Abstract
A method for inspecting far-side fatigue cracks is proposed. These cracks occur in the spot-welding components of a heat-resistant alloy, used in aircraft engine components. For measurement without contact, an electromagnetic field is applied to the object. The distortion of the field owing to far-side fatigue cracks in the spot-welding area is measured with a linearly integrated giant-magneto resistance sensor array. Artificial far-side cracks can be detected where there is a slit-type crack around the spot-welding area. A probability of detection (POD) is used to analyze the detection performance of the inspection system. Crack with lengths of 3.699 mm and 4.647 mm were inspected with 90% POD and 90/95 POD with confidence bound, respectively.