Magnetic Memory Testing Technology Research Articles

Overview of welding defect detection utilising metal magnetic memory technology

Welded joints frequently endure the composite stress of steel components. The presence of defects within these welded joints can significantly jeopardise the safety and performance of the welded structure. Magnetic memory testing technology has garnered substantial attention due to its ability to evaluate welding defects. However, the conventional zero-point pole theory, which serves as the foundation for defect assessment in practical detection, may lead to defect location and omission errors. In response to this challenge, scholars have conducted extensive research to accurately pinpoint the location and identify the types of defect within welds. This paper systematically reviews the mechanisms of magnetic memory welding defect detection, the factors that influence it, signal characteristic parameters, noise reduction in magnetic memory signals and the application of machine learning for quantitative assessment. By summarising these research advancements, this paper aims to address the current issues and provide guidance for the precise quantitative evaluation of welding defects in the future using metal magnetic memory technology.

Experimental Study on Fatigue Damage of Drilling Tool Materials Based on Magnetic Memory Detection

In drilling engineering, the cost of drilling tool fracture is enormous, and studying the fatigue failure process of drilling tools has practical significance. This paper uses metal magnetic memory detection technology to design and conduct fatigue damage tests on typical drilling tool material 42CrMo specimens under tensile, torsional, compressive, tensile, compressive, and torsional dynamic loading conditions. By analyzing the changes in the tangential component Hp(x) and gradient value K of the magnetic memory signal under different load conditions with the number of loading times, the process of fatigue failure of the specimens and the trend of changes in the magnetic memory signal in local stress concentration areas are explored. The characteristic parameters of fatigue damage based on magnetic memory detection were extracted and the critical point at which fatigue damage leads to crack initiation was inferred. This confirms that metal magnetic memory testing technology is an effective means of analyzing the fatigue damage process of drilling tools and provides a certain reference for formulating judgment standards for drilling tool maintenance on site.

Quantitative Evaluation of Corrosion Defects on Structural Steel Plates via Metal Magnetic Memory Method

ABSTRACT The detection and evaluation of corrosion defects take on a critical significance to ensure the service safety of steel structures in civil engineering. The quantitative evaluation of corrosion defects has not been well addressed though metal magnetic memory (MMM) testing technology has been investigated in steel corrosion problems. In this study, the Q345qD steel plates were taken as the specimens of MMM testing. Specimens with different corrosion degrees were developed through electrochemical corrosion, and the change laws of the MMM signals and the characteristics of different corrosion specimens were analyzed. A three-dimensional (3D) magnetic charge model of the corrosion area was built based on the magnetic charge theory, such that the change laws of the MMM signal in the corrosion area from the mechanism were explained. The finite element simulation results of the corrosion specimens were well consistent with the experimental and theoretical results. A quantitative evaluation method for corrosion defect depth was proposed in combination with finite element simulation and experimental data. Comparing the experimental data and the inversion data, the relative errors of the determined defect depth h were within 20%, suggesting that the proposed evaluation method is feasible for the quantitative evaluation of steel corrosion depth.

Research on temperature-magnetic properties based on metal magnetic memory testing technology

during the running of high-speed railway, the vibration and friction between wheel set and track will cause the temperature rise between wheel set and track. The metal magnetic memory detection technology is used to detect the small fault of wheel set, and the temperature will have a certain impact on the magnetic memory signal. In order to study the quantitative relationship between temperature and magnetic memory signal, the temperature magnetic property of 25CrMo4 material is proposed in this paper. Through the temperature magnetic experiment and simulation analysis of the material specimen, it is concluded that when the temperature is lower than Curie point, the magnetic flux leakage of the sheet is basically stable. The value in tangential direction is 130A/m, and the value in normal direction is 0A/m. When the temperature reaches Curie point, the value of the tangential direction changes to 169.9 A/m, and the normal direction is still 0A/m; And the temperature magnetic numerical simulation curve is constructed, which provides the basis for carrying out magnetic signal to material small fault under coupling load, and provides the basis for non-destructive testing.

