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Image quality of the radiographs. The DIN62AL 10 ISO 16 wire penetrameter on an ≈ 4.87-mm-thick Ti-6242 plate. Both CNR + and CNR - are shown, and the radiographs are cropped to approximately 150 × 220 pixels.
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This article presents an algorithm that handles the detection, positioning, and sizing of submillimeter-sized pores in welds using radiographic inspection and tracking. The possibility to detect, position, and size pores which have a low contrast-to-noise ratio increases the value of the nondestructive evaluation of welds by facilitating fatigue li...
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Residual stress assessment is a key factor in engineering design owing to its impact on engineering properties of materials, structural components and welded joints. In dissimilar welding, residual stresses arise due to both the welding process itself and the different coefficients of thermal expansion of the two welded materials. The longitudinal...
Citations
... Radiography testing using X-rays is a common method for detecting voids, cracks, inclusions and various types of fibre orientation. An important advantage of this method is the ability to detect defects at a level of 50 µm [13]. Thermographic testing using heat is based on the change in thermal conductivity at the location of the defects. ...
This paper presents results of ultrasonic non-destructive testing of carbon fibre-reinforced plastics (CFRPs) and glass-fibre reinforced plastics (GFRPs). First, ultrasonic C-scan analysis was used to detect real defects inside the composite materials. Next, the composite materials were subjected to drilling in the area of defect formation, and measured forces were used to analyse the drilling process using recurrence methods. Results have confirmed that recurrence methods can be used to detect defects formed inside a composite material during machining.
... ✓/X No information available [17] >45 Digital Radiographic [35] Real-time radiography (RTR) [36] Compared to conventional radiography, digital data are generated during X-ray penetration in the sample [36]. ...
In Wire and Arc Additive Manufacturing (WAAM) and fusion welding, various defects such as porosity, cracks, deformation and lack of fusion can occur during the fabrication process. These have a strong impact on the mechanical properties and can also lead to failure of the manufactured parts during service. These defects can be recognized using non-destructive testing (NDT) methods so that the examined workpiece is not harmed. This paper provides a comprehensive overview of various NDT techniques for WAAM and fusion welding, including laser-ultrasonic, acoustic emission with an airborne optical microphone, optical emission spectroscopy, laser-induced breakdown spectroscopy, laser opto-ultrasonic dual detection, thermography and also in-process defect detection via weld current monitoring with an oscilloscope. In addition, the novel research conducted, its operating principle and the equipment required to perform these techniques are presented. The minimum defect size that can be identified via NDT methods has been obtained from previous academic research or from tests carried out by companies. The use of these techniques in WAAM and fusion welding applications makes it possible to detect defects and to take a step towards the production of high-quality final components.
... The vision was to obtain a high degree of generality of the evaluation by naturally dividing the problem into simple sub-problems, that is, the evaluation is general in the small but the sum is complex. The idea was to get inspiration to the new custom reconstruction algorithms from 3D-point reconstruction [1,2] and dynamic tomography [3]. ...
In this study techniques, setups, and procedures for in-situ (as built, layer by layer) X-ray nondestructive evaluation of metal components 3D printed with powder bed fusion or directed energy deposition have been explored,. Mathematical models have been utilized on order to estimate the applicabiliiy of the proposed techniques. Simple experiments have been conducted in order to verify some, far from all, of the requirements and assumptions. Both the possibility to utilize the built in electron beam in the powder bed fusion electron beam melting machines as the source producing X-rays as well as the option to utilize external X-ray sources for the case of the directed energy deposition processes have been explored. A proposed concept for backscattered X-ray imaging with an X-ray source has been simulated as seems promising for the application of in-situ layer-by-layer detection and depth positioning of small gas pores. A transmission X-ray imaging concept, less explored, has also been proposed.
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... The degree to which the defects reduce the residual strength is an important basis for the prediction of fatigue life of gas turbine blade [5][6][7][8][9]. Thus, to analyze the residual strength and predict the fatigue life of gas turbine blade, the three-dimensional feature of defect should be quantitatively characterized, such as size, location [10]. ...
