The Simulation Analysis Research Of Low Frequency Eddy Current Test On Water Tubes' Corrosion

The water wall tube is the main structure inside the utility boiler, so its online detection of corrosion defects has an important economic value. The low-frequency eddy current testing technology has more sensitivity on detecting the defects inside pipeline wall, so it has a very good prospect. To learn more about it how to apply the water wall effectively, the paper adopts the finite element analysis software ANSYS to carry out low-frequency eddy current testing simulation , which conclusion will provide the theoretical basis for the actual design and testing of the probe.Firstly, the article briefly introduces the principles of low-frequency eddy current testing according to the principle of electromagnetic induction, and finds out the formulas about how eddy current and electromagnetic field spread along the pipeline result from Maxwell's equations in low-frequency eddy current testing. It reaches conclusion that detection of the inner surface defects which is obtained with different specimens needs to select the appropriate frequency, and proposes the method of according to the size of phase to judge whether defect exists or not.Secondly, it makes a reasonable assumptions and definition of issues for an one-channel device of low frequency eddy current electromagnetic field, and gets the three-dimensional simulation optimized model. After solving the model, receives the vector distribution of eddy current and magnetic field when there has or not has defect, and compares the two curves of the induced voltage. Then analyze the suit factors for water-wall tube by analyzing the frequency and signal amplitude of excitation and the pattern of detection coil place respectively,and studies the regular pattern of phase difference under different patterns of defects,which illustrates the correctness of the methods of determining whether defect exists or not based on the size of phase difference.Finally,increases the sweep area of the probe by increasing the numbers of the detection coil,records the location coordinates and the induced voltage value when it moves facilitate,the graphics of the phases can effectively determine the approximate location of defects.Through those researches, provides an effective program by designing multi-channel low-frequency eddy current testing device for the water-wall corrosion, to a certain extent, improves the work efficiency.