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oyvinkle
Posts: 56
Registered: ‎01-11-2013

Converges of Eigen period

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01-25-2013 01:09 AM

Converges of Eigen period

 

Hey! I have modeled a beam (450X450mm ) length 4500mm in robot using beam elements. And got convergence of the Eigen period when I used 20 elements. I have solved the same problem using the differential equation for the beam without shear def.  Inn the result I get some differences and I have concluded that it must be the shear deformation. When I tried to model the same beam with length 200 m. I got some difftenses and the Eigen period got even bigger than the analytical solution.

 

I tough that the FEM solution always gave a stiffer construction than the analytical tough you impose a fictitious stiffness upon the construction.?????? The mass of the systems are the same.

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Artur.Kosakowski
Posts: 5,057
Registered: ‎12-17-2010

Re: Converges of Eigen period

01-28-2013 05:13 AM in reply to: oyvinkle

If I remember correctly that depends on the mass matrix type and the convergence is from 'above' or from 'bottom' respectively.

 

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Artur Kosakowski
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