This paper is the first part of a two part paper. It describes the concepts of shakedown at elevated temperatures that form the foundation for proposed rules described in the second paper for extension of fatigue design rules in Section VIII, Division 2, Part 5 slightly into the creep range. These proposed rules use shakedown concepts and a cycle limit as a basis for exemption from fatigue analysis.
The 2010 version of B31.3 introduced sustained stress indices (SSI's) in paragraph 320. Using methods in references [1],[2],[3],[4],[5], and [11], a test procedure was developed to evaluate these SSI's for standard metallic piping components. The test procedure has been incorporated into draft versions of B31J so that the sustained stress index can be produced at the same time stress intensification or flexibility factor tests are performed for a particular component. This paper describes the sustained stress index and the B31J test procedure used to determine the SSI.
NOMENCLATUREde = elastic specimen displacement calculated from de = Fm / Ee. D = mean diameter of pipe Dnom = nominal diameter of pipe dn = displacement at the measurement point calculated from the elastic model of the test assembly used to find the elastic constant G 1
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