Nonlinear Lamb waves in plate/shell structures

Because the conventional linear ultrasonic testing is not suitable for the distributed minor material damage and the contact-type structure damage, nonlinear ultrasonic technique has attracted wide attention in recent years. It is well-known that ultrasonic waves propagate in plate and shell structures with Lamb wave modes. However, due to the complexity of Lamb wave propagation, the theoretical and experimental studies on nonlinear Lamb waves make progress slowly. According to the mechanism of generation, and the progresses of theoretical and experimental works about the nonlinear Lamb waves induced by the inherent material nonlinearity are summarized based on classical nonlinear theory, and the application of the second harmonic Lamb mode in damage evaluation of material is reviewed. The present research status of the nonlinear Lamb waves induced by the contacttype structure damage is also discussed based on contact acoustic nonlinearity. At last, the future research emphasis and development trend of nonlinear Lamb waves are presented and discussed.