Development of Nondestructive Testing Techniques for Gas-Cooled Plasma-Facing Components

The main objectives of applying NDT techniques are to ensure the quality of an assembly or a part according to a given specification including known acceptance criteria. It generally enables not only to detect an indication, but also to classify it (size, position, nature…). Many non-destructive testing (NDT) techniques are effective in testing welded components. Radiography, ultrasonic testing, penetrant testing and magnetic particle testing are widely used and standardised. Phased arrays, TOFD and multi-elements eddy current are more and more extensively applied. Tomography, acoustic emission, ultrasonic guided waves, laser ultrasonic and optical techniques continue to be a strong topic of interest. Each of these techniques is based on different physical principles to detect defects on the surface of the part or over its whole volume. However, the geometry, physical and material properties of the part being tested are key factors in the applicability and performance of a given NDT technique. To date, the development of reliable NDT methods for additive manufacturing (AM) parts is still a major challenge. The process may generate various defects such as cracks, voids, inclusions and porosities. NDT techniques need to be optimised or developed to address singular features of the AM processes: complex geometry, special internal structures, anisotropic material properties, typical defects. Knowledge of the potential occurring imperfections produced by the various AM process needs to be improved in order to be able to select the best suited NDT techniques.

Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to load-carrying structures in aerospace, wind turbines, transportation, medical equipment and so on. Thus, robust and reliable non-destructive testing of composites is essential to reduce safety concerns and maintenance costs. There have been various non-destructive testing methods built upon different principles for quality assurance during the whole lifecycle of a composite product. This article reviews the most established non-destructive testing techniques for detection and evaluation of defects/damage evolution in composites. These include acoustic emission, ultrasonic testing, infrared thermography, terahertz testing, shearography, digital image correlation, as well as X-ray and neutron imaging. For each non-destructive testing technique, we cover a brief historical background, principles, standard practices, equipment and facilities used for composite research. We also compare and discuss their benefits and limitations and further summarise their capabilities and applications to composite structures. Each non-destructive testing technique has its own potential and rarely achieves a full-scale diagnosis of structural integrity. Future development of non-destructive testing techniques for composites will be directed towards intelligent and automated inspection systems with high accuracy and efficient data processing capabilities.

Friction stir welding (FSW) has dramatically changed how aluminium alloys can be welded. The quality of FS welds is usually excellent, but some imperfections periodically occur. The geometry, location, and microstructural nature of these imperfections bear no resemblance to the imperfections typically found in aluminium fusion welds. Consequently, it has been difficult to identify FS weld imperfections with common non-destructive testing (NDT) techniques. Therefore, further development of NDT techniques must be done to enable the detection of FS weld imperfections. This paper presents an integrated, on-line, NDT inspection system for FS welds, which employs a data fusion algorithm with fuzzy logic and fuzzy inference functions. It works by analyzing complementary and redundant data acquired from several NDT techniques (ultrasonic, Time of Flight Diffraction (ToFD), and eddy currents) to generate a synergistic effect that is used by the software to improve the confidence of detecting imperfections. The system was tested on friction stir welded AA5083-H111 specimens. The results indicate that by combining the output from various NDT processes, an improvement in finding imperfections can be obtained compared to using each NDT process individually. The methodology implemented in the QNDT_FSW system has given good results and improved reliability in the NDT of friction stir welds.

Various nondestructive testing (NDT) techniques are available to evaluate the condition of existing concrete structures. These NDT techniques can help to determine in-situ load carrying capabilities and in turn be used to help develop a cost effective rehabilitation solution. In this project, the four pier caps of Denver Colorado' Quebec Street Bridge over Air Lawn Road were inspected using several different NDT techniques. These tests included: carpenter hammer sounding, Schmidt hammer, and ultrasonic pulse velocity (UPV) testing including tomography. In addition visual testing was used to identify crack patterns and spalling conditions. Contour plotting of the NDT data was completed on individual and combined NDT techniques to better determine the condition of the piers. Equal weighted percentages were assumed in combining the hammer sounding, Schmidt, and direct ultrasonic transmission data. Although hammer sounding and Schmidt rebound techniques were used to determine the condition of the exterior layers of the piers, ultrasound and tomography were used to determine the condition of the interior. Various tomographic slices were completed between adjacent sides and from face to face. After the NDT tests were completed, the data were analyzed, interpreted and recommendations were given to further destructively examine local areas of the piers. Destructive tests included compressive strength, chloride, and petrographic testing. The specific detail of all testing methodologies used in this study will be discussed further along with the specific results for the northwest pier cap.

