X-ray Nondestructive Testing Research Articles

Failure Analysis of Girth Weld Cracking in Gas Transmission Pipelines Subjected to Ground Subsidence and Traffic Loads.

Girth welds are weak points in pipelines, and failures occur frequently. In a gas transmission pipeline, a girth weld experienced cracking, prompting a failure analysis using experimental methods and finite element analysis (FEA). Experimental results showed that X-ray non-destructive testing (NDT) revealed cracks, porosity, and lack of fusion in the girth weld. However, the hardness and microstructure of the material showed no abnormalities. During operation, the pipeline experienced an increase in soil cover and was subjected to ground subsidence and vehicle loads. Finite element analysis was conducted on the defective girth weld under different conditions, including varying soil cover depths, different levels of subsidence, and varying vehicle loads, to examine the pipeline's stress response. The results indicated that the combination of soil cover, subsidence, and vehicle loads led to pipeline failure, whereas none of these factors alone was sufficient to cause girth weld failure. To prevent such failures from occurring again, the following measures are recommended: strengthen on-site welding quality control of girth welds, conduct inspections for defects in girth welds of in-service pipelines, and promptly address any defects that exceed acceptable limits.

A Geant4-based Monte Carlo X-ray imaging simulation platform

X-ray digital radiography plays a pivotal role in accessing the internal structure of objects. Nevertheless, key imaging parameters, such as source-to-target distance or number of projected images needed for three-dimensional construction, mostly rely on real-life trials thus increasing radiation exposure risks. This paper introduces a recently developed software platform known as GMAX (Geant4-based Monte Carlo Advanced X-ray) that helps addressing above issues from a simulation perspective. GMAX employs Geant4, a Monte Carlo simulation code at its core and facilitates high-fidelity X-ray imaging, requiring no prior user experience. Compared to CAD models that only reflect object's geometrical information, GMAX simulates how objects interact with photon and can accurately evaluate important imaging parameters, such as target object to detector distance. It also provides three-dimensional construction functionality for images and therefore could be used as an effective tool for X-ray non-destructive testing and inspection.

Investigating the impact of X-ray irradiation on the SF6 gas discharge in GIS equipment

ABSTRACT Gas Insulated Switchgear (GIS) is extensively utilized in power grid systems. However, the existence of numerous photoelectrons in the SF6 gas during X-ray non-destructive testing in ultra-high-voltage (UHV) GIS equipment may induce gas streamer discharge in a strong electric field. To address this issue, in this work, the impact of X-ray irradiation on the SF6 gas discharge in GIS equipment was systematically analyzed. Firstly, one GIS engineering mode with a three-dimensional electric field was established, and a physical GIS model was established by the Geant4 and Garfield++ codes. Secondly, the electrons’ ionization, and multiplication processes in SF6 gas during the X-ray irradiation were studied. Finally, a test platform with an equivalent electric field tube, which had the same intensity as in the GIS equipment, was established to verify the physical GIS model. X-ray beams with 0.1 MeV, 0.16 MeV, 0.3 MeV, and 1.25 MeV energy were used during the test process. From our analysis, it was concluded that X-ray irradiation can cause an electron avalanche in SF6 gas and the intensity of the avalanche is low, which is far away from the appearance of the streamer discharge.

Controlled mechanism of dynamic behavior of water-based ultrasonic cavitation in coal pore microstructure

