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Both corrosion defects and stress can cause magnetic field mutations, so the effect of stress must be considered in the magnetic detection of steel corrosion. This paper focuses on exploring the influence law of tension on magnetic signals of the corroded specimens. Based on the spontaneous magnetic leakage mechanism of steel bar corrosion and the stress magnetization model, the magnetic memory detection of corroded reinforced concrete under tension was carried out. The magnetic characteristics of corroded specimens before and after loading were analyzed. The corrosion positions of the specimens can be determined according to the representative mutation points (RMP) of the Byc(0) curves, and the magnetic index I2 was proposed to roughly determine the corrosion degree of the specimens when the specimens were not subjected to tensions. The experimental results showed that the RMP of Byc(F) curves can still represent corrosion positions when the specimens were under tension. The theoretical derivation showed that the magnetic field change caused by tensile force is limited, and the maximum value of the magnetic field change caused by tensile force can be obtained. Based on this, the corresponding I3-F curves were obtained through the test. The magnetic field change caused by the most unfavorable tensions was calculated to analyze its influence on corrosion magnetic detection. Compared with I2, the relationship between I3 and the corrosion degree was more discrete, indicating that tensile forces affected the quantitative detection of corrosion. Still, the magnetic field caused by corrosion played a leading role. The verification showed that the measured corrosion positions of reinforced concrete specimens were in good agreement with those detected by the magnetic memory method. [ABSTRACT FROM AUTHOR]

The metal magnetic memory is used to detect the micro damage of structure based on the SMFL (self-magnetic flux leakage) effect, but it lacks an effective comprehensive diagnosis index suitable for the ferromagnetic material. In this paper, steel strand specimens were tensioned at different force levels, and the experimental study on the corrosion detection was carried out. Besides the monitoring analysis of the cable force, the initial structural magnetic field ΔBx0 and the surface SMFL signals Bx(α) induced by corrosion were both analysed. The results show that ΔBx0 curves of steel strand material present the periodic fluctuation. Considering ΔBx0 and measuring distance z, the proposed dimensionless damage analysis index X can be used for the quantitative research of corrosion diagnosis. The small influence of the cable force on index X is also illustrated. Moreover, the strong correlation that exists between the average maximum index X m a x ‾ and the corrosion ratio α is well fitted by the three-order polynomial curves. [ABSTRACT FROM AUTHOR]

• The magnetic parameter, concrete strain, reinforcement strain and deflection exhibit synchronous growth with high correlation. • The Y and B C curves in the mid-span of the beam effectively divide the beam failure mode into three loading stages. • The quantification of the relationship between mechanical indexes and SMFL intensity reveals linear associations for Y-B C and ε-B C. • A correlation between SMFL intensity, reinforcement stress and beam flexural strength is established. This paper proposes a novel approach for monitoring the bearing capacity of RC beams using the spontaneous magnetic flux leakage (SMFL) effect. Three decommissioned reinforced concrete hollow slab (RCHS) beams underwent bending loading failure experiments to collect data on crack formation, deflection Y , concrete strain ε , steel bar strain ε and SMFL intensity B x/y/z. The mechanical properties of concrete outside the structure and the magnetic properties of steel bars inside the structure during loading are investigated. The force-magnetic coupling effect of HRB400 steel bars is characterized. The SMFL parameter B C closely correlates with Y and ε variations in loading process, the quantitative relationship models between mechanical and magnetic parameters of the beam structures are established. A theoretical model predicted the ultimate bending capacity of RCHS beams. The relationship between beam bending capacity and SMFL intensity is clarified. [ABSTRACT FROM AUTHOR]

