Effects of grain refinement and strength on friction and damage evolution under repeated sliding contact in nanostructured metals

Short note on improved integration of mechanical testing in predictive wear models

“…In general higher wear rate was associated with increasing friction, and a transition to lower wear rate more steady friction. Studies of the relative importance of yield stress and microstructure on the evolution of friction and wear of metallic materials during micro-scale repetitive low-pass sliding have concluded that yield stress plays the dominant role on the evolution of friction as the friction was almost independent of the grain size but decreased with increasing hardness [35][36][37]. Non-constant rate of sliding wear has been observed in repetitive micro-scratch testing of bulk metallic samples such as Cu where the large plastic strains associated with sliding contact can produce a surface hardening effect [36] or surface softening [37].…”

Fracture toughness and fatigue crack growth characteristics of nanotwinned copper

“…In high cycle fatigue, this trend is reflected as a higher fatigue endurance limit (which is elevated with higher strength); the endurance limit is typically measured through cyclic-stress-controlled experiments on initially smooth laboratory specimens [7]. When the average grain size is refined to values typically below 100 nm, the resulting nanostructured metals exhibit significantly elevated strength and strain rate sensitivity and much lower activation volume, as well as improved resistance to corrosion, fatigue crack initiation for long life as seen in the fatigue endurance limit, and monotonic and cyclic wear [8][9][10][11][12][13] in comparison to microcrystalline metals and alloys [3,5,6]. However, such beneficial effects of grain size reduction are also commonly accompanied by reductions in ductility.…”

Nano-indentation mapping of fretting-induced surface layers

“…Small-scale fretting on Ti alloys and on copper was investigated by T. Hanlon and A. Singh at MIT [24,25]. The authors performed nano-indentation tests at the base of the sliding tracks to assess local gradients in mechanical properties.…”