Alternative Displacement Procedures for J-R Curve Determination

This investigation evaluates alternative displacement techniques with the single-specimen compliance (SSC) procedure, which do not require the commonly used load-line displacement measurements in a compact toughness (CT) specimen to determine the J-R curve. The two techniques studied are a double clip gage technique involving both crack-mouth displacement and load-line displacement at the edges of the specimen and a technique that requires only crack-mouth displacement. J-R curves developed using these techniques are compared to J-R curves developed with the normal load-line based deflections. In addition, results of a round-robin program using the SSC procedure are discussed in terms of validating the double clip gage technique. J-R curves developed from crackmouth displacements on the J-integral specimen from ASTM Test for J_Ic, a Measure of Fracture Toughness (E 813) suggest that the ASTM Test Method for Plane-Strain Fracture Toughness of Metallic Materials (E 399) specimen design can be used for both linear-elastic (for example, K_Ic) and elastic-plastic (for example, J-R curve) toughness assessments. This fact can be of particular value in the testing of reactor surveillance specimens that may not have been machined to permit load-line displacement measurements.