POP-IN效应对材料断裂韧度的影响及评价

INFLUENCE AND ASSESSMENT OF THE POP-IN EFFECT ON MATERIAL FRACTURE TOUGHNESS

裂纹尖端张开位移δ是衡量材料断裂韧度的一个重要参量,但在进行CTOD(cracktipopeningdisplacement)试验时,F—V曲线上通常会出现瞬间的载荷迅速下降、位移增加很小的“突进”现象,俗称“POP- IN”,它的出现对确定CTOD值产生很大影响,进而影响到材料断裂韧度评价的准确性。针对这一问题,文中依据BS7448PartⅡ中的有关评定标准,结合EH36钢埋弧焊接头CTOD试验,分别对均质、非均质材料中存在POP- IN现象时如何正确评定进行论述,力图为合理取舍POP -IN效应、准确评价材料断裂韧度提供依据。

The crack tip opening displacement（CTOD）,δ, is an important parameter which has been widely used in the asessment of material fracture toughness. However, the value of δ is influenced largely by a kind of phenomenon ＂POP-IN＂, which appears in CTOD test procedure with the load falling down rapidly and displacement increasing very slowly in the F-V curve. For this problem, an elaborate discuss on how to assess the POP-IN effect properly and reasonably when it occurs in homogenous and heterogeneous materials respectively has been given according to correlative assessing standard in BS 7448 Part Ⅱ . Furthermore, The CTOD test of EH36 submerged-arc welded （SAW） joint was exampled to provide a basic route and theoretical foundation for accepting or rejecting POP-IN effect properly, and assessing structural fracture toughness accurately.