Eddy current testing method and apparatus for inspecting an object for flaws

摘要

In an eddy current testing method which involves using a rotatable eddy current testing probe in which a detection coil is arranged within an exciting coil, a change in detection sensitivity (a deviation of detection sensitivity) which changes depending on the rotational position of the detection coil is reduced. The eddy current testing probe includes an exciting coil EC1, a detection coil DC1, an exciting coil EC2 and a detection coil DC2, which are mounted on a disk DS. The eddy current testing probe is placed so as to face a circumferential surface of an object to be inspected T, which is in the shape of a circular cylinder, and the disk DS is rotated. Then, the distance (liftoff) between the detection coils DC1 and DC2 and an inspection surface changes. Therefore, also the detection sensitivity to a flaw signal changes. To reduce the change in detection sensitivity, the detection sensitivity is adjusted by detecting the rotational position (rotational angle) of the detection coils DC1 and DC2.

主权项

1. An eddy current testing method which involves for rotating an eddy current testing probe in which a detection coil is arranged within an exciting coil so that coil planes of the both coils are orthogonal to each other, and testing an object to be inspected in which a liftoff between an inspection surface of the object and the detection coil changes depending on a rotational position of the detection coil, comprising the steps of:
setting a detection sensitivity to a flaw signal at a predetermined rotational position of the detection coil as a reference value of detection sensitivity; and adjusting a detection sensitivity to a flaw signal at a rotational position of the detection coil based on the reference value of detection sensitivity, wherein the inspection surface of the object has a predetermined curvature so that the liftoff oscillates between a maximum value and a minimum value in a continuous fashion depending on the rotational position of the detention coil.