Assessment Methods of Bree Type Ratcheting Without the Necessity of Linearization of Stresses and Strains

Pressurized component design codes based on design-by-analysis require the evaluation of thermal ratcheting produced by the combination of primary and cyclic secondary stresses. In the current codes for nuclear power components provide domain categorization type evaluation methods of progressive strain, using Miller's or Bree's diagram. When these methods are used with elastic analysis, the stress classification procedure with linearization of stress distribution is needed. When elastic-plastic analysis, which directly estimates accumulation trend of strains, is performed, the linearization of strain is necessary to assess the acceptability of progressive bending strain following the high temperature component design codes. These procedures for linearization can not be applied straight forwardly to general three-dimensional geometries. This paper proposes evaluation methods of Bree type ratcheting without the necessity of linearization of stresses and strains. The methods presented are based on surface strain increment or elastic core size, and are applicable to both smooth and notched components without losing the consistency with the current codes.