Coal pores are sealed as a result of water lock effect, which in turn inhibits coalbed methane (CBM) from desorbing and diffusing. It seriously restricts the efficient development of CBM in the complex geological environment. Relieving pore water lock (RPWL) in coal reservoirs is a scientific problem that puzzles CBM development. Currently, the widely-interested technology of enhancing coalbed methane recovery (ECBM) can not effectively break through the pore water lock. Ultrasonic cavitation can generate shaped charge micro-jets, high temperature, and high pressure, which may be a potential strategy to realize RPWL in coal reservoirs. It has been maturely applied in numerous fields such as medicine, chemical industry, and manufacturing industry. Therefore, water-based ultrasonic cavitation-enhanced coalbed methane recovery (WUC-ECBM) was proposed in this study. This technology has enormous application potential for the efficient and green development of CBM. However, as the theoretical key to the successful application of WUC-ECBM, its RPWL mechanism is still blank. In this paper, X-ray nondestructive testing and fluid invasion methods were used to reconstruct the digital model of coal pore microstructure. Through ultrasonic cavitation numerical simulation, the dynamic behavior mechanism of water-based ultrasonic cavitation was studied in coal pore systems, revealing the microscopic RPWL mechanism of WUC-ECBM. Results show that low metamorphic coal has a larger and fuller pore system, which reflects a stronger topological advantage. Small pores and throats are the main locations of ultrasonic cavitation. This spatial feature is consistent with pore water locking phenomenon. During the formation of a cavitation bubble, ultrasonic energy instantly weakens the surface tension of the water film and activates RPWL. When the cavitation bubble collapses, the micro-jets, high temperature, and high pressure wreak mechanical damage and thermal shock to pore water, accelerating the RPWL process. Ultrasonic frequency affects the cavitation threshold. Increasing ultrasonic power will significantly boost cavitation intensity in pores, particularly in high metamorphic coal. The research results contribute to the green, efficient and intelligent development of CBM in the harsh geological environment, and provide theoretical guidance for WUC-ECBM.

Determining the technological parameters of electron-beam welding of high-strength titanium alloys

It is usually quite difficult to carry out deep penetration of thick-walled products from titanium alloys using conventional welding technologies. In this study, it was proposed to use electron beam welding under high vacuum conditions for the realization of 40 mm thick melting of VT23, VT3-1 alloys. This paper considers the possibility of obtaining high-quality welded joints from high-strength titanium alloys having (a+β) two-phase structures. For the implementation of research works, samples were made from selected materials, samples were welded according to the specified modes, metallographic analysis was performed, and the level of mechanical properties was determined. The research results were verified under laboratory conditions. The technological features of the processes of electron-beam welding of products with a thickness of 40 mm were considered; the parameters affecting the weldability of titanium alloys and their structure were determined. The welded samples were checked by X-ray non-destructive testing, the microstructure of the welds was studied, and the physical and mechanical properties of the welded joints were checked. It was established that a feature of titanium alloys VT3-1, VT23 is the need for heat treatment after welding under the base metal regimes to improve the characteristics of the welded joint. The resulting strength limit of the alloys after heat treatment reached values of 1250 MPa and more, while the impact toughness was at the level of 48–50 J·cm-2. Modeling the welding process has made it possible to ensure the reproducibility of the characteristics of the welded joint at a level close to that of the base metal, to increase the quality indicators of welded joints, and to reduce the time required to test the technology. The studies of simulator samples showed compliance of the quality of welded joints with the predefined parameters.

Effect of Humidity Exposure on Microstructure and Photoluminescence Properties of Polycrystalline CsI(Tl) Screens

CsI(Tl) scintillation screens have been widely applied in X-ray nondestructive testing (NDT) because of their low cost, high scintillation efficiency, and fluorescence guide columnar microstructures. The effect of humidity exposure on the microstructure and photoluminescence properties of polycrystalline CsI(Tl) screens was investigated in this work. The results indicate that the grain diameter of the columnar microstructure increased with increased exposure time in a humid environment. The degree of anisotropy of polycrystalline screens changed from (211) and (310) to (110) orientation with exposure time. FT-IR Spectra of the exposed screens peaked at 3734 cm−1, 3710 cm−1, 3676 cm−1, 3647 cm−1, 3627 cm−1, 3598 c−1, and 3566 cm−1 due to the symmetrical and asymmetrical stretching vibrations of water molecules. In addition, the photoluminescence properties of exposed screens decreased with increased humidity exposure time due to the deliquescence caused by water molecules. After hours of humidity exposure, the photoluminescence and imaging properties of the screens decrease obviously and tend to reduce slowly. The moisture absorption and deliquescence would directly affect the service reliability and the storage lifetime of polycrystalline CsI(Tl) screens.

Adaptive Enhancement of High Greyscale Weld Images Based on the New Pixel Self-transformation Method

X-ray nondestructive testing technology is widely used in the weld detection of oil and gas pipeline industry. The industrial welding manufacturing field produces 12-bit and higher high grey scale images that cannot be displayed directly on an 8-bit display. In this paper, we propose an adaptive pixel self-transformation method for high greyscale weld images. The method takes into account the characteristics of weld images and human perception. Firstly, a high dynamic range tone mapping model is designed, which converts the original RAW data into optical observable data. Secondly, in order to solve the problem that the traditional pixel self-transformation method can only adapt to the input with 256 levels of greyscale and cannot process the high-bit image data. An adaptive high-bit pixel self-transformation is proposed. Finally, the method of this paper was tested on 12-bit X-ray films. The experimental results show that the designed method, which improves the recognizability of weld images and can effectively obtain weld images with outstanding details, is an efficient weld feature enhancement algorithm.

