A comprehensive study of the abrasive effects of lunar regolith is essential for mitigating damage to mechanical components during lunar missions. This research focuses on preparing lunar mare (LX-M100) and highland (LX-TH100) simulants with different particle size fractions to develop a tribological model for further investigation of their frictional properties. Fine and coarse simulants were separated using a digital electromagnetic sieve shaker, yielding five particle size fractions for each type. The sieving process revealed discrepancies between actual particle sizes and supplier data, highlighting the need for uniform particle size to ensure consistent wear testing. Simulants with uniform particle sizes produced more reliable and controlled wear patterns, especially in tribological experiments involving rotating shafts and seals. To replicate lunar conditions, future experiments will employ a custom-built pin-on-disc tribo-test rig and sand-pot test rig to evaluate the wear performance of a stainless-steel shaft and polytetrafluoroethylene (PTFE) seal. This study advances understanding of the abrasive impact of lunar dust, contributing to the development of more durable materials for future lunar exploration.

This study investigates the abrasive effects of Lunar Highland regolith simulant (TH100) and the particle size effect on stainless steel/PTFE rotary shaft–lip seal assemblies. A custom-built sand-pot testing rig filled with Nitrogen gas was used to expose EN-1.4404 stainless steel shafts paired with spring-loaded natural PTFE seals to fine (≤0.125 mm) and coarse (1.400–2.000 mm) Lunar Highland regolith particles. Each rotating pair was operated for 0.25, 0.5, and 24 hours at sequential shaft positions. Wear progression was assessed through shaft surface roughness measurements and scanning electron microscopy of the seals before and after testing. All tests under fine particles were completed without failure, whereas the sealing system exposed to coarse particles failed during the final shaft position and test was stopped. Fine particles primarily induced micro-cutting on the shaft surface, while coarse particles produced a combination of micro-cutting and micro-ploughing. These findings reveal the pronounced influence of particle size on wear mechanisms in lunar dust-exposed rotary sealing systems, with implications for the durability of moving components in extraterrestrial environments.

Despite extensive research on the abrasive properties of lunar regolith, the use of in-process tribological signals for wear assessment remains insufficiently studied. The aim of this work is to evaluate the relationship between torque response and abrasive wear severity in rotating shaft–seal systems exposed to lunar regolith simulants. Rotating EN 1.4404 stainless-steel shafts and spring-loaded natural polytetrafluoroethylene (PTFE) lip seals were tested under three-body abrasive wear conditions. Five particle-size fractions of LX-M100 Lunar Mare and LX-TH100 simulants were investigated at test durations of 15 min, 30 min and 1440 min. Frictional torque was continuously recorded, while post-test shaft surface roughness was used to characterize wear severity and Scanning Electron Microscope (SEM) analysis of the PTFE counterface was used to identify wear mechanisms. The results showed that torque response systematically depended on particle-size fraction and simulant type. Furthermore, the torque-response descriptors provide in-process information related to abrasive interaction severity, with peak torque events ($T_{max}$) showing the strongest relationship with abrasive surface modification. The statistical analysis was based on 27 complete observations, and considering the prematurely terminated test runs and the resulting limitations of the dataset, the obtained relationships are interpreted as exploratory. These findings provide a physical basis for torque-based wear monitoring in sealed rotating mechanisms for future lunar applications.