In this paper, Monte Carlo simulations are performed based on the two-dimensional Ising model with the objective of matching the simulated magnetic Barkhausen noise (MBN) signals with the measured MBN signals obtained from empirical research on bearing steel of different hardness levels. Firstly, the methods for obtaining simulated MBN signals based on the Ising model are studied. This paper suggests that simulated MBN signals obtained by applying a digital filter to the simulated magnetization curve, both in the time domain and frequency spectrum, are closer to the actual measured signals. Secondly, the influencing factors of the two-dimensional Ising model are studied, including lattice size ( N ), temperature ( T ), neighbor interaction ( J ), external magnetic field ( H ( t )), number of simulation points per period ( P_sim ) and Monte Carlo step ( MCS ). Furthermore, the simulated MBN signals and their feature diagrams under different temperatures and neighbor interactions are plotted. Finally, a method is proposed to match the simulated MBN signals with the actual measured MBN signals using scaling and shifting, reducing the relative error between the simulated and measured MBN signal features to within 7

In this paper, magnetic Barkhausen noise (MBN) and tangential magnetic field (TMF) are employed to quantitatively predict the hardness of bearing steel GCr15. In order to solve the problems that MBN and TMF signals are susceptible to electromagnetic interference (EMI) and sensor vibration during the inspection process, which lead to the decrease of the hardness prediction accuracy, a feature-based abnormal signal elimination algorithm is proposed. The features of MBN and TMF signals are used to determine whether the signals are affected by EMI or sensor vibration. To verify the effectiveness of the algorithm, the multiple linear regression (MLR) and multilayer perceptron (MLP) hardness prediction model are developed based on MBN and TMF features. After removing abnormal signals, the hardness prediction error of MLR model is reduced from 21.39 to 1.25% and the hardness prediction error of MLP model is reduced from 7.75 to 0.13%.

In this paper, magnetic Barkhausen noise (MBN) is employed to quantitatively predict the hardness of GCr15 bearing steel. Firstly, to thoroughly investigate the relationship between MBN signal features and material hardness, a comprehensive study is conducted on multi-feature extraction methods for MBN signals based on time domain, frequency domain and time–frequency domain. Secondly, a novel feature evaluation algorithm is proposed that considers the correlation, stability and discriminability (CSD) of MBN features. This algorithm selects MBN features that are relevant to material hardness, remain stable under the same hardness level, and can distinguish between different hardness levels. Finally, linear regression models and multilayer perceptron models are established for the relationship between MBN features and material hardness. The models built using the features selected by the CSD feature evaluation algorithm demonstrate superior accuracy, with the root mean square error of 1.04 HRC for predicting unknown hardness values.

The challenge for future nondestructive techniques is characterized by the two major demands of the users of ND techniques. One is the detectability of defects getting smaller and smaller, is the earlier detection of damages and the reliable characterization of states or evaluation of quantities describing the quality of the component. The second demand is the application of the n.d. techniques as early as possible in the manufacturing process in order to predict the properties of the final product and to enable the optimization of the process. This second demand and the applicability of electromagnetic and ultrasonic techniques will be addressed by the contribution.

A novel magnetic nondestructive testing method, that is named eddy current magnetic signature (EC-MS) method, is proposed to evaluate the residual strain in low carbon steels. This method relies on characterization of eddy current signals in the impedance plane if low frequency major magnetization is superimposed. To investigate the mechanism of the proposed method, the eddy current magnetic signatures of a set of tensile test specimens are measured, and their relationship to the residual strain is surveyed. The trajectories of the eddy current signals show significant dependences on the residual strain; the EC-MS changes depending on the three residual strain stages, the region just after elastic limit before yield point, the Luders-strain region, and the region after start of work hardening. The EC-MS under elastic strain/stress is measured to investigate the influence of stress on the EC-MS. Numerical calculation is performed considering micro-eddy current field associated with moving domain walls and compared with experimental results to interpret the EC-MS phenomena.

