Hi.

I would like to solve Frequency Response Analysis by my own code.

Is it possible to get stiffness and mass matrix from karamba model?

Hi.

I would like to solve Frequency Response Analysis by my own code.

Is it possible to get stiffness and mass matrix from karamba model?

Hi @R.omae,

yes it is possible via a C# script. See GitHub - karamba3d/K3D_tests: Unit tests for the Finite Element Toolkit Karamba3D, Algorithms/NaturalVibes_tests.cs for general examples.

You can use the following method:

/// —

/// Calculate the structures natural frequencies and mode shapes.

/// —

/// “in_model”: Model to be analyzed.

/// “from_shape_ind”: index of first natural vibration mode to be calculated. Numbering starts from one.

/// “shapes_num”: number of modes to be calculated.

/// “max_iter”: maximum number of vector iterations in the Mises procedure.

/// “eps”: convergence criteria for determining the eigenvalues.

/// “disp”: displacement pattern for calculating participation factors.

/// “scaling”: type of scaling applied to the mode shapes.

/// “nat_frequencies”: frequencies of the natural vibration mode in Hz.

/// “modal_masses”: modal mass of the corresponding natural vibration mode.

/// “lumped_masses”: vectors of lumped masses of each node.

/// “participation_facs”: participation-factor in global x-, y- and z-direction.

/// “participation_facs_disp”: participation-factors with respect to displacement pattern.

/// “out_model”: model with vibration modes as load-case results.

/// returns: Calculated model.

public virtual Model NaturalVibes(

Model in_model,

int from_shape_ind,

int shapes_num,

int max_iter,

double eps,

List<double> disp,

EigenShapesScalingType scaling,

out List<double> nat_frequencies,

out List<double> modal_masses,

out List<Vector3> lumped_masses,

out List<Vector3> participation_facs,

out List<double> participation_facs_disp,

out Model out_model)

This method resides in Karamba.Factories.FactoryAlgorithms of KarambaCommon.dll.

– Clemens

Thank you for your reply!

I have additional question.

Do you mean that I can solve natural vibration by “Model NaturalVibes” method, or I can get mass and stiffness matrix via “Model NaturalVibes” method?

If later is right, would you please tell me more detail how to get them ?

Thank you.

With the above method you can solve the model for the natural vibration modes and get out the lumped masses at the nodes.

– Clemens

Ok, I’ve got the point. I’ll try it.

I really appreciate your answer.

Hi,

I would like to get the stiffness matrix for analysing its eigenvalues. Is there any solution for extracting this matrix from the model ?

Martin

Hi @martin.steinmetz,

at the moment it is not possible to get out the stiffness matrix. I could add a corresponding method to the API.

– Clemens

It woudl be helpfull

Thanks for your help,

Martin