Metal Magnetic Memory Research Articles

Finite Element Simulation and Test of Metal Magnetic Memory Detection of Wire Rope Under Weak Magnetic Field

Finite Element Simulation and Test of Metal Magnetic Memory Detection of Wire Rope Under Weak Magnetic Field

Quantitative Detection of Corrosion State of Concrete Internal Reinforcement Based on Metal Magnetic Memory

Quantitative Detection of Corrosion State of Concrete Internal Reinforcement Based on Metal Magnetic Memory

Study on corrosion damage characterization and tensile strength evaluation for locally corroded bridge steel via metal magnetic memory method

Corrosion is a severe threat to the load-bearing capacity of steel members in bridges. Metal magnetic memory (MMM) is considered a potential method for detecting corrosion damage. In this paper, the SMFL signals HSFy on 27 Q345qD specimens with local corrosion were measured, and then the tensile tests for all specimens were performed. The results show that the crest-trough spacing on the gradient K curves can locate the position and range of corroded region accurately. The difference HSF,my between the maximum and minimum of HSFy signals and the crest-trough difference Kc-t of the gradient K curve can be utilized for the comprehensive characterization of the corrosion damage degree. Finally, the correlation between HSF,my and strength degradation degree η was established to realize the quantitative evaluation of tensile strength. This research serves as a base for corrosion damage characterization and tensile strength evaluation for bridge steel members via the MMM.

Study on the influence of ultrasonic impact treatment (UIT) on stress evaluation of laser cladding coating by using metal magnetic memory technology

The effect of ultrasonic impact treatment (UIT) on stress of laser cladding coating evaluated with metal magnetic memory technology (MMMT) was discussed, so a stress control method was proposed. In this paper, a metal magnetic memory testing device of EMS-2003, a two-channel pen metal magnetic memory probe and a non-ferromagnetic three-dimensional electronically controlled displacement plat form were employed to collect Hp(y) signal defined as the normal component of MMM signal, and tensile test was carried out on LC-50 testing machine. To prove the theoretical analysis, the microstructure and three dimensional surface topography of coating under different repetition rates of UIT were observed by using optical microscope and laser scanning confocal microscopy. The results show that the influence of detection line on Hp(y) signal can be ignored, and the distribution of Hp(y) signals under different tensile loads are all approximately an oblique line, which can be explained by the magnetic dipole model. As tensile load increases, the magnetic field intensity gradient of Hp(y) signal (K) becomes higher, and after coating is in the plastic deformation state, the value of K becomes lower gradually as tensile load increases further. When tensile loads are the same, the value of K becomes higher gradually as the repetition rate of UIT increases. But as repetition rate of UIT increases, the slope of K becomes lower gradually, and the changes on microstructure and deformation caused by UIT are seen as main reasons. At last, the experimental results were theoretically discussed based on the magnetostriction effect, and it was thought that the change on orientation of magnetic domain was the main reason.

Magnetic Signal Characteristics in Critical Yield State of Steel Box Girder Based on Metal Magnetic Memory Inspection

Metal magnetic memory testing (MMMT) is a nondestructive testing technique that can detect early signs of damage in components. Many scholars have studied the effect of uniaxial stress on the self-magnetic-leakage field (SMLF)’s strength. Nevertheless, there is still insufficient research on the combined action of bending and shear. We studied the law of distribution of the magnetic signal, ΔHSF(y), at different stress parts of a steel box girder and the quantitative relationship between the magnetic characteristic parameters and the external load. The results showed that the MMMT could accurately detect the early stress concentration zone (SCZ) and predict the final buckling zone of steel box girders. It could be judged that the corresponding parts of the steel box girder had entered the elastic-plastic working stage by the reverse change of the ΔHSF(y)-F and |HSF(y)|a -F curve trends, this feature could be used as an early warning sign before the steel box girder was deformed or destroyed. The fitted |HSF(y)|ave -F linear expression could be used as the expression between the magnetic signal and the shear capacity. All the evaluation methods were expected to provide a basis for effectively evaluating the stress state of steel box girders with the MMMT method.

