Optimized modeling of fracture-critical structural components and connections requires the application of elastic-plastic fracture mechanics. However, such applications can require sophisticated analytical techniques that require time and/or resources beyond those available to the designer. One of the first engineering tools to address this dilemma was The Welding Institute CTOD Design Curve and was included in the first edition of the British Standards Institution (BSI) fitness-for-purpose guidance PD 6493. The engineering tool receiving attention currently is the Failure Assessment Diagram (FAD). This approach has been used, primarily, in the electric power industry both in Great Britain as the R6 criteria and the U.S. as both the Failure Assessment Diagram and the Deformation Plasticity Failure Assessment Diagram (DPFAD). Both the R6 and DPFAD approaches utilize the J-integral criteria for fracture driving force and resistance (i.e., toughness). Also, The second edition of the BSI PD 6493 presents failure assessments in the form of FAD's using crack-tip opening displacement (CTOD)as crack-driving force.
"Engineering Approaches to Elastic-Plastic Failure Assessment," Bethlehem Steel Corporation, Bethlehem, Pa., November 7, 1994.