Journals / SV / Vol.55, No.2

Research Article


Experimental Modal Damping Identification of a Mechanical Structure Using Video Magnification Technique

Jaafar Hallal1,*, Mahmoud Fakih2, Hala Damerji3, Mohammad Hammoud4,5, Mehdi Chouman4,5
1 Mechanical Engineering Department, Faculty of Engineering, Lebanese University, Beirut, Lebanon
2 Civil Engineering Department, Faculty of Engineering, Lebanese University, Beirut, Lebanon
3 Universite Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
4 SDM Research Group, Mechanical Engineering department, International University of Beirut, Beirut, Lebanon
5 Mechanical Engineering department, Lebanese International University, Bekaa, Lebanon
* Corresponding Author: Jaafar Hallal. Email:


Vibration can be introduced in all mechanical fields in our life. Engineers try to avoid its negative effect leading in some cases to deformation in the machines. Many researches are dedicated to study the identification of damping especially in multi degree of freedom systems with particular attention to the source of energy dissipation. They focus on developing new tools or methods which may be used in real problems to obtain accurate results about the amount (or value) and the location of energy dissipation in the structure. The aim of this paper is to present an original procedure aims to experimentally determine the modal damping ratio of a mechanical structure. The proposed procedure consists of extracting the Frequency Response Function of the vibrating system using the video magnification method and then calculate the modal damping ratio using the 3-dB method. These experimental measurements are carried out by giving an external force on a cantilever beam, then the modal damping ratios are extracted using motion magnification. The obtained results show a relative error less than 4.2% between the experimental measurements and the analytical calculation for the Frequency Response Function (FRF) curves. The novelty of the paper is to combine the video magnification technique and the 3dB method in a procedure that aims to experimentally measure the modal damping of a mechanical structure. The proposed procedure in this paper represents the damping identification as a simple and easy engineering application.


Vibrations; modal damping; experimental measurement; video magnification
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