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[Xansys] problem about coefficient of ratio
 
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yongbinglee
Guest





PostPosted: Fri Oct 17, 2003 6:51 am  Reply with quote

Dear all£¬

Long time no see. Miss you all very much.

I am doing a thermal-electrical analysis(solid69 used) with thermal and electrical contact(targe170 and conta173 used). But the ANSYS tell me that "coeffiecient of ratio exceeds 1.0e8". Can anybody tell me why encounter this problem and how to solve it?

Any hint will be appreciated deeply.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

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Shinbrot, Adam
Guest





PostPosted: Fri Oct 17, 2003 7:04 am  Reply with quote

Your model is not seeing contact.

If we had a FAQ, this question would certainly be in it. You could therefore
search the archive if you want more information.

********************************
Adam Shinbrot
Zimmer Spine
Tel.: 952.830.6324 Fax: 952.837.6924
--email address suppressed--
********************************
"I¡¯ve been Zimmered!¡±


-----Original Message-----
From: yongbinglee [mailto:--email address suppressed--]
Sent: Friday, October 17, 2003 8:40 AM
To: --email address suppressed--
Subject: [Xansys] problem about coefficient of ratio


Dear all£¬

Long time no see. Miss you all very much.

I am doing a thermal-electrical analysis(solid69 used) with thermal and
electrical contact(targe170 and conta173 used). But the ANSYS tell me that
"coeffiecient of ratio exceeds 1.0e8". Can anybody tell me why encounter
this problem and how to solve it?

Any hint will be appreciated deeply.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

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yongbinglee
Guest





PostPosted: Fri Oct 17, 2003 7:18 am  Reply with quote

Dear all,

I think I should add some information about this warning,
I looked through the information in ANSYS output window and found that the element with maximium matrix coefficient is 7690(solid69),and the element with minimum matrix coefficient is element 16160(conta173).I selected the two element and plotted them in graphics window. The two elment is very regular.

Does anyone have experiences about this?

Many thanks.


Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

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Frederick, Robert T.
Guest





PostPosted: Fri Oct 17, 2003 7:19 am  Reply with quote

Yongbing,

I can't comment on your "coefficient of ratio" question, but as far as I
know (and as of release 6.1 - yeh, our IT guys are real sharp around here,
still working in 6.1), targe170 and conta173 do not provide electrical
contact, so you will need to take care of the electrical contact by coupling
or other means. I hope to hear I'm wrong on this, because I'd like to be
able to put an interface resistance in my thermal electric models using a
contact element.

Bob Frederick
Engr. Analyst
Tyco Electronics
Harrisburg, PA



-----Original Message-----
From: yongbinglee [mailto:--email address suppressed--]
Sent: Friday, October 17, 2003 9:40 AM
To: --email address suppressed--
Subject: [Xansys] problem about coefficient of ratio


Dear all£¬

Long time no see. Miss you all very much.

I am doing a thermal-electrical analysis(solid69 used) with thermal and
electrical contact(targe170 and conta173 used). But the ANSYS tell me that
"coeffiecient of ratio exceeds 1.0e8". Can anybody tell me why encounter
this problem and how to solve it?

Any hint will be appreciated deeply.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

Post generated using Mail2Forum (http://www.mail2forum.com)
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yongbinglee
Guest





PostPosted: Fri Oct 17, 2003 7:42 am  Reply with quote

Hi Adam,

Thank you very much. I have searched all the archives in xansys.org and ansys.net and cannot find any list about coefficient of ratio. Can you give me some more information?
I will check my model carefully to see if it was created correctly.

Bob,thank you too for your quick reponse. In ansys7.1, conta173 and targe170 really have VOLT Dof and electrical contact conductance(ECC) can be defined easily.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

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yongbinglee
Guest





PostPosted: Fri Oct 17, 2003 7:43 am  Reply with quote

Hi Adam,

Thank you very much. I have searched all the archives in xansys.org and ansys.net and cannot find any list about coefficient of ratio. Can you give me some more information?
I will check my model carefully to see if it was created correctly.

