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| Michel PIETTE |
 Posted: Fri Jan 21, 2005 12:56 am |
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Guest
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Good morning,
Our laboratory makes tensile testing on steels. We often observe Young's
Modulus (initial slope of the tensile curve) very different of the expected
value of 207 GPa (we observe 140 GPa to 230 GPa) on Carbon Steel materials
in different metallurgical states (Q, QT, N, ...).
This seems to occur since years (I have asked former workers), independently
of tensile testing machines, operator, sample geometry.
We have also asked INSTRON, the supplier of our testing machine, and they
have no ideas.
To live with the problem, it was decided to make an hysteresis loop after 2%
deformation and use that slope as Young's modulus. The value so obtained is
only slightly less dispersed, but a recent experiment with multiple
hysteresis loops (after 1% 2%, 3%, ...) shows that doing so, the Young's
Modulus seems to decrease with the deformation performed before the
hysteresis.
Do you have any ideas or references about :
- why the initial slope and the hysteresis slope differ so much from 207 GPa
- why Young's Modulus seems to decrease as the inital deformation increases.
I have done search on the Web with google and Copernic, but got no helpful
answer.
Thank you very much for your help,
Michel |
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| Michael Dahms |
| Posted: Fri Jan 21, 2005 6:15 am |
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Guest
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Michel PIETTE wrote:
[quote:ac2a7cfae7]
Our laboratory makes tensile testing on steels. We often observe Young's
Modulus (initial slope of the tensile curve) very different of the expected
value of 207 GPa (we observe 140 GPa to 230 GPa) on Carbon Steel materials
in different metallurgical states (Q, QT, N, ...).
[/quote:ac2a7cfae7]
Young's modulus of polycrystalline materials depends on crystallographic
texture. 207 GPa is just a typical value for bcc iron.
Michael Dahms
f'up2 sci.materials |
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| Guest |
| Posted: Fri Jan 21, 2005 3:21 pm |
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Michael Dahms wrote:
[quote:948e9d9925]Michel PIETTE wrote:
Our laboratory makes tensile testing on steels. We often observe
Young's
Modulus (initial slope of the tensile curve) very different of the
expected
value of 207 GPa (we observe 140 GPa to 230 GPa) on Carbon Steel
materials
in different metallurgical states (Q, QT, N, ...).
Young's modulus of polycrystalline materials depends on
crystallographic
texture. 207 GPa is just a typical value for bcc iron.
Can the anisotropy of steel's young's modulus really be as high as a[/quote:948e9d9925]
factor of two? I'm looking on the web for a numeric range but haven't
found one yet.
Michael, When you say initial slope what exactly do you mean? You are
not looking at the very short low-slope portion that may be because of
minor alignment problems are you? I've interpreted your question to
refer to the slope of the stress strain line essentially to the yield
condition.
Dave |
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| jbuch |
| Posted: Fri Jan 21, 2005 8:41 pm |
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Guest
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Michel PIETTE wrote:
[quote:29545ad6f8]Good morning,
Our laboratory makes tensile testing on steels. We often observe Young's
Modulus (initial slope of the tensile curve) very different of the expected
value of 207 GPa (we observe 140 GPa to 230 GPa) on Carbon Steel materials
in different metallurgical states (Q, QT, N, ...).
This seems to occur since years (I have asked former workers), independently
of tensile testing machines, operator, sample geometry.
We have also asked INSTRON, the supplier of our testing machine, and they
have no ideas.
To live with the problem, it was decided to make an hysteresis loop after 2%
deformation and use that slope as Young's modulus. The value so obtained is
only slightly less dispersed, but a recent experiment with multiple
hysteresis loops (after 1% 2%, 3%, ...) shows that doing so, the Young's
Modulus seems to decrease with the deformation performed before the
hysteresis.
Do you have any ideas or references about :
- why the initial slope and the hysteresis slope differ so much from 207 GPa
- why Young's Modulus seems to decrease as the inital deformation increases.
I have done search on the Web with google and Copernic, but got no helpful
answer.
Thank you very much for your help,
Michel
[/quote:29545ad6f8]
If you go here and look at the slide near the very end.... titled
anisotropy....
