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In recent years, the manufacturing process of lead zinc niobate-lead titanate [Pb(Zn1/3Nb2/3)O3-PbTiO3, also called PZN-PT] has been enhanced with improvements in size, consistency and a suitable compromise between piezoelectric properties and phase transition temperature, which means that it is possible to obtain PZN-PT single crystals in sufficient size for performance characterization studies and batch manufacturing to produce high-performance medical ultrasonic transducers. This paper mainly focuses on the development of the 64-element phased array ultrasonic transducer based on novel large-size PZN-PT piezoelectric single crystals. The composition of the single crystal was chosen as PZN-5.5 %PT. The designed center frequency of the phased array is 3.0 MHz, which is suitable for cardiac ultrasound imaging. The array elements were spaced at a 0.254 mm pitch, and interconnected through a custom-designed flexible circuit. Double matching layers with a light backing structure were applied in the transducer fabrication process to improve the performance of the array. The test results of the developed phased array showed a center frequency of 3.0 MHz, and an average -6 dB fractional bandwidth of 72%. In the vicinity of the center frequency, the two-way insertion loss (IL) was about -46 dB, while a crosstalk between the adjacent elements was less than -31 dB. The wire phantom can be distinctly imaged with the phased array and the axial and lateral resolutions were measured to be 660 and 1299 μm, respectively. The image of a standard phantom was acquired to present the imaging performance of the transducer. The final results indicate that the transducer arrays based on novel large-size PZN-PT single crystals are quite promising for use in medical ultrasound imaging applications.

High-density polyethylene (HDPE) above-ground storage tanks (AST) are used by highway agencies to store liquid deicing chemicals for the purpose of road maintenance in the winter. A sudden AST failure can cause significant economic and environmental impacts. While ASTs are routinely inspected to identify signs of aging and damage, current methods may not adequately capture all defects, particularly if they are subsurface or too small to be seen during visual inspection. Therefore, to improve the ability to identify potential durability issues with HDPE ASTs, additional non-destructive evaluation (NDE) techniques need to be considered and assessed for applicability. Specifically, this study investigates the efficiency of using infrared thermography (IRT) as a rapid method to simultaneously examine large areas of the tank exterior, which will be followed by closer inspections with conventional and phased array ultrasonic testing (UT) methods. Results show that IRT can help to detect defects that are shallow, specifically located within half of the tank’s wall thickness from the surface. UT has the ability to detect all defects at any depth. Moreover, phased array UT helps to identify stacked defects and characterize each defect more precisely than IRT. Published version

Firstly, a novel FRI sampling model has been proposed according to the characteristics of ultrasonic signals. The model has the advantages such as good stability, strong antinoise ability, simple circuit implementation, and fewer preconditions, compared to the traditional methods. Then, in order to verify the validity of the sampling model, the method is applied to B-type ultrasonic imaging, and a B-type phased array ultrasonic imaging algorithm based on FRI sampling model is proposed. Finally, the algorithm simulation experiment is designed, and the results show that the sampling point required by the proposed FRI sampling model is only 0.1% of the traditional B-type phased array ultrasonic imaging method, and the sampling frequency of the proposed ultrasonic imaging algorithm is only 0.0077% of the traditional B-type ultrasonic imaging method. Additionally, the experiment result indicates that this algorithm is more applicable to phased array ultrasonic imaging than the SOS filter is.

Rail monitoring is an important activity which aims to preserve the safety and availability of railways. According to statistics, the primary cause of railway accidents is due to transverse defects that occur in the rail head. These special defects develop generally in a plane orthogonal to the rail running direction. The detection of these defects is a priority to increase the safety of rail transportation. Rail control monitoring techniques mostly rely on infrared thermography, eddy currents, air-coupled acoustic sensors, and ultrasounds. The present research studies the rail diagnosis by means of a non-contact device. The focus is on ultrasonic based methods where excitation is generated by thermal elastic coupling following laser irradiation of the rail head. For the reception of echoes, a special ultrasound sensor was used. In order to sense defects, phased array elements, which use multiple transducers and electronic time delays, are used to increase and to focalise the signal intensity. Flaws that have a moderate extension are better detected by the proposed method than with laser irradiation consisting of a single spot.

