Experimental Research On Magnetostrictive Guided Wave Testing Technique

Recently the research of magnetostrictive guided wave technology has been carried out widely and thoroughly because the technology can inspect over long distance from a single position. Based on the demands and supports of special funds from support from the National High Technology Research and Development Program of China (863 Program) (No. 2006AA04Z435), National Key Technology R&D Program of China (No. 2006BAK02B03-S-01), this thesis studied the guided wave propagation and flaw detection on different types of wave guide and several elements that affect the propagation of the guided wave experimentally.First of all, the magnetostrictive guided wave inspection system is developed based on the basic principle of magnetostriction. Two important factors during the propagation of guided wave, dispersion of guided wave and magnetostrictive linear region, are studied too.Secondly, the relationship between magnetization of the pipes and the amplitude of the signal is studied in detail by designing different structure of magnetic circuit. A linear relation between them was found which provided reference for further inspections. The propagation of guided wave in coated pipelines is studied when considering the coating as a lift-off effect of the sensors based on the result. The relationship curve between the attenuation of the signal and the lift-off height is obtained. The result shows that a thick coating causes a great attenuation during propagation, which in return a greater exciting power is required.At last, studies on common cables are carried out experimentally. The study on single wire, parallel wire and prestressing steel strand, showed a linear relationship between the area loss and the defect signal amplitude, which provided reference for quantitative inspection. The signal processing method of reference point and difference is applied to process reflected signals of the defect when using the transition zone of sucker rod to simulated the complex structure of the cable anchorage zone. Experiment of cable anchorage zone is conducted, which provided a basis for in-service detection of the cable anchorage zone.