| To axial throughwall crack pipeline, sleeve repair in crack region can hinder or suspend the extension of the crack and therefore is extensively adopted. So it's of significant importance to carry on quantitative research on the lengthening of this structure to the life of defect component. Limit analysis can reflect the nature of the structure and becomes more and more important in safety assessing of defect pipeline and intensify designing of structure. With fracture mechanics theory, using finite element methods, studied crack arrest law of sleeve repair to axial throughwall crack pipeline; with mechanics of elastoplasticity, using three dimensional elastoplasticity finite element methods, calculated plasticity limit load of the structure.Main content and conclusions are as follows:(1) Studied finite element modeling methods of axial throughwall crack pipeline structure and confirmed its accuracy. Established finite element model of axial throughwall crack pipeline repaired by sleeve, compiled model production, load and post-processing macroprogram with APDL.(2) Evaluated the crack arrest effect according to the crack arrest coefficient f which is the ratio of stress intensity factor after sleeve repair K to original one K0; evaluate limit load level according to limit load coefficient p which is the ratio of limit load of crack pipeline PLd to non-crack ones with same specification PL0 Calculated and analyzed prestressed and non-prestressed sleeve structure from crack arrest effect and limit load level aspects.(3) To non-prestressed sleeve, crack arrest coefficient f and limit load coefficient p are related with location of sleeve Lx, length of sleeve Ls, and wall thickness ts:f decreases and then increases after the increase of Lx and decreases along the increase of Ls and ts; while p changes oppositely and can reach the maximum. Provided reasonable sleeve arrangement suggestion, that is, recommendation parameter; given equal wall thickness entire crack sleeve, the crack arrest coefficient f is related with t/Do andα/Do, proposed the fitting formula of f; under the given recommendation parameter, p is close to 1 and with no relationship with crack pipeline parameter, and the repaired crack pipeline can reach the limit load level as complete one.(4) To prestressed sleeve, prestressed produced through interference fit between sleeve and crack pipeline. Crack arrest coefficient f and limit load coefficient p are related with length of sleeve Ls, and wall sickness ts; and shrink rangeδ, but not with location of sleeve Lx; f decreases with the increase of Ls, ts,δ, and increases after reaching the minimum, while p increases with the increase of Ls, ts,δ, and keep stable after the maximum. Recommended sleeve structure under given prestressed pattern which is the same as non-prestressed sleeve.δdiffers with minimum f from different axial throughwall crack pipeline, limit load can reach the limit load level as complete pipeline and influenced byδslightly.(5) Compare conclusions under the two situations, prestressed sleeve is better than non-prestressed sleeve, and recommend equal wall thickness entire crack sleevewith small magnitude of interference which is convenient in engineering application.
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