Bob,thank you too for your quick reponse. In ansys7.1, conta173 and targe170 really have VOLT Dof and electrical contact conductance(ECC) can be defined easily.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

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Shinbrot, Adam
Guest





PostPosted: Fri Oct 17, 2003 8:08 am  Reply with quote

The message refers to the fact that the stiffness matrix is seeing what is
essentially zero stiffness. Now why would it see zero stiffness? Because the
contact region is open, most likely.

********************************
Adam Shinbrot
Zimmer Spine
Tel.: 952.830.6324 Fax: 952.837.6924
--email address suppressed--
********************************
"I¡¯ve been Zimmered!¡±


-----Original Message-----
From: yongbinglee [mailto:--email address suppressed--]
Sent: Friday, October 17, 2003 9:31 AM
To: --email address suppressed--
Subject: RE: [Xansys] problem about coefficient of ratio


Hi Adam,

Thank you very much. I have searched all the archives in xansys.org and
ansys.net and cannot find any list about coefficient of ratio. Can you give
me some more information?
I will check my model carefully to see if it was created correctly.

Bob,thank you too for your quick reponse. In ansys7.1, conta173 and targe170
really have VOLT Dof and electrical contact conductance(ECC) can be defined
easily.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

Post generated using Mail2Forum (http://www.mail2forum.com)
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Sheldon Imaoka
Guest





PostPosted: Fri Oct 17, 2003 1:55 pm  Reply with quote

Hi Adam and Yongbing,

Actually, the coefficient ratio warning is probably because of your thermal
and electrical properties.

Depending on the material and the units you use, your thermal and electrical
values may differ significantly - this is possible with your materials as
well as your thermal and electrical contact conductance values. For
example, if you had copper in SI units, your thermal conductivity may be
around 400 W/m/K whereas your resistivity may be around 2e-8 ohm m, which
results in big differences in terms in the [K] matrix.

If you expect these values to differ significantly, you can ignore the
warning. The warning is usually there to make sure that in a single-field
analysis, you have input properties correctly. You will often see this
warning in coupled-field analyses because the values used in the two (or
more) physics may not be in the same order of magnitude.

Regards,
Sheldon


----- Original Message -----
From: "Shinbrot, Adam" <--email address suppressed-->
To: "'ANSYS User Discussion List'" <--email address suppressed-->
Sent: Friday, October 17, 2003 7:56 AM
Subject: RE: [Xansys] problem about coefficient of ratio


> The message refers to the fact that the stiffness matrix is seeing what is
> essentially zero stiffness. Now why would it see zero stiffness? Because
the
> contact region is open, most likely.
>
> ********************************
> Adam Shinbrot
> Zimmer Spine
> Tel.: 952.830.6324 Fax: 952.837.6924
> --email address suppressed--
> ********************************
> "I’ve been Zimmered!”
>
>
> -----Original Message-----
> From: yongbinglee [mailto:--email address suppressed--]
> Sent: Friday, October 17, 2003 9:31 AM
> To: --email address suppressed--
> Subject: RE: [Xansys] problem about coefficient of ratio
>
>
> Hi Adam,
>
> Thank you very much. I have searched all the archives in xansys.org and
> ansys.net and cannot find any list about coefficient of ratio. Can you
give
> me some more information?
> I will check my model carefully to see if it was created correctly.
>
> Bob,thank you too for your quick reponse. In ansys7.1, conta173 and
targe170
> really have VOLT Dof and electrical contact conductance(ECC) can be
defined
> easily.
>
> Best Regards,
>
> Yours,
> Yongbing,Lee
>
> Body Manufacturing Techonology Center
> SJTU
> ^----------------------------------------------------------------------
> | XANSYS - www.xansys.org |
> | List hosted by PADT: www.padtinc.com |
> ^----------------------------------------------------------------------
>

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Shinbrot, Adam
Guest





PostPosted: Fri Oct 17, 2003 5:08 pm  Reply with quote

Thanks, Sheldon.


