内压作用下复合材料修复裂纹管道的失效分析

Failure analysis of cracked pipes repaired by composites under internal pressure

为准确评估在内压作用下纤维复合材料修复含裂纹管道的有效性及失效压力,建立复合材料修复后裂纹管道的失效数值模型。该数值模型通过扩展有限元法模拟管道裂纹的扩展,利用cohesive单元模拟胶层的脱粘失效,复合材料的失效通过最大应力失效准则进行判定。通过静水压爆裂试验对所提失效数值模型进行验证,实验结果与数值计算结果具有较好的一致性。失效数值分析结果表明:当内压增大至一定值后,未修复管道的初始裂纹沿轴向及壁厚方向逐渐扩展,进而使得管道内壁单元扩展成真实裂纹,此时真实裂纹贯穿整个壁厚方向,即认为裂纹管道发生爆裂失效,爆裂失效压力随初始裂纹半长呈指数形式下降。复合材料修复裂纹管道的不同修复工况呈现相同的失效模式:在单调递增的内压作用下,管道内表面首先出现黏结裂纹,而后其外表面裂纹张开趋势急剧上升,使得复合材料层应力急剧上升,达到极限强度而失效。且对于不同的初始裂纹尺寸,存在对应的复合材料缠绕层数临界值。

In order to accurately evaluate the effectiveness and failure pressure of cracked pipelines repaired by fiber composites under static load,a numerical model for the failure of cracked pipelines repaired by composites was established.The numerical model simulated the crack propagation of the pipeline by expanding finite element method.The cohesive element was used to simulate the debonding failure of the adhesive layer.The failure of the composite material was determined by the maximum stress failure criterion.The proposed numerical model of failure was verified by hydrostatic burst test.The experimental results were in good agreement with the numerical results.According to the results of numerical analysis,when the internal pressure increases to a certain value,the initial crack of the unrepaired pipe gradually expands along the axial and wall thickness directions,and then the inner wall unit of the pipe expands into a real crack.At the same time,the real crack runs through the entire wall thickness.The burst failure pressure decreases exponentially with the half length of the initial crack.The different repair conditions of cracked pipelines repaired by composite exhibit the same failure mode:under the monotonically increasing internal pressure of the pipeline,the internal surface of the pipeline first appears a cohesive crack,and the cracking tendency of its outer surface rises sharply,making the stress of the composite material layer rise sharply and reach the ultimate strength.And there are corresponding critical values of the composite layers for different initial crack sizes.