抄録
In this study, we applied non-contacting NRUS (nonlinear resonant ultrasound spectroscopy), and nonlinear three-wave mixing method to evaluation for fatigue damage in aluminum alloy plates subjected to zero-to-tension cyclic loading, These methods were resonance-based techniques exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency of an object was studied as a function of the excitation level. As the excitation level increases, the elastic nonlinearity was manifest by a shift in the resonance frequency. In nonlinear three-wave mixing method, two intersecting ultrasonic waves produced a scattered wave when the resonance condition was satisfied. The wave amplitude was measured. NRUS and nonlinear three-wave interaction method exhibits high sensitivity to micro-structural change of the damaged material. It rapidly increases from 60 % of fatigue life to the fracture The sensitivity in three-wave interaction methods was higher than that in NRUS. These noncontact resonance-EMAT measurement can monitor the evolution of nonlinear acoustic characterizations throughout the fatigue life and has a potential to assess the damage advance and predict the fatigue life of metals.
