An Experimental Study of the Modal Parameters of a Damaged Cantilever

The introduction of a crack in a structure will cause a local change in stiffness and damping capacity. The local change in stiffness, normally a decrease, will lead to a change of natural frequencies of the structure and a discontinuity in the mode shapes. This report contains a presentation of results from experimental tests with six hollow section steel cantilevers containing a fatigue crack introduced from a narrow laser cut slot. The modal parameters have been identified for different size and location of a crack. The modal parameters have been estimated by mean of frequency domain and time domain system identification techniques. A short description of these system identification methods is given