钢管涡流检测系统设计及孔类缺陷辨识研究-测试计量技术及仪器专业论文.docxVIP

II Abstract In engineering practice, Eddy current testing (ECT) often be used for steel tube’s quality, and our country formulates a standard GB/T 7735-2004 about ECT for steel tube. In this paper, according to the standard GB/T 7735-2004, processing steel specimens with through-hole or internal and external blind hole. ECT experiments of the through-hole or internal and external blind hole of steel tube under different magnetization current are carried on. The experiments is to study on the variation of ECT signal of through-hole or internal and external blind hole under different magnetization current, and improve the defect evaluation system of the standard GB/T 7735-2004 for steel tube. Consistent machining diameter steel tube in the same material, the different depth of internal and external blind hole, for steel tube under the unsaturated and saturated magnetization of ECT found the internal and external blind hole can effectively be checked out. However, this test uses exteriorly-thru-type probe, can be seen from the effective penetration depth of the eddy current, the internal blind hole should not be checked out. The trial against the phenomenon, through theoretical analysis curve extrapolated steel permeability and magnetizing current, because of the proliferation of non-uniform at around permeability to the steel surface of the coil impedance of an impact, this makes the internal blind hole to check out .According to the experiment phenomenon, the curve of relationship between steel tube permeability and magnetizing current can be gotten through theoretical analysis. It is concluded that the reason for the internal blind hole can be checked out is the non-uniform permeability around the flaws diffusion to the surface of steel tube, the coil impedance is influenced, then it makes the internal blind hole to check out. Firstly, considering the needs of ECT experiments of steel tube, designing the ECT instrument. The instrument includes the ECT coil, excitati