Damage detection in rods by means of the wavelet analysis of vibrations: Influence of the mode order

This communication deals with the detection of damage in rods using free axial vibrations. A density and a stiffness reduction were considered as local defects. The displacement along the damaged rod at a fixed time was the signal used to assess the presence and location of defects through wavelet transform. A study of the influence of the mode order on damage detection is presented. We demonstrate that detection quality for a particular mode depends on the combination of two factors: the order of the mode and the location of the defect. As for the first factor, the higher the order of mode, the better the detection for both kinds of defects. The second factor depends on the kind of defect; if it affects density, its closeness to an antinode of displacement favors its detection. However, if it affects stiffness, the closeness to a node of displacement (antinode of the stress) improves its detection.