Currently, analytical methods used to analyze the internal magnetic fields of pipelines seldom consider the leakage flux generated during magnetization. This paper uses the magnetic field segmentation method to establish pipeline axial equivalent magnetic circuit model that considers edge effect magnetic resistance of the detection area.

An electromagnetic pulse-induced acoustic testing (EPAT) method was investigated for length sizing of a debonding between rebar and concrete of reinforced concrete. In EAPT, a pulsed electromagnetic field is applied to vibrate a rebar inside a reinforced concrete and excite elastic waves on a rebar. The elastic wave signal is detected by an acoustic emission sensor to evaluate the properties and condition of the material. By comparing the signal reach time of the elastic waves between specimens with and without a debonding, it was clarified that EPAT can be used as a length sizing method of rebar debonding.

In visualizing inner structures in constructional materials to maintain buildings, it is important to know the size and position of the foreign objects precisely. Spatial resolutions of conductivity distributions obtained using two algorithms for electrical impedance tomography (EIT), one of the simplest and lowest cost methods for non-destructive visualization, were evaluated in terms of the position and size of foreign objects in the specimens. From theoretical and experimental aspects, we obtained that the machine learning-assisted method is more suitable for the EIT algorithm.

In recent years, remanent magnetization after non-destructive inspection using magnetization and after transfer by electromagnet type magnets has become a problem. The influence of external magnetic fields and the demand for demagnetization accuracy in industry will be presented. Therefore, we propose a new demagnetization method and report basic demagnetization experiments and application examples of demagnetization of steel plates.

Silicon steel sheets are widely used as electromagnetic yoke materials in electric motors and generators. These yoke materials have various shapes and are sheared by die presses, etc., but residual stress is generated on the sheared surface. It is known that the magnetic permeability of ferromagnetic materials generally decreases in the residual stress area, and electrical equipment using sheared silicon steel sheets may not produce the designed output. Generally, X-ray test equipment is used to measure the residual stress in the processed part, but a simpler test method is required. In this research, a DC magnetic field is applied to a silicon steel plate, and leakage magnetic flux is generated from the sheared surface. In this paper, a magnetic measurement method is proposed to evaluate the magnetic properties of the sheared surface machined part from the distribution of the leakage magnetic flux. The usefulness of this proposed method is examined by three-dimensional nonlinear magnetic field FEM analysis and verification experiments.

The remote field eddy current testing (ECT) method is known to be effective in detecting external surface defects in ferromagnetic pipes used in petrochemical and steel industries. In previous research, it is clarified that the detection signal is decreased because of the phase angle difference between flux density due to the excitation current and eddy current approaches 180 degrees and cancels each other out. In this paper, an improved remote field ECT probe with ferromagnetic cores inserted inside the excitation and search coils is proposed to deviate phase angle to 180 degrees. The measured sensitivity of the proposed probe is increased by 15% compared with the conventional one. The mechanism is analysed in detail by using 3D nonlinear eddy current analysis using finite element method.

Carburizing and quenching is a type of surface hardening method used to improve durability, such as wear resistance. In carburizing and quenching, only the surface part of the steel material is carburized, making it possible to create a steel material with a hard surface and high toughness inside the steel material. It is important for quality control to measure the hardening layer depth of this carburized material. There is a difference in the hysteresis magnetization curve and electrical conductivity between the carburized layer and the non-carburized layer. Therefore, an electromagnetic inspection method is proposed to measure the depth of the carburized layer by detecting these electromagnetic property differences. In this paper, the usefulness of the proposed method is demonstrated through 3D nonlinear FEM analysis using the play model method, which considers the hysteresis magnetization curves and conductivity of carburized and non-carburized layers. In addition, the Verification experiment is also be conducted.

Nondestructive evaluation (NDE) of Fiber reinforced plastics (FRP) is essential, but challenging owing to the presence of interlaminar interfaces and anisotropy of material properties. The present paper provides for a dual-mode concentrical sensor which may be used for flaw detection in FRP composites using eddy current testing (ECT) and capacitive imaging (CI). Combining ECT and CI techniques provides necessary synergy to detect different types of flaws in electrically conductive and insulating FRP. The proposed sensor consists of a central pancake coil and an outer ring coil. Both coils are printed on a multi-layered flexible PCB such that the windings in each layer provide the same direction of current flow. ECT and CI inspection modalities are realized by establishing proper electrical connections between the coils. Validation of the sensing technique is provided on carbon FRP and glass FRP samples with simulated flaws such as fiber breakage and interlaminar delaminations.

The magnetic Barkhausen noise (MBN) effect, caused by the jumps of the magnetic domains, is demonstrated sensitive to the microstructure of ferromagnetic materials, which makes it a valuable tool for evaluating the micro damage and monitoring the magnetic domain motion. This paper presents a novel 3D numerical model for MBN problem by simulating the motion of magnetic domains during magnetization evolution procedure in the applied magnetic field. The model incorporates the pinning effect of micro damage by spatially randomly distributed barriers, and characterizes the discontinuous domain jumping by comparing the barrier potential and 3D magnetic field simulated with equivalent magnetic polarization method. The proposed model exhibits potential to investigate the MBN phenomenon under complex load and damage conditions and can aid in the optimization of MBN testing devices.

