Numerical Simulation of Thermal Stress and Creep Fatigue Crack Growth Analysis for Thick-Walled Tubes of Header

Abstract

The super heater outlet headers usually operate at high temperatures in excess of 900 ℉ and are subject to thermal stresses, pressure stresses, fatigue, creep that can lead to cracking and failure of components. In fact, crack and failure often occur at the tubes before at the cylinder part of header. However, in recent years, many studies have been focused in order to develop a model for remaining life and crack growth assessment of cylinder part. In this study, thermal stress using finite element simulation and creep fatigue crack growth analysis for thick-walled tubes of header were performed for failure analysis. Numerical simulation of thermal stress was carried out to find local positions which occurs maximum stress potential leading to failure. Crack growth failure and remaining life assessment of the cracked tube were employed based on creep fatigue crack growth laws to determine the time required for the crack to grow into a failure and the initial defect crack size that causes crack propagation. The results from the assessment show that crack growth of tubes and cylinder part of header propagate to damage by two main reasons including fatigue crack growth due to temperature fluctuations and creep crack growth during steady state operation. In addition, the remaining life is much more dependent on fatigue crack growth than creep crack growth during service time. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.