GB/T 21143-2025 Metallic materials—Unified method of test for determination of quasistatic fracture toughness

Scope

This document describes the test method for determining the fracture toughness and resistance curves of homogeneous metal materials under quasi-static loading in terms of K, δ, and J. The specimens contain notches, and the cracks are pre-manufactured by fatigue methods. The tests are conducted under conditions of slowly increasing displacement. The fracture toughness is determined by the state of the specimens when ductile crack propagation occurs, when ductile crack propagation becomes unstable, or after the occurrence of non-stable crack propagation. When the crack propagation exhibits stable propagation under ductile tearing conditions, the resistance curve that measures the relationship between fracture toughness and crack propagation can be determined. When testing certain ferritic materials, non-stable crack propagation caused by cleavage or the initiation and propagation of ductile cracks being interrupted by cleavage expansion may occur. The crack restraint conditions are not discussed in this document. GB/T 28896 supplements the special test requirements and data processing procedures for welding materials.
Note: The statistical differences in test results are related to the type of fracture. For example, the fracture toughness values obtained from cleavage fractures in ferritic steel will fluctuate. For cases requiring high reliability, the reference [4] provides a method for quantitatively characterizing the fluctuation of fracture toughness values in the region of ductile-brittle transition. This document does not provide further explanations on the number of tests and the application and understanding of test results in such cases.

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