Numerical prediction of operating conditions for magnetic flux leakage inspection of moving steel sheets

Optimal operating conditions for magnetic flux leakage inspection of moving steel sheets are predicted by using a 2-D finite element model and a time step algorithm. Through numerical modeling of motional induction phenomena, sensor signal variations due to different velocities are investigated. Results show that changes in specimen velocity affect the base signal level and the peak to peak (P-P) signal, but their variations are not proportional to the velocity. Also found is that the sensor position where the maximum P-P signal appears changes its location to the direction of specimen motion as the velocity increases. These results made it possible to decide optimal operating conditions, such as the velocity of steel sheet and the sensor location, to obtain the maximum signal to noise ratio.