-----Original Message-----
From: Sheldon Imaoka
To: ANSYS User Discussion List
Sent: 10/17/2003 3:43 PM
Subject: Re: [Xansys] problem about coefficient of ratio

Hi Adam and Yongbing,

Actually, the coefficient ratio warning is probably because of your
thermal
and electrical properties.

Depending on the material and the units you use, your thermal and
electrical
values may differ significantly - this is possible with your materials
as
well as your thermal and electrical contact conductance values. For
example, if you had copper in SI units, your thermal conductivity may be
around 400 W/m/K whereas your resistivity may be around 2e-8 ohm m,
which
results in big differences in terms in the [K] matrix.

If you expect these values to differ significantly, you can ignore the
warning. The warning is usually there to make sure that in a
single-field
analysis, you have input properties correctly. You will often see this
warning in coupled-field analyses because the values used in the two (or
more) physics may not be in the same order of magnitude.

Regards,
Sheldon


----- Original Message -----
From: "Shinbrot, Adam" <--email address suppressed-->
To: "'ANSYS User Discussion List'" <--email address suppressed-->
Sent: Friday, October 17, 2003 7:56 AM
Subject: RE: [Xansys] problem about coefficient of ratio


> The message refers to the fact that the stiffness matrix is seeing
what is
> essentially zero stiffness. Now why would it see zero stiffness?
Because
the
> contact region is open, most likely.
>
> ********************************
> Adam Shinbrot
> Zimmer Spine
> Tel.: 952.830.6324 Fax: 952.837.6924
> --email address suppressed--
> ********************************
> "I’ve been Zimmered!”
>
>
> -----Original Message-----
> From: yongbinglee [mailto:--email address suppressed--]
> Sent: Friday, October 17, 2003 9:31 AM
> To: --email address suppressed--
> Subject: RE: [Xansys] problem about coefficient of ratio
>
>
> Hi Adam,
>
> Thank you very much. I have searched all the archives in xansys.org
and
> ansys.net and cannot find any list about coefficient of ratio. Can you
give
> me some more information?
> I will check my model carefully to see if it was created correctly.
>
> Bob,thank you too for your quick reponse. In ansys7.1, conta173 and
targe170
> really have VOLT Dof and electrical contact conductance(ECC) can be
defined
> easily.
>
> Best Regards,
>
> Yours,
> Yongbing,Lee
>
> Body Manufacturing Techonology Center
> SJTU
>
^----------------------------------------------------------------------
> | XANSYS - www.xansys.org |
> | List hosted by PADT: www.padtinc.com |
>
^----------------------------------------------------------------------
>

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yongbinglee
Guest





PostPosted: Fri Oct 17, 2003 11:50 pm  Reply with quote

Many thanks to Sheldon.

I think what you analyzed is correct.Just as you had analyzed,I really have copper in my model in SI units. In order to validate your analysis, I purposely changed the resistivity of copper to a relatively lower value(about 2e-4 ohm*m) and solved again. Wonderfully, The warning is removed now.:)

Thank you again. And thanks to Adam too.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

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yongbinglee
Guest





PostPosted: Fri Oct 17, 2003 11:52 pm  Reply with quote

Many¡¡thanks to Sheldon.

I think what you analyzed is correct.Just as you had analyzed,I really have copper in my model in SI units. In order to validate your analysis, I purposely changed the resistivity of copper to a relatively lower value(about 2e-4 ohm*m) and solved again. Wonderfully, The warning is removed now.:)

Thank you again. And thanks to Adam too.

Best Regards,

Yours,
Yongbing,Lee

Body Manufacturing Techonology Center
SJTU

Post generated using Mail2Forum (http://www.mail2forum.com)
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