Variable pulse width stimulated pulse eddy current detection method

Abstract

The invention discloses a variable pulse width stimulated pulse eddy current detection method. The method comprises the following steps: (1) putting a pulse eddy current sensor on a test piece to be detected; (2) setting a current stimulation pulse width PWcur=t0; (3) obtaining a detection signal and measuring a time interval [0,t]; (4) calculating integral INcur of the detection signal in a time interval [t1,t2]; (5) setting a next stimulation pulse width PWnext=PWcur+PWadd; (6) obtaining a detection signal and measuring a time interval [0,t]; (7) calculating integral INnext of the detection signal in a time interval [t1,t2]; (8) calculating RIcur=(INnext-INcur) / INcurPwadd; comparing the RIcur with a pre-set threshold value RIT; if the RIcur is less than RTT, executing the step (9); otherwise, determining that PWcur=PWnext and INcur=INnext; returning back to the step (5); and (9) recording the current stimulation pulse width PWcur to obtain a detection region characteristic of the test piece to be detected according to a relation between the pulse width and the detection region characteristic. The method can be used for detecting each detection region characteristic of the test piece to be detected, is not easily influenced by noise and is simple and easy to operate.

Description

technical field [0001] The invention belongs to the technical field of electromagnetic nondestructive testing, and more specifically relates to a pulsed eddy current testing method with variable pulse width excitation. Background technique [0002] During the use of pressure vessels and pipelines, the wall thickness is often thinned due to corrosion and erosion, which seriously threatens the safety of industrial production. Since the pulsed eddy current testing technology adopts the excitation in the form of pulses, it is not necessary to remove the covering layer outside the pressure vessel and the pipeline during the testing, and it can detect deep-seated defects. It has the advantages of fast speed, good safety, and low cost. One of the preferred techniques for detecting pressure vessel and pipe wall thickness reduction. [0003] In the pulsed eddy current testing technology, the excitation in the form of a pulse is applied to the excitation coil close to the test piece....

AI Technical Summary

Problems solved by technology

The above method has the following disadvantages: (1) Use the amplitude of a certain point of the detection signal or differential signal to detect defects, which is easily affected by noise; (2) The excitation coil of the sensor is loaded with a pulse excitation of a preset frequency, and its pulse width Invariant, limited information obtained from detection signal

Images