Method improves ultrasonic inspection of complex parts

Ultrasonic waves can find faults in adhesive bonds holding composite parts together and the research from Penn will let engineers select the best frequencies to detect adhesive failures in hard-to-reach places.

Different ultrasonic modes work best for different materials and configurations using the right one will locate more flaws with higher precision, according to the researchers. The selection process could save time and effort for engineers who perform maintenance on complex structures made from composite materials.

Adhesive bonds are better for attaching composite parts than nuts and bolts, which pierce and weaken structural integrity, but heavy operation can crack the glue, damaging the bond’s effectiveness. Ultrasonic waves let engineers examine bonded regions non-destructively.

‘This technique is very widely used in aerospace engineering because those structures require a very high reliability,’ said Baiyang Ren, postgraduate in engineering science and mechanics.

For bonded regions located between easily accessible, wide surfaces, obtaining a clean readout is straightforward as ultrasonic waves pass through the bonded intersection to a receiver on the other side without interference. However, for bonds between inaccessible, irregularly angled surfaces, the ultrasonic wave will convert into a different mode by the time it enters and travels through the bonded region, and this new wave mode may not be as sensitive to adhesive flaws.