Session: CS-07-02 Recent Developments in ASME Codes and Standards II

Paper Number: 61658

Start Time: Wednesday, July 14, 2021, 08:00 PM

61658 - Evaluation of Primary-Load Effects on Creep-Fatigue Life of Alloy 617 Using Simplified Model Test Method 

Current creep-fatigue evaluation approaches based on the creep-fatigue Damage-diagram are complex and conservative. Simplified Model Test (SMT) method is an alternative approach to determine cyclic life at elevated temperatures. The SMT-based creep-fatigue evaluation methodology avoids parsing the damage into creep and fatigue components and greatly simplifies the evaluation procedure for elevated temperature cyclic service. In this study, the effects of sustained primary stress loading are evaluated in support of the development of SMT-based creep-fatigue design curves for Alloy 617.

Experiments were designed and performed using internal pressurized tubular specimens at 950C on Alloy 617. The sustained primary load was introduced by the internal pressure. A newly developed SMT technique, single-bar SMT, was extended to these tests and SMT creep-fatigue test data were generated with various elastic follow-ups, internal pressures and strain ranges. The test results from this study along with the original SMT data on Alloy 617 demonstrate that, although internal pressure is within the allowable pressure limit, the SMT creep-fatigue cycles to failure were reduced for the cases tested with primary pressure load.  The reduction of SMT creep-fatigue life due to primary load was found to be dependent on strain ranges and elastic follow up. Approaches to handle the primary load effect on SMT design curves are discussed.

Presenting Author: Yanli Wang Oak Ridge National Laboratory

Authors:

Yanli Wang Oak Ridge National Laboratory
Peijun Hou University of Tennessee, Knoxville
Robert Jetter R. I. Jetter Consulting
T. L. Sham Argonne National Laboratory