Eddy current testing for weld defects with different directions of excitation field of rectangular coil

The directional property of the rectangular coil leads to different characteristics in eddy current testing (ECT) under various directions of excitation field. This paper applies the method to test and analyze the weld seam defects by placing the direction of the excitation coil perpendicular to and parallel with the seam. The results show that compared with the method in which the field is parallel with the seam, the method in which the field is perpendicular to the seam is less influenced by the shape change in the specimen. Although the experiment is affected by both the coarse surface and the shape change of the specimen, the result still implies that ECT is capable of testing and positioning the subsurface defect with diameter smaller than 1mm.