Applying Acceleration to User-Specified Location
Folks,
It seems like the ACEL command acts precisely at the center of gravity of the model. If I wanted the acceleration to act at a different location in the model, is there a way 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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Matt,
At the top of my head, you may want to shift the CG to your desired
location by attaching mass elements (MASS21) to a node at that specific
location and apply acceleration using ACEL — this mass element will then
respond based on its location, and create the inertial effects you want.
Best,
Mohammad
---====
Mohammad A Gharaibeh, Ph.D.
Associate Professor
Department of Mechanical Engineering
The Hashemite University
P.O. Box 330127
Zarqa, 13133, Jordan
Tel: +962 - 5 - 390 3333 Ext. 4771
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On Mon, 14 Apr 2025 at 8:57 PM Matthew Ridzon, PE via Xansys <
xansys-temp@list.xansys.org> wrote:
Folks,
It seems like the ACEL command acts precisely at the center of gravity of
the model. If I wanted the acceleration to act at a different location in
the model, is there a way 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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Hi Matt,
If you are applying translational accels for shears it wouldn’t matter
since it’s a straight F=ma problem. Derived acels don’t require CG. Could
be at origin or infinity.
Angular acels on the other hand get a little more tricky.
Moment = mass mom of inertia x angular acel where I inertia depends on the
CG. You’ll get different moment reactions as you change the CG.
Dcomg would give you different moment loads as you change the CG. Can do a
quick test with the following :
Cgloc, X loc , Y loc, Z loc
Acel, X acel, y acel, Z acel
Dcgomg, x Ang acel, y Ang acel, z Ang acel
Thanks,
Nelson
On Mon, Apr 14, 2025 at 10:56 AM Matthew Ridzon, PE via Xansys <
xansys-temp@list.xansys.org> wrote:
Folks,
It seems like the ACEL command acts precisely at the center of gravity of
the model. If I wanted the acceleration to act at a different location in
the model, is there a way 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
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Hi Matt,
A potential approach is to modify the density of some elements to be almost
zero and have ACEL act on the mass of interest.
Thanks,
Jason
On Mon, Apr 14, 2025 at 6:47 PM Nelson Ho via Xansys <
xansys-temp@list.xansys.org> wrote:
Hi Matt,
If you are applying translational accels for shears it wouldn’t matter
since it’s a straight F=ma problem. Derived acels don’t require CG. Could
be at origin or infinity.
Angular acels on the other hand get a little more tricky.
Moment = mass mom of inertia x angular acel where I inertia depends on the
CG. You’ll get different moment reactions as you change the CG.
Dcomg would give you different moment loads as you change the CG. Can do a
quick test with the following :
Cgloc, X loc , Y loc, Z loc
Acel, X acel, y acel, Z acel
Dcgomg, x Ang acel, y Ang acel, z Ang acel
Thanks,
Nelson
On Mon, Apr 14, 2025 at 10:56 AM Matthew Ridzon, PE via Xansys <
xansys-temp@list.xansys.org> wrote:
Folks,
It seems like the ACEL command acts precisely at the center of gravity of
the model. If I wanted the acceleration to act at a different location
in
the model, is there a way 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
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If
you are not the intended recipient of this message, please notify the
sender immediately, and delete the message and any attachments. Any
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any
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is
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Hello Matt,
I am wondering, why do you need that, ACEL is a body load which acts at the CG of the body. What kind of physics are you simulating, I am intrigued.
Nevertheless, if you want to use ACEL command and shift the point of application of the load i.e. CG, I guess one of the option is to use point load OR distributed load based on the complexity of your model.
I remember using surface elements (SURF154) to model insulation weight and use ADMAS (to add mass). I would overlay the surface elements on the 3D model.
To balance the total weight u might have to reduce the density for the material assigned to your model and compensate that thru point load OR distributed mass.
Best Regards
Anjum
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 14 April 2025 23:26
To: xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Applying Acceleration to User-Specified Location
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Folks,
It seems like the ACEL command acts precisely at the center of gravity of the model. If I wanted the acceleration to act at a different location in the model, is there a way 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.
Dear Mr. Ridzon,
if my understanding is correct, ACEL apples a uniform force field on the entire body. It is not a concentrated load at the center of mass. The load resultant is however and by definition at the center of mass, so if you clamp it, you get no reaction moment.
Best regards
Riccardo Testi
Development and Strategies
2 Wheeler Engines Technical Centre
Piaggio & C. S.p.A
Viale Rinaldo Piaggio, 25
56025 Pontedera (Pisa) - ITALY
Phone: +39 0587 272850
Fax: +39 0587 272010
Mobile: +39 339 7241918
E-mail: riccardo.testi@piaggio.com
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: Monday, April 14, 2025 7:56 PM
To: xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [Xansys] Applying Acceleration to User-Specified Location
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Folks,
It seems like the ACEL command acts precisely at the center of gravity of the model. If I wanted the acceleration to act at a different location in the model, is there a way 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://urlsand.esvalabs.com/?u=http%3A%2F%2Fwww.prime-engineer.com&e=6e97a7e3&h=87561189&f=y&p=y < https://urlsand.esvalabs.com/?u=http%3A%2F%2Fwww.prime-engineer.com%2F&e=6e97a7e3&h=63971262&f=y&p=y >
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Anjum,
I am working on a small test problem (cantilevered beam fixed at one end) to benchmark some response spectrum stuff versus static acceleration. For the purposes here, I'd like to avoid getting into those details so we don't get off track. In short, the spectrum excitations are applied at boundary conditions in Mechanical, while accelerations are applied at the CG. As a result, the comparison does not correlate well partly because the application of the load on the two models is at different locations. Therefore, I would like to apply the accelerations at the model's boundary conditions, so it better correlates with the spectrum results.
-Matt
-----Original Message-----
From: Factoo,Anjum FACTOOA@airproducts.com
Sent: Tuesday, April 15, 2025 5:05 AM
To: XANSYS Mailing List Home xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: RE: [External] [Xansys] Applying Acceleration to User-Specified Location
Hello Matt,
I am wondering, why do you need that, ACEL is a body load which acts at the CG of the body. What kind of physics are you simulating, I am intrigued.
Nevertheless, if you want to use ACEL command and shift the point of application of the load i.e. CG, I guess one of the option is to use point load OR distributed load based on the complexity of your model.
I remember using surface elements (SURF154) to model insulation weight and use ADMAS (to add mass). I would overlay the surface elements on the 3D model.
To balance the total weight u might have to reduce the density for the material assigned to your model and compensate that thru point load OR distributed mass.
Best Regards
Anjum
-----Original Message-----
From: Matthew Ridzon, PE via Xansys xansys-temp@list.xansys.org
Sent: 14 April 2025 23:26
To: xansys-temp@list.xansys.org
Cc: Matthew Ridzon, PE Matt@prime-engineer.com
Subject: [External] [Xansys] Applying Acceleration to User-Specified Location
This email is from an external source. Please exercise caution in opening attachments or links.
Folks,
It seems like the ACEL command acts precisely at the center of gravity of the model. If I wanted the acceleration to act at a different location in the model, is there a way 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.