Multi-layered steel vessel (MLSV) for high-pressure hydrogen storage is an important equipment in hydrogen refueling station and periodic inspection is necessary to be carried out on it. Welded joint between the head and thick-walled nozzle of the vessel is the key point of the inspection. In this study, based on structural characteristics of MLSV, a method of inserted curved surface coupling phased array ultrasonic inspection (PAUI) was proposed. In order to achieve effective inspection on the welded joint, acoustic field calculation model of the welded joint by PAUI was established. Influences of various inspection parameters on the acoustic field were analyzed by considering difficulties of far detection distance, wide detection area and large material attenuation systematically to obtain optimized parameters and scanning method. Corresponding probe was subsequently made according to the analysis, and experiment was carried out on test block to prove effectiveness of the method in this study.

In the present work, the effect of low-speed impact on the static residual strength of aluminum foam sandwiches having GFRP skins has been evaluated. Two different configurations have been considered, which differs both for thickness and layup used for the manufacturing of GFRP skins. The detection and the quantification of the damage induced by impact have exploited the potentiality of pulsed thermography and phased array ultrasonic techniques, which gives the possibility to provide synergistic and complementary information. Mechanical strength has been evaluated through three-point bending tests carried out on undamaged and damaged specimens. Static tests allowed also evaluating the failure mode of panels and the changes induced by the presence of a low-speed impact zone.

In safety dominant industries, nondestructive evaluation (NDE) is crucial in quality assurance and assessment. Phased array ultrasonic testing (PAUT) as one of the NDE methods is more promising compared with conventional ultrasonic testing (UT) method in terms of inspection speed and flexibility. To incorporate PAUT, the techniques should be qualified, which traditionally is performed by extensive physical experiments. However, with the development of numerical models simulating UT method, it is expected to complement or partly replace the experiments with the intention to reduce costs and operational uncertainties. The models should be validated to ensure its consistency to reality. This validation work can be done by comparing the model with other validated models or corresponding experiments. The purpose of current work focuses on the experimental validation of a numerical model, simSUNDT, developed by the Chalmers University of Technology. Validation is conducted by comparing different data presentations (A-, B- and C-scan) from experimental and simulated results with some well-defined artificial defects. Satisfactory correlations can be observed from the comparisons. After the validation, sound field optimization work aiming at retrieving maximized echo amplitude on a certain defect can be started using the model. This also reveals the flexibility of parametric studies using simulation models.

The article presents results of tests performed to determine the noise level in ultrasonic Phased Array testing. The tests, involving non-alloy steel S355 and austenitic steel X5CrNi18-10, were carried out applying a frequently used test configuration and 16-element 5 MHz array probes having an aperture of 10 mm ×10 mm. The obtainment of a differentiated structure, i.e. characterised by various grain sizes, required the performance of special heat treatment processes. Metallographic tests, concerning both steel grades, were performed to quantify the grain size. Specimens containing artificially made SDH Ø3 cylindrical reflectors and spherical reflectors having various diameters were made of the material prepared in the above-presented manner. The tests also involved amplitude measurements and the identification of the noise level of the reflectors. The test results enabled the quantitative determination of the signal-noise ratio, affecting the detection of low-amplitude indications.

In this study, near-surface cracks in a railhead are inspected thoroughly using phased array ultrasonic testing (PAUT). This research finds an alternative technique to inspect for near-surface cracks because the conventional non-destructive testing method for rail inspection lacks the capacity to inspect the near-surface crack profile. This study shows that PAUT can determine not only the crack depth but also the near-surface crack profile, so that the inspector can estimate the stage of crack growth and how the crack propagates. This information is valuable to the rail maintainer as one of the considerations for deciding the thickness of metal to remove when grinding the rail. In this study, after the measurement, the inspected region of the cracked railhead is sliced into thin pieces so that crack network information can be extracted. A 3D image reconstruction of the surface cracks based on the crack marks from all of the sliced rail pieces is performed. This image is then used as a reference to confirm the PAUT results. The results show that PAUT can clearly deliver crack profile estimation and provide an accurate estimation of a 3.51 mm crack-tip depth with an absolute error range of 8%-18%. The results also suggest that PAUT is a potential method for installation in a measurement train for near-surface crack inspection.

