A method for evaluating residual stress distribution characteristics of natural gas pipeline girth welds using coercive force

Abstract

The invention discloses a method for evaluating residual stress distribution characteristics of a natural gas pipeline girth weld by using coercive force. The method utilizes the probe of the coercive force detection device and the outer wall of the natural gas pipeline to form a closed magnetic circuit, and an alternating current is passed into the probe to magnetize the closed magnetic circuit to measure the hysteresis loop, and the same material as the natural gas pipeline is used to make a standard tensile The test piece is subjected to stress test to determine the corresponding relationship between coercive force and stress, and then use the coercive force detection device to measure the residual stress of the outer wall of the natural gas pipeline, draw the residual stress change curve, and establish a finite element model according to the actual natural gas pipeline. The spherical heat source model simulates the distribution of residual stress at the girth weld of the natural gas pipeline, determines the residual stress distribution cloud map at the girth weld, draws the residual stress characteristic curve and verifies its accuracy. The invention realizes the nondestructive detection and evaluation of the residual stress of the natural gas pipeline, has simple operation, and is beneficial to guarantee the service safety of the welded pipeline.

Description

technical field [0001] The invention relates to the field of natural gas pipeline construction, in particular to a method for evaluating residual stress distribution characteristics of a natural gas pipeline girth weld by using coercive force. Background technique [0002] Pipeline girth weld welding technology, as a key technology for on-site construction of natural gas pipelines, will inevitably generate welding residual stress during the welding process. The existence of residual stress is the cause of failure modes such as brittle fracture, fatigue fracture and stress corrosion cracking of pipeline welded joints. Therefore, it is of great significance to study the distribution characteristics of residual stress for the long-term effectiveness and safety of in-service pipelines. [0003] At present, the blind hole method and ultrasonic method are mostly used for the measurement of residual stress in the pipeline. However, because the blind hole method belongs to the destr...

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Problems solved by technology

[0003] At present, the blind hole method and the ultrasonic method are mostly used for the measurement of the residual stress of the pipeline on site. However, since the blind hole method is a destructive detection method, the pipeline needs to be artificially drilled during the measurement, causing damage to the pipeline; the measurement conditions of the ultrasonic method are demanding and difficult. It is easy to be affected by factors such as material anisotropy, processing technology, heat-affected zone, etc. Therefore, it is urgent to propose a new and efficient online evaluation method for residual stress in pipelines, which can not only ensure the service safety of welded pipelines, but also ensure the safety of pipelines. residual stress evaluation

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