Abstract
In related research, femtosecond laser-induced periodic surface structures (FLIPSSs) have been well developed to achieve grooved structures with submicron spacing (700nm) and amplitude (200nm). FLIPSSs can be formed on various kinds of materials using linearly polarized femtosecond laser pulses with low fluence that is slightly above the ablation threshold. FLIPSSs with submicron scale periodical pitch and groove depth generate extremely high load carrying capacity under submicron clearance sliding conditions However, when start-up or rest of sliding, FLIPSSs have possibilities to increase damage of counterpart surface such as wear because of little load carrying capacity. In this study, in order to decrease damage of counterpart surface, FLIPSSs were offset from the polished sliding surface, and the effect of offset depth for load carrying capacity was evaluated by both numerical analysis and ring-on-disk test using PAO4 (18.82Cp @ 37°C) as lubricant. As a result, it was confirmed that intermittent spiral FLIPSSs pattern can ease up damage of counterpart surface, although inhibit decrease of load carrying capacity.
