Ultrasonic guided wave damage localization method for composite fan blades based on damage-scattered wave difference

Abstract

Abstract Ultrasonic guided wave (UGW) has a wide monitoring range and high accuracy, holding promise for monitoring damage in engine large-area composite fan blades. However, the multi-curvature characteristics of engine composite fan blades with their anisotropic material properties make damage localization impossible with conventional UGW monitoring methods. In order to realize the UGW damage monitoring of the blade, this paper proposes a damage localization method based on damage-scattered wave difference. The method utilizes irregular sensing arrays to achieve localization of damage in multi-curvature composite blades with a small amount of data. First, the difference between the mutual excitation in a pair of sensors and the damage-scattered waves captured at reception was analyzed. It is concluded that the closer the damage is to the received sensor, the greater the damage index (DI). Next, a DI ratio of the mutually excited and received signals is computed for each sensor pair. This ratio is utilized to make a vertical line on the propagation path, which is identified as the damage likelihood line (DLL). Finally, a DLL corresponding to the three largest DIs was selected, and their intersections were used for damage localization. A time-domain truncated signal processing method is proposed to enable DI to more accurately represent the effects of damage, and improve the localization accuracy of the method. An experiment on damage localization was carried out on a homemade composite fan blade, where the damage was tested at various locations and sizes. The results show that the damage localization on the blade is good and 3mm tiny damage localization is achieved.