Simulations of crack extensions in arc-shaped tension specimens of uncharged and hydrogen-charged 21-6-9 austenitic stainless steels using cohesive zone modeling with varying cohesive parameters

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

“…The computational load-displacement, load-crack extension, crack extension-displacement and J-R curves of the A(T) specimens with the selected changing cohesive parameters can fit very well the test data as presented in Wu et al (2021). Sung et al (2019) simulated crack extensions in sub-sized bend specimens with sidegrooves made from an additively manufactured (AM) steel plate with the constant cohesive parameters.…”

“…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.…”

“…In this investigation, the calibration procedure of Wu et al ( 2021) is adopted. The detailed calibration steps were presented in Wu et al (2021) and briefly summarized here. In the first step, the 0 Γ and 0 T increase with increasing crack extension to fit the experimental displacement and crack extension corresponding to the experimental maximum load.…”

“…Therefore, the cohesive strength and cohesive energy should vary to reflect the change of the constraint conditions along the crack front during crack extension as indicated in Wu et al (2021).…”

“…For a fracture specimen with the sizes not satisfying Equation (1), side-grooves can be introduced to promote a uniform crack front during crack extension but the plane strain conditions along the crack front may not be satisfied. Wu et al (2021) simulated crack extensions in sub-sized arc-shaped tension (A(T)) specimens, as discussed in Kim et al (2004), with the constant and changing cohesive parameters. In contrast to the stress-state dependency of TSL based on the stress triaxiality of the neighboring continuum elements to the cohesive elements used in Brocks (2000a, 2000b), Anvari et al (2006), and Rashid and Banerjee (2017), Wu et al (2021) identified the changing cohesive strengths and energies with increasing crack extension based on the changing near-tip maximum opening stresses and separation work rates with increasing crack extension determined by 2-D FE analyses with nodal release as presented in Sung et al (2021a).…”