Abstract
The present study investigated crack visualization in metallic structures using time-domain reflectometry (TDR) with differential circuit of microstrip line (MSL). It was problematic that single ended of two-dimensional (2D) MSL was affected by the cross talk voltage because of the interference of adjacent MSL. Differential circuit enables to suppress the cross talk voltage by taking the difference. Crack visualization experiments were conducted using the proposed TDR with differential circuit of 2D MSL for different crack lengths. The experimental results demonstrated that crack propagation could be clearly visualized by determining the appropriate threshold. To observe the time change of the electric field, the electromagnetic fields of the differential circuit was numerically simulated using the finite-difference time-domain method. The simulation results clarified that the cross talk voltage decreased, because the electric field of the differential circuit caused by interference of adjacent MSL was in phase and obtained the visualization result like the experiment.
