Defect identification method, and array detection probe

An alternating current field based defect identification method, performed by an array detection probe, comprising the following steps:

• step one:
• enabling the array detection probe to conduct parallel scanning along a surface of a workpiece, and obtaining a magnetic field Bx signal in direction X and a magnetic field Bz signal in direction Z;
• step two:
• extracting a background magnetic field at a defect-free position of the workpiece, separately removing a background magnetic field of each of the magnetic field Bx signal in the direction X and the magnetic field Bz signal in the direction Z from the background magnetic field at the defect-free position, and obtaining a magnetic field Bx1 signal in the direction X and a magnetic field Bz1 signal in the direction Z without background magnetic fields;
• step three:
• using a position of the array detection probe as X-axis data, a position of a sensor array as Y-axis data, and an amplitude of a collected magnetic field signal as Z-axis data, and drawing an array image of the Bx1 signal and an array image of the Bz1 signal according to the magnetic field Bx1 signal in the direction X and the magnetic field Bz1 signal in the direction Z without background magnetic fields;
• and
• step four:
• locating a distortion zone corresponding to disturbance at the same time and position in the array image of the Bx1 signal and the array image of the Bz1 signal;
• determining whether distortion signals obtained by different sensor units of the sensor array in the distortion zone are all perpendicular to an X axis;
• and determining that the distortion signals are lift-off signals if the distortion signals are all perpendicular to the X axis, and otherwise, determining that the distortion signals are defect signals, wherein the array detection probe used in the defect identification method comprises:
• a probe housing, a lemo connector, the sensor array, an excitation device, and a signal conditioning circuit;
• the lemo connector is mounted on one side of the probe housing for signal transmission;
• the sensor array, the excitation device and the signal conditioning circuit are all mounted in the probe housing;
• the excitation device comprises an excitation coil and a U-shaped magnetic core, and the excitation coil is uniformly wound around the U-shaped magnetic core and is configured to generate a uniform induced electromagnetic field on a surface of a workpiece to be tested;
• the sensor array is mounted directly below the excitation device, and comprises n groups of sensor units, wherein n≥3;
• the sensor units are arranged between two legs on a lower portion of the U-shaped magnetic core, and are uniformly and equidistantly arranged in a cross beam direction of the U-shaped magnetic core;
• each group of sensor units consists of a tunnel magnetoresistance (TMR) magnetic sensor having an X-axis sensitive direction and a TMR magnetic sensor having a Z-axis sensitive direction;
• and the signal conditioning circuit is mounted above the excitation device and configured to amplify and filter a signal output by the sensor array.