查看更多>>摘要：The Menkaure Pyramid is the smallest of the three main pyramids on the Giza Plateau. Recently, the possibility of a second entrance to the Pyramid has been hypothesized by Van den Hoven, based on similarities between the polished granite blocks covering the Eastern face and the blocks around the main entrance on the Northern face. To test this hypothesis, measurement campaigns using three non-destructive techniques, Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), and Ultrasonic Testing (UST), were carried out on the Eastern face of Menkaure Pyramid. ERT data was obtained from measurements of four long parallel profiles using stainless steel mesh electrodes and inverted using a three-dimensional inversion algorithm. These ERT results guided the more focused grid measurements of a dual-frequency GPR instrument (200/600 MHz antenna) and a 16-channel UST array device. Image Fusion (IF) was utilized to merge the reconstructed ERT, GPR, and UST images, allowing for precise correlation of the detected features from each technique. The images revealed two anomalies directly behind the polished granite blocks, which would indicate the presence of air-filled voids. This interpretation was supported by a series of numerical simulations that considered various possible scenarios under real-world conditions.
查看更多>>摘要：High-energy X-ray microscopy is critical for imaging dense and large-scale materials due to its ability to provide deep penetration and reduced radiation damage. Incorporating phase-contrast imaging enables the visualization of subtle differences in density that traditional absorption techniques cannot detect. Despite these benefits, implementing phase-contrast imaging at high energies (> 70keV) presents significant challenges. The short wavelength of high-energy X-rays reduces spatial coherence and diminishes refraction, thereby limiting phase-contrast effects. The flux of emitted X-ray photons significantly drops at higher energies due to less efficient emission process. All of these challenges degrade X-ray phase-contrast image quality. In this study, we evaluate the feasibility of high-energy X-ray phase-contrast imaging (XPCI) using propagation-based methods. Through rigorous wave propagation simulations, we explored the effects and importance of optimizing the source size and geometrical configurations to enhance image quality. Under optimized conditions at a fourth-generation storage ring, we successfully retrieved phase information of microstructures surrounded by similar materials, such as boron fibers in an aluminum matrix and dual-phase iron. These results provide valuable guidelines for designing high-energy X-ray microscopy experiments, helping to maximize imaging performance while addressing the inherent limitations of using high-energy for XPCI. Ultimately, this study provides essential insights for improving high-energy X-ray microscopy, paving the way for advancing non-destructive testing techniques for a wide range of challenging materials and applications.
查看更多>>摘要：Cone-beam rotational computed laminography (CL) is a highly effective inspection technique for nondestructive testing of objects with a large aspect ratio, such as printed circuit boards (PCB) and insulated gate bipolar transistors (IGBT). However, when scanning objects with a large aspect ratio, the projection data may become truncated, resulting in region of interest (ROI) artifacts in the reconstructed image and reducing the contrast of the reconstructed image. To address this issue, we have proposed a weighted factor that considers the length of the ray within the reconstructed volume and the distance between the X-ray source and the detector bin position. We have also developed a method called ROI conjugate gradient weighted least squares (ROI-CGWLS) to suppress ROI artifacts and enhance the contrast of the reconstructed image in Cone-beam rotational CL. Both simulation and real PCB experimental results demonstrate the effectiveness of the proposed ROI-CGWLS method in suppressing ROI artifacts and improving image contrast and resolution compared to other classical reconstruction methods.
查看更多>>摘要：Photon-counting detectors (PCDs) are an emerging technology that provide energy-selective images for a single X-ray exposure. For studies considering PCDs for industrial non-destructive inspection, presenting a metric describing the imaging efficiency or performance of PCDs is important. In this study, we describe the imaging performance in terms of the detective quantum efficiency (DQE) and report the results of the DQE analysis for a sample PCD using a representative X-ray spectrum (70 kV and 21-mm Al filtration). The PCD, a mosaic of eight small detector modules, employs two adjustable energy thresholds and possesses a function called an anti-coincidence (AC) operation, which sums charges spread over four pixels into a pixel exhibiting the highest charge signal. The DQE measurements confirmed that, without correction for the signal and noise correlation between the energy bins, the DQE could be incorrectly overestimated. The AC or charge-summing operation effectively suppressed the signal and noise correlations between the energy bins, enhanced the modulation-transfer functions and removed the cross-noise-power spectra (cross-NPSs) but increased the normalized NPSs in each energy-bin image, degrading the resulting DQE performance. The performance gap between the measured DQE and theoretical models is discussed. The DQE forms and analysis methodologies presented in this paper will be helpful for researchers seeking to understand PCD-based imaging systems.
查看更多>>摘要：X-ray imaging is broadly applied for defect detection in industry and research. However, traditional X-ray imaging methods struggle to achieve high sensitivity for pixel-level defects (1-3 pixels) in noisy or scattering-dominated environments, such as metal workpieces or thick low-Z materials. To address this, we introduce move contrast X-ray imaging (MCXI), which leverages relative motion between the sample and imaging system to suppress noise and enhance the sensitivity of weak signal detection in complex backgrounds. MCXI has been successfully applied in fields such as biomedical imaging and high-resolution material studies, demonstrating significant noise resistance and sensitivity improvements. This paper extends MCXI to the testing of defects in static samples, aiming to solve the challenges of detecting pixel-level in high-noise and complex backgrounds. Numerical simulations demonstrate MCXI's capability for single-pixel defect detection. Synchrotron radiation experiments validate this technique through quantitative characterization of 1.54-pixel defects (1-μm polystyrene spheres) in low-contrast polyvinyl chloride (PVC) samples, achieving a CNR of 26.12 - representing a 14.04 × improvement over direct projection imaging. The method's industrial applicability is demonstrated through alloy steel pipe testing with 81.2 μm defects (8.12 pixels), where MCXI achieves a CNR of 15.16 (8.1 × enhancement) using laboratory-based X-ray systems. MCXI's seamless integration with both synchrotron facilities and industrial X-ray machines, combined with its noise-resistant characteristics, establishes a universal solution for high-sensitivity nondestructive testing in challenging environments with strong scattering and complex backgrounds.