Thermal barrier coating (TBC) is widely used for the purposes of heat insulation and protection in high-temperature structural component such as aero-engine and heavy-duty gas turbine. Aiming at the difficulty of TBC measurement with conventional nondestructive testing method, a new method of surface acoustic wave spectrum analysis based on grating laser generation is proposed for both thickness measurement and delamination defect inspection of TBC. Firstly, the dispersion curve of surface acoustic waves in thermal barrier coating is obtained. Numerical simulation of grating laser acoustic signal and spectrum is then performed. Finally, both thickness measurement and debonding defect inspection of TBC with the proposed method is validated experimentally.

The surface state of metal material is closely related to its service life. Electromagnetic acoustic transducers (EMATs) can realize the nondestructive evaluation of the surface of metal materials because of its non-contact detection characteristics. However, EMAT relies on the principle of electromagnetic induction when exciting ultrasonic waves, so it has the disadvantage of low energy conversion efficiency. In this study, a new design is proposed, and the amplitude of signal is improved by combining linear frequency modulation (LFM) signal with variable-pitch meander coil. The finite element method is used to compare the conventional EMAT with the new designed ultrasonic surface wave EMAT. The numerical analysis results show that the combination of LFM signal and variable-pitch meander coil can greatly improve the amplitude of ultrasonic surface wave.

The detection of cracks with any orientations is a main challenge for the eddy current testing (ECT). In this paper, we propose a flexible printed circuit board (FPCB) probe based on "EIGHT" shape transmitter coils (Tx coils) to solve this problem. Firstly, the detection principle of the probe is given. Secondly, the angle of the Tx coils is designed through experiments, results shows that Tx coils with an angle of 60 is better. Finally, the probe is used for cracks with different orientations. Results show that the probe can detect both 0 - and 90-degree cracks.

The carbon fiber reinforced plastic (CFRP) material is a lightweight, high-strength material that combines carbon fiber and resin and takes advantage of the characteristics of each. This material is widely used in parts that require high strength, such as aircraft, automobiles, and hydrogen tanks. Although this material has high strength, if it is subjected to a large impact, it may cause internal delamination or internal defects. The detecting of these delamination and defects is important for strength and quality assurance of CFRP materials. In this research, the inspection method for detecting backside defects in CFRP plate is proposed from the measurement of the vibration intensity of electromagnetic force vibration. When the proposed measurement method was applied to a CFRP plate with a backside defect, the signal output was large at the defect site, indicating that this measurement method is effective.

This study monitored the Barkhausen noise, the incremental permeability, and the flux density in the same experimental conditions to evaluate the tensile elastic stress influence on magnetic behaviors. Hysteresis loops were reconstructed for all these measurements and used to define common indicators to establish correlations with elastic stress. Simulation tests based on the Jiles-Atherton-Sablik theory were run in parallel to confirm the relations between the elastic stress and assist in investigating the magnetization mechanisms.

In a bid to simultaneously exploit the advantages of pulsed eddy current and pulsed remote-field eddy current for evaluation of buried defects in layered conductors, in this paper, the near- and remote-field pulsed eddy current integrated testing (NRPEC) alongside an axi-symmetric probe has been proposed. Simulations are conducted to reveal the field characteristics underlying the proposed method and analyse the signal response to hidden flaws. In parallel, an NRPEC system has been built up. Based on the images of near-field and remote-field signal features, a fusion algorithm is proposed to fuse the signal features of near-field and remote-field signals for defect testing with the enhanced signal-to-noise ratio. Results from simulations and experiments indicate that based on the fused signal feature, high-accuracy imaging of hidden defects in a double-layer conductor can be achieved via NRPEC with the improved signal-to-noise ratio.

This study evaluates the applicability of using eddy current testing to detect the cracks that appear on the surface of full-tungsten divertor monoblocks. Tungsten blocks with artificial slits were inspected by a differential plus point probe. The results reveal that deep cracks away from the edge can be confirmed well and confirming the amplitude of signals due to an edge would be effective to detect a crack near the edge.

Flow-accelerated corrosion thins the pipe wall and makes a periodic rough surface on the inner pipe wall. The objective of this study is to develop a non-destructive evaluation method of the inner rough surface. To evaluate the roughness of the inner rough surface, a reflected wave from the surface with periodic flaws is acquired, and a frequency spectrum is calculated from the reflected wave. When the flaws are periodic, the spectrum decreases at a specific frequency. This effect on the spectrum is verified by experimental and simulation data, and a method for evaluating roughness is discussed.

The nuclear power equipment contains a large number of dissimilar metal welded structures, which are easy to be damaged, therefore need to be inspected. Detection of defects in dissimilar metal welds can be carried out using non-coaxial Transmitter-Receiver (Tx-Rx) PECT (pulsed eddy current testing) probes. However, considering the diverse materials and complex structure, the detection method needs to be further studied. In this paper, firstly, a simulation model is established to discuss the effects of the material distribution and the position of the excitation coil on the eddy current distribution in the dissimilar metal welded specimens. It is used for probe design. Secondly, the experimental platform is established to verify the simulation results, and the peak value of differential signal is used to analyze weld defects quantitatively.

Incremental permeability measurement is one of the electromagnetic non-destructive tests (NDT) used to characterise industrial parts and evaluate cementation depth, hardness, or residual stresses. Residual stresses are a determining factor for the performance, integrity, and service life of structural steels. A precise assessment of internal stresses makes it possible to anticipate possible breakdown and degradation with disastrous consequences. The first part of the study explores the dependence of the magnetic incremental permeability of a Grain-Oriented Iron-Silicon steel on the amplitude and orientation of applied uniaxial stresses. The second part proposes a model to predict this magnetic signature.