scholarly journals Influence of Crack Size on Stress Evaluation of Ferromagnetic Low Alloy Steel with Metal Magnetic Memory Technology

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4028 ◽  
Author(s):  
Liu ◽  
Fu ◽  
Li ◽  
He ◽  
Dong
Keyword(s):  
Magnetic Domain ◽  
Groove Depth ◽  
Crack Size ◽  
Groove Width ◽  
Magnetic Memory ◽  
Experimental Sample ◽  
Metal Magnetic Memory ◽  
Magnetic Intensity ◽  
Intensity Gradient ◽  
As Stress

Based on the magneto-mechanical effect, the influence of crack size on stress evaluated with metal magnetic memory (MMM) technology was discussed in this paper. Based on equivalent theory, the regular rectangular grooves, with different widths and depths, were precut in the surface of an experimental sample for simulating surface crack, and a three dimensional electrically controlled displacement system was used to collect the Hp(y) signal of the sample under different stresses, and the fracture morphology was observed by using scanning electron microscopy (SEM). The results show that the influence of detection line on Hp(y) signal can be ignored; as stress increases, the Hp(y) signal turns counterclockwise around zero-crossing point and its mutation, corresponding to the location of groove, becomes distinct gradually. When groove depth is constant, the magnetic intensity gradient changes in the form of quadratic polynomial as groove width increases, and when the groove width is the same, the magnetic intensity gradient is a linear function of groove depth. When stress reaches the yield strength of the material, the magnetic intensity gradient decreases gradually as stress increases further, and the orientation of magnetic domain is seen as the main reason for that result. At last, the experimental results are discussed based on the piezomagnetic effect and leakage magnetic field theory of finite depth slit model, and the change of magnetic domain orientation is considered to be the main reason.

A Review of the Metal Magnetic Memory Technique

2016 ◽  
Author(s):  
Sheng Bao ◽  
Meili Fu ◽  
Shengnan Hu ◽  
Yibin Gu ◽  
Huangjie Lou
Keyword(s):  
Experimental Investigations ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Non Destructive Testing ◽  
Early Failure ◽  
Destructive Testing ◽  
Damage State ◽  
Recent Developments ◽  
As Stress ◽  
Non Destructive

Metal magnetic memory (MMM) is a newly developed non-destructive testing (NDT) technique. It has potentials to detect early failure, such as stress concentration, micro-crack and fatigue damage of ferromagnetic components. This paper outlines the recent developments of the mechanism studies on the MMM technique. Several advances in experimental investigations on the MMM technique are also summarized, e.g. the factors which can influence the detection signals, the criteria for judging the damage state and the magnetic parameters which can be used to assess the testing results. Finally, some future development trends about this technique are suggested.

scholarly journals The Quantitative Prediction of Pipeline Cracks Using Metal Magnetic Memory Based on a Regression Model

2014 ◽  
Vol 8 (1) ◽  
pp. 1-8
Author(s):  
Lihong Gong ◽  
Zhuxin Li ◽  
Zhiqiang Song
Keyword(s):  
Regression Model ◽  
High Efficiency ◽  
Quantitative Description ◽  
Surface Preparation ◽  
Quantitative Prediction ◽  
Coefficient Of Determination ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Early Failures ◽  
As Stress

The technique of metal magnetic memory (MMM) has great advantages in detecting early failures such as stress concentration and fatigue damage of ferromagnetic components, which has been widely applied due to its high efficiency, low requirements for surface preparation and ease of operation. However, research into the quantitative description of defect characteristics is still far from adequate. To promote relative study in this area, in this paper, a regression model is employed to analyze the sizes of surface cracks in pipelines. Three nonlinear functions are obtained to predict the length, width and depth of cracks respectively based on a regression model. Length prediction is convenient and accurate, with the average coefficient of determination of training samples up to 0.994 and that of testing samples 0.962. Moreover, as the width and depth are small (less than 2 mm), the accuracy of size prediction is very high. The obtained functions provide a useful method of predicting the crack sizes of pipelines according to MMM signals.

