PE100管及其热熔接头的蠕变裂纹扩展行为

聚乙烯(PE)管性能优异,广泛应用于城市水及燃气供应系统。PE管的主要破坏形式是长期静压载荷下的慢速裂纹扩展失效。在蠕变条件下,采用光滑试样和裂纹圆棒试样对PE100管及其热熔接头进行了测试,得到了基于蠕变断裂参数C*的蠕变裂纹扩展动力学关系式。利用扫描电子显微镜(SEM)分析了裂纹圆棒试样的断面形貌,对比分析结果发现,蠕变裂纹扩展失效模式对应的最大应力为15.05 MPa,热熔接头熔合面分布有约11个/mm^2、直径范围为1~5μm的微气孔,热熔接头断裂微纤平均长度比母材约小20%~45%。当热熔对接时,熔合面存在的微气孔以及系带分子的浅渗透是导致PE100热熔接头蠕变裂纹扩展抗力降低的主要原因。

Creep Crack Growth ( CCG) Behavior of PE100 Pipe and Its Butt-Fusion Joint

Polyethylene(PE)pipe was widely applicated in city water and gas supply systems for its excellent properties.Most PE pipes were damaged by slow crack growth under long-term static pressure.Under the creep condition,PE100 pipe and its butt-fusion joint were tested by smooth specimens and cracked round bar specimens.The creep crack growth kinetics based on the creep fracture parameter C*was obtained.The fracture surfaces morphology of cracked round bar specimens were analyzed by scanning electron microscopy(SEM).By contrast,the maximum stress corresponding to failure mode of creep crack propagation was 15.05 MPa.There were micro pores with a density about 11/mm2 and diameters ranging from 1 to 5μm on the fusion surface of the butt-fusion joint.The average length of rupturing fibrils was 20%~45%shorter than that of parent material.The two main reasons that led to the decrease of the creep crack growth resistance of the PE100 butt-fusion joint were the existent micro pores on the fusion surface and the shallow penetration of the tie-molecules during butt-fusion process.