Engineers at Bristol University in the UK say they have developed new ultrasonic technology that can show hidden cracks in the wings of planes or bridges, which would previously have gone undetected.
This could mean increased safety as it provides an important tool for inspectors to replace materials before they get overused.
The way it works is that the system locates so-called acoustic nonlinearities, in other words places where multiple sound waves don’t add up as one might expect, which often reveal sites of cracks or extreme fatigue.
Anthony Croxford and his team use a technique called nonlinear ultrasonics to look inside the materials. Hundreds of sound signals are sent through the material, giving a picture of what is inside – and where even the tiniest cracks could be located.
“The way this works is that your energy essentially shakes that crack, it rattles it on the way in, and that leads to harmonics, so you put in one frequency and you get out other frequencies. In a purely linear system, you only get out the frequency you put in. By using this novel approach we can now pick up a crack close to a hole, which is directly relevant to, say, aerospace applications, where they’re worried about cracks growing from rivet holes, things like that,” explains Anthony Croxford, Senior Lecturer in Mechanical Engineering at Bristol University.
Croxford says the real strength of this approach is in the tools needed. The nonlinear method of acoustic imaging requires equipment that is already being used within the industry.
Such advances in non-destructive evaluation not only increase the safety of structures but can help future design, for example, allowing the next generation of aircraft to be built thinner and lighter.
Scientists also hope the technology could help build metal structures like bridges in a better, safer way in the future.