Evaluation of Depth Size Based on Layered Magnetization by Double-Sided Scanning for Internal Defects.

The quantitative evaluation of defects is extremely important, as it can avoid harm caused by underevaluation or losses caused by overestimation, especially for internal defects. The magnetic permeability perturbation testing (MPPT) method performs well for thick-walled steel pipes, but the burial depth of the defect is difficult to access directly from a single time-domain signal, which is not conducive to the evaluation of defects. In this paper, the phenomenon of layering of magnetization that occurs in ferromagnetic materials under an unsaturated magnetizing field is described. Different magnetization depths are achieved by applying step magnetization. The relationship curves between the magnetization characteristic currents and the magnetization depths are established by finite element simulations. The spatial properties of each layering can be detected by different magnetization layering. The upper and back boundaries of the defect are then localized by a double-sided scan to finally arrive at the depth size of the defect. Defects with depth size of 2 mm are evaluated experimentally. The maximum relative error is 5%.

Mechanism of Magnetic Flux Leakage Detection Method Based on the Slotted Ferromagnetic Lift-Off Layer.

Magnetic flux leakage (MFL) testing is widely used in non-destructive testing of ferromagnetic components. In view of the serious attenuation of the leakage magnetic field (LMF) caused by the transmission of LMF in the lift-off layer between the measuring point and the workpiece, this paper introduces an MFL detection method based on the slotted ferromagnetic lift-off layer (SFLL). The conventional non-ferromagnetic lift-off layer is changed to a ferromagnetic lift-off layer with a rectangular slot. The magnetic sensor is fixed above the slot and scans the workpiece together with the lift-off layer. First, the detection mechanism of the new method was studied by an equivalent LMF coil model. The permeability perturbation effect and the magnetization enhancement effect were analyzed in the new method. Based on the detection mechanism, the lift-off tolerance of the new method was investigated. Then, the LMF enhancement and lift-off tolerance of the new method in the steel plate detection model were studied. Finally, experiments were conducted to compare the new method with the conventional method. The simulation and experimental results show that the slotted ferromagnetic lift-off layer enhances the amplitude of the MFL signal and is tolerant to the lift-off value. This method provides a new idea for optimizing the design of the MFL sensor and improving the sensitivity of MFL detection at a large lift-off value.

Mechanism of Magnetic Permeability Perturbation in Magnetizing-Based Eddy Current Nondestructive Testing.

DC magnetization is generally considered to suppress the usual local magnetic permeability variation and increase the penetration depth for magnetizing-based eddy current testing (MB-ECT) of ferromagnetic materials. In fact, such simple explanations lead to rough nondestructive evaluation and cause new neglected non-uniform magnetic characteristics. Hence, the "perturbation" of the internal magnetic field variation is analyzed using a magnetic dipole model and the mechanism of magnetic permeability perturbation in MB-ECT is revealed. The theoretical analysis and simulations show that a significant permeability perturbation always appears around a defect and presents opposite features with strong and weak magnetization. Furthermore, experimental results indicate that the hidden signal component arising from the local permeability perturbation is critical for both far-side surface and near-side surface defects in the MB-ECT method.

A Displacement Sensing Method Based on Permanent Magnet and Magnetic Flux Measurement.

This paper proposes a displacement sensing method based on magnetic flux measurement. A bridge-structured magnetic circuit, formed by permanent magnets and two ferromagnetic cores, is designed and discussed. The analyses of the equivalent magnetic circuit and three-dimensional finite element simulations showed that the magnetic flux density changes linearly with the reciprocal of the sum of a constant and the displacement. A prototype sensor of the bridge structure is developed that consists of four permanent magnets as excitation, a Hall sensor as reception, and two ferromagnetic cores as the connection. Experiments have validated the feasibility of this method. The measured results show a good linearity between the sensor's output and the reciprocal of the sum of a constant and the displacement, with a correlation coefficient greater than 0.9995 across different measurement ranges. Additionally, the measured results significantly indicate that the proposed sensor is compatible with different ferromagnetic materials with a worst-case error of less than 5%. The proposed sensor has the advantages of low cost and good linearity; however, the test object is limited to ferromagnetic materials.

An Online MFL Sensing Method for Steel Pipe Based on the Magnetic Guiding Effect.

In order to improve the sensitivity of online magnetic flux leakage (MFL) testing for steel pipe, a sensing method based on the magnetic guiding effect is proposed and investigated in this paper. Compared to the conventional contact sensing method using a non-ferromagnetic support, the proposed method creatively utilizes a ferromagnetic one to guide more magnetic flux to leak out. Based on Hopkinson's law, the principle of the magnetic guiding effect of the ferromagnetic support is theoretically illustrated. Then, numerical simulations are conducted to investigate the MFL changes influenced by the ferromagnetic support. Finally, the probe based on the proposed method is designed and developed, and online MFL experiments are performed to validate the feasibility of the proposed method. Online tests show that the proposed sensing method can greatly improve the MFL sensitivity.

A Lift-Off-Tolerant Magnetic Flux Leakage Testing Method for Drill Pipes at Wellhead.

