Large-caliber thick-wall pipeline defect location method based on time-reversal circumferential Lamb waves

Abstract

The invention relates to a large-caliber thick-wall pipeline defect location method based on time-reversal circumferential Lamb waves. According to the method, a defect in a pipeline is regarded as a wave source, and scattered signals generated by interaction of the circumferential Lamb waves and the defect are regarded to be sent by the wave source. The scattered signals are secondarily excited by a multi-channel sensor after the scattered signals are accepted, intercepted and inverted by the multi-channel sensor, thereby achieving detection of small defects in a large-caliber thick-wall pipeline. Bu utilization of the time-reversal focusing principle, the signals surely focus on the position of the wave source (namely the defect), and therefore defect echo signals with high amplitudes are generated, and existence of the defect can be determined based on the defect echo signals. Meanwhile, according to compensation characteristics of time reversal to circumferential Lamb wave frequency dispersion and multimoding effects, the direct signals will focus partly, and defect circumferential location of the large-caliber thick-wall pipeline is achieved by using the time for direct signal focusing as the time reference. The process can be achieved by two manners as follows: detection by utilization of a sensor array and a multichannel signal excitation reception system; and detection by utilization of a pair of sensors and a single-channel signal excitation reception system. The method solves problems, namely difficulty in finding the time reference, difficulty in locating defects, and the like, in time-reversal ultrasonic detection.

Description

technical field [0001] The invention relates to a defect detection and positioning method of a large-diameter thick-walled pipeline, and belongs to the field of ultrasonic non-destructive testing. In particular, it relates to a defect location method for large-diameter thick-walled pipelines based on time-reversed circumferential Lamb waves. Background technique [0002] Thick-walled pipe refers to a tubular steel structure with a ratio of outer diameter to wall thickness of less than 20. Large-diameter thick-walled pipes are widely used in the fields of petroleum, chemical industry, and thermal power generation. Since the pipes work in high-temperature and high-pressure environments and the inner and outer walls of the pipes are easily exposed to corrosive media, various types of failures are prone to occur during use, resulting in leakage accidents, resulting in Serious environmental pollution accidents and major economic losses. Therefore, it is very important to find a...

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Problems solved by technology

At present, there is no public research report on the time-reversed circumferential Lamb wave, and the research on the time-reversed longitudinal guided wave is mostly focused on the imp

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