On the use of phase laws for the Linear Sampling Method in an elastic waveguide. Application to nondestructive testing

This paper presents the use of phased array data as the input of the Linear Sampling Method for elastic waveguides. Indeed, this method enables the high frequency, hence high resolution, inspection of waveguides, which is of interest for example for nondestructive testing applications. However, the use of single emitter data, also known as Full Matrix Capture in the Non Destructive Testing (NDT) context, leads to poor signal to noise ratios as low amplitude signals are emitted and only a fraction of the energy reaches the potential defect. The use of phase laws, that is the simultaneous emission with multiple sensors, enables better signal to noise ratios. However, the drawback may be a loss on the conditioning of the method, which may lead to higher sensitivity to noise in the end. This paper shows how to choose the sensors and the phase laws to obtain a satisfactory imaging results. This is exemplified on experimental data acquired in a steel plate with a circular hole.