Structural health monitoring for multi-strand aircraft wire insulation layer based on ultrasonic guided waves

•Online defect detection technology for multi-strand aircraft wire insulation layer.•Offering early warning before aircraft wire failure.•The method proposed in this paper is of high defect localization accuracy. Aircraft wire insulation layer with defects can cause serious accidents that threaten the life of the people on board. Compared with the traditional aircraft wire detection methods, an on-line detection for multi-strand aircraft wire (MSAW) based on ultrasonic guided waves (UGWs) is proposed. In this paper, the propagation characteristics of UGWs in MSAW are investigated by numerical simulations and experiments. In the experiment, a 5 cycles Hanning window modulated sinusoidal waves with a center frequency of 20 KHz is employed as excitation signal. The experimental results show that this method effectively detect 4 different types of defects in a 3-strand aircraft wire and the maximum defect location relative error is 1.6 %. The amplitude of defect reflected echoes decrease as the axial length and circumferential ratio of these defects increased from 2 mm to 10 mm and 12.5 % to 100 %, respectively. An interesting phenomenon is found that the defects reflection energy in a wire can be acquired in other wires which shows that UGWs energy disperse among wires. The experiment successfully detected each defect in the MSAW, proving the effectiveness of the proposed method.