A detection of backside crack using rotational magnetic flux sensor with search coils

We have developed a new magnetic sensor using a rotational magnetic field with a three-axis search coil for non-destructive testing (NDT). Using specimens with a machined crack in the center, we investigated the relationship between the position end the depth of a crack and the output signal of the three-axis search coil. The results of our experiments, this sensor can clearly detect a crack existing on the reverse side of the sensing surface. In this paper, we present the construction, results of numerical analysis and experimental results of this sensor.