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Required supports in screw rotation
 
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bhishan.kayastha
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Joined: 10 Dec 2013
Posts: 20

PostPosted: Sun May 18, 2014 6:33 am  Reply with quote

Hi FEA Experts,

I am rotating a screw in clockwise direction that is inside the cylinder to calculate a moment reaction force. I have applied the supports as shown in the attached image as follows:

http://postimg.org/image/a6ekuzi3z/

I am always getting the warning message as follows:

"One or more MPC contact regions or remote boundary conditions may have conflicts with other applied boundary conditions or other contact regions. This may reduce solution accuracy. Tip: You may graphically display FE Connections from the Solution Information Object for non-cyclic analysis. Refer to Troubleshooting in the Help System for more details."

"One or more bodies may be underconstrained and experiencing rigid body motion. Weak springs have been added to attain a solution. Refer to Troubleshooting in the Help System for more details."


Can anyone please help me in this matter ? If you need any additional information. Let me know.

Thanks a lot in advance.


Bhishan Kayastha
Flinders University
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ayo.brimmo
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Joined: 01 Jul 2013
Posts: 38
Location: Masdar City, Abu Dhabi

PostPosted: Sun May 18, 2014 7:12 am  Reply with quote

Imagine what would happened if you had this same setup in real life. If you don't constrain the screw all through radially, it would most likely fall off.

To avoid rigid body motion, try making the bone a full cylinder rather than just a sector

Best,
Ayo Brimmo
Masdar

-----Original Message-----
From: Xansys [mailto:xansys-bounces@xansys.org] On Behalf Of bhishan.kayastha
Sent: Sunday, May 18, 2014 5:33 PM
To: xansys@xansys.org
Subject: [Xansys] Required supports in screw rotation

Hi FEA Experts,

I am rotating a screw in clockwise direction that is inside the cylinder to calculate a moment reaction force. I have applied the supports as shown in the attached image as follows:

http://postimg.org/image/a6ekuzi3z/

I am always getting the warning message as follows:

"One or more MPC contact regions or remote boundary conditions may have conflicts with other applied boundary conditions or other contact regions. This may reduce solution accuracy. Tip: You may graphically display FE Connections from the Solution Information Object for non-cyclic analysis. Refer to Troubleshooting in the Help System for more details."

"One or more bodies may be underconstrained and experiencing rigid body motion. Weak springs have been added to attain a solution. Refer to Troubleshooting in the Help System for more details."


Can anyone please help me in this matter ? If you need any additional information. Let me know.

Thanks a lot in advance.


Bhishan Kayastha
Flinders University






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Ayo Brimmo
Research Engineer
Masdar Institute of Science and Technology
UAE.
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bhishan.kayastha
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Joined: 10 Dec 2013
Posts: 20

PostPosted: Sun May 18, 2014 7:22 am  Reply with quote

Hi Ayo.brimmo,

That is a symmetry divided by 2 planes. The original cylinder was a full cylinder. I just did that to reduce computational time.

thanks.

Bhishan Kayastha
Flinders University
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ayo.brimmo
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Joined: 01 Jul 2013
Posts: 38
Location: Masdar City, Abu Dhabi

PostPosted: Sun May 18, 2014 7:32 am  Reply with quote

How this would work is beyond me.

Anyways, if the solution failed to converge what you should be bothered about is the error message not the warning message.

-----Original Message-----
From: Xansys [mailto:xansys-bounces@xansys.org] On Behalf Of bhishan.kayastha
Sent: Sunday, May 18, 2014 6:22 PM
To: xansys@xansys.org
Subject: Re: [Xansys] Required supports in screw rotation

Hi Ayo.brimmo,

That is a symmetry divided by 2 planes. The original cylinder was a full cylinder. I just did that to reduce computational time.

thanks.

Bhishan Kayastha
Flinders University






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| The Online Community for users of ANSYS, Inc. Software |
| Hosted by PADT - www.padtinc.com |
| Send administrative requests to xansys-mod@tynecomp.co.uk |
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| Hosted by PADT - www.padtinc.com |
| Send administrative requests to xansys-mod@tynecomp.co.uk |
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Ayo Brimmo
Research Engineer
Masdar Institute of Science and Technology
UAE.
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bhishan.kayastha
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Joined: 10 Dec 2013
Posts: 20

PostPosted: Sun May 18, 2014 7:42 am  Reply with quote

Thanks for the prompt reply. If it was full cylinder, where would you expect to have the supports ?

Thanks.

Bhishan Kayastha
Flinders University
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ayo.brimmo
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Joined: 01 Jul 2013
Posts: 38
Location: Masdar City, Abu Dhabi

PostPosted: Sun May 18, 2014 7:51 am  Reply with quote

This totally depends on what you are trying to model.

-----Original Message-----
From: Xansys [mailto:xansys-bounces@xansys.org] On Behalf Of bhishan.kayastha
Sent: Sunday, May 18, 2014 6:43 PM
To: xansys@xansys.org
Subject: Re: [Xansys] Required supports in screw rotation

Thanks for the prompt reply. If it was full cylinder, where would you expect to have the supports ?

Thanks.

Bhishan Kayastha
Flinders University






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| Send administrative requests to xansys-mod@tynecomp.co.uk |
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Ayo Brimmo
Research Engineer
Masdar Institute of Science and Technology
UAE.
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bhishan.kayastha
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Joined: 10 Dec 2013
Posts: 20

PostPosted: Sun May 18, 2014 7:58 am  Reply with quote

Hi Ayo,

I am trying to make a simple continuum model of bone (cancellous bone) in which screw rotates. I want to find out moment reaction forces due to rotation so that i can correlate the degree of rotation with moment reaction forces in each step of rotation (5 degrees/step). Let me know if i have provided enough information.

Thanks.

Bhishan kayastha
Flinders University
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martin.mazurowski.
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Joined: 08 Apr 2014
Posts: 47

PostPosted: Wed May 21, 2014 6:05 am  Reply with quote

Hi,

are you aware of the fact that if you want to use symmetry, not only the geometry has to be symmetric but also the BCs?

Best regards.
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Martin Mazurowski
Drehmoment GmbH
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bhishan.kayastha
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Joined: 10 Dec 2013
Posts: 20

PostPosted: Mon May 26, 2014 5:36 am  Reply with quote

Hi Martin,

Thanks for the reply. I am sorry that i wasnt able to reply on time. I wasnt aware of the fact that boundry condition had to be symmetric too. I will do that and lets see how the results come out.

Thanks.


Best,

Bhishan kayastha
Flinders University
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