An electromagnetic acoustic transducer (EMAT) design using an air-cored solenoid coil as a pulsed electromagnet is proposed for the high-temperature non-contact monitoring of metal processing, and the operation of a prototype device is confirmed at temperatures ranging from room temperature to 700 °C. The coil generates a biasing magnetic field that allows the device to overcome the Curie temperature limitations of conventional EMATs. Pulse-echo measurements on carbon steel are made at high temperatures, and the superposition of the nth compression method is used as a signal processing technique to confirm that the shear wave velocity decreases with increasing temperature, and it is verified that the EMAT can operate at high temperature.

This paper describes eddy current magnetic signature (EC-MS) method that can evaluate small plastic deformation in carbon steels with high accuracy. In EC-MS method, an incremental magnetic field is superimposed on a magnetization field, and the directions of the incremental field to the magnetization field changes, depending on experimental setups. The objective of this study is to investigate the influence of the measurement conditions on experimental results of EC-MS method. Tensile test specimens are measured by EC-MS method with different directions of the incremental field parallel and perpendicular to the magnetization one. Furthermore, the dependence on the static/quasi-static magnetization field is discussed comparing a continuous waveform of the magnetization field with a stepwise one.

This paper describes the measurement of wall thinning by continuous wave electromagnetic acoustic resonance (CW-EMAR) and pulse wave electromagnetic acoustic resonance (PW-EMAR). Simulated pipe wall thinning specimens are measured. The two methods show accurate results in the areas with a low variation of thickness, and the accuracy decreases when the thickness changes drastically. The two methods are analyzed by using the finite element method. The results show that with the increase of the bottom inclination, the accuracy of the two methods is reduced. For thin specimens, the reason for the larger error of CW-EMAR method is due to that CW-EMAR method is more easily affected by ultrasonic scattering and nonuniform distribution of static magnetic field.

Following the design rules and considering the safety factors, the lifetime of nuclear power plants (NPP), worldwide is expected to be in the range of 40 years. Obviously, within such a lifespan the components and systems under heavy mechanical (static and dynamic pressure, vibration), thermic and irradiation loads, suffer ageing phenomena which are Thermal Ageing, Corrosion, Low Cycle Fatigue (LCF), High Cycle Fatigue(HCF), Very high Cycle Fatigue (VHCF) and Irradiation Damage due to neutrons - and the possible synergy of the phenomena together. However, the electrical power producing utilities as operators of the NPP, perform a 'predictive maintenance', also called 'retrofitting', by timely performing the replacement of especially stressed components. Examples for these replacement procedures are the change of heat-exchangers and parts of the main cooling pipes, like hot knees near heat-exchangers or components of the surge-line in pressurized-water NPP. As the components, which are replaced, always are manufactured according the newest technical state of the art, the retrofitting enhances inherently also the safety standard. In Germany, where due to the Atomic Law, the safety of the plants is asked for, this law - beside economic reasons of a higher technical availability - is the driver for replacement. The IAAEA has introduced safety standards for Ageing Management and according these documents, worldwide most of the atomic energy producing countries have adopted their national guidelines, newly introducing mainly fatigue condition monitoring. The proposed paper discusses, on one hand, the application of the 3MA-strategy (Micromagnetic, Multiparameter, Microstructure and Stress Analysis) on ferromagnetic components and Eddy-Current-based and Ultrasonic techniques on austenitic materials for early-characterizing fatigued microstructures - before cracking and, on the other hand, characterization of irradiation damage in pressure-vessel steels.

Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness.

This paper reports on the determination of applied stress using Magnetic Barkhausen Noise (MBN). Effective damping in Barkhausen noise influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile strain variation. After experimental studies, the skewness of MBN distribution profile is presented as a new feature for applied stress characterizaton. A non-linear behaviour of this signature and an independence of the excitation conditions have been found and is discussed. Domain wall (DW) energy, characteristic relaxation time and distance between pinning edges of the DW are considered as the reason of the phenomenon. Skewness presents its robustness to excitation parameters and ability for measuring applied stress.

When designing a weld, it is often desirable that the root side has a greater or at least the same fatigue life as the toe side.