Advanced characterization technique which is Non-destructive Testing (NDT) technique are required to monitor the testing for physical and mechanical properties of rock. Using Non-destructive Testing technique, the information gather are much faster and easier without any disturbance to the sample test. In rock engineering, the key role in the long term stability are depending on the characteristics of rock and the rock masses. Since the finding of strength parameter are time consuming and very expensive, this research is conducted to perform experimental testing and ultrasonic pulse transmission technique on granite for a sustainable rock testing approach. Through this study, it enables to identify a simple way to predict these strength parameters especially and specifically for Unconfined Compression Strength (UCS) by using Point Load Test (PLT) and Ultrasonic Pulse Velocity (UPV) Test. From this study, the correlation can be made among UCS, point load index, and sound velocity which the empirical formula for point load and the ultrasonic pulse velocity test are UCS = 20.8(Is50) + 2.2 and UCS = 144.68Vp – 684.37 respectively. The ultrasonic pulse transmission technique methods can be used to predict the compressive strength of rock. It can be practically used in the field since the technique are portable and easy to use. By using the least-square regression method, the empirical formula formulated between UPV and UCS values signifies that the correlation coefficient (R2) obtained for the equation is 0.9692 and indicates that both variables have a good agreement relationship.

Concrete is susceptible to cracking and damage under repeated freeze–thaw conditions. Ultrasonic techniques have been widely used as non-destructive testing and evaluation techniques to assess concrete integrity under various damage mechanisms; however, commonly adopted linear ultrasonic (LU) techniques are less effective for identifying microscale damage. Nowadays, non-linear ultrasonic (NLU) techniques are favoured for detecting microscale damage due to their high sensitivity to microcracks. Recently, sideband peak count (SPC)-based NLU techniques have emerged as a robust alternative to traditional NLU methods. In this study, both LU and SPC-based NLU techniques were conducted to assess the damage of mortar specimens that were subjected to different freeze–thaw cycles. The freeze–thaw damage was also evaluated with conventional resonant frequency and compressive strength tests. Results indicate that LU-based technique – ultrasonic pulse velocity (UPV) – performs the worst correlation with the changes in compressive strength of the mortar specimens. The other LU parameter – signal attenuation – shows better result than UPV, exhibiting a similar trend with relative dynamic modulus of elasticity (RDME) from resonant frequency test. The two SPC-based techniques sideband peak count-index (SPC-I) and sideband peak intensity (SPI) are more sensitive to different degrees of frost damage. Specifically, the SPC-I technique correlates well with the change in RDME throughout the testing period. In terms of the mechanical property, SPI performs the best among the three techniques (resonant frequency, SPC-I and SPI), especially for assessing the damage at the early stages when the accumulative damage did not change compressive strength significantly. At later stages as the damage progressed, all three techniques produced reliable results.

Prediction of axial compressive stresses in ultra-high-performance concrete blocks using non-destructive ultrasonic techniques

Diagnosis of Historic Reinforced Concrete Buildings: A Literature Review of Non-Destructive Testing (NDT) Techniques

This paper discusses the possible non-destructive testing (NDT) techniques for a novel bonding quality evaluation technique based on comparison of different inspection methodologies. The goal of this paper is to guide a way for bonding quality evaluation with high reliability by comparing different NDT techniques including ultrasonic, electromagnetic, and thermography. The advantages and limitations of each different NDT technique have been reported systematically. Two case studies have been investigated with two different NDT techniques, namely ultrasonic and induction thermography. The results suggested the limitations and advantages of NDT techniques. In order to compensate the limitations of each technique, data fusion of the selected techniques is proposed.

