Stiffness of round bar
Existential Angst
A 1" solid round HR bar is supported at it's ends 7 feet apart. The loads
are such that there is noticeable but not dangerous sag. Still, I'd like to
reduce the sag, without increasing the bar diameter, due to other
constraints.
What alloys, tempering, etc would increase stiffness, and by how much? At
what cost, rel. to hot rolled?
I seem to notice a much increased stiffness of tempered/alloyed alum over
plain old 6061 alum, and am hoping to see the same thing in steel.
--
EA
Paul K. Dickman
one another that it will not make any difference.
It is governed by steel's modulus of elasticity, it's cross section and the
load
You can't change the first.
You have to increase the diameter or decrease the weight.
Use pipe
Paul K. Dickman
"Existential Angst" <UNfi...@UNoptonline.net> wrote in message
news:4b8594a0$0$22533$607e...@cv.net...
Ed Huntress
"Existential Angst" <UNfi...@UNoptonline.net> wrote in message
news:4b8594a0$0$22533$607e...@cv.net...
You won't. Heat treatment and alloy have almost no effect on stiffness. To
get anything stiffer, you have to go to tungsten or tungsten carbide, or
some equally expensive exotic.
--
Ed Huntress
F. George McDuffee
<pkdi...@ameritech.net> wrote:
>The stiffness of all steels (regardless of heat treatment) are so close to
>one another that it will not make any difference.
>
>It is governed by steel's modulus of elasticity, it's cross section and the
>load
>
>You can't change the first.
>
>You have to increase the diameter or decrease the weight.
>Use pipe
===========
This appears to exactly correct.
One thing that you can do to improve stiffness is pre stress the
tube or pipe by placing a threaded rod inside it and using this
to compress the tube. The more compression stress you can apply
without collapsing the tube the stiffer the tube will be.
Unka George (George McDuffee)
..............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).
Ned Simmons
<gmcd...@mcduffee-associates.us> wrote:
>
>One thing that you can do to improve stiffness is pre stress the
>tube or pipe by placing a threaded rod inside it and using this
>to compress the tube. The more compression stress you can apply
>without collapsing the tube the stiffer the tube will be.
As long as you're working within the elastic limit of the materials,
prestressing won't help; superposition applies.
--
Ned Simmons
Jim Wilkins
wrote:
> Awl --
>
> A 1" solid round HR bar is supported at it's ends 7 feet apart. The loads
> are such that there is noticeable but not dangerous sag. Still, I'd like to
> reduce the sag, without increasing the bar diameter, due to other
> constraints.
> --
> EA
If you can keep it from twisting, bend it upward enough that it
settles straight.
jsw
Tim Wescott
If it's a concrete pipe, then stressing it in compression will certainly
strengthen it against the stretch from bending, but I don't know if
it'll _stiffen_ it.
Not that Proctologically Anxious, or Existentially Violated, or whatever
his name is today, is using a 1" diameter, 7' long concrete tube.
--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
Tim Wescott
compared to its weight...
Wes
>If you can keep it from twisting, bend it upward enough that it
>settles straight.
Which explains those flat bed trailers that have an arch built in.
Wes
Ed Huntress
"Tim Wescott" <t...@seemywebsite.now> wrote in message
news:iN-dnRnDtcviIxjW...@web-ster.com...
It's a tricky question, because it varies from 8 to over 300 GPa. Steel is
200 GPa.
It depends primarily on the measurement relative to fiber direction, but
also to fiber percentage and type of fiber. There are high-modulus fibers
that are brittle, and low-modulus ones that you can tie into a knot.
Typical values for high-performance automotive-type (racecar) epoxy layups,
multi-directional (fibers arranged in multiple axes) is around 100 - 180
GPa. But that's per unit volume. Per unit weight, it's *much* stiffer than
steel. Plain, individual fibers can run well over 300 GPa.
BTW, regarding your comment about concrete, its modulus in compression is
only around 30 GPa. The modulus in tension is almost irrelevant, because the
strength is so low. But pre-tensioned concrete is never in tension. You're
either adding to the compression load, or reducing it.
--
Ed Huntress
Richard J Kinch
> A 1" solid round HR bar is supported at it's ends 7 feet apart.
Drapery hanging project? Too cheap for a Walmart traverse rod?
