金属材料.钢构件断裂评估CTOD断裂韧性损失校正约束方法

[中文适用范围]： 在含裂纹钢结构的断裂评估中，通常假设断裂韧性试样的断裂抗力等于结构构件的断裂抗力。 然而，这样的假设常常导致骨折评估过于保守。 这是由于主要承受拉伸载荷的结构部件失去了塑性约束。 相比之下，断裂韧性样品由于弯曲模式而在裂纹尖端附近保持约束应力状态。 对于近年来得到广泛开发并广泛应用于结构的具有高屈强比（=屈服应力/抗拉强度）的高强度钢来说，约束的损失是显着的。 本国际标准规定了一种将实验室样品获得的 CTOD（裂纹尖端张开位移）断裂韧性转换为结构部件的等效 CTOD 的方法，同时考虑约束损失。 该方法也适用于使用应力强度因子或 J 积分概念的断裂评估（参见第 9 条）。 本国际标准涉及铁素体结构钢中因裂纹状缺陷或疲劳裂纹而发生的不稳定断裂。 伴随大量延性裂纹扩展的不稳定断裂和延性断裂不包括在本发明的范围内。 结构钢的 CTOD 断裂韧性根据既定测试方法 ISO 121351) 或 BS 7448-1 进行测量。 裂纹部件的断裂评估是使用有关组织中既定的方法如FAD（失效评估图）进行的，本国际标准中未提及其细节。 本国际标准可消除传统断裂力学方法中经常出现的过度保守现象，从结构钢的断裂韧性中准确评估结构件的不稳定断裂起裂极限。 这也用于合理确定材料的断裂韧性，以满足结构件性能的设计要求。 [外文原描述]： In fracture assessments of steel structures containing cracks, it has generally been assumed that the fracture resistance of fracture toughness specimens is equal to the fracture resistance of structural components. However, such an assumption often leads to excessively conservative fracture assessments. This is due to a loss of plastic constraint in structural components, which are subjected mainly to tensile loading. By contrast, fracture toughness specimens hold a constrained stress state near the crack-tip due to bending mode. The loss of constraint is significant for high strength steels with high yield-to-tensile ratios (= yield stress/tensile strength) which have been extensively developed and widely applied to structures in recent years. ISO 27306:2016 specifies a method for converting the CTOD (crack-tip opening displacement) fracture toughness obtained from laboratory specimens to an equivalent CTOD for structural components, taking constraint loss into account. This method can also apply to fracture assessment using the stress intensity factor or the J-integral concept (see Clause 9). ISO 27306:2016 deals with the unstable fracture that occurs from a crack-like defect or fatigue crack in ferritic structural steels. Unstable fracture accompanied by a significant amount of ductile crack extension and ductile fractures are not included in the scope hereof. The CTOD fracture toughness of structural steels is measured in accordance with the established test methods, ISO 12135[1] or BS 7448-1. The fracture assessment of a cracked component is done using an established method such as FAD (Failure Assessment Diagram) in the organization concerned, and reference is not made to the details thereof in ISO 27306:2016. It can be used for eliminating the excessive conservatism frequently associated with the conventional fracture mechanics methods and accurately assessing the unstable fracture initiation limit of structural components from the fracture toughness of the structural steel. This is also used for rationally determining the fracture toughness of materials to meet the design requirements of performance of structural components.