Application of Metal Magnetic Memory Testing Technology to the Detection of Stress Corrosion Defect

The damage of equipment manufactured with ferromagnetic materials in service can be effectively detected by Metal Magnetic Memory Testing (MMMT) technology, which has received extensive attention in various industry fields. The effect of stress or strain on Magnetic Flux Leakage (MFL) signals of ferromagnetic materials has been researched by many scholars for assessing stress concentration and fatigue damage. However, there is still a lack of research on the detection of stress corrosion damage of ferromagnetic materials by MMMT technology. In this paper, the electrochemical corrosion system was designed for corrosion experiments, and three different experiments were performed to study the effect of corrosion on MFL signals. The distribution of MFL signals on the surface of the specimen was investigated. The results indicated that both the normal component Hn and tangential component Ht of MFL signals presented different signal characteristics when the specimen was subjected to different working conditions. Finally, two characterization parameters, Sn and St, were defined to evaluate the corrosion degree of the specimen, and St is better. The direct dependence of corrosion depth on the parameter was developed and the average error rates between the predicted and measured values are 8.94% under the same working condition. Therefore, the expression can be used to evaluate the corrosion degree of the specimen quantitatively. The results are significant for detecting and assessing the corrosion defect of ferromagnetic materials.

Magnetic crawler climbing detection robot basing on metal magnetic memory testing technology

Failure detection of high facilities always presents a tremendous challenge. Climbing-wall robot with detection capacity has become a main approach. But owing to their limitations in overcoming obstacles and complicated wall situation, reliable wall-climbing property and precise detection abilities are the most basic demand for achieving this function. Hence, further research is required to enhance robot capabilities in overcoming obstacles and accurate detection signal. The paper presents a new climbing-wall detection robot mechanism. The wall-climbing robot consists of two climbing modules. The two climbing modules are connected by anti-overturning mechanism to provide a capacity of anti-overturning during overcoming obstacle. The detection mechanism is installed at the bottom of the robot. Detailed design issues are presented with analyses of the design parameters. Transition displacement of anti-overturning mechanism and force transfer equation are derived, and stable operating conditions are verified. The abilities of flat surface locomotion, anti-overturning, preload and detection capacity are validated by using experiments. Experiment results show that the prototype achieves 10kg payload capacity on vertical surfaces and can overcome 10mm obstacle. 1mm×1mm circular groove can be found.

Studies on influences of initial magnetization state on metal magnetic memory signal

Metal magnetic memory testing is a novel testing method which can early test stress concentration level of ferromagnetic components. In theory, the influences of the initial magnetization on the magnetic memory signal were studied. In the experimental aspect, take Q235 steel specimen for example, the relationship between initial magnetization state and metal magnetic memory signal was researched by static tensile test under three different initial magnetization conditions. Both the experimental studies and theoretical analysis come to similar conclusion that the variation trend of magnetization with the stress is that the initial magnetization status tends to shift towards the non-hysteresis magnetization state. With the increasing of stress, the magnetizing state gradually shifts towards the anhysteretic magnetization state, and the variation rate is directly proportional to the difference between the initial magnetization and the non-hysteresis magnetization. Our study indicates that the initial magnetization state has an important influence on the magnetic memory signal, and the research results can provide reference for quantitative test of metal magnetic memory testing technology.

A Judgment Criteria and Its Application for Magnetic Memory Testing Based on the Reassigned Wavelet Scalogram

The Metal Magnetic Memory Testing technology is a completely new method in recent years. The reassigned wavelet scalogram analysis method can improve the aggregation of scalogram, reduce interference terms, and be understood easily to some extent. Aiming at the deficiency of using Metal Magnetic Memory Testing to recognise pipeline defect, the reassigned wavelet scalogram analysis method is put forward to analysis the Metal Magnetic Memory Testing signal in this paper. The experimental research proves that the reassigned wavelet scalogram effectively used for Pipeline Defect Recognition by Metal Magnetic Memory Testing.

Application of Metal Magnetic Memory Testing Technology in Pipeline Defect

The metal magnetic memory testing technology can detect the stress concentration area of ferromagnetic materials, and then diagnose the micro defects and early damage. Based on the principle of artificial neural network, 3 single output three layer BP neural networks are designed by using metal magnetic memory testing technology. In this paper, the stress concentration, crack and other pipeline defects are detected and identified. The experimental results show that the recognition rate of pipeline defects is 97.5%.

