A Method of Pulsed Magnetic Testing for Discontinuities in Objects Made of Diamagnetic and Paramagnetic Metals Using a Magnetic Carrier

Abstract

Experimental dependences of the electric voltage U (t) across an induction magnetic head as it scans a magnetic carrier containing the recordings of magnetic fields due to artificial continuity defects in aluminum plates with a thickness from 1.5 × 10^–5 to 3.0 × 10^–3 m are presented. The strength of the primary magnetic field in pulses created by a flat inductor varied in the range of (2–50) × 10³ A/m. The rise time of the pulses with field spikes was in the range (1.5–100) × 10^–6 s. A method for testing objects made of electroconductive materials has been developed that ensures the optimum geometrical dimensions of the inductor, the optimum amplitude, direction, rise time, and shape of the leading and trailing edges of the main field pulse, as well as the optimum amplitude, rise time, number, and polarity of field spikes. The method performs the operations of smoothing, computation, and extraction of desired signal with removal of background and recognizes information recorded on the magnetic carrier by comparing the obtained signal distributions with reference or design ones when establishing signals from minimum defects. The method improves the accuracy and increases the speed of testing by several times.