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

From:	jbuch
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	Fri, 21 Jan 2005 19:41:39 -0600

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.

--
................................

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From:	Michel PIETTE
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	Sat, 22 Jan 2005 19:17:43 +0100

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" a écrit dans le message de news:
cssasq022s8@enews4.newsguy.com...
> 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
>

From:	jbuch
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	Sat, 22 Jan 2005 17:33:19 -0600

Michel PIETTE wrote:
> 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
>

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

From:	dmartin at newarts.com
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	21 Jan 2005 19:22:49 -0800

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.

From:	jbuch
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	Fri, 21 Jan 2005 23:25:25 -0600

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.

From:	Gerben Sinnema
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	Sat, 22 Jan 2005 16:19:51 GMT

the link is:
http://www.me.polyu.edu.hk/subject/me3302(yliu)/notes/chapt1.pdf

"jbuch" wrote in message
news:csso0c01a2v@enews3.newsguy.com...
> 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.
>

From:	dmartin at newarts.com
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	21 Jan 2005 12:21:52 -0800

Michael Dahms wrote:
> 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
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

From:	Michael Dahms
Subject:	Re: Young's Modulus / Steel / Abnormal values
Date:	Fri, 21 Jan 2005 12:15:35 +0100

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.

Michael Dahms

f'up2 sci.materials