Application of D. C. electrical potential method for measurement of J-R curve by a single specimen

The fracture toughness tests at temperatures from -600C to 1000C are conducted to develop the new method for the generation of the fracture resistance curve (J-R curve) by a single specimen. The three-point bend specimens with several configurations made of four kinds of nuclear reactor pressure vessel steels are used and the crack extention is measured by the d. c. electrical potential method during testing. From the results obtained, the following conclusions can be drawn: (1) The relation between the potential difference (V0 + δV)/V0 and the ratio of crack extention (a0 + δa)/a0 is a very little bit scattered regardless of the specimen size, type of steels or testing temperatures, when the specimen configurations are kept as the similar figure. Where, a0, δa, V0 and δV respectively denote the initial crack length, the amount of crack extention, the initial potential and the amount of potential difference. This relation is named here as the master curve. (2) Then, the J-δa relation (J-R curve) can be developed using the load-deflection record by a single specimen through the above mentioned master curve. (author)