During the manufacturing and service process of turbine blades, various types of defects may be formed and bring huge threat to the safe operation of gas turbine. However, if qualifying the turbine blade only by the existence of defects, it will lead to the unavoidable large waste. Preferably, it should determine whether the turbine blades with defects could be in safe service for some period of time. Therefore, the residual strength and fatigue life should be analyzed and predicted based on the three-dimensional feature of defect, such as size, location. Considering the characteristics of shape (free-from surface) and material (high density superalloy), the radiographic imaging based techniques could be used in the non-destructive testing of turbine blades. For one thing, although the industrial computed tomography can obtain the three-dimensional feature of defects, the low efficiency and high cost may limit its practical application. For another, the projective nature of digital radiographic imaging technique results in the unavailability of geometric parameter in the transmitting direction and brings difficulty to the three-dimensional characterization of defect. Aiming at this critical issue, a new method based on the determination of mapping relationship between the thickness of material and the gray value of image is presented in this paper. By acquiring the thickness of two defects in a gas turbine blade, the three-dimensional geometric parameter (volume) can be calculated. Finally, the accuracy of the proposed method is verified using a test specimen. In comparison with the industrial CT, the proposed method could have relative high efficiency and low cost in the application of the three-dimensional quantitative characterization of defects for gas turbine blades.
... usability. Compared to common ultrasonic [4,5] and X-ray [6,7] techniques, eddy current testing (ECT), which operates on the principles of electromagnetic induction, has many advantages such as its efficiency, low cost, noncontact nature, implementation and so on. Currently, ECT has been widely accepted as a desirable technique for characterization of defects in metallic parts [8][9][10]. ...
Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances.
Welding radiographic image analysis (WRIA) is a key technology for welding automated non-destructive testing. Although there already exist some valuable surveys on WRIA, they do not provide a systematic overview of the challenges faced by WRIA and lack a careful distinction and comparison of the core feature techniques in WRIA. With the rapid development of the WRIA area, it is both urgent and challenging to comprehensively review the relevant studies. Therefore, this paper provides an extensive review of 164 papers published in the recent quarter century (1997–2021) ever since its first coined. Three key aspects, namely the challenges faced by WRIA, the evolutionary paths involved in the technology, and the specific application tasks are further discussed in detail. At last, potential future perspectives for WRIA are explored in terms of problem setup, technical improvement, and humanistic care, so as to provide useful insights to both academic researchers and industrial practitioners.
During the manufacturing and service process of gas turbine blades, various types of defects may be formed and bring huge threat to the safe operation of gas turbine. To confirm whether the gas turbine blades with defects could be in safe service for some period of time, the residual strength and fatigue life of gas turbine blade should be analyzed and predicted based on the 3D spatial position of defect, which significantly determines the degree of effect on the strength of gas turbine blade. Considering the characteristics of shape (free-from surface) and material (high density superalloy), the digital radiographic imaging techniques could be used in the non-destructive testing of gas turbine blades. However, the projective nature of digital radiography (DR) technique results in the unavailability of position in the transmitting direction of X-ray beam and brings difficulty to the 3D characterization of defect. Aiming at this critical issue, based on the exploration of the changing rule for the projection of a point feature relative to the irradiating angle, a new method is presented to obtain the 3D spatial position of defect. Finally, the accuracy of the proposed method is validated using a metrological computed tomography (CT) system. It can be learned that the proposed DR based method could obtain the 3D spatial position of defect with a relative error less than 2%. The 3D spatial position of defect could be used in the following residual strength analysis and fatigue life prediction of gas turbine blade.
In this chapter, relevant applications on X-ray testing are described. We cover X-ray testing in (i) castings, (ii) welds, (iii) baggage, (iv) natural products, and (v) others (like cargos and electronic circuits). For each application, the state of the art is presented. Approaches in each application are summarized showing how they use computer vision techniques. A detailed approach is shown in each application and some examples using Python are given in order to illustrate the performance of the methods.
The uncertainty problem in sensor track to local track association is a difficult problem in distributed sensor networks, particularly when there is a big difference of sensors’ tracking performance. To solve this problem, a weighted fuzzy track association (FTA) method based on Dempster–Shafer theory is proposed. In the proposed method, five characteristics of sensor tracks from different sensors are established, and meanwhile their belief functions are defined to determine the corresponding beliefs. Considering the different effects of sensor tracks on track association, the reliabilities of sensor tracks are further presented and their magnitudes can be calculated by the combination belief function defined.Then, these reliabilities are used to reconstruct the fuzzy association degrees by the FTA method. The proposed method has an advantage that it can dynamically allocate the weight of each sensor track in association decision according to its characteristics. The performance of the proposed method is evaluated by using two experiments with simulation data in manoeuvring and uniform situations. It is found to be better than those of other two track association methods in tracking accuracy.
In this chapter, relevant applications on X-ray testing are described. We cover X-ray testing in (i) castings, (ii) welds, (iii) baggage, (iv) natural products, and (v) others (like cargos and electronic circuits). For each application, the state of the art is presented. Approaches in each application are summarized showing how they use computer vision techniques. A detailed approach is shown in each application and some examples using Matlab are given in order to illustrate the performance of the methods.
