  Understanding the coupled thermo-mechanical behaviour of compacted granular
beds can benefit various industrial applications, such as pebble bed design in
fusion reactors. In this study, a thermo-mechanical discrete element method
based on our previous work is improved and adapted to investigate the cyclic
thermo-mechanical performance of gas-filled granular materials composed of
elastoplastic grains. An interparticle contact model is developed considering
the plastic deformation of grains. Through the simulation on a representative
volume element of beryllium pebble beds, we provide grain-scale insight into
the evolution of thermal conductivity and stress. The simulation results
suggest that the network of thermal contacts is impeded by plastic deformation
leading to a significant drop of thermal conductivity during cooling. This
effect can be suppressed by increasing the initial packing factor. Not limited
to pebble bed design, the conclusion of this work can also pave the way for
optimizing powder-based manufacturing and energy storage, where combined
thermo-mechanical loading conditions and elastoplastic deformation of
individual particles are involved.
