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http://dx.doi.org/10.20466/KPVP.2016.12.1.062

Evaluation of Fracture Toughness and Constraint Effect of Cruciform Specimen under Biaxial Loading  

Kim, Jong Min (한국원자력연구원 원자력재료안전연구부)
Kim, Min Chul (한국원자력연구원 원자력재료안전연구부)
Lee, Bong Sang (한국원자력연구원 원자력재료안전연구부)
Publication Information
Transactions of the Korean Society of Pressure Vessels and Piping / v.12, no.1, 2016 , pp. 62-69 More about this Journal
Abstract
Current guidance considers that uniaxially loaded specimen with a deep crack is used for the determination of the ductile-to-brittle transition temperature. However, reactor pressure vessel is under biaxial loading in real and the existence of deep crack is not probable through periodic in-service-inspection. The elastic stress intensity factor and the elastic-plastic J-integral which were used for crack-tip stress field and fracture mechanics assessment parameters. The difference of the loading condition and crack geometry can significantly influence on these parameters. Thus, a constraint effect caused by differences between standard specimens and a real structure can over/underestimate the fracture toughness, and it affects the results of the structural integrity assessment, consequentially. The present paper investigates the constraint effects by evaluating the master curve $T_0$ reference temperature of PCVN (Pre-cracked Charpy V-Notch) and small scale cruciform specimens which was designed to simulate biaxial loading condition with shallow crack through the fracture toughness tests and 3-dimensional elastic-plastic finite element analyses. Based on the finite element analysis results, the fracture toughness values of a small scale cruciform specimen were estimated, and the geometry-dependent factors of the cruciform specimen considered in the present study were determined. Finally, the transferability of the test results of these specimens was discussed.
Keywords
Cruciform specimen; Biaxial loading; Fracture toughness; Reference temperature; Finite element analysis; Constraint effect;
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