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

Abstract

Ultrasonic guided wave (UGW) has a wide monitoring range and high accuracy, showing promise for monitoring damage in large-area composite fan blades. However, the multi-curvature characteristics of engine composite fan blades and their anisotropic material properties make damage localization difficult 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 differences. This method addresses the challenge of locating damage in multi-curvature composite blades. 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 receiving 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 used to draw a vertical line on the propagation path, identified as the damage likelihood line (DLL). Finally, the DLL corresponding to the three largest DIs is selected, and their intersections were used for damage localization. A time-domain truncated signal processing method is proposed to enable the DI to more accurately represent the effects of damage and improve the localization accuracy of the method. An experiment on damage localization was conducted 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 3 mm tiny damage localization is achieved.