Changing Material Properties Between Load Steps
Folks,
I'm working in v2022R2 Mechanical. I am running a 2-step static analysis. In step 2, I issue a command snippet to alter material properties...
MPDELE,ALPX,ALL
For some reason, the solver is not deleting the material data though. It works perfectly fine if I run a 1-step analysis and issue the command. But it does not work across multiple load steps. Is there an explanation for this?
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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Hi Matt -- I don't think the stiffness matrix and change like that between steps. I've never heard of a good work-around. It is possible to do swaps using element birth and death with elements that are comprised of the same nodes. That's one approach...
Another thing we have done, for CTE analyses, is to create two regimes: One between, say 20C and 200C... and another between 1020C and 1200c. Then we can enforce temperatures that are offset by 1000C and get the new CTE's in effect... those sorts of games to have a fixed material model.
Maybe I'm wrong -- but that's my recollection!
Rod
Rod Scholl
Principal
Phone: 952-405-9710
Email: Rod.Scholl@EpsilonFEA.com
www.EpsilonFEA.com
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: Thursday, August 7, 2025 4:34 PM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [Xansys] Changing Material Properties Between Load Steps
Folks,
I'm working in v2022R2 Mechanical. I am running a 2-step static analysis. In step 2, I issue a command snippet to alter material properties...
MPDELE,ALPX,ALL
For some reason, the solver is not deleting the material data though. It works perfectly fine if I run a 1-step analysis and issue the command. But it does not work across multiple load steps. Is there an explanation for this?
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.
Hello Matt
Have u tried using THEXPAND,OFF command. MPDELE works in PREP7 only.
/solu
time,1
thexpand,off
TREF,428
TUNIF,428
I set the TREF and TUNIF to same temperature, just to be double sure.
Let me know if this work for you in workbench, I have used this in Classic APDL.
Best regards
Anjum
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 08 August 2025 03:04
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Changing Material Properties Between Load Steps
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Folks,
I'm working in v2022R2 Mechanical. I am running a 2-step static analysis. In step 2, I issue a command snippet to alter material properties...
MPDELE,ALPX,ALL
For some reason, the solver is not deleting the material data though. It works perfectly fine if I run a 1-step analysis and issue the command. But it does not work across multiple load steps. Is there an explanation for this?
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.
Anjum, Rod,
Thanks for responding with your feedback! :-)
Anjum,
This is strange. The Help documentation definitely says that MPDELE works in /SOLU, as well as /PREP7. However, it does not seem to behave that way in the software. If I issue the following for load step 2, it almost works properly across multiple load steps:
/PREP7
MPDELE,ALPX,ALL
/SOLU
It will remove the ALPX data for load step 2 and beyond, but a different anomaly pops up...for some reason, Mechanical does not write load step 1 results to the RST. So I'm losing hope in this idea altogether. As a result, I abandoned the idea and used THEXPAND instead. I must have forgotten about that command. It's much simpler and quicker. Thanks for sharing that information.
I'm good now! I appreciate the help!
-Matt
-----Original Message-----
From: Factoo,Anjum FACTOOA@airproducts.com
Sent: Thursday, August 7, 2025 11:41 PM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: RE: [External] [Xansys] Changing Material Properties Between Load Steps
Hello Matt
Have u tried using THEXPAND,OFF command. MPDELE works in PREP7 only.
/solu
time,1
thexpand,off
TREF,428
TUNIF,428
I set the TREF and TUNIF to same temperature, just to be double sure.
Let me know if this work for you in workbench, I have used this in Classic APDL.
Best regards
Anjum
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 08 August 2025 03:04
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Changing Material Properties Between Load Steps
This email is from an external source. Please exercise caution in opening attachments or links.
Folks,
I'm working in v2022R2 Mechanical. I am running a 2-step static analysis. In step 2, I issue a command snippet to alter material properties...
MPDELE,ALPX,ALL
For some reason, the solver is not deleting the material data though. It works perfectly fine if I run a 1-step analysis and issue the command. But it does not work across multiple load steps. Is there an explanation for this?
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.
