Review of fracture toughness (G, K, J, CTOD, CTOA) testing and standardization

The present paper gives a technical review of fracture toughness testing, evaluation and standardization for metallic materials in terms of the linear elastic fracture mechanics as well as the elastic–plastic fracture mechanics. This includes the early investigations and recent advances of fracture toughness test methods and practices developed by American Society for Testing and Materials (ASTM). The review describes the most important fracture mechanics parameters: the elastic energy release rate G, the stress intensity factor K, the J-integral, the crack-tip opening displacement (CTOD) and the crack-tip opening angle (CTOA) from the basic concept, definition, to experimental estimation, test methods and ASTM standardizing practices. Attention is paid to guidelines on how to choose an appropriate fracture parameter to characterize fracture toughness for the material of interest, and how to measure the fracture toughness value defined either at a critical point or in a resistance curve format using laboratory specimens. The relevant ASTM fracture toughness test standards considered in this paper are E399 for KIc testing, E561 for K–R curve testing, E813 for JIc testing, E1152 for J–R curve testing, E1737 for JIc and J–R curve testing, E1290 for CTOD (δ) testing, a combined common test standard E1820 for measuring the three parameters of K, J and δ, E1921 for the transition reference temperature T0 testing and the master curve of cleavage toughness KJc testing, and E2472 for CTOA testing. The effects of loading rate, temperature and crack-tip constraint on fracture toughness as well as fracture instability analysis are also reviewed.

► This paper reviews fracture toughness testing, evaluation and standardization at ASTM.
► It relates to the linear elastic fracture mechanics and the elastic–plastic fracture mechanics.
► The review describes the most important fracture mechanics parameters of G, K, J, CTOD, and CTOA.
► ASTM fracture test standards discussed are E399, E561, E813, E1152, E1737, E1290, E1820, E1921 and E2472.