• The B T/N intensities in different directions on the rebar surface have various force-magnetic coupling characteristics. • The effect of stress strength and initial magnetization intensity on the variation pattern of rebar SMLF intensity is different. • Initial magnetization induces an abrupt change in B T/N curves at the yield strength, effectively distinguishing rebars' elastic and plastic stages. • The initial magnetization state enhances the sensitivity of SMLF intensity to characterize stress variation in rebars. • The tangential SMLF parameter D T has a higher sensitivity to the stress variation in rebars. To investigate the effect of the initial magnetization state on the force-magnetic coupling effect of rebars, magnetic field magnetization experiments and axial tensile experiments of rebars were conducted. The tangential/normal components of spontaneous magnetic leakage field (SMLF) intensity B T/N were collected. The "SMLF intensity distribution parameters" D T/N were introduced to quantify the degree of stress-induced changes in the distribution of the B N/T curves on the rebar surface. The results show that both the stress state and the initial magnetization state affect the variation pattern of SMLF intensity of rebars, and B T/N have different characteristics of the force-magnetic coupling effect. With the increase of tensile stress, B T curves shift downward and B N curves rotate counterclockwise. With the increase of magnetization, the convexity degree of B T curves and the variation range of B N curves enlarge. And both B T/N values change abruptly at the yield strength point. The initial magnetization state drives the force-magnetic coupling effects in the elastic and plastic stages to exhibit differences. The σ-D T/N curves in the elastic stage are linearly monotonically decreasing, where the σ-D T fitted straight line has a large downward slope. D T is more sensitive to stress changes. The D T/N variations in the plastic stage can effectively characterize the stable development region of plastic deformation. The modified J-A magnetomechanical model reveals the contribution of the initial magnetization state to the characterization of the force-magnetic coupling effect. The morphological analysis of the rebar microstructure clarifies the physical reasons for the SMLF variation under different stress states. This research provides a new idea for the non-destructive detection of the rebar stress state. [ABSTRACT FROM AUTHOR]

• During repetitive tensile loading, the fluctuation period of the tangential leakage intensity Bσ Y can accurately indicate the stress fluctuation of the steel bar. • Repetitive tensile load induces the stabilization of the tensile displacement v of the steel bar. The variation of v is positively correlated with the variation of Bσ Y. • The proportional change in the repetitive tensile load amplitude 2f i is approximately equivalent to the proportional change in the tangential leakage magnetic intensity ΔBσ Yi. • A linear relationship exists between the parameter B N and 2f i. The quantitative measurement of fluctuating stresses can be achieved by detecting the ΔBσ Yi value, combined with the f i expression. For the ambiguous status of force-magnetic effect on bridges under repeated loading, different repetitive loads were applied to HRB400 steel bars. The magnetic leakage intensities of steel bars were detected and the 'magnetic leakage ratio parameter' B N was introduced. The results indicate that the fluctuation of tangential magnetic leakage intensity Bσ Y is consistent with the variation of tensile load. The variation ΔBσ Y is positively correlated with steel bar tensile displacement v and repetitive tensile load amplitude 2f i. At various loading phases, the proportional change of 2f i is equal to the proportional change of ΔBσ Yi. That makes a linear relationship between 2f i and B N , which derives the expression of f i. Tensile loads are effectively calculated, enabling quantitative measurement of fluctuating stresses in steel bars. The measured deviation rate is within 10.0%. The theoretical model verifies the correctness of experimental results. This study provides new ideas for the nondestructive testing of stress. [ABSTRACT FROM AUTHOR]

In an actual structure, the arrangement of steel bars is complicated, there are many factors affecting the corrosion of steel bars, and these factors affect each other. However, accurately reflecting the corrosion of steel bars in actual engineering through theoretical calculations is difficult. Besides, it is impossible to detect and evaluate steel bars rust completely and accurately. This article is based on spontaneous magnetic leakage detection technology and adopts the method of stage corrosion and scanning along the reinforcing bar. Based on spontaneous magnetic flux leakage detection technology, the linear change rate of the tangential component curve of the magnetic flux leakage signal generated after the corrosion of a steel bar is studied, and a comparison is made between the steel bar coated concrete samples with different steel bar diameters. In this paper, the "origin of magnetic flux leakage signal" is defined as a reference point, which is convenient for effectively comparing the magnetic signal curves under all operating conditions. Besides, the "rust-magnetic fluctuation parameter" is proposed to accurately reflect the sudden change of leakage magnetic field caused by disconnection due to the corrosion of a steel bar. A new data processing method is provided for the non-destructive testing of steel corrosion using the spontaneous magnetic flux leakage effect, which can effectively reduce the influence of steel bar diameter on magnetic flux leakage signal and improve the precision of non-destructive testing technology of steel bar corrosion using the metal magnetic memory effect. [ABSTRACT FROM AUTHOR]

