Session: MF-16-01 Creep and Creep-Fatigue Interaction-1

Paper Number: 122915

122915 - A Continuum Damage Coupled Unified Constitutive Model for Creep-Fatigue Damage Evaluation of Modified Grade 91 Tube Sheet Structures Under Flexible Loading Conditions 

The Grade 91 tube-sheet structure is a critical integral part of Sodium Fast Reactors (SFR) developed by the Japan Atomic Energy Agency. Life evaluation of such a component is complex because of its geometry with the numerous holes and combined fatigue-creep loading conditions at elevated temperatures. The Sodium in the SFR tube sheets is flowed at the operating temperature varied from 650 and 250  for hot and cold transients. For these components, the fatigue-creep damage evaluation is commonly performed using simplified approaches such as the Stress Redistribution Locus (SRL) method or non-unified constitutive models where creep and plastic strains are not coupled. However, understanding the behavior of Grade 91 steel under fatigue, creep and fatigue-creep loading conditions and its constitutive model based on these phenomena are important to properly predict the component responses. Hence, this study developed a 3D FE model of the tube-sheet component, utilized the advanced damage coupled unified constitutive model (UCM-CDM) of Mod. Grade 91, formulated by the author earlier, to analyze the creep-fatigue strength of the tube sheet under combined flexible loading. The damage estimation using the UCM-CDM model is compared with other commonly used non-unified models, and the robustness of the UCM-CDM model is discussed.

Presenting Author: Nazrul Islam Bangladesh University of Engineering and Technology

Presenting Author Biography: Nazrul Islam received Bachelor of Science degree in Civil Engineering with a specialization in structural engineering from Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh in 2007. He completed Master of Science degree in Civil (Structural) Engineering from the same institution with a research focus on structural optimization. He joined as a lecturer in the Civil Engineering Department of BUET after completion of the bachelor degree and promoted as an Assistant Professor in 2011. For pursuing higher studies with the commitment to serving the community, Nazrul Islam moved to the USA and started doctoral studies in Structural Mechanics at North Carolina State University, Raleigh, NC. His Ph. D. research focused on developing advanced constitutive models for room and high-temperature applications in the fossil and nuclear power industries. As a part of doctoral studies, he worked on the research projects funded by the Department of Energy (DOE), National Science Foundation (NSF) and the Fossil Power division of the Babcock and Wilcox Company, Ohio, USA. Dr. Islam moved back to his home country after completion of his doctoral studies and rejoined as an Assistant Professor at BUET. Now he is serving as a Professor in the same department of BUET. Dr. Islam also holds a PE license to practice Civil Engineering (Structural) in the State of North Carolina, USA.

Authors:

Nazrul Islam Bangladesh University of Engineering and Technology
Md Sumon Hossain Geotech and Structures Ltd