Normalization method used to determine fracture toughness with C-ring small size specimen and its application

With the miniaturization development of engineering components, thin plates and thin-walled tubes are widely applied in the industries of aerospace, nuclear power, chemical equipment and instrumentation, the estimation of fracture toughness by using small size specimens is of great importance for special demand of sampling and testing, but the current test method for the fracture properties of materials with small specimen is far from demands. A small size C-ring specimen is designed for determining fracture toughness of ductile materials and a new non-dimensional load separation method to estimate J-resistance curves of ductile materials for the C-ring specimen is proposed. J-resistance curves tests for 26NiCrMoV11-5 and A508-Ⅲ are carried out by use of C-ring specimens and compact tension (CT) specimens, respectively. The results show that, the specimen thickness and initial crack size have limited influence on fracture toughness of ductile materials obtained by C-ring specimens. Due to the higher level of constraint near the crack tip of the C-ring specimens, visible lower J-resistance curves can be observed in comparison the results of the CT specimens. ©, 2015, Journal of Mechanical Engineering. All right reserved.