Variable loadings cause fatigue to the structural elements leading to crack initiation and propagation, which results in a decrease in the fatigue life of the elements. In particular, cracks decrease the stiffness and the natural frequency thus, causing specimens to fail under normal working conditions. This paper presents the application of the vibration- based technique for detecting the location and the size of a fatigue crack in structures. The two presented methods are based on the measurements of the natural frequencies of the cracked beam. The crack is modelled by a rotational spring. The predicted crack depth and location are compared with the actual data obtained from finite element models.
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