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Steel wire rope can be frequently damaged by various factors. Although weak defect signal detection is the key to guarantee safety, current classic stochastic resonance (SR) models and methods are unavailable due to the complicated interference of noise. Thus, in this article, a novel E-exponential SR model and weak signal detection method are proposed. The principle of this model is first introduced from the perspective of Taylor expansion and nonlinear system analysis. Then, the model performance is simulated and evaluated by output signal analysis and chaos characterizations. Afterward, model comparison with different system parameters, experiments, and case studies regarding three typical wire rope defects inspection and weak signal recognition is conducted to demonstrate the validity of the novel method. Finally, the advantages and limitations of the proposed SR model are discussed. [ABSTRACT FROM AUTHOR]

In oil mining system, stress cracks on thread usually lead to drill pipe failure. To maintain normal operation of drill pipes, the thread needs to be nondestructively tested. However, due to complicated structure, it is challenging to identify and quantify the cracks the using existing nondestructive testing (NDT) methods. In this article, a scanning induction thermography (SIT) system for automatic detection of drill pipe thread (DPT) is presented. Specifically, a profiling heating method (PHM) is proposed to produce uniform heating on the root part of thread tooth where most of the stress cracks occur. A weighted least squares fitting (WLSF)-based difference algorithm is used to eliminate the background temperature of scanning data. The algorithm can extract crack thermal response with the influence of lift-off distance change and marginal effect of electric field in SIT. Experiments show that the proposed system can obtain 3k thermal contrast between crack and defective-free area when testing the crack with only 0.3 mm depth. Three SIT systems with other heating methods are also used for comparison. Better heating uniformity, signal intensity, robustness of structural change, linear property with depth information, and signal consistency when testing similar cracks in different areas of the root part can be demonstrated in the proposed system. [ABSTRACT FROM AUTHOR]

Smart sensing of the surface roughness values is of great importance for intelligent manufacturing when online surface roughness measurements are essential in optimizing the machining processes. In this article, the magnetic flux leakage (MFL) method is applied to assess the roughness of triangle array surfaces, which may result from milling, turning, and planing. The leakage magnetic field (LMF) distribution is obtained by the magnetic dipole theory. The Fourier transform (FT) method is adopted to obtain the spatial spectrum functions of the LMF. Surface topography parameters are characterized from the first pulsed position and the correlation coefficient in the spatial spectrum domain. A magnetic recording head is designed for experimental verification. The results show that the relative errors of the surface roughness values are less than 13%. In addition, a portable probe used for roughness measurements is developed for a machining tool with an electromagnetic fixture. Fourier transform (FT), electromagnetic fixture, magnetic flux leakage (MFL), spatial spectrum, surface roughness. [ABSTRACT FROM AUTHOR]

Eddy current array testing (ECAT) is a useful tool in evaluating defect sizes. However, it is difficult for ECAT to evaluate the inner defects in ferromagnetic materials due to thin skin effect. In this article, direct current (dc) magnetization-based ECAT (DCMECAT) is proposed to quantify buried defects existing in the inner surface of steel plates. Relying on permeability disturbance in the defect vicinity, DCMECAT can build links between the testing signals and defect sizes. The results show that the performance of evaluating defect sizes is better under the saturated magnetization state. Further, three features, i.e., the signal width, the peak voltage, and the contour orientation, are proposed to evaluate the width, the depth, and the orientation of defects, respectively. Relationships between features and defect sizes are investigated by using least-squares regression. Further, a testing example is shown in this article, and the evaluation error is 14%. [ABSTRACT FROM AUTHOR]

The traditional magnetic flux leakage (MFL) method with a single magnetic excitation source has been widely used in engineering practice but fails in long-range (long liftoff distance of the sensor from the surface of the tested object) defect detection, especially when the liftoff distances increase. Thus, we propose a novel electromagnetic testing method based on the magnetic field interaction between the primary magnetic induction field and the secondary field of MFL. The principles of the new method are first introduced, and the method is compared with the common MFL methods; this comparison indicates that the new method has the capabilities of long-range defect detection and signal strength enhancement. Furthermore, a series of simulations and analyses demonstrates that the proposed method is more efficient in defect detection, particularly when the induction magnet is a diamagnetic material, which is independent of the coercive force. Finally, experiments and comparisons were conducted to verify the feasibility and reliability of our proposed method in the long-range defect detection. All results show that the novel method has great promise in widely practical applications in the future. [ABSTRACT FROM AUTHOR]

