Effect of impact velocity on the variation pattern of dissipated thermal energy during rock crushing process

Crushing is an energy-intensive process in which only a small fraction of the input energy is used for crack generation, while a considerable portion is dissipated in thermal energy. Clarifying the evolution of dissipated thermal energy during impact crushing is therefore important for understanding fragmentation efficiency and optimizing loading conditions. In this study, a calibrated Particle Flow Code (PFC) model for green sandstone was established based on laboratory tests and micro-parameter calibration. Within an energy-partition framework, dissipated thermal energy was quantified using the irreversible dissipation components tracked in the model. Two indicators, namely the thermal dissipation ratio and the specific dissipated thermal energy ( G h ), were introduced to characterize the relationship among dissipated thermal energy, energy partitioning, and fragmentation effectiveness. The results show that dissipated thermal energy increases overall with impact velocity. From the viewpoint of the physical dissipation mechanism, the relative importance of friction-induced heating and plastic-deformation-related heating changes progressively with increasing impact velocity; in the calibrated PFC model, this evolution is reflected by the changing contributions of sliding-related dissipation and dashpot-related dissipation. The thermal dissipation ratio exhibits staged variation with impact velocity, whereas G h shows a non-monotonic trend and reaches its minimum at 6 m/s. Under the present model conditions, an impact velocity of about 6 m/s provides a relatively favorable balance between energy dissipation and crack development.