Method for assessing structural integrity of high-temperature and high-pressure welded member

Abstract

The invention relates to a method for assessing the structural integrity of a high-temperature and high-pressure welded member. The method comprises the following steps that (a) mechanical performance testing is conducted on a joint material of the welded member at normal temperature and high temperature; (b) crack propagation rate testing under the creep-fatigue and fatigue-creep interaction effect is conducted on the joint of the welded member in a high-temperature temperature to obtain crack propagation characteristics represented by high-temperature breakage parameters; (c) SEM is adopted to analyze the fracture of the joint of the welded member so as to determine a failure mode of a test sample and select corresponding high-temperature breakage parameters; (d) an isochronous stress-strain curve of the joint of the welded member is established; (e) the ratio value of a stress intensity factor to fracture toughness serves as a vertical coordinate and the ratio value of an applied load to a plastic collapse load serves as a horizontal ordinate to establish a failure assessment curve about the correlation between the joint material of the welded member and time, and an assessment area of the failure assessment curve is divided into a safety area and a failure area to perform structural safety assessment. Therefore, the obtained safety evaluation is more scientific and accurate.

Description

technical field [0001] The invention relates to a structural safety assessment method, in particular to a structural integrity assessment method of high temperature and high pressure welded components with creep, fatigue and creep-fatigue interaction. Background technique [0002] At high temperatures (generally above 500°C), creep and fatigue fracture of metal structures become the main failure modes. For example, about 30% of the pipes in boilers and pyrolysis reforming units, especially the failure of welded joints, are caused by creep or fatigue fracture. The key challenge of the creep and fatigue interaction problem is that the damage gradually accumulates inside the material, and the failure often occurs suddenly without obvious symptoms, causing serious losses to production and even catastrophic consequences. [0003] At present, my country has carried out research on local thinning defects in pressure vessels in the "Seventh Five-Year Plan" and "Eighth Five-Year Pla...

AI Technical Summary

Problems solved by technology

However, this standard is only for equipment at room temperature, and the evaluation of defects under high temperature creep conditions does not involve

However, the failure assessment under the creep-fatigue interaction in foreign standards only adopts the linear superposition method, which obviously has a large error

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