Study on Dimensional Tolerances Required for Miniature C(T) Specimens

Abstract

The Master Curve approach using the miniature C(T) specimens with 4 mm-thickness is a promising method for the direct determination of the reference temperature of reactor pressure vessel steels, because they can be taken from the broken halves of the Charpy specimens used for surveillance program to monitor neutron irradiation embrittlement. The dimensional tolerances of standard C(T) specimens are relatively provided in the present standard, ASTM E1921, consequently, absolute dimensional tolerances are severer for smaller specimens. In this paper, the effect of the tolerances of key dimensions on the elastic-plastic equivalent stress intensity factor derived from the J-integral, KJ, was calculated using three-dimensional finite element analysis. Even if the dimensional tolerances for the miniature C(T) specimens based on the present standard were mitigated in some degree (as examples, the tolerance of specimen thickness of ±0.08 mm was mitigated to ±0.1 mm, the tolerance of specimen width of ±0.04 mm was mitigated to ±0.1 mm), the variations of KJ and reference temperature were negligibly small. The use of the mitigated dimensional tolerances with adequate accuracy of fracture toughness evaluation was ascertained.