金属和合金的腐蚀.应力腐蚀试验.第6部分:预破裂试样的制备和使用

[中文适用范围]： 本文件规定了设计、制备和使用预裂纹试样来研究应力腐蚀敏感性的程序。它为设计、制备和使用预裂纹试样来研究应力腐蚀敏感性给出了建议。有关缺口试样的建议见附件 A。本文件中使用的术语“金属”包括合金。由于需要限制裂纹尖端的塑性，预裂纹试样不适用于评估薄产品（如薄板或线材），通常用于较厚的产品（包括板材和锻件）。它们也可用于通过焊接连接的部件。预裂纹试样可以加载设备以施加恒定载荷，也可以结合使用装置在载荷点产生恒定位移。在增加位移或增加载荷下进行的测试在 ISO 7539-9 中处理。预裂试样的一个特殊优势是，它们能够获取数据，根据这些数据，可以估算已知几何形状的部件在已知应力作用下的临界缺陷尺寸（超过该尺寸，应力腐蚀开裂就会发生）。它们还能确定应力腐蚀开裂的扩展速率。在监测使用过程中含有缺陷的部件时，可以考虑后者的数据。 [外文原描述]： This document specifies procedures for designing, preparing and using precracked specimens for investigating susceptibility to stress corrosion. It gives recommendations for the design, preparation and use of precracked specimens for investigating susceptibility to stress corrosion. Recommendations concerning notched specimens are given in Annex A. The term "metal" as used in this document includes alloys. Because of the need to confine plasticity at the crack tip, precracked specimens are not suitable for the evaluation of thin products, such as sheet or wire, and are generally used for thicker products including plate bar and forgings. They can also be used for parts joined by welding. Precracked specimens can be loaded with equipment for application of a constant load or can incorporate a device to produce a constant displacement at the loading points. Tests conducted under increasing displacement or increasing load are dealt with in ISO 7539-9. A particular advantage of precracked specimens is that they allow data to be acquired, from which critical defect sizes, above which stress corrosion cracking can occur, can be estimated for components of known geometry subjected to known stresses. They also enable rates of stress corrosion crack propagation to be determined. The latter data can be taken into account when monitoring parts containing defects during service.