Folks,

I am running an eigenvalue buckling analysis (ANTYPE,BUCKLE).  Is there a way to tell the software to only search for buckling modes in certain bodies of the model?  In other words, suppose I have a vacuum tank comprised of a shell and two heads.  If I only want to find the buckling modes in one of the heads, is there a way to tell the software to do that?

Matt Ridzon, PE, MSME
Sr. Engineering Analyst

Email    matt@prime-engineer.commailto:matt@prime-engineer.com
Mail        266 Main St, Burlington, VT 05401
Web      www.prime-engineer.comhttp://www.prime-engineer.com/
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PRIME ENGINEERING LLC

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Hello folks!  I never heard anything back from my email below.  I just want to check one more time to see if anyone has an answer.

-Matt

From: Matthew Ridzon, PE
Sent: Friday, September 12, 2025 3:59 PM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Subject: Searching for Buckling Modes in Specific Body of the Model

Folks,

I am running an eigenvalue buckling analysis (ANTYPE,BUCKLE).  Is there a way to tell the software to only search for buckling modes in certain bodies of the model?  In other words, suppose I have a vacuum tank comprised of a shell and two heads.  If I only want to find the buckling modes in one of the heads, is there a way to tell the software to do that?

Matt Ridzon, PE, MSME
Sr. Engineering Analyst

Email    matt@prime-engineer.commailto:matt@prime-engineer.com
Mail        266 Main St, Burlington, VT 05401
Web      www.prime-engineer.comhttp://www.prime-engineer.com/
[A blue hexagon with white letters  Description automatically generated]
PRIME ENGINEERING LLC

This message (including any attachments) may contain confidential, proprietary, privileged and/or private information. The information is intended to be for the use of the individual or entity designated above. If you are not the intended recipient of this message, please notify the sender immediately, and delete the message and any attachments. Any disclosure, reproduction, distribution or other use of this message or any attachments by an individual or entity other than the intended recipient is prohibited.

Hi Matt,

The solution I can think is to increase the elastic modulus value by 100 or may be 10000 for the bodies that you want to ignore. That will filter out the bodies and you will get the buckling modes in bodies which have realistic elasticity as compared to other ones.

My Disclaimer : I haven't tried this myself. Maybe it turns out to be bullshit.

Thanks
Anjum

-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 08 October 2025 18:04
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Re: Searching for Buckling Modes in Specific Body of the Model

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Hello folks!  I never heard anything back from my email below.  I just want to check one more time to see if anyone has an answer.

-Matt

From: Matthew Ridzon, PE
Sent: Friday, September 12, 2025 3:59 PM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Subject: Searching for Buckling Modes in Specific Body of the Model

Folks,

I am running an eigenvalue buckling analysis (ANTYPE,BUCKLE).  Is there a way to tell the software to only search for buckling modes in certain bodies of the model?  In other words, suppose I have a vacuum tank comprised of a shell and two heads.  If I only want to find the buckling modes in one of the heads, is there a way to tell the software to do that?

Matt Ridzon, PE, MSME
Sr. Engineering Analyst

Email    matt@prime-engineer.commailto:matt@prime-engineer.com
Mail        266 Main St, Burlington, VT 05401
Web      http://www.prime-engineer.com/http://www.prime-engineer.com/
[A blue hexagon with white letters  Description automatically generated] PRIME ENGINEERING LLC

This message (including any attachments) may contain confidential, proprietary, privileged and/or private information. The information is intended to be for the use of the individual or entity designated above. If you are not the intended recipient of this message, please notify the sender immediately, and delete the message and any attachments. Any disclosure, reproduction, distribution or other use of this message or any attachments by an individual or entity other than the intended recipient is prohibited.

I appreciate Anjum's integrity.

I gave it some thought. Maybe there are two possibilities

1. Assign only MDOF's to the nodes in the heads, not in the other part.  (M command). The M command seems to imply you could do this.  We use to do this sort of thing when we had less compute power and had sizeable models to compute the mode shapes.
2. back out the rotational stiffness at the joint of the shell and take the complete model, remove the shells and put springs in their place at the edge of the heads.

As with what Anjum said, I have not tested this, either; refussive materials, garbage it could be.
Thanks
MIke
-----Original Message-----
From: Factoo,Anjum via Xansys xansys-temp@list.xansys.org
Sent: Wednesday, October 8, 2025 9:13 AM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com; Factoo,Anjum FACTOOA@airproducts.com
Subject: [Xansys] Re: [External] Re: Searching for Buckling Modes in Specific Body of the Model

[External]

Hi Matt,

The solution I can think is to increase the elastic modulus value by 100 or may be 10000 for the bodies that you want to ignore. That will filter out the bodies and you will get the buckling modes in bodies which have realistic elasticity as compared to other ones.

