Research On Automatic Non-destructive Testing System Of Steel Bars

Automatic inspection system for defects of steel bars has very important meaning in the aspects such as improving the quality of products and reducing accidents. Combined with automatic inspection of steel bars, this dissertation deeply researches some key problems existing in MFL(Magnetic Flux Leakage) method of steel bars' transverse defect testing and signal wireless transmission in rotational testing probes.On the ground of analysis of recent correlative research status at home and abroad about the inspection methods and inspection systems of steel bars, according to the practical condition of the bars' defects and the requirements of inspection, MFL method is adopted, which has such many advantages as rapid speed, high sensitivity and so on. In addition, the general design and arrangement of the whole system are set down. In this dissertation, on the basis of experimental results, some key problems existing in MFL method of steel bars' transverse defect testing are discussed, such as the optimum magnetization regions on different specification bars, the limit sensitivity and the end effect. The wavelet analysis, which has property of multi-resolution, is used to filter and extract defect signals from steel bars' end part testing signals effectively. In order to transform testing signals from rotational probes, firstly, electromagnetism coupling is applied to supply the power wirelessly and magnetic circuit is designed reasonably to improve the efficiency of the power transmission. Secondly, infrared wireless transmission method is used in signal transmission system by voltage-frequency conversion (V/F) and frequency-voltage conversion (F/V), to enhance the dependability of signal transmission.Based on the experimental studies, steel bars' MFL testing system is developed and mechanical structure and electrical control of the whole testing system are ameliorated. Through on-site testing, it proves that the system is effective and reliable.