Research on Depth Evaluation of Surface Crack in Laser Cladding Coating with Metal Magnetic Memory Technology

2014 ◽  
Vol 651-653 ◽  
pp. 73-77
Author(s):  
Bin Liu ◽  
Zhu Jing Shao ◽  
Shi Yun Dong
Keyword(s):  
Laser Cladding ◽  
Surface Crack ◽  
Evaluation Method ◽  
Magnetic Domain ◽  
Tensile Load ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Fitting Method ◽  
Leakage Field ◽  
Lift Off

Depth of evaluation method of surface crack in laser cladding coating with metal magnetic memory was introduced in this paper. Laser cladding coating specimen were degaussed, placement direction of specimen and detection direction unchanged, detection speed and lift off value of probe were the constant. Results show that gradient value ofHp(y) signal corresponding to surface crack increases as tensile load increases under the same depth of surface crack, gradient value ofHp(y) signal corresponding to surface crack increases as depth of surface crack increases under the same tensile load. Orientation of internal magnetic domain changes as tensile load changes and magnetic leakage field caused by surface crack are seen as two main reasons for above results. Using fitting method with quadratic polynomial, depth of surface crack in laser cladding coating can be evaluated nondestructively in this paper.

Stress Concentration Positions Determination of Ferromagnetic Material Based on Magnetic Test Method

2009 ◽  
Vol 417-418 ◽  
pp. 865-868
Author(s):  
Feng Yun Yu ◽  
Jing Chong Zhang
Keyword(s):  
Magnetic Field ◽  
Stress Concentration ◽  
Spontaneous Magnetization ◽  
Tensile Load ◽  
Test Point ◽  
Test Method ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Magnetic Intensity ◽  
The Magnetic Field

The magnetic field of ferromagnetic components under service load and geomagnetic field increases is induced by the residual magnetic induction and spontaneous magnetization. The stress concentration positions can be determination by detecting the magnetic field and the fracture can be avoided. The magnetic intensities of the demagnetized samples are tested by metal magnetic memory test method. By tensile test, the relationship between the magnetic memory signals and tensile load is studied, and the metal magnetic memory characteristics of the demagnetized samples under condition that the load keeps a fixed value are obtained. The test result indicates that the magnetic intensities of the samples change greatly after demagnetized; the change of the magnetic intensity of each test point are much different with different tensile displacement; in the later period of hardening phase and necking phase, the magnetic intensity about the side of the stress concentration positions increases along with the increasing of tensile displacement, however that of the other side decreases, that is the gradient of Fracture position increases obviously. Basing on this result by testing the parts of components emphatically where the fatigue failure and breakdown appear easily, the abrupt accident can be avoided.

Experimental Research on Metal Magnetic Memory Method

2011 ◽  
Vol 52 (3) ◽  
pp. 305-314 ◽  
Author(s):  
K. Yao ◽  
Z. D. Wang ◽  
B. Deng ◽  
K. Shen
Keyword(s):  
Experimental Research ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Metal Magnetic Memory Method

Research of Pipeline Weld Detection Based on Magnetic Memory Technology

2014 ◽  
Vol 940 ◽  
pp. 222-225
Author(s):  
Fei Fei Long ◽  
Jian Zeng Wang ◽  
Li Li ◽  
Jun Ru Zhao
Keyword(s):  
Strain State ◽  
Evaluation Method ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Safe Operation ◽  
Long Distance ◽  
Peak Period ◽  
Detection Evaluation ◽  
Metal Magnetic Memory Method ◽  
Testing Work

Ensuring the safe operation of pipeline and monitoring it to prevent sudden accidents are an important task of current nondestructive testing work because of our country is in the peak period of long-distance pipeline construction. Welding cracks are common and most dangerous flaw in the root of the failure of the welded joints . Metal magnetic memory method is the only viable detection , evaluation method currently used for diagnosing the stress-strain state of serving welding crack in the early stages. So this article designs weld cracks of the general pipeline, establish a method to detect pipeline weld crack by metal magnetic memory method.

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