An integral formulation has been developed to calculate the interaction of an ideal crack with transient eddy currents in a conductor. By using the moment method, the integral equation for the field at the crack is approximated by a matrix equation and a numerical solution computed. The discontinuity in the field at the crack is expressed in terms of a current dipole density. The dipole distribution is approximated by a discrete form and the numerical approximation used to predict the external magnetic field. The results show a that the signal response is sensitive to the distance from the crack edge to the surface of the conductor. A maximum signal is obtained in the region where this distance is smallest and the time taken to reach this maximum is dependent on the ligament size.
展开▼