This paper presents the evaluation of two promising non-destructive testing (NDT) methods for the inspection of additively manufactured (AM) parts: a resonant acoustics method (RAM) and a phased array ultrasonic testing (PAUT) method involving a full matrix capture (FMC) acquisition procedure and a total focused method (TFM) to post-process the data and reconstruct the images. The two methods were evaluated using the so-called star artefacts designed in the international standardisation joint group 59 of the ISO/TC261-ASTM/F42 dedicated to NDT for AM parts. These artefacts contain inner and outer features simulating typical AM flaws lying between 100 and 700 μm. The RAM enabled to sort the artefacts with flaws from the reference artefacts without flaw. However, RAM was unable to separate the artefacts according to the number of flaws they contained. The detection with PAUT depended on the shape, orientation and location of the flaws. The best results were obtained for the vertical cylinders, simulating AM cross-layer flaws. They could be detected up to 200 μm.

Friction welding of tube-to-tube plate using external tool (FWTPET) 1 is an innovative friction welding process wherein a friction stir welding tool is used to join tube and tube plate. This work investigates the combined effects of tool rotation speed and plunge duration in terms of a parameter named Total Welding Rotation (TWR) 2 , on the quality of FWTPET joints. A mathematical model is proposed to understand the upper and lower limits of TWR, beyond which the process is inclined to give defective joints. This model is verified using experimental studies on joints between AA6061 plate and AA1060 tube. The welded specimens are non-destructively evaluated using Digital Radiography (DR) 3 and Phased Array Ultrasonic Testing (PAUT) 4 , which show that above and below certain TWR values the process leads to defective joints.

The automatic phased array ultrasonic testing method has been developed for inspecting the pipe welds with complex geometry. Applying time of flight diffraction (TOFD) technique has two problems: one is the difficulty in recognition of head wave under complex structure; the other is the limited scanning space cannot provide the needed span for pitch-catch mode. To overcome these two problems, an array probe can be placed on the surface of base metal of the weld by the direct and double traverse techniques. In order to design the optimal scanning path for high probability of detection and inspection rate, the model of beam path on tilt steps was established to quantitatively analyze the effects of tilt steps on beam coverage and mode conversion. Experiments were conducted to validate the proposed rule of planning the optimal scanning path. All artificial defects in the mock-up block were detected on the scanning side of which exists the optimal scanning path. While for the scanning side without the optimal scanning path, a combination of scanning is needed to avoid missing inspection.

The China Fusion Engineering Testing Reactor (CFETR) vacuum vessel (VV) port stub was formed by electron beam welding (EBW). In this article, the phased array ultrasonic testing (PAUT) method was introduced for testing the quality of the weld. First, the acoustic field simulation and analysis of the EBW of 316L austenitic stainless steel were carried out with different frequency probes, then the microstructure of electron beam welds were observed by microscopic metallographic to analyze the influence of the type and influence of probe, finally fabricating the reference test blocks according to the NB/T47013-2015 standard to conducting the PAUT experiment. The test results show that the type of probe has less influence on the signal-to-noise ratio (SNR) and localization of the detection of large-thickness austenitic stainless steel electron beam welds under low-frequency conditions. The SNR of EBW detection was gradually decreased as the frequency of the probe increases under the same type of probe. In the direction of depth of the EBW, with the increase in the depth, the weld microstructure size becomes finer, so the sector scan image of $\phi ~1$ -mm side drilled hole (SDH) near the upper weld was severely distorted, while the sector scan image of $\phi ~1$ -mm SDH near the lower EBW was relatively good.

