Learn About Vibrations!

Learn About Vibrations!

Welcome!

The ABRAVIBE blog is where you find all the resources for learning more about vibrations. Browse and download examples for the free MATLAB/Octave ABRAVIBE toolbox. Or browse the many theory examples, videos, and resources for the book "Noise and Vibration Analysis: Signal Analysis and Experimental Procedures," by Anders Brandt!

Finite Element Verification and Calibration Example

ABRAVIBE ExamplesPosted by Anders Brandt Nov 12, 2013 19:18
This is a complete example of finite element model verification and calibration (sometimes known as correlation).

The example uses a finite element model built in the free CALFEM toolbox and experimental modal analysis results of the Plexiglas plate used throughout ABRAVIBE as an example structure. The idea of this example is to be simple and illustrative, so that the techniques are not hidden by practical difficulties. The example includes verification of mode shapes using the MAC matrix and frequency tables, and calibration by adjusting the Young's modulus to adjust the first bending mode of the FE model to fit the experimental data. In the Bibliography Section on this site there is a technical paper describing the example.


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Modal Analysis Example and Bug Fix

ABRAVIBE ExamplesPosted by Anders Brandt Jun 09, 2013 18:28
A new modal analysis example is available! This example compares the three currently available options to the frf2ptime command; 'prony', 'lsce', and 'ptd'. It can serve as a reference for how to use these three options.
The example also includes a bug fix to the frf2ptime.m file, to make this command work for the Prony option.

The example uses the same synthetic data for the Plexiglass plate that the Plexi Modal Example uses, but comes with the data to make it independent of the previous example.

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Modal Analysis Example and Important Upgrade for Modal Parameter Extraction

ABRAVIBE ExamplesPosted by Anders Brandt Mar 09, 2013 15:48
The ABRAVIBE example PlexiModal is an example of using the ABRAVIBE
toolbox to do experimental modal analysis of a Plexiglass plate using measured data.

The example uses data measured using impact testing, and the
polyreference time domain (PTD) method with two references, to be able to
estimate the first two modes which are strongly coupled on this plate.
The example shows all involved steps such as importing and sorting data,
curve-fitting for poles and mode shapes, and evaluating the results with
a MAC matrix and animation of the modes.

This example is good to use as a template for all modal analysis tasks
with the ABRAVIBE toolbox; just replace the data imported, and the
geometry created before animation, to use the script for your modal
analysis tasks!

In addition to this, the example includes an upgrade to the ABRAVIBE toolbox revision 1.2, with a new command enhancefrf which uses singular value decomposition to reduce the measured FRFs into a smaller number of principal responses to use for the modal parameter extraction. Also the command frf2ptime is updated to use FRF enhancement by default. These two functions will be included in the next release of the ABRAVIBE toolbox. The theory of FRF enhancement is covered in chapter 15 in the book "Noise and Vibration Analysis".

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Plexiplate Operating Deflection Shape (ODS) Example

ABRAVIBE ExamplesPosted by Anders Brandt Mar 04, 2013 18:52
The ABRAVIBE example PlexiODS is an example using synthesized data
generated from a modal model of a Plexiglass plate (incidentally, by the
example called ForcedResponse) to illustrate operating deflection shapes
(ODS) analysis in ABRAVIBE. This is an advanced example including
multiple-reference ODS to be able to separate two close modes! The
example is divided into two parts, the first a single-reference technique
and the second an extended multi-reference technique.

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Forced Response Simulation Example

ABRAVIBE ExamplesPosted by Anders Brandt Mar 04, 2013 18:49
The ABRAVIBE example ForcedResponse is illustrating the power of the digital
filter forced response method for computing forced response developed by
Kjell Ahlin and published in, among other references, "Noise and
Vibration Analysis: Signal Analysis and Experimental Procedures," by
Anders Brandt. The method uses a modal superposition formulation using
a ramp invariant transform to formulate the forced response of each mode.
Also see inside the ABRAVIBE command timefresp for references to original
papers.

The example produces time data simulating a measurement of 35
displacement responses on a Plexiglass plate, when it is excited with
four forces in the corners of the plate. Mode shapes and eigenfrequencies
from a finite element model are used as a model for the plate.

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Universal File Import/Export Example

ABRAVIBE ExamplesPosted by Anders Brandt Mar 04, 2013 18:47
The ABRAVIBE example UNVExamples contains a number of example MATLAB scripts illustrating the import and export capabilities of the ABRAVIBE toolbox. It contains three examples of reading universal files, and two examples of writing universal files. Test data as well as modal data are used both for
reading and writing.

The following examples are included:
ReadUnvEx1.m Read a universal file with test data into ABRAVIBE files
ReadUnvEx2.m Read a universal file with mode shape data into ABRAVIBE files
ReadUnvEx3.m Convert ABRAVIBE modal files into a structured file for animate
WriteUnvEx1.m Write a universal file with test data
WriteUnvEx2.m Write a universal file with modal data

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Have you missed the chapter examples supplied with the ABRAVIBE toolbox?

ABRAVIBE ExamplesPosted by Anders Brandt Feb 26, 2013 19:44
We have noticed from some support questions, that some ABRAVIBE toolbox users seem to have missed the wealth of examples supplied with the ABRAVIBE toolbox. To ensure you are not one of those, I would like to make clear that after installing the ABRAVIBE toolbox (i.e. unzipping the content to a directory of your choice), there will be a directory called ChapterExamples. Usually this will be located in the Abravibe_Toolbox directory which you unzipped, unless you altered it during unzipping.

The ChapterExamples inlcudes a subdirectory for each chapter (2 to 16) of the book "Noise and Vibration Analysis", in which are located a large number of examples of various ABRAVIBE applications of the theory covered by that chapter. If you are not a proud owner of the book, you should not fool yourself by not browsing through these subdirectories! Regardless of whether you have the book or not, these subdirectories includes examples of many common tasks you may want to use the ABRAVIBE toolbox for, so they will help you get quickly started using the toolbox!

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