Studies on laws of stress-magnetization based on magnetic memory testing technique

Metal magnetic memory (MMM) testing technique is a novel testing method which can early test stress concentration status of ferromagnetic components. Under the different maximum tensile stress, the relationship between the leakage magnetic field of at certain point of cold rolled steel specimen and the tensile stress was measured during the process of loading and unloading by repeated. It shows that when the maximum tensile stress is less than 610MPa, the relationship between the magnetic induction intensity and the stress is linear; When the maximum tensile stress increase from 610MPa to 653MPa of yield point, the relationship between the magnetic induction intensity and the tensile becomes bending line. The location of the extreme point of the bending line will move rapidly from the position of smaller stress to the larger stress position, and the variation of magnetic induction intensity increases rapidly. When the maximum tensile stress is greater than the 653MPa of yield point, the variation of the magnetic induction intensity remains large, and the position of the extreme point moves very little. In theoretical aspects, tensile stress is to be divided into ordered stress and disordered stress. In the stage of elastic stress, a microscopic model of the order stress magnetization is established, and the conclusions are in good agreement with the experimental data. In the plastic deformation stage, a microscopic model of disordered stress magnetization is established, and the conclusions are in good agreement with the experimental data, too. The research results can provide reference for the accurate quantitative detection and evaluation of metal magnetic memory testing technology.

Study on characteristics of magnetic memory testing signal based on the stress concentration field

Metal magnetic memory testing technology has been effectively used in stress concentration areas and micro-cracks detection of ferromagnetic metal components. However, due to the lack of profound theoretical basis and effective experimental research, the magnetic memory signal characteristics and magnetism quantitative relationship has not yet been determined. In this study, the full electronic potential magneto-mechanical model is established which is using the norm conserving pseudo-potential algorithm based on the first-principle. The quantitative relationship is then calculated between the stress concentration and the magnetic memory signal. The calculation results show that the changes of the wave function, which result from the stress concentration in the solid band, are the fundamental cause of the magnetic memory phenomenon, and atomic magnetic moment, lattice constant and the magnetic flux leakage signal strength linearly changes as a function of stress trend. As the stress concentration reached the critical stress point, the lattice structure was damaged, and the magnetic memory signal had undergone mutation. In this study, the experimental results are consistent with the theoretical calculation results.

Stress Evaluation of Plasma Sprayed Cladding Layer Based on Metal Magnetic Memory Testing Technology

Stress Evaluation of Plasma Sprayed Cladding Layer Based on Metal Magnetic Memory Testing Technology

Simulation Study of Magnetic Memory Signal Correlation Effect of Dual Defects by ANSYS

To study the correlation effect of multiple defects of metal magnetic memory (MMM) testing technology, the stress-magnetization effect on 20# steel specimen with dual defects under exercise of the geomagnetic field and tensile load is simulated by using the finite element analysis (FEA) software ANSYS. With the stimulation, the magnetic flux leakage (MFL) distribution with different measured paths and different lift-off values of the surface specimen is given. The results showed that the correlation effect of dual defects produce more severe stress concentration phenomenon on the associated region of ferromagnetic specimen, and had no obvious effect on the edge of ferromagnetic materials; Gradient value K of the normal component H(z) of leakage magnetic field in the specimen, as a parameter evaluation of stress concentration in the specimen, has high reliability in areas without correlation effect, but it has no credibility in areas under dual defect correlation effect. Moreover, this article also discusses the influence of measured path and the lift-off value on magnetic memory signals.

Numerical Simulation Study of Stress-Magnetization Effect on Different Notch Steel Specimens

To study the mechanism of metal magnetic memory (MMM) testing technology, the stress-magnetization effect on 20 steel specimens with different notch angles under exercise of the geomagnetic field and tensile load is simulated by using the finite element analysis (FEA) software ANSYS. With the stimulation, the stress and magnetic flux leakage distribution of the specimens is given. The results showed that internal stress distribution of different notch specimens under external tensile effects is different; The curves of relationship between damage degree of stress concentration and the distribution of magnetic flux leakage is also related to the defect shape and structure; Magnetization decreases with increases of stress at first and then increases with continuing increase of stress, which is called stress magnetization reversal. It provides an important reference for the quantitative research of metal magnetic memory technology.

Based on the Magnetic Memory Testing Technology of Wind Generator Fault Early Prediction Research

The study is based on wind power tower drum with Q345E low alloy steel weld detection of magnetic memory method, combining with the characteristic of X-ray photos of magnetic memory formation mechanism and made a detailed analysis. By doing this, it aims to show that increasing scan device on the number of channels, can to a certain extent, improve the accuracy of detection. Magnetic memory method is proved to be able to predict the nondestructive testing artifacts of the early damage and the possibility of micro crack germination to some extent. It shows that the weld seam can be quickly found dangerous parts by using the magnetic memory test full scan, coupled with the X-ray testing technology for defects, and it also can be further qualitative and quantitative and significantly improve the detection efficiency.