Submarine pressure hulls must withstand high hydraulic pressure and be free of defects. To improve the precision of defect detection, we herein examined different probes for optimal defect assessment by applying the Phased Array Ultrasonic Testing (PAUT) method. Two sets of probe design parameters were selected by considering pressure hull characteristics and analyzed through modeling. PAUT probes were applied, and defect assessment results were compared based on ultrasonic signals of various simulated defects in specimens designed to be the same as actual pressure hulls. The final selected design parameters for the submarine probe, which were designed to minimize the grating lobe of wave interference effect and improve the ultrasonic resolution of pressure hull welds, were identified through the experiment. The improvement in the probe's ability to detect defects in a pressure hull was verified. Furthermore, the accuracy of defect length measurement was improved, enhancing the applicability of the technique.

Phased array ultrasonic testing is widely used to test structures for flaws due to its ability to produce steered and focused beams. The inherent anisotropic nature of some materials, however, leads to skewing and distortion of the phased array beam and consequently measurement errors. To overcome this, a quantitative model of phased array beam propagation in such materials is required, so as to accurately model the skew and the distortion. The existing phased array beam models which are based on exact methods or numerical methods are computationally expensive or time consuming. This article proposes a modeling approach based on developing the linear phased multi-Gaussian beam (MGB) approach to model beam steering in anisotropic media. MGBs have the advantages of being computationally inexpensive and remaining non-singular. This article provides a comparison of the beam propagation modeled by the developed ordinary Gaussian beam and linear phased Gaussian beam models through transversely isotropic austenitic steel for different steering angles. It is shown that the linear phased Gaussian beam model outperforms the ordinary one, especially at steering angles higher than 20° in anisotropic solids. The proposed model allows us to model the beam propagation from phased arrays in both isotropic and anisotropic media in a way that is computationally inexpensive. As a further step, the developed model has been validated against a finite element model (FEM) computed using COMSOL Multiphysics.

Friction welding of tube-to-tube plate using external tool (FWTPET) is a novel variant of friction welding process for joining tubes to tube plates. This process has the capability of producing leak proof joints between similar or dissimilar materials. Being a solid state welding process FWTPET has a significant advantage that it is free from fusion related defects usually seen in conventional tube to tube plate joining alternatives which use fusion welding methods. Hence this process offers a strong potential for applications in several sectors including automotive, marine, aerospace etc. However, in order to establish FWTPET for industrial applications it is required to develop suitable Non-Destructive Evaluation (NDE) methods for detection and characterization of the defects. In this study, the defects in FWTPET joints welded between 6 mm thick AA 6061 plate and 2 mm thick AA 1060 tube under various conditions are investigated using two advanced volumetric NDE methods, namely Digital Radiography (DR) and Phased Array Ultrasonic Testing (PAUT). This study shows the capability of these volumetric NDE methods to assess the quality of FWTPET joints, and to reveal significant information about the conditions which lead to defect formation. This work also brings out the effect of the parameters of FWTPET using theoretical model and NDE results, and in turn suggests the parametric combinations which could offer defect free joints.

Ultrasonic non-destructive testing traditionally uses a conventional monolithic transducer. An approach similar to this comprising of independent single transmissions but with reception performed by all the elements in phased array ultrasonics is known as Full Matrix Capture (FMC). The acquired data is processed by Total Focusing Method (TFM). Conventional FMC-TFM has limitations in the inspection at large depth in attenuating materials due to single element transmission. To improve the beam forming process, coherent recombination of the plane wave with specific angles is utilized in transmission and the same aperture is used for the reception in Plane Wave Imaging (PWI). A new methodology called Angle Beam Virtual Source FMC-TFM (ABVSFMC-TFM) is proposed to inspect thick attenuating materials such as nickel base alloys. The ABVSFMC method leads to improved Signal to Noise Ratio (SNR) as compared to the conventional FMC due to increased energy with directivity during transmission using a group of elements and improved divergence as compared to the PWI due to a small virtual source near the sample surface. In the present paper, FMC-TFM, PWI-TFM and ABVSFMC-TFM methods are compared for inspection of thick nickel base superalloy (Alloy 617) with slots at various depths in the range of 25-200 mm. Optimization of the incidence angle has been performed by beam computation in CIVA software. Results obtained by CIVA simulations are discussed and also compared for the three methods.

