Global Ratcheting by Elastic-Plastic FEA According to ASME Section VIII Rules

Abstract

A framework of global ratcheting is developed for which the ratcheting measure is incremental permanent change of shape of a vessel or component. The changes of shape are such that they reduce the resistance to collapse, and, upon extended cycling, can lead to eventual failure by collapse. A ratcheting check is designed to prevent this failure. This framework fits the ratcheting rules that are currently in the 2010 Section VIII of the ASME B&PV Code. Tools are provided for ratcheting assessment based on this framework, and examples are presented that illustrate their application. BACKGROUNDNumerous papers have been published on ratcheting in conference proceedings and journals. Among those that use direct cycle-by-cycle, elastic-plastic FEA, the following are cited. Garud (1993) 1 reported experimental results on ratcheting of an elbow-pipe assembly and compared them with