Crack detection from the variation of the eigenfrequencies of a beam on elastic foundation

A crack in a structural member can change the eigenfrequencies of the undamaged structure. The magnitude of change in the eigenfrequencies is a function of the severity and the location of the crack. In this paper, crack-induced changes in eigenfrequencies of a beam on elastic foundation are studied. A perturbation method is used to evaluate the first order perturbation of the eigenfrequencies. The local flexibility, introduced by the crack in the cracked section, is represented by a massless rotational spring, whose stiffness depends on the severity of the crack. Some graphics illustrate the procedure for identifying both the position and the severity of the crack.