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Damage Detection in Flux Cored Wire Welded Structures by Using Vibration Testing

In welded structures subjected to dynamic cyclic loads may appear and propagate fatigue cracks due to local structural damage. These cracks may initiate due to technological damages induced by welding process, or by environmental operating conditions. In the present work, it is determined, by the means of Finite Element Method (FEM), the natural frequencies and mode shapes of more steel specimens that are welded together. The analysis is carried out in undamaged condition as well as in damaged one, after the damage has been artificially induced. The experimental measurement of the vibration response is carried out by using a condenser semi-professional microphone Samson C01U, which is suitable for high-fidelity acoustic measurements in the frequency range of 40 18.000 Hz. A first post-processing of the vibration responses of the welded specimens, in free-free conditions, is carried out using an algorithm based on Prony series. A second post-processing is carried out by means of signal processing using DWT together with Shannon entropy. The results are compared to modal parameters estimated using FE Analysis.