Based on the metal magnetic memory effect, this paper proposed a new non-destructive testing method for the internal tensile force detection of steel bars by analyzing the self-magnetic flux leakage (SMFL) signals. The variation of the SMFL signal of the steel bar with the tensile force indicates that the curve of the SMFL signal has a significant extreme point when the tensile force reaches about 65% of the yield tension, of which the first derivative curve has extreme points in the elastic and yielding stages, respectively. To study the variation of SMFL signal with the axial position of the steel bar under different tensile forces, a parameter reflecting the fluctuation of the SMFL signal along the steel bar is proposed. The linear relationship between this parameter and the tensile force can be used to quantitatively calculate the tensile force of steel bar. The method in this paper provides significant application prospects for the internal force detection of steel bar in the actual engineering. [ABSTRACT FROM AUTHOR]

This paper proposed a new computing method to quantitatively and non-destructively determine the corrosion of steel strands by analyzing the self-magnetic flux leakage (SMFL) signals from them. The magnetic dipole model and three growth models (Logistic model, Exponential model, and Linear model) were proposed to theoretically analyze the characteristic value of SMFL. Then, the experimental study on the corrosion detection by the magnetic sensor was carried out. The setup of the magnetic scanning device and signal collection method were also introduced. The results show that the Logistic Growth model is verified as the optimal model for calculating the magnetic field with good fitting effects. Combined with the experimental data analysis, the amplitudes of the calculated values (BxL(x,z) curves) agree with the measured values in general. This method provides significant application prospects for the evaluation of the corrosion and the residual bearing capacity of steel strand. [ABSTRACT FROM AUTHOR]

The non-destructive quantitative evaluation of the rebar corrosion degree is an urgent problem to be solved for corroded reinforced concrete structures. In this study, a non-destructive quantification method for the rebar localized corrosion cross-sectional area was proposed based on the dynamic linkage mechanism of the induced magnetic and self-magnetic flux leakage fields of rebar. As verified by data from the experiment and the finite element simulation, this quantification method could eliminate the adverse influence of the magnetic property differences of the rebar. The results indicated that different quantitative indices for corrosion evaluation could be created based on this method, and an index created by two transformations with the same geometric characteristics had better quantification capability. The four quantitative indices I 1 , I 2 , I 3 , and I 4 created in this study were all linearly related to the rebar localized corrosion cross-sectional area ratio S , and index I 3 had the relatively best quantitative capability and applicability. This quantification method provided an innovative solution for the non-destructive quantitative evaluation of rebar corrosion. • The dynamic linkage mechanism between the IM and SMFL fields of corroded rebar was demonstrated. • An SMFL-based non-destructive quantification method for the rebar corrosion degree was proposed. • Four quantitative indices were created based on this quantification method. • All of the created quantitative indices were linearly related to the corrosion cross-sectional area of rebar. [ABSTRACT FROM AUTHOR]

• The maximum value of the axial leakage magnetic B x -max coincides with the variation of the broken wire parameter. • The sensitivity of each influencing factor to the value of B x- max and to its transverse coordinate is analyzed. The degree of wire breakage shows a good linear relationship with B x- max. The most unfavorable cross-section identification parameter X c is proposed. • The factors have an effect on the identification of the most unfavorable cross section. This effect can be reduced by correcting the most unfavorable cross section identification parameter X c. The self-leakage magnetic signal of 37 parallel steel wires was detected by using magnetic signal detection technology and equipment. Based on the theoretical and experimental data, the relationship between the magnetic signal characteristics and the influencing factors was analyzed. The magnetic signal characteristics of multi-point interleaved broken wires are explored. The results show that the characteristics of the self-magnetic flux leakage signal of parallel wires broken are related to the defect parameters of the broken wires. The influence of lifting height on the magnetic signal is less than 3.8 %. The influence rate of the detection angle path is under 8.3 %. By analyzing the measured magnetic signals, a method for identifying the most dangerous cross section is proposed, and this is modified and improved. The maximum identification error of the recognition error is only 5.6 %. [ABSTRACT FROM AUTHOR]