Damage location by ultrasonic Lamb waves and piezoelectric rosettes

An approach based on macro-fiber composite transducer rosettes and ultrasonic guided waves is proposed for damage location in plate-like structures. By using the directivity behaviour of the three macro-fiber composite sensors in each rosette, the direction of an incoming wave generated by scattering from damage can be estimated without knowledge of the wave velocity in the structure. Two rosettes suffice to identify the location of a scatterer in a planar structure. The technique does not have the drawbacks of time-of-flight triangulation, requiring information on wave velocity that complicates the damage location when testing anisotropic materials, tapered sections or any structure under temperature fluctuations. The effectiveness of the piezoelectric rosette method is tested experimentally on an aluminium plate with a simulated damage subjected to temperature variation.