High-resolution damage imaging for composite plate structures based on virtual time reversal

According to the problems that traditional time reversal (TR) method eliminates propagation time of Lamb waves and its procedure is complicated, a virtual time reversal (VTR) method is presented. In the method, changing-element exciting and receiving mechanism is adopted to reserve time information and the TR procedure is replaced by the signal operations. The realization involving acquiring transfer functions of damage detecting path under step pulse excitation is discussed. A high-resolution damage imaging method based on VTR is developed. To reduce the anisotropic effect in composite plates, velocity correction is carried out during the imaging. The experimental results show that damage scattered wavepackets of Lamb waves in the carbon fiber composite plate can be partly recompressed and time reversal focused by VTR. Both the signal damage and dual adjacent ones in the plate are clearly displayed by the proposed imaging method.