The spheroidal cast iron is widely used in many purposes, especially for high stressed parts. It is very difficult to detect the internal defect of such cast iron products, by means of NDT equipment. In the case of overloading or low cycle fatigue, the stress-strain behavior is observed in loading state but the life is determined for the failure, while outer cracks could be found easily. The MDK sensor is a kind of elector-magnetic detector using the inductive coils, like the Eddy-current sensor. In this research, a MDK Magnetic Sensor is used to inspect the microscopic plastic deformation or cracks around graphite nodules, and the relations between the loading or deformation and the MDK value. The availability of the MDK Sensor for the nondestructive determining of low cycle fatigue of the SGCI is discussed.
