A MODIFIED NORMALIZATION METHOD FOR DEVELOPING J-R AND CTOD-R CURVES WITH THE LMN FUNCTION

A direct method for obtaining J-R curves and delta-R curves from load- crack mouth opening displacement data is proposed. The method uses the direct method proposed by Landes, Herrera, Zhou, and Lee, based on th e geometric normalization suggested by Ernst for deeply cracked bend s pecimens, to develop calibration curves that relate load, crack mouth opening displacement, and crack length. Given two of these parameters, the third can be calculated from the calibration curves. These curves are developed by assuming a power law plus a straight line functional form with unknown L, M, and N constants and evaluating the unknowns a t three calibration points in the test. The method is studied for a HY -80 steel for four test temperatures and 50 mm-width, 25 mm-thickness side-notched single-edge bend specimens.