How to import a Frequency Response Function (FRF) in MANATEE?

Starting from version 1.06.02, it is possible to import a standard structural Frequency Response Function (FRF) to be used in MANATEE. The FRF represents the displacement of the structure under some elementary magnetic forces, for instance tangential and radial rotating force waves of 1N.

The input parameters are in the project file:

Input.Simu.type_FRF
Input.Simu.type_loadFRF
Input.Simu.pathname_FRF

First, you need to set Input.Simy.type_FRF = 1 to choose the Electromagnetic Vibration Synthesis (EVS) type as a rotating force wave excitation. Then, by setting type_loadFRF = 2, MANATEE skips the structural computations and directly loads your data. The data need to be stored in an Excel file. The path to the Excel file is set in Input.Simu.pathname_FRF (if the absolute path is not used the folder should be part of your Matlab path).

Each sheet of the excel file corresponds to a specific unit-magnitude electromagnetic excitation. The sheets are named according these excitations. The first character is a "r" or a "t" for radial or tangential followed by the wavenumber. For instance, "r+10" corresponds to a radial excitation of wavenumber r=10 and "t-2" to a tangential excitation of wavenumber r=-2.

The content of each sheet follows the same template:

  • The first column is the frequencies at which the FRF is computed [Hz]
  • The second one is the real part of the quadratic average displacement [m] over all external surface under a 1 N/m^2 excitation
  • The third one is the imaginary part of the quadratic average displacement [m] over all external surface under a 1 N/m^2 excitation

Import FRF from a .mat file

By setting Input.Simu.type_loadFRF = 1, you can also provide the FRF data in a .mat file. This file needs to contain three variables:

  • orders_circ_FRF: list of the circumferential wavenumbers (integer array)
  • FRF_rad: a cell array containing matrices (first column: frequency, second column: complex quadratic average displacement over all external surfaces under a unit pressure wave of 1 N/m^2) for radial excitation
  • FRF_tan: a cell array containing matrices (first column: frequency, second column: complex quadratic average displacement over all external surfaces under a unit pressure wave of 1 N/m^2) for tangential excitation

The matrices in the cell arrays are in the same order as orders_circ_FRF. Note that MANATEE generates this kind of .mat file when Input.Simu.type_loadFRF=1.

Convert the data from OptiStruct to be imported

MANATEE also includes a tool to convert OptiStruct .frf files to match these constraints:

convert_Optistruct_FRF(frf_path, r, is_rad,file_type);

The parameters of this function are:

  • frf_path: Path to the folder containing all the .frf files
  • r: wavenumber list (to set the correct sheet names)
  • is_rad: 1 for radial, 0 for tangential (to set the correct sheet names)
  • file_type: 0 convert to Excel, 1 convert to .mat, 2 convert to both
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