DETECTION OF INTEGRITY DEFECTS IN ALUMINUM SPECIMENS BY THE MAGNETIC PULSE METHOD

Abstract

Experimental time dependences of the electric voltage U(t), taken from the induction magnetic head when scanning it with a magnetic carrier with magnetic field records of artificial defects of the integrity (slits) with a width of (1.0 - 10.0) x 10-5  m in aluminum plates from 1.5 x 10-6 to 2.0 x 10-3 m are presented. On the magnetic carrier the magnetic fields of the defects that occur when aluminum plates are exposed to a pulse of magnetic field of plane inductor (action time of about 1.0 x 10-4 sec). Dependences of U(t) for different depths of bedding of the defects and thickness of the layer of the material above them in the specified ranges of influences are obtained. In this case, distributions of instantaneous magnetic fields are recorded on the surface area of objects of the order of 1.0 x 10-3 m2 with a resolution in the measurement plane of 1.0 x 10-8 m2. The novelty of the method consists in determination of the amplitude of the main pulse of the field and build up time, the shape of the leading and trailing edges, as well as the amplitude, build up time, the number and polarity of the outliers of magnetic field, direction of the applied field, operations of smoothing, calculation, separation of the useful signal and operations of recognition of the defect information recorded on the magnetic medium with analysis of the dependences U(t). The developed method for controlling objects from electrically conductive materials makes it possible to increase several times the accuracy and speed of the control of the integrity defects in diamagnetic and paramagnetic metals.