Abstract It is vital to prevent brittle cracks in large structures. This is particularly important for a number of industry sectors including offshore wind, Oil & Gas, and shipbuilding where structural failure risks loss of human life and loss of expensive assets. Some modern steels exhibit high Charpy energy – i.e. high initiation fracture toughness, but poor resistance to crack propagation – i.e. low crack arrest toughness. The correlation between initiation and arrest toughness measured through small-scale testing is investigated in five different steels, which include S355 structural steel (with two different thicknesses), X65 pipeline steel, two high strength reactor pressure vessel steels and EH47 shipbuilding steel. Small scale mechanical tests were carried out to characterise the materials’ properties and were compared to the materials’ microstructures. A wide range of tests were carried out, including instrumented Charpy, drop weight Pellini, fracture toughness, tensile testing, and optical microscopy. Nil ductility transition temperature (NDTT) is used to characterise a material’s arrest properties. Initiation fracture toughness correlated with higher upper shelf Charpy energy and smaller average grain sizes, as expected, however none of these correlated well with the arrest toughness measured through NDTT. The NDTT correlated most strongly with the T27J temperature which indicates the start of lower shelf of the Charpy curve. This correlation held for all materials including those where the NDTT lies on the upper shelf of the Charpy curve. While initiation fracture toughness can be predicted through high Charpy toughness and operation temperatures on the upper shelf, crack arrest behaviour should be predicted from characteristics of the ductile to brittle transition temperature, for example by using the T4kN from instrumented Charpy tests or T27J.

中文翻译：

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小规模试验预测的断裂起始韧度与脆性裂纹止裂韧度关系的实验研究

摘要 防止大型结构的脆性裂纹至关重要。这对于许多行业尤其重要，包括海上风能、石油和天然气以及造船业，在这些行业中，结构故障可能会导致人员伤亡和昂贵资产的损失。一些现代钢表现出高夏比能——即高起始断裂韧性，但抗裂纹扩展能力差——即低裂纹止裂韧性。研究了通过小规模试验测量的起止韧性之间的相关性，包括 S355 结构钢（两种不同厚度）、X65 管线钢、两种高强度反应堆压力容器钢和 EH47 造船钢等五种不同钢种。进行了小规模的机械测试以表征材料的性能，并与材料的微观结构进行比较。进行了广泛的测试，包括仪器化夏比、落锤 Pellini、断裂韧性、拉伸测试和光学显微镜。无延展性转变温度 (NDTT) 用于表征材料的阻滞特性。正如预期的那样，初始断裂韧性与较高的上架夏比能和较小的平均晶粒尺寸相关，但是这些都与通过 NDTT 测量的止裂韧性没有很好的相关性。NDTT 与 T27J 温度的相关性最强，T27J 温度表明夏比曲线下架的开始。这种相关性适用于所有材料，包括那些 NDTT 位于夏比曲线上架的材料。