金属材料. 用预制裂纹夏比试片在冲击载荷率下测量断裂韧性

[中文适用范围]： 本国际标准规定了使用断裂力学方法对金属材料进行和评估仪器化预裂夏比冲击试验的要求。 对测量和记录设备给出了最低要求，以实现相似的灵敏度和可比较的测量。 当满足相应的有效性标准时，使用本国际标准确定的动态断裂力学性能与传统的大尺寸断裂力学结果具有可比性。 由于夏比试样的绝对尺寸较小，因此情况通常并非如此。 尽管如此，获得的值可用于材料的研究和开发、质量控制，以及确定冲击载荷速率下性能随测试温度的变化。 通过使用本国际标准确定的断裂韧性特性可能与在准静态加载速率下测量的值不同。 事实上，当在脆性或延脆性状态下进行测试时，加载速率的增加会导致断裂韧性下降。 在完全延展性状态下观察到相反的情况（即断裂韧性增加）。 参考文献 [1] 中给出了有关断裂韧性对加载（或应变）速率的依赖性的更多信息。 此外，人们普遍认为断裂韧性还取决于试验温度。 由于这些原因，用户需要报告每次执行的测试的实际测试温度和加载速率。 如果铁素体钢在延性到脆性转变区域发生解理断裂，变异性可能非常大，并且无法通过简单的统计充分描述。 在这种情况下，需要进行额外的测试，并且使用适用于此类测试的统计程序进行分析，例如参见参考文献 [2]。 注：可能需要对参考文献[2]中规定的分析程序进行修改，以考虑升高（冲击）加载速率的影响。 [外文原描述]： ISO 26843:205 specifies requirements for performing and evaluating instrumented precracked Charpy impact tests on metallic materials using a fracture mechanics approach. Minimum requirements are given for measurement and recording equipment such that similar sensitivity and comparable measurements are achieved. Dynamic fracture mechanics properties determined using this International Standard are comparable with conventional large-scale fracture mechanics results when the corresponding validity criteria are met. Because of the small absolute size of the Charpy specimen, this is often not the case. Nevertheless, the values obtained can be used in research and development of materials, in quality control, and to establish the variation of properties with test temperature under impact loading rates. Fracture toughness properties determined through the use of this International Standard may differ from values measured at quasistatic loading rates. Indeed, an increase in loading rate causes a decrease in fracture toughness when tests are performed in the brittle or ductile-to-brittle regimes; the opposite is observed (i.e. increase in fracture toughness) in the fully ductile regime. More information on the dependence of fracture toughness on loading (or strain) rate is given in Reference [1]. In addition, it is generally acknowledged that fracture toughness also depends on test temperature. For these reasons, the user is required to report the actual test temperature and loading rate for each test performed. In case of cleavage fracture of ferritic steels in the ductile-to-brittle transition region, variability can be very large and cannot be adequately described by simple statistics. In this case, additional tests are required and the analysis is to be performed using a statistical procedure applicable to this type of test, see for example Reference [2]. NOTE Modifications to the analytical procedures prescribed in Reference [2] might be necessary to account for the effect of elevated (impact) loading rates.