New method for structural health monitoring and failure
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Lightweight structures such as wind turbines and aircraft are exposed to high dynamic loads during operation. Due to these operating conditions and their low mass, they vibrate. This is comparable to musical instruments, which produce sounds due to induced vibrations.
The vibrations of structures are characterised by the dynamic parameters and change during operation. Musical instruments change the sound they produce after they have been used. A musician detects such a change in operating conditions with his or her hearing and tunes the instrument (maintenance). In structures, which are usually complex, such monitoring is not possible; instead, the dynamic parameters are monitored. One of the dynamic parameters is structural damping, which characterises the dissipation of vibration energy in structures. If there were no damping, a guitar would never stop sounding after a string pluck. Damping in structures is caused by various sources, such as internal friction in the material, the environment in which the structure vibrates (water, air, space), joints, etc. It is very difficult to model each of these sources as they all occur simultaneously. Therefore, for simplicity, it is characterised by a single parameter called the damping ratio.
The process of identifying dynamic parameters is called modal identification. The first step in this process is to measure the structural response and then identify the modal parameters using a signal processing method. Structural responses are usually measured using accelerometers. However, these must be attached to the structure and a large number of sensors is impractical. A large number of measurement points is required to identify local structural changes in the vibration motion and can be used to improve the identification of modal parameters. Today's developments in high-speed cameras make it possible to obtain a structural response from a high-speed video recording. To meet the challenges of the new measurement techniques, a new signal processing method is required. In addition, damping in structures is a challenge for identification due to their nature.
In the published article, an advanced signal processing method was used to identify structural damping from high-speed video recordings with similar accuracy to the accelerometer. Structural responses obtained from high-speed video recordings are subject to noise, and current methods for identification are problematic. The method developed in this research can identify damping from such responses. Since the measured response has a very high spatial density, this is used to improve the identification results.
This achievement paves the way for non-contact remote measurement of structural vibration and enables relatively fast monitoring of the condition of structures.
Authors: Dr. Ivan Tomac, Prof.dr. Janko Slavi膷
Article: I. Tomac, J. Slavi膷, Damping identification based on a high-speed camera, Mechanical Systems and Signal Processing, Volume 166, 1 March 2022, 108485, DOI:
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