Quantitative study of the defects of ferromagnetic materials using the magnetic charge model and particle swarm optimization algorithm

Local defects in components are an important factor responsible for causing damage to steel structures. Hence, metal magnetic memory (MMM) has been used to investigate this issue in recent years. MMM can detect defects based on variations in the self-magnetic leakage of ferromagnetic materials. However, there have been problems of difficulty in quantifying the theoretical parameters of the magnetic charge model and the single characterization of magnetic feature parameters, when using MMM for quantitative analysis of defects. Therefore, the particle swarm optimization (PSO) algorithm was introduced to quicky and accurately quantify the parameters of the magnetic charge model. Theoretical values were compared with experimental data to verify the accuracy of the proposed method. Then, the defect information (defect width and defect depth) was changed and the variation patterns of the magnetic signal and characteristic parameters were analyzed. Finally, the weight of each characteristic parameter was calculated using the entropy value method. A theoretical formula to comprehensively describe defects using multi-feature parameters was proposed. The results show that the theoretical values calculated based on the parameter identification of the PSO algorithm well agreed with the experimental data. Moreover, the proposed formula well described the relationship between the defect width and characteristic parameters. This study is expected to provide a basis for improving the quantitative analysis of MMM.

Influence of tensile stress on magnetic flux leakage signal of ferromagnetic steel after overcoming initial magnetization disturbance

By locally enhancing the intensity of external excitation magnetic field (H0), a relatively stable local flux loop is formed at the test site, which can effectively overcome the problems of random and variable initial magnetization state, small test data base and low signal-to-noise ratio of ferromagnetic specimens in metal magnetic memory testing (MMMT). The results of magneto-mechanical coupling theory and experiment study show that under tensile stress (σt), the ascending part of the magnetization curve is stably constrained within 40 MPa, which is far less than the normal working load, and the descending part of the magnetization curve changes almost linear with the increase of σt. The gradient value of normal component (dHp(z5)/dx) increases by about 105% and the relative gradient value (Δ[dHp(z5)/dx]) increases by about 76% in the range of 0 MPa ≤ σt ≤ 180 MPa with the increase of σt. When H0 reaches 943.4 A/m and 1415.1 A/m, the characteristic parameter namely peak-to-peak amplitude, S(z)p-p, can stably describe σt linearly.

Propagation Characteristics of Magnetic Tomography Method Detection Signals of Oil and Gas Pipelines Based on Boundary Conditions.

The magnetic tomography method (MTM) is a non-contact external inspection method for detecting metal magnetic memory signals. It has great potential for application in long-distance oil pipeline and subsea pipeline inspection. However, the spatial distribution characteristics and propagation laws of magnetic signals are not yet clear, which makes the MTM passive detection. In this study, a three-dimensional mathematical model of the magnetic field distribution of the stress concentration zone outside the pipe was established based on the boundary conditions. For the two cases in which the stress concentration zone was located at the top and bottom of the inner wall of the pipe, the model was solved by finite element analysis. The variation law of the magnetic signal outside the pipe was analyzed, and experiments were designed to verify the model. The results show that the shape of the magnetic memory signal remained unchanged after passing through the pipe wall. As the magnetic permeability of the pipe medium is much larger than that of air, the magnetic memory signal is significantly attenuated after penetrating the pipe wall. As the detection height increases, the magnetic induction outside the tube decays exponentially. The results also prove that the magnetic tomography method can detect the stress concentration zone at any position of the pipeline, and the detection accuracy is higher when it is located at the top of the pipeline.

Study on stress measurement for steel bars inside RC beams based on self-magnetic flux leakage effect

The self-magnetic flux leakage (SMFL) effect has been widely studied because it not only can identify early damage evaluation of ferromagnetic materials but is highly sensitive to the stress state. To promote the application of the SMFL effect in the health detection of reinforced concrete (RC) bridge, the whole process failure experiment of the RC beams under four-point bending loading was carried out and a method for detecting and quantitatively evaluating reinforcement stress in RC beams was established. A three-axis automatic displacement device based on metal magnetic memory was used to collect the magnetic signals of the RC beams under different loads, the magnetic signals under different values (LOVs) and multiple scanning paths were analyzed. Based on the magnetic signals under different stress states, a dimensionless parameter Aσ was defined to quantitatively calculate the steel bars stress of RC beams. The experimental results show that in the pure bending section of RC beam, the steel bars stress, and the dimensionless parameter Aσ emerged with a linear relationship. Furthermore, the effect of parameter lift-off values (LOV) on the test results was discussed.

