Influence of heat flux loading patterns on the surface cracking features of tungsten armor under ELM-like thermal shocks

•Mechanism of cracking on tungsten surface observed in high heat flux thermal shock tests is elucidated.•Representative cracking patterns under ELM-like loads are reproduced by progressive fracture simulation.•Driving force for crack extension is assessed for various crack configurations and loading scenarios.•Effect of different heat flux profiles and temporal loading histories was quantitatively investigated. In this work, the influence of different high heat flux (HHF) loading patterns on the surface cracking of tungsten was investigated under edge-localized mode (ELM)-like thermal loads. Two numerical approaches were employed, namely, the extended finite element method (XFEM) and the virtual crack tip extension (VCE) method. Comparative assessment of initial cracking and crack growth was conducted for six HHF loading patterns (combinations of three spatial and two temporal variants) assuming the same deposited energy for all cases. A ramp pulse with a longer duration leads to slightly lower temperatures and stresses in comparison to a constant pulse with a shorter duration, and no significant difference in cracking appears for these two temporal loading scenarios. In the central part of the loading area, cracks propagate perpendicularly to the surface and the final length of these cracks is dependent on the applied power density. For both triangular and uniformly distributed HHF loadings, cracks initiated near the position, where the peak stress occurred at the surface, tend to kink from the initial vertical paths and then grow parallel to the surface. The driving force for this type of crack propagation is larger under uniform than triangular loading.