CTOD与BS7910结合的桥梁钢断裂韧度评定方法

The Fracture Toughness Assessment Method of Bridge Steel with CTOD and BS 7910

针对应用裂纹尖端张开位移(CTOD)评判指标评定桥梁钢和焊接接头的断裂韧性时缺少依据的问题,提出将CTOD试样的单边疲劳预裂纹作为缺陷,运用BS7910《金属结构缺陷可接受性评定方法指南》的失效评定曲线对桥梁钢的CTOD值进行评定。具体方法是根据对应桥梁钢CTOD试验温度下的单轴拉伸应力—应变曲线,得到桥梁钢真应力—真应变曲线,然后按照BS7910的2B级评定方法得到桥梁钢的CTOD的失效评定曲线,最后根据桥梁钢的CTOD值在失效评定曲线图上所处的位置对其合格性进行评定。应用该方法对某大跨度斜拉桥用50,60和100mm厚的S420ML桥梁钢进行评定,结果表明,这3种厚度的S420ML桥梁钢的CTOD值均在失效评定曲线图中可接受区域内,它们的断裂韧度均为合格。

It is difficult to determine the acceptable value of CTOD （crack tip opening displacement） when use CTOD as a term to assess the fracture toughness of bridge steel and the welded joints. Taking single edge fatigue precrack of CTOD specimen as a flaw, the FAD （failure assessment diagrams） of BS 7910 can be used to assess the acceptable value of CTOD of bridge steel. The uniaxial tensile test were conducted at the same temperature of CTOD test, then the true stress-true strain curve and the FAD of bridge steel could be obtained according to the level 2B of BS 7910. Using the FAD, the acceptable value of CTOD can be assessed. CTOD of 50 mm, 60 mm and 100 mm thickness parent material of S420ML bridge steel were assessed with this method for a certain long-span cable-stayed bridge. It gives the conclusion that all CTOD of the tested specimens are located in the acceptable area of the FAD and their fracture toughness is eligible.