In-Situ Quantitative Monitoring of Crack Propagation with Flexible Eddy Current Sensor

Aiming at the disadvantages of traditional flexible eddy current array sensors such as large number of sensing channels and low crack monitoring depth, a tunnel magnetoresistance (TMR) flexible eddy current array sensor (TMR-FECA) with less induction channels is proposed to quantitatively monitor structural surface and subsurface cracks. Simulation experiments on the propagation of cracks in different depths verify that the method of using TMR sensor to measure the y-axis magnetic field component has a better quantitative crack monitoring effect. Through 2-D finite element model established by Comsol software, the effects of different excitation frequencies on the eddy current distribution and the sensitivity of crack identification are analyzed. The experimental results show that the TMR-FECA has good quantitative monitoring effect for surface crack monitoring, and the sensitivity of crack monitoring increases with the excitation frequency. As the excitation frequency increases from 1 kHz to 5 kHz, the crack identification sensitivity increases from 108.41% to 741.64%. For the subsurface cracks 2 mm beneath the surface, when the excitation frequency is 1 kHz, the quantitative crack monitoring effect is not obvious, but the quantitative crack monitoring effect and the sensitivity of crack monitoring can be improved by increasing the excitation frequency. The crack monitoring accuracy of the sensor is 5 mm, which is consistent with the spacing between the excitation lines. This technique can effectively reduce the number of induction units and solve the quantitative monitoring problem of deep cracks. © 2021, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.