Notch Effect on Structural Strength of Components at Elevated Temperature Under Creep, Fatigue, and Creep-Fatigue Loading Conditions: Phenomenon and Mechanism

Abstract

Structural discontinuities (e.g., nozzle, hole, and groove) widely occur in many high temperature components of nuclear and fossil power plants. In general, the notched component is used for simplified tests and analyses due to the complexity of the introduction of a practical component. In the previous work, the effects of the notch on failure life of the components have been reported experimentally, including the strengthening and weakening effects; however, the internal mechanisms have not been clearly demonstrated. This work reviews the notch effects on the structural strength of the notched components at elevated temperatures under creep, fatigue, and creep-fatigue loading conditions. Experimental phenomena (i.e., strengthening or weakening effects) for typical notched specimens subjected to the above three loading conditions are summarized, and the related factors for notch effects on creep rupture life or cycle to failure of the components are discussed. The mechanisms for the strengthening or weakening effects induced by a notch are described. Evaluation procedures for notch effect analysis under complex loading conditions are also included, and the primary challenges concerning the notch effect are provided for further investigations.

A dual-scale modelling approach for creep-fatigue crack initiation life prediction of holed structure in a nickel-based superalloy

“…As a brittle material Inconel 718, the hold time sensitivity to life reduction can be rationalized as that the stress re-distribution at stress concentration position (i.e. holed root) is relatively slow and the local accumulated plastic strain exceeds the limit required for fracture before attaining the stationary state [73].…”

Multiaxial fatigue behavior and life prediction of 2198-T8 Al-Li alloy notched tubular specimen based on DIC technique

“…Skallerud et al (2018) proposed a method, based on elastic-plastic stress field with gradient correction, to predict the main crack initiation location and fatigue crack initiation life of components with surface roughness. Gong et al (2019 reviewed the notch effects on the structural strength at elevated temperatures under creep, fatigue, and creep-fatigue loading conditions and described the mechanisms for the strengthening or weakening effects induced by one notch and two neighboring notches, respectively.…”