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.
you will find listed the claim that the elastic modulus for Iron in the
face edge 100 directions is about 135 Gpa and the modulus for Iron in
the cell diagonal 111 direction is about 273 Gpa.
Very nice presentation.
--
................................
Keepsake gift for young girls.
Unique and personal one-of-a-kind.
Builds strong minds 12 ways.
Guaranteed satisfaction
- courteous money back
- keep bonus gifts
http://www.alicebook.com |
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| Guest |
| Posted: Fri Jan 21, 2005 10:22 pm |
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jbuch wrote:
[quote:25b70aee14]Michel PIETTE wrote:
Good morning,
If you go here and look at the slide near the very end.... titled
anisotropy....
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.
you will find listed the claim that the elastic modulus for Iron in
the
face edge 100 directions is about 135 Gpa and the modulus for Iron in
the cell diagonal 111 direction is about 273 Gpa.
Very nice presentation.
[/quote:25b70aee14]
Thanks Jim, it is just what I was looking for unfortunately he link is
broken. |
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| jbuch |
| Posted: Sat Jan 22, 2005 12:25 am |
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dmartin@newarts.com wrote:
[quote:9c3efe5177]jbuch wrote:
Michel PIETTE wrote:
Good morning,
If you go here and look at the slide near the very end.... titled
anisotropy....
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.
you will find listed the claim that the elastic modulus for Iron in
the
face edge 100 directions is about 135 Gpa and the modulus for Iron in
the cell diagonal 111 direction is about 273 Gpa.
Very nice presentation.
Thanks Jim, it is just what I was looking for unfortunately he link is
broken.
[/quote:9c3efe5177]
Email the author......
mmyliu@polyu.edu.hk
Ask if he will give you the link to his excellent materials notes. |
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| Gerben Sinnema |
| Posted: Sat Jan 22, 2005 11:19 am |
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Guest
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the link is:
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.pdf
"jbuch" <jbuch@CUTHERErevealed.net> wrote in message
news:csso0c01a2v@enews3.newsguy.com...
[quote:ab144c955a]dmartin@newarts.com wrote:
jbuch wrote:
Michel PIETTE wrote:
Good morning,
If you go here and look at the slide near the very end.... titled
anisotropy....
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.
you will find listed the claim that the elastic modulus for Iron in
the
face edge 100 directions is about 135 Gpa and the modulus for Iron in
the cell diagonal 111 direction is about 273 Gpa.
Very nice presentation.
Thanks Jim, it is just what I was looking for unfortunately he link is
broken.
Email the author......
mmyliu@polyu.edu.hk
Ask if he will give you the link to his excellent materials notes.
[/quote:ab144c955a] |
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| Michel PIETTE |
| Posted: Sat Jan 22, 2005 1:17 pm |
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Guest
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I fully agree that E depends on orientation.
Nevertheless, our steels are mainly Quenched and Tempered types, and I don't
expect them to be textured.
But maybe I'm wrong... What's your opinion ?
Michel
"jbuch" <jbuch@CUTHERErevealed.net> a écrit dans le message de news:
cssasq022s8@enews4.newsguy.com...
[quote:2b4f029bd5]Michel PIETTE wrote:
Good morning,
Our laboratory makes tensile testing on steels. We often observe Young's
Modulus (initial slope of the tensile curve) very different of the
expected value of 207 GPa (we observe 140 GPa to 230 GPa) on Carbon Steel
materials in different metallurgical states (Q, QT, N, ...).
This seems to occur since years (I have asked former workers),
independently of tensile testing machines, operator, sample geometry.
We have also asked INSTRON, the supplier of our testing machine, and they
have no ideas.
To live with the problem, it was decided to make an hysteresis loop after
2% deformation and use that slope as Young's modulus. The value so
obtained is only slightly less dispersed, but a recent experiment with
multiple hysteresis loops (after 1% 2%, 3%, ...) shows that doing so, the
Young's Modulus seems to decrease with the deformation performed before
the hysteresis.
Do you have any ideas or references about :
- why the initial slope and the hysteresis slope differ so much from 207
GPa
- why Young's Modulus seems to decrease as the inital deformation
increases.
I have done search on the Web with google and Copernic, but got no
helpful answer.
Thank you very much for your help,
Michel
If you go here and look at the slide near the very end.... titled
anisotropy....
