WHILE THE PRINCIPAL OBJECTIVE of this manual is to describe experimental aspects of elastic-plastic fracture testing, it is still necessary to define the quantities that we are measuring by presenting the ASTM standard equations that are currently used. The J-integral of Rice (1968) is defined in terms of a path integral not easily measured experimentally. For simple bend-type specimens, however, a straightforward analysis has been developed to relate J to the area under the load versus load point displacement record. Two different equations are used to evaluate J in ASTM fracture standards, the first applicable when the amount of crack extension is small, while the second includes a correction for crack extension.