Abstract
During the last decades a great variety of methods have been proposed for damage detection by using the dynamic structure characteristics, however, most of them require modal data of the structure for the healthy state as a reference. In this paper the applicability of the mode shape curvature squares determined from only the damaged state of the structure for damage detection in a beam structure is studied. To establish the method, two aluminium beams containing different-size mill-cut damage at different locations are tested by using the experimentally measured modal data. The experimental modal frequencies and the corresponding mode shapes are obtained by using a scanning laser vibrometer with a PZT actuator. From the mode shapes, mode shape curvatures are obtained by using a central difference approximation. With the example of the beams with free-free and clamped boundary conditions, it is shown that the mode shape curvature squares can be used to detect damage in the structures. Further, the extent of a mill-cut damage is identified via modal frequencies by using a mixed numerical-experimental technique. The method is based on the minimization of the discrepancy between the numerically calculated and experimentally measured frequencies.
Highlights
Structural health monitoring and damage detection in civil, mechanical and aerospace engineering constructions has become one of the most important keys in maintaining the integrity and safety of a structure
One can see that the boundary effect has been reduced significantly and this time the largest peaks in the Mode shape curvature square magnitude (MSCSM) damage index plot are seen at the location of the damage
The present study focuses on the identification of the location,size and extent of mill-cut damage in a beam structure by extracting dynamic characteristics obtained from vibration experiments
Summary
Structural health monitoring and damage detection in civil, mechanical and aerospace engineering constructions has become one of the most important keys in maintaining the integrity and safety of a structure. During the last decades vibration-based damage detection methods have been attracting most attention due to their simplicity of implementation These methods are based on the fact that dynamic characteristics, i.e., the modal frequencies, mode shapes, and modal damping are directly related to the stiffness of the structure. The major drawback of those methods is a need for the data of the healthy structure which sometimes could be difficult to obtain or even impossible To overcome this issue Gapped Smoothing Techniques [9,10,11] were introduced which allow the damage detection in a structure without prior knowledge on the healthy state. Experimental modal frequencies and corresponding mode shapes obtained by using a scanning laser vibrometer with a PZT actuator are used for illustration of the proposed method. In addition damage extent is identified via the modal frequencies by using a mixed numerical-experimental technique
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