2019 Volume 75 Issue 2 Pages I_71-I_81
The simulation-aided time reversal imaging method has been proposed for nondestructive ultrasonic testing. In this study, we describe the theory of the time reversal imaging method in detail and validate it for an anisotropic material using ultrasonic measured signals. First the incident wave arrives at the flaw, which is called ’illumination’, and then scattered waves from flaws are recorded at the array elements. Next the time-reversed signals are emitted into a finite element model which imitates the target material. The time reversal waves propagate in the model and focus on the flaw location. By calculating a crosscorrelation of the incident and the reverse propagated waves, the flaw shape can be uniquely determined. In the measurement, the elastic constants of the anisotropic material were estimated using wavefield data measured by a laser ultrasonic method. An artificial flaw in the target material can be reconstructed by the proposed method. It was shown that the flaw imaging area depends on the first illumination, and the frequency components contribute the intensity of the flaw shape.