Characterising the stress ratio effect for fatigue crack propagation parameters of SAE 1045 steel based on magnetic flux leakage

The aim of this study was to determine the relationship between fatigue crack length, a, the number of cycles, N, the magnetic flux gradient intensity, dH/dx and the stress ratio, R. Fatigue crack growth tests were performed using a constant tensile load amplitude on SAE 1045 steel in the form of single-edge cracks. Stress ratio values of 0, 0.1, 0.2, 0.3 and 0.4 were used to study the characteristics of the magnetic flux gradient. A crack opening displacement device was used to detect the parameters of the stress intensity factor range, ΔK, fatigue crack growth rate, da/dN, and N. Meanwhile, a metal magnetic memory sensor device was used to detect the H value at the stress concentration zone when a 1 mm-increase in the crack occurred. The experimental results showed that as the fatigue cycle and crack length increased for each R, dH/dx also increased exponentially. The governing equations were derived based on the magnetic flux gradient for the fatigue crack length equation and the fatigue cycle equation, with the stress ratio. Based on a statistical analysis of the magnetic flux leakage signals, it was found that all the data were within a range based on a 90 % confidence level. Thus, the magnetic flux leakage parameters could be used to construct fatigue crack growth behaviour models for ferromagnetic materials and potentially as an alternative method for predicting the fatigue life.

Distribution of Magnetic Flux Density under Stress and Its Application in Nondestructive Testing

Carbon steels are commonly used in railroad, shipment, building, and bridge construction. They provide excellent ductility and toughness when exposed to external stresses. They are able to resist stresses and strains effectively, and guarantee safe operation of the devices through nondestructive testing (NDT). The magnetic metal memory (MMM) can be used as an NDT method to measure the residual stress. The ability of carbon steel to produce a magnetic memory effect under stress is explored here, and enables the magnetic flux density to be analyzed. The relationship between stress and magnetic flux density has not been fully presented until now. The purpose of this paper is to assess the relationship between stress distribution and the magnetic flux density measured by the experiment. For this, an experimental method for examining a carbon steel plate (SA 106), based on the four-point loading test, was used. The effect of stresses resulting from the applied loads on the response of the experimented SA 106 specimen was examined. A three directional tunnel magnetoresistance (TMR) measurement system was used to collect the triaxial magnetic flux density distribution in the SA 106 specimen. In addition, finite element method (FEM) analyses were performed, and provided information on the direction and distribution of the stress over the studied SA 106 specimen. Indeed, a correlation was derived by comparing the stress analysis by FEM and the measured triaxial magnetic flux density.

Collaborative detection and on-line monitoring of pipeline stress in oil and gas stations

The types of pipeline used in oil and gas stations is diverse, and it is difficult to comprehensively and accurately measure pipeline stress using a single detection method. Non-contact pipeline magnetic detection (NPMD), metal magnetic memory, ultrasonic stress measurement (USM) and ultrasonic thickness measurement (UTM)constitute a collaborative detection strategy for station pipelines. The pipeline magnetic abnormal evaluation parameter N is derived according to the sensor arrangement in NPMD devices. The magnetic field distribution based on different extraction heights is determined by the magnetic charge model and the experimental results, and a feature parameter E is constructed that can characterize the degree of stress concentration. The pipeline stress concentration points can be quickly determined in accordance with N and E. Reference stress values can be measured using USM and UTM. Monitoring is implemented at the stress concentration points, and the true stress values at the stress concentration points of the pipeline are established by combining the stress detection results. The collaborative detection method is applied to an oil and gas station, and two stress concentrations of 186.7 and 211.6 MPa are identified, respectively. The stress at the excavation pit is confirmed to be 196 MPa based on the monitoring data. Based on collaborative detection and on-line monitoring, fast and efficient collaborative detection and real-time mastering of station pipeline stress are achieved.

Detection of Uniaxial Fatigue Stress under Magnetic Flux Leakage Signals using Morlet Wavelet

This paper demonstrates the application of continuous wavelet transform technique for magnetic flux leakage signal generated during a uniaxial fatigue test. This is a consideration as the magnetic signal is weak and susceptible to being influenced by an external magnetic field. The magnetic flux leakage signal response of API steel grade X65 is determined using Metal Magnetic Memory under cyclic load conditions ranging from 50% to 85% of the UTS. To facilitate further signal analysis, the magnetic flux gradient, the dH(y)/dx signal were converted from a length base into time series in this study. Magnetic flux leakage readings indicated a maximum UTS load of 56.5 (A/m)/mm at 85%, where a higher load resulted in a higher reading and the signal contained Morlet wavelet coefficient energy of 1.02×106 µe2/Hz. As increasing percentages of UTS loads were applied, the signal analysis revealed an increasing linear trend in the dH(y)/dx and wavelet coefficient energy. The analysis revealed a strong correlation between the wavelet coefficient energy and the dH(y)/dx amplitude, as indicated by the coefficient of determination (R2) value of 0.8572. Hence, this technique can provide critical information about magnetic flux leakage signals that can be used to detect high stress concentration zones.