Deep Learning Network of Amomum villosum Quality Classification and Origin Identification Based on X-ray Technology.

A machine vision system based on a convolutional neural network (CNN) was proposed to sort Amomum villosum using X-ray non-destructive testing technology in this study. The Amomum villosum fruit network (AFNet) algorithm was developed to identify the internal structure for quality classification and origin identification in this manuscript. This network model is composed of experimental features of Amomum villosum. In this study, we adopted a binary classification method twice consecutive to identify the origin and quality of Amomum villosum. The results show that the accuracy, precision, and specificity of the AFNet for quality classification were 96.33%, 96.27%, and 100.0%, respectively, achieving higher accuracy than traditional CNN under the condition of faster operation speed. In addition, the model can also achieve an accuracy of 90.60% for the identification of places of origin. The accuracy of multi-category classification performed later with the consistent network structure is lower than that of the cascaded CNNs solution. With this intelligent feature recognition model, the internal structure information of Amomum villosum can be determined based on X-ray technology. Its application will play a positive role to improve industrial production efficiency.

Nondestructive damage evaluation of composites based on terahertz and X-ray image fusion

Inspection of thin and multi-depth delamination and foreign inclusion defects inside glass fiber reinforced polymer (GFRP) composites is a challenge for traditional non-destructive testing (NDT) techniques. Terahertz (THz) and X-ray computed tomography (CT) are two prevalent NDT methods, which also have their unique advantages and relative weakness individually. Specifically, in our previous study, it is found that THz NDT method has a higher contrast and X-ray CT NDT method has a higher resolution for detecting defects in GFRP composites. In this paper, a new fusion algorithm applied to the THz and X-ray CT NDT imaging data, based on the combination of saliency region analysis (SRA) and wavelet based multi-scale transforms (W-MST) is proposed to detect delamination and inclusion defects of GFRP composites. Moreover, the strategy of weighted least square optimization (WLSO) is adopted to eliminate the effects of unregistered images. An exhaustive number of combinations (36 in total) of the proposed fusion algorithm, which include the selection of fusion rules for saliency map, wavelet decomposition levels and wavelet basis functions, have been quantitively compared using objective evaluation indices such as standard deviation (SD) and spatial frequency (SF) to quantify the improvement of detection effect in terms of contrast and resolution. Among them, there are five optimal combinations applicable to five pairs of different source images, and the averages of the SD and SF indicators of fused images have increased by 126% and 190% compared with the source images, respectively. The inspection efficacy of defects using the proposed fusion method has been analyzed visually, showing that the new approach can effectively accentuate the complementary advantages of THz and X-ray NDT methods, resulting in quantifiably improved defect inspections.

Automatic forgery detection for x-ray non-destructive testing of welding

Automatic forgery detection for x-ray non-destructive testing of welding

Study on Linear Segregation of ZL205A Alloy

Linear segregation of high strength aluminum alloy ZL205A castings were studied by X-ray Nondestructive testing, scanning electron microscope and energy dispersive spectrometer. It is found that the linear segregation occurs at the large wall thickness of the casting and/or at the place where the wall thickness is in transition. Segregation element is mainly Cu, which exists as compound θ (Al2Cu) phase. The formation of linear segregation is related to the flow of Cu-rich melt in the late solidification period, while the occurrence of thermal cracks promotes the formation of linear segregation. The formation of linear segregation of the casting can be effectively prevented by eliminating hot spots of the casting, refining crystal grains and increasing solidification speed of the casting.

Development of a CNN edge detection model of noised X-ray images for enhanced performance of non-destructive testing

X-ray non-destructive testing (NDT) is a primary detection technology in industrial fields, providing an effective detection for fragile and complex structures without destructing components. In this study, we adopt the principle of convolutional neural network (CNN) and a Laplacian filter to propose an edge detection model with improved performance. By constructing X-ray image datasets with different noise levels, our proposed CNN model successfully detects fuzzy defects on noised X-ray images, and presents better structure similarity of the detected information compared to conventional edge detection algorithms, Canny and SUSAN. Additionally, the experiment results indicate that the noised training datasets effectively improves the model’s capability of noise resistance in edge detection tasks. Furthermore, the quality of training images significantly affects the performance of the trained model. This study develops a robust edge detection algorithm for low-cost and noise-independent X-ray non-destructive testing technology, providing a meaningful reference in edge detection of industrial X-ray images.

