JR-Curve Testing of Three-Point Bend Specimens by the Unloading Compliance Method

Abstract

The unloading compliance technique for JR-curve testing is not well established for single-edge notched specimens loaded in three-point bending (SENB) to date. This paper investigates various effects hampering the successful application of the method of SENB specimens. It is shown that the specimen's compliance is significantly affected by rotation of the specimen halves during deformation and stable crack extension. By contrast, the effects of roller indentation, outer roller movements and friction, and of crack front curvature are relatively minor. Based on these findings, a general procedure is proposed for correcting the experimentally measured compliance of SENB specimens for the above effects. Crack extensions predicted for three steels from SENB unloading compliance experiments incorporating the proposed corrections are seen to correlate within ±10% with dye penetrant beachmarks made at several points during the tests.