A prototype method to evaluate the inner wall defects of ferromagnetic materials based on a two-stage magnetic combined detection

As the ferromagnetic materials have been more and more widely used in engineering, the detection requirements of the inner wall defects on structural components such as pressure vessels and pipes become urgent. Under the effect of high temperature, high pressure and corrosive media, the inner wall defects of ferromagnetic materials including crack, pore and corrosion tend to appear. In order to improve the detection efficiency, it is wise to evaluate the inner wall defects from the outside of ferromagnetic materials in a nondestructive way. Considering the rapid detection capability of metal magnetic memory (MMM) and the high sensitivity of magnetic needle probe (MNP), we combine these two magnetic nondestructive testing (NDT) techniques together and use them at two different detection stages, respectively, to help to better evaluate the inner wall defects of ferromagnetic materials. During the first stage of MMM detection, the weak magnetic signals measured from the outside of samples show that both the amplitude of MMM signal tangential component HP(x) and the gradient of MMM signal normal component HP(y) change obviously at the location of inner wall defect. However, they cannot quantify the size of inner wall defect at the backside of samples due to the serious fluctuation of signal characteristics under the interference of environment. Next, during the second stage of MNP detection, the hysteresis loop obtained by MNP can be used to quantitative evaluation because the remanence Br and the coercivity Hc decrease sharply near the inner wall defect. Furthermore, the overall average values of remanence Br¯ and coercivity Hc¯ are proposed as the characteristic thresholds to accurately determine the location and the size of inner wall defect and the evaluation accuracy can reach up to 90%. In this paper, the two-stage MMM and MNP combined detection can provide a convenient and accurate prototype method to evaluate the inner wall defects of ferromagnetic materials from the outside.

Study of Deformation Behavior of AISI 1025 Carbon Steel with Different Microstructures Using Metal Magnetic Memory and Acoustic Emission Testing

Studies are carried out to investigate the tensile deformation behavior of AISI-type 1025 carbon steel with different microstructures using metal magnetic memory and acoustic emission testing (AE) techniques. Seven AISI 1025 carbon steel specimens were heat treated for different microstructures and then subjected to tensile deformation until fracture. AE was conducted during tensile deformation and the deformation-induced self-magnetic leakage fields (SMLFs) were measured using a giant magneto-resistive sensor after unloading. Results reveal that SMLF signal values are influenced by microstructure and residual stress aroused due to plastic deformation. Among different specimens, SMLF signal peak amplitude is highest in the brine-quenched specimen followed by the tempered specimen, while hardness is highest in the brine-quenched specimen. SMLF signal peak amplitude and hardness are the lowest in the annealed specimen. SMLF signal is higher in tempered specimens compared to the untempered specimens. From AE measurements, it is observed that martensitic steel emits higher acoustic emissions during deformation but decreases when tempered. The acoustic emissions generated in the martensitic steel are also of higher amplitude. The results are correlated with optical micrographs and hardness measurements.

Simulation and experimental study on magnetic memory effect of drill string under geomagnetic shielding

The existing metal magnetic memory (MMM) theory holds that the geomagnetic field is necessary for the MMM effect. However, when working at the drilling platform, it is found that after the drill string, working in multi-layer casing, which can be regarded as a magnetic shielding environment, is pulled out of the wellhead, there is still a strong MMM at the stress concentration part. This phenomenon contradicts the existing research conclusions. To reveal this abnormal phenomenon, it is necessary to explore the MMM effect under the condition of geomagnetic shielding. In this paper, COMSOL software is used to simulate the surface magnetic signal distribution of a specimen under the action of geomagnetic field and constructed zero magnetic environment. By using self-made magnetic shielding device and taking 35 CrMo specimen made of typical drill string steel, the four tensile tests of the specimens under the conditions of high and extremely low initial initial remanences in the geomagnetic environment, high and extremely low initial remanences in the geomagnetic shielding environment are compared. The comparison between simulation and experimental results shows that the geomagnetic field is not the necessary condition of MMM effect, while both the geomagnetic field and initial remanence are the necessary conditions of MMM effect. Therefore, the conclusion of this paper has certain scientific significance for perfecting the definition of MMM, and has certain engineering significance for guiding the field service of drill string.