Design of Imaging System and Tomography Detection Method for Radial Tires Structure Under X-Ray Short-Scan Mode

X-ray computed tomography (CT) is a widely popular non-destructive testing (NDT) technology for engineering, which also plays an important role in the NDT testing for radial tires. The steel wires in radial tires are densely arranged and regularly distributed, which usually need high-energy X-rays to penetrate completely. Due to the limitation of tire size and mechanical structure, it is sometimes impossible to scan full-360-degree. In this paper, a scheme of alternating short-scan tomography for circumferential slices on one side of the tire is proposed, and a set of special X-ray NDT instrumentation for radial tires is developed. This solution solves the problem of transilluminating the entire tire in traditional CT scans, and can effectively reduce the maximum penetration energy and radiation dose. Furthermore, the winding problem of high voltage cable and oil cooling service pipeline in the process of rotation is well avoided. Then, a short-scan CT reconstruction method with the offset rotation center is deduced, which can effectively eliminate the image artifacts caused by the connection line between the rotating center of the turntable and the focus of the ray source is not perpendicular to the imaging plane of the detector. Computer simulations and experimental results prove the correctness of the proposed compensation symmetry filling reconstruction algorithm. The proposed method can effectively improve the reconstruction accuracy and suppress the reconstruction artifacts. Based on this, the requirements of mechanical assembly precision can be relaxed, which has a certain engineering significance.

Mechanism of P-wave promoting the solidification feeding in the low-pressure casting of ZL205A alloy

ABSTRACT The effect of P/S-wave on the solidification feeding and the mechanism of vibration promoting the solidification feeding in the low-pressure casting are discussed in the paper. The casting defects were analysed by X-ray non-destructive testing and the buoyancy method. It can be found that the compactness of casting is greatly improved by vibration. In the solidification feeding, according to vibration theory, P-wave will play a decisive role. When the transmission direction of P-wave is perpendicular to the feeding direction, it will lead to the alternation of dense-sparse state in the solidification system. When feeding is blocked, in the sparse state, the diameter of the feeding channel will increase, so that the pressure loss of feeding decreases. At the feeding end, the feeding pressure will make the solidification feeding again. On the contrary, vibration can’t further promote the feeding in the dense state.

Detection of defects in a welded joint by scanning contact potentiometry

ABSTRACT Scanning contact potentiometry (SCP) is a nondestructive method used for defects detection, and for determining the location coordinates of defects in welded joints. This paper evaluates the accuracy of SCP method in detecting defects and localising them in welded steel plates. The effectiveness of the SCP method was evaluated using sample of steel 321 H plates (Chromium–Nickel–titanium stainless steel), where sample plates were welded by means of manual arc welding, dimension of each 200 × 110 × 13.5 mm. After welding, welded sample was inspected using an X-ray radiographic testing system. In order to investigate SCP capabilities, plotted potentiograms were compared with the corresponding X-ray radiograph image. Furthermore, SCP signals were analysed using discrete Fourier transform. Experimental outcomes proved that defects can be detected by SCP technique more accurate comparative to X-ray. Also it is considered an inexpensive comparable to X-ray and ultrasound non-destructive testing methods. As a result, SCP may substitute some destructive or non-destructive testing methods.

X-ray Nondestructive Testing as an Essential Tool during Technology Design and Development of Modern Aircraft Materials

The X-ray nondestructive testing process is carried out by a system which includes an object of control (OC), source of radiation, detector, and operator. Under interaction of radiation with the OC, its radiation image is formed as an X-ray dose distribution in accordance with the OC properties. At this stage, useful information about the OC is formed, which is further partially lost, partially distorted, and veiled with a noise by conversion of a radiation image into an optical one. The optical image is analyzed by an operator, and the result of testing depends on his physical and emotional state. In this article, the step-by-step analysis of the entire radiation monitoring system is performed. The first stage is formation of a radiation image. For the theoretical estimate of the minimum defect size detected by the X-ray testing system, spatial-frequency spectrum analysis was used. The minimum sizes of a defect were established, for which the radiation image will be formed depending on the characteristics of the source of radiation and the OC. The second stage is the transformation of the radiation image into an optical one. We presented the simulation of this process and developed a model of how an operator recognizes the X-ray optical image and makes the decision about the OC condition. The optical image formation was studied and the choice criterion for the radiation energy was determined by using the digital radiography technique.

