Pump-probe localization technique of varying solid contacts

A baseline-free defect localization method in thin plates is proposed and tested. In this proof-of-concept work, a steel ball pressed against an aluminum plate used to mimic surface contact defect. The technique takes benefit of repetitive nonlinear pump-probe interaction with backpropagation imaging algorithm. High-frequency probe waves are periodically emitted by piezoelectric patch transducer glued the plate. Propagated flexural recorded using distributed array transducers. At same time, continuous low-frequency pump vibration provided shaker fixed modulates state. By combining multiple signals, can be successfully localized. Contrast images finally improved factor 3 5 implementing modified version based on synchronous detection