Accurate quantitative method for inclined cracks of thick-wall pipelines based on time of fight diffraction (TOFD) circumferential scanning images
A technology of circumferential scanning and cracking, which is applied to measuring devices, processing detection response signals, and using sound waves/ultrasonic waves/infrasonic waves to analyze solids, etc., can solve the problem of increased detection errors, non-overlapped propagation paths, and inability to crack length and inclination Accurate and quantitative angles and other issues, to achieve the effect of improving detection efficiency, simple operation, and high engineering application value
Active Publication Date: 2018-12-21
DALIAN UNIV OF TECH +2
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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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[0033] An accurate quantification method for oblique cracks in thick-walled pipes based on TOFD circumferential scanning images, using an ultrasonic testing system such as figure 1 As shown, it includes a TOFD flaw detector, a pair of TOFD ultrasonic probes, a pair of longitudinal wave wedges, and scanning devices. The specific detection and processing steps are as follows:
[0034] (1) Test objects such as figure 2 As shown, the outer wall radius of the thick-walled carbon steel pipe is 148.0mm, the wall thickness is 26.5mm, the axial length of the test block is 300.0mm, and the sound velocity of the longitudinal wave of the material is 5890m / s. In the test block, an inclined crack with an upper end point depth of 8.4mm, a lower end point depth of 11.9mm, a length of 4.0mm, and an inclination angle of 30° was processed.
[0035] (2) if image 3 As shown, the TOFD probe with a center frequency of 5MHz is used for detection, the longitudinal wave wedge angle is 45°, the cen...
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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...
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IPC IPC(8): G01N29/06G01N29/44
CPCG01N29/069G01N29/44
Inventor 金士杰马天天张东辉林莉严宇廖静瑜
Owner DALIAN UNIV OF TECH