Dynamic analysis of beams with breathing crack using finite element method

Özkan, Berkay
Non-linear dynamic characteristics of a beam with a breathing crack are investigated using finite element method. This thesis has two main objectives: (1) to obtain a foresight for the vibration based crack detection by using finite element method (2) to investigate the effects of crack location, crack depth, excitation frequency, excitation amplitude and boundary conditions on the indications of crack presence. Two dimensional finite element approach is used to model a square cross sectional beam subjected to dynamic loading. Frictionless contact is introduced to avoid any penetration between the crack faces. Time histories and Fourier spectra are obtained for nodal acceleration at specified sensor locations on the beam. On the basis of the results of this research, the capability of finite element method on the crack detection is evidenced by the generation of sub- and higher-harmonics in the Fourier spectra. Both time and frequency domain responses deviate considerably from vibration response of an intact beam. The depth and position of the crack change the amplitude of the harmonics, which can be interpreted as an indicator on the severity of the damage. Furthermore, exciting the beam with frequency of first natural mode of the beam, makes the harmonics more detectable on the frequency domain.  


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Citation Formats
B. Özkan, “Dynamic analysis of beams with breathing crack using finite element method,” M.S. - Master of Science, Middle East Technical University, 2017.