Ned Simmons
wrote:
>Ned Simmons wrote:
>> On Wed, 24 Feb 2010 16:48:49 -0600, F. George McDuffee
>> <gmcd...@mcduffee-associates.us> wrote:
>>
>>
>>> One thing that you can do to improve stiffness is pre stress the
>>> tube or pipe by placing a threaded rod inside it and using this
>>> to compress the tube. The more compression stress you can apply
>>> without collapsing the tube the stiffer the tube will be.
>>
>> As long as you're working within the elastic limit of the materials,
>> prestressing won't help; superposition applies.
>>
>If it's an isotropic material, like steel.
>
>If it's a concrete pipe, then stressing it in compression will certainly
>strengthen it against the stretch from bending, but I don't know if
>it'll _stiffen_ it.
Prestressing won't stiffen a concrete tube either.
--
Ned Simmons
Tim Wescott
> On Wed, 24 Feb 2010 16:02:45 -0800, Tim Wescott <t...@seemywebsite.now>
> wrote:
>
>> Ned Simmons wrote:
>>> On Wed, 24 Feb 2010 16:48:49 -0600, F. George McDuffee
>>> <gmcd...@mcduffee-associates.us> wrote:
>>>
>>>
>>>> One thing that you can do to improve stiffness is pre stress the
>>>> tube or pipe by placing a threaded rod inside it and using this
>>>> to compress the tube. The more compression stress you can apply
>>>> without collapsing the tube the stiffer the tube will be.
>>> As long as you're working within the elastic limit of the materials,
>>> prestressing won't help; superposition applies.
>>>
>> If it's an isotropic material, like steel.
>>
>> If it's a concrete pipe, then stressing it in compression will certainly
>> strengthen it against the stretch from bending, but I don't know if
>> it'll _stiffen_ it.
>
> Prestressing won't stiffen a concrete tube either.
>
under prestress -- that I can think of at least -- would be something
like caltrops in jelly, or a big stack of washers.
Existential Angst
news:Xns9D29CEB97F2...@216.196.97.131...
> Existential Angst writes:
>
>> A 1" solid round HR bar is supported at it's ends 7 feet apart.
>
> Drapery hanging project? Too cheap for a Walmart traverse rod?
Dude, it would have to be some hellified drapes to require 1" solid bar,
donchathink??
It's ackshooly for gym-type stuff: chinups, equipment/heavy-bag hanging,
etc.
--
EA
Existential Angst
news:g0lbo59l9irtf7f28...@4ax.com...
Have you noticed how much stiffer some aluminum is than other? Even within,
say, the 6061 class?
It seems that plate is much harder/stiffer than bar. Even in my limited
experience, if you give me two different pieces of say 6x6" x 1/4 cut from
plate and bar, I can immediately tell the diff -- the plate almost has a
ring to it.
And seems WAY stiffer.
Is this my imagination, or do you see the same thing? If this is in fact
true, why such a diff in aluminums, and not amongst steels?
Also, the 1" bars I use in weight lifting *seem* much stiffer than the 1"
HR stuff. More imagination?
--
EA
>
> --
> Ned Simmons
Ed Huntress
"Existential Angst" <UNfi...@UNoptonline.net> wrote in message
It's your imagination. Like steel alloys, aluminum alloy stiffness falls
into a narrow range, although it's a bit wider than that for steel -- around
62 - 75 GPa. It doesn't depend on a particular alloy's hardness, either.
> If this is in fact true, why such a diff in aluminums, and not amongst
> steels?
>
> Also, the 1" bars I use in weight lifting *seem* much stiffer than the 1"
> HR stuff. More imagination?
Yup. Until they take a permanent bend, the stiffnesses of various steels
(around 200 GPa) and aluminums (62 - 75 GPa) are very close.
Higher strength can give the allusion of greater stiffness. The actual
stiffness (Young's modulus) is roughly the same for 1100 grade aluminum and
for 6061, but bending a bar of each, the weaker 1100 reaches its elastic
limit much sooner. So you never get to feel as much "spring" in it as you do
with a same-size bar of 6061. This can feel like greater stiffness. But if
you clamped the end of a bar of each in a vise, and hung a weight from the
other end of each, you'd see that equal weights cause an equal amount of
bend -- until the weaker one takes a permanent bend.
Aluminum-beryllium alloys are much stiffer, however, as are aluminum
composites.
--
Ed Huntress
Ed Huntress
"Ed Huntress" <hunt...@optonline.net> wrote in message
news:4b8620eb$0$31274$607e...@cv.net...
>
> Higher strength can give the allusion....
GAK! Allusion should be illusion.
--
Ed Huntress
Existential Angst
Heh, DAT proly woke you up, eh?
