strength and ultimate tensile
strength. Charpy and Izod impact strength are additional terms. In
discussions of tool steels, you'll also see the term "timbre," which
is not well-defined.

What you're looking for, I think, is a determination of what happens
when the yield strength of the bar is exceeded. Does it bend, or does
it quickly reach the ultimate tensile strength, and snap? And if it
bends, how much does it bend before it snaps?

Right? If that's the case, I don't know the answer. I know that 5%
elongation suggests little bending before it snaps. As for thin versus
thick, that's a problem of mechanics: a 5% elongation in tension
allows more bending, in terms of degrees of bend, in a small wire
versus a thicker bar. So a smaller bar should bend more before
breaking than a larger one, all other properties being equal. This is
discussed in terms of the behavior of the "outermost fibers"
(theoretical) of a beam, including a wire or bar. It also explains why
a 300 kpsi piece of music wire will bend quite a lot before breaking.

I think. g Maybe someone who's more up to date on Statics and the
Strength of Materials (that's the title of a good book on the subject)
can chime in and correct me on this.

--
Ed Huntress