Abstract
This paper presents a methodology to detect, locate and assess cracks in structures using frequency measurements and energy formulation of the vibration theory. Cracks are modelled as a mass-less, infinitesimal, rotational springs with a much smaller stiffness than that of the undamaged structure. The variation in the natural frequency of the defective structure from that of the undamaged structure in each mode is dependent on the size as well as the location of the crack. The location and the severity of the crack are identified by triangulation from changes in natural frequencies in different modes caused by the defect. The proposed methodology is validated by Experimental Modal Analysis (EMA) of a cantilever beam with through thickness cracks of various sizes located at different positions along the length of the beam. Good agreement is obtained in all cases.
