Research On Damage Identification Technology Of Complex Structures Based On Guided Wave

In order to meet the needs of aeronautics and aerospace applications in the future,variable thickness and curvature structural elements have become an essential part of the structure,such as wings,tails and rotors.These complex structural parts are subject to external factors in the process of manufacture and use,and are prone to defects.Therefore,nondestructive testing of complex structures has become an important research direction.Laser ultrasonic nondestructive testing technology can excite guided waves in the structure without contact.Combined with the corresponding nondestructive testing algorithm,it can realize the imaging of the collected data to achieve the purpose of damage identification.Based on the laser ultrasonic nondestructive testing system,the experiment of complex structures has been completed.A new algorithm and a quantitative criterion for damage identification have been put forward,and the visualization of various kinds of damage has been realized.Firstly,based on the basic principle of laser ultrasound,the process of ultrasonic wave in laserexcited materials is introduced,and the excitation mode suitable for nondestructive testing is obtained.The formation process,basic concepts and dispersion characteristics of guided waves are also analyzed,which provides theoretical support for the subsequent experiments and the improvement of the algorithm.Then,the signal processing method of ultrasonic guided wave is studied.After separating incident and reflected waves,the time domain integral energy method and interference energy method are compared for damage identification.An energy-based wavenumber estimation method and a compensation method for time-domain amplitude attenuation are proposed to improve the imaging effect of damage.In order to quantitatively study the effect of damage identification,a damage identification factor is introduced,and the results of all methods are verified.Finally,the characteristics of ultrasonic guided waves for several typical composite structures with complex shapes are explored and compared with theoretical analysis.The most suitable experimental method and identification algorithm are proposed.Based on this,the visualization of damage in complex structures is studied and the damage detection in structures is successfully completed.