Stress Generation Mechanism of Elbow Pipes due to Thermal Stratification

Abstract

In nuclear reactors, piping components are susceptible to thermal fatigue damage. This is due to the fluid temperature change along these pipelines that can generate repeated thermal loads. One of these loads is thermal stratification. Thermal stratification generates an oscillating stratified layer, which imposes a temperature fluctuation in the structures. This induces cyclic thermal stresses leading to fatigue damage. In past, several failure events of piping were accredited to thermal stratification and in elbow pipes in particular. This study aims at understanding the stress generation mechanism of elbow pipes subjected to thermal stratification. To accomplish this task, multiple Finite Element Models were implemented to highlight the main factors than can induce failure. the results obtained from the numerical analysis were compared with an analytical approach based on the frequency response method.