The reliability of the ultrasonic phased array total focusing method (TFM) imaging of parts with curved geometries depends on many factors, one being the probe standoff. Strong artifacts and resolution loss are introduced by some surface profile and standoff combinations, making it impossible to identify defects. This paper, therefore, introduces a probe standoff optimization method (PSOM) to mitigate such effects. Based on a point spread function analysis, the PSOM algorithm finds the standoff with the lowest main lobe width and side lobe level values. Validation experiments were conducted and the TFM imaging performance compared with the PSOM predictions. The experiments consisted of the inspection of concave and convex parts with amplitudes of 0, 5 and 15 λAl, at 12 standoffs varying from 20 to 130 mm. Three internal side-drilled holes at different depths were used as targets. To investigate how the optimal probe standoff improves the TFM, two metrics were used: the signal-to-artifact ratio (SAR) and the array performance indicator (API). The PSF characteristics predicted by the PSOM agreed with the quality of TFM images. A considerable TFM improvement was demonstrated at the optimal standoff calculated by the PSOM. The API of a convex specimen’s TFM was minimized, and the SAR gained up to 13 dB, while the image of a concave specimen gained up to 33 dB in SAR.

In the recent past, Non-Destructive Testing (NDT) has become a most popular technology due to its efficiency and accuracy without destroying the object and maintains its original structure and gathering while examining external and internal welding defects. Generally, the NDT environment is harmful which is distinguished by huge volatile fields of electromagnetic, elevated radiation emission instability and elevated heat. Therefore, a suitable NDT approach could be recognized and practiced. In this paper, a novel algorithm is proposed based on Phased array ultrasonic test (PAUT) for NDT in order to attain the proper test attributes. In the proposed methodology, carbon steel welding section is synthetically produced with various defects and tested using PAUT method. The signals acquired from PAUT device is found with noise interference. The Adaptive Least Mean Square (ALMS) filter is proposed to filter PAUT signal in order to eliminate random noise and Gaussian noise. The ALMS filter is the combination of low pass filter (LPF), high pass filter (HPF) and band pass filter (BPF). The time domain PAUT signal is converted into frequency domain signal in order to extract more number of features by applying Empirical Wavelet Transform (EWT) algorithm. In the frequency domain signal, 1st order and 2nd order features extraction techniques are applied to extract various features for further classification. The Deep Learning methodology is proposed for classification PAUT signals. Based on the PAUT signal features, the Deep Convolution Neural Network (DCNN) is applied for further classification. The DCNN will classify the welding signal is whether it is defective or non-defective. The Confusion Matrix (CM) is used for estimation of measurement of performance of classification as calculating accuracy, sensitivity and specificity. The experiments prove that out proposed methodology for PAUT testing for welding defect classification is obtained more accurately and efficiently across existing methodologies by providing numerical and graphical results.

A numerical simulation-based study is undertaken in order to assess the performance of plane wave imaging in the concrete medium for damage detection. The random scattering of ultrasonic field by the aggregates in the concrete medium incorporates higher background noise in the reconstructed subsurface images using conventional imaging algorithms. This noise can at times mask the imaged defects either partially or completely and hence reducing the capability of damage detection of subsurface images. Also defects located closer to the top surface fail to appear in the reconstructed images. Plane wave imaging technique proposed in this study, on the other hand is able to significantly reduce the incoherent noise as well as other undesired imaging artefacts. This improves the damage detection capability since the image contrast gets improved significantly. The proposed technique is able to image the cracks located at the shallow depth of the medium and at the same time mapping the aperture facing geometry of the defects present in the simulated concrete medium. The reconstruction of subsurface images using plane wave imaging is done by post-processing the full matrix data and hence does not require the phased arrays which can be practically difficult to use on concrete structures.

