Ground-penetrating radar (GPR) has become one of the key technologies in subsurface sensing and, in general, in nondestructive testing (NDT), since it is able to detect both metallic and nonmetallic targets. GPR has proven its ability to work in electromagnetic frequency range for subsoil investigations, and it is a risk-reduction strategy for surveying underground various targets and their identification and detection. This paper presents the results of a case study which exceeds the laboratory level being realized in the field in a real case where the scanning conditions are much more difficult using GPR signals for detecting and assessing underground drainage metallic pipes which cross an area with large buildings parallel to the riverbed. The two urban drainage pipes are detected based on GPR imaging. This provides an approximation of their location and depth which are convenient to find from the reconstructed profiles of both simulated and practical GPR signals. The processing of data recorded with GPR tools requires appropriate software for this type of measurement to detect between different reflections at multiple interfaces located at different depths below the surface. In addition to the radargrams recorded and processed with the software corresponding to a GPR device, the paper contains significant results obtained using techniques and algorithms of the processing and post-processing of the signals (background removal and migration) that gave us the opportunity to estimate the location, depth, and profile of pipes, placed into a concrete duct bank, under a structure with different layers, including pavement, with good accuracy.

This paper proposes the study and implementation of a sensor with a metamaterial (MM) lens in electromagnetic nondestructive evaluation (eNDE). Thus, the use of a new type of MM, named Conical Swiss Rolls (CSR) has been proposed. These structures can serve as electromagnetic flux concentrators in the radiofrequency range. As a direct application, plates of composite materials with carbon fibers woven as reinforcement and polyphenylene sulphide as matrix with delaminations due to low energy impacts were examined. The evaluation method is based on the appearance of evanescent modes in the space between carbon fibers when the sample is excited with a transversal magnetic along z axis (TMz) polarized electromagnetic field. The MM lens allows the transmission and intensification of evanescent waves. The characteristics of carbon fibers woven structure became visible and delaminations are clearly emphasized. The flaws can be localized with spatial resolution better than λ/2000.

This paper proposes a method for eddy current non-destructive examination of carbon fibres from carbon epoxy composites as well as the regions impacted with bullets from Kevlar textures. In this aim, an eddy current focused micro sensor, send-receiver type with orthogonal coils was developed. The obtained data were post processed using an incoherent holographic technique. By a small modification of lift-off, the successive layers of fibres can be visualised and, implicitly, their integrity. Using a similar method, the boundaries of the region impacted by a bullet from Kevlar textures were completely emphasised.

This article presents a novel send-receive type of inner-eddy-current transducer. A rotating magnetic field created by three rectangular coils, fed by a triphased alternating-current system, was used for emission. The reception part is made from a circumferential array of coils, consecutively interrogated by measurement equipment. The source that creates the rotating magnetic field is described. The field created by this in free space is presented, and the forward problem using the volume integral method and dyadic Green's function for cylindrical layered media is solved. The experimental measurements are in good agreement with the predictions of the model.