GB/T 24522-2009 in English

《GB/T 24522-2009金属材料 低拘束试样测定稳定裂纹扩展阻力的试验方法》由TC183（全国钢标准化技术委员会）归口，TC183SC4（全国钢标准化技术委员会力学及工艺性能试验方法分会）执行，主管部门为中国钢铁工业协会。
本标准规定了均匀金属材料低拘束裂纹体试样塑性变形在承受准静态加载时稳定裂纹扩展阻力δ5 和ΨC 的测定方法。紧凑拉伸试样和中心裂纹拉伸试样有缺口,采用疲劳的方法预制裂纹,在缓慢增加位移量的条件下进行试验。
本标准描述的试验方法涵盖那些不满足断裂性能尺寸不敏感的试样,例如尺寸相对单薄的紧凑拉伸试样和中心裂纹拉伸试样。

Scope

This standard specifies the method for the determination of the resistance to stable crack propagation when the plastic deformation of a low-constraint cracked body specimen of a homogeneous metallic material is subjected to quasi-static loading. The compact support specimen and the center crack tensile specimen have notches, and the fatigue method is used to prefabricate the crack, and the test is carried out under the condition of slowly increasing the displacement. The test methods described in this standard cover those size-insensitive specimens that do not meet the fracture properties, such as compact tensile specimens and central crack support specimens with relatively thin dimensions. This standard gives the method for determining the crack growth resistance curve (R-curve). According to GB/T 21143, determine the characteristic value of the fracture toughness of the compact tensile specimen, and the method for measuring the characteristic value of the fracture toughness of the central crack tensile specimen is given in Appendix D. Crack growth resistance can be measured using a multi-sample method or a single-sample method. The multiple-specimen method requires that each nominally identical specimen be loaded with some degree of displacement. The amount of ductile crack growth is marked, and the specimen is subsequently opened to measure crack growth. The single-specimen method based on the unloaded compliance method and the potentiometric method can also measure crack growth as long as the accuracy requirements can be met. The recommended single-sample method is described in GB/T 21143. Either way, the goal is to obtain enough data points to adequately describe the crack growth resistance behavior of the material. The determination of δ₅ is relatively simple and easy. The results for δ₅ are represented by resistance curves, showing the uniqueness of the crack growth for a certain limit range. Far from this limit range, the δ₅ resistance curve of the compact tensile specimen shows a strong dependence on the specimen width, while the δ₅ resistance curve of the central crack tensile specimen shows a strong dependence on the specimen width. Weak dependence on sample width. The experimental determination of CTOA is difficult. The critical CTOA is represented by the stable value reached after a certain degree of crack propagation. The concept of CTOA can be applied to a large amount of crack growth, and its applicability exceeds the application range of the existing δ₅. Both measurements of resistance to crack growth are suitable for structural evaluation. The concept of δ₅ is complete and can be applied to structural integrity problems through existing evaluation procedures based on simple crack driving force formulations. The concept of CTOA is generally more accurate. Numerical methods, such as finite element analysis, are required for structural applications. The study showed that when the two specimens were loaded to the maximum load, the CTOA and the unique R-curve maintained a close relationship. The analytic or numerical relationship between the δ₅-R curve and the critical CTOA remains to be further studied.