Theoretical and Experimental Study of the Dynamic Behavior of a Double-Cracked Beam

In recent years a significant amount of effort has been devoted to the development of nondestructive testing techniques for damage detection in structures. It is wellknown that the dynamic response of a structure changes when it is subject to damage. Given a relationship between the dynamic property changes and the damage, measurement of the changes can be used as a diagnostic tool. When the damage of a structure is due to the presence of cracks, the measurement of t,he changes can be used to detect and quantify the extent of the damage. Previous research has revealed that both the location and quantification of damage is possible when a single crack is present. If the structure is cracked in at least two places, the identification problem becomes decidedly more complex. In fact, for two cracks, the solution depends on four wriiables, the position and the size of each crack. The aim of this paper is to validate two analytical models of a cantilever beam with two cracks using experimental data obtained from a real structure and to perform a systematic study of the analysis and experimentation by correlating the crack location, the crack size and the corresponding changes in modal parameters.