This paper presents a single-specimen method of evaluating the fracture toughness of nuclear pressure vessel steels by using a small round compact tension (RCT) specimen with deep side-grooves. The method has been used to estimate the fracture toughness parameters of the nuclear pressure vessel steels A508CL3-A, A508CL3-B and A508CL3-A' produced by two plants. A comparison of the measured fracture toughness results has been done among the small RCT specimen, the Charpy-size specimen and the large specimen, which GB2038 and ASTM E813 require. The research results indicate that the fracture toughness values obtained from the RCT specimens with the double-size deep side-grooves have little difference when compared with the valid fracture toughness results. Finally, this paper discusses the possibility of using the RCT specimens in nuclear pressure vessel steel embrittlement surveillance.

Controlling the dissolution of the base metal in the liquid filler metal is very significant for both brazing and soldering processes, in particular for high temperature brazing. A model for quantitatively evaluating the dissolution thickness of base metal in liquid brazing filler metal is established, that produces consistent predictions with experiment.

Basedon a CEGB/R6 two-parameter fracture analysis approach, the present studyhas proposed theoretical formulae to predict the elastic-plastic fracture toughness requirement of structures with both homogeneous materials and mismatched weldments. The fracture toughness requirement of homogeneous material structures is mainly related to the yield strength of materials, applied stress, stress concentration, residual stress and postulated crack size. However, the fracture toughness requirement of mismatched weld metal is also related to the mismatched strength of welds. It is expected that the formulae are suitable for predicting the elastic-plastic fracture toughness requirement of most welded structures including pressure vessels and piping.

The ductile fracture of structural steel including weldment can be described as a progressive process with void nucleation, growth and coalescence. The effects of mechanical heterogeneity of the weldment were investigated experimentally on the ductile fracture behaviors of the base metal and the weld metal using round-bar tensile notched bars. The results show that the mechanical heterogeneity of weldment has certain effects on fracture strain, stress triaxiality at fracture, critical void growth and the material constant C. The smaller the distance between the notch root and the fusion line, the larger the fracture stain, the smaller the stress triaxiality and the larger the critical void growth rate.

For the estimation of fracture mechanics parameters of cracked weldment with mechanical heterogeneity, there exist equivalent yielding stress and equivalent strain hardening exponents in the vicinity of the crack tip keeping the assessment of fracture mechanics parameters of weldment in the same way as the homogeneous material. In this paper, the factors such as width of weld, matching property, stress condition, and the mechanical properties of base metal and weld metal affecting the equivalent yielding stress and equivalent strain hardening exponents are carefully studied. The results show that the width of weld and matching property of weldment have a strong effect on the equivalent parameters while the stress condition has little effect on the equivalent parameters. Furthermore, the two equivalent parameters change independently from each other.