Experimental verification of a vibration based damage detection technique

A system of continuous monitoring would be desirable for early warning of distress in major engineering structures, particularly in long-duration space structures. However, the complexity of large structures and the difficulty in accessing them makes the use of traditional non-destructive evaluation, such as visual inspection and instrumental evaluation methods, impractical. An effective alternative is the use of methods that depend on vibration-based damage identification. These methods are based on measurement of changes in the modal characteristics of the structure, that is, its frequencies and mode shapes, to identify changes in its physical properties. However, vibration based damage detection still faces a number of challenges that have not been fully resolved. Some of these challenges are highlighted through modal tests designed to provide estimates of damage in a 3D eight-bay free-free frame. The construction of a finite element model of the structure and its correlation with measured test data are described. Details of tests on a healthy structure as well as on a structure in which predetermined damage has been introduced are presented. A technique of predicting damage on the basis of modal test data is described and the predictions are compared with the known damage. Some methods of improving the reliability of damage detection are discussed.