Research On Damage Identification Method Of Lamb Wave Phased Array For Thin-walled Plate Structures

Thin-walled plate structures are an important part of industrial equipment and a key component for supporting loads.If there is damage to thin-walled plate structures,it may cause significant casualties and economic losses.Therefore,it is very important to identify the damage of thin-walled plate structures.Lamb waves have many advantages such as long propagation distance,low energy attenuation,and sensitivity to damage,making them widely used in damage identification of thinwalled plate structures.The Lamb wave-based damage imaging method evaluates structural damage by capturing changes of received response signals caused by structural damage.However,most of these methods require pre-obtaining baseline signals and are difficult to achieve multi-damage identification.The ultrasonic phased array-based structural damage identification method does not require baseline signals.However,the ultrasonic phased array method uses non-dispersive body wave and is only suitable for thickness-direction damage identification.As Lamb waves have dispersive and multi-mode characteristics,the combination of ultrasonic phased array and Lamb waves will lead to inaccurate imaging position of thin-walled plate structures.Firstly,the Lamb wave pre-dispersion compensation technology is proposed in this thesis.The proposed pre-dispersion compensation technology is based on the dispersive characteristics of Lamb wave.In this way,the dispersion effect of Lamb wave is eliminated and the phase distortion is corrected,achieving Lamb wave synthesis waveform dynamic focusing.Secondly,the Lamb wave pre-compensation focusing imaging method is also proposed combining ultrasonic phased array and Lamb wave damage imaging technology.The proposed Lamb wave precompensation focusing imaging method is suitable for damage identification of thin-walled plate structures.Thirdly,the Lamb wave-based phased array multi-mode fusion imaging method is proposed based on the multi-mode characteristics of Lamb waves.The proposed fusion imaging method is conducted on the fusion imaging of A0 mode and S0 mode imaging to solve the problem of low positioning accuracy and imaging resolution of traditional Lamb wave damage imaging method.Lastly,the numerical simulations and experiments of single-damage and multi-damage concerning surface damage and through-hole damage on aluminum plates are carried out.The numerical and experimental results show that the proposed Lamb wave-based phased array multi-mode fusion imaging method achieves single-damage and multi-damage identification of thin-walled plate structure without requiring baseline signals.Above all,the proposed multi-mode fusion imaging method can effectively improve the positioning accuracy and imaging resolution and avoid artifacts.The maximum positioning error for multi-damage identification is only 3.3%.The Lamb wave-based phased array multi-mode fusion imaging method proposed in this thesis is expected to provide an effective way for multi-damage identification of large thinwalled plate structures such as aerospace,pressure vessels,and hulls.