The determination of Jq, the initiation elastic-plastic toughness parameter, using pre-cracked Charpy specimens

In order to assess the structural integrity of pressure vessel steels in the nuclear and chemical industries a need has arisen to measure fracture toughness using Charpy V-notch surveillance specimens.

This paper describes a procedure for determining the initiation fracture resistance, J_q of a material using pre-cracked Charpy specimens loaded in three-point bend. The size restrictions imposed by the geometry of a Charpy specimen on the measurement of the plane strain fracture toughness, K_IC, and the elastic-plastic toughness parameter, J_IC, are discussed for typical low- and medium-strength steels.

Consideration is given to the measurement of crack growth, side-grooving and the use of exclusion lines to interpret the fracture resistance, J, versus crack growth, Δa, curves.