Matt,
I’m thinking that when you left the SOLUTION processor, entered PREP7 and then went back into SOLUTION, that ANSYS will take that as the start of a new analysis and overwrite your previous solution files including load step 1 results. You may need to issue an ANTYPE,,RESTART command at the beginning of the second SOLUTION phase to tell it you want to continue the previous analysis by adding a load step.
/SOLU
RESCONTROL,…
…
SOLVE
FINISH
PREP7
MPDELE,ALPX,ALL
FINISH
/SOLU
ANTYPE,,RESTART,…
…
SOLVE
FINISH
See section 5.8 in the Basic Analysis Guide which discusses restarts. You may also need a RESCONTROL command near the beginning of the first SOLUTION to create the proper restart files as I don’t remember what the defaults are for restarts.
However, the problem with this method is that the manual clearly states that the material properties may not be changed in a multi frame restart, so your MPDELE command may not work with this method.
ANSYS originally had another restart method known as single frame restart. I don’t know if it is undocumented but still available, or if the MPDELE command would work in this situation.
THEXPAND,OFF
seems to be the way to go in this situation.
--
Mitch Voehl
CEO and Engineering Consultant
Summit Analysis, Inc.
78748 410th Ave
Lakefield, MN 56150
651-287-2360
www.summitanalysis.com
Specializing in the use of ANSYS (R) finite element analysis software
On 08/08/2025 12:41 PM CDT Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org wrote:
Anjum, Rod,
Thanks for responding with your feedback! :-)
Anjum,
This is strange. The Help documentation definitely says that MPDELE works in /SOLU, as well as /PREP7. However, it does not seem to behave that way in the software. If I issue the following for load step 2, it almost works properly across multiple load steps:
/PREP7
MPDELE,ALPX,ALL
/SOLU
It will remove the ALPX data for load step 2 and beyond, but a different anomaly pops up...for some reason, Mechanical does not write load step 1 results to the RST. So I'm losing hope in this idea altogether. As a result, I abandoned the idea and used THEXPAND instead. I must have forgotten about that command. It's much simpler and quicker. Thanks for sharing that information.
I'm good now! I appreciate the help!
-Matt
-----Original Message-----
From: Factoo,Anjum FACTOOA@airproducts.com
Sent: Thursday, August 7, 2025 11:41 PM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: RE: [External] [Xansys] Changing Material Properties Between Load Steps
Hello Matt
Have u tried using THEXPAND,OFF command. MPDELE works in PREP7 only.
/solu
time,1
thexpand,off
TREF,428
TUNIF,428
I set the TREF and TUNIF to same temperature, just to be double sure.
Let me know if this work for you in workbench, I have used this in Classic APDL.
Best regards
Anjum
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 08 August 2025 03:04
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Changing Material Properties Between Load Steps
This email is from an external source. Please exercise caution in opening attachments or links.
Folks,
I'm working in v2022R2 Mechanical. I am running a 2-step static analysis. In step 2, I issue a command snippet to alter material properties...
MPDELE,ALPX,ALL
For some reason, the solver is not deleting the material data though. It works perfectly fine if I run a 1-step analysis and issue the command. But it does not work across multiple load steps. Is there an explanation for this?
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.
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I've done something similar but with the MPCHG command. ANSYS complains that this is a non-standard usage but lets me do it - I'm guessing you will be alright.
Regards,
David
David J. Gross, P.E., ASME Fellow | Dominion Engineering, Inc.
Director, Federal Services
12100 Sunrise Valley Drive, Suite 220 | Reston, VA 20191
office 703.657.7300 | desk 703.657.7311 | mobile 301.580.3066
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-----Original Message-----
From: Mitch Voehl via Xansys xansys-temp@list.xansys.org
Sent: Sunday, August 10, 2025 1:35 AM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Mitch Voehl mitchpublic@voehl.us
Subject: [Xansys] Re: [External] Changing Material Properties Between Load Steps
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Matt,
I’m thinking that when you left the SOLUTION processor, entered PREP7 and then went back into SOLUTION, that ANSYS will take that as the start of a new analysis and overwrite your previous solution files including load step 1 results. You may need to issue an ANTYPE,,RESTART command at the beginning of the second SOLUTION phase to tell it you want to continue the previous analysis by adding a load step.
