Identification of cracks in beams using vibrational analysis

Abstract

Cracks in structural members lead to local changes in their stiffness, flexibility and consequently their static and dynamic behaviour is affected. The influence of cracks on dynamic characteristics like natural frequencies, modes of vibration of structures has been the subject of many investigations. Present work deals with the vibration analysis of an isotropic cantilever beam made with a transverse one-edge non-propagating open crack using the finite element method. The flexibility matrix method is used to calculate the stiffness of the cracked beam here. The vibration of the cracked beam is computed in the present study and then it is compared with the previous study results. The effects of various parameters like crack location, crack depth on the changes in Natural Frequencies of the beam is studied. It is found that, presence of crack in a beam decreases the natural frequency which is more pronounced when the crack is near the fixed support than the free end and the crack depth is more. Then the inverse problem is introduced, as the detection of cracks is very difficult through naked eye and the non-destructive method of detecting cracks which are used is very much costly. Here the first three Natural Frequencies are used to detect the crack depth and location of crack in the beam.