Defect detection for metal plates based on time-domain signal and frequency-domain signal analysis

ZHANG Xue-tong1， LI An-yang1， CHEN Li-jing2， ZHAO Qian2， CHEN Li-ting1，
HE Min1， YIN Wu-liang2
（1. School of Logistics Engineering， Shanghai Maritime University， Shanghai 201306， China；
2. School of Electrical Engineering &Automation， Tianjin University， Tianjin 300072， China）

Abstract： Electromagnetic eddy current testing technology as a new nondestructive testing technology is widely used in the aerospace，manufacturing and other fields. Aiming at studying electromagnetic eddy current testing technology in the measuring of the flaws of metal system，a detecting flaws of metal system based on field programmable gate array（FPGA）designed early days was used，experiments were conducted on metal plates with flaws of different lengths，depths and material properties， time-domain signal was achieved when electromagnetic sensor across the defective area of the metal plate. By means of analyzing the real part and the imaginary part of the time-domain signal and frequeency-domain signal，the relationship between flaws of metal and amplitude change of signal was established. Synthesized the characters of the two signals，the results indicate that both the surface and internal flaws can be detected more precisely with this system.
Key words： eddy current sensor； flaw detection； field programmable gate array（FPGA）； frequency-domain analysis； quadrature demodulation