Precise quantitative method for inclined cracks in thick-walled pipes based on tofd circumferential scan images

Abstract

The invention discloses an accurate quantitative method for inclined cracks of thick-wall pipelines based on time of fight diffraction (TOFD) circumferential scanning images, and belongs to the technical field of nondestructive testing. The accurate quantitative method adopts a TOFD detection system consisting of a TOFD flaw detector, TOFD probes, inclined plexiglass wedges and a scanning device,and TOFD circumferential scanning and image acquisition are carried out along the outer walls of the thick-wall pipelines. The radial distance from the upper and lower end points of the cracks to theouter walls of the pipelines, namely, the end depth, is calculated when primary bottom surface waves and diffracted waves propagating sound at the upper and lower end points of the cracks in the scanned images are read. The crack length and inclination angle are calculated based on the geometric relationship among the TOFD probe center spacing, the pipeline wall thickness and the pipeline outer wall curvature radius. The accurate quantitative method can realize simultaneous measurement of crack depth, length and inclination angle in the thick-wall pipelines, and has high detection efficiency,simple operation and high engineering application value.

Description

technical field [0001] The invention relates to a method for accurately quantifying oblique cracks in thick-walled pipelines based on TOFD circumferential scanning images, which belongs to the technical field of nondestructive testing. Background technique [0002] Thick-walled pipes are widely used in nuclear power, petroleum, chemical and electric power industries, and are often exposed to harsh service environments such as high temperature, high pressure, high radiation or strong corrosion for a long time, and are prone to dangerous defects such as cracks. Accurately giving crack location, scale and orientation information is of great significance for pipeline excavation repair, life prediction and safety assessment. [0003] At present, the non-destructive testing methods for internal defects of pipelines mainly include radiographic testing and ultrasonic testing. Among them, ray detection is not sensitive to area defects such as cracks, and it is difficult to give defe...

AI Technical Summary

Problems solved by technology

The efficiency of conventional ultrasonic testing is low, and the echo signal is significantly affected by the orientation of the crack; guided wave technology can detect cracks in thick-walled pipes, but cannot accurately quantify the crack length and inclination angle

When the conventional TOFD is used to detect the inclined cracks of the pipeline along the circumferential direction, the surface of the pipeline with curvature does not coincide with the propagation path of the straight-through wave, which leads to deviations in the results of crack location, fixed length and orientation; when the wall thickness of the pipeline is large, it is necessary to Increase the probe center distance to realize crack detection in deep areas, and the detection error caused by the curvature of the pipeline will further increase

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