Aircraft safety: New imaging technique could detect acoustically 'invisible' cracks

The next generation of aircraft could be thinner and lighter thanks to the development of a new imaging technique that could detect damage previously invisible to acoustic imaging systems.

The nonlinear acoustic technique developed by researchers from the University of Bristol's Ultrasonics and Non-destructive Testing (NDT) research group is published in the current issue of Physical Review Letters together with an accompanying article in Physics.

It has long been understood that acoustic nonlinearity is sensitive to many physical properties including material microstructure and mechanical damage. The lack of effective imaging has, however, held back the use of this important method.

Currently engineers are able to produce images of the interior of components using ultrasound, but can only detect large problems such as cracks. This is like detecting only broken bones in a medical environment.

Imaging of acoustic nonlinearity is achieved by exploiting differences in the propagation of fields produced by the parallel and sequential transmission of elements in ultrasonic arrays.

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