| At present,oil and gas are mainly transported by steel pipelines,and with the expanding energy demand,high steel grade large diameter pipelines are widely used in oil and gas transmission pipelines.It is inevitable that ring welds will exist in the pipeline laying process,and the ring weld area usually has various welding defects,which will have serious impact on the safety of the pipeline.Steel epoxy sleeve repair technology,as a non-welding repair technology,has gradually started to be used for pipeline defect repair,but there are few research results related to the repair of ring weld defects in high steel grade large diameter oil and gas pipelines with steel epoxy sleeve.Therefore,in this paper,the ultimate bearing capacity of steel epoxy sleeve repairing large-diameter pipeline with ring weld cracks of high steel grade under internal pressure,bending moment and combined load of internal pressure and bending moment is studied,and the main research results obtained are as follows:In this paper,the finite element model of X80 pipe containing ring weld cracks is firstly established by using the extended finite element method,which can simulate the expansion characteristics of cracked ring weld pipe and obtain the stress-strain distribution law of the crack tip.On this basis,the numerical simulation results are compared and analyzed with the internal pressure burst test and four-point bending test to obtain the crack expansion law of X80 pipe with ring weld crack.Secondly,the thesis systematically analyzes the influencing factors of the ultimate bearing capacity of the pipe containing ring weld cracks,and establishes the influence law of the crack length,crack depth,pipe wall thickness,pipe diameter and other parameters on the ultimate bearing capacity of X80 pipe based on the action of internal pressure,bending moment and combined load.At the same time,the formula for calculating the ultimate bearing capacity of X80 pipe under the action of internal pressure and bending moment was established.Finally,this paper establishes a numerical model of steel epoxy sleeve repairing cracked pipe with ring weld,analyzes the reinforcement mechanism of steel epoxy sleeve repairing cracked pipe with ring weld,obtains the ultimate bearing capacity of repaired and unrepaired cracked pipe with ring weld,and then gives the evaluation index of reinforcement effect.At the same time,the influence of crack length,crack depth,pipe wall thickness and pipe diameter on the repair performance of the steel epoxy sleeve and the ultimate bearing capacity of the repaired pipe was established.The results of this paper can provide a reference for predicting the ultimate load capacity of steel epoxy sleeves for repairing pipes containing ring weld cracks and for the future engineering applications of steel epoxy sleeve repair technology. |
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