Application of stress as a bodyforce

Numerical methods and mathematical models of Elmer
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Captain Slow
Posts: 72
Joined: 10 Nov 2009, 19:17

Application of stress as a bodyforce

Post by Captain Slow »

Hello,

I'm trying to execute eigenfrequency analysis of a beam with a stress distribution within it. I'm applying the stress distribution as a bodyforce which varies through the beams thickness and along its length. Is it correct to input the stress as a force per unit area?

The stress I have applied has had no effect on the eigenfrequencies (and I think it should) so I'm wondering if I have applied the body condition incorrectly.

Attached are my sif and mesh files.
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freecantilever.msh
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case.sif
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Captain Slow
Posts: 72
Joined: 10 Nov 2009, 19:17

Re: Application of stress as a bodyforce

Post by Captain Slow »

Captain Slow wrote: Is it correct to input the stress as a force per unit area?
No comments on the bodyforce application, particularly on the above?
raback
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Re: Application of stress as a bodyforce

Post by raback »

Hi

I think you need to set "Geometric Stiffness = Logical True" in solver section. See test case "geomstiff".

-Peter
Captain Slow
Posts: 72
Joined: 10 Nov 2009, 19:17

Re: Application of stress as a bodyforce

Post by Captain Slow »

Peter, Thank You for your reply.

Setting "Geometric Stiffness = Logical True" has had no effect on the results.

Is my stress B.C. correct? how does Elmer know that the input is for only stress xx, should I add '',0,0,0''etc for the other components of the stress?
raback
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Re: Application of stress as a bodyforce

Post by raback »

Hi

You're right. In fact there is no such body force available as "Stress(i)", and not even "Stress". There is "Stress Load" and Material property "Pre Stress". Haven't used them myself but these have at least in theory the possibility to take into account stresses.

-Peter
Captain Slow
Posts: 72
Joined: 10 Nov 2009, 19:17

Re: Application of stress as a bodyforce

Post by Captain Slow »

Thanks Peter, I shall look into the other options...
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