Localization of material defects using nonlinear resonant ultrasound spectroscopy under asymmetric boundary conditions

The position of microscopic defects in a one-dimensional bar is analyzed by means of the nonlinear resonant ultrasound spectroscopy technique under asymmetric boundary conditions. Experimental results on cementitious material confirm the feasibility of the method to locate nonlinear scatterers. Good agreement between the real damage position and the inferred experimental prediction is obtained based on information about the nonlinear frequency shift and about the amplitude ratio of the third and fifth harmonic for the fundamental resonance mode.