DETECTION OF THE LOCATION AND SIZE OF A CRACK IN STEPPED CANTILEVER BEAMS BASED ON MEASUREMENTS OF NATURAL FREQUENCIES

A method based on measurement of natural frequencies is presented for detection of the location and size of a crack in a stepped cantilever beam. The crack is represented as a rotational spring, and the method involves obtaining plots of its stiffness with crack location for any three natural modes through the characteristic equation. The point of intersection of the three curves gives the crack location. The crack size is then computed using the standard relation between stiffness and crack size. An example to demonstrate the usefulness and accuracy of the method is presented.