Magnetic Flux Leakage Sensing-Based Steel Cable NDE Technique Incorporated on a Cable Climbing Robot for Bridge Structures

Abstract

In this study, an automated cable monitoring system using a NDE technique and a cable climbing robot is proposed. MFL (Magnetic Flux Leakage- based inspection system was applied to monitor the condition of cables. This inspection system measures magnetic flux to detect the local faults (LF) of steel cable. To verify the feasibility of the proposed damage detection technique, an 8-channel MFL sensor head prototype was designed and fabricated. A steel cable bunch specimen with several types of damage was fabricated and scanned by the MFL sensor head to measure the magnetic flux density of the specimen. To interpret the condition of the steel cable, magnetic flux signals were used to determine the locations of the flaws and the level of damage. Measured signals from the damaged specimen were compared with thresholds set for objective decision making. In addition, the measured magnetic flux signal was visualized into a 3D MFL map for convenient cable monitoring. Finally, the results were compared with information on actual inflicted damages to confirm the accuracy and effectiveness of the proposed cable monitoring method.

Real-time quantitative evaluation on the cable damage of cable-stayed bridges using the correlation between girder deflection and temperature

“…The simulated values of D 1 ðtÞ, D 2 ðtÞ, Δl 1 ðtÞ, and Δl 2 ðtÞ are shown in Table 3. The values of v 1 ðtÞ and v 2 ðtÞ are further calculated by substituting the values of D 1 ðtÞ, D 2 ðtÞ, Δl 1 ðtÞ, Δl 2 ðtÞ, Φ, Ψ, and PðtÞ into equation (19), as shown in Table 3. Finally, g 1 ðtÞ and g 2 ðtÞ are evaluated using equation ( 14), as shown in Table 3.…”

“…Currently, the available techniques to evaluate cable damage mainly include vibration frequency technique, acoustic emission technique, magnetic flux leakage technique, fiber brag grating (FBG) technique, etc. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] For vibration frequency technique, it is commonly used in practice because of its simplicity and speediness. The frequency or cable force is calculated from the monitoring acceleration data of stay cables, and then the abnormal change of frequency or cable force is used for identification of cable damage.…”

“…However, this technique is greatly affected by temperature field and electromagnetic field, and it also needs to be specially equipped with autonomous cableclimbing devices, so there are still some difficulties in damage quantification. 17,19,22 For fiber brag grating technique, FBG sensors are pasted on the surface of steel wires in stay cables, and the changes of stresses measured by FBG sensors are analyzed to evaluate cable damage. [23][24][25][26] For example, some FBG sensors were pasted on the steel wires to evaluate the cumulative fatigue damage of stay cables of Tianjin Yonghe Bridge.…”

Localization and quantification of partial cable damage in the long-span cable-stayed bridge using the abnormal variation of temperature-induced girder deflection

“…For MFLM, in addition to its high cost, the determination of the relationship between magnetic properties and cable strain limits the application of this method . Besides, some technical problems such as temperature compensation of magnetic flux sensors, shielding effect of steel strands in the outer layers and sensor calibration are still not maturely solved, and one cable‐climbing device may be needed to climb along the long stay cable to detect the possible magnetic flux leakage . For FBGM, the FBJ sensors embedded in the stay cables are subjected to high stress levels, which are prone to failure due to their fragility, and moreover, the difficult accessibility and high cost for future replacement of damaged sensors is another disadvantage .…”

Signal Analysis of Broken Wires Fault with Different Width

“…The principle of the magnetic flux leakage (MFL) detection is the change of the leakage magnetic field on the surface of wire ropes. Generally, wire ropes are magnetized by permanent magnets in the first stage then, magneto-dependent sensors, such as inducting coils or Hall sensors are used to detect the faults of wire ropes [4].…”