Modern ultrasonic inspections utilize ever-richer data-sets made possible by phased array equipment. A typical inspection may include tens of channels with different refraction angle, that are acquired at high speed. These rich data sets allow highly reliable and efficient inspection in complex cases, such as dissimilar metal or austenitic stainless steel welds. The rich data sets allow human inspectors to detect cracks with low signal-to-noise ratio from the wider signal patterns. There’s a clear trend in the industry to even richer data sets with full matrix capture (FMC) and related techniques. Convolutional neural networks have recently shown capability to detect flaws with human level accuracy in ultrasonic signals at the B-scan level. To enable automated flaw detection at human-level accuracy for critical applications, these neural networks need be developed to take advantage of today’s rich phased array data-sets. In the present paper, we extend previous work and develop convolutional neural networks that perform highly reliable flaw detection on typical multi-channel phased array data on austenitic welds. The results show, that the modern neural networks can accommodate the rich ultrasonic data and display high flaw detection performance.

Additive manufacturing (AM) is a rising technology bringing new opportunities for design and cost of manufacturing, compared to standard processes like casting and machining. Among the AM techniques, direct energy deposition (DED) processes are dedicated to manufacture functional metallic parts. Despite of their promising perspectives, the industrial implementation of DED processes is inhibited by the lack of structural health control. Consequently, non-destructive testing (NDT) techniques can be investigated to inspect DED-manufactured parts, in an online or offline manner. To date, most ultrasonic NDT applications to metallic AM concerned the selective laser melting process; existing studies tackling DED processes mainly compare various ultrasonic techniques and do not propose a comprehensive control method for such processes. Current researches in the GeM laboratory focus on a multi-sensor monitoring method dedicated to DED processes, with a structural health control loop included, in order to track defect formation during manufacturing. In this way, this paper aims to be a proof of concept and proposes a comprehensive control method that opens the way to in situ ultrasonic control for DED. In this paper, a control method using the phased array ultrasonic testing (PAUT) technique is particularly illustrated on wire-arc additive manufacturing (WAAM) components, and its applicability to laser metal deposition (LMD) is also demonstrated. A specific attention is given to the calibration method, towards a quantitative prediction of the size of the detected flaws. PAUT predictions are cross-checked thanks to X-ray radiography, which demonstrates that the PAUT method enables to detect and dimension defects from 0.6 to 1 mm for WAAM aluminum alloy parts. Then, an applicable scenario of inspection of a WAAM industrial and large-scale part is presented. Finally, perspectives for in situ and real-time application of the chosen method are given. This paper shows that real-time monitoring of the WAAM process is possible, as the PAUT method can be integrated in the manufacturing environment, provides relevant in situ data, and runs with computing times compatible with real-time applications.

The reliable detection of defects is one of the most important tasks in nondestructive tests, mainly in the radiography test (RT) and ultrasonic test (UT). Non-Destructive Testing (NDT) is the most efficient as internal and external discontinuities are inspected while maintaining the target’s original structure (form and function). Therefore, in this paper, the Phased Array Ultrasonic Testing (PAUT) method was applied to propose inspection method that can address certain key PAUT Parameters and image processing to enhance the precision of discontinuities and the reliability of calculations of discontinuity size and characterization and also transfer 2D S-Scan images into 3D images (volumetric scan) which is more reliable and easily interpretation.

Phased array ultrasonic testing, an effective ultrasonic testing (UT) technology, has been widely used in steel inspection because of its high accuracy, sensitivity, and efficiency. However, as its application in as-cast magnesium alloys has just begun, more research is needed. Considering the important role of the gain compensation in quantifying defects in magnesium alloys by ultrasonic phased array technology, the effects of microstructure, the position, size, and overlap of defects, and boundary distance (distance from the defect position to the side surface of the test casting) on gain compensation of as-cast AZ80 and AZ31 magnesium alloys were studied. Results show the gain compensation increases with the increase of grain size. There is a strict linear positive correlation between gain compensation and defect depth, but such relationship no longer exists due to the defects overlap, orientation and boundary distance. In addition, there is a strict linear negative correlation between the gain compensation and defect size.

