<p>In order to establish a guideline for fracture evaluation considering plastic constraint in the ductile-brittle transition temperature (DBTT) region, the CAF (Constraint-Based Assessment of Fracture in Ductile-Brittle Transition Temperature Region) subcommittee has been organized in the Japan Welding Engineering Society. The five-years committee commenced in 2018. The goal of the committee is to submit a draft guideline for fracture prediction of a reactor pressure vessel after a long-term operation without excessive conservatism. In the committee, fracture tests have been conducted using laboratory specimens of C(T) and SE(B), and 50mm-thick flat plate with a surface flaw subjected by bending load or tensile load. Simultaneously, the analytical tools for fracture evaluation owned by the committee members have been verified by benchmarking. The benchmark analyses were progressed in four steps; Step 0 was to confirm the output of finite element (FE) codes which the members owned by using the same FE input data and the same FE model. Step 1 was to confirm the output of Weibull stress analysis tools which the members developed. The focused model was a C(T) specimen which test was conducted at -125℃. The Weibull parameter, m, was fixed in this step. Step 2 was sensitivity analyses for mesh size effect, mesh type, etc. Also, the analysis output by the Gurson–Tvergaard–Needleman (GTN) model was confirmed. Final step was performed for simulation of a 10mm-thick flat plate tensile specimen already conducted outside the committee. Through the benchmark analyses, the effects of the used FE codes, element type, implicit or explicit, the used Weibull stress analysis program, etc. were investigated. Since the equivalence of the tools of the members has been confirmed, further analyses will be performed by using various fractured specimens as a next step.</p>

Benchmark Analysis by Beremin Model and GTN Model in CAF Subcommittee

Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2021/volume/85314

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