ASTM E2472-12(2018)

1.1 This standard covers the determination of the resistance to stable crack extension in metallic materials in terms of the critical crack-tip-opening angle (CTOA), ψ_c and/or the crack-opening displacement (COD), δ₅ resistance curve (1).2 This method applies specifically to fatigue pre-cracked specimens that exhibit low constraint (crack-size-to-thickness and un-cracked ligament-to-thickness ratios greater than or equal to 4) and that are tested under slowly increasing remote applied displacement. The test specimens are the compact, C(T), and middle-crack-tension, M(T), specimens. The fracture resistance determined in accordance with this standard is measured as ψ_c (critical CTOA value) and/or δ₅ (critical COD resistance curve) as a function of crack extension. Both fracture resistance parameters are characterized using either a single-specimen or multiple-specimen procedures. These fracture quantities are determined under the opening mode (Mode I) of loading. Influences of environment and rapid loading rates are not covered in this standard, but the user must be aware of the effects that the loading rate and laboratory environment may have on the fracture behavior of the material.