Simulations of Crack Extensions in Arc-Shaped Tension Specimens of Uncharged and Tritium-Charged-and-Decayed Austenitic Stainless Steels Using Cohesive Zone Modeling

Abstract

Crack extensions in arc-shaped tension specimens of uncharged and tritium-charged-and-decayed conventionally forged (CF) 21-6-9 austenitic stainless steels are simulated by two-dimensional finite element analyses using the cohesive zone modeling (CZM) approach with the smooth trapezoidal traction-separation law. The J integrals at the deviation loads of the arc-shaped tension specimens are taken as the reference cohesive energies and the maximum opening stresses ahead of the initial crack tips in the arc-shaped tension specimens are taken as the reference cohesive strengths. The cohesive strengths and cohesive energies are then adjusted to match the maximum loads of the experimental load-displacement curves of the arc-shaped tension specimens. The computational results showed that the computational load-displacement, load-crack extension, crack extension-displacement, and J-R curves of the uncharged and tritium-charged-and-decayed CF steel specimens are compared well with the experimental data.

Calibration of cohesive parameters for fracture test simulations of sub-sized bend specimens of AM steels

“…Various TSLs and frameworks of cohesive elements were developed for different applications. The smooth trapezoidal TSL (Cornec et al 2003;Brocks 2003, 2006;Sung et al 2019;Wu et al 2020Wu et al , 2021 was selected to simulate crack extensions in FE analyses of fracture specimens of ductile metals. The smooth trapezoidal TSL has the initial stiff part so that the initial responses of the experimental load-displacement curves of fracture specimens can be fitted well to check the accuracies of the FE analyses (Cornec et al 2003;Brocks 2003, 2006;Sung et al 2019;Wu et al 2020Wu et al , 2021.…”

“…Accurate computational results with the CZM approach for practical applications rely on the two most important cohesive parameters, cohesive energy and cohesive strength, which should be carefully calibrated. Usually, constant cohesive parameters such as constant cohesive strength and cohesive energy were adopted to simulate crack extensions in ductile metals (Roychowdhury et al 2002;Cornec et al 2003;Brocks 2003, 2006;Sung et al 2019;Wu et al 2020). For a fracture specimen or structure, where the size requirements of the plane strain conditions of the linear elastic fracture mechanics are satisfied at crack initiation and during crack extension, the selection of the cohesive energy can be a constant value related to the fracture toughness at crack initiation and during crack extension.…”