You proly won't be able to get back to sleep for like 4 more hours!! :)
And yeah, mebbe it is that better "spring" that makes stuff feel like
harder, stiffer material.
Inneresting....
--
EA
>
> --
> Ed Huntress
>
Existential Angst
Heh, those are good, too, and not at all inaccurate.
Altho, in all etiological strictness, proctological violation is much more
conducive to existential angst than vice versa.
Sheeit, at my most Violated, forget about existential angst, yo, I dint have
any nails left!!
Truth be told, my proctological violations have abated not at all.... It's
just that I observe a very large demographic that is *at least* as PV'd as
I am (and far more MindFucked), so I don't feel so conspicuous, so
singled-out.
I still writhe/complain harder and louder than most about being incessantly
PV'd, but I may pipe down soon.
If my BAQ (broke-assed quotient) diminishes at all, and I'm able to afford
campaign contributions to my local congressman and thusly earn the privilege
of blowing him in private, sheeit, I'll be one very happy hypocritical and
quiet camper.
BYOKP.
yeah, knee pads.....
--
EA
Dave__67
wrote:
> "Richard J Kinch" <ki...@truetex.com> wrote in messagenews:Xns9D29CEB97F2...@216.196.97.131...
>
> > Existential Angst writes:
>
> >> A 1" solid round HR bar is supported at it's ends 7 feet apart.
>
> > Drapery hanging project? Too cheap for a Walmart traverse rod?
>
> Dude, it would have to be some hellified drapes to require 1" solid bar,
> donchathink??
>
> It's ackshooly for gym-type stuff: chinups, equipment/heavy-bag hanging,
> etc.
> --
> EA
Where no one needs to grab it, weld some of the same size bar
lengthwise under the main bar- something draped over it will still
slide past that spot.
Dave
Joe AutoDrill
Grind some flats on the end of the bar. Fasten it securiy in place AFTER
slightly bending it in an arc to match the arc you get now when it is under
load. It should just about be level under load after doing that presuming
you can properly manage it's desire to twist with those flats, etc.
--
Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com
Production Tapping: http://Production-Tapping-Equipment.com/
Flagship Site: http://www.Drill-N-Tap.com
VIDEOS: http://www.youtube.com/user/AutoDrill
V8013-R
Don Foreman
<hunt...@optonline.net> wrote:
> But pre-tensioned concrete is never in tension.
What could be clearer than that? <G>
>You're either adding to the compression load, or reducing it.
If you only pretend to do that is that pretension compression?
Ed Huntress
"Don Foreman" <dfor...@NOSPAMgoldengate.net> wrote in message
news:14ktq5h3brsh0s5pf...@4ax.com...
> On Wed, 24 Feb 2010 19:45:18 -0500, "Ed Huntress"
> <hunt...@optonline.net> wrote:
>
>> But pre-tensioned concrete is never in tension.
> What could be clearer than that? <G>
Cleaning out the "drafts" folder, Don? <g>
<sigh> That was a failed exercise in explaining. I also meant
post-tensioned, not pre-tensioned, but it doesn't matter. It applies to any
kind of tensioning.
The concrete itself it never in tension. The tension members in
post-tensioned concrete are separate from the concrete itself. Is that
better?
>
>>You're either adding to the compression load, or reducing it.
> If you only pretend to do that is that pretension compression?
Wise guy. d8-)
--
Ed Huntress
Wes
>It seems that plate is much harder/stiffer than bar. Even in my limited
>experience, if you give me two different pieces of say 6x6" x 1/4 cut from
>plate and bar, I can immediately tell the diff -- the plate almost has a
>ring to it.
>
>And seems WAY stiffer.
>
>Is this my imagination, or do you see the same thing? If this is in fact
>true, why such a diff in aluminums, and not amongst steels?
>
>Also, the 1" bars I use in weight lifting *seem* much stiffer than the 1"
>HR stuff. More imagination?
Imagination. Years ago, I as making a machine to take an SRIM dispensing head into a
press. The head was pretty darn heavy and the beam was fairly long.
My little brain knew that droop was going to be an issue. Glory be, machinist handbook
has the formulas to calculate that for regular sections.
Now not trusting my interpretation of the material presented, I performed the calculations
for various items in our stock rack and damn, when I clamped the stock to a heavy support
to check, the calculations proved out.
I ended up with a rectangular tube that was made out of two pieces of aluminum L section
angle together by my brother in law to get what I wanted based on the calculations.
Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller