Mirror Aided Ultrasonic Testing of the bonding interface of dual-alloy blisk through the bore

Welded dual-alloy blisks have found more and more applications in aeroengines for their excellent high temperature performance. However, defects may develop within the bonding interface and threat the safety of the engine. In this paper, the ultrasonic testing of the bonding interface was investigated in the dual-alloy blisk with a small bore. Aided by a 90 degrees mirror, the longitudinal wave was introduced to the interface. Simulations and theoretical analyses were performed to explain the propagating behavior of the sound beam upon the strongly curved surface. It was observed when the focus of the probe approaches a certain point, the beam distortion was compensated under ‘acoustic lens effect'. The cylindrical focused probe was found to give better performance than flat probes and spherical focused probes in terms of sensitivity and resolution. The experiments on a mock-up sample showed that φ0.8mm FBH and Φ0.4mm SDH at the bonding interface were detectable with a 15MHz cylindrical focused probe.