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!

Problems registering? Other Problems? Let us know!

DiscussionPosted by Anders Brandt Mar 17, 2013 17:36
Today I'd like to mention a couple things of administrative nature.

First of all - thanks to all of you who use this site! In the first three weeks the ABRAVIBE toolbox alone has been downloaded almost 500 times! We are very grateful for your support!

We have noticed that some users register but never activate their account. This could be because the registration email end up in your spam folder. We do mention this in the text during the registration process, but if you have missed it - take a look for the registration email in your spam folder.

Another thing is feedback. If you have trouble registering, or downloading, we really want to hear about it! Use our contact form here, to notify of what is going wrong.

You can also use the social media to share your thoughts about us! Or why not suggest an idea for what you would like to see as a vibration example.

Be sure to share us with your friends on Facebook and LinkedIn if you like us!

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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".

If you are signed in you can download the file by clicking here. Otherwise, please sign in and browse the resources at the main site.

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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.

If you are signed in you can download the file by clicking here. Otherwise, please sign in and browse the resources at the main site.

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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.

If you are signed in you can download the file by clicking here. Otherwise, please sign in and browse the resources at the main site.

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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

If you are signed in you can download the zip file by clicking here. Otherwise, please sign in and browse the resources at the main site.

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Theory problem: forced response of SDOF system to half-sine excitation by Laplace transform

Theory ExamplesPosted by Anders Brandt Mar 03, 2013 15:40
This is an example of using the Laplace transform to solve the forced response of a mechanical system. In this example the system is excited by a half-sine pulse, which is common in, for example, vibration testing. The supplied zip file contains a pdf file with the problem definition, and a separate zip file with a suggested solution. Like the harmonic SDOF forced response example, the present example is also an example I let all my mechanical vibration students solve. You can download the example either by signing in and browse the resources, or by clicking here.

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Theory problem: forced response of SDOF system to harmonic excitation by Laplace transform

Theory ExamplesPosted by Anders Brandt Feb 26, 2013 20:21
This an example of using the Laplace transform to solve the forced response of a mechanical system. It is also an illustration of the so-called beating phenomenon that can occur if a dynamic system is suddenly exposed to a harmonic excitation close to a natural frequency of the system. As illustrated by this example, the beating phenomenon occurs is more pronounced when damping is low. The supplied zip file contains a pdf file with the problem definition, and a separate zip file with a suggested solution. I run this example with all my mechanical vibration students, since it is a good example of how to use the Laplace transform to solve forced response. It is, of course, also an important demonstration example to run for different system damping and excitation frequencies, to learn the concept of beating and to understand the harmonic response of a SDOF system. Download the file by signing in and selecting it on the download page. Or, if you are signed-in already, click on the link in the text above!



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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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Start-up problems are solved!

DiscussionPosted by Anders Brandt Feb 22, 2013 18:03
Dear visitor,

The start-up problems we had for some visitors on slow Internet connections causing downloads to sometimes time out before they were finished, now seem to be solved. If you are encountering any problems downloading from this site, do not hesitate to contact us through the contact form!

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Download book resources!

Book ResourcesPosted by Anders Brandt Feb 20, 2013 22:53
If you are a proud owner of the book "Noise and Vibration Analysis: Signal Analysis and Experimental Procedures," by Anders Brandt, or have access to a library copy, you can now download some useful resources for the book:

The current errata list can be found here. Make sure you download it and make corrections in your copy of the book!

There is a zip archive with all book figures in separate PowerPoint files for each chapter. You can use these PowerPoint files to, more conveniently, make your own lecture presentations. The reason I have chosen to do it like this, rather than to provide complete presentations, is that I personally find it hard to use other peopleĀ“s slides. If you would like me to provide complete PowerPoint files, please send me an email through the contact template, indicating this. If there is enough interest, I will consider providing such presentations later. Download this zip archive by clicking here.

Finally there is a solutions manual for all the Problems in the book! The ZIP file includes a PDF file in a printer-friendly form, approx. 67 pages, and a file where each solution starts on a new page, suitable if you are a teacher and you wish to hand out only a single solution to your students. A directory with MATLAB scripts for all relevant Problems is also included. Download it by clicking here.

You can also go to www.abravibe.com and sign in. When you are signed in you can browse and select among all files to download!

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