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

An eddy current testing method 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 corresponding to the liftoff depending on a predetermined rotational position of the detection coil as a reference value of detection sensitivity;
• and
• adjusting a detection sensitivity to a flaw signal corresponding to the liftoff depending on 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 detection coil.

An eddy current testing apparatus which comprises a rotatable 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 tests 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:

• a detection device of rotational position which detects a rotational position of the detection coil;
• and
• an adjustment device of detection sensitivity which sets a detection sensitivity to a flaw signal at a predetermined rotational position of the detection coil as a reference value of detection sensitivity and adjusts a detection sensitivity to a flaw signal at a rotational position detected by the detection device of rotational position 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 coil.

An eddy current testing apparatus which comprises a rotatable 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 tests 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:

• a liftoff detection device which detects the liftoff depending on the rotational position of the detection coil;
• and
• an adjustment device of detection sensitivity which sets a detection sensitivity to a flaw signal corresponding to the liftoff depending on a predetermined rotational position of the detection coil as a reference value of detection sensitivity and adjusts a detection sensitivity to a flaw signal corresponding to a liftoff detected by the liftoff detection devise 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 detection coil.