A physically-based method for predicting high temperature fatigue crack initiation in P91 welded steel

Zhou, Jinbiao, Barrett, Richard A., & Leen, Sean B. (2021). A physically-based method for predicting high temperature fatigue crack initiation in P91 welded steel. International Journal of Fatigue, 153, 106480. doi: https://doi.org/10.1016/j.ijfatigue.2021.106480

Abstract

A methodology is presented for physically-based prediction of high temperature fatigue crack initiation in 9Cr steels, with a focus on material inhomogeneity due to welding-induced metallurgical transformations. A modified form of the Tanaka-Mura model for slip band formation under cyclically-softening conditions is implemented in conjunction with a physically-based unified cyclic viscoplasticity constitutive model. The physically-based constitutive model accounts for the key strengthening mechanisms, including precipitate hardening and hierarchical grain boundary strengthening, successfully predicting cyclic softening in 9Cr steels. A five-material, finite element model of a P91 cross-weld test specimen, calibrated using the physically-based yield strength and constitutive models, successfully predicts the measured detrimental effect of welding on high temperature low-cycle fatigue crack initiation for P91 cross weld tests, via the modified Tanaka-Mura model. A key finding of the current work is the requirement to adopt an energy-based Tanaka-Mura method to account for cyclic softening in 9Cr steels, with packet size as the critical length-scale for slip band formation. The work demonstrates the significant effect of highly flexible operation on the service life of welded connections.

Funder

Science Foundation Ireland

Publisher

Elsevier

Rights

Attribution 4.0 International (CC BY 4.0)

cb

Collections

Mechanical Engineering (Scholarly Articles)