The Researching Of Alternating Current Field Measurement Imaging Technology

The Alternating Current Field Measurement (ACFM) technique is a electromagnetic non-destructive testing (NDT) technique used to detect and size surface cracks in electrically conducting, metallic components. In this paper, The ACFM scan imaging measurement technique is accomplished. The status and the development home and abroad of the ACFM technique and the scan imaging technique are illustrated. Considering the motion of exciting coil in different scan orientation, the finite element numerical simulation analysis of the distribution of the perturbed magnetic is accomplished. The simulation results show that the length of crack is estimated by amplitude peculiarity of Bz, the component of magnetic field perpendicular to metal surface. the relation between the depth of crack and Bx. The ACFM scan imaging measurement system is designed from electrocircuit hardware and soft. The system scheme for testing are presented. Meanwhile, in order to improve the result the wavelet transform is used to remove the noise. This paper discusses the crack identification by qualitative analysis and the length and width of the crack from the measured signal is analysed. At last scan imaging technique is accomplished and the C scan image is finished from the amplitude of Bx and Bz and by the new way of two image combination, the length and width are shown directly. Based on the system, testing has been performed by experimentation on the sample, the result of C scan image is finished.And the experiment data, the theoretic data and the simulation data have the same trend approximately .