The application of non-destructive techniques for the evaluation of internal damage in composite materials is a challenge due to their complexity. The aim of this study is to analyse the ability of ultrasonic technique to identify and evaluate manufacturing defects and internal damage in composite laminates. Artificial object inclusions of different shapes, sizes and materials were embedded in carbon fibre reinforced epoxy (CFRP) laminates. Comprehensive investigation of non-destructive evaluation using phased array ultrasonic testing to trace and characterize the embedded defects is presented. Phased array ultrasonic technique was able to precisely locate most of the artificial inclusion in the composite laminates. Nerveless, the shape and size of the inclusions were not accurately determined due to the high signal attenuation and distortion characteristics of the carbon fibre epoxy composite. Furthermore, a major concern affecting the efficient use of composite laminates is their vulnerability to low velocity impact damage. The dynamic behaviour of composite laminates is very complex as there are many concurrent phenomena during composite laminate failure under impact loading. Thus, the practicality of the previous results is demonstrated by the evaluation of impacted carbon fibre reinforced epoxy laminates using ultrasonic testing. The influence of laminate thickness and impact energy on impact damage is also investigated. The performance of phased array ultrasonic testing for the inspection of composite laminates with barely visible impact damage is evaluated. In addition, fibre-reinforced thermoplastic composites are becoming more significant in industrial applications due to their excellent mechanical performance and potential recycling. In this study, impact damage in 3D printed continuous glass fibre reinforced thermoplastic laminates is also analysed. Phased array ultrasonic testing is performed and the amount of damage is quantified in terms of delaminated area.

Dissimilar metal welding that is the joining of two different metals which would not be welded together has been used in nuclear power plants so that the probability of occurrence of cracks that can cause serious accidents is high. Therefore, it is necessary to diagnose and investigate structures with dissimilar metal welds through nondestructive testing techniques. Among them, nondestructive evaluation techniques using phased array ultrasonic waves have been widely used and studied. However, transmitted ultrasound into dissimilar metal welds is split, skewed and distorted due to course grained anisotropy and inhomogeneity. Therefore, there are many limitations in tests using the conventional phased array ultrasonic technique. In this study, the phased array ultrasonic focusing methods such as phase matching method, adaptive focusing method and time reversal method were applied to the nondestructive ultrasonic testing of dissimilar metal welds for detecting internal cracks, and the performance and efficiency of each technique were compared through numerical simulations and experiments.

In this study, ultrasonic testing (UT) is adopted for the non-destructive testing (NDT) of the China Fusion Engineering Test Reactor (CFETR) vacuum vessel (VV) welding. Coarse grain and anisotropy of austenitic stainless steel welding pose great challenges on traditional UT and linear probes of phased array ultrasonic testing (PAUT) in terms of sensitivity and accuracy. An automatic PAUT system of dual matrix array probe has been recently developed and qualified in ASIPP. In this paper, key parameters of the system and test results obtained on demonstration blocks are introduced. Test results imply high sensitivity and efficiency of the automatic PAUT system, which will be further testified on the NDT of CFETR VV welding.

We investigate the use of phased array ultrasonic testing (PAUT) as an offsite non-destructive quality assurance technique for parts made by selective laser melting (SLM). SLM is a popular additive manufacturing (AM) approach for fabricating high-value metallic components with complex geometries. Slight variations in the laser power during fabrication might lead to internal defect development within the part, which could compromise its mechanical strength and fatigue life. PAUT is employed to detect typical internal porosity generated in Inconel 625 samples due to laser power fluctuation during SLM. The typical defect size, shape, and distribution are first identified using metallography and X-ray computed tomography (XCT). B-Scan images of the defect region is then generated experimentally using a 5-MHz linear UT phased array probe. Finite elements simulate wave propagation using geometries obtained from XCT images. The simulation results are compared to the experimental imaging of large defect regions and then used to generate total focusing method images of isolated clusters of 50–200 μm defects. The testing technique illustrates a successful application of PAUT for quality inspection of SLM parts.

This paper presents an advanced methodology for the detection of damage in aircraft composite materials based on the sensor fusion of two image-based non-destructive evaluation techniques. Both of the techniques, phased-array ultrasonics and infra-red thermography, are benchmarked on an aircraft-grade painted composite material skin panel with stringers. The sensors systems for carrying out the inspections have been developed and miniaturized for being integrated on a vortex-robotic platform inspector, in the framework of a larger research initiative, the Horizon-2020 ‘CompInnova’ project.