The presence of a crack causes a local variation of stiffness and affects the mechanical behaviour of the entire structure. Reduction in the stiffness reduces the natural frequencies and affects the mode shapes. In the present work, effect of crack depth and its location in beams is studied. Three different boundary conditions, namely cantilever, simply supported and fixed are considered. Natural frequencies for first three flexural mode shapes are obtained for different crack depths and locations using modal analysis on ANSYS-13. Effect of crack on top and bottom faces of the beams has also been studied. Crack depth and its relative position have got major effects on dynamic behaviour of the beam with different boundary conditions. The effect of cracks is significant when the cracks are near to the fixed end than free end. The natural frequency is observed to be reduced with increase in relative crack depth.

Keywords: Free vibration, Crack, Natural frequencies, Beams.