Magnetic Memory Testing and Intensity Failure Analysis of Fractured Bolt of Cylinder Head on Hydrogen Gas Compressor

Along with the wide application of pressure energy, large scale reciprocating compressor unit is becoming one of the necessary key equipments in petrochemical industry. The reciprocating compressor has complicated structure and it is very difficult to carry out measurement & analysis to the operation status of various components. Above all, as the most important fastener of the compressor, once fracture of cylinder head bolt of the reciprocating compressor occurs, major disaster will occur. Metal magnetic memory testing technology is a nondestructive examination technology based on magneto-mechanical effect principle. Specific change of leakage magnetic field will occur in stress & deformation concentrated region under combined action of alternate work load and geomagnetic field, macroscopic cracking can be detected and stress concentration and early state damage can be evaluated by utilizing this specific change, We carried out on-site examination on the fractured bolt of cylinder head of hydrogen gas compressor unit in refinery of certain petrochemical corporation with latest metal magnetic memory testing technology. On the basis of intensity analysis and dynamic load calculation to cylinder head bolt of the reciprocating compressor, we analyzed the cause of bolt fracture by using metal magnetic memory testing technology and drew out the magnetic memory signal distribution characteristics of the bolt and its fracture. We verified the correctness of testing result of the metal magnetic memory technology on cylinder head bolt and its fracture with metallographic examination technology; furthermore, we studied the reliability of bolt fatigue crack & fracture analysis and investigation of accident cause by using magnetic memory characteristic distribution signal.

Analysis of Metal Magnetic Memory Testing Technology

The magnetic memory effect and the principle of magnetic memory testing are described; The phenomenon of the magnetostriction is discussed. An instance is used with detail to analysis of the effect and mechanism of metal magnetic memory testing technology. Some opinions about the further work needs to be done in this area are given finally.

Investigation of Array Magnetic Memory Testing Technology on Extension of Metal Crack

Metal Magnetic Memory (MMM) testing method has its own effective and unique advantages on the research of extension of metal crack. The array magnetic memory testing sensor designed and assembled in accordance with specific conditions, could evidently enhance testing-efficiency, such as for components with complex shape or large surface area, and may simplify the test equipment correspondingly. A kind of array magnetic memory sensor with Hall elements as core components was designed and an experiment on metal magnetic memory testing on extension of metal crack was executed. The experiment results indicate that the magnetic memory testing technique could effectively monitor and qualitatively evaluate the progress of metal crack extension.

Influences of environmental magnetic field on stress-magnetism effect for 20 steel ferromagnetic specimen

The stress-magnetism effect is a fundamental principle in metal magnetic memory testing technology, which is also a key issue in the life assessment of ferromagnetic materials. Curves of magnetising status versus stress in different environmental magnetic fields were studied for 20 # steel ferromagnetic specimens. It was found that influences of the environmental magnetic field on the stress-magnetism effect were very obvious. It shows that testing and estimating of metal magnetic memory testing technology is related to the geomagnetic field.

Magnetic memory testing for medium carbon steel under the condition of fatigue experiment

Metal magnetic memory testing technology is a new kind of testing method in the field of nondestructive testing. With special testing concept,it is expected to accomplish veracious nondestructive testing job for ferromagnetic metal work pieces in the early damage phase.Owing to the immature development of metal magnetic memory testing technology,a lot of basic researches about theory and application range of this new technology need to be carried out.The change of magnetic memory signals for medium carbon 45 steel is studied by a variety of fatigue experiments.The research shows that magnetic memory signals varies regularly in the special fatigue mode.The magnetic memory,testing technology can test the high-load fatigue damage better than it can do for the low-load one.It has better ability of testing defect specimens than that of testing the smooth ones.Furthermore,the cause of formation of magnetic memory phenomenon is analyzed.It is deduced that it is the fatigue action that results in the formation and development of dislocation stress fields in the weak region of loaded specimens and arises obviously different distribution of magnetic domains between these weak regions and normal regions,and these special regions can be found by special magnetic signals.Experiments reveal that,magnetic memory testing technology is useful to judge damage state of metal materials,but the judge veracity may be influenced by a variety of factors,such as the condition of loading and specimen shape.