To meet the great needs for MFL (magnetic flux leakage) inspection of drill pipes at wellheads, a lift-off-tolerant MFL testing method is proposed and investigated in this paper. Firstly, a Helmholtz coil magnetization method and the whole MFL testing scheme are proposed. Then, based on the magnetic field focusing effect of ferrite cores, a lift-off-tolerant MFL sensor is developed and tested. It shows high sensitivity at a lift-off distance of 5.0 mm. Further, the follow-up high repeatability MFL probing system is designed and manufactured, which was embedded with the developed sensors. It can track the swing movement of drill pipes and allow the pipe ends to pass smoothly. Finally, the developed system is employed in a drilling field for drill pipe inspection. Test results show that the proposed method can fulfill the requirements for drill pipe inspection at wellheads, which is of great importance in drill pipe safety.

Ultrasonic detection method based on flexible capillary water column arrays coupling.

Conventional water immersion ultrasonic testing faces limitations due to factors such as environmental conditions, workpiece dimensions, corrosion, and resource wastage. Contact-based coupling methods, which employ coupling media or specific coupling structures, offer a convenient approach to coupling acoustic waves and reduce signal attenuation. However, these methods are time-sensitive and lack adaptability to uneven surfaces, particularly when dealing with workpieces featuring subtle undulations, resulting in significant signal decay. This paper presents an ultrasonic coupling method based on a flexible capillary water column array. By employing a stable and flexible water column array within the micro-channels as the coupling medium, stable contact-based transmission of ultrasonic signals is achieved. The influence of water column array unit dimensions and array structures is explored through theoretical analysis and experimentation, demonstrating lower energy attenuation compared to reductions in water column area. Notably, the tests revealed the method's adaptability at oblique angles below 20°, which surpasses the performance of submerged detection at similar angles. This research presents an innovative and stable approach for contact-based ultrasonic coupling testing, particularly in scenarios involving dynamic contact scanning between ultrasonic waves and workpieces.

A Review of Magnetic Flux Leakage Nondestructive Testing.

Magnetic flux leakage (MFL) testing is a widely used nondestructive testing (NDT) method for the inspection of ferromagnetic materials. This review paper presents the basic principles of MFL testing and summarizes the recent advances in MFL. An analytical expression for the leakage magnetic field based on the 3D magnetic dipole model is provided. Based on the model, the effects of defect size, defect orientation, and liftoff distance have been analyzed. Other influencing factors, such as magnetization strength, testing speed, surface roughness, and stress, have also been introduced. As the most important steps of MFL, the excitation method (a permanent magnet, DC, AC, pulsed) and sensing methods (Hall element, GMR, TMR, etc.), have been introduced in detail. Finally, the algorithms for the quantification of defects and the applications of MFL have been introduced.

Circular RNA circ_PVT1 induces epithelial-mesenchymal transition to promote metastasis of cervical cancer.

Cervical cancer is one of the most common gynecological malignant tumors. At present, it has been confirmed that the occurrence and development of cervical cancer is related to human papillomavirus infection. As a new regulatory molecule and research hotspot, circRNA is abnormally expressed in tumors and other diseases, and is expected to become a new biomarker for diagnosis and prediction of tumor occurrence and development. In this research, bioinformatics analysis and RT-PCR analysis showed that hsa_circ_0009143 (circRNA_PVT1) was up-regulated in cervical cancer. Knockdown of circRNA_PVT1 inhibits the migration and invasion of cervical cancer cells and would prevent pulmonary metastasis. Overexpression of circRNA_PVT1 induced migration and invasion of cervical cancer cells, which would result in the promotion of pulmonary metastasis. Finally, we found that circRNA_PVT1 can induce EMT of cervical cancer cells via targeting miR-1286 by exosome pathway, which can be a novel mechanism of cervical cancer progression.

[Study on correlation of soil nutrients and content of active constituents in root of Rumex gmelini].

OBJECTIVE: To provide scientific basis for the selection of agrotype and property fertilization for Rumex gmelini cultivated in compliance with good agricultural practice (GAP). METHOD: HPLC method was applied to determinate the content of seven active constituents (resveratrol, polydatin, chrysophanol 1-glucoside, nepodin, emodin, chrysophanol and physcion) of annual R. gmelini. And the correlation between soil nutrients and content of active constituents in the root of R. gmelini were analyzed by stepwise regression analysis. RESULT: Seven regression equation were established. The statistic significance was found in three of them. CONCLUSION: The soil with high total K level is not suitable for R. gmelini cultivation. But the higher available N, available P, available K level of soil is suitable.

[Study on the optimal harvesting time of Rumex gmelini by analyzing the contents of principal components].

OBJECTIVE: To establish a method used for optimization of harvesting time and determine the best time for harvesting Rumex gmelini. METHOD: An HPLC method was applied to determinate the contents of seven active constituents(resveratrol, polydatin, chrysophanol 1-glucoside, nepodin, emodin, chrysophanol and physcion)of R. gmelini at different development stage. The result was analyzed by principal component analysis. RESULT: The accumulation of active constituents showed a regular pattern. CONCLUSION: The best harvesting time of R. gmelini is early July.

[Effects of light intensity on resveratrol and polydatin production in Rumex gmelini root].

The study under controlled conditions showed that short-term shading resulted in the increase of resveratrol and polydatin contents in Rumex gmelini root, while long-term shading led to the decrease of them. The increase and decrease were more obvious with increasing shading degree and time. The production of resveratrol reached the maximum in August, while that of polydatin was in September. Shading had a negative effect on the resveratrol and polydatin accumulation in R. gmelini root, but severe shading at the late growth period of R. gmelini increased the production of resveratrol and polydatin.