Cobham adds modal solver to Opera-3D software

Written by: Laura Hopperton | Published:
Modal analysis only gives modes and frequencies, normally evaluated between 50 and 2000Hz in ...

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Cobham Technical Services has extended the multiphysics capabilities of its Opera-3D finite element software.

The new modal solver tool, known as STRESS/EV, can be used to analyse natural vibration modes and is said to greatly reduce the complexity and timescales of design projects.

Cobham says one of the key benefits is a further reduction in the need to create physical prototypes to explore the behaviour of a proposed design concept.

The tool works by finding a user-specified number of eigenvalues within a specified frequency range before calculating the eigenvectors of each mode.

It works in conjunction with the static stress analysis capability of Opera which calculates the deformation, stresses and strains of a body which is subject to external and internal forces.

The forces calculated from electromagnetic fields can be used as input to the stress analysis.

STRESS/EV accommodates isotropic, orthotropic and fully anisotropic materials, the properties of which can be specified as a constant or an expression.


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Comments
Modal analysis only gives modes and frequencies, normally evaluated between 50 and 2000Hz in aerospace applications. This doesn’t give stresses; the difficult task is then to drive the solved system using the dynamics module and to excite the structure, using effective mass and mode participations and effective mass @ resonances to determine which frequencies will be a problem. You may then need to stiffen your structure and re-evaluate. If you have a top end package, you can add rotational stresses, so you get mode + rotation. You should be able to apply sine or PSD or other functions, depending on your requirements and solve, but this is when it gets difficult. Once you excite your structure, you can evaluate nodal displacements with respect to input locations by function and see what your modal deformations may be. Don’t forget to apply damping because this makes a difference. Then compare your findings to real life test bed God luck to all you FEA guys ....
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