Effects of crack on modal frequency of cantilever beam

Finite Element Method is used to determine the natural frequency of beam whereas the experimentation is performed using Fast Fourier Transform analyser. In experimentation, cantilever beam with crack are considered. The experimental results are validated with the results of FEM software. This formulation can be extended for various boundary conditions as well as varying cross sectional areas. A crack in a structural member introduces local flexibility that would affect vibration response of the structure. i.e., a crack causes a reduction in the stiffness and an increase in the damping of the structure. These changes of physical properties cause a reduction in the natural frequencies and a deviation in the mode shape. Therefore it is possible to predict the crack depth and crack location by measuring changes in the vibration parameters. Changes in the natural frequencies are more often considered than deviation of mode shapes, since frequencies can be measured more easily than mode shapes, and they are less seriously affected by experimental errors. This property may be used to detect existence of a crack together with its location and depth in the structural member. In this analysis the natural frequencies obtained from experimental analysis and finite element analysis are used to obtain the crack location and crack depth.