Non-destructive testing (NDT) techniques for low carbon steel welded joints: A review and experimental study

Comparison and analysis of non-destructive testing techniques suitable for delamination inspection in wind turbine blades

Pulsed eddy current testing (PECT) and electromagnetic ultrasonic non-destructive testing (NDT) techniques are important methods for detecting defects in pressure pipelines. Although these methods have the advantages of no contact requirement, fast detection and simple signal processing, there is a near-surface blind area in electromagnetic ultrasonic detection and pulsed eddy current detection cannot accurately detect deep locations due to the skin depth. However, these two techniques can be combined to potentially overcome their individual limitations. This paper presents an in-depth study of the use of pulsed eddy current testing and electromagnetic ultrasonic non-destructive testing techniques to detect defects in pipelines. Moreover, the basic principles, numerical simulation methods, testing systems and application characteristics of the individual methods and their combined use are discussed.

Structural health monitoring (SHM) is an important aspect of the assessment of various structures and infrastructure, which involves inspection, monitoring, and maintenance to support economics, quality of life and sustainability in civil engineering. Currently, research has been conducted in order to develop non-destructive techniques for SHM to extend the lifespan of monitored structures. This paper will review and summarize the recent advancements in non-destructive testing techniques, namely, sweep frequency approach, ground penetrating radar, infrared technique, fiber optics sensors, camera-based methods, laser scanner techniques, acoustic emission and ultrasonic techniques. Although some of the techniques are widely and successfully utilized in civil engineering, there are still challenges that researchers are addressing. One of the common challenges within the techniques is interpretation, analysis and automation of obtained data, which requires highly skilled and specialized experts. Therefore, researchers are investigating and applying artificial intelligence, namely machine learning algorithms to address the challenges. In addition, researchers have combined multiple techniques in order to improve accuracy and acquire additional parameters to enhance the measurement processes. This study mainly focuses on the scope and recent advancements of the Non-destructive Testing (NDT) application for SHM of concrete, masonry, timber and steel structures.

The objective of this work is to evaluate the reliability of the ultrasonic nondestructive test technique (NDT), for specific test conditions, using POD (probability of detection) curves developed by experimental procedures. Two classes of defects, lack of penetration (LP) and lack of fusion (LF) were intentionally inserted in 24 weld beads belonging to 4 API X70 steel pipeline specimens with an outer diameter of 254mm and wall thickness of 19.05mm. These specimens were inspected using manual and automatic ultrasonic techniques. The results, besides producing real POD curves, showed the superiority of the automatic techniques over the manual test in the probability of detection of these two classes of defects.

The development in materials technology has produced stronger, lighter, stiffer, and more durable electrically insulating composites which are replacing metals in many applications. These composites require alternative inspection techniques because the conventional nondestructive testing (NDT) techniques such as thermography, eddy currents, ultrasonic, X-ray and magnetic particles have limitations of inspecting them. Microwave NDT technique employing open-ended rectangular waveguides (OERW) has emerged as a promising approach to detect the defects in both metal and composite materials. Despite its promising results over conventional NDT techniques, OERW microwave NDT technique has shown numerous limitations in terms of poor spatial resolution due to the stand-off distance variations, inspection area irregularities and quantitative estimation in imaging the size of defects. Microwave NDT employing OERW in conjunction with robust artificial intelligence approaches have tremendous potential and viability for evaluating composite structures for the purpose mentioned here. Artificial intelligence techniques with signal processing techniques are highly possible to enhance the efficiency and resolution of microwave NDT technique because the impact of artificial intelligence approaches is proven in various conventional NDT techniques. This paper provides a comprehensive review of NDT techniques as well as the prospect of using artificial intelligence approaches in microwave NDT technique with regards to other conventional NDT techniques.