TY - JOUR
T1 - A mechanistic interpretation of Nelson curves for PVP failures under high temperature hydrogen attack
AU - Han, Dong
AU - Gao, Yanfei
AU - Loya, Phillip E.
AU - Swindeman, Michael
AU - Penso, Jorge
AU - Feng, Zhili
N1 - Publisher Copyright:
© 2024 Elsevier Ltd
PY - 2024/9
Y1 - 2024/9
N2 - As an empirically established design criterion, Nelson curves that relate the service temperature and the allowable hydrogen partial pressure have been developed and utilized for more than sixty years in pressure vessels and piping (PVP) safety design. Despite a relatively clear thermodynamic understanding of the high-temperature-hydrogen-attack (HTHA) problem, the detailed fracture process on the microstructural length scales, however, remains elusive, and a quantitative assessment of the PVP lifetime under HTHA from the available creep fracture dataset is still not possible. This work develops a microstructure-informed and micromechanics-based model by incorporating a synergy between hydrogen transport and intergranular-cavity-based fracture process. Based on the available creep lifetime data of C-0.5Mo steels, we are able to calibrate material constitutive parameters, and then conduct nonlinear finite element simulations that reveal a real-time stress-induced hydrogen diffusional transport along grain boundaries, coupled with a microstructure-explicit failure process, from which Nelson curves can be computed. Such failure analyses allow us to delineate two distinct regimes on the Nelson curves, i.e., dislocation-creep-controlled or grain boundary diffusion-assisted cavity growth. More importantly, we found that a small change of the pipe thickness and applied stresses can significantly shift these lifetime curves. However, these two parameters are usually not provided in Nelson curves, thus limiting their usage in material selection and safety design. This discrepancy can clearly be mitigated by extensive parametric studies from our micromechanical modeling/simulation framework.
AB - As an empirically established design criterion, Nelson curves that relate the service temperature and the allowable hydrogen partial pressure have been developed and utilized for more than sixty years in pressure vessels and piping (PVP) safety design. Despite a relatively clear thermodynamic understanding of the high-temperature-hydrogen-attack (HTHA) problem, the detailed fracture process on the microstructural length scales, however, remains elusive, and a quantitative assessment of the PVP lifetime under HTHA from the available creep fracture dataset is still not possible. This work develops a microstructure-informed and micromechanics-based model by incorporating a synergy between hydrogen transport and intergranular-cavity-based fracture process. Based on the available creep lifetime data of C-0.5Mo steels, we are able to calibrate material constitutive parameters, and then conduct nonlinear finite element simulations that reveal a real-time stress-induced hydrogen diffusional transport along grain boundaries, coupled with a microstructure-explicit failure process, from which Nelson curves can be computed. Such failure analyses allow us to delineate two distinct regimes on the Nelson curves, i.e., dislocation-creep-controlled or grain boundary diffusion-assisted cavity growth. More importantly, we found that a small change of the pipe thickness and applied stresses can significantly shift these lifetime curves. However, these two parameters are usually not provided in Nelson curves, thus limiting their usage in material selection and safety design. This discrepancy can clearly be mitigated by extensive parametric studies from our micromechanical modeling/simulation framework.
KW - High temperature hydrogen attack (HTHA)
KW - Intergranular fracture
KW - Microstructure-informed and micromechanics-based model
KW - Nelson curves
UR - http://www.scopus.com/inward/record.url?scp=85197548879&partnerID=8YFLogxK
U2 - 10.1016/j.mechmat.2024.105079
DO - 10.1016/j.mechmat.2024.105079
M3 - Article
AN - SCOPUS:85197548879
SN - 0167-6636
VL - 196
JO - Mechanics of Materials
JF - Mechanics of Materials
M1 - 105079
ER -