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Fine wire rope is a type of skeleton material that is used widely in elevator steel belts, conveyor belts, and synchronous belts. When the tension of a fine wire rope changes abnormally, its service life and the safe operation of the system it belongs to will be seriously affected. Therefore, it is particularly important to monitor the tension and detect the defects of fine wire rope. However, traditional nondestructive testing technology only detects the defects or monitors the tension of the tested structure. In this article, longitudinal guided wave sensors are used to measure the tension changes and defects of fine wire rope. When the tension of a fine wire rope changes, the natural frequencies of the fine wire rope change, so the change of natural frequencies of fine wire rope can be used to represent the change of tension. White noise is used to measure the natural frequencies of fine wire rope under varying tension using a low-power circuit to determine the influence of the change of fine wire rope tension on the natural frequencies. Meanwhile, the excitation frequency needed to produce the maximum amplitude of the guided wave is determined according to the natural frequencies detection results to improve the signal-to-noise ratio of the guided wave signal. Additionally, defect detection is realized by analyzing the wave velocity and time of flight of the guided wave signal. [ABSTRACT FROM AUTHOR]

The loss of metallic area is the most important factor affecting the quality of wire ropes. Therefore, it is very important to detect the loss of metallic area values of wire rope defects quickly and accurately. At present, the main flux detection approach is one of the most effective methods, and the detection signal is related directly to the metal cross-sectional area of the wire rope. However, when the defect width is less than a specific value, the existence of the leakage magnetic field means that the amount of the magnetic flux change is not only related to the loss of metallic area of the defect but also has a complex nonlinear relationship with the defect width. The resulting calculation is highly complex and means that the loss of metallic area cannot be determined quickly and quantitatively. This article presents an in-depth study of the theoretical basis of magnetic flux detection, analyzes the problems of the main magnetic flux detection method and their causes, and proposes a method to improve main magnetic flux detection using the axial magnetic flux density. Simulation analysis and experimental results show that the method presented in this article can be used to calculate the loss of metallic area values of defects quickly and accurately without the need for complex calculation processes. [ABSTRACT FROM AUTHOR]

The magnetostrictive torsional wave sensors are focused on magnetostrictive patch transducer. These transducers use a material with a high magnetostrictive coefficient on the pipe surface to increase the excitation efficiency for detection. However, this approach loses the noncontact characteristic of the magnetostrictive guided waves. To enable noncontact detection in small-diameter pipes using torsional waves, a magnetostrictive torsional wave sensor with a tile-shaped magnet is designed in this article. By optimizing the structure of the static magnetic field, the circumferential magnetic field of the pipe is enhanced. The amplitude and the signal-to-noise ratio of the guided waves are also improved. The tile-shaped magnet with shoving magnetic structure is used to realize a uniform circumferential magnetic field. A solenoid coil is used to provide the axial dynamic magnetic field to generate the torsional waves that are used to detect the pipes. In this article, the principles of torsional wave sensors are studied first. The static magnetic field results for different structures are then analyzed via simulations. Finally, experiments show that the magnetostrictive torsional wave sensors with the tile-shaped magnets can realize the excitation and detection of torsional waves in pipes, which can be used to detect the locations and sizes of defects in these pipes. [ABSTRACT FROM AUTHOR]

Wire rope is a chain structure, and the strength of the weakest link is the strength of the entire wire rope. The axial resolution of loss of metallic cross-sectional area (LMA) detection using the induction coil is related to the length of the detection probe, which is usually greater than or equal to the length of the probe. Improving the axial resolution is an important technical indicator of the LMA. In this article, through theoretical analysis based on the principle of magnetic aggregation and 3-D transient magnetic field simulation, a particular kind of magnetic aggregation structure used for winding coil is proposed and optimized. Simulation and experimental results show that for wire rope LMA detection adding the proposed magnetic aggregation structure, the defect signals’ signal-to-noise ratio (SNR) is improved and the axial resolution of the LMA is increased to 20 mm. At the same time, the cross-sectional area loss can be quantitatively evaluated by the magnetic flux peak-to-peak value. The difference between the maximum and minimum values of the derivative of the magnetic flux signal can be used to evaluate the defect length. [ABSTRACT FROM AUTHOR]

Magnetostrictive guided waves are widely used in nondestructive testing and structural health monitoring of pipes to ensure their integrity. These guided waves are mechanical waves, and if the natural frequencies of the pipe are used as excitation frequencies, the mechanical vibration amplitude can be enhanced, which will then improve the amplitude of the guided waves. Comparison of the various methods to determine the natural frequencies of pipes shows that the white noise signals remain relatively smooth in both time and frequency domains. White noise has a wide bandwidth and uniform energy distribution. It does not require high energy within a short time period, so it is easy to generate. In this article, white noise is used to determine the natural frequencies of pipes. Comparison of the white noise spectra produced by analog and digital circuits shows that the energy spectrum of white noise produced by the analog circuit is high and uniform, so the analog circuit is used as the white noise source and this noise is loaded onto a magnetostrictive sensor. The detected signal spectrum is then analyzed and the frequencies with high power density spectra are determined to be the natural frequencies. The natural frequencies of the pipeline detected using white noise are compared with the results of modal analysis. Simulation results and experimental results demonstrate that the use of white noise allows the natural frequencies of pipes to be determined quickly and accurately. These natural frequencies can be used in magnetostrictive guided-wave nondestructive testing. [ABSTRACT FROM AUTHOR]

As a rapid, noncontact, and nondestructive technology, magnetostrictive guided waves have been widely used for the quality inspection of pipes and stay cables. Traditionally, a single-frequency signal with a high amplitude and a long pulse duration is used to increase the excitation energy and detection distance. However, the longer the pulse duration of a single-frequency signal is, the lower the resolution of adjacent defects and the accuracy of defect location will be. A novel method of addressing this problem is proposed in this paper. An encoded multifrequency excitation signal, whose frequency range is selected from a calculated dispersion curve, is used to excite the guided wave. After passing through the signal-conditioning board, the detected defect signals are sampled, averaged, and then filtered using a matched filter. In this manner, the pulse width of echoes can be greatly compressed. Our experimental results demonstrate that our proposed method can improve the resolution of adjacent defects and the accuracy of defect location in the propagation direction of the magnetostrictive guided wave. [ABSTRACT FROM AUTHOR]