A BASIS FOR APPLYING ELASTIC PERFECTLY-PLASTIC DESIGN METHODS TO CYCLIC SOFTENING MATERIALS

Conference · Sun Jul 01 04:00:00 EDT 2018

OSTI ID:1474440

Messner, Mark C. ^[1]; Wang, Yanli ^[2]; Jetter, Robert I. ^[3]; Sham, T.-L. ^[1]

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1. Argonne National Laboratory (ANL)
2. ORNL
3. Consultant

Design approaches using elastic perfectly-plastic (EPP) analysis have recently been approved as Code Cases for the Section III, Division 5 design of high-temperature nuclear reactor components made from austenitic stainless steel. These methods bound the ratcheting strain and creep-fatigue damage accumulated over the life of a component with a simplified, elasticperfectly plastic analysis using a special pseudo-yield stress – often not equal to the true material yield stress. The austenitic materials specified in the existing Code cases are cyclic-hardening for all allowable operating temperatures. However, other Section III, Division 5 materials, such as Grade 91 steel, are cyclic softening at expected advanced reactor operating temperatures. This work describes the extension of EPP methods to cyclic softening materials through the use of a postulated saturated material state and softening factors to be applied to the pseudo yield stress. We demonstrate the conservatism of the modified EPP method against a series of inelastic simulations of two bar tests, using a constitutive model that captures work and cyclic softening.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1474440
• Country of Publication: United States
• Language: English