Evaluation of Simplified Creep Design Methods Based on the Case Analysis of Tee Joint at Elevated Temperature

Abstract

Based on a tee joint, the simplified creep design methods of ASME code, elastic-perfectly plastic (EPP) analysis of Code Case N-861 (CC N-861) and the inelastic analysis by isochronous stress strain (ISS) curve, were evaluated and compared to nonlinear finite element creep analysis (FECA). Results indicate that both EPP and FECA lead to a greater inelastic strain than ISS curve-based results. By contrast, the ISS-based analysis induces a smaller usage fraction (damage) than FECA due to the underestimated inelastic strain. In addition, the smallest usage fraction (damage) is obtained by using EPP analysis of CC N-861 in which case the remarkable bending strain is involved.