Abstract
A flexible or planar eddy current probe with a differential structure can suppress the lift-off noise during the inspec-tion of defects.However,the extent of the lift-off effect on differential probes,including different coil structures,varies.In this study,two planar eddy current probes with differential pickup structures and the same size,Koch and circular probes,were used to compare lift-off effects.The eddy current distributions of the probes perturbed by 0° and 90° cracks were obtained by finite element analysis.The analysis results show that the 90° crack can impede the eddy current induced by the Koch probe even further at relatively low lift-off distance.The peak-to-peak values of the signal output from the two probes were compared at different lift-off distances using finite element analysis and experimental methods.In addition,the effects of different frequencies on the lift-off were studied experimentally.The results show that the signal peak-to-peak value of the Koch probe for the inspection of cracks in 90° orientation is larger than that of the circular probe when the lift-off distance is smaller than 1.2 mm.In addition,the influence of the lift-off distance on the peak-to-peak signal value of the two probes was studied via normalization.This indicates that the influence becomes more evident with an increase in excitation frequency.This research discloses the lift-off effect of differential planar eddy current probes with different coil shapes and proves the detection merit of the Koch probe for 90° cracks at low lift-off distances.
基金项目
Gansu Provincial Natural Science Foundation of China(22JR5RA229)
国家自然科学基金(51807086)
国家自然科学基金(12162021)
Hongliu Youth Found of Lanzhou University of Technology()
Gansu Provincial Outstanding Graduate Student Innovation Star of China(2021CXZX-453)
NETL
NSTL
万方数据