Frequency-Dependent Undamped Free-Vibration Solver (B2000++ Pro)

The frequency-dependent undamped vibration solver allows for solving frequency-dependent free vibration eigenvalue problems to determine eigenfrequencies and eigenmodes, where the linear internal forces and internal inertia are frequency-dependent. It is invoked by the MDL command analysis frequency_dependent_free_vibration; this command must be specified in the case block.

[Note] Note

When executing B2000++, errors of the following kind

CRITICAL:all:16:22:8.124: Uncovered b2000 exception caught in the main function.
Exception: Error with the arpack subroutine aupd, info = -9.

are often indicative of missing density specifications in the material definitions.

[Note] Note

When executing B2000++, warnings of the following kind

WARNING:solver.eigenvalue.arpack:12:36:35.234: Maximum number of iterations taken.
All possible eigenvalues (0) have been found.

are indicative that the value for the nmodes option should be increased.

1. MDL Commands

In addition to the MDL command analysis frequency_dependent_free_vibration, the following commands may be specified in the case block.

nmodes v

Number of free-vibration modes v to be computed (default: 1). It is often necessary to set this option to values of 10 or even 20 for the successful solution of the eigenvalue problem.

shift v

The spectral frequency shift value. The computed free-vibration modes are the ones whose eigen-frequencies are near this value (default=0). For complex problems, a complex spectral frequency shift value can be provided.

freq_init v

The initial frequency used in the first stage of the algorithm.

tol v

The relative tolerance of the computation of the exact eigenfrequency.

tol_predictor v

The relative tolerance for the re-computation of the approximated eigenfrequencies.