Experimental Investigation of Crack Detection in Cantilever Beam Using Natural Frequency as Basic Criterion

Crack changes the dynamic behaviour of the structure and by examining this change, crack size and position can be identified. Non destructive testing (NDT) methods are used for detection of crack which are very costly and time consuming. Currently research has focused on using modal parameters like natural frequency, mode shape and damping. to detect crack in beams. In this paper a method for detection of open transverse crack in a slender Euler-Bernoulli beam is presented. Experimental Modal Analysis (EMA) was performed on cracked beams and a healthy beam. The first three natural frequencies were considered as basic criterion for crack detection. To locate the crack, 3D graphs of the normalized frequency in terms of the crack depth and location are plotted. The intersection of these three contours gives crack location and crack depth. Out of several case studies conducted the results of one of the case study is presented to demonstrate the applicability and efficiency of the method suggested. Index Terms — Crack, Euler-Bernoulli, mode shape, natural frequency.