Modeling of Keyhole-Induced Pore Formation in Laser-Arc Hybrid Welding of Aluminum Alloy with a Horizontal Fillet Joint

A three-dimensional transient model is proposed to investigate the weld pool dynamic behavior in laser + metal inert gas (MIG) hybrid fillet welding of aluminum alloy in the horizontal position, which allows for the joint configuration and coupling of the keyhole, droplet and weld pool as well as the heat and mass exchange between gas and liquid phases and is able to simulate the temperature distribution, fluid flow and formation process of a keyhole-induced pore in hybrid welding with a horizontal fillet joint. The weld porosity is also measured using x-ray nondestructive testing technology. Keyhole behavior and the formation mechanism of keyhole-induced porosity were analyzed. The calculated results are in generally good agreement with the experimental ones. A clockwise vortex always exists at the middle part of the weld pool. The formation and growth of the molten metal bulge on the keyhole wall are responsible for the occurrence of a gas bubble, which has a variation in size and shape and can be split during welding. The keyhole collapses easily at its middle or upper part in horizontal fillet welding, and the capture of the bubble by the upper molten pool boundary enhances the possibility of porosity formation to some degree. The keyhole-induced pore is mainly formed at the regions near the keyhole bottom and the upper fusion line of the weld pool.

Development of X-ray Non-destructive Testing (NDT) Equipment for the Detection of Alien Substances

Development of X-ray Non-destructive Testing (NDT) Equipment for the Detection of Alien Substances

Effect of welding parameters on porosity distribution of dual laser beam bilateral synchronous welding in 2219 aluminum alloy T-joint

The dual laser beam bilateral synchronous welding (DLBSW) for T-joint is limited to develop for the porosity defect in joint. In order to investigate the effect of porosity in T-joint, the DLBSW experiment of 2219 Aluminum Alloy T-joint is carried out. While, the distribution of porosity is scanned by X-ray non-destructive testing (NDT) and the size of porosity is measured by particle size analysis software Nano measurer 1.2. The morphology of pore in fracture and the elemental concentration around the pore are investigated by scanning electron microscopy (SEM) and energy spectrometer (EDS). Furthermore, the analysis results of porosity distribution show that the optimal parameter is 3700 W of laser power and 2.5 m/min of welding rate, under which the number of porosities reaches the minimum. The main factor, caused the fracture of weld seam, is the concentrated porosities in T-joint. In addition, technical porosity is mainly found in the center of the weld seam or at the bottom of the weld seam, and it can be eliminated by improving welding parameters. Metallurgical porosity mainly exists at the edge and the top of the weld seam, including hydrogen porosity and metal vapor porosity which formed by the burning of metal elements.

Simulation and experimental studies of keyhole induced porosity in laser-MIG hybrid fillet welding of aluminum alloy in the horizontal position

The keyhole induced porosity in laser-MIG hybrid fillet welding of aluminum alloy in the horizontal position was investigated with simulation and experimental methods. A three dimensional model is developed, which takes into account geometric feature of horizontal filled joint and the coupling of keyhole, droplet and molten pool. Meanwhile, the major forces are also incorporated in the model. The inclination of heat source is dealt with through rotation of coordinate system. This model is able to calculate the keyhole dynamic behavior and the formation process of gas bubble as well as keyhole induced porosity directly. Also, it can describe the merging and disappearing of bubbles. The weld porosity was examined by the X-ray non-destructive testing. Large weld pool size provides more time for bubble to escape from the molten pool, which is the major factor responsible for the reduction in hybrid welding. Besides, the forward flow caused by the clockwise vortex is weakened, which also plays a positive role in improving the stability of back keyhole wall. The keyhole collapses at the middle part easily in horizontal fillet welding, raising the possibility of forming large pore. Bubble is easy to be captured by the upper weld pool boundary when floating up. With enhancing the welding current, the stability of keyhole is enhanced to some extent and the keyhole induced porosity is reduced.