/SOLU
RESCONTROL,…
…
SOLVE
FINISH
PREP7
MPDELE,ALPX,ALL
FINISH
/SOLU
ANTYPE,,RESTART,…
…
SOLVE
FINISH
See section 5.8 in the Basic Analysis Guide which discusses restarts. You may also need a RESCONTROL command near the beginning of the first SOLUTION to create the proper restart files as I don’t remember what the defaults are for restarts.
However, the problem with this method is that the manual clearly states that the material properties may not be changed in a multi frame restart, so your MPDELE command may not work with this method.
ANSYS originally had another restart method known as single frame restart. I don’t know if it is undocumented but still available, or if the MPDELE command would work in this situation.
THEXPAND,OFF
seems to be the way to go in this situation.
--
Mitch Voehl
CEO and Engineering Consultant
Summit Analysis, Inc.
78748 410th Ave
Lakefield, MN 56150
651-287-2360
www.summitanalysis.comhttp://www.summitanalysis.com
Specializing in the use of ANSYS (R) finite element analysis software
On 08/08/2025 12:41 PM CDT Matthew Ridzon, PE via Xansys <xansys-temp@list.xansys.orgmailto:xansys-temp@list.xansys.org> wrote:
Anjum, Rod,
Thanks for responding with your feedback! :-)
Anjum,
This is strange. The Help documentation definitely says that MPDELE works in /SOLU, as well as /PREP7. However, it does not seem to behave that way in the software. If I issue the following for load step 2, it almost works properly across multiple load steps:
/PREP7
MPDELE,ALPX,ALL
/SOLU
It will remove the ALPX data for load step 2 and beyond, but a different anomaly pops up...for some reason, Mechanical does not write load step 1 results to the RST. So I'm losing hope in this idea altogether. As a result, I abandoned the idea and used THEXPAND instead. I must have forgotten about that command. It's much simpler and quicker. Thanks for sharing that information.
I'm good now! I appreciate the help!
-Matt
-----Original Message-----
From: Factoo,Anjum <FACTOOA@airproducts.commailto:FACTOOA@airproducts.com>
Sent: Thursday, August 7, 2025 11:41 PM
To: XANSYS Mailing List Home <xansys-temp@list.xansys.orgmailto:xansys-temp@list.xansys.org>
Cc: Matthew Ridzon, PE <Matt@prime-engineer.commailto:Matt@prime-engineer.com>
Subject: RE: [External] [Xansys] Changing Material Properties Between
Load Steps
Hello Matt
Have u tried using THEXPAND,OFF command. MPDELE works in PREP7 only.
/solu
time,1
thexpand,off
TREF,428
TUNIF,428
I set the TREF and TUNIF to same temperature, just to be double sure.
Let me know if this work for you in workbench, I have used this in Classic APDL.
Best regards
Anjum
-----Original Message-----
From: Matthew Ridzon, PE via Xansys <xansys-temp@list.xansys.orgmailto:xansys-temp@list.xansys.org>
Sent: 08 August 2025 03:04
To: XANSYS Mailing List Home <xansys-temp@list.xansys.orgmailto:xansys-temp@list.xansys.org>
Cc: Matthew Ridzon, PE <Matt@prime-engineer.commailto:Matt@prime-engineer.com>
Subject: [External] [Xansys] Changing Material Properties Between Load
Steps
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Folks,
I'm working in v2022R2 Mechanical. I am running a 2-step static analysis. In step 2, I issue a command snippet to alter material properties...
MPDELE,ALPX,ALL
For some reason, the solver is not deleting the material data though. It works perfectly fine if I run a 1-step analysis and issue the command. But it does not work across multiple load steps. Is there an explanation for this?
Matt Ridzon, PE, MSME
Sr. Engineering Analyst
Email matt@prime-engineer.com<mailto:matt@prime-engineer.commailto:matt@prime-engineer.com%3cmailto:matt@prime-engineer.com>
Mail 266 Main St, Burlington, VT 05401
Web http://www.prime-engineer.com/<http://www.prime-engineer.com/http://www.prime-engineer.com/%3chttp:/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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