My Disclaimer : I haven't tried this myself. Maybe it turns out to be bullshit.

Thanks
Anjum

-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 08 October 2025 18:04
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Re: Searching for Buckling Modes in Specific Body of the Model

This email is from an external source. Please exercise caution in opening attachments or links.

Hello folks!  I never heard anything back from my email below.  I just want to check one more time to see if anyone has an answer.

-Matt

From: Matthew Ridzon, PE
Sent: Friday, September 12, 2025 3:59 PM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Subject: Searching for Buckling Modes in Specific Body of the Model

Folks,

I am running an eigenvalue buckling analysis (ANTYPE,BUCKLE).  Is there a way to tell the software to only search for buckling modes in certain bodies of the model?  In other words, suppose I have a vacuum tank comprised of a shell and two heads.  If I only want to find the buckling modes in one of the heads, is there a way to tell the software to do that?

Matt Ridzon, PE, MSME
Sr. Engineering Analyst

Email    matt@prime-engineer.commailto:matt@prime-engineer.com
Mail        266 Main St, Burlington, VT 05401
Web      https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.prime-engineer.com%2f&c=E,1,C7juI_xDHwq-29bYLSTi6l_eFQlKA4Zgv6ZvKTu36eseipFibHe9QGWO5u_CpGstZaUBvNdEwNyKtWMhhQI5xIZEZbqWFCFEuCM4z339VhP0BfMbaw,,&typo=1https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.prime-engineer.com%2f&c=E,1,mmx51rGvyGM-DMGVE_M321hQBlvN0Hjs2ky8_gSD0BRKbIrZAmUB69ZdVKsyPl1Ck2fI1ecb8wB0tLNAZU-NB2NIQgzXuqDGm1hkvuJCNJW95Q,,&typo=1
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Dr. Juan,

Thanks for the feedback.  Yes, I need to keep the other pieces of the model in place with their correct stiffness.  Otherwise, the pieces being studied will produce incorrect results due to other pieces having artificial stiffnesses.  You mentioned refining the search limits of the eigenvalues and modes within a certain frequency range.  I’m not aware of any way to do this.  Can you share more information about how to do it?

—Matt

From: Dr. Juan Pablo Toledo Gonzalez juan.toledo@complx.com.mx
Sent: Sunday, October 12, 2025 11:49 AM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: Re: [Xansys] Re: Searching for Buckling Modes in Specific Body of the Model

Hi,

If the device you don’t want to analyze does not play an important role in you analysis remove it. I don’t think is the case. You can refine the search limits of eigen values and modes within a certain frequency range, but that requires that you know where to expect.

If you increase the rigidity of the other device as mention in the previous mail, that will increase the overall and it will have an effect.

A way I think you could try is to try to quantify the rigidity that that device has on the shell, and the replace it by a mass with a spring (equivalent rigidity of the device you want to remove). See the image below.

[cid:image001.png@01DC3D2D.223B3340]

Regards,

Dr. Juan Pablo Toledo
General Manager
COMPLX
"Ingeniería Avanzada para Soluciones Reales"
www.complx.com.mxhttp://www.complx.com.mx
Tel: 229 337 1365
Cel: 229 136 5599

El 2025-10-08 06:33, Matthew Ridzon, PE via Xansys escribió:
Hello folks!  I never heard anything back from my email below.  I just want to check one more time to see if anyone has an answer.

-Matt

From: Matthew Ridzon, PE
Sent: Friday, September 12, 2025 3:59 PM
To: XANSYS Mailing List Home <xansys-temp@list.xansys.orgmailto:xansys-temp@list.xansys.org>
Subject: Searching for Buckling Modes in Specific Body of the Model

Folks,

I am running an eigenvalue buckling analysis (ANTYPE,BUCKLE).  Is there a way to tell the software to only search for buckling modes in certain bodies of the model?  In other words, suppose I have a vacuum tank comprised of a shell and two heads.  If I only want to find the buckling modes in one of the heads, is there a way to tell the software to do that?

Matt Ridzon, PE, MSME
Sr. Engineering Analyst

Email    matt@prime-engineer.commailto:matt@prime-engineer.com<mailto:matt@prime-engineer.commailto:matt@prime-engineer.com>
Mail        266 Main St, Burlington, VT 05401
Web      www.prime-engineer.comhttp://www.prime-engineer.comhttp://www.prime-engineer.com/
[A blue hexagon with white letters  Description automatically generated]
PRIME ENGINEERING LLC

This message (including any attachments) may contain confidential, proprietary, privileged and/or private information. The information is intended to be for the use of the individual or entity designated above. If you are not the intended recipient of this message, please notify the sender immediately, and delete the message and any attachments. Any disclosure, reproduction, distribution or other use of this message or any attachments by an individual or entity other than the intended recipient is prohibited.

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