Free vibration and damage identification of cracked functionally graded plates

This paper investigates the free vibration and crack identification of functionally graded material (FGM) plates with a through-width edge crack. The material properties of the FGM plates change continuously with the power law distribution along the plate thickness direction. The crack in an FGM plate is simulated as a massless rotational spring and the plate is separated into two sub-plates at the crack location connected by the line spring. The stress intensity factor (SIF) in the FGM strip is calculated to determine the stiffness of the spring. The governing equations of cracked FGM plates are derived from the Mindlin plate theory and solved by the differential quadrature (DQ) method to obtain modal parameters. The vibrational mode of a cracked FGM plate is analyzed by utilizing continuous wavelet transform (CWT). A novel damage index (DI) is developed based on calculated wavelet coefficients to localize the crack in FGM plates. This method can localize the crack accurately and reduce the edge effect even with the measurement noise.