Saeidreza Mohebpour

In this paper, a multi-cracks detection method, which is based on natural frequency changes and the concept of modal strain energy, is for the first time developed for the general cross-section swept tapered wings under coupled bending-torsional vibration (CBTV) and applied to the solid and thin-walled airfoil cross-section wings. The presented method is able to handle the problems with an unknown number of cracks, and predicts the number of existent cracks, their locations and depths by optimization of an appropriate objective function. The stress intensity factors (SIFs) of airfoil-shaped crack surfaces are obtained using an approximation method. Inputs of the detection method are natural frequencies of uncracked and cracked wings which are calculated by using a mathematical model and FEM software ANSYS, respectively and validated by comparison to former researches. In the mathematical model, the Rayleigh-Ritz method is employed to calculate the coupled bending-torsional mode shapes of uncracked wing and their corresponding natural frequencies. Results demonstrate that the proposed method has precisely predicted the number, locations and depths of cracks in all case studies.