Ultrasonic Adaptive Detection for Aerospace Components with Varying Thickness

Abstract

Automatic inspection of microdefects located in the aerospace components is difficult due to the imprecise scanning trajectory, especially for those specimens with varying thickness. In this paper, a new ultrasonic nondestructive testing (NDT) system using the robotic scanning trajectory is constructed for inspecting turbine blades. Additionally, an approach based on the analysis of ultrasonic signals is proposed to calibrate the trajectory; the ultrasonic image based on the threshold function represents the distribution of inner defects when the following gate is used to track the flaw echo. Therefore, the characteristic parameters of the flaw echo signals are easy to be discriminated if the reflection waves are stable in the time domain. Experimental result verified the effective and feasibility of the proposed approach; the distribution of inner defects can be shown with a higher resolution than other NDT methods when robotic orientation is correct at each point of scanning trajectory. Furthermore, the feature signals can be tracked more accurately during the ultrasonic signal processing if the ultrasonic distance was considered as a calibration coefficient of positional matrix. The proposed ultrasonic adaptive detection is adapted to complex geometric structure with a minimum resolution of equivalent diameter of the inner flaw being 0.15 millimeters.