Detecting damage in rods and beams from natural frequency and antiresonant frequency measurements

A reconstruction method for damage identification in vibrating beams is proposed in this paper. It is shown that natural frequency and antiresonant frequency shifts induced by a damage contain information on generalized Fourier coefficients of the stiffness variation caused by the damage. A numerical procedure based on this property is suggested to solve the inverse problem. Applications on steel beams with localized damages, either under axial or bending vibration, are discussed. Numerical results are in good agreement with the theory, provided that average frequency and antiresonant frequency shifts are bigger than modeling/measurement errors.