查看更多>>摘要：Internal local flaws (ILFs) are a principal cause of failure in steel wire ropes (SWRs), and accurately assessing their condition remains a significant challenge. In this article, a novel localization and quantification method based on physical information under a uniform circular array (UCA) is proposed. First, simulations and theoretical analyses are employed to investigate the diffusion pattern of the leakage magnetic field induced by ILFs and the corresponding signal distribution within the UCA. Additionally, a relationship between the spatial position of the ILFs and the physical model is established, enabling precise determination of its location in the SWR cross-section. Quantification of the ILFs is further achieved by applying the physical information obtained to a radial basis function (RBF) neural network. Results from simulations and experiments verify that the proposed method can effectively determine the location of ILFs, maintaining a localization error of less than 1 mm. Moreover, by integrating localization, it enhances quantification accuracy, achieving precision finer than 1 broken wire. The proposed method provides a novel perspective for ELF analysis, contributing to the enhanced safety and reliability of SWRs.
查看更多>>摘要：The addition of WC particles during metal laser cladding (LC) additive manufacturing process not only increases the high-temperature wear resistance but also improves the cracking sensitivity of the cladding. In this paper, LC processes of Fe313 power mixed with different contents of WC were monitored by an acoustic emission (AE) equipment. Combined with the results of temperature and morphology of molten pool and 3D micro-CT imaging results of defects in the cladding, the AE signal response characteristics (Amplitude distributions, AE_(RMS) and AE_(ASL) of AE hit signals and time-frequency decomposition results of AE waveform signals) of crack and pore defects during LC process were obtained. The crack formation time detected by the AE signal was consistent with the monitoring results of the high-speed camera. Furthermore, the number and type of defects monitored by the AE signal were consistent with the results of CT imaging and microscopic analysis. The results indicated that the AE monitoring was a reliable online detection method for LC process. Based on the CT imaging results, the unmelted WC particle in the CT image was separated, and the mass fraction of WC powder was calculated and identified, and the detection error of the mass fraction was only 0.505 %. This study can provide theoretical guidance for defect identification and feedback control in laser additive manufacturing process.
查看更多>>摘要：To prevent yield failure of thin-walled parts, an accurate on-line detection method is crucial. In this study, a laser ultrasonic technology (LUT) was proposed to inspect the acoustic behaviour of AISI type 304 stainless steel under tensile stress across time and frequency domain analysis. The specific acoustic parameters of LUT, including trough arrival time, trough amplitude difference, singular value decomposition entropy (SVDE), peak frequency, bandwidth, and energy distribution, exhibited distinctive characteristics at certain stress levels. Compared with traditional tensile tests, the yield strength determined by laser ultrasonic technology closely matched that obtained using the 0.5 % extension-under-load (EUL) method, with a slight difference of only 3.42 %. Additionally, through box plot analysis, the trough arrival time was confirmed as the optimal index for evaluating yield strength. These changes were further corroborated as corresponding to the yield stage through infrared thermal imaging technology. This research confirms that laser ultrasonic technology is an effective non-contact method for assessing yield strength, providing critical experimental and technical support for material analysis under operational conditions.
查看更多>>摘要：The edge reflection of Lamb waves contains rich information about the structure, and is a promising tool for the structural health monitoring (SHM) of composite laminates. However, related investigation on its applicability in orthotropic composite laminates are still limited. To address this issue, this paper presents a defect localization method based on multipath edge reflected Lamb waves, which can be used for the SHM of square carbon fiber reinforced plastics (CFRP) laminates that have orthotropic material properties. Firstly, the feasibility of using edge reflections to detect defects in orthotropic materials is analyzed, laying the foundation for the construction of a multipath model. A modified dispersion compensation algorithm is then developed based on the equivalent dispersion relations, so as to minimize the influence of the orthotropic property on the signal waveform. On the basis, a four-step implementation process of the detection method is established, including identifying edge reflected wave packets, tracking theoretical virtual wave paths, matching wave packets with virtual paths, and imaging the detection area by fusing images of multipath wave packets. Experiments on three different defect cases show that the method can localize the defect on orthotropic CFRP laminates accurately, even its position is near the edges. Compared with the widely-used delay-and-sum algorithm, the method also performs better in the presence of strong edge reflections, thus can be an efficient SHM tool for the orthotropic CFRP laminates of small sizes.
查看更多>>摘要：This study presents a comparative analysis of magneto-acoustic emission (MAE) signal detection using contact-based electromagnet and non-contact coil setups in pre-stressed Q235 steel samples. The research investigates how these two excitation methods influence MAE signal characteristics, including amplitude, root mean square (RMS), pulse counts, and pulse height distribution (PHD), under varying excitation frequencies (1, 10, and 20 Hz), voltages (10, 20, and 30 V) and tensile strain levels. The results demonstrate that the coil setup provides stable and consistent MAE signals, serving as a reliable baseline, while the electromagnet setup exhibits greater signal sensitivity but introduces variability due to contact-based excitation. The study highlights how contact quality and air-gap effects influence MAE signal variability in electromagnet-based detection of pre-stressed Q235 steel, the need for optimizing excitation conditions and understanding the limitations of electromagnet-based MAE for more reliable non-destructive testing in industrial applications, enabling the broader adoption of MAE-based non-destructive testing in industrial settings.
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