METHOD AND APPARATUS FOR NON-DESTRUCTIVE TESTING AND MAGNETOSTRUCTURAL MATERIALS INVESTIGATIONS.

摘要

A METHOD FOR MAGNETOSTRUCTURAL MATERIALS INVESTIGATION AND NON-DESTRUCTIVE MATERIALS TESTING OF DIAMAGNETIC, PARAMAGNETIC, FERROMAGNETIC AND FERRIMAGNETIC MATERIALS IS BASED ON THE MAGNETIZING AND DEMAGNETIZING OF A TEST SPECIMEN BY AN ALTERNATING MAGNETIC FIELD WHICH GENERATES AN INFINITESIMAL HYSTERESIS LOOP WITH A DIFFERENTIAL PERMEABILITY IN EACH PERIOD OF THE ALTERNATING MAGNETIC FIELD. A HALF-CYCLE OF THE PERIOD IS A MAGNETIZATION PULSE AND THE OTHER HALF-CYCLE OF THE PERIOD IS A DEMAGNETIZATION PULSE, THE LATTER HAVING THE SAME ENERGY CONTENT AS THE FORMER, BUT THE HALF-CYCLES ARE REGULATED SUCH THEY ARE ASYMMETRIC WITH RESPECT TO TIME AND MAGNETIC FIELD STRENGTH. DURING THE DEMAGNETIZATION THE COUNTERINDUCTION GENERATED BY ROTATION OF THE MAGNETIC DOMAINS OR GENERATED BY THE ALIGNMENT OF MAGNETIC MOMENTS IS DETECTED, IN SUITABLE MATERIALS ALSO THE BARKHAUSEN EFFECT AND PARAMETERS SUCH AS COERCIVE FORCE AND REMANENCE. THE DETECTION SIGNALS ARE RECORDED AND ANALYZED TO PROVIDE TIME-DERIVATED OR FREQUENCY-DERIVATED PARAMETERS FOR DETERMINING THE PROPERTIES OF THE INVESTIGATED MATERIALS, INCLUDING STRUCTURE, STRESS FIELDS, AND DEFECTS.(FIG. 1)