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As the demand of structural integrity in manufacturing industries is increasing, the ultrasonic array technique has drawn more attention thanks to its inspection flexibility and versatility. By taking advantage of the possibility of individual triggering of each array element, full matrix capture (FMC) data acquisition strategy has been developed that contains the entire information of an inspection scenario. Total focusing method (TFM) as one of the ultrasonic imaging algorithms, is preferably applied to FMC dataset since it uses all information in FMC to synthetically focus the sound energy at every image pixel in the region of interest. Half-skip TFM (HSTFM) is proposed in multi-mode TFM imaging that involves a backwall reflection wave path, so that the defect profile could be reconstructed for accurate defect characterization. In this paper, a method involving Snell’s law-based wave mode conversion is proposed to account for more reasonable wave propagation time when wave mode conversion happens at backwall reflection in HSTFM. A series of model based simulations (in software simSUNDT) are performed for parametric studies, with the intention of investigating the capability of defect characterization using HSTFM with varying tilt angle and relative position of surface-breaking notch to array probe. The results show that certain TFM modes could help with defect characterization, but the effectiveness is limited with varying defect features. It is inappropriate to address a certain mode for all characterization perspectives but rather a combination, i.e., multi-mode TFM, should be adopted for possible interpretation and characterization of defect features., CC BY 4.0

In this work, we propose an optimized auto-focusing algorithm to be used with ultrasound matrix arrays for three-dimensional imaging in the presence of interfaces. Its main application is for non-destructive-testing (NDT), where usually two mediums with different propagation velocities are present. The refraction at the interface between those mediums complicates the calculation and the application of the focusing delays, which requires iterative processes that are usually the main bottleneck for high-speed inspections. We tackle this problem by generalizing the virtual array concept previously proposed for linear arrays and plane images to the case of matrix-arrays and three-dimensional (3D) beamforming. Furthermore, we propose a two-dimensional iterative algorithm for exact time-of-flight calculation to the two foci per scan line required by the virtual array. The mathematical formulation for the 3D case is obtained and the time-delay errors are analyzed by simulation. Finally, image quality with the proposed method is compared with that obtained with conventional Total Focusing Method (TFM) and exact delay calculation. The principal conclusion is that the virtual array approach generates images with equivalent quality to those obtained by exact calculation, while it reduces more than two orders of magnitude the computation load.

While ultrasound testing (UT) with linear transducer arrays is a widely used method in Non-destructive Testing (NDT), the use of matrix arrays is not so widespread in the field. Nevertheless, matrix arrays can be used to do volumetric imaging without the need to displace the transducer. Furthermore, they provide a solution to the lack of resolution in the elevation direction characteristic of linear arrays, and the possibility to steer the beam in every direction in space. In this work, we propose an optimized auto-focusing algorithm to be used with ultrasound matrix arrays for three-dimensional imaging in the presence of interfaces, as is the case in immersion testing frequently used in NDT.

There has been an increase in the use of ultrasonic arrays for the detection of defects in composite structures used in the aerospace industry. The response of a defect embedded in such a medium is influenced by the inherent anisotropy of the bounding medium and the layering of the bounding medium and hence poses challenges for the interpretation of the full matrix capture (FMC) results. Modeling techniques can be used to understand and simulate the effect of the structure and the defect on the received signals. Existing modeling techniques, such as finite element methods (FEM), finite difference time domain (FDTD), and analytical solutions, are computationally inefficient or are singularly used for structures with complex geometries. In this paper, we develop a novel model based on the Gaussian-based recursive stiffness matrix approach to model the scattering from a side-drilled hole embedded in an anisotropic layered medium. The paper provides a novel method to calculate the transmission and reflection coefficients of plane waves traveling from a layered anisotropic medium into a semi-infinite anisotropic medium by combining the transfer matrix and stiffness matrix methods. The novelty of the paper is the developed model using Gaussian beams to simulate the scattering from a Side Drilled Hole (SDH) embedded in a multilayered composite laminate, which can be used in both immersion and contact setups. We describe a method to combine the scattering from defects with the model to simulate the response of a layered structure and to simulate the full matrix capture (FMC) signals that are received from an SDH embedded in a layered medium. The model-assisted correction total focusing method (MAC-TFM) imaging is used to image both the simulated and experimental results. The proposed method has been vali-dated for both isotropic and anisotropic media by a qualitative and quantitative comparison with experimentally determined signals. The method proposed in this paper is, Structural Integrity & Composites

Glass fibre-reinforced polymer composites are often used in corrosive environments. However, the material can suffer from loss of mechanical durability as a result of an attack of the media. In order to protect the structural bearing laminate, the composites are segmented in different levels, the structural layer and the corrosion barrier layer, each containing a higher or lower percentage of glass fibre and thereby holds varying durability towards chemical attacks. This work applies the total focusing method, a delay-and-sum beamformer technique based on the full matrix capture, a routine that provides a complete set of time series from an array. Glass fibre-reinforced composites have directional dependent properties and high attenuation, complicating the modelling of ultrasonic propagation. In the project described in this thesis, pulse-echo measurement and phased arrays are used to estimate the thickness of the corrosion barriers, before and after, exposure to acid in high temperatures. A filter prior to imaging is designed to project the received phased array data onto a theoretical surface subspace. Experiments showed that the corrosion barrier thickness was measurable, when the laminas were sufficiently separated in the structural layer, no traces of the penetrated acid could be detected., Validerat; 20151104 (global_studentproject_submitter)

DTFR53-11-D-00008L, Under the sponsorship and support of the Federal Railroad Administration (FRA), Transportation Technology Center, Inc. (TTCI), with participation from the original equipment manufacturer (OEM) of advanced nondestructive evaluation (NDE) equipment, NDE service providers, and other research institutions, conducted a feasibility study of applying advanced NDE methods to detect and characterize weld defects in railroad tank cars. Researchers evaluated the performance/capability of various state-of-the-art advanced NDE techniques for fatigue crack detection and characterization in railroad tank car butt welds and fillet welds. The team determined that advanced NDE methods could detect toe fatigue cracks with acceptable signal-to-noise ratio (SNR) while demonstrating challenges with accurate flaw sizing. Further, based on the false positive results obtained from this study, the team found that detailed attention and efforts are required to reduce the false positive rate