The Study On Pulsed Eddy Current Testing Of Austenitic Stainless Steel

Effective on-line non-destructive testing of austenitic stainless steel pressure vessel defects is anurgent problem in the field of pressure equipment. Using pulsed signal as excitation, pulsed eddycurrent method can get more defect information in time domain and realize a mass-area fast testing.Based on a research of the state of the art of domestic and foreign pulsed eddy current nondestructivetesting technology, the technical advantages of pulsed eddy current testing for austenitic stainless steelis refined. Pulsed eddy current technology is introduced into inspection of austenitic stainless steelpressure vessel, research and innovation as follows:This article described the principle of pulsed eddy current technology, established a simulationmodel to detect austenitic stainless steel using pulsed eddy current, simulated and analyzedaustenitic stainless steel pulsed eddy current response characteristics, and analyzed the effect of probestructure size on response signal. In order to enhance pulsed response signal in austenitic stainlesssteel, a system based on constant-current excitation source is designed for the analysis ofelectromagnetic property of austenitic stainless steel and for inspection of surface defects. Bycollecting the current value of pulse constant-current excitation at different time periods, itsstable-driving ability is verified as well as its anti-jamming ability, the predetermined targetcompleted.At last, long-thin slit injury defects with same width and different depth, and with same depthand different width are produced to simulate cracks. Also dot injury with same radius and differentdepth are produced to simulate pitting defects.6-layer wavelet decomposition using db4wavelet isapplied to filter the pulsed eddy current differential signal, achieving a good filtering effect and readyfor the extraction of time-domain feature value. The peak value of the above-mentioned defects isextracted and normalized to analyze the response characteristic of the austenitic stainless steel moreintuitively and for inspection and evaluation.