Abstract The objective of this work is to quantify the effect of loading rate on scatter as well as temperature-dependence of cleavage fracture toughness data of SA516 Gr.70 steel in the ductile-to-brittle transition temperature (DBTT) regime. This steel is a relatively high strength grade carbon steel and it is used for fabrication of nuclear pressure vessels, transportation casks and pipings etc. For integrity analysis in radioactive environment, the concept of master curve according to ASTM E1921 is used and the reference temperature T0 is evaluated from experimental data. The purpose of this work is to evaluate the change in T0 due to increase in loading rate when fracture specimens are tested in a modified split Hopkinson pressure bar (SHPB) test setup. In this work, a specially designed SHPB type test setup has been used to carry out the fracture tests using sub-sized single-edged notched bend specimens at a loading rate 700 m/min. The data from SHPB tests have been compared with those obtained from a lower loading rate of 0.5 m/min. From the results of the tests, it was observed that the median value as well as the scatter in fracture toughness increases with temperature in the DBTT regime for both the loading rates. For higher loading rate, the median values of fracture toughness increases slowly with temperature. The value of T0 was found to increase from -100°C at 0.5 m/min to -10°C at 700 m/min loading rate, signifying a positive shift in reference temperature with increase in loading rate. The reason for the observations regarding the variation of experimental data with loading rate has been explained from the point of view of micro-mechanism of the fracture process.

中文翻译：

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DBTT体系下加载速率对SA516Gr.70核压力容器和管道用钢断裂韧性的影响及参考转变温度变化评价

摘要 这项工作的目的是量化加载速率对 SA516 Gr.70 钢在韧脆转变温度 (DBTT) 范围内的解理断裂韧性数据的散射和温度依赖性的影响。该钢是一种强度较高的碳素钢，用于制造核压力容器、运输容器和管道等。 放射性环境中的完整性分析，使用根据 ASTM E1921 的主曲线概念和参考温度 T0是根据实验数据评估的。这项工作的目的是评估在改进的分体式霍普金森压力棒 (SHPB) 测试装置中测试断裂试样时由于加载速率增加而导致的 T0 变化。在这项工作中，专门设计的 SHPB 型试验装置已被用于使用小尺寸单刃缺口弯曲试样以 700 m/min 的加载速率进行断裂试验。SHPB 测试的数据与从 0.5 m/min 的较低加载速率获得的数据进行了比较。从测试结果可以看出，对于两种加载速率，在 DBTT 方案中，断裂韧性的中值和离散度都随着温度的升高而增加。对于更高的加载速率，断裂韧性的中值随温度缓慢增加。发现 T0 的值从 0.5 m/min 的 -100°C 增加到 -10°C 的 700 m/min 加载速率，这表明参考温度随着加载速率的增加而发生正变化。