As an efficient non-destructive testing method, magnetic flux leakage (MFL) has been widely used for damage detection in ferromagnetic materials. The magnetic dipole theory is a traditional method to calculate the magnetic leakage field. In this paper, the magnetic leakage field functions of a slot in a 2-D infinity plate are obtained using the magnetic dipole theory. Equations of the magnetic leakage field are converted into the convolution of two other functions. Spatial spectral equations of the MFL are developed according to the convolution theorem using the Fourier transform (FT) method. The results are analytical functions different from other numerical methods, such as the discrete FT and fast FT methods, and the calculation speed is fast. The results show that the $y$ -component of the magnetic leakage field has 90° phase shift with the $x$ -component. This result has clear physical significance compared with the traditional MFL equations using the magnetic dipole theory. Different spatial spectral curves for different defects are presented in this paper. Since there is a sinc function for the width value in the equation, the width value can be deduced from the first zero-crossing point in the spatial spectrum curves. A new method is proposed to determine the width value using the relationship $w =1/f_{s}$ , where $f_{s}$ is the first zero cross point. Two specimens with different cracks are investigated, and the experimental results show this method can be used as an inverse MFL data interpretation technique. [ABSTRACT FROM AUTHOR]

In order to detect tiny cracks in bearing rings, a high-sensitivity magnetic flux leakage (MFL) method based on magnetic induction head is proposed and investigated in this paper. First, the MFL sensing method based on magnetic induction head is theoretically illustrated. A magnetic core with an open gap is applied to guide leaked magnetic flux into a detection magnetic circuit, where an induction coil is placed to detect the change of the magnetic flux. To obtain an optimal gap width for higher sensitivity, its influence on MFL sensitivity is analyzed by building magnetic circuits. Then, to realize automatic inspection for bearing rings, a U-shape magnetizer is proposed and 3-D numerical simulations are conducted to investigate the signal characteristics of the proposed method and the sensitivity affected by gap width. Furthermore, MFL experiments for bearing rings were performed and it was found that the proposed method has high sensitivity for tiny cracks and when the gap width is approximately equal to the width of the crack, the greatest sensitivity will be obtained. Finally, the automatic MFL testing system for bearing rings is designed and employed in the production line. In-line tests show that the novel MFL system can fulfill the inspection requirement for bearing rings. [ABSTRACT FROM PUBLISHER]

Eddy current effect essentially occurs when a relative movement happens between steel pipes and the circumferential magnetizer in high-speed magnetic flux leakage (MFL) testing. To improve the MFL testing for longitudinal defects, the effect of motion-induced eddy current (MIEC) on circumferential magnetization is analyzed. First, in terms of Maxwell equations, the eddy current effect and the MIEC distribution in the steel pipe are analyzed. Then, the finite-element simulations are conducted to investigate the MIEC distribution, the magnetization status change, and the sensitivity difference. With the rotational speed increasing, the MIEC and circumferential magnetic flux density gradually become asymmetrical and non-uniform. The MFL testing signal amplitudes of external and internal defects in the arriving and leaving parts change in different variation trends. Finally, the relevant high-speed MFL testing experiments for steel pipes are performed to confirm the effect of MIEC. The experimental results match well with the theoretical analysis and numerical simulation results. [ABSTRACT FROM AUTHOR]

To improve the accuracy of the magnetic flux leakage (MFL) nondestructive testing in practical applications, we analyzed the MFL signal characteristics affected by discontinuity orientation and sensor-scanning direction. On the basis of magnetic dipole theory, the descriptions for the MFL field distributions of discontinuities in arbitrary orientations were established, indicating that the MFL density increases with the discontinuity orientation increasing from 0 to $\pi $ /2 and that magnetic flux always flows through the discontinuity perpendicularly, which was verified by relevant experiments. Further, the influence of the sensor-scanning direction on MFL signal features was analyzed and it was found that the MFL component signal parallel to scanning direction increases, the MFL component signal perpendicular to scanning direction falls, the MFL component signal perpendicular to discontinuity stays the same, and the widths of test signals become narrow, when the angle between the discontinuity orientation and sensor-scanning direction increases. [ABSTRACT FROM AUTHOR]

To enhance the signal intensity of magnetostrictive position sensor (MPS), a new method of bipolar pulse excitation (BPE), and a new structure of single-end damper (SED) are proposed in this paper. Two torsion strain waves, named as W1 and W2 waves, are generated by the BPE, and the W1 wave is reflected (changed into RW1) by the SED. Based on the principle of wave superposition, the interference between RW1 and W2 is realized by adjusting the structure parameters of the sensor. Therefore, the MPS signal is strengthened 1.8 times approximately as well as the measuring range. The notable difference between the new strategy and the conventional one lies in the reflection wave. In conventional MPS, the smaller the reflection wave is, the better the signal will be. However, the reflection wave should be as strong as possible in the new strategy. After the explanation of BPE and SED, a new model is presented. The validity and feasibility of the proposed strategy are verified by experiments. Finally, the characteristics of BPE and SED, such as the measured object, the polar of excitation pulse, and the limit of signal, are discussed in detail. Research results indicate that the proposed BPE method and SED structure are innovative development to conventional MPS, and are of great practical value. [ABSTRACT FROM PUBLISHER]