Correlation Between Stress Concentration Degree and Residual Magnetic Field

2016 ◽  
Author(s):  
Sheng Bao ◽  
Ashri Mustapha ◽  
Huangjie Lou
Keyword(s):  
Magnetic Field ◽  
Stress Concentration ◽  
Tensile Tests ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Residual Magnetic Field ◽  
Concentration Degree ◽  
Qualitative Relationship ◽  
Ferromagnetic Steels

In this research, the correlation between the stress concentration degree and the residual magnetic field (RMF) of ferromagnetic steels is investigated. Tensile tests were carried out to measure the RMF signals on the surface of steel specimens with different stress concentration degrees. The effectivity of the metal magnetic memory (MMM) technique in defective specimens was investigated in comparison with a non-defective specimen. Analysis of the qualitative relationship between the stress concentration degree and the RMF components was subsequently performed on two types of defective specimens. The qualitative correlation between the planar distributions of the RMF components and the stress concentration degree was further studied. It was validated that both the RMF signal and its planar distribution are effective in characterizing the stress concentration degree. The results obtained in this research will be a complement to the MMM technique.

The State-of-the-Art Surveys for Application of Metal Magnetic Memory Testing in Remanufacturing

2011 ◽  
Vol 301-303 ◽  
pp. 366-372 ◽  
Author(s):  
Yuan Liang Zhang ◽  
Di Zhou ◽  
Peng Sen Jiang ◽  
Hong Chao Zhang
Keyword(s):  
Magnetic Field ◽  
Stress Concentration ◽  
Residual Life ◽  
Fatigue Cracks ◽  
Research Work ◽  
Creep Damage ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Comprehensive Survey ◽  
Chinese Scholars

Metal magnetic memory（MMM） testing has been used in the residual life prediction of remanufacturing cores. The MMM testing is one of the most promising nondestructive testing methods for achieving early diagnosis on micro defects of remanufacturing cores. This method can not only detect the traditional macro-cracks, but also identify the micro-damage caused by stress concentration. The principle of MMM testing works in the conditions that without requiring of the external exciting magnetic field, the magnetic field distribution of the inspection surface is scanned and measured by means of magnetic mutation signals to find the possible existence of stress concentration and location of micro-cracks. This paper presents a state-of-art survey about MMM testing mechanism and application of MMM method in Russia, Britain, China and the other countries. It includes the applications of this method in power station turbine blade damage detection by Russia scholars, evaluating the gear creep damage by Polish scholars and detecting the stress concentration districts of the train wheels damaged parts by Chinese scholars. The paper also reports that Chinese scholars developed methods of using MMM testing to characterize initiating and growing of fatigue cracks, and applied this method for prediction of residual life of remanufacturing cores. Based on the comprehensive survey, this paper points out further trends of the research work in the area. The paper also points out that microscopic physical mechanism of the MMM phenomenon and application of MMM testing in defining the manufacturability of remanufacturing cores should be further studied. Introduction

Quantitative Stress Evaluation and Defect Identification in Ferromagnetic Steels Based on Residual Magnetic Field Measurements

2021 ◽  
Vol 79 (3) ◽  
pp. 311-319
Author(s):  
S Bao ◽  
M Fu ◽  
Z Zhao ◽  
P Jin
Keyword(s):  
Magnetic Field ◽  
Applied Load ◽  
Quantitative Characteristic ◽  
Ferromagnetic Material ◽  
Tensile Tests ◽  
Load Level ◽  
Characteristic Parameters ◽  
Defect Identification ◽  
Residual Magnetic Field ◽  
Ferromagnetic Steels

In this paper, the correlation between the residual magnetic field (RMF) and the applied load is investigated. Tensile tests were carried out to measure RMF signals on the surface of 30CrNiMo8 steel specimens with three types of machined defect shapes. Results show that the RMF curves of the three different defective specimens demonstrate similar overall evolution patterns during the loading process, while the magnetic signals exhibit noticeable differences in the defect area. It suggests that the profiles of the stress-induced RMF curves are strongly dependent on the defect’s shape, notch width, and load level. An improved method is proposed to extract some quantitative characteristic parameters from the magnetic signals. The characteristic parameters that reflect the fluctuation degree are in quadratic polynomial relation with the applied load, which can be potentially used to evaluate the applied load acting on a ferromagnetic material with a macro defect. The characteristic parameters that reflect the acting range seem to be independent of the applied load, and the normal ones are capable of capturing the defect’s location and shape. This paper presents a supplement for quantitative defect identification for discontinuities in ferromagnetic steels by RMF measurements.

Evolution of the Stress-Induced Residual Magnetic Field of X70 Pipeline Steel With Multiple Corrosion Defects

2021 ◽  
Author(s):  
Sheng Bao ◽  
Qiang Luo ◽  
Zhengye Zhao ◽  
Jian Yang
Keyword(s):  
Magnetic Field ◽  
Pipeline Steel ◽  
Normal Component ◽  
Tangential Component ◽  
Magnetic Memory ◽  
X70 Pipeline Steel ◽  
Corrosion Defect ◽  
Residual Magnetic Field ◽  
Corrosion Defects ◽  
Ferromagnetic Steels

Abstract The aim of this research is to investigate the correlation between the residual magnetic field (RMF) and multiple corrosion defects in ferromagnetic steels. Specimens of X70 pipeline steel were machined into standard bars with a single corrosion defect, double corrosion defects and triple corrosion defects, respectively. Tensile tests were carried out to detect the RMF signals on the surface of these specimens. The variations of abnormal magnetic changes of the RMF signals with the external loads were investigated and the results showed that the tangential component and the normal component of the RMF signals of three defect patterns presented different shapes. It was found that the RMF signals were capable of capturing the location and the number of defects in pipeline steels. The peak values of the tangential component and the slopes of the normal component were not influenced by the defects number. This research will promote the investigation on the corrosion defect cluster of ferromagnetic steels based on the metal magnetic memory (MMM) technique.

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 Study of Magnetic Field Variation Induced in Ferromagnetic Materials

2013 ◽  
Vol 312 ◽  
pp. 402-405
Author(s):  
Yang Yong ◽  
Dong Sun ◽  
Jie Ji
Keyword(s):  
Magnetic Field ◽  
Plastic Region ◽  
Steel Specimen ◽  
Fatigue Tests ◽  
Experimental Results ◽  
Magnetic Memory ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Metal Magnetic Memory ◽  
Stress Increase

The fatigue tests on 15CrMo steel specimen were carried out and the metal magnetic memory (MMM) signals were detected. The experiment shows that the magnetic signals of specimen contain the information of stress distribution in the material inside. Furthermore, the experimental results show that the magnetic signals increase initial while then decrease slightly with the stress increase from 0kN to 200kN. Though analysis the MMM signals induced by different tensile stress within the plastic region of the specimen, a simple model was derived. The experimental results are consistent with the calculated results based on the Jiles-Atherton model.

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