Diagnostics of power boiler superheater tubes made of austenitic steel using the metal magnetic memory technique

Diagnostics of power boiler superheater tubes made of austenitic steel using the metal magnetic memory technique

Modeling, simulation and experimental exploration of metal magnetic memory under weak magnetic excitation

This study proposes to use the improved Jiles–Atherton (J–A) magneto-mechanical effect model combined with simulation analysis to detect the damage of wire rope. By establishing the theoretical basis of the J–A model under weak magnetic excitation, the simulation analysis is carried out by using ANSYS software, and finally the correctness of the simulation and theoretical results is verified by experiments. The results show that the weak magnetic excitation magnetic field has a strengthening effect on the magnetic memory signal under the action of the force-magnetic coupling. By processing the extracted magnetic memory signal, it is verified that the weak magnetic excitation magnetic field alone has a certain inhibitory effect on the environmental interference of the geomagnetic field. Compared with the geomagnetic field environment, the weak magnetic excitation magnetic field can better identify the different defect types of simulated 60 steel damage and wire rope defects. Studies have shown that weak magnetic excitation plays an important role in the damage detection of ferromagnetic materials.

Modeling magnetization processes in steel under stress using magnetic objects

The application of ferromagnetic steel products is pervasive in society, with important applications arising in electrical steel, oil and gas pipelines, transportation infrastructure, naval structures, aircraft landing gear, and automotive components. Magnetic properties of electrical steel materials play a key role in electrical motors and transformers, with a direct impact on energy efficiency. Measurement of response to magnetization has implications for non-destructive inspection methods, such as magnetic flux leakage, magnetic Barkhausen noise, and metal magnetic memory method. Examples include flaw detection, characterization of material properties, and identification of stress state in steel. An understanding of the magnetic response of steel materials can be facilitated by the use of magnetic objects (MOs). MOs are defined as regions of relatively independent magnetic behavior, typically about the size of a grain, to which fundamental magnetic energy considerations may be applied. This Tutorial outlines mechanisms by which MOs may be applied for modeling magnetic response in steel and presents examples of their application. MOs incorporate material physical properties such as microstructure, grain size, crystallographic texture, the presence of dislocations and impurity elements, and the presence of residual stress and stress load on the component. They can also accommodate a description of the evolution of magnetic domain structure under magnetizing conditions. As the MO model incorporates fundamental physics principles, it allows estimates of physical parameters that can be used to provide insights into the connections between magnetic properties and material properties, including hardness, embrittlement, and the presence of applied and residual stress. Practical applications include non-destructive characterization of the stress state of steel and an improved understanding of magnetic processes in electrical steel. Examples where such models may be applied include magnetic Barkhausen noise and magnetic memory method for the characterization of steel materials. This Tutorial summarizes recent advances in the MO model and its applications, providing the foundation for its further development. Magnetic objects have the potential to provide fundamental explanations and could form the basis for magnetic measurements and magnetization processes, including magnetic flux leakage, magnetic Barkhausen noise, and magnetic hysteresis.

Stress Evaluation of Welded Joints with Metal Magnetic Memory Testing Based on Tension-Compression Fatigue Test.

Metal magnetic memory testing (MMMT) is an effective nondestructive technique for fatigue damage monitoring of weldments because of its capacity for stress evaluation. An experimental investigation of the effect of the applied fatigue stress on MMMT signals, including the tangential component Bx and the normal component Bz, during tension–compression fatigue tests in welded joints was carried out systematically. The Bx and Bz signals at different fatigue cycles and fatigue stresses were collected and analyzed, and the results showed that there was a peak of Bx and abnormal peaks of Bz that existed at the welded joint before loading. After loading, the peak of Bx and the abnormal peaks of Bz reversed, and the Bx signals moved upward and the Bz signals rotated anticlockwise dramatically in the first few fatigue cycles. After the fatigue cycle number was larger than 1000, Bx and Bz were stable, with very little fluctuation. In addition, the characteristics of Bx signals, the mean value, and the peak value of the average of Bx had an extremely significant linear relationship with the applied fatigue stress during the stable stage of the fatigue test, which indicates that MMMT is a feasible method for fatigue stress evaluation and even residual fatigue life estimation for weldments in service.