Structural Health & Prognostics

Physics-based life assessment and prognostics for welds, coatings, and pressure components — keeping energy infrastructure safely in service.

Why it matters

Much of the world's energy infrastructure — boiler tubes, heat-transport pipelines, turbine coatings, pressure vessels — is operating well beyond its original design life. Replacing it all is unaffordable; running it blind is unsafe. The engineering answer is prognostics and health management (PHM): knowing how much life a component has left, and what can be done to extend it. We take a model-based approach to PHM, rooted in fracture mechanics and materials science: models that predict when and where a component will fail, treatments that push that moment further out, and — increasingly — sensors and AI that update the prediction from real operating data.

What we do

Girth-weld specimen with attached sensor, residual stress contour and remaining-life curve

Figure 1. Weld specimen with in-situ sensing, residual-stress analysis, and remaining-life estimation.

Creep and fatigue life assessment of high-temperature components. Using hierarchical multiscale analysis combined with creep-cavitation models, we predict the remaining creep life of new and service-exposed boiler tubes (9Cr-1Mo T91, Super304H stainless steel) and quantify how long-term service changes their microstructure and precipitates. The same framework supports cost-based optimization of tube design and replacement schedules for thermal power plants.

Welding residual stress and life extension of pipelines. Field girth welds are the weakest link in buried heat-transport pipelines. In a project with a national district-heating utility we analyze residual stresses in multi-pass welds and evaluate post-weld treatments — ultrasonic impact treatment and others — that relieve them, aiming to extend the service life of welds that cannot be heat-treated in the field.

Fracture mechanics of interfaces and coatings. Our foundation is analytical and computational fracture mechanics: interface cracks between dissimilar and anisotropic materials, subsurface cracks under moving contact loads, residual stress in thin films, and — with phase-field simulation — spallation of thermal barrier coatings under thermal cycling. These models tell us how damage initiates and grows at the interfaces where real components fail.

Toward sensor-informed prognostics. Life models are only as good as their inputs. Building on our sensor programs, we are working to embed fiber and film sensors on structures so that measured strain and vibration continuously update remaining-life estimates — the link between structural health monitoring and true prognostics.

Key capabilities

Creep and creep–fatigue life assessment (Larson–Miller, creep-cavitation models, microstructure-based multiscale analysis)
Welding residual-stress simulation and post-weld treatment evaluation
Interface fracture mechanics: analytical singularity and crack solutions, cohesive-zone and phase-field models
Thermal barrier coating damage and spallation modeling
Fitness-for-service evaluation of pressure components
Sensor integration for structural health monitoring (with the Smart Fibers and Haptics tracks)

Selected publications

V. Lok, T. G. Le, J. M. Yu, Y. W. Ma, V. P. Nguyen, S. T. Choi, and K. B. Yoon*, Changes in creep property and precipitates due to aging of T91 steel after long-term service, Journal of Mechanical Science and Technology, 2020. [DOI]
V. P. Nguyen, F. Ibupoto, L. Q. Pham, W. Choi, K. Shin, M. K. Kim*, and S. T. Choi*, Creep lifetime prediction of new and service-exposed 9Cr-1Mo (Grade T91) steel boiler tubes based on hierarchical multiscale analysis and creep cavitation model, Materials at High Temperatures, 2020. [DOI]
L. Q. Pham, V. P. Nguyen, T. M. Jeong, K. B. Yoon, L. Xu, K. Shin, and S. T. Choi*, Creep lifetime prediction of virgin and service-exposed Super304H austenitic stainless-steel boiler tubes based on hierarchical multiscale analysis and creep cavitation model, Materials at High Temperatures, 2020. [DOI]
V. P. Nguyen, S. Lee, W. Choi, and S. T. Choi*, Effect of creep lifetime on cost-based optimization of boiler tubes for thermal power plants, Materials at High Temperatures, 2019. [DOI]
A. T. Al-Motasem, N. T. Mai, S. T. Choi*, and M. Posselt, Atomistic study on mixed-mode fracture mechanisms of ferrite iron interacting with coherent copper and nickel nanoclusters, Journal of Nuclear Materials, 2016. [DOI]
J.-S. Wen, T.-K. Han, S. T. Choi, and K.-S. Lee*, Finite element analysis of a subsurface penny-shaped crack with crack-face contact and friction under a moving compressive load, Journal of Mechanical Science and Technology, 2012. [DOI]
Y. T. Im, S. T. Choi*, T. S. Park, and J. H. Kim, Study on residual stress in viscoelastic thin film using curvature measurement method, KSME International Journal, 2004. [DOI]
S. T. Choi, H. Shin, and Y. Y. Earmme*, On the unified approach to anisotropic and isotropic elasticity for singularity, interface, and crack in dissimilar media, International Journal of Solids and Structures, 2003. [DOI]

Full list: Publications

Industry & careers

This track connects to energy public corporations and plant operators, power-equipment manufacturers, engineering and inspection firms, and nuclear and thermal power maintenance organizations. Students gain a rare combination of fracture mechanics, materials degradation, finite element simulation, and — increasingly — data-driven prognostics. Typical career paths include structural integrity engineer, PHM / reliability engineer, welding and materials engineer, and plant life-management specialist.

FMAM Lab

Structural Health & Prognostics