Acoustographic nondestructive evaluation

The authors discuss some of the basic principles underlying acoustography and its use as a nondestructive evaluation methodology. Acoustography is a process of forming ultrasonic images in a manner analogous to radiography and fluoroscopy. A sound source insonifies the test object with a uniform field of ultrasound. As the ultrasonic waves pass through the test object, they are differentially attenuated. The existing ultrasound casts a shadow that is converted into a visual image using an `acousto-optical´ display. It is concluded that acoustography can detect typical flaws, e.g., delaminations, inclusions, impact damage porosity, encountered in graphite/epoxy composite laminates. Since a direct full-field image is obtained within seconds, acoustography offers the potential for high-speed testing of large areas. Acoustography can inspect complex geometry parts with relative ease compared with conventional ultrasonic methods