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.
you will find listed the claim that the elastic modulus for Iron in the
face edge 100 directions is about 135 Gpa and the modulus for Iron in the
cell diagonal 111 direction is about 273 Gpa.
Very nice presentation.
--
...............................
Keepsake gift for young girls.
Unique and personal one-of-a-kind.
Builds strong minds 12 ways.
Guaranteed satisfaction
- courteous money back
- keep bonus gifts
http://www.alicebook.com
[/quote:2b4f029bd5] |
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| jbuch |
| Posted: Sat Jan 22, 2005 6:33 pm |
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Michel PIETTE wrote:
[quote:03bd9fb73a]I fully agree that E depends on orientation.
Nevertheless, our steels are mainly Quenched and Tempered types, and I don't
expect them to be textured.
But maybe I'm wrong... What's your opinion ?
Michel
[/quote:03bd9fb73a]
Sheets are usually rolled, and do generally have texture from the planar
nature of the cold work.
You can partly eliminate texture by examining tensile specimens cut
parallel to the rolling direction and 90 degrees to it, parallel to the
axis of the rolls used to produce the sheet.
Tough to take specimens in the thickness direction, but if you were to
be careful, you might be able to get a compressive Young's modulus from
the through thickness direction.
You could perhaps even investigate ultrasonic modulus measurements to
dig into the question of texture....... and some metallography would
always be informative.
If it isn't texture, then your measuring techniques are called into
question as otherwise potentially a waste of time and money.
You don't want to be in that position.
Jim |
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| Michael Dahms |
| Posted: Mon Jan 24, 2005 6:53 am |
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Guest
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Michel PIETTE wrote:
[quote:b832ba7efe]I fully agree that E depends on orientation.
Nevertheless, our steels are mainly Quenched and Tempered types, and I don't
expect them to be textured.
But maybe I'm wrong... What's your opinion ?
[/quote:b832ba7efe]
Measure it!
Michael Dahms
And stop top-posting. |
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| Michael Dahms |
| Posted: Mon Jan 24, 2005 6:55 am |
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dmartin@newarts.com wrote:
[quote:38726ae9b0]Can the anisotropy of steel's young's modulus really be as high as a
factor of two? I'm looking on the web for a numeric range but haven't
found one yet.
[/quote:38726ae9b0]
I doubt. 140 GPa looks like an austenitic steel.
Michael Dahms |
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| tfagan |
| Posted: Mon Jan 24, 2005 6:32 pm |
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http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/
try this, you can get all chapter listed there. I think link was missing
..pdf
"jbuch" <jbuch@CUTHERErevealed.net> wrote in message
news:csso0c01a2v@enews3.newsguy.com...
[quote:0434be60ee]dmartin@newarts.com wrote:
jbuch wrote:
Michel PIETTE wrote:
Good morning,
If you go here and look at the slide near the very end.... titled
anisotropy....
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.
you will find listed the claim that the elastic modulus for Iron in
the
face edge 100 directions is about 135 Gpa and the modulus for Iron in
the cell diagonal 111 direction is about 273 Gpa.
Very nice presentation.
Thanks Jim, it is just what I was looking for unfortunately he link is
broken.
Email the author......
mmyliu@polyu.edu.hk
Ask if he will give you the link to his excellent materials notes.
[/quote:0434be60ee] |
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| Trina |
| Posted: Tue Feb 01, 2005 7:26 am |
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Guest
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Two years ago I did some tensile tests of aluminium and copper foils
and found that the moduli were significantly smaller than quoted
values. It is quite difficult to test foils though, so my colleague
took the foils to another place and performed some sensitive three
point bend instead. The values he got were similar to the quoted
values. So perhaps you could perform a three point bend test
(apparently you can design it to be very sensitive) to check.
At the same time, we were also interested in the yield values, and it
was surprising to me that it was such a difficult measurement. Further
depending on how the stress-strain curve is fitted, e.g. power
law/bilinear, the yield value varies significantly. Now, I am more of
a soft matter person and was not so experienced with stiff, plastically
deforming materials, so I was generally surprised to find that those
whom I was working with (whom I presumed were more well verse with the
problem) were scratching their heads over this matter. Does anyone
have similar experience on measuring yield stress/strain? |
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