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Mitigation of Radiation and Hydrogen Damage with Laser Peening through Multiscale Modelling – Materials Strand Project

Supervisor: Gustavo Castelluccio (Cranfield University) and Chris Hardie (UKAEA)

1.Background and Motivation:

Material degradation is a leading challenge in developing viable nuclear fusion systems. Structural components in fusion reactors must withstand extreme combinations of temperature, irradiation, hydrogen exposure, and mechanical loading. However, current experimental facilities cannot fully reproduce the complex environments encountered in operating fusion devices, limiting our ability to assess material performance directly. As a result, multiscale, physics-based materials modelling has become the leading tool for designing improved material systems and optimising advanced manufacturing routes. Among the various degradation mechanisms, hydrogen and irradiation-induced damage from point defects are relevant to assess component lifetime. Recent studies [1–4] suggest that shock laser peening (SLP) is a promising approach to enhancing resistance against degradation. SLP is thought to reduce susceptibility to hydrogen and radiation embrittlement through a combination of mechanisms, including the introduction of beneficial compressive residual stresses, increased populations of defect sinks, and microstructural refinement. However, SLP may also have detrimental effects, such as increasing surface roughness or altering hydrogen diffusivity.

2. Research Problem and Hypothesis
Compared to conventional mechanical peening, SLP can induce significantly deeper surface modification and generate higher densities of dislocations and interfaces. To design an opti-mal manufacturing strategy, we must understand how these microstructural changes influence:
• Hydrogen and point-defect mobility,
• Mesoscale interactions between defects, residual stresses, and microstructural fea-tures, and
• The competition between dislocation networks and grain boundaries as defect sinks.

Hypothesis:
Hydrogen and irradiation tolerance can be substantially improved by SLP-induced microstructural modification—specifically, by increasing the density and effectiveness of defect sinks such as sessile dislocations structures and grain boundaries. Multiscale modelling of these interactions will enable the optimisation of laser-peening manufacturing processes.

3. Research Objectives

This PhD will address the following objectives:

  1. Quantify SLP-induced microstructural and residual stress states using a substructure-sensitive crystal plasticity framework informed by material characterisation,
  2. Model hydrogen and point-defect migration in relation to dislocation structures, grain boundaries, and stress fields,
  3. Integrate atomic-scale mobility data into mesoscale models to evaluate the relative effectiveness of defect sinks,
  4. Provide design guidelines for SLP process optimisation in fusion-relevant materials.

4. Methodology

A substructure-sensitive crystal plasticity model will be developed to simulate the microstructural state produced by SLP, capturing:

  • Residual stress distribution,
  • Dislocation density evolution,
  • Grain boundary formation and refinement,
  • Strain-rate sensitivity relevant to the high-strain-rate peening process.

Model predictions will be validated using experimental data such as residual stress measurements, dislocation densities (e.g., XRD), grain size and morphology (e.g., SEM/EBSD). Using atomistic data from the literature (e.g., DFT and MD datasets), the project will develop a mesoscale model describing hydrogen and of irradiation-induced point defects mobility in the presence of dislocation networks and grain boundaries. The model will explicitly consider diffusion time scales and the driving forces for segregation at microstructural features.

5. Expected Outcomes

  • A validated crystal plasticity model of SLP-induced microstructure,
  • A mesoscale migration and interaction model for hydrogen and irradiation defects,
  • An integrated tool for predicting embrittlement onset under relevant environments,
  • A scientific basis for advanced, damage-tolerant SLP manufacturing routes.

6. References

  1. Ghoniem, B. Singh, L. Sun, T.D.a de la Rubia. J. Nucl. Mater., 276 (1) (2000), pp. 166-177.
  2. Han, M. Demkowicz, E. Fu, Y. Wang, A. Misra. Acta Mater., 60 (18) (2012), pp. 6341-6351.
  3. -M. Bai, A.F. Voter, R.G. Hoagland, M. Nastasi, B.P.  Science, 327 (5973) (2010), pp. 1631-1634.
  4. P. Uberuaga, S. Choudhury, A. Caro. J. Nucl. Mater., 462 (2015), pp. 402-408

During the first six months of the PhD, materials strand students will typically travel to attend taught modules at all six of the Fusion CDT partner universities.

The work, being mostly computational, can be performed remotely after attending the courses.

There are multiple opportunities to travel to visit collaborators and attend conferences, particularly in the US where the sponsor comes from.

This project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.

This project is being offered by Cranfield University as part of the Fusion CDT Community Studentship scheme.

Applications are made via the Cranfield University website and the application deadline is 29 April 2026. 

For further information and details of how to apply please contact Gustavo Castelluccio (castellg@cranfield.ac.uk).

Image above: This figure demonstrates the multi scale nature of metals. This project integrates knowledge across scale to advance damage-resistant materials.