基于PECT-EMAT复合检测方法的铁磁性材料的复合缺陷检测

Ferromagnetic materials are widely used in the structures of modern energy industrial equipment.Some key parts easily form surface stress corrosion crack because of the tensile stress produced in the process of production and service.At the same time,internal thinning defects in the bending pipealso easily appear due to the fluid corrosion.These defects will seriously threaten the safety and reliability of industrial equipment structures.A composite electromagnetic nondestructive testing method based on pulsed eddy current and electromagnetic ultrasonic is proposed and developed to detect the surface cracks and bottom thinning defects of ferromagnetic specimens in this study.Meanwhile,a signal separation method based on spectrum filtering is developed to extract the pulsed eddy current signal and electromagnetic ultrasonic signal in composite detection.The experimental results show that the pulsed eddy current signal can effectively detect the surface cracks and the electromagnetic ultrasonic signal can well quantify the residual thickness of the bottom thinning defects.Therefore,the novel method developed in this study is of obvious advantages because it can detect both surface defects and bottom defects at the same time.