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http://dx.doi.org/10.3795/KSME-A.2003.27.11.1986

A Study on Accuracy of J-Resistance Curves Measured with Curved Compact Tension Specimen of Zr-2.5Nb Pressure Tube  

Yoon, Kee-Bong (중앙대학교 기계공학부)
Park, Tae-Gyu (중앙대학교 대학원)
Kim, Young-Suk (한국원자력연구소)
Publication Information
Transactions of the Korean Society of Mechanical Engineers A / v.27, no.11, 2003 , pp. 1986-1996 More about this Journal
Abstract
Methodology based on the elastic-plastic fracture mechanics has been widely accepted in predicting the critical crack length(CCL) of pressure tubes of CANDU nuclear plants. A conservative estimate of CCL is obtained by employing the J-resistance curves measured with the specimens satisfying plane strain condition as suggested in the ASTM standard. Due to limited thickness of the pressure tubes the curved compact tension(CT) specimens taken out from tile pressure tube have been used in obtaining J-resistance curves. The curved CT specimen inevitably introduce slant fatigue crack during precracking. Hence, effect of specimen geometry and slant crack on J-resistance curve should be explored. In this study, the difference of J integral values between the standard CT specimens satisfying plane strain condition and the nonstandard curved CT with limited thickness (4.2mm) is estimated using finite element analysis. The fracture resistance curves of Zr-2.5Nb obtained previously by other authors are critically discussed. Various finite element analysis were conducted such as 2D analysis under plane stress and plane strain conditions and 3D analysis for flat CT, curved CT with straight crack and curved CT with slant crack front. J-integral values were determined by local contour integration near the crack tip, which was considered as accurate J-values. J value was also determined from the load versus load line displacement curve and the J estimation equation in the ASTM standard. Discrepancies between the two values were shown and suggestion was made for obtaining accurate J values from the load line displacement curves obtained by the curved CT specimens.
Keywords
Zr-2.5Nb; Curved Compact Tension Specimen; J-integral; Critical Crack Length; CANDU Pressure Tube; Zr-2.5Nb; Finite Element Analysis;
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