Fully Noncontact Hybrid NDT for 3D Defect Reconstruction Using SAFT Algorithm and 2D Apodization Window

Abstract

Nondestructive testing of metallic objects that may contain embedded defects of different sizes is an important application in many industrial branches for quality control. Most of these techniques allow defect detection and its approximate localization, but few methods give enough information for its 3D reconstruction. Here we present a hybrid laser–transducer system that combines remote, laser-generated ultrasound excitation and noncontact ultrasonic transducer detection. This fully noncontact method allows access to scan areas on different object’s faces and defect details from different angles/perspectives. This hybrid system can analyze the object’s volume data and allows a 3D reconstruction image of the embedded defects. As a novelty for signal processing improvement, we use a 2D apodization window filtering technique, applied along with the synthetic aperture focusing algorithm, to remove the undesired effects due to side lobes and wide-angle reflections of propagating ultrasound waves, thus enhancing the resulting 3D image of the defect. Finally, we provide both qualitative and quantitative volumetric results that yield valuable information about defect location and size.

Directional Ultrasound Source for Solid Materials Inspection: Diffraction Management in a Metallic Phononic Crystal

“…Figure 11 shows a schematic representation of the defect embedded in the target material. We simulate the ultrasound propagation and we detect the transmitted ultrasound waves at the opposite side of the target (transmission NDT mode).This topology is used in many NDT analyses in the literature as well as beam forming for NDT applications [35][36][37][38][39][40].We compare the results obtained in the case of a healthy sample (shown in Figure 8) with those corresponding to a sample with an elliptical crack (elliptical trigonometric orthogonal axes' parameters a, b = 1, 2 cm respectively) and simulated as an air filled crack at a horizontal distance of 80 cm from the left border of the aluminium target specimen and vertically positioned at 20 cm in the middle of the specimen with and without using the ultrasound lens formed by the PC. Figure12 a show the surface plot of magnitude of the displacement field, abs(u), in the case of a normal diverging beam with no crystal, for a sample with an embedded elliptical crack.…”

Design of 2D Planar Sparse Binned Arrays Based on the Coarray Analysis

“…On the other hand, there is an increasing interest in synthetic aperture imaging methods [ 2 , 4 , 5 ], where all signals corresponding to each pair of emission and reception elements in the array are independently acquired, and the focusing process is performed as a part of digital signal processing operations. These solutions can be implemented with a trade-off between parallel resources and acquisition time and, although there is lower SNR (Signal-to-Noise Ratio) when compared to phased-arrays, the complete set of signals is rich in information [ 6 , 7 ].…”

Accurate 3D reconstruction of complex defects based on combined method of MFL and MFDs

“…Non-destructive testing (NDT) technologies can help engineers to achieve fast defect localization and sizing. As compared with other available (such as ultrasonic- [1], capacitive-based [2]) NDT imaging methods [3], magnetic NDT methods has balanced advantages of high precision, fast and convenience in implementation though they are only adequate for ferromagnetic materials and structures, such as steel strip [4], pipelines [5][6][7] and stay cables [8,9]. In magnetic flux leakage (MFL) inspection, the tested ferromagnetic specimen should be magnetized.…”