Thickness Effect on the Brittle Fracture Toughness for SCMn 2A

The object of this paper is to evaluate the thickness effect on the brittle fracture toughness for SCMn 2A steel and to propose a formula in order to estimate the fracture toughness J_c for any thickness specimen. The compact tension specimens (CTS) are used in this test at 213°K (-60℃). It becomes clear that the J_c-values at which a brittle fracture occured were decreased extremely with an increasing thickness up to 20mm thickness and those values are nealy asympototic to the value of 40mm thickness specimen. And the proposed formula will make it possible to estimate the J_c-value for any thickness specimen by using one experimental J_c-value.