Experimental Validation of Ultrasonic Imaging Using Topological Derivative

We investigated an array ultrasonic imaging method using the topological derivative. The topological derivative is formulated based on the sensitivity of the cost functional associated with the inverse scattering problem due to the creation of an infinitesimal rigid inclusion. To calculate the topological derivative, time convolutions of a free field and a supplementary adjoint field are required. In this study, scattered waves from flaws were received with an array transducer, then the supplementary adjoint field using the measured waves was calculated in the framework of the finite integration technique (EFIT). Finally, flaw imaging was performed by plotting the obtained topological derivative in the target region.