Three dimensional ultrasonic imaging: An aging aircraft nondestructive inspection tool

摘要

Ultrasonic nondestructive evaluation is a valuable technique for finding defects in aircraft structures. It can detect unbonds, corrosion damage and cracks in various aircraft components. Ultrasonic nondestructive evaluation techniques interrogate materials with high frequency acoustic energy. A piezoelectric transducer generates acoustic energy and converts returned acoustic energy into electrical signals which can be processed to identify the reflector. The acoustic energy propagates through the component and is reflected by abrupt changes in modulus and/or density that can be caused by a defect. Ultrasonic nondestructive evaluation typically provides a two dimensional image of internal defects. These images are either a planar view (C-scan) or a cross-sectional view (B-scan) of the component. The planar view is generated by raster scanning an ultrasonic transducer over the area of interest and capturing the peak amplitude of internal reflections. Depth information is generally ignored. The crass-sectional view is generated by scanning the transducer along a line and capturing the amplitude and time of flight for each internal reflection. The amplitude and time of flight information is converted into an image of the cross section of the component. By fusing the C-scan information with the B-scan information a three dimension image of the internal structure of the component can be produced. The three dimensional image can be manipulated by rotating and slicing to produce the optimal view of the internal structure. Visualizing defects in three dimensions aids the interpretation of the severity of defects and helps confirm the need to repair or replace components.