Development And Test Of The AC Field Detection Instruments

The alternating current field measurement (ACFM) is an emerging electromagneticnondestructive testing. The technology is based on the amount of induced magneticfield intensity of disturbance to detect the surface of the metal member and near surfacecracks, and can measure the length of the crack, and calculating the depth of the crack.Has a very broad application prospects in the petrochemical, offshore platforms,underwater equipment in service inspection, shipping and aviation manufacturing.This paper describes the study of the status of the alternating current fieldmeasurement technology at home and abroad, on the basis of the principle ofelectromagnetic induction, given ACFM detection principle and mathematical model."Incentive" type three-dimensional finite element model of the rectangular coil andrectangular slot defects, through harmonic analysis, the defect distribution, size andmagnetic field perturbations corresponding relationship.Secondly, according to the characteristics of the alternating current fieldmeasurement, design the hardware circuit for alternating current field measurementinstruments and software systems.AC electromagnetic field detector hardware design, including the design of thedetection probe, signal conditioning circuit design, circuit design lower MSP430mixedsignal processor-based machine control. Signal conditioning circuitry includeslow-noise programmable gain amplifier, adaptive band-pass filter circuit, the post-gainthe adjustable amplifier circuit, True RMS conversion circuit composed of four parts.AC electromagnetic field detector software systems, including lower computersoftware based on the C language, and two parts based on the graphical programminglanguage Labview develop PC software.Using the design of the AC electromagnetic field detection equipment, respectively,the artificial defects of different material properties of the rectangular groove the testpiece and the air compressed cans on the seam detection, the detection result of thedefect by the magnetic particle testing contrast, and verify the accuracy of the designinstrument and reliability.Finally, the non-ferromagnetic material workpiece, for example, through thedetection of known length and depth of the aluminum rectangular groove artificialdefect specimen constructed aluminum AC electromagnetic field defect detectionquantitative evaluation of the integrated parameter system.