Patent ID: 9170234
Filing Date: 2015-10-27
Classification: G01N

Abstract:
1. An apparatus for detecting a defect, comprising: an induced current applier applying surface currents to an object that is to be measured by using ACs (alternating currents) having a frequency varying depending on a depth to be measured; a magneto-electric converter sensing a magnetic field generated from the object due to the surface currents and generating a magnetic field sensing signal corresponding to a strength of the magnetic field; a signal processor filtering and amplifying the magnetic field sensing signal and outputting a signal corresponding to an amplitude of the filtered and amplified magnetic field sensing signal; a signal converter converting the signal output from the signal processor into a digital signal; and a data processor quantitatively converting the strength of the magnetic field generated from the object into a numerical value based on the digital signal output from the signal converter, wherein the induced current applier comprises an AC power supplier generating the ACs; at least one first coil transmitting the ACs; at least one core on which the first coil is wound, and the core in which a varying magnetic field is induced by the ACs; and at least one conductive plate in which the surface currents are induced by the varying magnetic field, and the at least one conductive plate applying the surface currents to the object, wherein the data processor calculates an amplitude of the magnetic field generated from each position of the object, a differential value dB/dx of the amplitude of the magnetic field with respect to a horizontal direction of induced currents in the object, a differential value dB/dy of the amplitude of the magnetic field with respect to a vertical direction of the induced currents, and a differential value dB^2/dxdy of the amplitude of the magnetic field with respect to horizontal and the vertical directions converts the amplitude of the magnetic field and the differential values of the amplitude of the magnetic field into numerical values, and quantitatively analyzes defects of the object, wherein the at least one conductive plate consists of a plurality of plates, the plurality of plates are linked so as to form loop, and one of the plurality of plates is adhered to the object, wherein B is the amplitude of the magnetic field, x is displacement of the horizontal direction of the induced currents, and y is displacement of the vertical direction of the induced currents.