聚乙烯管韧性破坏寿命预测方法研究

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There are three typical failure modes of high density polyethylene （HDPE） pipe under hydrostatic pressure, which are ductile rupture caused by creep, slow crack growth and degradation. The duration time of HDPE pipe under hydrostatic pressure before ductile rupture failure is predicted based on a viseo -elastic model. It is found that hoop stress increases due to reduction in wall thickness of HDPE pipe, while yielding stress decreases owing to decrease of strain rate. When the hoop stress approaches the instant yielding stress, HDPE pipe quickly deforms and then structural failure will follow. The relationship between hydrostatic pressure and failure life of HDPE pipe are obtained.聚乙烯管在静液压作用下有3种失效模式：蠕变韧性破坏、慢速裂纹脆性破坏和材料劣化破坏。提出基于粘弹性应力分析模型的聚乙烯管材蠕变韧性破坏寿命预测方法。在内压作用下，聚乙烯管材的蠕变导致其壁厚不断减薄，环向应力逐渐增大。同时，基于粘弹性应力分析模型得到管材蠕变的应变率逐渐减小，由于聚乙烯的屈服应力具有明显的率相关性，屈服应力也随之逐渐减小。当增加后的环向应力值与管材瞬时屈服应力相等时，聚乙烯管材发生韧性失效，从而得到韧性失效寿命与内压载荷之间的关系。