Toughness Rules in the New ASME Section VIII Division 2 Code

The PVRC proposal to ASME for the new Section VIII Division 2 incorporates fracture mechanics more rigorously than before in setting the toughness requirements for materials. The concepts of driving force for fracture and materials resistance as a function of temperature are linked through the concept of a FAD, that is now widely accepted. On the driving force side the latest technologies are available for incorporation via PVRC and MPC in the form of improved expressions for stress intensities, recently calculated by FEA and available in WRC Bulletins or API 579 on Fitness for Service. These do not require elaboration here. One aspect of the driving force side that will be noted, however, is the allowed reduction in MDMT associated with reduction of applied stress or pressure to values below the maximum permitted values. Recent analysis of the principles implicit in the current of ASME indicates that a new rational taking greater cognizance of the effects of secondary or residual stresses and the effects of heat treatment is appropriate.