INTERNATIONAL JOURNAL OF RESEARCH IN AERONAUTICAL AND MECHANICAL ENGINEERING ISSN (ONLINE): 2321-3051 Vol.3 Issue 8, August 2015 Pgs: 24-38 Swapnil Dokhe, Shailesh Pimpale 24 EFFECTS OF CRACK ON MODAL FREQUENCY OF CANTILEVER BEAM Swapnil Dokhe 1 , Shailesh Pimpale 2 1 Post Graduate Student, JSPM’S Rajashri Shahu College of Engineering, Tathawade, Pune-411033, Maharashtra, India, swapnildokhe@gmail.com, +919766675955 2 Professor, JSPM’S Rajashri Shahu College of Engineering, Tathawade, Pune-411033, Maharashtra, India, shailesh_pimpale@rediffmail.com, +919822457938 Abstract 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. Keywords: Crack, FEM, FFT, Modal Analysis, Natural Frequency. 1. Introduction Many structural applications worldwide have been in use form many years. Their failure could lead to tragic consequences and therefore structures have regular costly inspections. During the last decades vibration based damage detection methods have attracted the most attention due to their simplicity for implementation. The presence of crack in structure changes its dynamic characteristics [2]. The change is characterized by change in modal parameters like modal frequencies, modal value and mode shapes associated with each modal frequency [13]. It also alters the structural parameters like mass, damping matrix, stiffness matrix and flexibility matrix of